JP2000013420A - Ring transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system capable of reducing the configuration of a time slot assignment(TSA) part in a ring transmission system. SOLUTION: One and another transmission lines are respectively provided with bridge & switch parts 22a and 22b. These bridge & switch parts 22a and 22b have functions for performing bridge processing for switching transmission data from active channel to reserve channel, switch processing for switching data existent on the reserve channel among received data to the active channel and through processing for outputting the input as it is. Besides, the bridge & switch part 22a is connected so as to input the output of the other transmission line side and the bridge & switch part 22b is connected so as to input the output of one transmission line side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring transmission system in which a plurality of nodes are connected on a ring by one transmission path and the other transmission path, and mainly relates to a UPSR (Uni-directiona).
l Path SwitchedRing and BLSR (Bi-directiona)
The present invention relates to a ring transmission system that can support both the (Line Switched Ring) system.

[0002]

2. Description of the Related Art In recent years, there has been an optical transmission system in which a plurality of nodes are connected by two optical fibers for each node and are configured in a ring shape.
There are a UPSR method and a BLSR method.

There are the following documents as such BLSR and UPSR techniques. Reference 1: Japanese Unexamined Patent Publication No. 9-214438 Reference 2: Bellcore Spec. “SONET Bidirectional Line-S
witcched Ring Equipment Generic Critaria GR-1230 D
ecember 1996 "Reference 3: Bellcore Spec." SONET Dual-Fed Unidirectio
nal Path Switched Ring (UPSR) Equipment Generic Cr
itaria GR-1400-CORE Issue1, March 1994 ''

[0004] As described in the above document 1, the UP
In the SR system, the same transmission signal is transmitted in the WEST direction and the EA
When the transmission is performed in the ST direction and there is a failure on the route on the way to the reception side, the transmission signal passing through the non-failure side is selected on the reception side. In this system, one of the two optical fibers is used as a working line, and the other is used as a protection line.

[0005] In the BLSR system, half the transmission capacity of one optical fiber is used for a working line, and the other half is used for a protection line. In the BLSR method, when a failure occurs in a path along a line, a line is relieved by using a spare line of another line by bridge processing and switch processing at a node adjacent to the failed node.

[0006]

However, in the configuration of the prior art as shown in the above-mentioned document 1, TSA (Time S
lot Assignment) section.

In general, the TSA unit handles the STM (Synchr
As the signal level of the onous transport module increases, the circuit scale increases. For example, VC-3 (Virtual Contain
er-3) In units of TSA, STM-1 and STM-6
Comparing the scale of the circuit that processes the STM-4 simply, the STM-
64 is 64 × 64 times larger.

Further, even if the TSA unit handles the same signal level, the circuit becomes larger as the time slot replacement unit becomes smaller (for example, the unit of the TSA unit is VC-3 even at the same STM-4 signal level). Unit and VC-
With four units, the circuit size of the VC-3 unit is three times or more).

Further, with the progress of the information-oriented society in recent years, requirements for a ring transmission system include the following. First, the signal level of the STM used to increase the transmission capacity in the ring transmission system must be increased, and second, the TSA unit must not be increased so that the upper limit of the number of nodes in the ring transmission system does not decrease. Is required. That is, if the unit of the TSA is large, the number of VCs that can be transmitted in one frame decreases, and as a result, the number of connectable nodes decreases.

[0010] From such a point, in order to satisfy the requirements of the ring transmission system, it is inevitable that the circuit scale of the TSA unit becomes large.

Therefore, in the ring transmission system, the request for the TSA portion of each node in the ring transmission system requires a reduction in the circuit size of the TSA portion and a configuration that requires a small number of TSAs. .

In view of the above, it has been desired to realize a system capable of reducing the configuration of the TSA section in a ring transmission system.

[0013]

The present invention employs the following structure to solve the above-mentioned problems. <Configuration 1> A plurality of nodes are connected in a ring by a transmission path including one transmission path and the other transmission path, and half of the time-division multiplexed channel of one or the other transmission path is a working channel, and the other is a working channel. In a ring transmission system using half as a spare channel, each node performs, on one transmission path and the other transmission path, bridging processing for replacing transmission data from a working channel to a protection channel, and data existing in the protection channel during reception data. And a switch circuit for performing a switch process for replacing the transmission channel with the working channel, an output on one transmission line side of the own node becomes an input of the bridge & switch circuit on the other transmission line side, and the other transmission line on the own node. These bridges so that the roadside output becomes the input of one transmission line bridge & switch circuit Ring transmission system characterized by connecting a switching circuit.

