JPH0771107B2 - Optical communication system failure detection / removal method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fault detection / elimination method for an optical communication system in which a plurality of nodes are connected by an optical transmission line having a star coupler.

(Prior Art and its Problems) Conventionally, a star type optical communication system is known in which a plurality of nodes are connected by an optical transmission line having a passive star coupler and data is exchanged between the nodes. Fifth
The figure shows the overall configuration of a conventional optical communication system. A plurality of nodes 1, 2a to 2c are connected to each other via an optical transmission line 4 via a passive star coupler 3. In this conventional optical communication system, a specific node 1 of these plural nodes 1, 2a to 2c serves as a monitoring station, and constantly monitors the signal state of the optical transmission line 4 to shut off the power supply to the failed node. By removing the failed node from the system, the situation where the entire system becomes incommunicable is avoided.

More specifically, the node 1 of the monitoring station, as shown in FIG. 6, has a central control unit 10 that controls the node 1 and a communication control unit 11 that controls the data communication between the nodes. An optical / electrical conversion block 12a connected to an optical transmission line 4 formed of an optical fiber cable and converting an optical signal input from the optical transmission line 4 into an electric signal and an electric signal from the communication control unit 11 are converted into an optical signal. And an optical transmission / reception unit 12 including an electric / optical conversion block 12b that outputs a transmission signal to another node to the optical transmission line 4, a power supply 13, and a power switch 14 whose operation is controlled by a central control unit 10. The optical / electrical conversion block 12 of the central controller 10, the communication controller 11, and the optical transmitter / receiver 12
The power a is directly fed from the power source 13 via the power feeding line 15, and the electric / optical conversion block 12b of the optical transmitter / receiver 12 is fed from the power source 13 to the power feeding line 1.
Power is supplied via 6 and the power switch 14.

On the other hand, the other nodes 2a to 2c are, as shown in FIG. 7, a central control unit 10 'that controls each node 2a (2b, 2c).
And a communication control unit 11 ′ that controls the data communication between the nodes.
An optical transmission / reception unit 12 'similar to the optical transmission / reception unit 12 of FIG. 6, which is connected to the optical transmission line 4 and performs electric / optical conversion and optical / electrical conversion of a transmission signal; and a power supply 13', and Power switch
14 ', the central control unit 10' is directly fed from a power source 13 'through a power feed line 15', and the communication control unit 11 'and the optical transmitter / receiver unit 12' connect a power switch 14 'and a power feed line 16'. Powered through. The power switch 14 'of each node 2a (2b, 2c) is connected to the output side of the central control unit 10 of the monitoring station node 1 via the power switch control line 5a (5b, 5c), respectively.
The central control unit 10 of the monitoring station node 1 controls the operation of each.

The central control unit 10 of the monitoring station node 1 uses the optical
The signal state of the optical transmission line 4 input through the electrical conversion block 12a and the communication control unit 11 is constantly monitored, and the optical transmission line 4 is filled with abnormal signals such as continuous light and unsynchronized irregular light emission. If it is determined that communication between the nodes is not possible, the central control unit 10 determines that the power switch control lines 5a to 5c
, 18 are sequentially output to switch the power supply to the electrical / optical conversion block 12b of the optical transmitter / receiver 12 of the own station for a certain period of time, and then the nodes 2a to 2c other than the monitoring station node 1 are cut off.
The power supply to each communication control unit 11 'and the optical transmission / reception unit 12' is sequentially cut off for a certain period of time. Then, when the signal state of the optical transmission line 4 during the interruption of the power supply is normal, the node that interrupted the power supply is identified as the faulty node, and the power supply of the node is held in the stopped state. The faulty node is removed from the system to remove the abnormal signal from the optical transmission line 4, and the system is returned to the communicable state again.

In such a conventional optical communication system, communication is possible between nodes other than the faulty node, but post-fault communication is not possible between the faulty node and other nodes, and the system function is greatly reduced as a whole system. However, it is costly to wire the power switch control lines 5a to 5c between the monitoring station node and the other nodes only for detecting and removing the fault.

