Optical fiber distribution module for holding an optical...

Optical waveguides – Accessories

Reexamination Certificate

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Reexamination Certificate

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06256443

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical fiber distribution module for connecting or exchanging connections of multi-core optical fibers, a single-fiber optical cord and a set-type optical fiber cords, and an optical fiber distribution system for managing operating information of a network connecting outdoor optical facilities with optical communication equipment in a telecommunication equipment center so that the system may be operated at its peak efficiency.
2. Description of the Related Art
Conventional optical fiber distribution module has a connection board with an array of connector adaptors, and a holding board for storing those fiber cords with connector plugs that are not in use, and connections or switching requires the following three basic operations.
(1) Connect a plug of a stored optical fiber cord to a desired adaptor on the connection board.
(2) Change a connection by disconnecting a plug from the connection board and connecting it to another adaptor.
(3) Disconnect a plug connected to an adaptor on the connection board and store the plug on the holding board.
However, when such operations are repeatedly performed, many fiber cords become tangled, such that
(1) Entangled cords are hard to handle and the effective length becomes too short to reach the desired location of the adaptor;
(2) The weight of many fiber cords hanging from each other tends to load the fiber cord to distort the shape of the optical fiber inside the cord; and
(3) The force applied to a fiber is transmitted to the connection section of the plug attached to the end of the cord to increase optical signal attenuation; thus resulting in difficulty of achieving higher fiber density for the optical fiber distribution module.
Also, in some case, a set-type fiber cords, such as optical cable, are used for distribution of light signals on the fiber distribution board.
A set-type fiber cord is produced by bundling a plurality of fiber units, each unit containing several fiber cords.
Such set-type fiber cords are given identifying markings to enable to identify individual fiber cords within the cord unit, and such markings may be imprinted directly on the sheath for the cord, or indicated on a ring attached to the cord.
With the expansion of the optical fiber communication network, needs for switching the tangled fibers arise frequently, and a serious fiber congestion is experienced in the vicinity of the fiber sorting board, which is used to retain individual cords of the set-type fiber cords by the congregation of in-use fibers and not-in-use fibers which are stored in the holding board. Therefore, it is essential that individual fiber cords be clearly identifiable, particularly for the set-type fiber cords.
However, conventional set-type fiber cords allows identification of individual fiber cords within a given cord unit, but because the markings are the same for different units, it has been difficult to identify a particular fiber cord when the fiber units are debundled.
Especially, when such set-type fiber cords are used for fiber distribution purposes, fiber connections and fiber switching are made to different locations on the connection board on the basis of individual fibers, the bundle must be released before any particular fiber can be connected or switched to a specific adaptor.
Also, in equipment centers in a high density optical network, external fibers must be connected to internal fibers within the center using fiber termination modules (FTMs); and a distribution system is used to mange such fiber connections inside the centers.
Some examples of conventional FTMs will be presented in the following.
In general, FTMs are installed at the connection points between outdoor optical fiber cables in the subscriber loops and the indoor optical fiber cables in the central office. Examples of the conventional FTMs are reported in references (N. Tomita et al; “High-Speed & High-Capacity Technologies of Optical Fiber Line Testing System”, TECHNICAL REPORT OF IEICE (THE INSTITUTE OF ELECTRONICS INFORMATION AND COMMUNICATION ENGINEERS), CS
95-50
, pp59-66).
FIG. 29
shows an example of the configuration of the center equipment including the conventional FTM. The system comprises: FTM
1
; optical coupler
2
; fiber selector (FS); test light introducing fibers
4
to the optical coupler
2
; optical splitter
5
; center-side optical filter
6
; center communication equipment
7
; center imaging equipment
8
; transmission equipment units
9
; star coupler units
10
; test equipment modules
11
; test instruments
12
; fiber testing and equipment selection apparatus (FTES)
13
; FS master-side optical fiber
14
; fist indoor optical fiber cable
15
; second indoor optical fiber cable
16
; subscriber optical fiber cable
17
; user-side optical filter
18
; user-side data terminating unit
19
; and user-side image terminating unit
20
.
FIG. 29
shows a communication service system used for transmission of data and images. To provide high reliability, the equipment centers are provided with FTMs
1
, transmission equipment units
9
, star coupler modules
10
, and TEMs
11
.
Center communication equipment
7
used for data communication operate on signal light of a 1.3 &mgr;m band and a 1.55 &mgr;m band for imaging signals output from center image equipment
8
are injected in the star coupler module
10
through the first internal fiber cable
15
. The optical splitter
5
in the star coupler
10
wavelength multiplexes the 1.3 &mgr;m and 1.55 &mgr;m band signals, and wavelength multiplexed signal is distributed to a plurality of output ports. Signal light output from the ports of the splitter
5
is input in the FTM
1
through the second internal cable
16
. Signal light input in the FTM
1
passes through the optical coupler
2
which multi/demultiplexes test light, and is wavelength multiplexed to user-side data terminating unit
19
and user-side image terminating unit
20
through the subscriber cable
17
, to be delivered as data and image transmission service.
Tests to be conducted from the equipment center when installing or maintaining optical cable will be explained in the following. The fiber selector
3
in the fiber test module
1
selectively couples test light splitting fibers
4
and the fiber selector master-side fiber
14
connected to the test apparatus
12
in the test equipment module
11
. The fiber testing and equipment selection apparatus
13
in the FEM
11
selects the optical pulse tester in the test apparatus
12
. By this process, test light from the optical pulse tester is injected in the subscriber cable
17
, and signal loss distribution measurements and problem location searching are performed.
When performing the tests, to prevent test light from entering in the user-side data terminating unit
19
and user-side image terminating unit
20
, the user-side optical filter
18
for blocking the test light and transmitting the signal light is disposed just ahead of the user-side data terminating unit
19
and the user-side image terminating unit
20
. Also, to prevent test light and reflected light of the 1.55 &mgr;m band output from the center image equipment
8
from entering in the center communication equipment
7
, a center-side optical filter
6
for blocking test light and 1.55 &mgr;m band light and transmitting the 1.3 &mgr;m signal light is disposed in the signal light input port.
FIG. 31
shows an example of configuration of the conventional FTM
1
, and those parts that correspond to
FIG. 29
are referred to by the same reference numerals. The FTM
1
includes an excess cord length holder
21
, and an excess cable length storage shelves
22
, and on the left of FTM
1
, there are optical couplers
2
in each shelf, and the test light splitting fibers
4
separated from each coupler
2
are connected to FS
3
disposed at the bottom section. On the right side, there is an excess cable length storage space having an excess cable length holder
21
and an excess cable length shelves
22
for storing excess

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