<Structure 2> A plurality of nodes are connected in a ring by a transmission line composed of one transmission line and the other transmission line, and one of the one or the other transmission line is used for an active transmission line. Transmission system using the other channel as a spare channel and a transmission system using half of the time-division multiplexed channel of one or the other channel as a working channel and the other half as a spare channel. In the ring transmission system corresponding to the transmission system of (1), each node includes, on one transmission path and the other transmission path, a bridge process for switching transmission data from a working channel to a protection channel, and data existing in the protection channel during reception data. With a bridge and switch circuit that performs switch processing to replace the input with the working channel and through processing to output the input as it is. The output on one transmission line side of the own node becomes the input of the bridge & switch circuit on the other transmission line side, and the output on the other transmission line side of the own node becomes the input of the bridge & switch circuit on the one transmission line side. A ring transmission system characterized by connecting these bridge & switch circuits.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. << Specific Example >><Configuration> FIG. 1 is a configuration diagram showing a specific example of the ring transmission system of the present invention. The configuration shown is a two-fiber BLSR
ADM (Add
2 shows the configuration of a Drop Multiplex apparatus specifically around the TSA section.

As shown, the node has an optical receiving unit (O /
E) 1a, 1b, multiplexing / demultiplexing / TSA units 2a, 2b, optical transmitting units (E / O) 3a, 3b, path switch (PSW)
4. The multiplexing / demultiplexing / TSA units 2a and 2b include demultiplexing units (DMUX) 21a and 21b, bridge and switch units 22a and 22b, and T / I (Through).
or Insert) parts 23a and 23b, multiplex part (MUX) 24
a, 24b, TSA (Time Slot Assignment) unit 25
a, 25b, 26a and 26b. However, in the illustrated configuration, the SOH of the STM which always exists as a node always exists.
(Section Overhead) Terminating circuits, circuits on the tributary side, and the like are not shown because they are not directly related to the present invention.

The optical receiver 1a (1b) is provided with a WES
Receiving an optical signal sent from the T direction (EAST direction),
Converts to an electrical signal and multiplexes / demultiplexes / TSA section 2a (2b)
This is a functional unit for sending to

The demultiplexing sections 21a and 21b in the multiplexing / demultiplexing / TSA sections 2a and 2b are functional sections for demultiplexing an input signal. The bridge and switch units 22a and 22b are circuits having a bridge function, a switch function, and a through function.
The output of the other side is configured to be branched and input.
Here, the bridge function is a function of performing a process of replacing transmission data from a working channel to a protection channel,
The switch function is a function of performing a process of replacing data existing in the protection channel in the received data with the working channel. The through function is a function of outputting an input as it is.

The T / I sections 23a and 23b are circuits for outputting through the signals from the bridge and switch sections 22a and 22b or inserting the signals from the TSA sections 26a and 26b. Multiplexers 24a, 24b
Is a circuit for byte interleaving multiplexing a signal from a tributary side (not shown) and outputting the multiplexed signal.

The TSA sections 25a and 25b are circuits for outputting the outputs from the bridge & switch sections 22a and 22b to the path switch 4 by exchanging time slots. The TSAs 26a and 26b are circuits for inputting from a circuit on the tributary side and outputting to the T / I units 23a and 23b.

The optical transmitters 3a and 3b are connected to the multiplexer 24.
a, 24b are converted from electrical signals to optical signals, and EA
This is a circuit that outputs in the ST direction (WEST direction). Further, the path switch 4 is a switch for selecting any one of the TSA units 25a and 25b and outputting the selected output to the tributary side.

<Operation> (1) First, the operation of the two-fiber BLSR will be described.

[Normal Operation] In FIG.
A description will be given taking a signal to the AST side as an example. The signal from the WEST side is optically / electrically converted by the optical receiving unit 1a and separated by the separating unit 21a. The signal from the separation unit 21a is T /
The signal is passed as it is in the I unit 23a, or a signal from the tributary side is inserted, and the signal is byte-interleaved multiplexed in the multiplexing unit 24a. The output of the multiplexing unit 24a is subjected to electrical / optical conversion in the optical transmitting unit 3a and output to the EAST side.

When a signal from the WEST side is output to the tributary side at this node, the output signal of the separation unit 21a is branched (the bridge and switch unit 22a is in a through state), and the time slot is set by the TSA unit 25a. The output is switched. Then, the signal of the TSA unit 25a is selected by the path switch 4 and output to the tributary side.

Next, when the signal from the tributary side is inserted into the EAST side at this node, the signal from the tributary side is input to the TSA section 26a, and the time slot is exchanged and output. The signal from the TSA unit 26a is T /
In the I section 23a, the signal from the west side is inserted into the time slot in which the line is set. Here, the path switch 4
Indicates that if the path is BLSR, the path is
It is used to select in advance from which direction the signal is transmitted in the T direction.

