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| United States Patent |
6,348,986
|
|
Doucet
, et al.
|
February 19, 2002
|
Wireless fiber-coupled telecommunication systems based on atmospheric
transmission of laser signals
Abstract
A wireless optical transceiver system which includes a passive optical
antenna coupled by optical fiber to an active electronics module. The
transceiver system receives and transmits light beams from/to the
atmosphere,.and thereby communicates optically with a second optical
transceiver. Receivers, transmitters, repeaters, switches, routers, etc.,
may be similarly organized, i.e. by coupling one or more passive optical
antennas and an active electronics module with fiber-optic cable.
Furthermore, various network toplogies and organizations may be arranged
using one or more of the fiber-coupled transceivers, receivers,
transmitters, repeaters, switches, routers, etc. Such components are
admirably suited for use in various network configurations such as
broadcast networks, point-to-multipoint networks, etc due to their low
cost, ease of installation and antenna sighting, modularity, and
upgradability. An optical router for establishing wireless channels to a
number of subscribers may be configured based on demodulation and
remodulation of light beams, or alternatively by redirecting light beams
by adjustable deflections mirrors. A communications network infrastructure
based on atmospheric light beam propagation is contemplated.
| Inventors:
|
Doucet; Mark A. (Bryan, TX);
Panak; David L. (Bryan, TX)
|
| Assignee:
|
Dominion Lasercom. Inc. (Bryan, TX)
|
| Appl. No.:
|
106826 |
| Filed:
|
June 29, 1998 |
| Current U.S. Class: |
398/128; 398/129; 398/141 |
| Intern'l Class: |
H04B 010/00 |
| Field of Search: |
359/152,145,173,172
379/56.1,56.2
|
References Cited [Referenced By]
U.S. Patent Documents
| 4090067 | May., 1978 | Bell, III et al. | 250/199.
|
| 4358858 | Nov., 1982 | Tamura et al. | 359/152.
|
| 4727600 | Feb., 1988 | Avakian | 359/172.
|
| 4796301 | Jan., 1989 | Uzawa et al. | 359/172.
|
| 5247381 | Sep., 1993 | Olmstead et al. | 359/172.
|
| 5455672 | Oct., 1995 | Lamonde et al. | 356/73.
|
| 5493436 | Feb., 1996 | Karasawa et al. | 359/145.
|
| 5818619 | Oct., 1998 | Medved et al. | 359/172.
|
| 5983068 | Nov., 1999 | Tomich et al. | 359/118.
|
| 6091528 | Jul., 2000 | Kanda | 359/159.
|
| 6239888 | May., 2001 | Willebrand | 359/118.
|
| Foreign Patent Documents |
| 1018326 | Jan., 1989 | JP.
| |
Other References
Sladek, "Vier-Strahl-Technik Macht Uebertragung Sicherer," Nachrichten
Elektronik und Telematik, vol. 50, No. 8, Aug. 1996, pp. 32-33.
Kube, "Renaissance Eines Alten Konzepts," Nachrichten Elektronik und
Telematik, vol. 49, No. 5, May 1995, pp. 15, 16, and 18.
International Search Report, Application No. PCT/US99/14710, mailed Mar. 8,
2000.
AstroTerra Corp, "Additional Services," website:
http://www.photon.com/matsueda/Ast.../Additional%20Services/addserv.htm,
1996, 2 pages.
AstroTerra Corp, "Product Information, TerraLink 1000.TM.Series," website:
http://www.photon.com/matsueda/Ast...a/Product%20Info/T_1000/t_10000.htm,
1996, 2 pages.
AstroTerra Corp, "Product FAQ, Frequently Asked Questions," website:
http://www.photon.com/matsueda/AstroTerra/FAQ/faq.htm, 1996, 5 pages.
|
Primary Examiner: Negash; Kinfe-Michael
Attorney, Agent or Firm: Conley, Rose & Tayon PC, Hood; Jeffrey C., Brightwell; Mark K.
Parent Case Text
CONTINUATION DATA
This application is a continuation-in-part of U.S. patent application Ser.
No. 08/625,725 entitled "Point-to-Multipoint Wide Area Telecommunications
Network via Atmospheric Laser Transmission Through a Remote Optical
Router", filed on Mar. 29, 1996 now U.S. Pat. No. 5,786,923, invented by
Mark A. :Woucet and David L. Panak, and assigned to Dominion
Communications, LLC.
Claims
What is claimed is:
1. A system for light-based wireless communication through the atmosphere,
comprising:
an optical fiber;
a passive optical antenna coupled to the optical fiber, wherein the passive
optical antenna is configured (a) to decouple a first light beam from the
optical fiber and transmit the first light beam into the atmosphere, and
(b) to receive a second light beam from the atmosphere and couple the
second light beam onto the optical fiber;
a transceiver unit coupled to the optical fiber, wherein the transceiver
unit includes:
a transmitter for generating the first light beam and modulating a first
data signal onto the first light beam;
a receiver for demodulating a second data signal from the second light
beam;
a coupling interface for coupling the modulated first light beam onto the
optical fiber, and for decoupling the second light beam from the optical
fiber and providing the second light beam to the receiver;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to receive the first data signal from the
communication bus and provide the first data signal to the transmitter,
and further configured to receive the second data signal from the receiver
and transmit the second data signal onto the communication bus.
2. A system for wireless light-based transmission of information,
comprising:
an optical fiber;
a passive optical antenna coupled to the optical fiber, wherein the passive
optical antenna is configured to decouple a first light beam from the
optical fiber and transmit the first light beam into the atmosphere;
a transmitter unit coupled to the optical fiber, wherein the transmitter
unit includes:
a transmitter subsystem for generating the first light beam and modulating
a first data signal onto the first light beam;
a coupling unit for coupling the modulated first light beam onto the
optical fiber;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to receive the first data signal from the
communication bus and provide the first data signal to the transmitter.
3. A system for receiving atmospheric light-beam transmissions, comprising:
an optical fiber;
a passive optical antenna coupled to the optical fiber, wherein the passive
optical antenna is configured to receive a first light beam from the
atmosphere and couple the first light beam onto the optical fiber;
a receiver unit coupled to the optical fiber, wherein the receiver unit
includes:
a receiver subsystem for demodulating a first data signal from the first
light beam;
a coupling interface for decoupling the first light beam from the optical
fiber and providing the first light beam to the receiver subsystem;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to receive the first data signal from the
receiver subsystem and transmit the first data signal onto the
communication-bus.
4. A system for wireless light-based communication through the atmosphere,
comprising:
a first optical fiber and a second optical fiber;
a first passive optical antenna coupled to the first optical fiber, wherein
the first passive optical antenna is configured to decouple a first light
beam from the first optical fiber and transmit the first light beam into
the atmosphere;
a second passive optical antenna coupled to the second optical fiber,
wherein the second passive optical antenna is configured to receive a
second light beam from the atmosphere and couple the second light beam
onto the second optical fiber;
a transceiver unit coupled to the first optical fiber and the second
optical fiber, wherein the transceiver unit includes:
a transmitter for generating the first light beam and modulating a first
data signal onto the first light beam;
a receiver for demodulating a second data signal from the second light
beam;
a fiber coupler for coupling the modulated first light beam supplied by the
transmitter onto the first optical fiber;
a fiber decoupler for decoupling the second light beam from the second
optical fiber and providing the second light beam to the receiver;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to receive the first data signal from the
communication bus and provide the first data signal to the transmitter,
and further configured to receive the second data signal from the receiver
and transmit the second data signal onto the communication bus.
5. A system for receiving light-beam transmissions from the atmosphere,
comprising:
a plurality of optical fibers;
a corresponding plurality of passive optical antennas, wherein each of the
passive optical antennas is coupled to a corresponding one of the optical
fibers, wherein each of the passive optical antennas receives a portion of
a first light beam from the atmosphere and couples the received portion of
the first light onto the corresponding optical fiber;
an active electronics unit which includes:
a fiber coupling unit coupled to the plurality of optical fibers, and
configured to combine the multiple portions of the first light beam
provided by the plurality of optical fibers;
a receiver coupled to receive the combined portions of the first light beam
from the fiber coupling unit and configured to demodulate a first data
signal from the combined portions of the first light beam;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to receive the first data signal from the
receiver and transmit the second data signal onto the communication bus.
6. A network for wireless information broadcast based on light-beam
transmission, comprising:
a transmission system which transmits a first light beam into the
atmosphere, wherein the first light beam carries via modulation a first
data signal;
a plurality of receivers, wherein each of the receivers includes:
an optical fiber;
a passive optical antenna coupled to the optical fiber, wherein the passive
optical antenna is configured to receive a portion of the first light beam
and couple said portion of the first light beam onto the optical fiber;
an active electronics unit which includes:
a receiver for demodulating the first data signal from said portion of the
first light beam;
a fiber decoupler for decoupling said portion of the first light beam from
the optical fiber and providing said portion of the first light beam to
the receiver;
wherein said active electronics unit is configured to provide the first
data signal to a corresponding digital device.
7. The network of claim 6, wherein the transmission system comprises:
a transmit optical fiber;
a transmit optical antenna coupled to the transmit optical fiber;
a transmitter unit coupled to the transmit optical fiber and configured to
modulate the first data signal onto the first light beam and to couple the
modulated first light beam onto the transmit optical fiber;
wherein the transmit optical antenna is configured to decouple the first
light beam from the transmit optical fiber and transmit the first light
beam into the atmosphere.
8. The network of claim 7, wherein the transmitter unit is situated at a
first location internal to a first building, wherein the transmit optical
antenna is situated at a second location external to the first building.
9. The network of claim 6, wherein a first passive optical antenna
corresponding to a first of said receivers is situated at a third location
external to a second building, wherein a first active electronics unit
corresponding to the first receiver is situated at a fourth location
internal to the second building.
10. A system for light-beam transmission of multiple independent data
streams to multiple destinations, comprising:
a laser for generating a first laser beam;
an active electronics unit configured to receive the first laser beam,
wherein the active electronics unit includes:
a beam spitting device for splitting the first laser beam into a plurality
of beam components;
a plurality of modulators for modulating a corresponding plurality of data
signals on the plurality of beam components, wherein each of the
modulators modulates a corresponding one of the data signals on a
corresponding one of the beam components;
a coupling device for coupling the modulated beam components onto a
corresponding plurality of optical fibers, wherein each of the modulated
beam components is coupled onto a corresponding one of the optical fibers;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to receive a data stream from the
communication bus, and further configured to supply the corresponding data
signals to the plurality of modulators;
a plurality of passive optical antennas, wherein each of the passive
optical antennas is coupled to a corresponding one of the optical fibers,
wherein each of the passive optical antennas decouples the modulated beam
component from the corresponding optical fiber, and transmits the
modulated beam component into the atmosphere.
11. A system for wireless light-beam transmission of information to
multiple destinations, comprising:
a laser for generating a first laser beam;
a plurality of optical fibers;
an active electronics unit coupled to the plurality of optical fibers and
configured to receive the first laser beam, wherein the active electronics
unit includes:
a modulator for modulating a first data signal onto the first laser beam;
a power splitting unit for splitting the modulated first laser beam into a
plurality of beam components;
a fiber coupler for coupling each of the beam components onto a
corresponding one of the optical fibers;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to receive the first data signal from the
communication bus and supply the first data signal to the modulator;
a plurality of optical antenna, wherein each of the optical antennas is
coupled to a corresponding one of the optical fibers, wherein each of the
optical antennas is configured decouple a corresponding beam component
from the corresponding optical fiber and transmit the corresponding beam
component into the atmosphere.
12. A switching system for establishing wireless inter-connectivty for a
number of subscribers based on the atmospheric transmission of light
beams, comprising:
a plurality of optical fibers;
a corresponding plurality of passive optical antennas, wherein each of the
passive optical antennas is coupled to a corresponding one of the optical
fibers, wherein each of the passive optical antennas is configured (a) to
receive a first light beam from the atmosphere and couple the first light
beam onto the corresponding optical fiber, and (b) to decouple a second
light beam from the corresponding optical fiber and transmit the second
light beam into the atmophere;
a plurality of transceivers, wherein each of the transceivers is coupled to
a corresponding one of the optical fibers, wherein each of the
transceivers is configured (a) to receive the first light beam from the
corresponding optical fiber, (b) to demodulate a first data signal from
the first light beam, (c) to generate the second light beam, (d) to
modulate a second data signal onto the second light beam, and (e) to
couple the second light beam onto the corresponding optical fiber;
an electronic switching system for exchanging data signal between the
transceivers, wherein the electronic switching system is configured to
transmit the second data signal generated by a first transceiver to a
second transceiver, and further configured to transmit the second data
signal generated by the second transciever to the first transceiver.
13. A method for providing an optical communication capacity to a building,
the method comprising:
mounting a passive optical antenna at a first location external to the
building;
situating an active electronics unit at a second location internal to the
building, wherein said second location is equipped with a power outlet;
coupling the active electronics unit to the power outlet;
coupling the passive optical antenna at the first location and the active
electronics unit at the second location with an optical fiber;
coupling a digital device to the active electronics unit through a
communication bus;
the passive optical antenna receiving a light beam containing digital data
from the atmosphere and coupling the light beam onto the optical fiber;
the optical fiber transferring the light beam between the passive optical
antenna and the active electronics unit;
transferring said digital data between the active electronics module and
the digital device through the communication bus.
14. The method of claim 13, wherein the passive optical antenna is mounted
at a first location external to a building.
15. The method of claim 14, wherein the transceiver unit is situated at a
second location internal to the building.
16. A method for providing an optical communication capacity to a building,
the method comprising:
mounting a passive optical antenna at a first location external to the
building;
situating an active electronics unit at a second location internal to the
building, wherein said second location is equipped with a power outlet;
coupling the active electronics unit to the power outlet;
coupling the passive optical antenna at the first location and the active
electronics unit at the second location with an optical fiber;
coupling a digital device to the active electronics unit through a
communication bus;
transferring digital data between the digital device and the active
electronics module through the communication bus;
the optical fiber transferring a light beam containing the digital data
between the active electronics unit and the passive optical antenna;
the passive optical antenna transferring the light beam between the optical
fiber and the atmosphere.
17. The method of claim 16, wherein the passive optical antenna is mounted
at a first location external to a building.
18. The method of claim 17, wherein the transceiver unit is situated at a
second location internal to the building.
19. A system for light-based communication comprising:
one or more optical fibers;
one or more passive optical antennas each coupled to a corresponding one of
the optical fibers;
a transmitter subsystem for modulating one or more data signals onto one or
more light beams;
a coupling unit for coupling the one or more modulated light beams onto the
one or more optical fibers;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to redeive the one or more data signals from
the communication bus and provide the one or more data signals to the
transmitter subsystem;
wherein the one or more passive optical antennas are configured to decouple
the one or more modulated light beams from the one or moree optical
antennas and transmit the one or more modulated light beams into the
atmosphere.
20. The system of claim 19, wherein the transmitter subsystem, coupling
unit and data interface are contained in a single package, wherein the
single package is situated at a first location internal to a first
building, wherein the one or more passive optical antennas are situated at
one or more second locations external to the first building.
