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| United States Patent |
6,614,980
|
|
Mahony
|
September 2, 2003
|
Connectorized outside fiber optic drop
Abstract
A connectorized outside fiber optic drop that facilitates the deployment of
fiber to the home by connecting a local terminal to a fiber optic
interface device, the outside fiber optic drop including a sheath,
transition fittings, pigtails, fiber optic connectors, and a fiber optic
strand. The sheath is positioned over a middle section of the fiber optic
strand. The transition fittings are attached to the fiber optic sheath
proximate to both ends of the drop. The pigtails attach to the transition
fittings and enclose the fiber optic strand from the transition fittings
to the ends of the fiber optic strand, where the fiber optic connectors
are attached to the fiber optic strand and the pigtails. If the drop
contains more than one fiber optic strand, then one set of pigtails with
connectors is provided for each fiber optic strand.
| Inventors:
|
Mahony; Glenn M. (Alpharetta, GA)
|
| Assignee:
|
BellSouth Intellectual Property Corporation (Wilmington, DE)
|
| Appl. No.:
|
315123 |
| Filed:
|
December 10, 2002 |
| Current U.S. Class: |
385/135; 385/31; 385/137 |
| Intern'l Class: |
G02B 006/02 |
| Field of Search: |
385/134-139,31-35
|
References Cited [Referenced By]
U.S. Patent Documents
| 5067787 | Nov., 1991 | Gillham et al. | 385/50.
|
| 5179617 | Jan., 1993 | Stockman | 385/136.
|
| 5185844 | Feb., 1993 | Bensel et al. | 385/135.
|
| 5440665 | Aug., 1995 | Ray et al. | 385/135.
|
| 5696864 | Dec., 1997 | Smith et al. | 385/135.
|
| 6115516 | Sep., 2000 | Watson et al. | 385/24.
|
| 6301407 | Oct., 2001 | Donaldson | 385/34.
|
Primary Examiner: Zarroli; Michael C.
Attorney, Agent or Firm: Shaw Pittman LLP
Parent Case Text
This is a continuation of U.S. patent application Ser. No. 09/746,649,
filed Dec. 26, 2000, now U.S. Pat. No. 6,522,804, which is herein
incorporated by reference in its entirety, and which is a
continuation-in-part of application Ser. No. 09/372,675, filed Aug. 12,
1999, now U.S. Pat. No. 6,427,035, which is also hereby incorporated by
reference in its entirety. In addition, this application incorporates by
reference the following co-pending related applications in their
entireties: application Ser. No. 09/746,730, "Connectorized Fiber Optic
Interface Device," by Glenn M. Mahony, filed Dec. 26, 2000; and
application Ser. No. 09/746,528, "Connectorized Inside Fiber Optic Drop,"
by Glenn M. Mahony, filed Dec. 26, 2000.
Claims
What is claimed is:
1. A connectorized outside fiber drop for connecting a local terminal of a
fiber to the home network to a fiber optic interface device of the
network, the drop comprising:
at least one fiber optic strand having a first end and a second end;
a sheath enclosing a section of the at least one fiber optic strand;
a first transition fitting attached to the sheath proximate to the first
end of the at least one fiber optic strand;
a second transition fitting attached to the sheath proximate to the second
end of the at least one fiber optic strand;
on each fiber optic strand, a first fiber optic connector attached to the
first end;
on each fiber optic strand, a second fiber optic connector attached to the
second end; and
pigtails enclosing each fiber optic strand between the first transition
fitting and the first fiber optic connector, and between the second
transition fitting and the second fiber optic connector, and
wherein the at least one fiber optic strand floats freely within the
sheath.
2. The connectorized outside fiber drop of claim 1, wherein the first
transition fitting and the second transition fitting contain gel.
3. The connectorized outside fiber drop of claim 1, wherein the pigtails
are coded to identify an individual fiber optic strand of the at least one
fiber optic strand at its first end and its second end.
4. The connectorized outside fiber drop of claim 1, wherein the pigtails
bend to a smaller radius than the sheath.
5. The connectorized outside fiber drop of claim 1, wherein the sheath is
self-supporting and dielectric.
6. The connectorized outside fiber drop of claim 1, wherein the pigtails
are between about 2.2 mm and 3.0 mm in thickness.
7. The connectorized outside fiber drop of claim 1, wherein the
connectorized outside fiber drop has a single-mode attenuation coefficient
of less than 0.4 dB/km between 1270 nm and 1350 nm, and 0.3 dB/km between
1500 nm and 1600 nm.
8. A connectorized outside fiber drop for connecting a local terminal of a
fiber to the home network to a fiber optic interface device of the
network, the drop comprising:
a sheath having a first sheath end and a second sheath end;
a first transition fitting attached to the first sheath end;
a second transition fitting attached to the second sheath end;
a first pigtail attached to the first transition fitting;
a second pigtail attached to the second transition fitting;
a fiber optic strand extending from the first pigtail to the second
pigtail, wherein the fiber optic strand has a first strand end and a
second strand end;
a first fiber optic connector attached to the first strand end; and
a second fiber optic connector attached to the second strand end.
9. The connectorized outside fiber drop of claim 8, wherein the first
transition fitting and the second transition fitting contain gel.
10. The connectorized outside fiber drop of claim 8, wherein the first
pigtail and the second pigtail bend to a smaller radius than the sheath.
11. The connectorized outside fiber drop of claim 8, wherein the pigtails
are adapted to be coiled within the local terminal and the fiber optic
interface device to provide length adjustment of the connectorized outside
fiber drop.
12. The connectorized outside fiber drop of claim 8, wherein the first
pigtail is attached to the first fiber optic connector and wherein the
second pigtail is attached to the second fiber optic connector.
13. The connectorized outside fiber drop of claim 8, wherein the fiber
optic strand floats freely within the sheath.
14. The connectorized outside fiber drop of claim 8, wherein the sheath
complies with Section 6 of GR-20-CORE, Generic Requirements for Optical
Fiber and Optical Fiber Cable, Issue Jul. 2, 1998, except that rated
installation load of cables is 1780 N (400 lbf).
15. The connectorized outside fiber drop of claim 8, wherein the first
transition fitting and the second transition fitting provide strain relief
for the connectorized outside fiber drop.
16. A method for connecting a local terminal to a fiber optic interface
device in a fiber to the home network, the method comprising:
routing a fiber optic strand from the local terminal to the fiber optic
interface device, wherein the fiber optic strand has a first end and a
second end that are connectorized, wherein a middle portion of the fiber
optic strand is enclosed in a sheath, wherein the fiber optic strand is
enclosed in a first pigtail from the first end to the sheath, and wherein
the fiber optic strand is enclosed in a second pigtail from the second end
to the sheath;
placing the first pigtail in the local terminal;
inserting the first end of the fiber optic strand into a connectorized
termination of the local terminal;
placing the second pigtail in the fiber optic interface device; and
inserting the second end of the fiber optic strand into a connectorized
termination of the fiber optic interface device.
17. The method of claim 16, further comprising:
providing a transition fitting between the sheath and the first pigtail;
and
securing the transition fitting to the local terminal.
18. The method of claim 16, wherein placing the first pigtail in the local
terminal comprises storing slack of the first pigtail.
19. The method of claim 16, further comprising:
providing a transition fitting between the sheath and the second pigtail;
and
securing the transition fitting to the fiber optic interface device.
20. The method of claim 16, wherein the sheath runs from the local terminal
to the fiber optic interface device.
Description
BACKGROUND
1. Field of the Invention
The present invention relates to fiber optic cable systems and, more
specifically, to a fiber optic drop for providing continuous,
uninterrupted fiber optic service from a service provider central office
to a subscriber premises.
2. Definitions
The following definitions and descriptions are provided to clearly define
the intended meanings of certain terms used throughout this application.
1. Primary fiber optic strand--a fiber optic strand that is connected to an
electronic device in the central office of a service provider. A primary
fiber optic strand supports a single fiber optic electronic device in the
central office and up to 32 different fiber optic electronic devices
external to the central office, i.e., one fiber optic strand can be split
into 32 different strands for connection to 32 different fiber optic
electronic devices.
2. Fiber optic cable--a cable that contains a multiple number of fiber
optic strands.
3. Distribution splitter--a splitter used in the intermediate portion of a
deployment network, where fiber optic strands are separated and directed
to different locations. Distribution splitters divide a single fiber optic
strand into multiple numbers of strands.
The number of splitters in a network depends on the total number of strands
in the fiber optic cable leading into a central office. The total number
of strands in the cable is at least equal to the number of fiber optic
electronic devices connected at the central office.