FIG. 8 and FIG. 9 show another conventionally known optical communication system, which is a star type optical communication system like the optical communication system shown in FIG. No power switch control line is provided. That is, in FIG. 9, each node 2d ...
2g are connected to each other by an optical transmission line 4'through a passive star coupler 3 ', and the configuration of each node 2d-2g is similar to that of FIG. 7 as shown in FIG. It differs from that of FIG. 7 in that the abnormality detection circuit 18 is provided in 2g. That is, in the optical communication system shown in FIG. 8 and FIG. 9, the operation control of the power switch 14 'is performed by the abnormality detection circuit 18 provided in each node, and the abnormality detection circuit 18 is provided in the optical transmission / reception unit 1.
It is connected to the 2'electrical / optical conversion block, always monitors for abnormalities such as continuous light emission of its own electrical / optical conversion block, and if an abnormality occurs in its own electrical / optical conversion block, it supplies power to its own station. Switch 14 'is operated to stop the power supply to the communication control unit 11' and the optical transmission / reception unit 12 'of its own station, and each node detects the abnormality itself and withdraws from the system. Is.

This optical communication system does not require a power switch control line wired between a monitoring station node and other nodes as in the system shown in FIGS. 5 to 7, but this optical communication system also has a faulty node and other nodes. Not only communication between nodes becomes impossible, but each node constantly monitors the operating status of its own electrical / optical conversion block, and detects an abnormal signal in the optical transmission line to turn off the power of its own station. Therefore, there is a problem that the system becomes expensive if such an abnormality detection circuit is provided in each node.

FIG. 10 and FIG. 11 show still another conventionally known optical communication system. This system has an optical transmission line, each node has two optical transmission / reception units and two communication control units, and each node 2h ... 2k is the first through the first passive star coupler 3a
Are connected to each other by the optical transmission line 4a (of the active system)
They are connected to each other via a second (standby system) optical transmission line 4b via a second passive star coupler 3b. Each node 2h-2k is configured as shown in FIG.
10a is switchably connected to each of the communication control units 11a and 11b of the active system and the standby system via the changeover switch 20, and the active system communication control unit 11a is connected to the active system optical transmission line 12A via the active system optical transmission / reception unit 12A. The standby system communication controller 11b is connected to the standby system optical transmission line 4b via the standby system optical transceiver 12B. When a failure occurs in the optical transmission line 4a of the working system, the changeover switch 20 is used to change the signal transmission path to the communication control unit 11
a, the active system via the optical transmission / reception unit 12A and the optical transmission line 4a is switched to the standby system via the communication control unit 11b, the optical transmission / reception unit 12B and the optical transmission line 4b to ensure communication between the nodes.

In this conventional optical communication system, it is necessary to duplicate all the constituent elements except the central control unit of each node, which causes a problem that the cost is significantly increased.

The present invention has been made to solve such a problem, and in an optical communication system in which a plurality of nodes are connected by an optical transmission line having a passive star coupler, continuous light emission and synchronization of an electric / optical conversion block can be obtained. It is an object of the present invention to provide a highly reliable fault detection / removal method for an optical communication system by avoiding an inability to communicate with the entire system due to an abnormal signal such as irregular light emission, which is inexpensive.

(Means for Solving the Problems) According to the present invention in order to achieve the above object, a plurality of nodes are connected to a common optical transmission line, and an optical transmission / reception unit of each node transmits an electric signal to a transmission signal. In a fault detection / removal method for an optical communication system that performs optical conversion and optical / electrical conversion to perform data communication between nodes, one of the plurality of nodes is a monitoring node, and the monitoring node and the remaining monitored nodes are connected to each other. An electrical signal transmission path is provided, the monitoring node monitors the optical transmission path to detect the occurrence of an abnormal signal, and when an abnormal signal occurs in the optical transmission path, the monitoring node is While monitoring the change in the signal state, the power supply to each optical transmission / reception unit of each monitored node is controlled to be turned on / off in a predetermined order through the electric signal transmission path to detect a faulty node, and the detected faulty node light is detected. Stop the power supply to the transceiver There is provided a method of detecting and removing a fault in an optical communication system, which is characterized in that the faulty node and the supervisory node are communicated using the electric signal transmission path while keeping the stopped state.

