JPH10308704A - Oh signal protection system for optical network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the automatic recovery of overhead (OH) signal by monitoring the fault of line from input signals from the input sides of two pairs of bidirectional optical transmission lines, extracting the OH signal from the input side of the other bidirectional line where no fault occurs when any fault is detected on one bidirectional line, and outputting this signal to the output sides of two pairs of bidirectional optical transmission lines. SOLUTION: When a fault occurs on any one of active lines A1 and A2' on the side of WEST, this fault is detected from input signal interruption from A1 by a fault detection part 11 and an OH signal switching part 21 is operated. Then, the OH signal is extracted from an OH extraction part 32 connected to B1 and when this signal is not its own ID, it is outputted to both A1' and B1' while using OH signal inserting parts 35 and 36. Besides, when a fault occurs on any one of active lines A1 and A2' on the side of EAST, this fault is detected from input signal interruption from A1 by a fault detection part 13 and an OH signal switching part 22 is operated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OH signal protection method for an optical network for protecting a link monitor with an overhead (OH) signal when a failure occurs in a line of an optical transmission network having working and protection lines. .

[0002]

2. Description of the Related Art In an optical transmission network in which an optical repeater is interposed between two optical terminators, an overhead signal is mainly used for monitoring and controlling the optical terminator and the optical repeater, changing various settings, and the like. In many cases, a so-called link monitor is formed by multiplexing a signal (a signal used in actual communication; the same applies hereinafter) and using an HDLC protocol or the like. FIG. 6 shows an SDH (Synchronous digital hie).
FIG. 3 is a diagram illustrating a configuration example of an optical transmission network, in which 100 and 300 are optical termination devices,
A is an optical repeater. In this specification, the optical terminating device 100 and the optical terminating device 300 constituting the optical transmission network are also referred to as a first optical terminating device and a second optical terminating device, respectively. The EAST side and the first optical termination device 100 side of the optical repeater are tentatively referred to as the WEST side.

The optical transmission line is provided with two sets of transmission lines for working and protection for line protection (communication line protection) (each transmission line uses a bidirectional line as shown in the figure). The same shall apply hereinafter) and SDH accordingly
Both the active and standby relays are performed by the optical relay device 200A. The overhead signal is normally connected to either the working transmission line or the protection transmission line to avoid confusion of the connection because bidirectional communication is performed, and is not an overhead signal having its own ID in the optical repeater 200A. In that case, a simple relay is performed.

[0004]

In the optical network as described above, the optical terminating device 100 and the optical terminating device 300 are used.
When communication is performed using the working line between and the overhead signal is connected to the working line and a link monitor using the overhead signal is performed,
When a failure (for example, line interruption) occurs between the optical terminating device 100 or 300 and the optical repeater 200A, the protection line enters the operation state in the main signal, but the overhead signal remains connected to the working line. The signal is interrupted, and link monitoring cannot be performed. Therefore, the user needs to switch the connection of the overhead signal from the working line to the protection line, but this operation is cumbersome, and when a large number of optical repeaters are interposed or a line failure is complicated, There was a problem that this became difficult.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has been made in consideration of an OH of an optical network capable of automatically recovering an overhead signal even when a line failure occurs.
It is intended to provide a signal protection method.

[0006]

According to the OH signal protection system of an optical network according to the present invention, an optical repeater is interposed between a first optical terminal and a second optical terminal, and the optical repeater is interposed between these devices. An optical network for protecting the connection of an overhead (OH) signal when a line failure occurs in the bidirectional optical transmission line on an optical network connected by two pairs of the active and standby bidirectional optical transmission lines. In the OH signal protection method, the optical repeater includes an EAST side (tentatively referring to the second terminator side),
On both sides of the WEST (the first terminating device side is tentatively referred to), failures of the two sets of bidirectional optical transmission lines are monitored by input signals from the input sides of the two sets of bidirectional optical transmission lines. , The EAST side (or the WEST side)
When a line failure of any one of the two-way lines is detected, the overhead signal is extracted from the input side of the other two-way line where no failure has occurred, and the extracted overhead signal is sent to the WEST side (or the EAST side)
The connection of the overhead signal is protected by outputting to both output sides of the two sets of bidirectional optical transmission lines.