The above operation will be described in more detail with reference to a normal state diagram. FIG. 2 and FIG. 3 are explanatory diagrams showing the normal operation and the abnormal operation of the two-fiber BLSR, respectively. FIG. 4 and FIG. 5 are explanatory diagrams showing the configuration in the ADM apparatus of the two-fiber BLSR and the flow of signals in a normal state.

FIGS. 2 and 3 show two fibers BL of STM-4.
The case where four nodes (nodes 1 to 4) exist on the SR ring and the unit of TSA in each node is VC-3 is shown as an example. The state of FIG. 2 shows a case where the communication of the signal A of the VC-3 size from the node 1 to the node 2 is normal.

The normal signal A is transmitted after being allocated to a time slot of a working channel in the STM-4 signal. In FIGS. 2 to 5 and FIGS. 6 and 7 described later, the first half of the STM-4 signal is described as a working channel and the latter half as a spare channel for easy understanding. However, actually, as shown in Document 3, the first half of the input of the multiplexing units 24a and 24b of each node is defined as the working channel, and the latter half is defined as the protection channel. Absent.

FIGS. 4 and 5 focus on the nodes 1 and 2 of FIGS. 2 and 3 and show the details in detail (however, FIG. 4 focuses on only the TSA section compared to FIG. 1). Therefore, the configurations of the optical receiving units 1a and 1b and the optical transmitting units 3a and 3b are omitted.) The bridge and switch units 22a and 22b in FIG. 1 are composed of T / I units 27a and 27b and TSA units 28a and 28b as shown in these figures.

First, the signal A input from the tributary side of the node 1 is transmitted to the TSA section 26a and the T / I section 23a.
After the line is set, it is inserted into the assigned time slot in the working channel of STM-4, and after passing through the transmission line,
Input to node 2. The node 2 drops the input signal and inputs the signal to the TSA unit 25a.
After the selection, the data is output to the tributary side. Thus, communication of the signal A from the node 1 to the node 2 is performed.

[At the time of abnormal operation] FIG. 3 and FIG.
At 7, the operation of transmitting the signal A from the node 1 to the node 2 in the same manner as in the normal operation will be described by taking a case where a failure occurs in the transmission line as an example.

The example of FIG. 3 shows how a signal is transmitted, taking as an example a case where a fault has occurred in the fiber that was transmitting the signal A at the time of normal operation. The node 1 detects a failure in the transmission path, causes a bridge, and allocates the fiber to a spare channel of the backward fiber for transmission. The nodes 3 and 4 pass this signal through.

The node 2 which has received the signal A in the reverse direction performs the switching process and assigns it to the working channel of the fiber inside (on the drawing) (assigns it to the original channel). The signal is dropped as in the case where no failure has occurred in the node 2 and output to the tributary side.

FIGS. 6 and 7 show the AD of the two-fiber BLSR.
FIG. 3 is an explanatory diagram showing a configuration inside the M device and a flow of a signal at the time of abnormality. However, since FIG. 1 focuses on only the TSA unit, the configuration of the optical receiving units 1a and 1b and the like is not shown.

The signal A input from the tributary side of the node 1 is set up by the TSA unit 26a and the T / I unit 23a, inserted into the assigned time slot in the working channel of the STM-4, and inserted into the transmission line. Is output. At the same time, the same signal is branched to the bridge & switch unit 22b.

When the node 1 recognizes that a failure has occurred in the transmission line on the transmission side, the node 1 bridges and switches 22b.
Performs bridge processing. The bridge process is TSA
The signal that was in the working channel is set in advance in the unit 28b so that the time slot is replaced with the spare channel, and the spare channel replaced in the T / I unit 27b is replaced with the input signal from the node 2 only when a failure is recognized. To the spare channel of.

The node 1 outputs the signal to the WEST-side transmission path which is opposite to the normal state. At the nodes 3 and 4, the signal A is passed without any processing.

In the node 2, the signal input from the EAST side is branched at the subsequent stage of the T / I section 23b and input to the bridge & switch section 22a. Bridge & switch part 22a
When the TSA unit 28a sets in advance that the spare channel is to be replaced with the working channel by replacing the time slot, and recognizes that a failure has occurred in the input transmission line from the node 1, the T / I unit 27a 1 is inserted into the working channel of the input signal phase. Thereafter, as in the normal state, this signal is dropped and input to the TSA unit 25a.
After being selected by the path switch 4, it is output to the tributary side. As a result, even in the event of a failure, the nodes 1 to 2
The communication of the signal A is performed.

Further, as described in Document 2, the signal from the node 2 to the node 1 also needs to be bridged at the node 2 and switched at the node 1. Accordingly, bridge processing and switch processing are performed in the bridge & switch unit 22b of the node 1. Similarly, in the node 2, the bridge & switch unit 22a performs the bridge processing and the switch processing.