21. The system of claim 19, wherein the transmitter subsystem, coupling
unit and data interface are contained in a single package, wherein the
single package is configured for coupling to a host computer through the
communication bus.
22. A system for light-based communication comprising:
one or more optical fibers;
one or more passive optical antennas for receiving one or more light beams
from the atmosphere, wherein each of the one or more passive optical
antennas is coupled to a corresponding one of the optical fibers;
a receiver subsystem;
a coupling interface for decoupling the one or more light beams from the
one or more optical fibers and providing the one or more light beams to
the receiver subsystem, wherein the receiver subsystem is configured to
demodulate one or more data signals from the one or more light beams;
a data interface configured to couple to a communication bus, wherein the
data interface is configured to receive the one or more data signals from
the receiver subsystem and transmit the one or more data signals onto the
communication bus.
23. The system of claim 22, wherein the receiver subsystem, coupling
interface and data interface are contained in a single package, wherein
the single package is situated at a first location internal to a first
building, wherein the one or more passive optical antennas are situated at
one or more second locations external to the first building.
24. The system of claim 22, wherein the receiver subsystem, coupling
interface and data interface are contained in a single package, wherein
the single package is configured for coupling to a host computer through
the communication bus.
Description
FIELD OF THE INVENTION
The present invention relates generally to wireless telecommunications
networks, and more particularly to a broadband telecommunication system
and network which employs atmospheric (i.e. free-space) laser
transmission.
DESCRIPTION OF THE RELATED ART
In the modern telecommunications market, there exists a vast array of
products and services targeted for the needs and desires of consumers at
every level. Many of these products and services necessitate a network
infrastructure. For example, telephone service is mediated by the Public
Switched Telephone Network (PSTN), also known as the Plain Old Telephone
System (POTS).
Any-to-any connectivity is a fundamental organizing principle of the PSTN,
i.e. any telephone subscriber should be able to call and communicate with
any other telephone subscriber. The switching systems employed in the PSTN
are almost completely digital. Fiber optic cables, copper cables,
microwave links, and satellite links are used for data transmission.
Transmission over the local loop is typically carried by copper-based T1
feeder or fiber optic cable. However the subscriber loop is still
primarily implemented with copper UTP (unshielded twisted pair). Thus, the
transmission bandwidth deliverable to a telephone subscriber is severely
limited, typically less than 56,600 bits per second. At present, the PSTN
bears the triple burden of conveying voice, fax, and data communications,
and is nearly saturated in certain large metropolitan regions.
The Integrated Services Digital Network (ISDN) represents a step upward in
speed relative to the PSTN. First time subscribers to ISDN service
generally incur a cost for installation of an ISDN line which comprises
upgraded copper wire. Computer users who access a corporate Intranet or
the Internet through an ISDN line and ISDN modem experience increased
performance relative to connecting through the PSTN.
A variety of communication applications such as interactive television,
video telephony, video conferencing, video messaging, video on demand,
high definition television (HDTV) and high-speed data services require
broadband data transmission. In fact, many communication applications may
require bandwidths high enough to exclude ISDN as a feasible medium for
establishing a data connection.
Optical fiber offers significantly higher data transmission bandwidths than
copper wire/media. However, fiber optic networks such as fiber to the curb
(FTTC) and fiber to the home (FTTH) require new fiber optic cable to be
run to every subscriber. Thus, the cost of implementing a fiber optic
network may be exorbitant. Other alternatives for increasing the capacity
of existing networks include Asymmetric Digital Subscriber Line (ADSL),
Symmetric Digital Subscriber Line (SDSL), and Hybrid Fiber Coax (HFC),
among others.
In general, all hard-wired networks are burdened with the requirement of
laying cable to new subscribers/nodes. Furthermore, it is difficult to
reconfigure the topology of an existing hard-wired network since cables
are quite often buried underground, suspended from poles, or stung through
the interstitial spaces of office buildings.
In contrast, wireless networks based on the radiation of electromagnetic
energy through free space (i.e. the atmosphere) are able to service
subscribers without incurring costs for laying cable to the subscribers.
Many wireless telecommunication systems are organized as broadcast systems
where a single transmitter sends an information signal to multiple
receivers. For example, the Direct Broadcast Satellite (DBS) systems such
as PrimeStar, Digital Satellite Service, etc. provide satellite broadcast
of video channels to subscribers equipped with a receiving antenna
(typically a dish antenna) and a set-top decoder. Wireless
telecommunication systems and networks are widespread and numerous. Their
numbers continues to increase in response to consumer demand. Thus, the
radio spectrum is increasingly crowded resulting in degraded signal
quality and/or increased subscriber costs.
In certain circumstances and for various reasons, a client/customer may
desire point-to-point communication, i.e. the transmission of information
between two points separated by a distance. For example, a microwave link
between two central offices in the PSTN may be a point-to-point
connection. Laser technology provides an admirable alternative to radio
transmission for establishing broadband point-to-point communication due
to the fact that lasers inherently generate narrowly focussed beams.
Laser-based wireless systems have been developed for establishing
point-to-point, bi-directional and high speed communication through the
atmosphere. The range for such systems is typically 0.5 to 1.2 miles, with
some systems achieving a range of 4 miles or more. The longest atmospheric
communication path achieved with a point-to-point system exceeded 100
miles.
These point-to-point systems require a laser-based communication unit at
each end of the point-to-point connection. A laser-based communication
unit includes an optics package, a laser transmitter, an optical receiver,
and a data interface package. The laser transmitter includes a laser for
generating a laser beam, and modulating electronics for impressing a first
information signal onto the laser beam. Quite often, the first information
signal is a digital signal and ON/OFF keying is employed as the modulation
scheme. The modulated laser beam is transmitted into the atmosphere by the
optics package. Thus, the optics package is sometimes referred to as an
optical antenna. The optics package also receives a second laser signal
from the atmosphere, and provides the second laser signal to the optical
receiver. The optical receiver includes photo-detection and demodulation
electronics for recovering a second information signal from the second
laser signal.
The data interface package is coupled to the laser transmitter, the optical
receiver and to a communication bus. The data interface package is
configured to send and receive data on the communication bus according to
a pre-defined communication protocol. The data interface receives the
first information signal from the communication bus and transmits the
first information signal to the laser transmitter for modulation. The data
interface also receives the second information signal from the optical
receiver and transmits the second information signal onto the
communication bus. Typically, a computer of some sort generates the first
information signal and receives the second information signal. Thus, the
computer generally requires a separate interface card/package in order to
send/receive signals over the communication bus. For example, the
communication bus may be the well-known Ethernet bus. In this case, the
data interface in the laser-based communication unit is Ethernet
compatible as is the interface card/package coupled to the computer.
In prior art laser-based point-to-point systems, the subsystems of the
laser-based communication unit, i.e. the optics package, the laser
transmiitter, the optical receiver, and the data interface package, are
physically integrated into a common chassis. As will become apparent in
the following discussion, the binding of all the sub-systems into a
commnon chassis effects the design complexity of the communication unit
and the installation procedures for the communication unit both of which
impact the effective cost to the consumer.
In order to establish a point-to-point connection, two laser-based
communication units must be configured so that their respective optical
antennas achieve a line of sight (LOS) through the atmosphere. This
generally requires that the units be installed at an elevated outdoor
location such as a rooftop. Since, the communication unit includes active
electronics, the user/client generally incurs a significant cost for
providing a power connection to the installation site. This cost severely
impacts the marketability of existing laser-based systems to home users
and small business users.
The communication unit, being situated out of doors, may be exposed to a
wide variation of temperature and weather conditions. Thus, the
communication unit may require heating and/or cooling devices in order to
protect the electronic subsystems. Furthermore, the chassis must generally
be weatherproof. For example, the chassis should be designed to withstand
rain, wind, and perhaps hail disturbances. Humidity from the ambient air
may corrode internal metallic parts. These weather related constraints add
to the overall cost of prior art laser-based communication units.
Laser-based communication units are massive and voluminous because of the
colocation of transceiver electronics, data interface, and antenna optics
in a common chassis. Care must be exercised to securely mount the chassis
onto a supporting substrate. For example, the chassis often includes a
base plate with holes which admit mounting screws. The cost of designing
the chassis and its mounting structures contributes to overall cost of the
communication unit.
After the communication unit has been mounted, an installer/user must
adjust the angular orientation of the unit to achieve an optical line of
sight (LOS) to a remote communication unit. The optical antenna of the
local unit must be pointed at the optical antenna of the remote unit, and
vice versa. This adjustment generally requires coordination between two
installation personnel, one located at each site. In order to facilitate
the LOS adjustment process, communication units typically include an
external sighting scope. An installer/user looks through the sighting
scope to determine the current direction of the optical antenna. The
sighting scope is typically bore-sighted (i.e. calibrated) at the
manufacturing facility. The installer/user adjusts the orientation of the
communication unit until the remote antenna is centered in the cross-hairs
of the sighting scope.
Since the bore-sighting (calibration) of the sighting scope may be
comprised by physical disturbances to the sighting scope and/or
communication unit, the laser beam transmitted by the optical antenna may
not intercept the remote optical antenna when the unit is adjusted only on
the basis of the sighting scope. The installer/user may have to execute a
search procedure to achieve beam contact with the remote optical antenna.
In other words, the installer/user may have to randomly adjust the
orientation of the local unit while obtaining feedback from the person at
the remote unit to determine when LOS has been achieved. The additional
time required to conduct the random search in case of an insufficiently
bore-sighted sighting scope significantly adds to the cost of
installation.
Although a sighting scope may be bore sighted initially, e.g. in the
factory or by trained personnel at a field site, the bore sighting (i.e.
calibration) may be compromised over the passage of time. For example,
thermal stresses and weathering (rain, hail, wind, etc.) may contribute to
loss of bore sighting accuracy. Thus, the cost of bore sighting may be
incurred more than once through the lifetime of the laser-based
communication unit.
On occasion, the installer/user may desire to replace or upgrade one or
more of the electronic subsystems of the communication unit. Since the
electronic and optical sub-systems of the communication unit are combined
in a common housing, the process of the accessing the electronic
components/subsystems generally implies a physical disturbance of the
optical antenna and the line of sight to the remote optical antenna. For
example, replacement or upgrade of the data interface board may require
the removal of an access panel. The pressures exerted in removing the
access panel and exchanging boards may disturb the LOS of the
communication unit. In some situations, the communication unit must be
dismounted and transported to a repair facility for testing and repair.
Thus, the investment in achieving LOS to the remote optical antenna may be
lost when accessing electronics for maintenance, repair, and/or upgrade.
After accessing the electronics in the communication unit, the
communication unit must generally be re-sighted at additional cost to the
user/client. As with the initial sighting, the re-sighting generally
requires two personnel: one situated at the local site to perform angular
adjustments, and another situated at the remote site to confirm when LOS
has been achieved. Thus, modification to the electronics of one
communication unit generally requires two personnel to coordinate the LOS
adjustment. This greatly increases the effective cost of repairing or
modifying the electronics of the communication unit.
Laser-based systems are capable of maintaining a high-bandwidth
point-to-point connection in some of the most severe inclement weather
conditions. However, the cost of such systems is typically in the $10,000
to $20,000 dollar range, making them unsuitable for most home and business
use.
Therefore, a need exists for a laser-based communication system which may
be mounted more simply and efficiently than in prior art systems.
Furthermore, a laser-based communication system which allows for accurate
and efficient attainment of LOS to a remote unit is desired. Any method
for circumventing the necessity of re-sighting the communication system
upon repair or upgrade of electronics is greatly to be desired. Any method
for simplifying user access to the electronic subsystems of the
laser-based communication system is desirable. In general, a considerable
need exists for a laser-based communication system which realizes
significant cost reductions with respect to prior art systems.
Furthermore, in view of the problems associated with wired networks and
radio-transmission based networks, a wireless laser-based
telecommunication system is desired which provides a number of subscribers
with high-bandwidth telecommunication services. In particular, a wireless
laser-based telecommunication system is desired that enables a number of
subscribers to communicate with a great number of subscribers. A wireless
laser-based telecommunications system is further desired which reduces the
cost to each subscriber, yet maintains high-speed, bi-directional,
broadband, wide area telecommunications. A system is desired which does
not require the huge installation costs of ISDN and fiber optics, and
which does not require any of the electromagnetic broadcast bands in the
radio spectrum. Such a network could be employed in a wide variety of
applications such as telephony, data communications such as the Internet,
teleconferencing, radio broadcast, and various television applications
such as cable television, HDTV and interactive TV.
SUMMARY OF THE INVENTION
The present invention comprises a wireless optical transceiver system which
includes a passive optical antenna coupled by optical fiber to an active
electronics module. The transceiver system receives and transmits light
beams from/to the atmosphere, and thereby communicates optically with a
second optical transceiver. The fiber-optic isolation between an active
electronics module and passive optical antenna has a host of implications
which reduce the initial system cost and ongoing maintenance costs to the
user. In particular, the passive optical antenna, free from the
encumbering influence of active system components, may be installed more
easily and efficiently. Line of sight to a target antenna may be achieved
by disconnecting the optical fiber and visually observing through the
optical path of the passive antenna. Furthermore, the isolation implies
that a power connection is not longer required at the site of the optical
antenna. This results in significant saving to the user/client.
In addition to an optical transceiver system, the present invention also
contemplates receivers, transmitters, repeaters, switches, routers, etc.
configured according to the principle of fiber-optic isolation between a
passive optical antennas and active electronics modules. Such components
are admirably suited for use in various network configurations such as
broadcast networks, point-to-multipoint networks, etc due to their low
cost, ease of installation and antenna sighting, modularity, and
upgradability.