Also, an optical repeater is interposed between the first and second optical terminating devices, and these devices are connected to each other by two pairs of active and standby bidirectional optical transmission lines. In the case where a line failure occurs in the bidirectional optical transmission line on the existing optical network, in an OH signal protection device of the optical network for protecting the connection of an overhead (OH) signal, the optical repeater is connected to the EAST side (the The second terminating device side is tentatively named), the west side (the first terminating device).
Means for monitoring faults in the two sets of bidirectional optical transmission lines based on input signals from the input sides of the two sets of bidirectional optical transmission lines, respectively, and the EAST side. Means for extracting the overhead signal from the input side of the other two-way line where no fault has occurred when detecting a line fault in any of the two-way lines (or the WEST side); The signal is transmitted from the WEST side (or the EAST side) to the 2
Means for outputting to both output sides of the set of bidirectional optical transmission lines.

The OH signal protection system of the optical network according to the present invention employs the above-described method or apparatus configuration to cause a failure in both the working and protection optical transmission lines on the EAST or WEST side of the optical repeater. Unless otherwise, the connection of the overhead signal can be protected.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an optical repeater 200 for explaining the present invention.
In the figure, reference numerals 11 to 14 denote a fault detection unit, 21 and 22 denote overhead signal switching units, 31 to 34 denote overhead signal extraction units, and 35 to 38 denote overhead signal insertion units. The optical repeater is usually provided with an amplifier circuit for amplifying and transmitting the main signal, a control circuit for controlling the amplifier, and the like. However, since it is not directly related to the present invention, FIG.
In these figures, these circuits are omitted.

As shown in FIG. 1, in the optical repeater 200 of the present embodiment, the input side (A1, B) on the west side is divided by the working and protection overhead signal insertion units 35, 36.
1) are respectively connected to the fault detection units 11 and 12 and the overhead signal extraction units 31 and 32, and their outputs are connected to the overhead signal switching unit 21. The output of the overhead signal switching unit 21 is used as the overhead signal insertion unit 35, 36. Similarly, EAST
On the side, a working and protection overhead signal insertion unit 3
The respective outputs are connected to failure detection units 13 and 14 and overhead signal extraction units 33 and 34, respectively, to the input side (A2, B2) bordering on lines 7 and 38, and are respectively connected to the overhead signal switching unit 22. The output of the signal switching unit 22 is the overhead signal insertion unit 3
7 and 38 are connected.

Therefore, as shown in FIG. 2, when a failure occurs in the working line, a protection line is connected, and when a failure occurs in the protection line, the working line is connected to connect the protection line. The signal is extracted.
Side and west side independently. That is, WEST
If the working line (A1, A2 ') on the side fails
When the input signal from A1 is cut off, the failure detection unit 11 detects this and operates the overhead signal switching unit 21;
The overhead signal is extracted from the overhead signal extraction unit 32 connected to B1, and the overhead signal
If D is not its own ID, it outputs to both A1'B1 'using overhead signal insertion units 35 and 36. The reason that the overhead signal is output to both the working side (A1 ') and the protection side (B1') is that the detection of a failure on the input side is easily performed by the presence or absence of an input signal, normality / abnormality, and the like. Although it can be determined, a failure detector having a complicated configuration is required to detect a failure on the output side.

Also, the working line (A1'A2) on the EAST side
, When the signal input from A2 is interrupted, the failure detection unit 13 detects this and operates the overhead signal switching unit 22 to extract the overhead signal from the overhead signal extraction unit 34 connected to B2, If the ID of this overhead signal is not its own ID, the overhead side (A
2 ') and the spare side (B2').

An overhead signal is connected to the protection line, and when a failure occurs in the protection line, the overhead signal is transmitted from a line in which no failure has occurred by the same operation as described above. Extract and output overhead signals to both lines. If the ID of the input overhead signal is its own ID, the overhead signal is terminated and processed by the optical repeater, and the processing result is output as an overhead signal. Since there is no relationship, a detailed description of its configuration and operation will be omitted.

Next, the operation of the present invention will be described with reference to FIGS. For example, as shown in FIG.
And two optical repeaters 201,
When the terminal 202 is connected, as shown in FIG.
It is assumed that a failure occurs in the working line at one point (the optical repeater 200 shown in FIG. 1 is used for each optical repeater). The overhead signal input from the WEST side of the optical repeater 201 detects a failure on the working side,
Protection line B by overhead signal switching unit 21
1 and output to both the working and protection lines on the EAST side. In addition, since no failure is detected in the optical repeater 202 and the optical terminal 300, the working side is selected as it is.

