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| United States Patent |
6,616,344
|
|
Van Deventer
|
September 9, 2003
|
Interconnection system for optical networks
Abstract
An optical interconnection system for the realization of network elements
in optical networks comprises a set of functional optical circuit modules
(15) and an interconnection panel (10). The panel is provided with a row
of module positions (13.1, 13.2, 14.1, . . . , 14.N) suitable for plugging
in circuit modules (15), and with a pair of optical (1:N) splitters
(16,17), each pair of corresponding ports of which (16A/17A, 16.1/17.1, .
. . , 16.N/17.N) are interconnectable to a pair of a number of pairs of
connection ports (11, 12.1, . . . , 12.N) through a module position and a
circuit module plugged into that position. The set of circuit modules
comprises circuit modules with functions for signal interconnection, for
signal transport direction reversal, and for signal manipulation. A number
of panels can be coupled together for purposes of, inter alia, expansion
and/or protection.
| Inventors:
|
Van Deventer; Mattijs Oskar (Leidschendam, NL)
|
| Assignee:
|
Koninklijke KPN N.V. (The Hauge, NL)
|
| Appl. No.:
|
486333 |
| Filed:
|
February 24, 2000 |
| PCT Filed:
|
September 4, 1998
|
| PCT NO:
|
PCT/EP98/05723
|
| PCT PUB.NO.:
|
WO99/13656 |
| PCT PUB. Date:
|
March 18, 1999 |
Foreign Application Priority Data
| Current U.S. Class: |
385/88; 385/89; 385/90; 385/135; 398/164 |
| Intern'l Class: |
G02B 006/36 |
| Field of Search: |
359/163
385/89-90,135,88
|
References Cited [Referenced By]
U.S. Patent Documents
| 4870637 | Sep., 1989 | Follett et al. | 359/135.
|
| 5636047 | Jun., 1997 | Lagoutte et al. | 359/124.
|
| Foreign Patent Documents |
| 0 316 259 | May., 1989 | EP.
| |
| 0 511 779 | Nov., 1992 | EP.
| |
| 1006963 | Jun., 1997 | NL.
| |
| WO 95/20772 | Aug., 1995 | WO.
| |
Other References
Russell C. Stanley; "Fiber Optic Local-Area Networks"; pp. 390-398;
Proceedings of the National Communications Forum; Sep. 30, 1988, No. 1.
Akira Himeno et al; "Experimental Optical Switching System Using
Space-Division Matrix Switches Gated by Laser Diodes"; pp. 0928-0932; 1988
IEEE; Nov. 20, 1988.
M.J. Goodwin; "Optical Interconnect Technologies For High Performance
Electronic Processor Systems"; 1993; pp. 85-90; GEC Journal of Research,
vol. 10, No. 2.
I.M. Burnett et al; "Future Switching Requirements for Telecommunications
Networks: Challenges for Photonics"; 1993; pp. 38-41; ECOC.
A. Herzberger et al; "Phase--A Comprehensive System For Synchronous
Networks"; pp. 4-17; Philips Telecommunication Review; vol. 51, No. 2.
|
Primary Examiner: Negash; Kinfe-Michael
Attorney, Agent or Firm: Frishauf, Holtz, Goodman & Chick, P.C.
Claims
What is claimed is:
1. An optical interconnection system for realizing network elements in
optical networks, comprising:
a plurality of functional optical circuit modules;
an optical interconnection member including a pair of optical beam
splitting means, having a pair of main ports and a plurality of pairs of
subsidiary ports, module positions, each of which includes a pair of
optical receptacles connected to a pair of subsidiary ports of the pair of
optical beam splitting means for plugging in optical circuit modules from
the set of circuit modules,
at least one further module position being connected to the pair of main
ports, and
a plurality of pairs of optical connection ports for connecting external
optical signal transport lines, and each module position includes a
further pair of optical receptacles, separate pairs of said connection
ports having separate optical connections to the further pairs of optical
receptacles of separate module positions.
2. An optical interconnection system according to claim 1, wherein the
module positions include first and second main module positions, each
provided with first and second pairs of optical receptacles, the first
pair of optical receptacles of the first main module position having
optical connections to the first pair of optical receptacles of the second
main module position, the pair of main connection ports having optical
connections to the second pair of optical receptacles of the first main
module position, and the pair of main ports of the optical splitting means
having optical connections to the second pair of optical receptacles of
the second main module position.
3. An optical interconnection system according to claim 1, wherein the
optical interconnection system comprises a further interconnection member
of a same type as the first-mentioned interconnection member, and wherein
a pair of subsidiary connection ports of the first-mentioned
interconnection member has optical interconnections with the pair of main
connection ports of the further interconnection member.