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the present invention can be obtained when the
following detailed description of the preferred embodiment is considered
in conjunction with the following drawings, in which:
FIG. 1 illustrates a full-duplex transceiver system according to the
present invention in communication with a second transceiver system;
FIG. 2 illustrates the transceiver electronics module of the full-duplex
transceiver system of FIG. 1 according to the present invention;
FIG. 3A illustrates an optical transmission system according to the present
invention;
FIG. 3B illustrates an optical receiver system according to the present
invention;
FIG. 4 illustrates a dual-simplex optical transceiver system according to
the present invention;
FIG. 5 illustrates the transceiver electronics module of the dual-simplex
transceiver system of FIG. 4 according to the present invention;
FIG. 6A illustrate an optical receiver system with an antenna array to
increase receiver signal power according to the present invention;
FIG. 6B illustrates a representative distribution of optical receive
antennas in the cross section of the received beam according to the
present invention;
FIG. 6C illustrates the receiver electronics module of the optical receiver
system of FIG. 6A according to the present invention;
FIG. 7 illustrates a branched-fiber embodiment for the receiver system of
FIG. 6A according to the present invention;
FIG. 8 illustrates use of an optical transmitter and multiple receiver
systems to implement a broadcast network according to the present
invention;
FIG. 9 illustrates an optical repeater system according to the present
invention;
FIG. 10 illustrates a transmitter system with multiple inline modulators
and multiple passive optical antennas for transmission of multiple
independent data streams according to the present invention;
FIG. 11 illustrates a broadcast transmission system with an inline power
splitter for transmitting an information signal to a plurality of
receivers;
FIG. 12 illustrates optical switching system for establishing wireless
communication channels among a plurality of subscribers according to the
present invention;
FIG. 13 illustrates the active electronics module of the optical switching
system of FIG. 12 according to the present invention;
FIG. 14 illustrates a point-to-multipoint wide-area telecommunications
network using atmospheric laser transmission according to the present
invention;
FIG. 15 illustrates the overlapping coverage achieved by the incorporation
of multiple optical routers in the network of FIG. 14;
FIG. 16 illustrates a point-to-multipoint wide area telecommunications
network using atmospheric laser transmission according to an alternate
embodiment of the present invention;
FIG. 17 illustrates the preferred embodiment of the optical router in the
network of FIG. 14;
FIG. 18 is a plan view of one of the transceiver modules of FIG. 17;
FIG. 19 is a block diagram of the optical router of FIG. 17, including a
detailed block diagram of the secondary transceiver unit;
FIG. 20 illustrates the optical router in the network of FIG. 16;
FIG. 21 illustrates the primary transceiver unit of FIGS. 14 and 16;
FIG. 22 illustrates a subscriber transceiver unit of FIGS. 14 and 16; and
FIG. 23 is a block diagram of a portion of an alternate embodiment of the
subscriber transceiver unit of FIG. 22.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
Incorporation by Reference
For general information on broadband telecommunications and optical data
communications, please see Lee, Kang and Lee, Broadband Telecommunications
Technology, Artech House, 1993 which is hereby incorporated by reference
in its entirety. Also please see Davis, Carome, Weik, Ezekiel, and Einzig,
Fiber Optic Sensor Technology Handbook, Optical Technologies Incorporated,
1982, 1986, Herndon, Va., which is hereby incorporated by reference in its
entirety.
Full-Duplex Transceiver System
Referring now to FIGS. 1, a fall-duplex transceiver system 10 for
light-based wireless communication through the atmosphere is presented.
Transceiver 10 includes transceiver electronics module 100 and passive
optical antenna 130. The transceiver electronics module 100 is coupled to
passive optical antenna 130 through optical fiber 120. Since the optical
antenna 130 includes only passive components, no power connection is
necessary at the location of optical antenna 130. The user of transceiver
system 10 thereby avoids the cost of installing power at site of the
optical antenna 130. Since optical antennas are generally situated at
elevated outdoor locations such as rooftops, this cost savings is
typically significant.
Since passive optical antenna 130 is coupled to the transceiver electronics
module 100 by optical fiber, the transceiver electronics module may be
separated from the passive optical antenna 130 by a significant distance.
Transceiver electronics module 130 may thereby easily be situated near an
existing power outlet. Typically, this implies that the transceiver
electronics module will be located indoors. Thus, the transceiver
electronics module 100 will not generally require protection from
weathering and extreme temperature variation. Cost reductions connected
with these simplifications may be passed to the consumer.
Furthermore, the fiber optical coupling between the transceiver electronics
module and the passive optical antenna implies that the former may be
modified or upgraded without disturbance to the passive optical antenna.
To upgrade the transceiver electronics module, the user may disconnect the
optical fiber, exchange the transceiver electronics module 100 with an
upgraded version, and reconnect the optical fiber to the new module. The
fiber optic coupling implies that the passive optical antenna will
experience no physical disturbance due to the upgrade. Similar remarks may
be made in situations where the transceiver electronics module 100 is
subjected to repair or maintenance. Thus, the initial investment in
achieving a line of sight between passive optical antenna 130 and optical
antenna 230 may be advantageously preserved.
Since the active optical and electronic components are separated from the
passive optical antenna, both subsystems (i.e. the transceiver electronics
module and the passive optical antenna) are simplified and may be more
compactly arranged. Increased modularization leads to decreased
manufacturing costs.
Passive optical antenna 130 decouples a first light beam from optical fiber
120 and transmits the first light beam into the atmosphere. Transmitted
light beam 140 propagates through space to optical transceiver 20. In one
embodiment shown in FIG. 1, optical transceiver 20 is similar to
transceiver system 10, thus enabling bi-directional point-to-point
communication between the two transceiver systems. Thus, optical
transceiver 20 includes passive optical antenna 230 coupled to transceiver
electronics module 200 through optical fiber 220.
In addition to beam transmission, optical antenna 130 receives a second
light beam 150 from the atmosphere and couples the second light beam onto
optical fiber 120. The second light beam is transmitted by optical
transceiver 20.
Referring now to FIG. 2, a block diagram of transceiver electronics module
100 is shown. Transceiver electronics module 100 includes transmitter 310,
fiber coupling interface 320, signal interface 330, and receiver 340. It
is noted FIG. 2 indicates a pattern of interconnectivity and not
necessarily the spatial layout or physical dimensions of the depicted
subsystems. Transmitter 310 generates the first light beam and modulates
the first light beam according to a first information signal. Thus,
transmitter 310 includes a light source such as a semiconductor laser. In
one embodiment of transmitter 310, the first light beam is modulated after
it is emitted from the light source. In a second embodiment, modulation is
performed by controlling the voltage or current supplied to the light
source. Transmitter 310 receives the first information signal from signal
interface 330. After modulation, first light beam 315 is supplied to fiber
coupling interface 320. The fiber coupling interface 320 couples the first
light beam onto optical fiber 120. Fiber coupling interface 320 preferably
includes a connector to facilitation the connection of optical fiber 120.
Fiber coupling interface 320 also decouples the second light beam from
optical fiber 120, and supplies the decoupled second light beam 325 to
receiver 340. Receiver 340 demodulates the second light beam to recover a
second information signal. The second information signal is supplied to
signal interface 330. Receiver 340 includes a photodetection circuit to
detect the second light beam and convert the second light beam into an
analog electrical signal. In addition, receiver 340 preferably includes
demodulation circuitry for recovering the second information signal from
the analog electrical signal.
Signal interface 330 is configured to couple to a communication bus 350.
Signal interface 330 receives the first information signal from
communication bus 350 and transmits the first information signal to
transmitter 310. In addition, signal interface 330 receives the second
information signal from receiver 340 and transmits the second information
signal onto communication bus 350.
In the preferred embodiment of transceiver electronics module 100, signal
interface 330 is a digital data interface and communication bus 350 is a
digital data bus. Thus, when referring to this embodiment, signal
interface 330 will hereinafter be referred to as data interface 330, and
communication bus 350 will be referred to as data bus 350. Data interface
330 is preferably configured for Ethernet compatibility, in which case
data bus 350 is an Ethernet-compatible bus. However, it is noted that any
type of data interconnection bus may be used to realize data bus 350.
In one embodiment of transceiver electronics module 100, transceiver
electronics module 100 is configured as a PC card (or board) for insertion
into a computer slot. In this case data interface 330 is configured for
exchanging data according to the protocol prevailing on the system bus of
the host computer into which it is to be inserted. The host computer
provides the first information signal (i.e. a first data stream) to the
transceivers electronics module and likewise receives the second
information signal (i.e. a second data stream) through its system bus.
Thus, the host computer advantageously avoids the need for a specialized
communication interface such as an Ethernet card for communicating with
the transmission system 10.
Recall that prior art optical transceivers are generally integrated with
the antenna optics. Thus, prior art transceivers are typically located
remotely. To facilitate data exchange with a computer or digital
device(s), prior art transceivers typically include a bus interface such
as an Ethernet interface. In order to communication with such a prior art
transceiver, a computer would typically require a second bus interface
compatible with the bus interface of the transceiver. The PC card
embodiment of transceiver electronics module 100 advantageously simplifies
the communication path to the host computer. The host computer may
communicate with the optical transceiver 10 without employing an external
communication bus. Transceiver electronics module 100 may be configured to
support any of a variety of telecommunication applications such a
real-time video, Internet access, etc. Thus, high-bandwidth full-duplex
wireless communication may be provided to a computer user at significantly
reduced cost.
Transceiver 10 supports full-duplex communication with optical transceiver
20 mediated by atmospheric transmission of the first and second light
beams. In the preferred embodiment of transceiver system 10, the first
light beam and the second light beam have distinct wavelengths, and fiber
coupling interface includes a wavelength separation device such as a
dichroic mirror for separating the transmit and receive paths. Transmitter
310 continuously generates and modulates the first light beam, while
receiver 340 continuously detects and demodulates the second light beam.
Similarly, passive optical antenna 130 continuously transmits the first
light beam 140 into the atmosphere, and continuously receives the second
light beam 150 from the atmosphere. In this embodiment employing distinct
transmit and receive wavelengths, transceiver system 10 and optical
transceiver 20 are complementary. Namely, the transmit wavelength of
transceiver system 10 is equal to the receive wavelength of optical
transceiver 20, and the receive wavelength of transceiver system 10 is
equal to the transmit wavelength of optical transceiver 20.
In another embodiment of transceiver system 10 and optical transceiver 20,
the first light beam and second light beam have different polarization,
and polarization serves as the means for separating the transmit and
receive paths in the fiber coupling interface 320.
Passive optical antenna 130 is aligned on a line of sight (LOS) with
optical antenna 230 of optical transceiver 20. Passive optical antenna 130
preferably uses a single-lens system to couple the light beams into and
out of optical fiber 120. Since the passive optical antenna is isolated
from active electronics by a fiber coupling, the passive optical antenna
may be configured as a light and compact package which contributes to the
ease of installation and in particular to the ease of achieving LOS to the
optical antenna 230. Furthermore, since the optical fiber may be easily
disconnected from the passive optical antenna 130, a user/installer may
position his/her eye directly in the light transmission path of passive
optical antenna 130. Thus, the user/installer may advantageously performs
angular adjustments while physically viewing through the true optical path
of passive optical antenna 130. When the target, i.e. optical antenna 230
is visually centered in the fiber aperture, a line of sight is achieved.
This ability to directly view the optical path of optical antenna 130
eliminates the need for a separate sighting scope, and the attendant need
for bore sighting (i.e. calibrating) the sighting scope. Thus, the cost of
the transceiver system 10 may be advantageously reduced. Once the line of
sight to the target antenna has been achieved, the optical fiber 120 may
be reconnected to passive optical antenna 130, and system operation may
commence. Since LOS is achieved with less complexity and more reliably,
the cost of installation is significantly reduced.
Furthermore, since modifications to transceiver electronics module 100 do
not disturb passive optical antenna 130, the installation/alignment
process may be performed less frequently as compared to prior art systems
which co-located electronics and antenna optics. Thus, the user of
transceiver system 100 may experience lower on-going costs to maintain the
communication link with optical transceiver 20.
The isolation of active components and passive optical antenna into
separate modules allows the user-client to independently choose the
electronics module and the passive optics module. Each may occur in a
variety of models and configurations to suit various user requirements.
Since the optical fiber is low loss medium, a significant distance may
prevail between the passive optical antenna and transceiver electronics
unit without significant loss of signal power. The transceiver electronics
unit may therefore be situated at any location convenient to the
user-client and with access to a power connection. For example, the
transceiver electronics module 100 may occur as a stand alone package. The
stand alone package may couple to an existing network infrastructure such
as the ISDN, PSTN, or the Internet.
The passive optical antenna 130 is lighter and more compact than in prior
art systems since it is separated from active components. Thus, it is
easier to achieve a secure mounting of the passive optical antenna. In
practice, smaller mounting screws may be used to fix the optical antenna
to a substrate/foundation.
The isolation between transceiver electronics modules and passive antennas
allows a system administrator is reconfigure the connectivity between
multiple transceiver modules and multiple antennas. The isolation
principle leads to increased system flexibility and maintainability.
Hereafter, a number of embodiment of receiver, transmitter, transceivers,
repeaters, switches, routers, etc. are presented. In every case, the
principle of fiber optic isolated between a compact and light passive
optical antenna, and an active optoelectronic module may be employed to
capitalize on the advantages described in connection with optical
transceiver system 10.
Half-Duplex Transceiver System
It is noted that a half-duplex transceiver system (not depicted) may be
configured similar to full-duplex transceiver 10 according to the
principle of separating active electronics subsystems from the passive
optical antenna by a fiber optic coupling. The half-duplex system partakes
of the same advantages as the full-duplex transceiver system with regard
to ease of installation and line of sight targeting, efficiency of
manufacture and upgrade, and reduction of initial and ongoing support
costs.
Optical Transmitter
Referring now to FIG. 3A, a transmitter system 40 for wireless transmission
of information based on light-beam propagation through the atmosphere is
presented. Transmission system 40 includes transmitter electronics module
400 and passive optical antenna 460 coupled via optical fiber 420.
Transmission electronics module 400 includes signal interface 410,
transmitter 420, and fiber coupling interface 430. Signal interface 410 is
configured to couple to communication bus 440. Signal interface 410
preferably includes a specialized connector for coupling to communication
bus 440. Signal interface 410 receive a first information signal from
communication bus 440 and transmits the first information signal to
transmitter 420. Transmitter 420 generates a first light beam and
modulates the first light beam according to the first information signal.
Thus, transmitter 420 includes a light source such as a laser diode.
Transmitter 420 supplies the modulated first light beam to fiber coupling
interface 430. Fiber coupling interface 430 couples the first light beam
onto optical fiber 420. Passive optical antenna 430 decouples the first
light beam from optical fiber 420 and transmits the first light beam into
the atmosphere.
The communication bus 440 couples to a communication device (not shown)
which serves as a source for the first information signal.
Passive optical antenna 460 is aligned to transmit the first light beam to
one or more optical receivers (not shown).
Optical Receiver System
Referring now to FIG. 3B, a receiving system 40 for receiving light-beam
transmissions is depicted. The receiving system 40 includes a receiver
electronics module 500 and passive optical antenna 560 coupled via optical
fiber 520. Passive optical antenna 560 receives a first light beam from
the atmosphere, and couples the first light beam onto optical fiber 520.
Optical fiber 520 provides the first light beam to receiver electronics
module 500.
Receiver electronics module 500 includes signal interface 510, receiver
520, and fiber coupling interface 530. Fiber coupling interface 530
decouples the first light beam from optical fiber 520, and provides the
first light beam to receiver 520. Receiver 520 demodulates the first light
beam to recover a first information signal which is carried on the first
light beam. Thus, receiver 520 includes photodetection circuitry to
convert the first light beam into an electrical signal. Receiver 520
further includes demodulation circuitry to demodulate the first
information signal from the electrical signal. The first information
signal is supplied to signal interface 510.
Signal interface 510 is configured to coupled to communication bus 540.
Signal interface 510 receives the first information signal from receiver
520 and transmits the first information signal onto communication bus 540.
Communication bus 540 couples to a communication device which serves as a
sink for the first information signal.
Dual Simplex Transceiver System
Referring now to FIG. 4, a dual-simplex transceiver system 600 is shown.
Dual-simplex transceiver system 600 includes transceiver electronics
module 610, passive transmit optical antenna 616, passive receive optical
antenna 618. Transmit optical antenna 616 is coupled to transceiver
electronics module 610 through optical fiber 612. Receive optical antenna
618 is coupled to transceiver electronics module 610 through optical fiber
614.