(Function) When an abnormal signal such as continuous light or irregular light emission that does not synchronize is generated in the optical transmission line, the monitoring node detects this abnormality,
While monitoring a change in the signal state of the optical transmission line, power supply to each optical transmission / reception unit of each monitored node is controlled to be turned on / off in a predetermined order via the electric signal transmission line. If the abnormality of the optical transmission line disappears when the power supply to the optical transceiver is stopped, it means that the monitored node that stopped the power supply has failed.
It becomes possible to detect a failed node. Then, the power supply to the optical transmission / reception unit of the faulty node is held in a stopped state to remove the faulty node from the optical transmission line and to enable communication between the nodes other than the faulty node via the optical transmission line, By communicating between a faulty node and another node via an electric signal transmission path, it is possible to avoid a significant decrease in system function and realize a highly reliable and inexpensive system.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

First, FIG. 3 shows a connection relation of each node of an optical communication system for carrying out the method of the present invention. A plurality of nodes, for example, four nodes 21, 22a to 22c, perform optical optical transmission in a radial direction via a passive star coupler 23. Connected by path 24. Monitoring station (master) of a specific node 21 among these multiple nodes
Nodes and the remaining nodes 22a to 22c as monitored nodes (slave nodes) are used as backup electrical signal transmission lines 25a to 25c from the master node 21 to the slave nodes 22a to 22c.
Are connected to each other. The master node 21 of the monitoring station is configured as shown in FIG. 1, and is a central control unit that executes the control peculiar to the master node 21, the failure of the optical transmission line 24, etc., and the control program for removing the failure. 30 is the optical transmission line 24
To the optical transmission / reception unit 32 via the communication control unit 31 that controls the data communication between the nodes performed via the
In addition, the optical transmitter / receiver 32 is connected to the decoder 45, and
The electrical / electrical conversion block 32a for converting the optical communication input from 24 into an electrical signal and the electrical signal from the communication control unit 31 are converted into an optical signal, and the transmission signal to another node is output to the optical transmission line 24. -It is composed of the light conversion block 32b.

A driver 41 is connected to the output side of the encoder 40, and a receiver 44 is connected to the input side of the decoder 45, and the driver 41 and the receiver 44 are connected to a communication node changeover switch 43 via a changeover switch 42. The electric signal transmission paths 25a to 25c are connected to the communication node changeover switch 43. The electric / optical conversion block 32b is supplied with power from a power supply 33 via a power switch 34 and a power supply line 36, and the other components except the electric / optical conversion block 32b are directly supplied with power from the power supply 33 via a power supply line 35. It

The power switch 34, the changeover switch 42, and the communication node changeover switch 43 are connected to the central control unit 30 via the switch changeover control lines 38, 46, 47, respectively, and these switches 34, 42, 43 are connected.
Are controlled by the central control unit 30.

On the other hand, the slave nodes 22a to 22c are configured as shown in FIG. 2, respectively, and are controlled by the individual nodes 22a (22b, 22c) and the electrical signal transmission paths 25a (25b, 25c) described later. Central control unit 30 'that controls data communication between nodes
Is an electrical transmission signal of the transmission signal via the communication control unit 31 ′ which controls the data communication between the nodes using the optical transmission line 24 as the transmission route.
The optical transmitter / receiver 32 'is connected to the optical transmitter / receiver 32' which performs optical conversion and optical-electrical conversion, and the encoder 40 'and the decoder 45'. The optical transmitter / receiver 32 is connected to the optical transmission line 24.