4. An optical interconnection system according to claim 1, wherein the
plurality of circuit modules comprises:
a first group of circuit modules having a first type of signal circuit
including a first optical interconnection in a first signal transport
direction, and a second optical interconnection in a second signal
transport direction, and
a second group of circuit modules having a second type of signal circuit
with a third optical interconnection which transfers the first signal
transport direction in the second signal transport direction.
5. An optical interconnection system according to claim 4, wherein an
optical amplifier is incorporated in at least one of the interconnections
of the signal circuits on the circuit modules.
6. An optical interconnection system according to claim 4, wherein an
optical filter is incorporated in at least one of the interconnections of
the signal circuits on the circuit modules.
7. An optical interconnection system according to claim 4, wherein an
optical transponder is incorporated in at least one of the
interconnections of the signal circuits on the circuit modules.
8. An optical interconnection system according to one of claims 1 to 7,
wherein the optical interconnection system comprises M interconnection
members (PN.sub.1 to PNM.sub.M), with M.gtoreq.2, of a same type as the
first-mentioned interconnection member;
each interconnection member includes a back panel onto which the row of
module positions is fitted;
the M back panels being incorporated into a frame in positions parallel to
each other, in which the module positions of the M interconnection panels
form a matrix ({r,k}) of module positions with M rows and N+2 columns, and
the set of circuit modules comprises a first subset of single circuit
modules, and a second subset of multiple circuit modules, in which a
single circuit module can be plugged into any one of the module positions
of the matrix, and in which a multiple circuit module can be plugged into
two or more, with a maximum of M, module positions within any one column
of the matrix.
9. An optical interconnection system according to claim 8, wherein the
first and the second groups of circuit modules form part of the first
subset of circuit modules.
10. An optical interconnection system according to claim 8, wherein the
circuit modules of the second subset of multiple circuit modules include
two or more, with a maximum of M, signal circuits of a same type as the
signal circuits of the first group of circuit modules, said two or more
signal circuits being coupled together by means of optical switching
devices.
11. An optical interconnection system according to claim 8, wherein the
second subset comprises:
a first group of multiple circuit modules which includes two signal
circuits coupled by means of optical cross-bar switches, and
a second group of multiple circuit modules which include three signal
circuits coupled by means of an optical matrix switch.
12. An optical interconnection system according to claim 2, wherein the
optical interconnection system comprises a further interconnection member
of a same type as the first-mentioned interconnection member, and wherein
a pair of subsidiary connection ports of the first-mentioned
interconnection member has optical interconnections with the pair of main
connection ports of the further interconnection member.
13. An optical interconnection system according to claim 2, wherein the
plurality of circuit modules comprises:
a first group of circuit modules having a first type of signal circuit
including a first optical interconnection in a first signal transport
direction, and a second optical interconnection in a second signal
transport direction, and
a second group of circuit modules having a second type of signal circuit
with a third optical interconnection which transfers the first signal
transport direction in the second signal transport direction.
14. An optical interconnection system according to claim 3, wherein the
plurality of circuit modules comprises:
a first group of circuit modules having a first type of signal circuit
including a first optical interconnection in a first signal transport
direction, and a second optical interconnection in a second signal
transport direction, and
a second group of circuit modules having a second type of signal circuit
with a third optical interconnection which transfers the first signal
transport direction in the second signal transport direction.
15. An optical interconnection system according to claim 5, wherein an
optical filter is incorporated in at least one of the interconnections of
the signal circuits on the circuit modules.
16. An optical interconnection system according to claim 5, wherein an
optical transponder is incorporated in at least one of the
interconnections of the signal circuits on the circuit modules.
17. An optical interconnection system according to claim 6, wherein an
optical transponder is incorporated in at least one of the
interconnections of the signal circuits on the circuit modules.
18. An optical interconnection system according to claim 9, wherein the
circuit modules of the second subset of multiple circuit modules include
two or more, with a maximum of M, signal circuits of a same type as the
signal circuits of the first group of circuit modules, said two or more
signal circuits being coupled together by means of optical switching
devices.
19. An optical interconnection system according to claim 9, wherein the
second subset comprises:
a first group of multiple circuit modules which includes two signal
circuits coupled by means of optical cross-bar switches, and
a second group of multiple circuit modules which includes three signal
circuits coupled by means of an optical matrix switch.
20. An optical interconnection system according to claim 10, wherein the
second subset comprises:
a first group of multiple circuit modules which includes two signal
circuits coupled by means of optical cross-bar switches, and
a second group of multiple circuit modules which includes three signal
circuits coupled by means of an optical matrix switch.