For purposes of describing the present invention, it is understood that,
although only two levels of splitting are described herein, any number of
levels could be used to divide a primary fiber optic strand into multiple
strands. In fact, instead of using distribution splitters and local
terminals, a single primary fiber optic strand could go directly to a
local terminal with a 1.times.32 splitter, in which case the local
terminal splits the strand into 32 separate strands which may be connected
to 32 individual fiber optic drops leading to one or more subscriber
premises.
4. Secondary fiber optic strand--the strands that are separated from a
primary fiber optic strand. When a primary fiber optic strand goes through
a first distribution splitter, the separated strands are referred to as
secondary fiber optic strands. The number of secondary fiber optic strands
in the network depends upon the configuration of the splitter, e.g., a
1.times.8 splitter would split a primary fiber optic strand into eight
secondary fiber optic strands. Through each set of splitters, the number
of fiber optic electronic devices supported becomes progressively smaller
until there is only one device per strand.
5. Splice case or splicer--case that attaches to a fiber optic cable and
separates one or more fiber optic strands from the cable to be diverted
away from the cable in a different direction. A splice case contains fiber
optic splices or permanent connections between two fiber optic strands.
6. Local terminal--an outside plant cable terminal used in the prior art
for terminating one or more fiber optic strands near one or more
subscriber premises for connection to copper wire drops into each
subscriber premises. Under the current invention, a local terminal
includes a splitter-terminal apparatus that splits a final fiber optic
strand into multiple strands, each fitted with a connectorized termination
for joining one fiber optic drop.
7. Fiber optic drops--small fiber optic cables that contain one or two
fiber optic strands connecting, for example, the local terminal to a fiber
optic interface device or a fiber optic interface device to an optical
network terminal.
8. Connectorized termination--a fitting for a fiber optic cable or strand
that facilitates quick connections between two different cables or
strands. The fittings are typically plastic connectors with a male and
female side, e.g., SC connectors.
9. Pigtail--in the context of a splitter-terminal, pigtail refers to a
short length of jacketed fiber optic strand permanently fixed to a
component at one end and a connectorized termination at the other end,
such that the pigtail provides a flexible fiber optic connection between
the component and the connectorized termination. When used in the context
of a fiber optic drop, pigtail refers to a short length of jacket (the
fiber optic strand is described separately) fixed to a component (sheath)
at one end and a connectorized termination at the other end.
BACKGROUND OF THE INVENTION
The telecommunications industry has long recognized the many advantages
fiber optic cabling and transmission devices hold over traditional copper
wire and transmission systems. Fiber optic systems provide significantly
higher bandwidth and greater performance and reliability than standard
copper wire systems. For example, fiber optic systems can transmit up to
10 gigabits per second (Gbps), while copper lines transmit at typically
less than 64 kilobits per second (Kbps). Optical fibers also require fewer
repeaters over a given distance to keep a signal from deteriorating.
Optical fibers are immune to electromagnetic interference (from lightning,
nearby electric motors, and similar sources) and to crosstalk from
adjoining wires. Additionally, cables of optical fibers can be made
smaller and lighter than conventional copper wire or coaxial tube cables,
yet they can carry much more information, making them useful for
transmitting large amounts of data between computers and for carrying
bandwidth-intensive television pictures or many simultaneous telephone
conversations.
Despite the many advantages, extremely high installation costs have
discouraged network providers from providing continuous fiber optic
networks extending from central office facilities all the way to
subscriber premises. As used herein, "fiber to the home" (FTTH) refers to
this continuous deployment of fiber optic lines directly to subscriber
premises. On the main distribution lines of a telecommunications network,
the volume of traffic and number of customers often justify the high
installation cost of fiber optic lines. However, thus far, the costs of
deploying fiber optic lines to individual subscriber premises have far
outweighed any potential benefits to network providers.
Therefore, instead of implementing FTTH networks, service providers have
developed strategies to provide some of the benefits of fiber optic
networks without actually deploying fiber all the way to the home (or
other end-subscriber location). One such strategy is known as fiber to the
curb (FTTC), in which fiber optic lines extend from the service provider
to local terminals (also referred to as outside plant cable terminals)
that are situated in areas having a high concentration of subscribers.
Service providers complete the last leg of the network, i.e., from the
local terminals into a subscriber premises, using copper wire drops and
perhaps a high speed data connection, such as an Asynchronous Digital
Subscriber Line (ADSL).
Such FTTC systems provide the benefits of fiber optic systems as far as the
fiber extends, but deprive the subscriber of the full benefit of fiber
optic networks because of the copper wire drops. Indeed, as the weakest
link, the copper wire drops limit the bandwidth capacity for the entire
system. Thus, the only way to gain the full benefit of fiber optic
networking is to use a continuous fiber optic connection from the service
provider's equipment to the subscriber's equipment.
Despite the bandwidth limitations, network providers favor copper wire
drops because of the prohibitively high cost of installing fiber optic
drops using conventional systems and methods. The bulk of these costs can
be attributed to the highly skilled labor and time required to install
fiber optic splitters and to join fiber optic drops to fiber optic strands
coming from the splitters. In conventional systems and methods, fiber
optic networks use fiber optic splitters and splice cases to route fiber
optic strands throughout a distribution network. The fiber optic splitters
and splice cases allow a fiber optic strand to branch into multiple
strands to widen a network's coverage area. In conventional networks,
design engineers use splitters and splice cases to route strands from
electronic devices at the central office to distribution locations, such
as those in housing developments.
To provide fiber optic drops to individual subscriber premises from the
distribution locations, network providers could manually splice individual
fiber optic drops onto each strand. Or, alternatively, each time that a
new subscriber requires fiber optic service, a network provider could
manually fit the fiber optic strands with a connector for joining a fiber
optic drop that runs to the new subscriber's premises. However, whether
manually splicing individual fiber optic drops or fitting fiber optic
strands with connectors for each service request, network providers must
use highly skilled technicians to complete the specialized tasks. These
technicians tend to be both expensive and in short supply. Thus, in light
of the conventional systems and methods for deploying fiber optic cable,
network providers rightly view the deployment of individual fiber optic
drops from these distribution locations as an expensive and time-consuming
endeavor.
To avoid the high costs of manually splicing fiber or fitting connectors
onto fiber, network providers could use conventional fiber optic splitters
to facilitate connections. However, conventional fiber optic splitter
apparatus are difficult to connect. The fiber optic splitters known in the
prior art are designed to accommodate permanent connections. The splitters
are installed at network branch locations at which the number and
structure of incoming and outgoing strands rarely change. In contrast, in
deploying fiber to the home from the distribution locations, network
providers must have the flexibility to add and disconnect services on an
individual subscriber level. Thus, the permanent nature of conventional
fiber optic splitter apparatus is inappropriate for fiber to the home
deployment.
Thus, in a typical network, instead of providing fiber optic drops from the
distribution locations to the subscriber premises, network providers run
fiber optic strands from the distribution locations to electronic devices
located in local terminals, e.g., aerial or buried terminals. These local
terminals are situated in the center of a cluster of subscriber houses.
The fiber optic service ends at these local terminals, and copper wire
drops complete the connection to the subscriber premises. The copper wire
drops are used because no device exists in the prior art that facilitates
an economical, easy-to-connect fiber optic drop to the subscriber
premises. Although the prior art includes fiber optic splitters and
splices for network deployment, the existing splitters and splices are not
appropriate for installing individual drops to subscribers because they do
not provide a terminating function and they are not combined into an
easy-to-deploy unit.
In addition, because the prior art lacks a device to connect a fiber optic
drop to a subscriber premises, the prior art also lacks devices for
implementing fiber to the home from the distribution locations to the
subscriber's equipment inside the subscriber's premises. Thus far,
connecting distribution locations to subscriber equipment has been limited
to copper. Devices that bring copper from the curb into the home are well
known in the art. For example, one such device is a network interface
device produced by Corning Cable Systems of Hickory, N.C. In stark
contrast, however, the prior art lacks devices dedicated to bringing fiber
from the curb to the home.
SUMMARY OF THE INVENTION
The present invention is a connectorized outside fiber optic drop that
facilitates the deployment of fiber to the home. The connectorized outside
fiber drop includes a sheath, transition fittings, pigtails, fiber optic
connectors, and a fiber optic strand. The sheath is positioned over a
middle section of the fiber optic strand. The transition fittings are
attached to the sheath proximate to both ends of the outside fiber optic
drop. The pigtails attach to the transition fittings and enclose the fiber
optic strand from the transition fittings to the ends of the fiber optic
strand, where the fiber optic connectors are attached to the fiber optic
strand and the pigtails. If the drop contains more than one fiber optic
strand, then one set of pigtails with connectors is provided for each
fiber optic strand.