A driver 41 'is connected to the output side of the encoder 40' and a receiver 44 'is connected to the input side of the decoder 45'. These driver 41 'and receiver 44' transmit electric signals via a changeover switch 42 '. It is connected to the path 25a (25b, 25c). The optical transmitter / receiver 32 'and the communication controller 31' have a power source 3
Power is supplied from 3'through a power switch 34 'and a power supply line 36', and the other components except the optical transmission / reception unit 32 'and the communication control unit 31' are supplied from a power supply 33 'through a power supply line 35'. Directly powered.

The power switch 34 'and the changeover switch 42' are connected to the central control unit 30 'via switch changeover control lines 38' and 46 ', respectively, and these switches 34' and 42 'are changed over by the central control unit 30'. The operation is controlled.

Next, a fault detection and removal procedure of the optical communication system configured as described above will be described with reference to FIG.

The central control unit 30 of the master node 21 includes an optical transmission line 24 via a communication control unit 31 and an optical / electrical conversion block 32a of an optical transmission / reception unit 32.
The signal state of each node is constantly monitored, and unless an abnormal signal such as continuous light or irregular light emission without synchronization is detected in the optical transmission line 24, the power switches 34 and 34 'of each node are set to the power supply position. The central control unit 30, 30 'of each node, the communication control unit 31, 31' and the optical transmission / reception unit 32, 3 are held in the state of being switched to
Data communication between the nodes is performed by 2'through the optical transmission line 24 (refer to time t0 in FIG. 4A).

On the other hand, when the central control unit 30 of the master node 21 detects that an abnormal signal of the optical transmission line 24 has occurred for a predetermined time T (now, the slave node 22c fails and the optical transmission / reception unit 32 of the node 22c). Assuming that the electrical / optical conversion block of ′ outputs an abnormal signal of continuous light to the optical transmission line 24, FIG. 4 (f)
When a predetermined time T elapses from the time point when the node 22c starts outputting continuous light, the central control unit 30 determines that an abnormality has occurred in the optical transmission line 24, and the switch switching control of its own node is performed. A switching signal is output to the line 46 to switch the switching switch 42 to the transmission mode to connect the communication node switching switch 43 and the driver 41, and then the switch switching control line 47.
A switching signal is also output to switch the communication node changeover switch 43, and the electric signal transmission path 25a connected to the slave node 22a is switched and selected so that communication with the slave node 22a is possible.

Next, the central control unit 30 controls the communication control unit 31 'of the slave node 22a via the encoder 40, the driver 41, the changeover switch 42, the communication node changeover switch 43, and the electric signal transmission path 25a.
And a power supply control signal Sa for stopping power supply to the optical transmitter / receiver 32 '.
1 is output (see FIG. 4 (g)). Slave node 22a
The changeover switch 42 'of the power supply control signal transmitted from the master node 21 is switched to the normal reception mode.
Sa1 is input to the central control unit 30 'of the slave node 22a via the receiver 44' and the decoder 45 '. Then, the central control unit 30 'outputs a switching signal to the switch switching control line 38' and turns off the power supply switch 34 'to supply power from the power source 33' to the communication control unit 31 'and the optical transmission / reception unit 32'. Stop over time (see Fig. 4 (b), power switch)
When the switching signal to 34 'is high level, power supply is stopped). At this time, the central control unit 30 of the master node 21 is monitoring the signal state of the optical transmission line 24, and if there is no change in the signal state, the communication control unit 31 'and the optical transmission / reception unit 32' of the slave node 22a are not abnormal. When it is determined that there is no communication, the communication control unit 31 'and the optical transmission / reception unit 3 of the slave node 22a are connected to the electric signal transmission line 25a.
A power supply control signal Sa2 for restarting power supply to 2'is output (see FIG. 4 (g)). Central control unit 3 of slave node 22a
0'receives the power supply control signal Sa2 transmitted from the master node 21 via the electric signal transmission line 25a, outputs a switching signal to the switch switching control line 38 ', and turns on the power switch 34' to turn on the power supply 33. ′ To communication controller 31 ′ and optical transceiver
The power supply to 32 'is restarted (see Fig. 4 (h)).