21. An optical interconnection system according to one of claims 12 to 17,
wherein the optical interconnection system comprises M interconnection
members (PN.sub.1 to PNM.sub.M), with M.gtoreq.2, of a same type as the
first-mentioned interconnection member;
each interconnection member includes a back panel onto which the row of
module positions is fitted;
the M back panels being incorporated into a frame in positions parallel to
each other, in which the module positions of the M interconnection panels
form a matrix ({r,k}) of module positions with M rows and N+2 columns, and
the set of circuit modules comprises a first subset of single circuit
modules, and a second subset of multiple circuit modules, in which a
single circuit module can be plugged into any one of the module positions
of the matrix, and in which a multiple circuit module can be plugged into
two or more, with a maximum of M, module positions within any one column
of the matrix.
Description
BACKGROUND OF THE INVENTION
The invention is in the field of optical networks. More in particular, it
concerns an optical interconnection system for the realization of network
elements in such networks, provided with one or more identical
interconnection members.
Telecommunication techniques increasingly use optical signal transmission
through optical fibre links. Various types of optical networks, not only
single point-to-point connections, bit also tree-shaped, star-shaped, or
ring-shaped interconnect structures using passive and/or active network
components, have already been developed for this purpose, or are under
development. Furthermore, optical networks are increasingly being expanded
with protection configurations. Such diversity in network structures
requires a large variety of network elements. Such network elements can
vary from such relatively simple elements as optical amplifiers, filters,
and transponders, and passive optical splitters, in some cases combined
with optical amplifiers, to more complex elements such as optical add/drop
multiplexers (AODMs) and optical cross-connects (OXCs). For reasons of
economy, both manufacturers/suppliers and network operators of optical
networks find themselves facing the technical problem of realizing the
largest possible variety of network elements using the smallest possible
number of equipment components, with which in addition, a high degree of
flexibility regarding adaptation according to function and capacity of the
network elements is to be achieved. In reference [1], and more in
particular in Section 4 of said reference, a problem of this type is
analyzed for Synchronous Digital Hierarchy (SDH) networks. The conclusion
of said analysis is that the number of types of installation racks for the
various equipment components can be minimized only if a rack structure is
used with a uniform back panel; and that a uniform back panel can be used
thanks to the application of a signal bus into which, inter alia, so-call
aggregate and tributary interfaces can be plugged to realize signal
connections in the various transmit and receive directions of the network
elements in question. A rack structure with a back panel provided with a
signal bus of this type not only allows for flexible adaptation to meet
the current need for capacity of a network element, it also enables
flexible upgrading to take place to more complicated network elements,
e.g. from an ADM (add/drop multiplexer) to an LXC (local cross-connect).
In principle, a signal bus rack structure of this type can also be
realized in the optical domain. Reference [2] for instance, describes a
possible development path to a `future node` based on an optical bus
architecture, which may be ring-shaped. An optical bus of this type
comprises a back panel with a number of parallel optical wave guides, on
which, analogous to an electronic back panel, card-type modules fitted
with optical circuits, hereinafter referred to as optical circuit modules,
can be optically coupled. Typical problems that occur when optical power
is drawn from optical conductors can be solved, e.g. by the application of
optical fibre amplifiers in the back panel between the connection points.
For the coupling of the optical circuit modules with each of the parallel
wave guides in the Zoptical bus a technique is indicated which is known
for example from reference [3]. In this reference, an optical bus is
described consisting of a number of parallel optical fibres, D-shaped in
section, in a back panel, to which card-type circuit modules are coupled
with each of the optical fibres through specific connector blocks.
The application of a bus principle offers many advantages in the electrical
domain. The application in the optical domain, however, is not as simple,
since a signal bus is by principle a non-directional signal transport
medium, whereas an optical wave guide, such as an optical fibre, is a
directional signal transport medium. In addition, signal communication
through a signal bus requires an additional bus protocol, calling for
protocol conversions that can take place only in the electrical domain.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide an optical interconnection
system enabling a flexible realization of network elements. In doing so,
it avoids the application of an optical signal bus, while still enabling a
rack structure to be used with one or more identical interconnection
members. It uses the insight that network elements in optical networks in
most cases include a signal splitting function, and that a suitable
manipulation of the optical signals is possible within the optical
connections to and from the splitting means used, e.g. amplification,
filtering, or regeneration.
An optical interconnection system for the realization of network elements
in optical networks according to the introductory part of claim 1, and for
the definition of which reference [3] has been used, according to the
invention has the characteristic features according to claim 1.
Although in principle, optical fibre connections can be used
bidirectionally, the risk of signal interference as a result of, inter
alia, cross-talk will increase, and the bidirectional manipulation of
optical signals is in most cases unfeasible, so signal traffic in either
direction is preferably conducted through physically separate optical
signal connections. In a preferred embodiment, the interconnection system
according to the invention therefore has the characteristic features
according to claim 2.
In order to offer an extra possibility for manipulation at the main ports
of the optical signal splitters, a further preferred embodiment has the
characteristic features according to claim 3.
The optical interconnection system according to the invention can also
comprise more than one interconnection member. These members can be
coupled together in various ways. According to a first variant of a
coupling of this type, this can be implemented by connecting a pair of
subsidiary ports of a member to the pair of main connection ports of a
further member. For this purpose, a further preferred embodiment has the
characteristic features according to claim 4. The coupling can also be
effected by providing the member with a back panel onto which the row of
module positions is fitted, in combination with a suitable positioning of
the back panels of a number of interconnection members relative to each
other in a rack or frame, and a design of the circuit modules that is
adapted to this positioning. For this purpose, yet a further preferred
embodiment has the characteristic features of claim 9.
Further preferred embodiments have been summarized in further subclaims.
Reference [4] discloses an optical interconnection apparatus for
interconnecting via a back panel, using multiple fibre connectors, a
number of printed circuit boards fitted with electrical wiring. These
printed circuit boards are fitted with E/O and O/E converters that can be
coupled to each other by means of multiple optical edge connectors
connecting to optical fibre connectors located in grooves in the back
panel, and also to external optical lines through separate optical
connector points. However, there are no optical splitting devices in the
back panel, and the purpose of the invention is not known from this.
Reference [5], which was not published in time, discloses an
interconnection apparatus that provides optical and/or electrical signal
interconnections of a number of input ports to a number of output ports
through a segmentable signal bus. In this case an interconnection panel is
used with a row of module positions for plugging in circuit modules, in
combination with a set of circuit modules fitted with signal circuits with
different bus functions. The signal bus can be composed of bus parts
formed by permanent signal connections between subsequent modules and by
the signal circuits of circuit modules plugged into the module positions.
The interconnection system according to the invention offers a relatively
economical basic configuration for the implementation of a wide variety of
network elements for various types of optical networks, which moreover can
be expanded in a modular fashion without interruption of service, even to
100% of the optical fibre capacity of the connected optical fibre links.
References
[1] A. Herzberger et al., "PHASE--A comprehensive system for synchronous
networks", Philips Telecommunication Review, Vol. 51, No. 2, pp. 4-17;
[2] I. M. Burnett and D. W. Smith, "Future switching requirements for
telecommunication networks: Challenges for photonics", ECOC '93(?),
TuP3.1, pp. 38-44;
[3] WO 95/20772;
[4] EP-A-0511779;
[5] Dutch patent application by applicant: application no. 1006239,
application date Jun. 5, 1997.
All references are deemed to be incorporated in the present application.
SHORT DESCRIPTION OF THE DRAWING
The invention will be explained in greater detail by means of a description
of an exemplary embodiment, with reference to a drawing containing the
following figures:
FIG. 1 showing a schematic diagram of an optical interconnection system
according to the invention;
FIG. 2 showing in parts (a)-(k) schematic diagrams of ten types of circuit
modules for an interconnection system according to FIG. 1;
FIG. 3A showing in parts (a)-(e) five symbols for use in FIG. 3B, and in
figures FIGS. 7-9;
FIG. 3B showing in parts (a)-(j) schematic diagrams of nine applications of
the interconnection system according to FIG. 1 using the circuit modules
shown in FIG. 2;
FIG. 4 showing a first embodiment of a coupling between interconnection
panels;
FIG. 5 showing a schematic diagram of a frame with interconnection panels
which can be coupled by means of multiple circuit modules;
FIG. 6 showing in parts (a) and (b) two further symbols for use in figures
FIGS. 7, 8, and 9;
FIG. 7 showing schematic diagrams in parts (a)-(c) of a first group and in
parts (d)-(f) of a second group of multiple circuit modules;
FIG. 8 showing in parts (a)-(g) schematic diagrams of seven applications of
an interconnection system provided with a frame according to FIG. 5;
FIG. 9 showing in parts (a)-(c) schematic diagrams of three applications of
an interconnection system provided with a frame according to FIG. 5.