In facilitating the deployment of fiber to the home, the present invention
functions within a fiber optic network that provides continuous fiber
optic strands from a service provider's central office to individual
subscriber's premises. As shown schematically in FIG. 1a, the network
comprises a central office fiber optic electronic device, a primary fiber
optic cable (or strand), distribution splitters, secondary fiber optic
cables (or strands), local terminals (outside plant cable terminals), and
fiber optic drops to subscriber premises. In replacing the inferior fiber
to the curb deployments of the prior art, the present invention
facilitates a system that economically deploys complete, uninterrupted
fiber optic services to individual subscribers.
To facilitate fiber to the home, the present invention helps connect the
local terminals of the network to the subscriber premises, i.e., the
present invention helps to extend fiber from the "curb" to the "home." As
shown in FIG. 1b, this portion of the network includes a fiber optic
splitter-terminal apparatus in the local terminal, the connectorized
outside fiber drop of the present invention in communication with the
fiber optic splitter-terminal apparatus, a fiber optic interface device in
communication with the connectorized outside fiber drop, and a
connectorized inside fiber drop in communication with the fiber optic
interface device. The connectorized inside fiber drop connects to optical
network terminals in the subscriber premises, which in turn connect to the
subscriber's fiber optic electronic devices. The fiber optic electronic
devices connect to home consumer electronic devices, such as personal
computers or telephones. Together, these components enable the
cost-effective installation of fiber to the home.
Accordingly, an object of the present invention is to provide a fiber optic
network that delivers uninterrupted fiber optic service from a central
office to subscriber premises.
Another object of the present invention is to provide an inexpensive
apparatus that connects a local terminal to a fiber optic interface
device.
Another object of the present invention is to provide an outside fiber
optic drop that can be installed without requiring splicing.
These and other objects of the present invention are described in greater
detail in the detailed description of the invention, the appended
drawings, and the attached claims.
DESCRIPTION OF THE DRAWINGS
FIG. 1a is a schematic diagram of a fiber optic network from a central
office to subscriber premises, according to a representative embodiment of
the present invention.
FIG. 1b is a schematic diagram of the distribution of a fiber optic drop
from a local terminal to a subscriber premises, according to preferred
embodiments of the present invention.
FIG. 1c is a schematic diagram of a fiber optic network, showing the
deployment to individual subscriber premises, according to a
representative embodiment of the present invention.
FIG. 2a is a schematic diagram of a splitter-terminal package with a
1.times.4 splitter and a connectorized termination for the incoming fiber
optic strand, according to a representative embodiment.
FIG. 2b is a schematic diagram of a splitter-terminal package with a
1.times.8 splitter and a connectorized termination for the incoming fiber
optic strand, according to a representative embodiment.
FIG. 2c is a schematic diagram of a splitter-terminal package with a
1.times.4 splitter and a pigtail for the incoming fiber optic strand,
according to a representative embodiment.
FIG. 2d is a schematic diagram of a splitter-terminal package with a
1.times.8 splitter and a pigtail for the incoming fiber optic strand,
according to a representative embodiment.
FIG. 3 is a schematic diagram of a splitter-terminal package with two
incoming fiber optic strands and two 1.times.4 splitters, according to a
representative embodiment.
FIG. 4a is a schematic diagram of a pole-mounted splitter-terminal package
for an aerial deployment system with a connectorized termination for the
incoming fiber optic strand, according to a representative embodiment.
FIG. 4b is a schematic diagram of a pole-mounted splitter-terminal package
for an aerial deployment system with a pigtail for the incoming fiber
optic strand, according to a representative embodiment.
FIG. 5 is a schematic diagram of a strand-mounted splitter-terminal package
for an aerial deployment system, according to a representative embodiment.
FIG. 6a is a schematic diagram of a pedestal-mounted splitter-terminal
package for a buried deployment system with the splice case enclosed in
the pedestal shell, according to a representative embodiment.
FIG. 6b is a schematic diagram of a pedestal-mounted splitter-terminal
package for a buried deployment system with the splice case located
separate from the pedestal shell and with the incoming fiber optic cable
connected to the splitterterminal package by a pigtail, according to a
representative embodiment.
FIG. 6c is a schematic diagram of a pedestal-mounted splitter-terminal
package for a buried deployment system with the splice case located
separately from the pedestal shell, and with the incoming fiber optic
cable connected to the splitter-terminal package with a connectorized
termination, according to a representative embodiment.
FIG. 7a is a schematic diagram of a connectorized outside fiber drop
according to a representative embodiment of the present invention.
FIG. 7b is a schematic diagram of a connectorized outside fiber drop having
two fiber optic strands, according to a representative embodiment of the
present invention.
FIG. 8a is a schematic diagram of a fiber optic interface device, according
to a representative embodiment.
FIG. 8b is a schematic diagram of a grommet for a fiber optic interface
device, according to a representative embodiment.
FIGS. 8c and 8d are schematic diagrams of termination hardware in a fiber
optic interface device, according to representative embodiments.
FIG. 9 is a flowchart outlining how a fiber optic interface device is
installed and how the pigtails of an outside fiber drop and an inside
fiber drop are installed in the fiber optic interface device, according to
a representative embodiment.
FIG. 10a is a schematic diagram of a connectorized inside fiber drop
according to a representative embodiment.
FIG. 10b is a schematic diagram of a connectorized inside fiber drop having
two fiber optic strands, according to a representative embodiment.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a connectorized outside fiber optic drop that
connects a local terminal to a fiber optic interface device mounted on a
subscriber premises. In serving this function, the present invention
facilitates the deployment of fiber to the home. To provide the context in
which the present invention operates, the following subheadings describe
the present invention, a representative fiber optic network deployment
system that uses the present invention, and the specific components with
which the present invention interacts as a part of that system.
Fiber Optic Network Deployment System
FIGS. 1a and 1b illustrate a complete fiber to the home deployment system,
according to a representative embodiment of the present invention. FIG. 1a
shows the distribution of fiber optic lines on a network level. On an
individual subscriber level, FIG. 1b shows the distribution of a fiber
optic drop from a local terminal to a subscriber premises.
As shown in FIG. 1a, a representative embodiment of the fiber to the home
deployment system of the present invention includes a central office 100,
a primary fiber optic cable 102 having a plurality of primary fiber optic
strands 102a, a plurality of distribution splitters 104, a plurality of
secondary fiber optic cables 106 having a plurality of secondary fiber
optic strands 106a, a plurality of local terminals 108 (outside plant
cable terminals), each containing a fiber optic splitterterminal apparatus
(not shown in FIG. 1a), a plurality of fiber optic drops 110, and a
plurality of subscriber premises electronic equipment 112.
As shown in FIG. 1a, the system components are connected in a branched
network. Starting from the central office 100, primary fiber optic cables
102 run from the service provider to locations throughout the network. At
various points in the network, primary fiber optic strands 102a are
spliced from primary fiber optic cables 102 into a plurality of
distribution splitters 104. Each distribution splitter 104 divides a
primary fiber optic strand 102a into a secondary fiber optic cable 106. As
secondary fiber optic cable 106 passes near clusters of subscribers,
splice cases 107 splice secondary fiber optic strands 106a off of
secondary fiber optic cable 106 to be directed toward the respective
service areas. The number of secondary fiber optic strands 106a in cable
106 supported by primary strand 102a depends on the configuration of
distribution splitter 104. For example, a 1.times.8 distribution splitter
splits a primary fiber optic strand into eight secondary fiber optic
strands 106a. Each of the eight secondary fiber optic strands 106a
accommodates four electronic devices for a total of thirty-two supported
end devices per primary fiber optic strand 102a.
Within a service area, each secondary fiber optic strand 106a is in
communication with a local terminal 108. Local terminals 108 include a
splitterterminal apparatus for further splitting secondary fiber optic
strand 106a into a plurality of fiber optic drops 110. The
splitter-terminal apparatus replaces the conventional fiber-to-copper
interface and provides a fiber optic connector interface between a fiber
optic strand and multiple fiber optic drops to subscriber premises. Each
fiber optic drop 110 serves one fiber optic electronic device on
subscriber premises 112 (assuming, of course, that local terminals 108
split secondary fiber optic strands 106a into fiber optic drops 110 of a
single strand).
In dividing primary fiber optic cable 102 down to a single fiber optic drop
110, the representative network of FIG. 1a uses the following distribution
scheme. For simplicity, this example assumes that one primary fiber optic
strand 102a extends from central office fiber optic electronic device 150.
In other words, primary fiber optic cable 102 consists of one primary
fiber optic strand 102a. From central office 100, primary fiber optic
strand 102a goes through one 1.times.8 distribution splitter 104,
resulting in eight separate secondary fiber optic strands 106a. These
eight secondary fiber optic strands are bundled in secondary fiber optic
cable 106. At locations near each service area, splice cases 107 splice
secondary fiber optic strands 106a off of secondary fiber optic cable 106
and direct secondary fiber optic strands 106a toward intended service
areas. Once inside the service areas, the eight secondary fiber optic
strands 106a are routed to local terminals 108 that contain 1.times.4
splitter-terminal packages. Each 1.times.4 splitter-terminal package
yields four separate fiber optic drops 110, for a total of 32 separate
fiber optic drops. In this example, local terminals 108 are situated
between four subscriber premises 112, with each subscriber having one
fiber optic electronic device. Thus, 32 subscribers each having one fiber
optic electronic device, are served from a single primary fiber optic
strand 102 from central office 100.
FIG. 1b shows the fiber to the home deployment system on the individual
subscriber level, from a local terminal 108 to a subscriber premises 112.
In other words, FIG. 1b illustrates the specific components that form the
fiber optic drops 110 of FIG. 1a. As shown in FIG. 1b, this portion of the
fiber optic network deployment system includes a connectorized outside
fiber drop 120, a fiber optic interface device 122, and a connectorized
inside fiber drop 124. Connectorized outside fiber drop 120 is in
communication with local terminal 108 and fiber optic interface device
122, and can be deployed from a pole 109 in an aerial application or from
a pedestal 111 in a buried application. Fiber optic interface device 122
is mounted on subscriber premises 112. In turn, connectorized inside fiber
drop 124 is in communication with fiber optic interface device 122 and
optical network terminal 126. Optical network terminal 126 provides a
termination point to which a subscriber fiber optic electronic device 128
can be connected. A home consumer electronic device, such as a personal
computer, television, or telephone, is then connected to subscriber fiber
optic electronic device 128. Thus, as illustrated in FIGS. 1a and 1b, the
representative fiber optic network deployment system of the present
invention provides complete, uninterrupted fiber optic service from
central office 100 to subscriber fiber optic electronic devices 128.
The representative fiber optic network deployment system can support data,
analog video, and voice transmission, with each configuration requiring a
different type of fiber optic electronic device 150 in central office 100.
In addition, for voice, video, or data transmission, a plurality of
optical line terminals would be connected to the plurality of primary
fiber optic strands 102a in cable 102. A preferred embodiment of the
deployment system eliminates the use of active components (e.g., remote
terminal sites containing multiplexers, host digital terminals, digital
loop carrier systems, and other electronic equipment) throughout the
distribution network. This preferred deployment system uses active
components only at the ends of the network, i.e., in the service
providers' central office electronic equipment and the electronic
equipment located in subscribers' premises. The resulting passive optical
network greatly reduces the probability of trouble reports and decreases
the cost of provisioning, maintaining, and repairing the system.
FIG. 1c illustrates a fiber optic deployment within a community of
subscribers. The primary fiber optic cable from the central office enters
the community at three hub locations 150. At these locations 150, the
primary strands are split and diverted to individual branches. Along the
branches, a multiple number of terminals are present. Each terminal
location along these branches indicates the number of drops leading to
individual fiber optic electronic devices at subscriber locations.
Splitter-Terminal Apparatus
A splitter-terminal apparatus combines into a single inexpensive apparatus
a means for splitting and terminating a fiber optic strand for deployment
to a cluster of subscriber premises. The splitter-terminal provides easily
accessible, easily connectable terminations from which to run fiber optic
drops to subscriber premises. Further, the splitter-terminal apparatus
provides strain relief for the delicate fiber optic strands being split or
being joined to the fiber optic drops. Finally, as described below, the
splitter-terminal apparatus can be modified to accommodate aerial and
buried deployment applications.
As shown in FIG. 2a, the preferred embodiment of the splitter-terminal
apparatus is a splitter-terminal package 199 that includes a splitter 200,
a plurality of outgoing connectorized terminations 201, and a housing 202.
Connectorized terminations 201 could be made with any number of connection
fittings known in the art, e.g., SC connectors or ST connectors. Splitter
200 receives incoming fiber optic strand 203 and splits the strand into a
plurality of single fiber optic strands 204. Single fiber optic strands
204 connect to the plurality of outgoing connectorized terminations 201.
Splitter 200 and connectorized terminations 201 are attached to housing
202 to maintain a fixed distance between the components and to provide
strain relief to the delicate fiber optic strands enclosed within housing
202.
The capacity of incoming fiber optic strand 203 and the configuration of
splitter 200 dictate the maximum number of strands making up the plurality
of single fiber optic strands 204. The number of connectorized
terminations making up the plurality of outgoing connectorized
terminations 201 is equal to the number of lines making up the plurality
of single fiber optic strands 204. As an example, splitter 200 could be a
1.times.4 splitter in which an incoming fiber optic strand 203 is split
into four separate strands 204 that connect to four separate outgoing
connectorized terminations 201, as shown in FIG. 2a.
In a preferred embodiment of the splitter-terminal apparatus, incoming
fiber optic strand 203 is connected to incoming connectorized termination
205 mounted in the wall of housing 202. In this manner, splitter-terminal
package 199 is selfcontained, with connectorized terminations 201 and 205
on each end. Connectorized terminations 201 and 205 enable fiber optic
service providers to quickly and easily install the splitter-terminal
package 199 between a splice case and a fiber optic drop to a subscriber
home.
In another embodiment of the splitter-terminal apparatus, shown in FIGS. 2c
and 2d, the splitter-terminal package includes a pigtail permanently
connected to the splitter. In this embodiment, the free end of the pigtail
is fitted with a connectorized termination for easily connecting to an
incoming fiber optic strand. This pigtail extends through the wall of the
splitter-terminal housing so that the internal splitter-terminal
components remain protected by the housing. As shown in FIG. 2c, in
another embodiment of the splitter-terminal apparatus, fiber optic strand
252 extends from splitter 200 through housing 202 to connectorized
termination 251, forming pigtail 250. In this embodiment,
splitter-termination package 199 in FIG. 2c is a self-contained package
similar to splitter-termination package 199 in FIG. 2a. However, pigtail
250 provides more flexibility in reaching an adjacent splice case. These
pigtails are more suited for manufactured assemblies, where an entire
splitter-terminal package is delivered to the field.
A splitter-termination package could be arranged in a variety of ways,
depending on the capacity of the incoming fiber optic strand and the
configuration of the splitter. For instance, instead of the 1.times.4
splitter shown in FIG. 2a, a 1.times.8 splitter could be used, thereby
requiring eight outgoing connectorized terminations. FIGS. 2b and 2d
illustrate this 1.times.8 configuration with eight strands making up the
plurality of single fiber optic strands 204 and eight connectorized
terminations making up the plurality of outgoing connectorized
terminations 201. Further, to accommodate two incoming fiber optic
strands, e.g., one for data and one for video, two splitters could be used
to separate the two incoming fiber optic strands. FIG. 3 shows two
incoming strands leading into two 1.times.4 splitters 300 and 301, with
two separate pluralities of outgoing fiber optic strands 304a and 304b
leading to outgoing connectorized terminations 302a and 302b.
In a further representative embodiment of the splitter-terminal apparatus,
splitter-terminal package 199 is installed as a component of a larger
deployment system, e.g., a pole-mounted aerial system, a strand-mounted
aerial system, or a pedestal-mounted system for buried lines. These larger
deployment systems include a splice case and fiber optic drops, in
addition to the splitter-terminal package. The splice case connects to a
secondary fiber optic cable and separates a secondary fiber optic strand
from the bundle. The separated strand becomes the incoming fiber optic
strand connected to the incoming side of the splitter-terminal package. As
shown in FIGS. 4a through 6c, splitter-terminal package 199 is installed
between splice case 400 and the plurality of fiber optic drops 404 leading
to the subscriber premises.
Aerial deployment systems arrange the splice case, splitter-terminal
package, and fiber optic drops in a variety of configurations. Two
examples are pole-mounted systems and strand-mounted systems, shown in
FIGS. 4a-4b and 5, respectively. FIGS. 4a and 4b illustrate the use of
splitter-terminal package 199 in a pole-mounted aerial deployment system.
In a pole-mounted system, the splice case is attached to the secondary
fiber optic cable, the splitter-terminal package is mounted on the pole,
the incoming fiber optic strand runs from the splice case to the
splitter-terminal package, and fiber optic drops connected to the outgoing
side of the splitter-terminal package run from the pole to the subscriber
premises.
Thus, splice case 400 connects to and splices fiber optic cable 401,
diverting incoming fiber optic strand 203 to splitter-terminal package 199
mounted on pole 402. As shown in FIG. 4a, incoming fiber optic strand 203
connects to splitter-terminal package 199 through connectorized
termination 205. In another embodiment as shown in FIG. 4b, incoming fiber
optic strand 203 and connectorized termination 205 are replaced by pigtail
250 as described for FIGS. 2c and 2d above. In this embodiment,
connectorized termination 251 plugs directly into splice case 400, as
shown in FIG. 4b.
To complete the pole-mounted aerial deployment system, the plurality of
fiber optic drops 404 connects to the plurality of outgoing connectorized
terminations 201. Each fiber optic drop 404 extends to a subscriber
premises.
FIG. 5 illustrates the use of splitter-terminal package 199 in a
strand-mounted aerial deployment system. In a strand-mounted system, both
the splice case and the splitter-terminal package are mounted inside a
splice case housing that is lashed with wire to a secondary fiber optic
cable. The splice case splices off the incoming fiber optic strand that
runs from the splice case to the splitter-terminal. The fiber optic drops
connected to the outgoing side of the splitter-terminal package run from
the strand-mounted splice case housing directly to the subscriber
premises.
Thus, as shown in FIG. 5, splice case 400 and splitter-terminal package 199
are contained in splice case housing 500. Splice case housing 500 is
lashed to fiber optic cable 401 with wire. Splice case 400 connects to and
splices fiber optic cable 401, diverting incoming fiber optic strand 203
to the incoming side of splitter-terminal package 199 mounted inside
splice case housing 500. On the outgoing side of splitter-terminal package
199, the plurality of connectorized terminations 201 are connected to
plurality of fiber optic drops 404.
FIGS. 6a-6c illustrate the use of splitter-terminal package 199 in a
pedestal-mounted deployment system for buried lines. Buried deployment
systems mount the splitter-terminal package and splice case in a pedestal
shell that rests on the ground. As shown in FIG. 6a, a secondary fiber
optic cable enters and exits the pedestal shell from the pedestal shell
bottom. The splice case connects to the secondary fiber optic cable and
splices off an incoming fiber optic strand that runs from the splice case
to the splitter-terminal package. The fiber optic drops connected to the
outgoing side of the splitter-terminal exit the pedestal through the
pedestal shell bottom and proceed underground to the subscriber premises.
In one embodiment, as shown in FIG. 6a, splitter-terminal package 199 and
splice case 400 are contained in and mounted on pedestal shell 600. Fiber
optic cable 401 enters pedestal shell 600 through the bottom of pedestal
600 and connects to splice case 400. Splice case 400 splices fiber optic
cable 401, diverting incoming fiber optic strand 203 to the incoming side
of splitter-terminal package 199. On the outgoing side of
splitter-terminal package 199, the plurality of connectorized terminations
201 connects to the plurality of fiber optic drops 404. The plurality of
fiber optic drops 404 exits pedestal shell 600 through its bottom, and
travels underground to subscriber premises.
As shown in FIG. 6b, in another embodiment of the buried deployment system,
the splice case resides underground with a secondary fiber optic cable, as
opposed to being contained in the pedestal shell. As shown, splice case
400 is positioned underground and not inside pedestal shell 600.
Splitter-terminal package 199 is housed in and mounted on pedestal shell
600. Splice case 400 connects to and splices fiber optic cable 401
underground, diverting incoming fiber optic strand 203 to pedestal shell
600. Incoming fiber optic strand 203 enters pedestal shell 600 through its
bottom. Once inside pedestal shell 600, incoming fiber optic strand 203
connects to the incoming side of splitter-terminal package 199. On the
outgoing side of splitter-terminal package 199, the plurality of
connectorized terminations 201 connects to the plurality of fiber optic
drops 404. The plurality of fiber optic drops exits pedestal shell 600
through its bottom, and travels underground to subscriber premises.
In either of the configurations of FIGS. 6a and 6b, incoming fiber optic
strand 203 connects to splitter-terminal package 199 with connectorized
terminations or is replaced with a pigtail having a connectorized
termination on its the end.
On the outgoing side of the splitter-terminal package, the outgoing
connectorized terminations connect to fiber optic drops. Each fiber optic
drop proceeds to a subscriber premises for connecting a subscriber's fiber
optic electronic device to fiber optic service. Thus, continuous,
uninterrupted fiber optic service is delivered all the way to the
subscriber premises serving subscriber electronic devices (e.g.,
television, telephone, personal computer). This fiber optic network
deployment system eliminates the inferior copper drop connections
prevalent in the prior art.
In each of the above-described deployment systems, the incoming fiber optic
strand running from the splice case to the splitter-terminal package can
be connectorized or spliced. The use of either spliced or connectorized
terminations for the splice case and incoming side of the
splitter-terminal package depends upon the service provider's intended
method of installation. If the service provider desires more factory
pre-assembly, the incoming fiber optic strand would be spliced to the
splice case and splitter-terminal package at the factory and delivered as
a pre-connected unit. If field assembly were desired, service providers
would manufacture the splice case and incoming side of the
splitter-terminal package with connectorized terminations so that the
components could be connected in the field. This configuration would also
allow customizing of the length of the incoming fiber optic strand to
accommodate field requirements.
Connectorized Outside Fiber Drop
A connectorized outside fiber drop provides fiber connectivity between a
splitter-terminal and a fiber optic interface device. For example, as
shown in FIG. 1b, connectorized outside fiber drop 120 provides
communication between splitter-terminal 108 and fiber optic interface
device 122. The connectorized ends eliminate the need for fiber splicing
and reduce installation and replacement costs.
FIG. 7a illustrates a connectorized outside fiber drop 700 according to a
representative embodiment. As shown, outside drop 700 includes a section
of outside plant sheath 702, transition fittings 704, pigtails 706, fiber
optic connectors 708, and a fiber optic strand 710. Outside plant sheath
702 is positioned over a middle section of fiber optic strand 710. The
design of drop 700 allows fiber optic strand 710 to float freely within
outside plant sheath 702 to prevent stress on fiber optic strand 710
during installation and normal operation.
Outside plant sheath 702 preferably contains no metallic strength members,
to avoid bonding and grounding requirements at a subscriber premises. Both
ends of outside plant sheath 702 are attached to transition fittings 704.
Transition fittings 704 provide a structure with which to secure drop 700
with adequate strain relief. Transition fittings 704 also provide a
structure to transition between outside plant sheath 702 and pigtails 706.
Pigtails 706 attach to transition fittings 704 and enclose fiber optic
strand 710 from transition fittings 704 to the ends of fiber optic strand
710, at which point connectors 708 are attached to fiber optic strand 710
and pigtails 706.
If the connectorized outside fiber drop contains more than one fiber optic
strand, then one set of pigtails with connectors is provided for each
fiber optic strand, as FIG. 7b shows for an outside drop 703 having two
fiber optic strands 713. With two fiber optic strands 713, outside drop
703 can support two separate lines of communication, e.g., video and data.
Outside plant sheath 702 provides environmental protection for fiber optic
strand(s) 710 between a splitter-terminal and a fiber optic interface
device. Therefore, sheath 702 must be appropriate for the particular
application for which a drop is used, e.g., aerial,.buried, or underground
installations. For aerial applications, sheath 702 is preferably
self-supporting and dielectric, capable of withstanding anticipated
stresses such as wind-loading, ice loading, and ultra-violet exposure. As
an example, sheath 702 could conform to the requirements of Section 6 of
GR-20-CORE, Generic Requirements for Optical Fiber and Optical Fiber
Cable, Issue Jul. 2, 1998, with the exception that the rated installation
load of cables be 1780 N (400lbf). Section 6 of GR-20-CORE is hereby
incorporated by reference in its entirety. For buried applications, sheath
702 must withstand anticipated stresses and deterioration mechanisms such
as water penetration.
Transition fittings 704 are attached to outside plant sheath 702 and
pigtails 706 at points proximate to the ends of outside fiber drop 700.