Next, the central control unit 30 of the master node 21 outputs a switching signal to the switch switching control line 47 to output the communication node switching switch 43.
After switching the electrical signal transmission path 25b connected to the slave node 22b to make it possible to communicate with the slave node 22b, the power supply control signal Sb1 and power supply for stopping the power supply to the slave node 22b as well as the slave node 22a Then, the power supply control signal Sb2 for restarting the operation is sequentially output to confirm that there is no abnormality in the communication control unit 31 'and the optical transmission / reception unit 32' of the slave node 22b (see FIGS. 4 (i) and (j)).

When the power supply control signal Sc1 for stopping the power supply is supplied to the failed slave node 22c through the electric signal transmission line 25c (see (k) in FIG. 4), the central control unit 30 'of the slave node 22c.
Outputs a switching signal to the switch switching control line 38 'and causes the power switch 34' to turn off so that the power supply 33 'causes the communication control unit 31'.
Also, the power supply to the optical transmitter / receiver 32 'is stopped. When the power supply to the optical transmission / reception unit 32 'of the slave node 22c is stopped, the power supply to the electric / optical conversion block of the optical transmission / reception unit 32' in an abnormal state such as continuous light emission is stopped, so that the electric / optical conversion is performed. The block does not emit light, and the signal state of the optical transmission line 24 becomes no signal (see time t1 in FIGS. 4A, 4F, and 1). When the central control unit 30 of the master node 21 detects the change in the signal state of the optical transmission line 24, it is determined that there is an abnormality in either the communication control unit 31 'or the optical transmission / reception unit 32' of the slave node 22c. In this case, the central control unit 30 of the master node 21 does not output the power supply control signal for resuming power supply to the slave node 22c, and the communication control unit 3 of the slave node 22c
The state in which the power supply to the 1'and the optical transmitter / receiver 32 'is stopped is maintained (see FIG. 4 (1)). In this way, the failure of the optical transmission line 24 is detected, and this is eliminated, and the communication via the optical transmission line 24 becomes possible again, and the faulty slave node
Data communication via the optical transmission line 24 between the master node 21 and the slave nodes 22a and 22b other than 22c is restarted (fourth
After time t2 in Fig. (A)).

On the other hand, the failed slave node 22c is connected to the electrical signal transmission line 25c.
It is possible to communicate with the master node 21 via the. That is, when the master node 21 detects an abnormality in the slave node 22c,
After that, when communication is required between the master node 21 and the slave node 22c, the communication node changeover switch 43 is caused to switch and select the electric signal transmission path 25c to make it possible to communicate with the slave node 22c, and then the changeover switch 42 of the own node is changed. The transmission mode and the reception mode are sequentially switched, and the slave node 22c side is also controlled to sequentially switch the changeover switch 42 'to the reception mode and the transmission mode, and the encoders 40, 40', the drivers 41, 41 'of the nodes 21 and 22c, The receiver 44, 44 'and the decoder 45, 45' encode and equalize and amplify a transmission signal into an appropriate signal, and transmit / receive between the central control units 30, 30 '. At this time, the signal transmission speed of the electric signal transmission path 25a is slower than the transmission speed of the optical transmission path 24, or even at the same signal transmission speed, since the overhead for error checking is large, the master node 21 and the slave node 22c The transmission signal transmitted / received in (1) may be limited to only the minimum data required for system control or the like.

When the cause of the abnormal signal is in the master node 21, the power switch 34 of the own node 21 is turned off to stop the power supply to the electric / optical conversion block 32a to detect the abnormality of the own node. It is possible. In this case, the electric signal transmission lines 25a to 25c are used for communication between the master node and the slave node, and the transmission between the slave nodes is performed by the optical transmission line 24 as in the conventional case.

(Effects of the Invention) According to the failure detection / removal method for an optical communication system of the present invention as described in detail above, one of a plurality of nodes is set as a monitoring node, and between the monitoring node and the remaining monitored nodes. An electrical signal transmission path is installed in the monitoring node, the monitoring node monitors the electrical signal transmission path to detect the occurrence of an abnormal signal, and when an abnormal signal occurs in the optical transmission path, the monitoring node determines the signal status of the optical transmission path. While monitoring the optical signal transmission path to each optical transmission / reception unit of each monitored node, each power supply is turned on / off in a predetermined order to detect a faulty node, and the optical transmission / reception unit of the detected faulty node is detected. The power supply is maintained in a stopped state, and the electric signal transmission line is used to communicate with the faulty node. The electric signal transmission line is used for three purposes: detection of a fault, elimination thereof, and signal backup transmission after the elimination of the fault. Available for Therefore, it has an excellent effect that a highly reliable optical communication system can be realized at low cost.

Further, although the monitoring node is provided, the instruction from the monitoring node to each monitored node is performed via another transmission path, so that there is an effect that it is possible to cope with the abnormality of the monitoring node.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, FIG. 1 is a block diagram showing an internal configuration of a master node (monitoring node) of an optical communication system for implementing the method of the present invention, and FIG. FIG. 4 is a block diagram showing an internal configuration of a slave node (monitored node) of an optical communication system for implementing the method of the invention, FIG. 3 is a block diagram showing an overall configuration of an optical communication system for implementing the method of the present invention, and FIG. Timing charts for explaining fault / detection and removal procedures of an optical communication system according to the method of the invention, FIGS. 5 to 11 show various conventional optical communication systems, and FIG. 5 shows a conventional star-type optical system. 6 is an overall configuration diagram of the communication system, FIG. 6 is a circuit diagram showing an internal configuration of the monitoring node 1 in FIG. 5, FIG. 7 is a circuit diagram showing an internal configuration of a node other than the monitoring node in FIG. 5, and FIG. Has an anomaly detection circuit on each node FIG. 9 is a circuit diagram showing the internal configuration of each node of another conventional optical communication system. FIG. 9 shows a state in which a plurality of nodes shown in FIG. 8 are connected by an optical transmission line 4 '. Overall configuration block diagram of the system,
FIG. 10 is a block diagram showing the overall configuration of still another conventional optical communication system, and FIG. 11 is a block diagram showing the internal configuration of each node 2h to 2k in FIG. 21 …… Master (monitoring) node, 22a, 22b, 22c …… Slave (monitored) node, 23 …… Passive star coupler, 24
...... Optical transmission line, 25a to 25c ...... Electrical signal transmission line, 30,30 '
...... Central control unit, 31,31 '...... Communication control unit, 32,32' ......
Optical transmitter / receiver, 33 ... Power supply, 34 ... Power switch, 42, 4
2 '... Changeover switch, 43 ... Communication node changeover switch.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kei Inoue, 2-9-15 Futaba, Shinagawa-ku, Tokyo Furukawa Electric Co., Ltd. Central Research Laboratory (72) Shoji Hara 2-9, Futaba, Shinagawa-ku, Tokyo No. 15 Central Research Laboratory, Furukawa Electric Co., Ltd. (56) Reference JP-A-58-51647 (JP, A)

Claims (1)

[Claims] 1. An optical communication system in which a plurality of nodes are connected to a common optical transmission line, and optical transmission / reception units of the nodes electrically / optically switch and optical / electrically convert transmission signals to perform data communication between the nodes. In the failure detection / removal method, one of the plurality of nodes is a monitoring node, the monitoring node and the remaining monitored nodes each have an electric signal transmitting / receiving unit, and the electric signal transmitting / receiving unit of the monitoring node and the remaining An electrical signal transmission / reception unit of the monitored node is connected through an electrical signal transmission line, and the monitoring node monitors the optical transmission line to detect the occurrence of an abnormal signal, and an abnormal signal is generated in the optical transmission line. At this time, the monitoring node performs on / off control in a predetermined order to supply power to each optical transmission / reception unit of each monitored node via the electric signal transmission line while monitoring a change in a signal state of the optical transmission line, and a failure occurs. Node An optical communication system characterized by detecting and holding the power supply to the optical transceiver of the detected faulty node in a stopped state, and performing communication between the faulty node and the monitoring node via the electrical signal transmission path. Failure detection / removal method.