Transmit optical antenna 616 decouples a first light beam from optical
fiber 612 and transmits the first light beam into the atmosphere. The
first light beam 640 propagates through space to optical transceiver
system 700. In the embodiment shown in FIG. 4, optical transceiver system
700 is similar to dual-simplex transceiver system 600. Thus, optical
transceiver system 700 includes transceiver electronics module 710,
passive receive optical antenna 716, and passive transmit optical antenna
718. Receive optical antenna 716 is coupled to transceiver electronics
module 710 through optical fiber 712. Transmit optical antenna 718 is
coupled to transceiver electronics module 710 through optical fiber 714.
Referring now to FIG. 5, a block diagram of transceiver electronics module
600 is shown. Transceiver electronics module 600 includes signal interface
810, transmitter 820, receiver 830, fiber coupler 840 and fiber coupler
850. Signal interface 810 is con-figured to couple to a communication bus
860. Signal interface 810 receives a first information signal from
communication bus 860, and provides the first information signal to
transmitter 820. Transmitter 820 generates the first light beam and
modulates the first light beam according to the first information signal.
Transmitter 820 provides the modulated first light beam to the fiber
coupler 840. Fiber coupler 840 couples the first light beam onto optical
fiber 612. The first light beam propagates the length of optical fiber 612
and is transmitted into space by transmit optical antenna 616.
Fiber coupler 850 decouples the second light beam from optical fiber 614,
and provides the second light beam to receiver 830. Receiver 830 detects
and demodulates the second light beam, and thereby recovers a second
information signal. The second information signal is provided to signal
interface 810. Signal interface 810 transmits the second information
signal onto communication bus 860.
Transmit optical antenna 616 and receive optical antenna 716 are aligned to
achieve an optical line of sight (LOS). Thus, the first light beam
effectively illuminates receiver optical antenna 716. Also, transmit
optical antenna 718 and receiver optical antenna 618 are aligned to
achieve a line of sight. Thus, the second light beam effectively
illuminates the receiver optical antenna 618.
In one embodiment, dual-simplex transceiver system 600 is configured for
communication compatibility with full-duplex transceiver system 10 of FIG.
1. Thus, the wavelength of the first light beam generated by the
dual-simplex transceiver system 600 is equal to the receive wavelength of
the full-duplex transceiver system 10. Also, the dual-simplex transceiver
system 600 is configured to receive the second light beam at a wavelength
equal to the transmit wavelength of full-duplex transceiver 10. In this
embodiment, both antennas of the dual-simplex transceiver system 600 are
aligned to achieve a line of sight to passive optical antenna 130 of
full-duplex transceiver 10.
Receiver System with Antenna Array for Increasing Received Signal Power
Referring now to FIG. 6A, a receiver system 1000 with an antenna array is
shown. Receiver system 1000 includes receiver electronics module 1010 and
an antenna array which comprises a plurality of passive optical antennas
1060A through 1060N. Passive optical antennas 1060 are coupled to receiver
electronics module 1010 through a corresponding plurality of optical
fibers 1050A through 1050N. In other words, passive optical antenna 1060A
is coupled to receiver electronics module 1010 through optical fiber
1050A, . . . , and passive optical antenna 1060N is coupled to receiver
electronics module 1010 through optical fiber 1050N.
Receiver system 1000 operates in conjunction with optical transmitter 900.
Optical transmitter 900 transmits a first light beam 950 to passive
optical antennas 1060. Thus, each of the passive optical antennas 1060
achieves a line of sight with the optical antenna 960 of optical
transmitter 900. It is assumed that the first light beam has a
cross-sectional area large enough to intersect more than one of passive
optical antennas 1060. Each of passive optical antennas 1060 receives a
portion of the first light beam, and couples its received portion onto a
corresponding one of optical fibers 1050. The passive optical antennas
1060 are advantageously distributed so as to cover the cross-sectional
area of the first light beam (see FIG. 6B). For example, the passive
antennas 1060 may be distributed in a hexagonal, rectangular, or
pseudo-random pattern to cover the first light beam cross-section.
Referring now to FIG. 6C, a block diagram of receiver electronics unit 1010
is shown. Receiver electronics unit 1010 includes signal interface 1012,
receiver 1015, and fiber coupling interface 1020. Fiber coupling interface
1020 is configured to couple to each of the optical fibers 1050. Fiber
coupling interface 1020 decouples the portions of the first light beam
from the optical fibers 1050, and combines these beam portions into a
single composite beam. The single composite beam 1018 is supplied to a
photodetector (not shown) in receiver 1015. Receiver 1015 demodulates the
composite beam 1018 and thereby recovers an information signal which is
supplied to signal interface 1012. Signal interface 1010 supplies the
information signal to communication bus 1025.
The receiver system 1000 of FIG. 6A demonstrates the principle of adding
multiple optical antennas in order to increase the amount of light
collected and supplied to the photodetector.
Referring now to FIG. 7, an alternate embodiment 1000B of receiver system
1000 is depicted. In the alternate embodiment 1000B, the plurality of
optical fibers 1050 are replaced by a one-to-N branched optical fiber
1052, wherein N is the number of passive optical antennas 1060. The N
branches couple to the optical antennas 1060, while the single opposite
end couples to receiver electronics module 1010B. The one-to-N branched
fiber 1052 physically combines the beam portions which propagate through
the N branches into a single fiber. In this embodiment, fiber coupling
interface 1020B couples to the single unified end of branched fiber 1052,
and decouples the combined beam from the branched fiber 1052, and supplies
the combined beam to the receiver 1015.
In an embodiment similar to the embodiment of FIG. 8, the one-to-N branched
fiber is replaced by a network of one-to-two, one-to-three, or one-to-K
branched fibers, where K is an integer smaller than N. For example, a
one-to-four branching may be realized by three one-to-two branched fibers.
By employing the principles described above, full-duplex transceiver system
10 may be configured with an antenna array similar to antenna array
similar to the antenna array 1060 of FIG. 6A or FIG. 8. Furthermore,
dual-simplex transceiver system 600 may also be configured with an antenna
array wherein one or more of the antennas of the array are dedicated for
transmission, and remaining antennas of the array are dedicated for
reception.
A Broadcast Network Embodiment
Referring now to FIG. 8, one embodiment of a broadcast network according to
the present invention is depicted. An optical transmitter 1100 transmits a
broadcast beam BCB to multiple optical receiver systems 50-1 through 50-N
similar to receiver system 50 of FIG. 3B. The multiple optical receiver
systems 50-1 through 50-N have their passive optical antennas 560-1
through 560-N aimed at the transmission antenna 1160. Optical transmitter
1100 embeds an information signal onto the broadcast beam BCB. In the
embodiment shown in FIG. 8, optical transmitter 1100 is similar to
transmission system 40. Each of the passive optical antennas 560-1 through
560-N intercept a portion of the broadcast beam BCB. Thus, the passive
optical antennas 560-1 through 560-N are in relatively close proximity to
one another. However, the fiber optic connections 520-1 through 520-N
allow the receiver electronics modules 500-1 through 500-N to be located
at widely disparate locations according to convenience to the respective
users.
Each of the receiver systems 50-1 through 50-N demodulate the common
information signal from the intercepted portion of the broadcast beam.
Optical Repeater System
Referring now to FIG. 9, an optical repeater system 1200 is shown according
to the principles of the present invention. Optical repeater 1200 includes
a passive receive optical antenna 1210, an active electronics module 1215,
and a passive transmit optical antenna 1220. The passive receive antenna
1210 is coupled to the active electronics module 1215 through a first
optical fiber 1212. The passive transmit antenna is coupled to the active
electronics module through a second optical fiber 1217.
The receive antenna 1210 is oriented in a first direction in order to
receive a first light beam B1 from a remote transmitter (not shown).
Receive antenna 1210 couples the first light beam B1 onto the first
optical fiber 1212. The active electronics module 1215 decouples the first
light beam B1 from the first optical fiber B1. Furthermore, active
electronics module 1215 includes circuitry (a) to demodulate an
information signal from the first light beam, (b) to generate and modulate
a second light beam B2 according to the information signal, and (c) to
couple the second light beam B2 onto the second optical fiber 1217.
Transmit optical antenna 1220 decouples the second light beam B2 from the
second optical fiber 1217 and transmits the second light beam B2 to a
remote receiver (not shown). In one embodiment of repeater 1200, the
transmit wavelength equals the receive wavelength. In another embodiment
of repeater 1200, the transmit and receive wavelengths are distinct.
It is noted that a variety of optical repeater embodiments may be realized
by pursuing the principle of fiber optic separation of a passive antennas
and active electronics. In particular, the present invention contemplates
optical repeaters in full-duplex, half-duplex, and dual-simplex
realizations.
Optical repeater 1200 may be advantageously employed in a broadcast network
to extend the effective range of a transmitter, or to get around an
obstacle which occludes a direct line of sight between a transmitter and
one or more receivers.
Multicasting Transmitter with Multiple Inline Modulators
Referring now to FIG. 10, an optical transmission system 1300 for
broadcasting multiple independent data streams to multiple spatially
distributed receivers is presented. Optical transmission system 1300
includes a light source 1380, an active electronics unit 1310, and a
plurality of passive optical transmission antennas 1360-1 through 1360-N.
Optical antennas 1360 are coupled to active electronics module 1310
through a corresponding plurality of optical fibers 1350-1 through 1350-N
as shown in FIG. 10. Light source 1380 is preferably a laser. Light source
1380 generates a first light beam 1381 which is provided to the active
electronics module 1310.
Active electronics module 1310 includes signal interface 1315, beam
splitter 1320, a plurality of beam modulators 1330-1 through 1330-N, and
fiber coupling interface 1340. Beam splitter 1320 splits the first light
beam 1381 generated by light source 1380 into a plurality of beam
components 1325-1 through 1325-N. Each of the beam components 1325-I is
supplied to a corresponding beam modulator 1330-I, where I is a generic
value in the range 1 to N. Beam modulators 1330 receive a corresponding
plurality of information signals from signal interface 1315. Each beam
modulator 1330-I modulates the corresponding beam component 1325-I
according to the corresponding information signal supplied by signal
interface 1315. The modulated beam components 1335-1 through 1335-N are
provided to fiber coupling interface 1340. Fiber coupling interface
includes a plurality of connectors for the plurality of optical fibers
1350-1 through 1350-N. Fiber coupling interface 1340 couples each of the
modulated beam components 1335-1 through 1335-N onto a corresponding one
of the optical fibers 1350.
Each passive optical antenna 1360-I decouples a corresponding beam
component from the optical fiber to which it is coupled, and transmits the
beam component into the atmosphere. Since each of the optical antennas
1360-I may be independently oriented, transmission system 1300 supports
transmission to a plurality of receivers which are geographically
scattered.
Signal interface 1370 is configured to couple to communication bus 1370. In
one embodiment, signal interface 1370 receives a data stream which
contains N independent information signals from communication bus 1370.
Signal interface 1370 separates the information signals, and supplies each
of the information signals to a corresponding one of beam modulators
1330-1 through 1330-N. In other embodiment, communication bus may be an
analog signal bus and/or include multiple independent conductors or
optical fibers.
In summary, optical transmission system 1300 provides for the transmission
of multiple independent information streams to multiple receivers.
It is noted that the optical transmission system 1300 may be easily
modified to realize optical transceiver systems with full-duplex,
half-duplex, and dual-simplex configurations.
In an alternate embodiment of active electronics module 1310, light source
1380 is included in active electronics module 1310.
Broadcast Transmitter with Inline Power Splitter
Referring now to FIG. 11, a broadcast transmission system 1400 for wireless
light-beam transmission of an information signal to multiple
geographically distributed users is presented. Broadcast transmission
system 1400 includes a laser 1480, active electronics module 1405, and a
plurality of passive optical antennas 1460-1 through 1460-N. The optical
antennas 1460 are coupled to active electronics module 1405 through a
corresponding plurality of optical fibers 1450-1 through 1450-N as shown
in FIG. 11. Light source 1480 is preferably a laser.
Active electronics module 1405 includes signal interface 1410, modulator
1420, power splitter 1430, and fiber coupling interface 1440. Light source
1480 generates a first light beam 1481. Modulator 1420 modulates the first
light beam according to an information signal supplied by signal interface
1410. The modulated light beam 1425 is supplied to power splitter 1430
which splits light beam 1425 into a plurality of beam components 1435-1
through 1435-N. Fiber coupling interface 1440 preferably includes a
plurality of connectors for coupling to optical fibers 1450-1 through
1450-N. Fiber coupling interface 1440 couples each of beam components
1435-1 through 1435-N onto a corresponding one of optical fibers 1450-1
through 1450-N. Each of passive optical antennas 1460 decouples a
corresponding beam component from the corresponding optical fiber and
transmit the corresponding beam component into the atmosphere.
Each of the optical antennas 1460 may be oriented in a distinct direction
(azimuth and elevation angle). Thus, transmission system 1400 supports
transmission of an information signal to multiple independent
destinations.
Switching System for Wireless Network Interconnectivity
Referring now to FIG. 12, wireless network 1500 for providing
interconnectivity among a number of users is presented. Wireless network
1500 includes switching system 1505 and a plurality of transceivers 10-1
through 10-L similar to transceiver system 10 of FIG. 1.
Switching system 1505 includes a plurality of passive optical antennas
1560-1 through 1560L, and active electronics module 1510. Passive optical
antennas 1560 are coupled to active electronics module 1510 through a
corresponding plurality of optical fibers 1550-1 through 1550-L as shown
in FIG. 12. Each passive optical antenna 1560-I achieves a line of sight
to optical antenna 130-I of a corresponding transceiver 10-I. The optical
antenna 130-I of transceiver 10-I transmits a first light beam to optical
antenna 1560-I. Optical antenna 1560-I receives the first light beam and
couples the first light beam onto the corresponding optical fiber 1550-I.
Furthermore, optical antenna 1550-I decouples a second light beam from
optical fiber 1550-I, and transmits the second light beam to optical
antenna 130-I through the atmosphere.
Active electronics module 1510 includes a plurality of transceivers 1520-1
through 1520-L coupled to an electronics switching system 1530. Each
transceiver 1520-I is coupled to a corresponding optical fiber 1550-I.
Furthermore, each transceiver 1520-I is configured (a) to receive the
first light beam from the corresponding optical fiber, (b) to demodulate a
first data signal from the first light beam, (c) to generate the second
light beam, (d) to modulate a second data signal onto the second light
beam, and (e) to couple the second light beam onto the corresponding
optical fiber 1550-I.
Electronics switching system 1530 is configured for exchanging data signals
between transceivers 1520-1 through 1520-L. In one embodiment, electronics
switching system 1530 is configured to establish a number of
bi-directional data channels between pairs (or subsets) of transceivers
1520. For each channeled pair (subset) of transceivers, electronics
switching system 1530 exchanges (broadcasts) the second data signal
produced by each transceiver to the other transceiver(s) of the pair
(subset). Each transceiver of the pair uses the second data signal
receiver from the other transceiver as the first data signal for beam
modulation.