Transition fittings 704 provide strain relief for outside fiber drop 700
and for fiber optic strand 710 as it passes from sheath 702 to pigtails
706. Optionally, transition fittings 704 may include gel to further
protect fiber optic strand 710. Transition fittings 704 also provide a
sturdy structure that can be attached to the housings of splitter-terminal
108 and fiber optic interface device 122. For example, transition fittings
704 could be clamped inside a female fitting that is integral to a
housing. Alternatively, transition fittings 704 could be secured to a
housing using a cable tie.
Pigtails 706 are jackets that protect individual fiber optic strands 710
inside the housings of splitter-terminal 108 and fiber optic interface
device 122. In relation to outside plant sheath 702, pigtails 706 are more
flexible, allowing fiber optic strands 710 to bend at a smaller radius.
This flexibility enables installers to easily route outside drop 700 to
connectors within the housings of splitter-terminal 108 and fiber optic
device 122. The flexibility also allows installers to take up any slack in
fiber optic strands 710 by coiling strands 710 within a housing. In a
representative embodiment, the jacket of pigtails 706 is made of extruded
thermal plastic of a thickness of 2.2 mm to 3.0 mm. In addition, when more
than one fiber optic strand 710 is contained in the connectorized outside
fiber drop 700 (as shown in FIG. 7b), pigtails 706 are color coded to
identify the same fiber optic strand on both ends of drop 700.
Connectors 708 are compatible with the connectorized terminations provided
in splitter-terminal 108 and fiber optic interface device 122. Depending
on the particular application, suitable connectors could include such
types as SC, ST, and FC connectors. As an example, connectors 708 could
conform to GR-326-CORE, Generic Requirements for Single-Mode Optical
Connectors and Jumper Assemblies, Issue Dec. 2, 1996 (with the
clarification that connectors 708 meet the reflectance performance of -55
dB for all conditions). GR-326-CORE is hereby incorporated by reference in
its entirety.
As a whole, the transmission performance of connectorized outside fiber
drop 700 must be consistent with the requirements of the fiber optic
network system in which it operates. For example, the single-mode fiber
attenuation coefficient of outside drop 700 should be less than 0.4 dB/km
between 1270 nm and 1350 nm, and 0.3 dB/km between 1500 nm and 1600 nm.
The attenuation should be uniformly distributed throughout the length of
outside drop 700 such that there are no discontinuities greater than 0.1
dB for single-mode fiber at any design wavelength. In addition, all fibers
in outside drop 700 should not exhibit point discontinuities with a
measured loss greater than 0.10 dB or a reflectance greater than -45 dB at
1310 nm or 1550 nm.
Connectorized outside fiber drop 700 must also meet the structural and
material specifications of the fiber optic network system in which it
operates. For example, outside drop 700 should meet all appropriate
requirements of the National Electrical Code (NEC), e.g., NEC NFPA 70. In
addition, outside drop 700 should meet the flammability requirements of
UL-1581 when tested in accordance with the VW-1 Vertical Wire Flame
Test--All Wires Flame Test procedure.
The overall length of connectorized outside fiber drop 700 depends upon the
typical lengths between splitter-terminals and subscriber premises in a
particular fiber optic network system. Outside drop 700 is designed to be
manufactured in predetermined lengths that accommodate these typical
network configurations. In this manner, an installer first estimates the
distance between a particular splitter-terminal and the particular
location at which the fiber optic interface device will be mounted on the
subscriber premises. The installer then selects a fiber optic drop of an
appropriate predetermined length.
Pigtails 706 provide mechanical protection for the fiber optic strand
during installation and normal operation. Pigtails 706 also provide a
means for accommodating variations in the distance between a strain relief
point (where the transition fitting is secured) and an adapter within a
splitter-terminal or fiber optic interface device. As such, the length of
pigtails 706 depends upon the design of the splitter-terminal and fiber
optic interface device. At a minimum, a pigtail must be long enough to
reach the adapter in a splitter-terminal or a fiber optic interface
device, while maintaining at least the minimum allowable bend radius of
the fiber optic strand. However, pigtails 706 must not be so long that the
routing hardware of a splitter-terminal or fiber optic interface device
(discussed below) is unable to manage the slack. Thus, in light of these
guidelines, a suitable length for pigtails 706 could range from, for
example, 18 to 36 inches for a typical installation.
Fiber Optic Interface Device (FID)
As shown in FIG. 1b, fiber optic interface device 122 provides an interface
point between connectorized outside fiber optic drop 120 and connectorized
inside fiber drop 124. As this interface, FID 122 receives one or more
fiber optic strands from drop 120, manages the slack of the fiber optic
strand(s), protects the strand(s) from the outside environment, and
connects the strand(s) to connectorized inside fiber drop 124. In doing
so, FID 122 provides a clear demarcation point between
network-operator-owned materials and customer-owned materials, provides a
convenient fiber optic test point outside of the customer's home, and
allows for the efficient installation, maintenance, and replacement of
outside drop 120, all without affecting the customer's line configuration
within the home.
FIG. 8a illustrates a fiber optic interface device 800 according to a
representative embodiment. As shown, FID 800 includes a housing 802 having
ports 804 and 806, termination hardware 808, routing hardware 810, and one
or more adapters 812.
Housing 802 of FID 800 protects the interior components against
environmental damage, and can be constructed of metal, hardened plastic,
or any other material suitable for the intended application. Housing 802
is adapted to be mounted on the side of a customer's house and is
preferably capable of withstanding temperatures ranging from -40 degrees
Celsius to 85 degrees Celsius. For convenient and secured access to the
internal components, housing 802 preferably includes a swinging, lockable
door. In addition, housing 802 is sealed to prevent wind driven rain from
affecting the internal components. As a part of this seal, ports 804 and
806 of housing 800 preferably include grommets that prevent infiltration
from such hazards as water and insects. FIG. 8b illustrates a
representative embodiment of a grommet 820 in which a slit 822 is cut to
receive outside drop 120 or inside drop 124. The remaining portion of
grommet 820 is solid and impervious. As an example, grommet 820 could be
made of a flexible rubber or a plastic elastomer.
As shown in FIG. 8a, port 804 is adapted to receive connectorized outside
fiber drop 120. Similarly, port 806 is adapted to receive connectorized
inside fiber drop 124. The outside plant sheaths of outside drop 120 and
inside drop 124 slide through ports 804 and 806 to enter FID 800. From
ports 804 and 806, outside drop 120 and inside drop 124 extend into
housing 802, with transition fittings positioned just above ports 804 and
806. Termination hardware 808 secures the transition fittings of outside
drop 120 and inside drop 124 to housing 802.
Termination hardware 808 is positioned above ports 804 and 806 to secure
outside drop 120 and inside drop 124, and to provide necessary strain
relief. To reduce labor costs, termination hardware 808 is easily
installed, removed, and replaced. For example, as shown in FIG. 8c,
suitable termination hardware 808 could include a raised slot 830 in the
back of housing 802, through which a cable tie 832 is placed. Cable tie
832 wraps around and secures the transition fitting of outside drop 120 or
inside drop 124 (transition fittings 704 and 1004, respectively).
Alternatively, as shown in FIG. 8d, termination hardware 808 could be a
hose clamp 834 attached to housing 802 through which the transition
fitting 704 or 1004 of outside drop 120 or inside drop 124, respectively,
is placed and secured. (Although FIG. 8a shows termination hardware 808 in
the context of FID 800, termination hardware 808 could be used in a
splitter-terminal or optical network terminal as well.)
As shown in FIG. 8a, routing hardware 810 routes the pigtails of outside
drop 120 and inside drop 124 to adapter 812. Routing hardware. 810 stores
any extra length in the pigtails and is shaped to keep the fiber optic
strands within a proper bend radius. In storing slack, routing hardware
810 enables an installer to adjust the length of a drop without removing
the connectors and without splicing. Conventional copper network interface
devices lack this unique routing hardware. A pigtail with slack wraps
around routing hardware 810 until all the slack is taken up and the
remaining portion of the pigtail is long enough to reach adapter 812.
Although shown as separate semicircles in FIG. 8a, routing hardware 810
could be any shape or shapes that satisfy the above-described functions,
e.g., a continuous circle or oval would also perform well. (Although FIG.
8a shows routing hardware 810 in the context of FID 800, routing hardware
810 could be used in a splitter-terminal or optical network terminal as
well.) As another alternative for managing slack storage, routing hardware
810 could be plastic routing clips evenly spaced in a pattern (e.g., a
circular pattern) within FID 800.
As shown in FIG. 8a, FID 800 also includes at least one fiber optic
connector adapter 812, which is a connectorized termination that connects
the connector of outside drop 120 to the connector of inside drop,124,
providing a well-aligned and stable fiber optic connection. As such, one
connector adapter 812 is required for each fiber optic strand 710 of
connectorized outside fiber drop 700 (see FIGS. 7a and 7b). Adapter 812 is
any fitting suitable for coupling connector 708 of outside drop 700 to the
connector of inside drop 124 (described below). For example, adapter 812
can accommodate an SC-, ST-, or FC-type connector, and can be for single
or multiple devices. Although shown horizontally mounted in FIG. 8a,
adapter 812 can also be oriented vertically or at any other angle,
depending on the construction of connectorized outside fiber drop 120 and
connectorized inside fiber drop 124. As with connectorized terminations,
adapter 812 provides a convenient interface point that eliminates the need
for splicing.
Housing 802 of FID 800 also includes means for securely attaching FID 800
to a subscriber premises. For example, housing 802 could include external
tabs containing holes through which a fastener such as a screw could be
placed. Housing 802 could also include internal slots or knockouts that
can receive fasteners that attach FID 800 to a subscriber premises.
In light of the functions of each component of FID 800, the flowchart of
FIG. 9 illustrates how FID 800 is installed and how the pigtails of
outside drop 120 and inside drop 124 are installed in FID 800, according
to a representative embodiment. Although the flowchart describes a single
fiber optic strand routed through a fiber optic interface device, as one
skilled in the art would appreciate, the flowchart applies to the routing
of multiple fiber optic strands as well, in which case more than one fiber
optic strand wraps around the routing hardware in each direction, and more
than one adapter couples the fiber optic strands together. In addition,
the flowchart also applies to slack management within a splitter-terminal
or optical network terminal.
In step 900, the field technician installs FID 800 at a suitable location
on a building exterior, using, for example, external mounting feet of FID
800 and appropriate fasteners. The suitable location is preferably
accessible by an installer or repair person without a ladder and without
being obstructed by parts of the building or objects around the building.
Appropriate fasteners are compatible with the external mounting feet of
FID 800 and the building structure to which FID 800 is to be affixed.
Once FID 800 is mounted, in step 902, the technician removes the grommets
from ports 804 and 806, cuts a slit into each grommet to accommodate
outside drop 120 and inside drop 124, respectively, and places the
grommets back into ports 804 and 806. As described above, FIG. 8b
illustrates a representative grommet 820 and slit 822.
In step 904, the technician prepares termination hardware 808 to receive
outside drop 120 and inside drop 124. For example, in the case of a raised
slot 830 (FIG. 8c), the technician inserts one or more cable ties 832
through raised slot 830. In the case of a hose clamp 834 (FIG. 8d), the
technician loosens hose clamp 834 to a size larger than the diameters of
outside drop 120 and inside drop 124.
In step 906, the technician places outside drop 120 through the grommet in
port 804 and aligns the end of the transition fitting of outside drop 120
with a guide line 840 marked on the inside of housing 802. Guide line 840
ensures that the technician secures connectorized outside fiber drop 120
at its transition fitting, where it is most sturdy and provides the
optimal strain relief.
Once aligned properly, in step 908, the technician secures the transition
fitting of outside drop 120 with termination hardware 808. For example,
with raised slot 830, the technician tightens cable tie(s) 832 around
outside drop 120 and trims off any excess of cable tie(s) 832. As another
example, with hose clamp 834, the technician places outside drop 120
inside hose clamp 834, tightens the worm gear, and secures the hose clamp
around outside drop 120.
In step 910, the technician wraps pigtail 842 of outside drop 120 around
routing hardware 810 to store the slack of pigtail 842 at a proper bending
radius. The technician stores enough slack such that the remaining length
of pigtail 842 reaches only to adapter 812. To maintain a proper bending
radius between termination hardware 808 and routing hardware 810, FIG. 8a
shows pigtail 842 wrapping around routing hardware 810 in a clockwise
direction. However, pigtail 842 could wrap in any direction, provided the
relative distance between and configuration of termination hardware 808
and routing hardware 810 does not create an unacceptable bend.
After storing the slack of pigtail 842 around routing hardware 810, in step
912, the technician routes the remaining length of pigtail 842 to adapter
812 and inserts the connector of outside drop 120 into adapter 812.
In step 914, the technician places inside drop 124 through the grommet in
port 806 and aligns the end of the transition fitting of inside drop 124
with guide line 840. As with outside drop 120, guide line 840 ensures that
the technician secures inside drop 124 at its transition fitting, where it
is most sturdy and provides the optimal strain relief.
Once aligned properly, in step 916, the technician secures inside drop 124
with termination hardware 808, as described above for outside drop 120 in
step 908.
In step 918, the technician wraps pigtail 844 of inside drop 124 around
routing hardware 810 to store the slack of pigtail 844 at a proper bending
radius. The technician stores enough slack such that the remaining length
of pigtail 844 reaches only to adapter 812. To maintain a proper bending
radius between termination hardware 808 and routing hardware 810, FIG. 8a
shows pigtail 844 wrapping around routing hardware 810 in a
counterclockwise direction. However, pigtail 844 could wrap in any
direction, provided the relative distance between and configuration of
termination hardware 808 and routing hardware 810 does not create an
unacceptable bend.
After storing the slack of pigtail 844 around routing hardware 810, in step
920, the technician routes the remaining length of pigtail 844 to adapter
812 and inserts the connector of inside drop 124 into adapter 812.
Finally, in step 922, the technician closes the door of FID 800 and locks
and secures housing 802.
As a component of a fiber optic network system, FID 800 serves at least
four beneficial functions. First, FID 800 provides an interface point
between outside drop 120 and inside drop 124. This interface point
transitions between the different physical properties of outside drop 120
and inside drop 124. Specifically, because outside drop 120 is exposed to
exterior elements in either buried or aerial application, outside drop 120
has a heavy and inflexible sheath. In contrast, being installed inside a
building, inside drop 124 is lighter and more flexible. Thus, FID 800
transitions the considerably different constructions of outside drop 120
and inside drop 124.
A second function of FID 800 is to provide a convenient test point for
verifying service and diagnosing service problems. Because FID 800 is
mounted outside of a building, a technician can access the testing point
without disturbing the customer. Thus, for example, if a customer reports
a service problem, a technician can visit the customer's house during the
day, without requiring the customer to provide access to the house. The
technician can test optical levels at FID 800 and thereby determine if the
problem originates from within the network or within the customer's house
(e.g., with a defective optical network terminal).
FID 800 also provides a clear demarcation point between the material and
equipment owned by the fiber optic service provider and the material and
equipment owned by the customer. Once FTTH systems are implemented on a
large scale, service providers will likely favor customers' taking
ownership of the connectorized inside fiber drops and fiber optic
electronic devices. Thus, having the FID as a demarcation point will
clarify who is responsible for repairs and maintenance.
Finally, FID 800 provides a flexible maintenance point. If an outside fiber
drop or an inside fiber drop is defective or suffers damages (e.g., from a
falling tree or from errant excavations or interior demolition), a
technician can simply disconnect the inoperable drop and can replace it
with another connectorized drop without requiring any splicing. In
addition, if the outside drop suffers damage, the technician can replace
the drop without requiring customer access and without requiring any
modification or rerouting of the facilities located within the subscriber
premises, which is often a time-consuming and difficult operation.
Connectorized Inside Fiber Drop
A connectorized inside fiber drop provides fiber connectivity between a
fiber optic interface device and an optical network terminal. For example,
as shown in FIG. 1b, connectorized inside fiber drop 124 provides
communication between fiber optic interface device 122 and optical network
terminal 126. The connectorized ends eliminate the need for fiber splicing
and reduce installation and replacement costs.
FIG. 10a illustrates a connectorized inside fiber drop 1001 according to a
representative embodiment. As shown, inside drop 1001 includes a section
of sheath 1002, transition fittings 1004, pigtails 1006, fiber optic
connectors 1008, and a fiber optic strand 1010. Sheath 1002 is positioned
over a middle section of fiber optic strand 1010. The design of drop 1001
allows fiber optic strand 1010 to float freely within sheath 1002 to
prevent stress on fiber optic strand 1010 during installation and normal
operation.
Sheath 1002 preferably contains no metallic strength members, to avoid
bonding and grounding requirements at a subscriber premises. Both ends of
sheath 1002 are attached to transition fittings 1004. Transition fittings
1004 provide a structure with which to secure drop 1001 with adequate
strain relief Transition fittings 1004 also provide a structure to
transition between sheath 1002 and pigtails 1006. Pigtails 1006 attach to
transition fittings 1004 and enclose fiber optic strand 1010 from
transition fittings 1004 to the ends of fiber optic strand 1010, at which
point connectors 1008 are attached to fiber optic strand 1010 and pigtails
1006.
