Shelf unit for communication system

Details Shelf unit for communication system Shelf unit for communication system

2002-01-23

2004-05-04

Lee, John D. (Department: 2874)

Optical waveguides

Accessories

Splice box and surplus fiber storage/trays/organizers/ carriers

Reexamination Certificate

active

06731851

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a shelf unit which is a piece of equipment of a communication system, and particularly relates to a shelf unit in which modules accommodating dispersion compensating fibers are mounted.
Due to rapid increase of IP traffics, it is necessary to enhance transmission efficiency by increasing transmission capacity and/or making use of long-distance transmissions. A photonic network using a WDM (Wavelength Division Multiplexing) transmission system is becoming of an interest as a solution for achieving such enhanced transmission efficiency.
For a long-distance WDM network having a total transmission distance in a range of a several thousands of kilometers, regenerators are installed in the network at a certain interval. However, the distance between the regenerators is subjected to a limitation due to degradation of optical waveforms caused by wavelength dispersion in optical fibers. In order to suppress such wavelength dispersion, dispersion compensating relays may be provided in the network at a certain interval. With the distribution compensation relays being provided at a certain interval, the regenerators may be provided with an increased distance between them. Accordingly, total cost of the network can be reduced since less number of costly regenerators is required.
In an Ultra Long Haul WDM system aiming for a transmission distance over 3000 km without using regenerators, in order to achieve compensation with an increased efficiency, it is necessary to use DCF modules having dispersion compensating levels that correspond to the wavelengths of the signal.
FIG. 1
shows a dispersion compensating relay
10
provided with dispersion compensating fibers (DCFs)
11
-
1
to
11
-n for optical paths &lgr;
1
to &lgr;n, respectively. The dispersion compensating fibers
11
-
1
to
11
-n are formed into modules to provide dispersion compensating fiber modules
12
-
1
to
12
-n. The dispersion compensating fiber modules
12
-
1
to
12
-n are mounted inside a shelf
13
, which may be box-shaped. The dispersion compensating fiber modules
12
-
1
to
12
-n are mounted in the shelf
13
to constitute a dispersion compensating fiber module shelf unit
14
.
In
FIG. 1
, a receiving amplifier
15
, a wave-dividing filter
16
, a wave-combining filter
17
and a transmitting amplifier
18
are also shown.
The level of dispersion in an optical fiber depends on material and structure of the optical fiber and on the transmission distance. Also, various types of optical fibers are used among various communication common carriers and even if the same type of an optical fiber is used, the transmission distance may be different. Therefore, the dispersion compensation level of the DCF must be customized. Accordingly, there are various types of DCF modules for various dispersion compensation levels.
One of the parameters determining the dispersion compensation level is the length of the DCF. Particularly when compensating for a positive dispersion, a long DCF is required since the DCF has a small compensation level per unit length. Accordingly, the size of the DCF module increases with an increase of the dispersion level.
To build a system, various DCF modules are required for various transmission channels of the communication common carriers. Accordingly, there is a need for a mounting structure of a DCF shelf in which DCF modules with different width can be accommodated with improved efficiency.
2. Description of the Related Art
FIGS. 2
,
3
A and
3
B are diagrams showing a dispersion compensating fiber module shelf unit
20
of the related art. The shelf unit
20
includes a shelf
21
provided with lower guide rails
22
and upper guide rails
23
. Dispersion fiber modules
30
,
40
,
50
of different sizes are supported by the guide rails
22
and
23
.
The shelf
21
includes a shelf main body
24
, the guide rails
22
,
23
and screw-hole plates
25
,
26
.
The shelf main body
24
is a rectangular box having an opening
22
at its front face and has a certain width W
1
conforming to a global standard and has a certain size. The lower guide rails
22
and the upper guide rails
23
are fixed to the shelf main body
24
and are arranged at pitch P
1
. Screw holes
28
of the lower screw hole plate
25
and screw holes
29
of the upper screw hole plate
26
are arranged at pitch P
2
.
A dispersion compensating fiber module
30
of a first size has a width A which equals to the pitch P
1
and accommodates a dispersion compensating fiber
31
of a predetermined length L
1
wound on a reel
32
. The module
30
is provided with a rail
33
on its upper surface, a rail
34
on its lower surface, a flange
35
on an upper end of the front side, a flange
36
on a lower end of the front side and an optical connector
37
on a central step part on the front side. The flanges
35
and
36
are provided with retaining screws
38
and
39
, respectively.
A dispersion compensating fiber module
40
of a second size has a width
2
A which is double the width A of the dispersion compensating fiber module
30
and accommodates a dispersion compensating fiber
41
of a predetermined length L
2
wound on a reel
42
. The length L
2
is greater than the length L
1
. In a manner similar to the module
30
, the module
40
is provided with rails
43
,
44
, flanges
45
,
46
and an optical connector
47
. The flanges
45
and
46
are provided with retaining screws
48
and
49
, respectively.
A dispersion compensating fiber module
50
of a third size has a width
3
A which is three-times greater than the width A of the dispersion compensating fiber module
30
and accommodates a dispersion compensating fiber
51
of a predetermined length L
3
wound on a reel
52
. The length L
3
is greater than the length L
2
. In a manner similar to the modules
30
and
40
, the module
50
is provided with rails
53
,
54
, flanges
55
,
56
and an optical connector
57
. The flanges
55
and
56
are provided with retaining screws
58
and
59
, respectively.
A dispersion compensating fiber module
60
of a fourth size has a width
4
A which is four-times greater than the width A of the dispersion compensating fiber module
30
and accommodates a dispersion compensating fiber
61
of a predetermined length L
4
wound on a reel
62
. The length L
4
is greater than the length L
3
. In a manner similar to the modules
30
,
40
and
50
, the module
60
is provided with rails
63
,
64
, flanges
65
,
66
and an optical connector
67
. The flanges
65
and
66
are provided with retaining screws
68
and
69
, respectively.
The dispersion compensating fiber modules are configured to have widths which are integral multiples of the width of the dispersion compensating fiber module
30
of a first size.
The dispersion compensating fiber modules
30
,
40
,
50
,
60
are inserted into the shelf main body
24
in Y
1
-direction with the rails
34
,
44
,
54
,
64
being engaged with and guided by the guide rails
22
and the rails
33
,
43
,
53
,
63
being engaged with and guided by the guide rails
23
. As shown
FIG. 3A
, the dispersion compensating fiber modules
30
,
40
,
50
,
60
are mounted to the shelf main body
24
in such a manner that with the rails
34
,
33
,
54
,
64
engaging the guide rails
22
and the rails
33
,
43
,
53
,
63
engaging the guide rails
23
, the flanges
35
,
45
,
55
,
65
are fixed to the screw-hole plate
26
by screwing the retaining screws
38
,
48
,
58
,
68
into the screw holes
29
of the screw-hole plate
26
and the flanges
36
,
46
,
56
,
66
are fixed to the screw-hole plate
25
by screwing the retaining screws
38
,
48
,
58
,
68
into the screw holes
28
of the screw-hole plate
25
so as to prevent the dispersion compensating fiber modules
30
,
40
,
50
,
60
from sliding out of the shelf main body
24
. The shelf unit
20
is in a state where the dispersion compensating fiber modules
30
,
40
,
50
,
60
are closely mounted in the shelf main body
24
.
It is

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