In the reverse direction, the optical repeater 201
The working line is selected on the east side of the optical relay device 202, and the protection line is automatically selected on the west side of the optical repeater 201 and the optical terminal device 100. Therefore, failure S
Even if 1 occurs, the overhead signal can be automatically restored in both directions, and link monitoring becomes possible.

Further, as shown in FIG.
If it occurs in S3 and S4, the optical repeater 201
WEST side selects a protection line due to failure S2,
The AST outputs the signal to both the working line and the protection line.
However, in the optical repeater 202, since the failure S3 has occurred in the protection line on the west side, the working side is selected,
On the EAST side, it is output to both the working line and the protection line. In the optical terminal device 300, since a failure S4 has occurred, a protection line is selected. In addition, the overhead signal in the reverse direction is switched from the protection side to the working side by the optical repeater 202 and switched from the working side to the protection side by the optical repeater 201, so that the communication is not interrupted in both directions. As described above, according to the present invention, in each optical repeater, if either the working line or the protection line is normal, transmission and reception of the overhead signal can be performed,
Link monitoring using overhead signals becomes possible.

In the above embodiment, an optical network in which two optical repeaters intervene has been described.
This can be performed as long as no failure occurs in both the working line and the protection line on the ST or WEST side, and it goes without saying that any number of optical repeaters may be interposed.

[0018]

As described above, the optical network O
In the H signal protection method, the EAST side and the WEST side of the optical repeater monitor a line failure with a working and protection input signal, and when a line failure is detected, an overhead signal is extracted from a line where no failure has occurred. By outputting the extracted overhead signal to both lines, automatic recovery of the overhead signal can be easily performed even when a large number of optical repeaters are interposed or the line failure is complicated. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical repeater for explaining the present invention.

FIG. 2 is a diagram illustrating an operation of selecting an overhead signal switching unit in the optical repeater illustrated in FIG. 1;

FIG. 3 is a diagram illustrating an example of overhead communication in a network using an optical repeater.

FIG. 4 is a diagram showing a flow of an overhead signal when a line failure occurs.

FIG. 5 is a diagram showing a flow of an overhead signal when a line failure occurs.

FIG. 6 is a diagram illustrating a configuration example of a network using an optical repeater;

[Explanation of symbols]

 11 to 14 fault detection unit 21, 22 overhead signal switching unit 31 to 34 overhead signal extraction unit 35 to 38 overhead signal insertion unit 100 first optical termination device 200, 200A, 201, 202 optical repeater device 300 second optical termination apparatus

Claims (2)

[Claims] 1. An optical repeater is interposed between a first optical terminal and a second optical terminal, and these apparatuses are connected by two pairs of working and protection two-way optical transmission lines. In the optical network OH signal protection method for protecting a connection of an overhead (OH) signal when a line failure occurs in the bidirectional optical transmission line on the existing optical network, the optical repeater includes: On both sides of the second terminating device side and the WEST side (temporarily terming the first terminating device side), the two sets are input signals from the input sides of the two sets of bidirectional optical transmission lines, respectively. Of the EAST side (or the WEST side), and when a line failure of any one of the two-way lines is detected, the input of the other two-way line having no failure is monitored. ~ side The overhead signal is extracted from the two sets of bidirectional optical transmission lines on the WEST side (or the EAST side), and the connection of the overhead signal is established. OH signal protection method of optical network to be protected. 2. An optical repeater is interposed between a first optical terminating device and a second optical terminating device, and these devices are connected by two pairs of working and protection two-way optical transmission lines, respectively. An optical network OH signal protection device for protecting the connection of an overhead (OH) signal when a line failure occurs in the bidirectional optical transmission line on the existing optical network; The second terminating device side is tentatively named), WE
On both the ST side (tentatively referring to the first terminal device side),
Means for monitoring failures of the two sets of bidirectional optical transmission lines based on input signals from the input sides of the two sets of bidirectional optical transmission lines; and either the EAST side (or the WEST side) Means for extracting the overhead signal from the input side of the other two-way line in which no fault has occurred when the line fault of the incoming line is detected, and transmitting the extracted overhead signal to the WEST side (or the EAST side). Means for outputting to both output sides of the two sets of bidirectional optical transmission lines; and an OH signal protection apparatus for an optical network.