Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
2000-03-28
2004-07-13
Hsu, Alpus H. (Department: 2665)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C370S516000, C375S362000, C375S371000, C398S101000, C398S155000
Reexamination Certificate
active
06763038
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light transmission equipment, and in particular to a clock change circuit used for a light transmission equipment for realizing a concatenation of synchronous transfer signals (STS) used in a synchronous transmission mode (STM).
In a recent light transmission equipment, a data communication technique such as the Internet or the like is required for enhancing a working efficiency of a single signal shared with many people. Also, a transmission function of STS-48 (2.4 Gb/s) data by the synchronous transmission mode for accommodating the Internet signal whose signal rate is improving is required for the improvement of services.
2. Description of the Related Art
The above-mentioned STS-48 data have a frame format as shown in
FIG. 8
, and a system diagram in which a light signal transmission is performed by using such STS-48 data is shown in FIG.
9
.
Such a light transmission system forms a 4F-BLSR (4 Fiber-Bidirectional Line Switched Ring) system where stations A-D respectively forming a light transmission equipment are mutually connected with four optical fibers.
The STS-48 (2.4 Gb/s) data flow through each of the four optical fibers, which are shown by solid lines used as work or active lines (WK) and by dotted lines used as protect or standby lines (PT).
A prior art arrangement (1) of each station (light transmission equipment) in such a light transmission system is shown in FIG.
10
.
In this arrangement, a circuit board is divided into two, i.e. a SHELF
1
for the work line and a SHELF
2
for the protect line. In the circuit board SHELF
1
, as for the station C in
FIG. 9
for instance, data are to be inputted from the work line (WK) and the protect line (PT) on the EAST side where the side of the station D is made the EAST (East side) and the side of the station B is made the WEST (West side). By a connection switch in the middle, the data are to be outputted to the work line (WK) and the protect line (PT) on the same EAST side.
This applies to the WEST side in the circuit board SHELF
2
. As a matter of course, by the connection switch, it is made possible to input the data from the work line (WK) and the protect line (PT) on the EAST side of the circuit board SHELF
1
and to output the data to the work line (WK) and the protect line (PT) on the WEST side of the circuit board SHELF
2
. Conversely it is made possible to input the data from the work line (WK) and the protect line (PT) on the WEST side of the circuit board SHELF
2
and to output the data to the work line (WK) and the protect line (PT) on the EAST side of the circuit board SHELF
1
.
To be more specific, the circuit board SHELF
1
is provided with a receiving portion OR
1
for the work line (WK) and a receiving portion OR
2
for the protect line (PT), which are respectively connected to demultiplexing portions DMUX
1
and DMUX
2
.
In addition, the circuit board SHELF
2
is provided with receiving portions OR
3
and OR
4
for the work line (WK) and the protect line (PT) from the WEST side, which are respectively connected to demultiplexing portions DMUX
3
and DMUX
4
.
Since each of the lines transmits the STS-48 data, 1-48CH data flow through a single optical fiber, while at the demultiplexing portions DMUX
1
-
4
the data are divided into data of 24 channels (hereinafter occasionally abbreviated as CH's) to be bundled. Then, from the demultiplexing portion DMUX
1
for instance, 1-24CH data are provided to the EAST side of an add/drop portion ADM
1
which forms an add/drop portion ADM, and 1-24CH data from the demultiplexing portion DMUX
2
are similarly provided to the EAST side of the add/drop portion ADM
1
.
Furthermore, 1-24CH data from the demultiplexing portion DMUX
3
and 1-24CH data from the demultiplexing portion DMUX
4
are inputted to the WEST side of the add/drop portion ADM
1
.
Also, at an add/drop portion ADM
2
, 25-48CH data from the demultiplexing portion DMUX
1
and 25-48CH data from the demultiplexing portion DMUX
2
are inputted to the EAST side, and 25-48CH data from the demultiplexing portion DMUX
3
and 25-48CH data from the demultiplexing portion DMUX
4
are inputted to the WEST side.
It is to be noted that add/drop portions ADM
3
and ADM
4
are provided as physical spare add/drop portions for the above-mentioned add/drop portions ADM
1
and ADM
2
.
Also, the WEST side of the add/drop portion ADM
1
outputs data bundles of 24CH's, one of which is provided to a multiplexing portion MUX
3
of the circuit board SHELF
2
and the other of which is provided to a multiplexing portion MUX
4
of same.
Furthermore, the EAST side of the add/drop portion ADM
1
outputs data bundles of 24CH's, one of which is provided to a multiplexing portion MUX
1
of the circuit board SHELF
1
and the other of which is provided to a multiplexing portion MUX
2
of same.
At the add/drop portion ADM
2
, the output data on the WEST side are divided into data bundles of 25-48CH, one of which is provided to the multiplexing portion MUX
3
and the other of which is provided to the multiplexing portion MUX
4
. Furthermore, one of the 25-48CH output data on the EAST side are provided to the multiplexing portion MUX
1
, and the other of the 25-48CH output data are provided to the multiplexing portion MUX
2
.
Then, the data of the multiplexing portions MUX
1
-
4
respectively pass through transmitting portions OT
1
-OT
4
to be outputted to the work line (WK) and the protect lines (PT) on the EAST and the WEST side.
A prior art arrangement of each add/drop portion ADM is shown in
FIG. 11
, in which line data on the EAST and the WEST side are provided to a span switch S-SW with 24CH data being divided into data bundles of 12CH's on the work line and the protect line.
The span switch S-SW, as shown in
FIG. 11
, switches over the work line (WK) and the protect line (PT) based on a control signal (not shown), and a ring switch R-SW is provided next to the span switch S-SW to perform the switching operation opposite to the span switch S-SW.
The data which pass through the ring switch R-SW are provided to clock change circuits CSC
1
and CSC
2
, in which a clock change from a line side to an equipment side is performed to output the data of 48CH's.
The output data of the clock change circuits CSC
1
and CSC
2
are provided to a selector SEL through time slot assignment portions TSA
1
and TSA
2
, where the data on either the EAST or the WEST side are to be dropped or branched to the equipment side.
In addition, the data from the equipment side are provided to service selectors SS
1
and SS
2
through time slot assignment portions TSA
3
and TSA
4
. The 48CH data from the clock change circuits CSC
1
and CSC
2
are also provided to the service selectors SS
1
and SS
2
.
Accordingly, either the line side or the equipment side is preliminarily selected, whereby the data divided into the data bundles of 12CH's are sent to a ring bridge circuit R-Br. After performing the switching operation just opposite to the ring switch R-SW at the ring bridge circuit R-Br, the switching operation just opposite to the span switch S-SW is performed at a span bridge circuit S-Br, so that the data bundles of 12CH's are respectively outputted as the line data on the WEST and the EAST side.
The above-mentioned example refers to the case where the 48CH (2.4 Gb/s) data are transmitted through a single optical fiber, while the case where STS-192 data are transmitted can be similarly considered as shown by parentheses in FIG.
10
.
In this case, however, since 1-192CH data are divided at the demultiplexing portions DMUX
1
-DMUX
4
, not two but eight add/drop portions ADM are required for each circuit board. Also in this case, each of the add/drop portions has the arrangement shown in FIG.
11
.
While the four optical fibers are used in the above-mentioned example, the case where two optical fibers (2F-BLSR) are used can be similarly considered as shown in FIG.
12
.
Namely, the 48CH data from the EAST side are divided into data bundl
Maehira Masayuki
Matsunaga Koji
Ogata Yumiko
Shioda Masahiro
Taniguchi Atsuki
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