DESCRIPTION OF AN EXEMPLARY EMBODIMENT
FIG. 1 shows a schematic diagram of a first embodiment of an
interconnection system according to the invention. It comprises an
interconnection member 10, which may be in the form of a panel,
hereinafter referred to as interconnection panel. Interconnection panel 10
is subdivided into a connection panel 10.1 and a back panel 10.2. The
connection panel is provided with a pair of main connection ports 11 and N
pairs (N=1, 2, . . . ) of subsidiary ports 12.1-12.N. Each pair of
subsidiary ports has an input port p and an output port q, which have been
configured for the connection of incoming and outgoing optical signal
transport lines. The back panel 10.2 is provided with N+2 module
positions, i.e. two main module positions 13.1 and 13.2, and N subsidiary
module positions 14.1-14.N. Each of the N+2 module positions is configured
for accepting plug-in optical circuit modules 15. For this purpose, a
circuit module 15 is provided with four optical connectors m1-m4, and each
module position is provided with four optical receptacles f1-f4. In
addition, the back panel 10.2 is provided with optical beam splitter
provisions, in this case two optical signal splitters 16 and 17. Each of
the two signal splitters has a main port, 16A and 17A, and N subsidiary
ports, 16.1-16.N and 17.1-17.N, respectively. The ports of the optical
signal splitters have permanent optical signal connections to the module
positions, as follows. The main ports 16A and 17A are connected to the
receptacles f4 and f3 of the main module position 13.2, respectively; the
first subsidiary ports 16.1 and 17.1 are connected to the receptacles f1
and f2 of the first subsidiary module position 14.1, respectively; the
second subsidiary ports 16.2 and 17.2 are connected to the receptacles f1
and f2 of the second subsidiary module position 14.2, respectively; etc.;
and finally, the Nth subsidiary ports 16.N and 17.N are connected to the
receptacles f1 and f2 of the Nth subsidiary module position 14.N,
respectively. The pairs of connection ports on the connection panel also
have permanent optical signal connections to the module positions, as
follows. The connection ports p and q of the pairs of main and subsidiary
connection ports 11 and 12.1-12.N are connected to the receptacles f3 and
f4 of the main and subsidiary module positions 13.1 and 14.1-14.N,
respectively. Of the module positions, only the two main module positions
13.1 and 13.2 are interconnected, as follows. The receptacles f1 and f2 of
the first main module position 13.1 have permanent optical signal
connections 18 and 19 with the receptacles f2 and f1 of the second main
module position 13.2, respectively.
The signal splitters 16 and 17 preferably are optical (1:N) power
splitters, but can also be of another type, e.g. WDM (de)multiplexers or
WDM routers. The optical power splitters preferably are selected
symmetrically, the optical power in the splitting direction being evenly
distributed among the ports. However, in principle they can also be
asymmetrical, consisting of e.g. N power splitters switched in series, in
which any lack of optical power symmetry can be compensated by means of
optical amplification at suitably selected module positions.
The interconnection system can be used to implement semi-permanent optical
signal interconnections between the pair of main connection ports 11 and
the pairs of subsidiary connection ports 12.1-12.N, but also between the
pairs of main connection ports, depending on the circuit modules plugged
into the module positions. A first signal transport direction from a main
connection port via the signal splitter 16 in the direction of one or more
of the subsidiary connection ports has been indicated with arrows s. A
second signal transport direction from one or more subsidiary connection
ports via the signal splitter 17 in the direction of a main connection
port, i.e. in the opposite direction, has been indicated by arrows t. For
the purpose of implementing the semi-permanent signal interconnections,
the interconnection system comprises a set of circuit modules. This set is
subdivided into two subsets, one subset of single circuit modules, and one
subset of multiple circuit modules. The subset of multiple circuit modules
will be discussed further on. The circuit module 15 shown in FIG. 1 is a
single circuit module, provided with an optical circuit 20, which in
addition to a signal-conducting function, can also have a
signal-manipulating function (see below). The subset of single circuit
modules in turn is subdivided into two groups. The circuit modules of the
first group are such that the optical circuit 20 provides optical
interconnections between the connectors m3 and m2 in the first signal
transport direction (arrows s), and between the connectors m1 and m4 in
the second signal transport direction (arrows t). Of the circuit modules
of the second group, the optical circuit 20 provides an optical
interconnection between the connectors m1 and m2, as a result of which the
signal transport direction is in fact reversed from the first into the
second, or from the second into the first signal transport direction. FIG.
2 shows in parts (a)-(f) six different types of circuit modules of the
first group, and in parts (g)-(k) four different types of the second
group. Part (a) shows a circuit module with interconnections 21 and 22 in
both signal transport directions: type designation D.sub.0 ; part (b) also
shows a circuit module with an interconnect function in both directions,
in which interconnection 22 incorporates an optical wavelength filter 23:
type designation D.sub.1 ; the circuit module of part (c) is identical to
that of part (b), in which in addition a transponder 24 has been
incorporated in the interconnection 21: type designation D.sub.2. Parts
(d), (e), and (f) also show circuit modules with an interconnect function
in both directions, in which an optical amplifier 25 has been incorporated
in the interconnection 21, or in the interconnection 22, or in both
interconnections: type designations A.sub.2, A.sub.3, and A.sub.4,
respectively. Part (g) shows a circuit module with an interconnection 26
which reverses the signal transport direction: type designation T.sub.0 ;
the parts (h), (j), and (k) also show circuit modules with a similar
interconnection 26, in which however, either an optical filter 23, or a
combination of an optical filter 23 and a transponder 24 in series, or an
optical amplifier 25 has been incorporated: type designations T.sub.1,
T.sub.2, and A.sub.1, respectively.
Of course, the connection ports for the incoming and outgoing signal
transport lines can also be implemented on two different connection
panels. In principle, the module positions can also be duplicated, i.e.
N+2 for each signal transport direction, and implemented using only two
receptacles and associated circuit modules instead of four. However, an
interconnection panel of this type is less compact, and a relatively
simple reversal of the signal transport direction as by means of the
single circuit modules of the second group is impossible. In addition, the
connection panel need not form a whole with, or be located in the same
plane as, the back panel. Also, the module positions can be located along
an edge on one side of a back panel, which can be rectangular in shape, in
a manner similar to that described in reference [4], with the connection
points being located as optical connector points along an edge of an
opposite side of the rectangle, and the optical signal splitters and their
associated optical connections with the module positions and the
connection points being located on or in the back panel. In this context,
the signal splitters and the associated optical connections can be
discrete components, but they can also be entirely or partly implemented
in integrated form. The circuit modules, for example, have been
implemented as a card or printed circuit board provided with edge
connectors for optical signal connections according to a technique known
per se, as described for example in the reference [4] mentioned above.
Hereinafter a number of network elements will be described schematically
for N=3, which network elements can be implemented using an
interconnection system comprising an interconnection panel 10 according to
FIG. 1 and a set of circuit modules as shown in FIG. 2. In this context,
reference is made to FIG. 3A and FIG. 3B. FIG. 3A shows in parts (a)-(e)
five drawing symbols which have been used in FIG. 3B to indicate equipment
components. Part (a) shows the symbol for an optical (1:3) splitter, which
is used in FIG. 3B to indicate the signal splitters 16 and 17 of FIG. 1
for N=3. Parts (b), (c), and (d) in turn show the symbols of an optical
amplifier, an optical filter, and a transponder, which are used in FIG. 3B
to indicate the optical amplifiers 25, the optical filters 23, and the
transponders 24 on the circuit modules shown in FIG. 2. Part (e) shows a
symbolical representation of interconnection panel 10 of FIG. 1, reduced
to a matrix of one row with five positions represented by boxes 1-5, which
indicate the module positions for N=3, i.e. the main module positions 13.1
and 13.2, and the subsidiary module positions 14.1, 14.2, and 14.3.
Placing one of the type designations of the circuit modules of FIG. 2 in
one of the boxes indicates that the circuit module in question has been
plugged into the module position corresponding with the box. For example,
the designation A.sub.4 in the first box means that a circuit module as
shown in part (f) of FIG. 2 has been plugged into the first main module
position 13.1. Using the symbols of FIG. 3A, the parts (a)-(j) of FIG. 3B
show nine examples of network elements (NE), each part showing on the left
a schematic diagram of the optical circuit of an NE, and on the right, the
matrix representation of an implementation using the interconnection
system described. In addition, signal transport directions have been
indicated in the optical circuits on the left (arrows s and t). Parts (a)
and (b) show network elements that consist of a preamplifier and a booster
amplifier, respectively. In these cases, only the two main module
positions of the connection panel are used. Part (c) shows as network
element an in-line amplifier. Parts (d) and (e) show as network element a
node with a splitter function, without amplification for a passive optical
network (PON), and with amplification for a Super PON, respectively. Parts
(f) and (g) show as network element an optical terminal multiplexer (OTM),
without and with transponders, respectively. Parts (h) and (j) show as
network element an optical add-drop multiplexer (OADM), without and with
transponders, respectively.
Two or more interconnection panels can be coupled in different ways. A
first embodiment of this, called `frame extension`, is shown schematically
in FIG. 4 in a manner similar to that of FIG. 3B. Said coupling is
effected between two interconnection panels 40 and 41 (of a same type as
interconnection panel 10) by means of optical interconnections 42 and 43
between a pair of subsidiary connection ports (such as the pair 14.3 in
FIG. 1) of the connection panel 40 and the pair of main connection ports
(such as 13.1 in FIG. 1) of the interconnection panel 41. The use of such
a `frame extension` enables, for example for a Super PON, a network
element with a combined (1:N.sup.2) amplifier/splitter function to be
created with only N+1 interconnection panels.
A second embodiment for a coupling of two or more interconnection panels is
possible by providing the circuit modules with a shape and signal circuit
such that they can form optical interconnections between module positions
of the various interconnection panels. FIG. 5 shows a schematic diagram of
an exemplary embodiment of this. For this purpose, the interconnection
apparatus comprises a frame 50 into which M (M=2, 3, . . . )
interconnection panels PN.sub.1 -PN.sub.M (of a same type as
interconnection panel 10) have been fitted. The M interconnection panels
PN.sub.1 -PN.sub.M in the frame form a multiple interconnection panel MPN.
In the figure, the frame 50 has been indicated, by way of example and for
the sake of simplicity, as a line frame. Each interconnection panel has a
row of N+2 module positions (with N.gtoreq.2), i.e. two main module
positions 51.1 and 51.2, and N subsidiary module positions 52.1-52.N. The
M interconnection panels have been incorporated into the frame in
positions that are fixed relative to each other, in which the module
positions of the M interconnection panels form a, preferably rectangular,
matrix (r,k) with M rows (r=1, . . . , M) and N+2 columns (k=1, . . . ,
N+2). The figure shows each panel PN.sub.1 -PN.sub.M in a form reduced to
the row of module positions, in a manner similar to that of part (e) of
FIG. 3A for M=1. At each separate module position (r,k) of the matrix, a
circuit module of the subset of single circuit modules, such as of the
types shown in FIG. 2, can be plugged in, as described above. A single
circuit module has only a single foursome of optical connectors, m1-m4. A
multiple circuit module 53 is provided with more than one foursome of such
optical connectors. A double circuit module is provided with two foursomes
54.1 and 54.2, a triple module has three of such foursomes, etc.; and an
M-fold module has M foursomes 54.1-54.M. A multiple circuit module 53 is
provided with an optical control circuit 55 which, in addition to
signal-conducting and signal-manipulating functions, can have a switching
function. A multiple circuit module 53 can be plugged in at two or more
circuit positions simultaneously within one column of the matrix. With
reference to the figures FIGS. 7, 8, and 9, examples of this will be
described for M=2 and M=3. In addition to FIG. 3A, FIG. 6 shows four
further symbols which are used in this context to indicate a number of
other equipment components. Part (a) concerns an optical cross-bar switch
60 with two switch positions: a first switch position S1 (continuous
lines), in which a first and a second input port 61.1 and 61.2 are
connected to a first and a second output port 62.1 and 62.2, respectively;
and a second switch position S2 (broken lines), in which the first and the
second input port 61.1 and 61.2 are connected to the second and the first
output port 62.2 and 62.1, respectively. Part (b) shows the symbol for a
(1:2) switch 60', which corresponds with the cross-bar switch 60 of part
(a), but the output port 62.2 of which is not used (and therefore has been
omitted from the figure). Part (c) shows a symbol of a cross-bar switch
60", which corresponds with the switch 60 of part (a), of which the input
and output ports 61.1/61.2 and 62.1/62.2 have been arranged differently.
Part (d) concerns an optical matrix switch 63, in this case a 6.times.6
optical space switch with six input ports and six output ports. (Note: In
the symbol for the optical matrix switch, the input and output ports are
shown as twelve ports, grouped in three groups of four; another group
layout of three, six, and three is also used, as in parts (b) and (c) of
FIG. 9.) FIG. 7 shows in parts (a), (b), and (c) three double, and in
parts (d), (e), and (f) three triple circuit modules. The double circuit
module of part (a) with type designation P.sub.0 is in fact a composite of
two single circuit modules of type D.sub.0 (see part (a) of FIG. 2), the
interconnections 71 and 72, and 71' and 72' of which have been coupled by
means of two cross-bar switches, 73 and 74 respectively (both indicated by
the symbol as shown in part (a) of FIG. 6). The coupling is such that, if
both switches 73 and 74 are set to switch position S1, the circuit module
of type P.sub.0 will act as two separate single circuit modules of type
D.sub.0 ; whereas with both switches set to the second switch position S2,
the interconnections 71 and 72 are connected to the interconnections 71'
and 72', respectively. Parts (b) and (c) show double circuit modules with
the type designations P.sub.1, and P.sub.2, respectively, which are, in a
manner identical to that of the double circuit module of type P.sub.0, a
composite of two single circuit modules, of types D.sub.1 and D.sub.2,
respectively (see parts (b) and (c) of FIG. 2). Part (d) shows a triple
circuit module with type designation X.sub.0, which is in fact a composite
of three single circuit modules of type D.sub.0, the interconnections of
which are coupled via a 6.times.6 matrix switch 75 with six input ports
and six output ports. The parts (e) and (f) show triple circuit modules
with type designations X.sub.1 and X.sub.2, respectively, which are, in a
manner identical to that of the double circuit module of type X.sub.0, a
composite of three single circuit modules, of types D.sub.1 and D.sub.2,
respectively (see parts (b) and (c) of FIG. 2).
The types of double circuit modules shown are eminently suitable for use in
protection configurations. Seven examples of this are shown in parts
(a)-(g) of FIG. 8. In a similar manner as in FIG. 3B, each part shows, on
the left, a schematic diagram of the optical circuit of an NE, and to the
right, the matrix representation of a realization using a multiple
interconnection panel MPN for M=2 and M=3. The multiple interconnection
panel MPN is represented symbolically by a matrix of (2.times.5) boxes
which represent the module positions of the two interconnection panels PN1
and PN2 in the multiple interconnection panel MPN. The parts (a)-(e) show
protection configurations in which a double circuit module of type P.sub.0
is used in the second column of the matrix, i.e. at the second module
position (13.2 in FIG. 1) of both panels, PN1 and PN2. Part (a) shows an
NE with a protection configuration, in this case a (1+1) type protection,
for a pair of bidirectional optical connections. Part (b) shows an NE with
a protection configuration, in this case a (1:1) type protection, for two
pairs of bidirectional optical connections. By plugging in further circuit
modules of type D.sub.0 at the unoccupied module positions, protection
configurations are obtained for the NE shown in part (e) of FIG. 3B. In a
similar manner, part (c) and part (d) show an NE with protection
configuration, in this case a (1+1) type protection and a (1:1) type
protection, respectively, for an optical multiplexing section (OMS) like
the OTM shown in part (g) of FIG. 3B. Part (e) shows an NE with a
protection configuration for the OADM shown in part (j) of FIG. 3B. For
protection purposes, instead of the pair of main module positions in the
second column of the matrix, two subsidiary module positions in the same
column of the matrix can also be used, enabling forms of so-called optical
channel protection (OCH protection) to be realized. Part (f) shows an NE
with OCH protection for an OTM (see part (g) of FIG. 3B), and part (g)
shows an NE with OCH protection for an OADM (see part (j) of FIG. 3B).
The triple circuit module types are suitable for realizing NEs with an
optical cross-connect (OXC) function. Three examples of this are shown in
parts (a)-(c) of FIG. 9. Each part shows, on the left, a schematic diagram
of the optical circuit of an NE with such a function, while to the right,
the matrix representation of a realization using the multiple
interconnection panel MPN for M=3 and N=3 is shown. Part (a) shows an NE
with an optical fibre router function with amplification, in fact the
simplest form of an OXC (three pairs of input and output ports of the
6.times.6 matrix switch have been interconnected). For this purpose, the
triple circuit module of type X.sub.0 has been placed in the second column
of the matrix, in combination with three single circuit modules of type
T.sub.0 in the third column, and circuit modules of type A.sub.4 in the
first column. Parts (b) and (c) show an NE for an OXC, without and with
transponders (TR), respectively. For this purpose, a triple circuit module
has been placed in both the third and the fourth column of the matrix, of
type X.sub.1 in part (b), and of type X.sub.2 in part (c), while in both
configurations, the first column has been filled with circuit modules of
type A.sub.4, and the second column with circuit modules of type D.sub.0.
In the above, only optical signal connections and interconnection
possibilities of the interconnection system have been shown in the
descriptions of the exemplary embodiments. Any necessary electrical wiring
for power supply purposes, e.g. to amplifiers and transponders, and for
control purposes, e.g. to optical switches, is implicitly deemed present,
realized using techniques known per se, and consequently does not form
part of the subject invention. In addition, the circuit modules may be
provided with circuits for management purposes, e.g. for carrying out
power measurements for purposes of error detection or power control.
The filters used on the circuit modules preferably are tuneable filters.
The use of transponders allows for the possibility of wavelength
conversion and/or 3R regeneration.
Of course, the range of possible types is not exhausted with the types
shown in FIG. 2 and in FIG. 7. Also, the optical splitters 16 and 17 on
the interconnection panel 10 can be used in the same signal transport
direction. For example, by providing a circuit module with a (1:2)
splitter function and placing it in one of the main module positions, an
interconnection panel can be set up as a (1:2N) splitter.
* * * * *
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