A Network with an Optical Router and a Primary Transceiver
Referring now to FIG. 14, a point-to-multipoint wide-area
telecommunications network 3100 using atmospheric light beam or laser
transmission according to the present invention is shown. The network 3100
preferably comprises a primary transceiver unit 3120, an optical router
3110 and a plurality of subscriber transceiver units 3130A-3130N (referred
to collectively as 3130). In an alternate embodiment, the network 3100
comprises only the optical router 3110 and the plurality of subscriber
transceiver units. The present invention provides a broadband
bi-directional communication network with reduced infrastructure costs,
i.e., no cable or fiber is required to be laid in the subscriber loop,
i.e., to the subscribers.
According to the preferred embodiment of network 3100, the subscriber
transceiver units are located at subscriber premises, such as homes or
businesses. The optical router 3110 is located in the vicinity of the
subscriber transceiver units 3130, and the optical router optically
communicates with the subscriber units 3130. The optical router 3110 has
an associated range of accessibility, wherein the optical router 3110 is
capable of communicating with subscriber transceiver units located within
a circular area around the optical router 3110. In the preferred
embodiment of optical router 3110, the range of accessibility is
approximately between 2000 and 4000 feet. It is contemplated, however,
that optical router 3110 may be configured with larger or smaller ranges
of accessibility. Each of the subscriber transceiver units 3130 is
positioned in a line of sight path relative to the optical router 3110.
The optical router 3110 is positioned in a line of sight path relative to
the primary transceiver unit 3120. The optical router 3110 is preferably
mounted on, for example, a pole, building, or other structure
approximately 75 feet above ground level. Preferably the distance between
the primary transceiver unit 3120 and the optical router 3110 is
approximately in the range from one half to ten miles. It is contemplated,
however, that larger or smaller distances may exist between the optical
router 3110 and the primary transceiver unit 3120 of network 3100
The primary transceiver unit 3120 generates a first light beam 3140 and
atmospherically transmits the first light beam 3140 to the optical router
3110. In the preferred embodiment, the term "light beam" is intended to
encompass any of various types of light transmission, including lasers, a
super-fluorescent light source, or other coherent and/or non-coherent
light or optical transmission.
The primary transceiver unit 3120 modulates data on the first light beam
3140 before transmitting the first light beam 3140 to the optical router
3110. Data may be modulated on the first light beam using any of various
techniques, including amplitude and/or frequency modulation techniques, as
is well known in the art.
The optical router 3110 atmospherically receives the first light beam 3140
including the data sent by the primary transceiver unit 3120 and
demodulates the data, then modulates the data on and atmospherically
transmits a second light beam 3845A-3845N (referred to collectively as
3845) to the subscriber transceiver units 3130. The second light beam 3845
contains at least a portion of the data sent by the primary transceiver
unit 120. The subscriber transceiver units 3130 atmospherically receive
the second light beam 3845 and demodulate the data sent by the primary
transceiver unit 3120 from the second light beam 3845. The present
invention distinguishes among different users, i.e., shares the
communication bandwidth, using techniques such as time-division multiple
access (TDMA) or frequency-division multiple access (FDMA). The present
invention may also use code-division multiple access (CDMA) techniques.
The subscriber transceiver units 3130 atmospherically transmit a third
light beam 3855A-3855N (referred to collectively as 3855) to the optical
router 3110. The subscriber transceiver units 3130 modulate data on the
third light beam 3855 and then transmit the third light beam 3855 to the
optical router 3110. The optical router 3110 atmospherically receives the
third light beam 3855 including the data sent by the subscriber
transceiver units 3130 and demodulates the data, then modulates the data
on and atmospherically transmits a fourth light beam 3150 to the primary
transceiver unit 3120. The primary transceiver unit 3120 receives the
fourth light beam 3150 and demodulates the data sent by the subscriber
transceiver units 3130 from the fourth light beam 3150.
The optical router 3110 routes data between the primary transceiver unit
3120 and each of the subscriber transceiver units 3130 thus establishing
channels of communication, that is, subscriber channels, on the light
beams between the primary transceiver unit 3120 and the subscriber
transceiver units 3130. Preferably the optical router 3110 establishes
subscriber channels in a time-multiplexed fashion. During a first
time-period the optical router 3110 establishes a first set of one or more
subscriber channels between the primary transceiver unit 3120 and a first
set of one or more subscriber transceiver units 3130. Next, the optical
router 3110 establishes a second set of subscriber channels between the
primary transceiver unit 3120 and a second set of subscriber transceiver
units 3130 during a second time-period. The optical router 3110 proceeds
in this manner, establishing a two-way or bi-directional subscriber
channel with each of the subscriber transceiver units 3130 in the range of
accessibility of the optical router 3110.
One embodiment of network 3100 contemplates any or all of the first light
beam 3140, second light beam 3845, third light beam 3855, and fourth light
beam 3150, comprising a plurality of different wavelengths, wherein data
is modulated on each wavelength of the light beams, thereby advantageously
increasing the bandwidth of the subscriber channels.
The network of the present invention may support a large number of
subscribers. One embodiment contemplates on the order of 1000 subscriber
transceiver units supported by a single optical router.
In an alternative embodiment of network 3100, primary transceiver unit 3120
receives the first light beam 3140 from another transceiver (not shown)
and optically redirects the first light beam 3140 to optical router 3110.
Conversely, primary transceiver 3120 optically redirects the fourth light
beam 3150 from optical router 3110 to the other transceiver.
In a second alternative embodiment of network 3100, primary transceiver
unit 3120 receives a source light beam from another transceiver (not
shown), and demodulates data from the source light beam which then becomes
the data source for modulating the first light beam. Conversely, primary
transceiver unit 3120 demodulates data sent by the subscriber transceiver
units from the fourth light beam 3150. The demodulated data is modulated
onto a return light beam which is atmospherically transmitted to the other
transceiver.
In a third alternative embodiment of network 3100, optical router 3110
communicates with another transceiver (not shown). Optical router 3110
atmospherically transmits the fourth light beam 3150 to the other
transceiver for demodulation, and receives the first light beam 3140 from
the other transceiver.
Thus, it may be readily observed that the elements recited above form a
wireless point-to-multipoint wide-area telecommunications network. By
establishing subscriber communications channels in a multiplexed manner
using atmospherically transmitted light beams, the present invention
advantageously provides a telecommunications network which has the
potential to be much less expensive than current wired networks which rely
on copper wire and/or optical fiber.
Additionally, the present invention advantageously provides a much less
expensive telecommunications network than a network which employs an array
of point-to-point atmospherically transmitted light beams.
Further, by employing light beams as the communications path, the present
invention advantageously avoids the costs associated with licensing and
purchasing bands in the radio spectrum.
Finally, the present invention advantageously provides a communications
network which consumes much less power than a system which employs an
angularly dispersed light beam.
In the preferred embodiment of network 3100, the primary transceiver unit
3120 communicates control information to the optical router 3110 and
subscriber transceiver units 3130. The control information for the optical
router 3110 contains information about the angular location of the
subscriber transceiver units 3130. The control information also contains
timing information to instruct the optical router 3110 regarding
multiplexing of the light beams and thus establishing the subscriber
communications channels. The control information for the subscriber
transceiver units 3130 contains timing information instructing the
subscriber transceiver units 3130 about when to transmit the third light
beam 3855 to the optical router 3110. The primary transceiver unit 3120
transmits the first light beam 3140 and receives the fourth light beam
3150 cooperatively according to the control information which the primary
transceiver unit 3120 communicates to the optical router 3110 and
subscriber transceiver units 3130.
In the preferred embodiment of network 3100, the primary transceiver unit
3120 includes a master clock and computes timing control information based
upon at least a plurality of the following factors: the data packet size,
the local speed of light, the number of subscribers, the distance between
the primary transceiver unit and the optical router, the distance between
the optical router and the respective subscriber transceiver unit, the
processing time of the subscriber transceiver units, the time associated
with the electronic router (discussed below), and the switching speed of
the X-Y beam deflectors (discussed below).
In the preferred embodiment of network 3100, the first light beam 3140 and
the fourth light beam 3150 are substantially collinear as are the second
light beam 3845 and third light beam 3855. The collinear light beam
embodiment advantageously allows many of the optical components of the
primary transceiver unit, optical router and subscriber transceiver units
to be shared by the light beams. In this embodiment, the first light beam
3140 and the fourth light beam 3150 have different frequencies or
polarities as do the second light beam 3845 and third light beam 3855 to
advantageously avoid cross-talk between the two light beams. In an
alternate embodiment, the first light beam 3140 and fourth light beam 3150
are in close proximity but not collinear as are the second light beam 3845
and third light beam 3855.
Referring now to FIG. 15, a network comprising a plurality of optical
routers is shown. Each optical router has an associated range of
accessibility. In one embodiment of the present invention, the optical
routers are spatially located such that the accessibility ranges of some
of the optical routers overlap. That is, more than one optical router is
able to service a given subscriber. FIG. 15 shows various regions of
coverage and indicates the number of optical routers which may service a
subscriber located in the region.
In one embodiment of network 3100, if a subscriber transceiver unit detects
a loss of reception of the first light beam, the subscriber transceiver
unit searches for another optical router by which to receive service. By
providing overlapping coverage of a given subscriber by multiple optical
routers, the present invention advantageously provides an element of
redundancy and hence more reliable operation.
In FIG. 15, three optical routers are shown. However, the present invention
is not limited in the number of optical routers which may be serviced by a
given primary transceiver unit 3120, nor the number of optical routers
which may service a given subscriber transceiver unit 3130.
In one embodiment of network 3100, the primary transceiver unit 3120
comprises a plurality of light sources to generate a plurality of first
light beams to transmit to a plurality of optical routers. In another
embodiment of network 3100, the primary transceiver unit 3120 comprises a
single light source to generate a single light beam, and the primary
transceiver unit 3120 is configured to split the light beam generated by
the single light source into multiple first light beams which are
transmitted to a plurality of optical routers. In both embodiments the
primary transceiver unit 3120 modulates subscriber data on each first
light beams.
Alternate Embodiments
Referring now to FIG. 16, an alternate embodiment of the network 3100 of
FIG. 14 is shown. The embodiment of FIG. 16 is similar to the embodiment
of FIG. 14, and corresponding elements are numbered identically for
simplicity and clarity. The optical router 3110 of FIG. 16 corresponds to
the alternate embodiment of the optical router 3110 shown in FIG. 20 and
described below. In the alternate embodiment the optical router 3110
redirects the light beam from the primary transceiver unit 3120 to the
subscriber transceiver units 3130 and redirects the light beams from the
subscriber transceiver units 3130 to the primary transceiver unit 3120
rather than demodulating the data and re-modulating it. The optical router
3110 receives the first light beam 3140 and redirects the first light beam
3140 to the subscriber transceiver units 3130. The subscriber transceiver
units 3130 receive the first light beam 3140 and demodulate the data sent
by the primary transceiver unit 3120 from the first light beam 3140. The
present embodiment distinguishes among different users, i.e., shares the
communication bandwidth, using techniques such as time division multiple
access (TDMA) or frequency division multiple access (FDMA). The present
embodiment may also use code division multiple access (CDMA) techniques.
The subscriber transceiver units 3130 atmospherically transmit a second
light beam 3150A-315ON (referred to collectively as 3150) to the optical
router 3110. The subscriber transceiver units 3130 modulate data on the
second light beam 3150 and then transmit the second light beam 3150 to the
optical router 3110. The optical router 3110 receives the second light
beam 3150 and redirects the second light beam 3150 to the primary
transceiver unit 3120. The primary transceiver unit 3120 receives the
second light beam 3150 and demodulates the data sent by the subscriber
transceiver units 3130 from the second light beam 3150. Alternatively, the
optical router 3110 and/or the primary transceiver unit 3120 provide the
second light beam 3150 to another transceiver (not shown) for
demodulation, wherein this other transceiver is in communication with the
primary transceiver unit 3120.
The optical router 3110 redirects the first and second light beams between
the primary transceiver unit 3120 and each of the subscriber transceiver
units 3130 during different time periods, that is, in a time-multiplexed
manner. In other words, the optical router 3110 establishes channels of
communication comprising the light beams between the primary transceiver
unit 3120 and the subscriber transceiver units 3130 in distinct time
slices. Thus, during a first time period the optical router 3110
establishes a first subscriber channel by redirecting the first light beam
3140 from the primary transceiver unit 3120 to a first subscriber
transceiver unit 3130 and redirecting the second light beam 3150 from the
first subscriber transceiver unit 3130 to the primary transceiver unit
3120. Next, the optical router 3110 establishes a second subscriber
channel between the primary transceiver unit 3120 and a second subscriber
transceiver unit 3130 during a second time period. The optical router 3110
proceeds in this manner, establishing a two-way or bi-directional
subscriber channel with each of the subscriber transceiver units 3130 in
the range of accessibility of the optical router 3110.
An alternate embodiment of the network 3100 contemplates an alternate
multiplexing scheme wherein the primary transceiver unit 3120 is
configured to generate and/or transmit a first light beam 3140 which
comprises a plurality of different wavelengths which correspond to the
subscribers. The optical router 3110 receives the first light beam and
provides each of the wavelength portions to the respective subscriber
transceiver units. In this embodiment, the optical router 3110 includes a
grating, such as a diffraction grating, which separates the different
frequency or spectra and provides the different wavelength portions to the
respective subscribers. Additionally, each subscriber transceiver unit is
configured to generate a second light beam of one or more respective
unique wavelengths. The optical router 3110 redirects the respective
wavelength light beams of the first and second light beams between the
primary transceiver unit 3120 and respective subscriber transceiver units
3130, that is, in a frequency-multiplexed manner. Alternately stated, the
optical router 3110 establishes subscriber channels of communication on
the light beams between the primary transceiver unit 3120 and the
subscriber transceiver units 3130 based upon different wavelength portions
of a light beam. Thus, the optical router 3110 establishes a first
subscriber channel by redirecting a first wavelength portion of the first
light beam from the primary transceiver unit 3120 to a first subscriber
transceiver unit 3130 and redirecting the second light beam 3150
comprising the first wavelength from the first subscriber transceiver unit
3130 to the primary transceiver unit 3120. Simultaneously, the optical
router 3110 establishes a second subscriber channel between the primary
transceiver unit 3120 and a second subscriber transceiver unit 3130 using
a second wavelength portion of the first light beam 3140 and a second
light beam 3150 comprising the second wavelength. The optical router 3110
operates in this manner, establishing a subscriber channel with subscriber
transceiver units 3130 in the range of accessibility of the optical router
3110. By employing multiple wavelength light beams and FDMA techniques,
the invention advantageously increases the bandwidth available to the
subscribers.
Another alternate multiplexing embodiment is contemplated in which the
optical router 3110 establishes subscriber communication channels in a
combined time-multiplexed and frequency-multiplexed manner. A subscriber
requiring increased data bandwidth employs a subscriber transceiver unit
configured to receive multiple light beams of differing wavelengths and/or
multiple time-slots, thereby multiplying the bandwidth available to the
subscriber. In another embodiment, the present invention employs code
division multiple access (CDMA) techniques using bipolar codes.
The present invention contemplates an alternate embodiment of the network
3100 comprising unidirectional data transmission, that is, broadcast or
point-to-multipoint data communication only from the primary transceiver
unit 3120 and/or optical router 3110 to the subscriber transceiver units
3130. In this embodiment, the subscriber transceiver units 3130 do not
generate light beams back through the optical router 3110 to the primary
transceiver unit 3120. Other aspects of this alternate embodiment are as
described above in the preferred embodiment of FIG. 14 and the alternate
embodiment of FIG. 16. This alternate embodiment is contemplated as an
advantageous alternative to current implementations of broadcast
television, particularly high definition television, or cable television,
for example. Thus this embodiment may comprise a pure broadcast (one-way)
network. Alternatively, the network 3100 may use a different return path
from the subscriber units 3130 to the primary transceiver unit 3120, such
as an analog modem (POTS) or ISDN.
The present invention further contemplates an alternate embodiment of the
network 3100 in which the primary transceiver unit 3120 essentially
resides in the same location as the optical router 3110. Alternately
stated, the primary transceiver unit 3120 and the optical router 3110 are
essentially combined into a single unit. In this embodiment the light
source of the primary transceiver unit 3120 transmits only a few inches or
feet into the optical router 3110. Various elements of the primary
transceiver unit 3120 and optical router 3110 may be eliminated or
combined in such an embodiment. In this embodiment, fiber optic cable may
be used to transfer the light beam directly to the optical router 3110,
and thus a separate primary transceiver unit 3120 is not needed.
The Optical Router
Referring now to FIG. 17, the preferred embodiment of the optical router
3110 in the network 3100 (of FIG. 14) is shown. The optical router 3110
comprises a secondary transceiver unit 3700 coupled to a plurality of
transceiver modules 3800A-3800M (referred to collectively as 3800) by an
electronic router 3790. The transceiver modules 3800 are coupled to a
circular backplane 3889. The electronic router 3790 is coupled to the
transceiver modules 3800 through the backplane 3889.
Transceiver module 3800A (representative of the transceiver modules 3800)
has a backplane connector 3888 which connects the transceiver module 3800A
to the backplane. The transceiver module 3800A is configured to transmit
the second light beam 3845 to and receive the third light beam 3855 from a
portion of the subscriber transceiver units 3130, namely those subscriber
transceiver units 3130 within a portion of the circular area around the
optical router 3110. The transceiver modules 3800 collectively provide the
optical router 3110 with a 360 degree range of accessibility to the
subscriber transceiver units 3130.
A beam deflector control system 3795 is coupled through the backplane 3889
to the transceiver modules 3800 for controlling the deflection of the
second light beam 3845 and third light beam 3855 by the transceiver
modules 3800. The beam deflector control system 3795 is also coupled to
the electronic router 3790 and receives beam deflector control information
from the primary transceiver unit 3120 through the electronic router 3790.
The electronic router 3790 receives routing control information from the
primary transceiver unit 3120. The routing control information regards the
routing of data sent by the primary transceiver unit 3120 from the
secondary transceiver unit 3700 to the various transceiver modules 3800
for atmospheric transmission to the subscriber transceiver units 3130.
Conversely, the routing control information regards the routing of data
sent by the subscriber transceiver units 3130 from the various transceiver
modules 3800 to the secondary transceiver unit 700 for atmospheric
transmission to the primary transceiver unit 3120.
The secondary transceiver unit 3700 atmospherically receives the first
light beam 3140 including the data sent by the primary transceiver unit
3120 and demodulates the data. The secondary transceiver unit 3700
communicates the data sent by the primary transceiver unit 3120 to the
electronic router 3790. The electronic router 3790 routes the data from
the secondary transceiver unit 3700 to the appropriate one of the
transceiver modules 3800. For illustration purposes let us assume
transceiver module 3800A is the appropriate transceiver module 3800. The
transceiver module 3800A receives the data and modulates the data onto the
second light beam 3845 which is atmospherically transmitted to the
appropriate subscriber transceiver unit 3130A.
Conversely, the transceiver module 3800A receives the third light beam 3855
including data from the subscriber transceiver unit 3130 and demodulates
the data. The transceiver module 3800A communicates the data sent by the
subscriber transceiver unit 3130A to the electronic router 3790. The
electronic router 3790 routes the data from the transceiver module 3800A
to the secondary transceiver unit 3700. The secondary transceiver unit 700
modulates the data sent by the subscriber transceiver unit 3130A onto the
fourth light beam 3150 and atmospherically transmits the fourth light beam
3150 including the data sent by the subscriber transceiver unit 3130A to
the primary transceiver unit 3120.
FIG. 18
Referring now to FIG. 18, a plan view of the transceiver module 3800A of
the optical router 3110 of FIG. 17 is shown. The transceiver module 3800A
comprises a light source 3862 configured to generate the second light beam
3845. A beam modulator 3864 receives data which was sent by the primary
transceiver unit 3120 from the electronic router 3790 through the
backplane connector 3888 and modulates the data onto the second light beam
3845. The second light beam 3845 is deflected by an X-Y beam deflector
3840 to the subscriber transceiver unit 3130A.
Preferably the X-Y beam deflector 3840 is a galvanometer mirror pair.
Galvanometer mirrors are well known, particularly in the art of laser
printer technology and the art of laser light shows. Alternatively the X-Y
beam deflector 3840 is an acousto-optic or solid state beam deflector. The
optical router 3110 light source 3862 preferably comprises one or more
continuous wave or pulsed beam lasers as are well known in the art, such
as gas, solid state or diode lasers. The beam modulator 3864 preferably
comprises an electro-optic cell. Alternatively, the beam modulator 3864 is
a bulk type modulator. The light source and beam modulator configuration
is indicative of those well known in fiber optic communication link
transmission systems. However, the laser power output is typically
significantly greater than those used in fiber optic systems.
While the X-Y beam deflector 3840 deflects the second light beam 3845 to
the subscriber transceiver unit 3130A the X-Y beam deflector 3840
simultaneously deflects the third light beam 3855 from the subscriber
transceiver unit 3130A to a beam splitter 3880. The beam splitter 3880
splits a relatively large portion of the third light beam 3855 to a beam
demodulator 3872 which receives the third light beam 3855 and demodulates
data sent by the subscriber transceiver unit 3130A from the third light
beam 3855. The beam demodulator 3872 communicates the data through the
backplane connector 3888 to the electronic router 3790. The beam
demodulator 3872 preferably comprises a photodiode as is common in the
art.
During a first time period, the X-Y beam deflector 3840 deflects the second
light beam 3845 from the light source 3862 to a first subscriber
transceiver unit 3130A and deflects the third light beam 3855 from the
first subscriber transceiver unit 3130A to the beam demodulator 3872.
Hence, the transceiver module 3800A establishes a bi-directional
communications channel using the second and third light beams between the
transceiver module 3800A and the first subscriber transceiver unit 3130A
for a first period of time. Hence, the bi-directional communications
channel between the transceiver module 3800A and the first subscriber
transceiver unit 3130A comprises a portion of the subscriber channel
described above between the primary transceiver unit 3120 and the
subscriber transceiver unit 3130A. During subsequent periods of time the
X-Y beam deflector 3840 deflects the second and third light beams to and
from other subscriber transceiver units 3130 in a time-multiplexed manner.
Each of the transceiver modules 3800 establishes bi-directional
communication channels as just described between the given transceiver
module and the portion of the subscriber transceiver units 3130 accessible
by the given transceiver module in a time-multiplexed fashion and
simultaneously with the other transceiver modules. In this manner, a
portion of a wireless point-to-multipoint bi-directional wide area
telecommunications network is advantageously formed between the optical
router 3110 and the subscriber transceiver units 3130.
The beam splitter 3880 splits a relatively small portion of the third light
beam 3855 to a beam alignment detector 3852 which receives the split
portion of the third light beam 3855 and detects misalignment or wander of
the third light beam 3855 from the subscriber transceiver unit 3130A which
may occur and stores the beam stabilization information. The beam
alignment detector 3852 communicates the beam stabilization information
through the backplane 888 via the electronic router 3790 to the secondary
transceiver unit 3700. The secondary transceiver unit 3700 transmits the
beam stabilization information to the primary transceiver unit 3120. The
primary transceiver unit 3120 communicates the beam stabilization
information to the given subscriber transceiver unit so that the
subscriber transceiver unit can adjust the beam for misalignment or wander
appropriately. Atmospheric turbulence and density variations along the
atmospheric path between the subscriber transceiver unit 3130A and the
optical router 3110 may account for misalignment of the third light beam
3855 on the X-Y beam deflector 3840 of the transceiver module 3800A.
Likewise, events such as ground shifting or tower sway may cause the
positions of the subscriber transceiver unit 3130A or optical router 3110
relative to each other to change.
FIG. 19
Referring now to FIG. 19, a block diagram of the optical router 3110 of
FIG. 17 is shown including a detailed block diagram of the secondary
transceiver unit 3700. A transceiver module 300A is coupled to the
electronic router 3790 through the backplane 3889. The electronic router
3790 is also coupled to the other transceiver modules 3800 (not shown).
The electronic router 3790 is coupled to the beam deflector control system
3795 and to the secondary transceiver unit 3700.
The secondary transceiver unit 3700 comprises an optical antenna 3210 which
receives the first light beam 3140 from the primary transceiver unit 3120.
The optical antenna 3210 also transmits the fourth light beam 3150 to the
primary transceiver unit 3120. The optical antenna 3210 preferably
comprises an optical system with a conic mirror, which is well known in
the art. Alternatively the optical antenna 3210 is a collecting lens
system which is also well known in the art. The optical antenna 3210 and
associated optics converge and re-collimate the incoming first light beam
3140 to a relatively small diameter, preferably in the range of 1 to 3
millimeters. Conversely, the optical antenna 3210 receives a relatively
small diameter fourth light beam 3150 generated by a light source 3362 and
expands and re-collimates the fourth light beam 3150 for atmospheric
transmission to the primary transceiver unit 3120.
The optical antenna 3210 atmospherically receives the first light beam 3140
including the data sent by the primary transceiver unit 3120 (of FIG. 1)
from the primary transceiver unit 3120 and directs the first light beam
3140 to a beam demodulator 3372. The beam demodulator 3372 demodulates the
data sent by the primary transceiver unit 3120 from the first light beam
3140 and communicates the data to the electronic router 3790. The data
sent by the primary transceiver unit 3120 comprises subscriber data as
well as control data. The control data comprises routing control
information for the electronic router 3790 as well as timing control
information and angular position control information of the subscriber
transceiver units 3130 for the beam deflector control system 3795. The
electronic router 3790 uses the routing control information to route the
subscriber data to the appropriate transceiver modules 3800. The
electronic router 3790 communicates the timing control information and the
angular position control information to the beam deflector control system
3795. The beam demodulator 3372 preferably comprises a photo-diode as is
common in the art.
The light source 3362 generates the fourth light beam 3150. The electronic
router 3790 routes the data sent by the subscriber transceiver units 3130
from the transceiver modules 3800 to a beam modulator 3364. The beam
modulator 3364 modulates the data sent by the subscriber transceiver units
3130 onto the fourth light beam 3150 for transmission to the optical
antenna 3210 and on to the primary transceiver unit 3120.
The light source 3362 preferably comprises one or more continuous wave or
pulsed beam lasers as are well known in the art, such as gas, solid state
or diode lasers. The beam modulator 3364 preferably comprises an
electro-optic cell. Alternatively, the beam modulator 3364 is a bulk type
modulator. The light source and beam modulator configuration is indicative
of those well known in fiber optic communication link transmission
systems. However, the laser power output is typically significantly
greater than those used in fiber optic systems.
As the first light beam 3140 passes from the optical antenna 3210 to the
beam demodulator 3372 the first light beam 3140 is directed toward the
beam demodulator 3372 by a beam separator 3380. Conversely, as the fourth
light beam 3150 passes from the light source 3362 to the optical antenna
3210 the fourth light beam 3150 passes through the beam separator 3380.
The X-Y beam deflector 3840 is coupled through the backplane 3889 to the
beam deflector control system 3795. The beam deflector control system 3795
controls the switching of the X-Y beam deflector 3840 to deflect the
second light beam 3845 and third light beam 3855 to and from the desired
subscriber transceiver unit 3130 at the desired time. Thus in a
time-multiplexed fashion the beam deflector control system controls the
establishing of the portion of the subscriber channels between the
subscriber transceiver units 3130 and the transceiver modules 3800.
Preferably, the beam deflector control system 3795 receives control
information from the primary transceiver unit 3120 to control the X-Y beam
deflector 3840. The control information for the beam deflector control
system 3795 contains information about the angular location of the
subscriber transceiver units 3130. The beam deflector control system 3795
uses the subscriber transceiver unit angular location information to
determine the desired deflection angles of the X-Y beam deflector 3840.
As mentioned in the discussion of FIG. 14, the primary transceiver unit
3120 also preferably transmits multiplexing control information to the
optical router 3110 and to the subscriber transceiver units 3130. The
primary transceiver unit 3120 transmits the control information for one or
more subscriber channels prior to transmitting the subscriber data packets
associated with the one or more subscriber channels. The multiplexing
information is timing information used by the beam deflector control
system 3795 to control the X-Y beam deflector 3840 regarding when to
deflect the second and third light beams to and from a given subscriber
transceiver unit 3130.
The subscriber transceiver unit transmits the third light beam 3855
containing data for the primary transceiver unit 3120 to the optical
router 3110 at a time determined by the primary transceiver unit 3120.
Correspondingly, the transceiver module servicing the subscriber
transceiver unit transmits the second light beam with the data modulated
for the subscriber transceiver unit to arrive at the X-Y beam deflector at
substantially the same time as the third light beam 3855 containing data
from the first subscriber arrives at the optical router 3110. The primary
transceiver unit 3120 transmits the first light beam 3140 containing data
for the subscriber transceiver unit to arrive at the optical router 3110
at a time such that the data may be demodulated, routed, modulated on the
second light beam 3845 and the second light beam 3845 transmitted to
arrive at the X-Y beam deflector 3840 at substantially the same time as
the third light beam 3855 containing data from the first subscriber
arrives at the optical router 3110.
By employing optical components to converge and re-collimate the light
beams as described previously, the internal components of the optical
router 3110, such as the beam deflector, advantageously operate on
relatively narrow light beams. This improves the accuracy of beam
redirection. Conversely, by employing optical components to expand and
re-collimate the light beams as described previously, the light beams
traveling through the atmosphere between network elements are
advantageously relatively wide light beams. This improves the reception
characteristics of the light beams as they are received by the network
components.
The optical router 3110 further comprises an active optics control system
3350, such as are well known, particularly in the defense industry. The
active optics control system 3350 provides stabilization of the first
light beam 3140 on the optical antenna 3210 of the optical router 3110 and
of the fourth light beam 3150 on the optical antenna 3710 (of FIG. 21) of
the primary transceiver unit 3120. As the first light beam 3140 travels
from the optical antenna 3210 toward the beam demodulator 3372, a small
portion of the first light beam 3140 is split by a beam separator 3380 and
redirected to a beam alignment detector 3352. The beam alignment detector
3352 detects misalignment or wander in the first light beam 3140 which may
occur and stores the beam stabilization information. Atmospheric
turbulence and density variations along the atmospheric path between the
primary transceiver unit 3120 and the optical router 3110 may account for
misalignment of the first light beam 3140 on the optical router 3110.
Likewise, events such as ground shifting or tower sway may cause the
positions of the primary transceiver unit 3120 or optical router 3110
relative to each other to change.
The active optics control system 3350 communicates the beam stabilization
information to the electronic router 3790 which in turn communicates the
beam stabilization information to the beam modulator 3364. The beam
modulator 3364 modulates the beam stabilization information data onto the
fourth light beam 3150 during a designated time period for atmospheric
transmission to the primary transceiver unit 3120. The primary transceiver
unit 3120 demodulates the beam stabilization information data from the
fourth light beam 3150 and uses the beam stabilization information to make
corrections and stabilize the first light beam 3140 on the optical router
3110.
Additionally, the active optics control system 3350 uses the beam
misalignment information to control a beam adjuster 3220, positioned
between the optical antenna 3210 and the beam splitter 3230, to adjust the
first light beam 3140 optimally into the beam demodulator 3372.
As previously mentioned the primary transceiver unit 3120 communicates
control information to the optical router 3110. The control information
further comprises beam stabilization information. The active optics
control system 3350 uses the beam stabilization information from the
primary transceiver unit 3120 to control the optical antenna 3210 and beam
adjuster 3220 to make corrections and stabilize the fourth light beam 3150
on the primary transceiver unit 3120.
Preferably the beam separator 3380 is a dichroic mirror. Alternatively, the
first light beam 3140 and fourth light beam 3150 are orthogonally
polarized and the beam separator 3380 is a polarization separator.
In the preferred embodiment of the invention, the optical router 3110
periodically polls the subscriber transceiver units 3130 by allocating a
communication channel to each of the subscriber transceiver units 3130
within the range of accessibility of the optical router 3110. However, the
optical router 3110 may lose reception of the third light beam 3855 from a
given subscriber transceiver unit for a significant period of time. The
most common cause of the reception loss is the subscriber transceiver unit
being powered off. When the optical router 3110 detects reception loss,
the optical router 3110 preferably and advantageously polls the
powered-off subscriber less frequently than subscriber transceiver units
which are actively transmitting a third light beam 3855 to the optical
router 3110.
Alternate Embodiment
Referring now to FIG. 20, an alternate embodiment of the optical router
3110 in the network 3100 (of FIG. 16) is shown. The optical router 3110
comprises an optical antenna 3210 which receives the first light beam 3140
from the primary transceiver unit 3120. The optical antenna 3210 also
transmits the second light beam 3150 received from a subscriber
transceiver unit to the primary transceiver unit 3120. The optical antenna
3210 preferably comprises an optical system with a conic mirror, which is
well known in the art. In an alternate embodiment the optical antenna 3210
is a collecting lens system which is also well known in the art. The
optical antenna 3210 and associated optics converge and re-collimate the
incoming first light beam 3140 to a relatively small diameter, preferably
in the range of 1 to 3 millimeters. Conversely, the optical antenna 3210
receives a relatively small diameter second light beam 3150 received from
internal components of the optical router 3110 and expands and
re-collimates the second light beam 3150 for atmospheric transmission to
the primary transceiver unit 3120.
The optical antenna 3210 receives the first light beam 3140 from the
primary transceiver unit 3120 (of FIG. 16) and directs the first light
beam 3140 to an X-Y beam deflector 3240. The beam deflector 3240 receives
the first light beam 3140 and deflects the first light beam 3140 toward a
mirror 3261. The mirror 3261 reflects the first light beam 3140 to a
respective one or more of the subscriber transceiver units 3130 (of FIG.
16). Conversely, the subscriber transceiver units 3130 transmit respective
second light beams 3150 to the mirror 3261. The mirror 3261 reflects a
received second light beam 3150 to the beam deflector 3240. The beam
deflector 3240 deflects the second light beam 3150 to the optical antenna
3210. The optical antenna 3210 receives the second light beam 3150 and
transmits the second light beam 3150 to the primary transceiver unit 3120.
Preferably, during a first time period, the beam deflector 3240 deflects
the first light beam 3140 from the optical antenna 3210 to a location on
the mirror 3261 and deflects the second light beam 3150 from substantially
the same location on the mirror to the optical antenna 3210. The location
on the mirror 3261 is calculated to reflect the first light beam 3140 to a
particular subscriber transceiver unit and reflect the second light beam
3150 from the particular subscriber transceiver unit. Hence, the optical
router 3110 establishes a bi-directional communications channel using the
first and second light beams between the primary transceiver unit 3120 and
one of the subscriber transceiver units 3130 for a period of time. During
subsequent periods of time the beam deflector 3240 deflects the light
beams to other locations on the mirror 3261 in order to establish channels
with the other subscriber transceiver units 3130 serviced by the optical
router 3110. In this manner, a wireless point-to-multipoint bi-directional
wide area telecommunications network is advantageously formed.
The beam deflector 3240 is controlled by a beam deflector control system
3340 coupled to the beam deflector 3240. The beam deflector control system
3340 controls the beam deflector 3240 to deflect the light beams to the
desired locations on the mirror 3261 during the desired time. Preferably,
the beam deflector control system 3340 receives control information from
the primary transceiver unit 3120 to control the beam deflector 3240. The
control information for the optical router 3110 contains information about
the angular location of the subscriber transceiver units 3130. The beam
deflector control system 3340 uses the subscriber transceiver unit angular
location information to determine the desired locations on the mirror 3261
used for deflection of the light beams.
As mentioned in the discussion of FIG. 16, the primary transceiver unit
3120 also preferably transmits multiplexing control information to the
optical router 3110 and to the subscriber transceiver units 3130. The
primary transceiver unit 3120 transmits the control information for one or
more subscriber channels prior to transmitting the subscriber data packets
associated with the one or more subscriber channels. Preferably, the
multiplexing information is timing information used by the beam deflector
control system 3340 to control the beam deflector 3240 regarding when to
deflect the light beams to and from a particular location on the mirror
3261. A first subscriber transceiver unit 3130 transmits the second light
beam 3150 containing data for the primary transceiver unit 3120 to the
optical router 3110 at a time determined by the primary transceiver unit
3120. Correspondingly, the primary transceiver unit 3120 transmits the
first light beam 3140 containing data for the first subscriber to the
optical router 3110 at a time such that the first light beam 3140
containing data for the first subscriber arrives at the optical router
3110 at substantially the same time the second light beam 3150 containing
data from the first subscriber arrives at the optical router 3110.
Additionally, the beam deflector control system 3340 controls the beam
deflector 3240 to redirect the first and second light beams between the
primary transceiver unit 3120 and first subscriber transceiver unit 3130
during the time when the first and second light beams are passing through
the optical router 3110, as directed by the primary transceiver unit 3120.
Preferably, the X-Y beam deflector 3240 is a galvanometer mirror pair.
Galvanometer mirrors are well known, particularly in the art of laser
printer technology and the art of laser light shows.
One embodiment contemplates the beam deflector 3240 comprising a plurality
of such galvanometer mirror pairs. Each galvanometer mirror pair deflects
a different light beam between the mirror 3261 and the optical antenna
3210. The primary transceiver unit 3120 transmits the first light beam
3140 which is comprised of multiple light beams each of a different
wavelength, i.e., the first light beam 3140 includes a plurality of
different wavelengths. The optical router 3110 splits the first light beam
3140 into respective wavelength portions which are deflected by respective
beam deflectors. Conversely, multiple subscriber transceiver units 3130
transmit second light beams 3150 of differing wavelengths which arrive
simultaneously at the optical router 3110. The optical router 3110
combines the multiple wavelength second light beams 3150 and transmits the
multiple wavelength second light beam 3150 to the primary transceiver unit
3120.
Other embodiments contemplate the beam deflector 3240 comprising one or
more acousto-optic or solid state beam deflectors.
Preferably the mirror 3261 is a conical or hemispherical mirror wherein the
cone axis is in a vertical orientation, thus providing 360 degree access
to subscribers with an elevation aperture covering the access area to a
range of approximately between 2000 and 4000 feet. The mirror 261 is
circumscribed by a lens set 3262. The lens set 3262 preferably comprises a
plurality of relatively small positive lenses arrayed in a conical or
hemispherical fashion. As the relatively small diameter first light beam
3140 reflects from the mirror 3261, the first light beam 3140 expands in
diameter. The lens set 3262 re-collimates the expanding first light beam
3140 back to a slightly converging first light beam 3140 for atmospheric
transmission to the subscriber transceiver units 3130. Conversely, the
lens set 3262 focuses the second light beam 3150 from the subscriber
transceiver units 3130 onto the mirror 3261. An aperture is formed in the
lens set 3262 through which the relatively small diameter first and second
light beams travel between the X-Y beam deflector 3240 and the mirror
3261. The mirror 3261 and lens set 3262 collimate beam 3150 in a manner
optimized for the optical router 3261 access area.
By employing optical components to converge and re-collimate the light
beams as described previously, the internal components of the optical
router 3110, such as the beam deflector, advantageously operate on
relatively narrow light beams. This improves the accuracy of beam
redirection. Conversely, by employing optical components to expand and
re-collimate the light beams as described previously, the light beams
traveling through the atmosphere between network elements are
advantageously relatively wide light beams. This improves the reception
characteristics of the light beams as they are received by the receivers
of the network components.
The optical router 3110 further comprises a receiver 3370 and a beam
separator 3380. Preferably, the optical router 3110 establishes a control
channel between the primary transceiver unit 3120 and the optical router
3110 for use in communicating control information, as previously
discussed, from the primary transceiver unit 3120 to the optical router
3110. The control channel is distinct from the subscriber channels.
Preferably, the beam deflector control system 3340 controls the beam
deflector 3240 to redirect a particular first light beam 3140 to the beam
separator 3380 rather than to the subscriber transceiver units 3130. This
redirection to the beam separator 3380 rather than to the subscriber units
3130 preferably occurs at preset periods of time. The beam separator 3380
redirects the particular first light beam 3140 to the receiver 3370, which
receives the first light beam 3140. The primary transceiver unit 3120
correspondingly modulates the control information data on the first light
beam 3140 to be received and demodulated by the beam demodulator 3372 in
the receiver 3370. The receiver 3370 is coupled to the beam deflector
control system 3340 and communicates the control information data to the
beam deflector control system 3340. The beam demodulator 3372 preferably
comprises a photo-diode as is common in the art.
Preferably, the control channel is established in a time-multiplexed
manner. During a time period, which is distinct from time periods devoted
to subscriber channels, the beam control system 3340 controls the beam
deflector 3240 to deflect the first light beam 3140 to a location on the
mirror 3261 such that the first light beam 3140 is reflected to the beam
separator 3380 rather than to the subscriber transceiver units 3130. The
primary transceiver unit 3120 instructs the optical router 3110 to
establish this control channel prior to the time for the optical router
3110 to establish the control channel. Preferably, during initialization,
the optical router 3110 devotes all communication channels to be control
channels until instructed by the primary transceiver unit 3120 to allocate
subscriber channels.
In an alternate embodiment, the control channel is established in a
frequency-multiplexed manner wherein a light beam of a distinct frequency,
which is distinct from frequencies devoted to subscriber channels, is
devoted to control channels.
The optical router 3110 further comprises an active optics control system
3350, such as are well known, particularly in the defense industry. The
active optics control system 3350 provides stabilization of the first
light beam 3140 on the optical antenna 3210 of the optical router 3110 and
the second light beam 3150 on the optical antenna 3710 (of FIG. 21) of the
primary transceiver unit 3120. As the first light beam 3140 travels from
the optical antenna 3210 to the beam deflector 3240, a small portion of
the first light beam 3140 is split by a beam splitter 3230 and redirected
to a beam alignment detector 3352. The beam alignment detector 3352
detects misalignment or wander in the first light beam 3140 which may
occur and stores the beam stabilization information. Atmospheric
turbulence and density variations along the atmospheric path between the
primary transceiver unit 3120 and the optical 3110 may account for
misalignment of the first light beam 3140 on the optical router 3110.
Likewise, events such as ground shifting or tower sway may cause the
positions of the primary transceiver unit 3120 or optical router 3110
relative to each other to change.
The active optics control system 3350 communicates the beam stabilization
information to the primary transceiver unit 3120 on a control channel. The
primary transceiver unit 3120 uses the beam stabilization information to
make corrections and stabilize the first light beam 3140 on the optical
router 3110.
The optical router 3110 further comprises a transmitter 3360 including a
light source 3362 and a beam modulator 3364. The active optics control
system 3350 provides the beam stabilization information of the first light
beam 3140 to the transmitter 3360. The light source 3362 generates and
atmospherically transmits a control light beam 3250. The beam modulator
3364 modulates the positional information on the control light beam 3250
as it travels through the beam separator 3380 to the mirror 3261. Thus a
control channel is established between the optical router 3110 and the
primary transceiver unit 3120, similar to the control channel described
above in which the primary transceiver unit 3120 transmits control
information to the optical router 3110, but in the opposite direction.
That is, while the beam deflector 3240 is controlled to deflect the first
light beam 3140 to the mirror 3261 such that the mirror 3261 reflects the
first light beam 3140 to the receiver 3370, the beam deflector 3240 also
deflects the control light beam 3250 from the mirror 3261 to the optical
antenna 3210. This provides a two-way or bi-directional control channel.
The optical router 3110 light source 3362 preferably comprises one or more
continuous wave or pulsed beam lasers as are well known in the art, such
as gas, solid state or diode lasers. The beam modulator 3364 preferably
comprises an electro-optic cell. Alternatively, the beam modulator 3364 is
a bulk type modulator. The light source and beam modulator configuration
is indicative of those well known in fiber optic communication link
transmission systems. However, the laser power output is typically
significantly greater than those used in fiber optic systems.
Additionally, the active optics control system 3350 uses the beam
misalignment information to control the beam adjuster 3220 to adjust the
first light beam 3140 optimally into the beam deflector 3240.
As previously mentioned the primary transceiver unit 3120 communicates
control information to the optical router 3110. The control information
further comprises beam stabilization information which the optical router
3110 receives on the control channels. The active optics control system
3350 of the optical router 3110 uses the beam stabilization information
from the primary transceiver unit 3120 to control the optical antenna 3210
and beam adjuster 3220 to make corrections and stabilize the second light
beam 3150 on the primary transceiver unit 3120.
In an alternate embodiment, the optical router active optics control system
3350 further comprises a second beam alignment detector (not shown) which
detects misalignment or wander in the second light beam 3150 from the
subscriber transceiver units 3130 and stores the beam stabilization
information. The optical router 3110 communicates the beam stabilization
information to the primary transceiver unit 3120. The primary transceiver
unit 3120 in turn communicates the beam stabilization information to the
subscriber transceiver units 3130. The active optics control systems in
the subscriber transceiver units 3130, discussed below, use the beam
stabilization information from the primary transceiver unit 3120 to
control the subscriber transceiver unit optical antennas and beam
adjusters to make corrections for misalignment or wander and stabilize the
second light beam 3150 on the optical router 3110.
In one embodiment the beam separator 3380 is a dichroic mirror. In another
embodiment, the first light beam 3140 and second light beam 3150 are
orthogonally polarized and the beam separator 3380 is a polarization
separator.
Preferably, the optical router 3110 periodically polls the subscriber
transceiver units 3130 by allocating a communication channel to each of
the subscriber transceiver units 3130 within the range of accessibility of
the optical router 3110. However, the optical router 3110 may lose
reception of the second light beam 3150 from a given subscriber
transceiver unit for a significant period of time. The most common cause
of the reception loss is the subscriber transceiver unit being powered
off. When the optical router 3110 detects reception loss, the optical
router 3110 preferably and advantageously polls the powered-off subscriber
less frequently than subscriber transceiver units which are actively
transmitting a second light beam 3150 to the optical router 3110.
The Primary Transceiver Unit
Referring now to FIG. 21, the preferred embodiment of the primary
transceiver unit 3120 in the network 3100 (of FIG. 14) is shown. The
primary transceiver unit 3120 comprises an optical antenna 3710 optically
coupled to a transmitter 3750 and a receiver 3770.
The optical antenna 3710 transmits the first light beam 3140 to the optical
router 3110 (of FIG. 14) and receives the fourth light beam 3150 from the
optical router 3110. (It is noted that for the network 3100 where the
alternate embodiment of the optical router 3110 is employed, i.e., the
network of FIG. 16, the optical antenna 3710 receives the second light
beam 3150.) The optical antenna 3710 preferably is similar to the optical
antenna 3210 of the optical router 3110. An optical antenna 3710 of the
primary transceiver unit 3120 is contemplated with different dimensions
and optical characteristics than the optical antenna 3210 of the optical
router 3110.
The optical antenna 3710 of the primary transceiver unit 3120 is preferably
larger than the subscriber transceiver unit optical antenna. Preferably,
the receiver 3770 of the primary transceiver unit 3120 is more sensitive,
i.e., able to demodulate a weaker light beam, than that of the subscriber
transceiver units. Thus the subscriber transceiver unit light source,
discussed below, may be less powerful, thus reducing the cost of the
subscriber transceiver units. In other words, the primary transceiver unit
3120 transmitter light source 3754 is preferably more powerful than the
subscriber transceiver unit light source. This allows the subscriber
transceiver unit antenna, discussed below, to be relatively small and the
subscriber transceiver unit receiver, discussed below, to be relatively
less sensitive. Hence the total cost of the system is reduced since the
number of subscriber transceiver units is typically much greater than the
number of primary transceiver units in the network.
A data source/sink (not shown) provides data to the primary transceiver
unit 3120 to be sent to the subscriber transceiver units 3130. The data
source/sink ties into and/or uses existing communication structures such
as a telephone network, cable television system, the Internet or other
networks employing Asynchronous Transfer Mode (ATM), switched-ethernet,
SONNET, FDDI, Fibre-Channel, Serial Digital Heirarchy, etc. Various means
for coupling the data source/sink to the primary transceiver unit 3120 are
contemplated, such as fiber-optic cable, satellite up-links and
down-links, atmospheric light beams, coaxial cable, microwave links, etc.
The light source 3754 generates and atmos-pherically transmits the first
light beam 3140 upon which the beam modulator 3752 modulates the data to
be sent to the subscriber transceiver units 3130. A beam adjuster 3720,
which preferably comprises an adjustable fine steering mirror, receives
and reflects the first light beam 3140 to a lens assembly 3780 and optical
antenna 3710 which expand, re-collimate and transmit the first light beam
3140 to the optical router 3110.
Conversely, the primary transceiver unit optical antenna 3710
atmospherically receives the fourth light beam 3150 from the optical
router 3110, and the lens assembly 3780 focuses the fourth light beam 3150
onto the beam adjuster 3720. The beam adjuster 3720 reflects the narrowed
fourth light beam 3150 to a beam separator 3740. The beam separator 3740
is similar to that of the optical router 3110. The beam separator 3740
redirects the fourth light beam 3150 to the receiver 3770. The beam
demodulator 3772 receives the fourth light beam 3150 and demodulates the
data sent by the subscriber transceiver units 3130. The data is then
provided to the data source/sink. The beam demodulator 3772 preferably
comprises a photo-diode, as is common in the art.
The primary transceiver unit light source 3754 preferably comprises one or
more continuous wave or pulsed beam lasers as are well known in the art,
such as gas, solid state or diode lasers. The beam modulator 3752
preferably comprises an electro-optic cell. Alternatively, the beam
modulator 3752 is a bulk type modulator. The light source and beam
modulator configuration is similar to those well known in fiber optic
communication link transmission systems. However, the laser power output
is typically significantly greater than those used in fiber optic systems.
The light beam wavelengths generated by the atmospherically transmitting
light sources described in the present invention are chosen to minimize
the power loss through the atmosphere. Preferably the wavelengths are in
the near infrared range.
The lens assembly 3780 and optical antenna 3710 are configured to transmit
the first light beam 3140 having a beam waist which is advantageously
located at the optical router 3110. The diameter of the first light beam
3140 leaving the optical antenna 3710 is many times the diameter of the
first light beam 3140 exiting the light source 3754. Thus the laser power
density is spread over a relatively large, cross-sectional area, which
enhances eye-safety. Additionally, the relatively large diameter of the
light beams traveling between the components of the network improves the
reception characteristics of the light beams at the optical receivers.
The primary transceiver unit 3120 additionally comprises a control system
(not shown) which computes the previously discussed routing, beam
stabilization, timing, subscriber location and multiplexing control
information.
The primary transceiver unit 3120 further comprises an active optics
control system 3760 similar to the active optics control system 3350 of
the optical router 3110. The primary transceiver unit active optics
control system 3760 cooperates with the optical router active optics
control system 3350 to provide stabilization of the first light beam 3140
on the optical antenna 3210 of the optical router 3110 and the fourth
light beam 3150 on the optical antenna 3710 of the primary transceiver
unit 3120.
As previously mentioned, the optical router 3110 communicates beam
stabilization information to the primary transceiver unit 3120. The active
optics control system 3760 uses the beam stabilization information from
the optical router 3110 to control the optical antenna 3710 and beam
adjuster 3720 to make corrections and stabilize the first light beam 3140
on the optical router 3110.
Additionally, the active optics control system 3760 uses the beam
misalignment information detected by the beam alignment detector 3762 to
control the beam adjuster 3720 to adjust the fourth light beam 3150
optimally into the receiver 3770.
The Subscriber Transceiver Units
Referring now to FIG. 22, an illustration of the preferred embodiment of a
subscriber transceiver unit 3130A in the network 3100 (of FIG. 14) is
shown. Subscriber transceiver unit 3130A is representative of the
plurality of subscriber transceiver units 3130. The subscriber transceiver
unit 3130A comprises an optical antenna 3510 coupled to an input/output
device 3600, such as a set-top box 3600, by a fiber optic cable 3590. The
input/output device 3600 may be any of various devices, including a
set-top box, computer system, television, radio, teleconferencing
equipment, telephone or others which may be coupled to the optical antenna
3510 by a fiber optic cable 3590. In the remainder of this disclosure, the
input/output device 3600 is referred to as a set top box. Power and
control wires (not shown) also couple the subscriber optical antenna 3510
and the set-top box 3600.
The optical antenna 3510 receives the second light beam 3845 from the
optical router 3110 (of FIG. 14) and transmits the third light beam 3855
to the optical router 3110. (It is noted that for the network 3100 where
the alternate embodiment of the optical router 3110 is employed, i.e., the
network of FIG. 16, the subscriber transceiver unit 3130A receives the
first light beam 3140 from the optical router 3110 and transmits the
second light beam 3150 to the optical router 3110.) The optical antenna
3510 preferably is similar to the optical antenna 3210 of the optical
router 3110. An optical antenna 3510 of the subscriber transceiver unit
3130A is contemplated with different dimensions and optical
characteristics than the optical antenna 3210 of the optical router 3110.
The optical antenna 3510 receives the second light beam 3845 and focuses
the second light beam 3845 into a fiber-optic coupling 3580. The
fiber-optic coupling 3580 couples the second light beam 3845 into the
fiber optic cable 3590. The fiber optic cable 3590 carries the second
light beam 3845 to the set-top box 3600. A beam separator 3570 in the
set-top box 3600 redirects the second light beam 3845 to a receiver 3550
which receives the second light beam 3845. A beam demodulator 3552 in the
receiver 3550 demodulates the data from the second light beam 3845. The
receiver 3550 provides the data to external connections (not shown) on the
set-top box 3600, which connect to various devices such as televisions,
computers, radios, teleconferencing equipment and telephones (also not
shown). The beam demodulator 3552 preferably comprises a photo-diode as is
common in the art.
Conversely, the various digital devices provide data to be sent to the
primary transceiver unit 3120 (of FIG. 14) to a transmitter 3560 in the
set-top box 3600. The set-top box 3600 comprises a light source 3564 which
generates the third light beam 3855. A beam modulator 3562 in the
transmitter 3560 modulates the data to be sent to the primary transceiver
unit 3120 on the third light beam 3855. The third light beam 3855 passes
through the fiber optic cable 3590 to the fiber-optic coupling 3580. The
fiber optic coupling 3580 decouples the third light beam 3855 from the
fiber optic cable 3590 and atmospherically redirects the third light beam
3855 to the optical antenna 3510. The optical antenna 3510 then transmits
the third light beam 3855 including the data to the optical router 3110.
The subscriber transceiver unit 3130A light source 3564 preferably
comprises one or more continuous wave or pulsed beam lasers as are well
known in the art, such as gas, solid state or diode lasers. The beam
modulator 3562 preferably comprises an electrooptic cell. Alternatively,
the beam modulator 3562 is a bulk type modulator. The light source and
beam modulator configuration is similar to those well known in fiber optic
communication link transmission systems. However, the laser power output
is typically greater than those used in fiber optic systems.
In an alternate embodiment, previously mentioned, the subscriber
transceiver unit 3130A is configured to transmit and receive multiple
wavelength light beams in order to increase the data bandwidth available
to a given subscriber.
The subscriber transceiver unit 3130A further comprises an active optics
control system 3540 similar to the active optics control system of the
optical router 3110 and the primary transceiver unit 3120. The subscriber
transceiver unit active optics control system 3540 cooperates with the
primary transceiver unit 3120 active optics control system to provide
stabilization of the second light beam 3845 on the subscriber transceiver
unit 3130A and the third light beam 3855 on the optical router 3110.
A beam alignment detector 3542 detects misalignment or wander in the second
light beam 3845 from the optical router 3110 and stores the beam
stabilization information. The subscriber transceiver unit 3130A
communicates the beam stabilization information regarding the first light
beam 3150 to the primary transceiver unit 3120 via the transmitter 3560.
The invention contemplates the beam stabilization information being
communicated to the primary transceiver unit 3120 in a header in a
subscriber data packet. The invention additionally contemplates the beam
stabilization information being communicated to the primary transceiver
unit 3120 via a dedicated control data packet. The primary transceiver
unit 3120 utilizes the beam stabilization information when computing
positional and multiplexing control information.
A beam adjuster 3520 optically positioned between the optical antenna 3510
and the fiber optic coupling 3580 is controlled by the active optics
control system 3540 to maintain efficient coupling of the second light
beam 3845 into the fiber optic cable 3590.
The optical antenna 3510 is mounted on gimbals (not shown) which allow the
optical antenna 3510 to rotate and search for an optical router 3110, or
different transceiver module 3800 of the preferred optical router 3110, by
which to receive service upon installation or upon loss of reception from
a current optical router 3110 or transceiver module 3800.
Alternate Embodiments
An alternate embodiment of the subscriber transceiver unit 3130A is
contemplated in which the light beams are converted to/from electrical
signals at the optical antenna 3510 and transmitted in electronic form to
the input/output device 3600. Hence, alternative transmission mediums for
coupling the optical antenna 3510 to the input/output device 3600 are
contemplated such as coaxial cable or other forms of electrical wires.
Referring now to FIG. 23, an alternate embodiment of the set-top box 3600
of FIG. 9 is shown. A fiber optic "T" 4020 is coupled to the fiber optic
cable 3590. The second light beam 3845 enters the fiber optic "T" 4020 and
passes along the fiber optic cable 3590 to a beam demodulator 4030. The
beam demodulator 4030 is similar to and performs similar functions to the
beam demodulator 3552 of the preferred embodiment. The second light beam
3845 then passes through the fiber optic cable 3590 to an optical data
remover 4040. The optical data remover 4040 preferably comprises a
micro-bender. The data remover 4040 removes any data which has been
modulated on the second light beam 3845. At this point the second light
beam 3845 essentially becomes the third light beam 3855. The third light
beam 3855 is then passed along the fiber optic cable 3590 to a beam
modulator 4050. The beam modulator 4050 is similar to and performs similar
functions to the beam modulator 3562 of the preferred embodiment of the
subscriber transceiver unit 3130A. The third light beam 3855 including the
second data is then passed to the fiber optic "T" 4020 and on to the fiber
optic coupling for transmission to the optical router 3110. The alternate
embodiment advantageously avoids the cost of a light source.
An alternate embodiment of the subscriber transceiver unit 3130A optical
antenna is contemplated in which the antenna is an omni-directional
antenna. The omni-directional antenna is similar to the mirror and lens
set assembly of the alternate embodiment of the optical router 3110.
Additionally, a beam deflector is provided for coupling and decoupling the
light beams into and out of the fiber optic coupling 3580. Alternatively,
the fiber optic coupling 3580 is rotatably mounted. The alternate
embodiment advantageously enables the subscriber unit 3130 to receive
service from an alternate optical router 3110 with minimal interruption of
data transmission. In addition, installation of the subscriber transceiver
unit 3130 is simplified in that virtually no alignment must be performed
upon installation, other than achieving a line of sight path to one or
more optical routers 3110.
The present invention contemplates the use of fiber optic amplifiers, such
as an EDFA (erbium-doped fiber amplifier), in one or more of the various
network elements for amplifying the various light beams in order to
achieve appropriate signal power levels of the various light beams within
the network.
The present invention contemplates the use of atomic line filters, which
act as optical band-pass filters for selected light wavelengths, in one or
more of the various network element receivers for filtering out necessary
light wavelengths, such as sunlight.
The present invention contemplates the use of light sources in the various
network element transmitters with adjustable light beam power control. The
light beam power is adjusted according to factors such as weather
conditions to achieve a proper fade margin for the signal power. A fade
margin of 15 dB at a 1 km range to achieve a 10.sup.-9 bit error rate is
preferred.
Conclusion
Therefore, the present invention comprises a wireless point-to-multipoint
wide area telecommunications network by establishing subscriber
communications channels in a multiplexed manner using atmospherically
transmitted light beams. The network employs an optical router to
establish the communications channels between a primary transceiver unit
and a plurality of subscriber transceiver units by time-multiplexing,
light beam frequency multiplexing, or a combination thereof, the
atmospherically transmitted light beams.
Although the systems and networks of the present invention have been
described in connection with several preferred embodiments, the present
invention is not intended to be limited to the specific forms set forth
herein, but on the contrary, it is intended to cover such alternatives,
modifications, and equivalents, as can be reasonably included within the
spirit and scope of the invention as defined by the appended claims.
* * * * *
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