If a connectorized inside fiber drop contains more than one fiber optic
strand, then one set of pigtails with connectors is provided for each
fiber optic strand, as FIG. 10b shows for an inside drop 1003 having two
fiber optic strands 1013. With two fiber optic strands 1013, inside drop
1003 can support two separate lines of communication, e.g., video and
data. In addition, the separate fiber optic strands 1013 can be run to
separate optical network terminals.
Sheath 1002 provides environmental protection for fiber optic strand(s)
1010 between a fiber optic interface device and an optical network
terminal. Therefore, sheath 1002 must be appropriate for the particular
application for which inside drop 1001 is used, e.g., inside-wall,
conduit, or plenum installations. As opposed to an outside fiber optic
drop, inside drop 1001 is installed indoors and is subject to fewer
environmental hazards. Therefore, sheath 1002 is thinner and more flexible
than an outside plant sheath of an outside fiber drop. The flexibility of
sheath 1002 also enables installers to run inside drop 1001 at smaller
bending radii to accommodate the tighter confines of interior
installations. As an example of a suitable construction, sheath 1002 could
conform to the requirements of GR-409-CORE, Generic Requirements for
Premise Fiber Optical Cable, Issue May 1, 1994. GR-409-CORE is hereby
incorporated by reference in its entirety.
For an inside fiber drop 1001 having one fiber optic strand 1010, sheath
1002 is preferably fastened to the housings of the fiber optic interface
device and the optical network terminal. The fiber optic strand 1010 then
extends into the housings. For an inside fiber drop 1003 having more than
one fiber optic strand 1013, sheath 1002 is preferably fastened to the
housing of the fiber optic interface device and to a location near the
optical network terminals that the multiple fiber optic strands 1013
serve. In this manner, the individual fiber optic strands 1013 can be
routed separately to the appropriate optical network terminals.
Transition fittings 1004 are attached to outside plant sheath 1002 and
pigtails 1006 at points proximate to the ends of inside fiber drop 1001.
Transition fittings 1004 provide strain relief for inside fiber drop 1001
and for fiber optic strand 1010 as it passes from sheath 1002 to pigtails
1006. Optionally, transition fittings 1004 may include gel to further
protect fiber optic strand 1010. Transition fittings 1004 also provide a
sturdy structure that can be attached to the housings of fiber optic
interface device 122 and optical network terminal 126. For example,
transition fittings 1004 could be clamped inside a female fitting that is
integral to a housing. Or, transition fittings 1004 could be secured to a
housing using a cable tie.
Pigtails 1006 are jackets that protect individual fiber optic strands 1010
inside the housings of fiber optic interface device 122 and optical
network terminal 126. In relation to sheath 1002, pigtails 1006 are more
flexible, allowing fiber optic strands 1010 to bend at a smaller radius.
This flexibility enables installers to easily route inside drop 1001 to
connectors within the housings of fiber optic device 122 and optical
network terminal 126. The flexibility also allows installers to take up
any slack in fiber optic strands 1010 by coiling strands 1010 within a
housing. In a representative embodiment, the jacket of pigtails 1006 is
made of extruded thermal plastic of a thickness of 2.2 mm to 3.0 mm. In
addition, when more than one fiber optic strand 1010 is contained in the
connectorized inside fiber drop 1003 (as shown in FIG. 10b), pigtails 1006
are color coded to identify the same fiber optic strand on both ends of
inside drop 1003.
Connectors 1008 are compatible with the connectorized terminations provided
in fiber optic interface device 122 and optical network terminal 126.
Depending on the particular application, suitable types of connectors 1008
could include such types as SC, ST, and FC connectors. As an example,
connectors 1008 could conform to GR-326-CORE, Generic Requirements for
Single-Mode Optical Connectors and Jumper Assemblies, Issue Dec. 2, 1996
(with the clarification that connectors 1008 meet the reflectance
performance of -55 dB for all conditions).
As a whole, the transmission performance of connectorized inside fiber drop
1001 must be consistent with the requirements of the fiber optic network
system in which it operates. For example, the single-mode fiber
attenuation coefficient of inside drop 1001 should be less than 0.4 dB/km
between 1270 nm and 1350 nm, and 0.3 dB/km between 1500 nm and 1600 nm.
The attenuation should be uniformly distributed throughout the length of
inside drop 1001 such that there are no discontinuities greater than 0.1
dB for single-mode fiber at any design wavelength. In addition, all fibers
in inside drop 1001 should not exhibit point discontinuities with a
measured loss greater than 0.10 dB or a reflectance greater than -45 dB at
1310 nm or 1550 nm.
Connectorized inside fiber drop 1001 must also meet the structural and
material specifications of the fiber optic network system in which it
operates. For example, inside drop 1001 should meet all appropriate
requirements of the National Electrical Code (NEC), e.g., NEC NFPA 70. In
addition, inside drop 1001 should meet the flammability requirements of
UL-1581 when tested in accordance with the VW-1 Vertical Wire Flame
Test--All Wires Flame Test procedure.
The overall length of connectorized inside fiber drop 1001 depends upon the
typical lengths between fiber optic interface devices and optical network
terminals in a typical subscriber premises. Inside drop 1001 is designed
to be manufactured in predetermined lengths that accommodate these typical
subscriber premises configurations. For example, a typical installation
may involve an inside fiber drop penetrating an exterior wall of the
subscriber premises and entering an inside basement wall where the optical
network terminal is mounted. In this manner, an installer first estimates
the distance between a particular fiber optic interface device and the
particular location at which the optical network terminal will be mounted
inside the subscriber premises. The installer then selects an inside fiber
drop of an appropriate predetermined length.
Pigtails 1006 provide mechanical protection for the fiber optic strand
during installation and normal operation. Pigtails 1006 also provide a
means for accommodating variations in the distance between a strain relief
point (where the transition fitting is secured) and an adapter within a
fiber optic interface device or an optical network terminal. As such, the
length of pigtails 1006 depends upon the design of the fiber optic
interface device and the optical network terminal. As a minimum, a pigtail
must be long enough to reach the adapter in a fiber optic interface device
or optical network terminal, while maintaining at least the minimum
allowable bend radius of the fiber optic strand. However, pigtails 1006
must not be so long that the routing hardware of a fiber optic interface
device or optical network terminal is unable to manage the slack. Thus, in
light of these guidelines, a suitable length for pigtails 1006 could range
from, for example, 18 to 36 inches for a typical installation.
For each of the above-described FTTH system components, connectorized
terminations provide an easy, economical way to connect and disconnect
fiber optic drops and inside drops without the necessity of performing
fiber optic cable splicing operations. This advantage affords service
providers with greater flexibility in accommodating changes and additions
to existing fiber optic networks. For example, connectorized terminations
easily accommodate new subscribers, as is often the case in a new housing
development. Similarly, in the event that an outside fiber drop to the
subscriber is damaged, for example, the service provider can abandon the
existing drop and opt for the more cost-effective repair of installing a
new fiber optic drop from the fiber optic splitter-terminal to the fiber
optic interface device.
At all locations where fiber optic strands penetrate housings, cases, or
shells, strain relief orifices or fittings well known in the art could be
installed to reduce the possibility of damaging the fiber optic strands.
Other devices well known in the art, e.g., splice trays, could also be
incorporated into the fiber optic deployment systems to provide strain
relief and sheath management.
In describing representative embodiments of the present invention, the
specification may have presented the method and/or process of the present
invention as a particular sequence of steps. However, to the extent that
the method or process does not rely on the particular order of steps set
forth herein, the method or process should not be limited to the
particular sequence of steps described. As one of ordinary skill in the
art would appreciate, other sequences of steps may be possible. Therefore,
the particular order of the steps set forth in the specification should
not be construed as limitations on the claims. In addition, the claims
directed to the method and/or process of the present invention should not
be limited to the performance of their steps in the order written, unless
that order is explicitly described as required by the description of the
process in the specification. Otherwise, one skilled in the art can
readily appreciate that the sequences may be varied and still remain
within the spirit and scope of the present invention.
The foregoing disclosure of embodiments of the present invention has been
presented for purposes of illustration and description. It is not intended
to be exhaustive or to limit the invention to the precise forms disclosed.
Many variations and modifications of the embodiments described herein will
be obvious to one of ordinary skill in the art in light of the above
disclosure. The scope of the invention is to be defined only by the claims
appended hereto, and by their equivalents.
* * * * *
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