The basic operation of the two-fiber BLSR is well known, as shown in, for example, Reference 2 described in the related art, so that the description is omitted here.

(2) Next, the point that this specific example can support the UPSR system will be described. FIG. 8 is an explanatory diagram when applied to the UPSR system. FIG. 8 corresponds to the configuration of the BLSR described with reference to FIG. 1, but at the time of UPSR, the T / Ts in the bridge & switch units 22a and 22b are set.
The I sections 27a and 27b are set to through. Other than this, there is no change from the configuration at the time of BLSR.

Thus, it is possible to realize a UPSR transmission apparatus that transmits the same transmission signal in the west direction and the east direction. The basic operation of the UPSR-type transmission device is well-known, for example, as shown in Reference 3 of the related art, and a description thereof will be omitted.

<Effects> As described above, according to the specific example,
The ring transmission system has the following effects. 1. For example, since the number of TSAs is smaller than that of the conventional BLSR method shown in Reference 1, even in a large-scale ADM apparatus, the circuit size of the TSA unit can be reduced. 2. Since the ring bridge and switch are shared, the circuit scale can be reduced as compared with the conventional configuration. 3. Since the number of circuits such as TSA is small, the number of wirings can be reduced.

In the above specific example, an STM-4 ring has been described as an example. However, the present invention can be applied to a transmission apparatus of a ring transmission system having an arbitrary STM signal level. Further, in this specific example, the description has been made using the “STM” which is the name on the ITU-T, but the same applies when the name “STS” on the Bellcore is used. Furthermore, the present invention can be applied to a ring transmission system in which each node is connected in a ring shape by one and the other transmission paths and a signal is time-division multiplexed, similarly to the above specific example.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a specific example of a ring transmission system of the present invention.

FIG. 2 is an explanatory diagram showing a normal operation of the two-fiber BLSR in the ring transmission system of the present invention.

FIG. 3 is an explanatory diagram showing an operation when a two-fiber BLSR is abnormal in the ring transmission system of the present invention.

FIG. 4 is an explanatory diagram (No. 1) showing the configuration inside the ADM apparatus of the two-fiber BLSR and the operation in a normal state in the ring transmission system of the present invention.

FIG. 5 is an explanatory diagram (No. 2) showing the configuration in the ADM apparatus of the two-fiber BLSR and the operation at the time of normal operation in the ring transmission system of the present invention.

FIG. 6 is an explanatory diagram (part 1) showing a configuration in an ADM device of a two-fiber BLSR and an operation at the time of abnormality in the ring transmission system of the present invention.

FIG. 7 is an explanatory diagram (part 2) illustrating the configuration of the two-fiber BLSR in the ADM device and the operation in the event of an abnormality in the ring transmission system of the present invention.

FIG. 8 is an explanatory diagram when the ring transmission system of the present invention is applied to the UPSR system.

[Explanation of symbols]

 1a, 1b Optical receiving section (O / E) 3a, 3b Optical transmitting section (E / O) 4 Path switch (PSW) 21a, 21b Separating section 22a, 22b Bridge & switch section (BR) 23a, 23b T / I section 24a, 24b multiplexing unit

Claims (2)

[Claims] A plurality of nodes are connected in a ring shape by a transmission path including one transmission path and another transmission path, and a half of a time-division multiplexed channel of the one or other transmission path is a working channel. In a ring transmission system in which the other half is a spare channel, each node includes: a bridge process for replacing transmission data from the working channel to a spare channel on the one transmission line and the other transmission line; And a switch circuit for performing a switch process for replacing data existing in the current channel with the working channel, and an output of one transmission line side of the own node becomes an input of the bridge & switch circuit of the other transmission line side, and The output on the other transmission line side of the node becomes the input of the bridge & switch circuit on one transmission line side. A ring transmission system characterized in that these bridge and switch circuits are connected in such a manner as to make the connection. 2. A plurality of nodes are connected in a ring shape by a transmission line including one transmission line and another transmission line, and one of the one or other transmission lines is used as an active transmission line. A transmission system in which the other transmission line is used as a spare transmission line, and a transmission system in which half of the time-division multiplexed channel of the one or other transmission lines is used as a working channel and the other half is used as a protection channel. In the ring transmission system corresponding to the transmission system of (1), each node includes, on the one transmission line and the other transmission line, a bridge process for replacing transmission data from the working channel to a protection channel, and A bridge and switch circuit that performs switch processing to replace the data to be used with the working channel and through processing to output the input as it is. In addition, the output of one transmission line side of the own node becomes the input of the bridge & switch circuit of the other transmission line side, and the output of the other transmission line side of the own node becomes the input of the bridge & switch circuit of the one transmission line side. A ring transmission system in which these bridge and switch circuits are connected such that: