Communication system, communication device, abnormality handling method, and program

Abstract

A communication device according to the present invention is provided with: a redundant terminal device that terminates a main signal relating to a subordinate device; and a communication unit that relays the main signal relating to the subordinate device between another communication device connected via a first communication path and the terminal device. Upon detecting an abnormality in an active terminal device, the communication device notifies the other communication device of the occurrence of the abormality via the first communication path. Furthermore, the communication device notifies a monitoring control device of the occurrence of the abnormality via a second communication path. The communication device switches a reserve terminal device to the active terminal device on the basis of setting information received from the other communication device or the monitoring control device.

Description

[Technical Field]

[0001] The present invention relates to a communication system, a communication device, an abnormality handling method, and a program. Regarding. [Background technology]

[0002] PON protection is a technology to improve the reliability of PON (Passive Optical Network), which provides redundancy to the devices that make up the PON.

[0003] An OLT (Optical Line Terminal, an optical subscriber line communication system) has N+1 OSUs (Optical Subscriber Units) inside. Each of the N OSUs is connected to an ONU (Optical Network Unit) via a different PON line. The OSU terminates the optical signals between the ONUs. Some of the N OSUs are used as active systems, and the rest are used as redundant systems. If an active OSU stops working due to a failure or other reason, the OLT can switch the ONU's connection to a standby OSU via an N×(N+1) optical switch. By switching to the standby OSU, the OLT can continue communication without interrupting the service it provides to the ONU.

[0004] If an abnormality occurs in the OSU of the working system, the abnormality is dealt with in the following procedure. First, the control panel equipped in the OLT acquires the setting information of the OSU where the abnormality occurred. Next, the control panel sends this setting information to the OSU of the backup system to be switched to, and also sends a command to switch the line to the optical selector. After the setting of the OSU of the switching destination and the line switching by the optical selector are completed, the control panel commands the OSU to emit light. This allows the OLT to switch the OSU of the working system. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2013 / 058179 Summary of the Invention [Problem to be solved by the invention]

[0006] Rural areas often have poor transportation access, and if maintenance personnel need to work in rural areas to troubleshoot a failure, recovery may take time. Therefore, it is desirable to provide a PON protection function in the OLT that can autonomously handle abnormalities. Furthermore, it is necessary to prevent PON protection from becoming unavailable if an abnormality occurs in the configuration that realizes the PON protection function.

[0007] In view of the above circumstances, the present invention aims to provide a communication system, a communication device, an abnormality handling method, and a program that can switch a backup device to a working device even when multiple abnormalities occur. [Means for solving the problem]

[0008] One aspect of the present invention is a communication system comprising a first communication device, a second communication device connected to the first communication device via a first communication path, and a monitoring control device connected to the first communication device and the second communication device via a second communication path different from the first communication path, wherein the first communication device comprises a switch for transmitting and receiving main signals related to a first lower-level device and a second lower-level device with a higher-level device, a first termination device for terminating the main signals related to the first lower-level device, a first transfer device for relaying the main signals related to the second lower-level device between the switch and the second communication device via the first communication path, and a first control unit for controlling the second communication device, and the second communication device comprises a redundant second termination device for terminating the main signals related to the second lower-level device, and a transfer device for relaying the main signals related to the second lower-level device between the first communication device and the second termination device via the first communication path. A communication system comprising: a second transfer device; a switching unit that switches a second terminal device of a standby system among the redundant second terminal devices to a working system; and a second control unit that controls the second communication device; when the second control unit detects an abnormality in the second terminal device of the working system, it notifies the first communication device of the occurrence of the abnormality via the first communication path and notifies the monitoring and control device of the occurrence of the abnormality via the second communication path; when the first control unit is notified of the occurrence of the abnormality in the second terminal device, it transmits setting information required to switch the second terminal device via the first communication path; when the monitoring and control device is notified of the occurrence of the abnormality in the second terminal device, it transmits the setting information via the second communication path; and the switching unit switches the second terminal device of the standby system to the working system based on the setting information received from the first communication device or the monitoring and control device.

[0009] One aspect of the present invention is a communication device comprising: a redundant termination device that terminates a main signal related to a lower-level device; a communication unit that relays the main signal related to the lower-level device between the termination device and another communication device connected via a first communication path; a control unit that, when an abnormality is detected in the termination device of a current system, notifies the first communication device of the occurrence of the abnormality via the first communication path or notifies a monitoring control device of the occurrence of the abnormality via a second communication path; and a switching unit that switches the termination device of a standby system to a current system based on setting information received from the communication device or the monitoring control device.

[0010] One aspect of the present invention is a method for dealing with an abnormality in a communication system including a first communication device having a switch for transmitting and receiving main signals related to a first lower device and a second lower device with a higher device, and a first termination device for terminating the main signals related to the first lower device, a transfer device for transferring the main signals related to the second lower device to and from the first communication device via a first communication path, and a second communication device having a redundant second termination device for terminating the main signals related to the second lower device, and a monitoring control device connected to the first communication device and the second communication device via a second communication path different from the first communication path, wherein when the second communication device detects an abnormality in the second termination device, the second communication device notifies the occurrence of the abnormality via the first communication path. a step of notifying the first communication device of an abnormality in the second terminal device, when the second communication device detects an abnormality in the second terminal device, notifying the monitoring and control device of the occurrence of the abnormality via the second communication path; a step of the first communication device, when notified of the occurrence of the abnormality in the second terminal device, transmitting setting information required for switching the second terminal device via the first communication path; a step of the monitoring and control device, when notified of the occurrence of the abnormality in the second terminal device, transmitting the setting information via the second communication path; and a method of switching the second terminal device of the standby system to the working system by the second communication device based on the setting information received from the first communication device or the monitoring and control device.

[0011] One aspect of the present invention is a program for causing a computer of a communication device that includes a redundant termination device that terminates a main signal related to a lower-level device, and a transfer unit that relays the main signal related to the lower-level device between the termination device and another communication device connected via a first communication path, to function as a control unit that, when an abnormality is detected in the termination device of the current system, notifies the first communication device of the occurrence of the abnormality via the first communication path and notifies a monitoring control device of the occurrence of the abnormality via a second communication path, and a switching unit that switches the termination device of the standby system to the current system based on configuration information received from the communication device or the monitoring control device. [Effects of the Invention]

[0012] According to the present invention, even if multiple abnormalities occur in communication devices installed in rural areas, it is possible to switch the standby system equipment to the working system. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 illustrates an example of the configuration of a communication system according to a first embodiment. [Figure 2] 6 is a flowchart illustrating an operation of a slave station when an abnormality occurs according to the first embodiment. [Figure 3] 5 is a flowchart showing the operation of the master station according to the first embodiment. [Figure 4] 4 is a flowchart showing a monitoring operation of a slave station by the monitoring control device according to the first embodiment. [Figure 5] FIG. 10 is a sequence diagram showing the operation of a communication system in a first specific example. [Figure 6] FIG. 10 is a sequence diagram showing the operation of a communication system in a second specific example. [Figure 7] FIG. 10 is a schematic block diagram showing the configuration of a communication system according to a second embodiment. [Figure 8] FIG. 10 is a sequence diagram showing the operation of a communication system in a third specific example. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the same parts in the drawings are designated by the same reference numerals, and the description thereof will be omitted.

[0015] The communication system of the embodiment has a configuration in which a plurality of OLTs or OSUs, which are partial functions of the OLTs, are hierarchically connected. The hierarchically connected OLTs have a relationship between a master station and a slave station. The OLT of the master station (hereinafter referred to as the master station) and the OLT of the slave station (hereinafter referred to as the slave station) are equipped with a control panel and a transfer PKG (package). The transfer PKG transfers main signals between the slave stations and the master station via a main signal line. The transfer PKG also has a control unit and has the function of sending and receiving control signals used by the control panel. The communication system also has a monitoring and control device that monitors the OLTs including the master station and the slave stations. The OLTs and the monitoring and control system are each connected via a control line different from the main signal line.

[0016] As a result, if an abnormality occurs in the active PON-PKG of the slave station, the slave station can receive setting information from the control panel of the master station to switch the standby PON-PKG to the active system, and can also receive setting information from the monitor and control device to switch the standby PON-PKG to the active system.In other words, if an abnormality occurs in the active PON-PKG as well as in communication with the master station, the slave station can attempt to restore communication based on the setting information from the monitor and control device.Furthermore, if an abnormality occurs in the active PON-PKG as well as in communication with the monitor and control device, the slave station can attempt to restore communication based on the setting information from the master station.

[0017] First Embodiment FIG. 1 is a diagram illustrating an example configuration of a communication system 1 according to a first embodiment. The communication system 1 includes an OLT in a remote configuration. The communication system 1 includes a master station 100, a slave station 300, and a monitoring and control device 500. The master station 100 is an example of a first communication device, and the slave station 300 is an example of a second communication device. The master station 100 may be connected to multiple slave stations 300, and the slave station 300 may be connected to a lower-level slave station 300. The master station 100 may be installed in an urban area, and the slave station 300 may be installed in a rural area. The monitoring and control device 500 monitors and controls the master station 100 and the slave station 300.

[0018] The master station 100 is connected to a lower-level device 7-1 via an optical transmission path, and the slave station 300 is connected to a lower-level device 7-2 via an optical transmission path. The lower-level devices 7-1 and 7-2 are collectively referred to as lower-level devices 7. The lower-level device 7-1 is an example of a first lower-level device. The lower-level device 7-2 is an example of a second lower-level device. The lower-level device 7 is, for example, an ONU. The master station 100 is also connected to a higher-level device 8. The communication system 1 converts optical signals transmitted from the lower-level device 7 into electrical signals and forwards them to the higher-level device 8, and converts electrical signals transmitted from the higher-level device 8 into optical signals and forwards them to the lower-level device 7. The direction from the lower-level device 7 to the higher-level device 8 is referred to as upstream, and the direction from the higher-level device 8 to the lower-level device 7 is referred to as downstream.

[0019] The master station 100 includes a control PKG 110, a plurality of PON-PKGs 120, a transfer PKG 130, a switch 140, and an optical selector 200. The slave station 300 includes a control PKG 310 , a plurality of PON-PKGs 320 , a transfer PKG 330 , and an optical selector 400 .

[0020] The lower device 7-1 provided in the urban area is connected to the PON-PKG 120 of the parent station 100, and the lower device 7-2 provided in the rural area is connected to the PON-PKG 320 of the child station 300. The transfer PKG 130 and the transfer PKG 330 transfer main signals between the lower device 7-2 and the upper device 8 via a main signal line 250. The main signal line 250 is, for example, an optical transmission path such as an optical fiber. The main signal line 250 is an example of a first communication path.

[0021] <Configuration of master station 100> The PON-PKG 120 converts optical signals into electrical signals and vice versa. The PON-PKG 120 terminates optical signals between the lower-level device 7-1. For example, the PON-PKG 120 is equipped with a PON interface of an OSU. The electrical signal interface of the PON-PKG 120 is connected to the switch 140, and the optical signal interface is connected to the optical switch of the optical selector 200. Some of the multiple PON-PKGs 120 (M PON-PKGs 120) are used as active systems, and the remaining (N PON-PKGs 120) are used as standby systems. In a normal state where no abnormality occurs in any of the active PON-PKGs 120, the standby PON-PKG 120 is not connected to the lower-level device 7-1. The PON-PKG 120 is an example of a first termination device. The master station 100 does not necessarily have to include the PON-PKG 120.

[0022] The control PKG 110 is a control panel. The control PKG 110 monitors and controls each unit in the master station 100. If the control PKG 110 detects an abnormality in any of the PKGs, it executes PON protection. For example, if the control PKG 110 detects an abnormality in the active PON-PKG 120, it performs control to switch the connection destination of the lower-level device 7-1 that was connected to that PON-PKG 120 to the standby PON-PKG 120. The control PKG 110 is connected to the monitor and control device 500 via a control signal line 510. The control PKG 110 notifies the monitor and control device 500 of the state of the master station 100, and also receives instructions from the monitor and control device 500. Furthermore, when the control PKG 110 receives a PON protection instruction for the PON-PKG 320 from the monitoring control device 500, it transmits a control signal including setting information for the PON-PKG 320 to the slave station 300 that sent the notification, thereby performing PON protection for the slave station 300. The setting information includes information about the lower-level device 7-2 that should be accommodated in the switching destination PON-PKG 320, i.e., information about the lower-level device 7-2 accommodated in the active PON-PKG 320 in which the abnormality occurred. The control PKG 110 is an example of a first control unit.

[0023] The transfer PKG 130 relays an optical signal related to the lower device 7-2 between the higher-level device 8 and the slave station 300. That is, the transfer PKG 130 transfers an optical signal transmitted from the higher-level device 8 and destined for the lower device 7-2 to the slave station 300. The transfer PKG 130 also transfers an optical signal transmitted from the slave station 300 and destined for the lower device 7-2 to the higher-level device 8. The transfer PKG 130 also transmits a control signal to the slave station 300 via the main signal line 250. The transfer PKG 130 includes an internal control unit 131. The control unit 131 is independent of the control unit 111 in the control PKG 110. When an abnormality occurs in the active PON-PKG 320 of the slave station 300, the control PKG 110 transmits and receives a control signal to the slave station 300 via the transfer PKG 130, thereby realizing PON protection in the slave station 300. Note that the control signal may be transmitted using a control line different from the main signal line 250. The transfer PKG 130 is an example of a first transfer device.

[0024] The switch 140 has ports on both the primary side and the secondary side. The primary side ports are connected to multiple PON-PKGs 120 and transfer PKGs 130. Not only the active system PON-PKGs 120 but also the standby system PON-PKGs 120 are connected to the switch 140. The secondary side ports are connected to a higher-level device 8. The switch 140 relays electrical signals between the primary side ports and the secondary side ports. That is, the switch 140 transfers electrical signals received from the transfer PKGs 130 and PON-PKGs 120 to the higher-level device 8. The switch 140 also transfers electrical signals input from the higher-level device 8 to the transfer PKGs 130 or PON-PKGs 120 according to the destination of the electrical signal.

[0025] The optical selector 200 includes an optical switch 201 and a control unit 202. The control unit 202 sets the lines in the optical switch 201. The optical switch 201 has a primary-side port and a secondary-side port. The optical transmission lines connected to the main signal line 250 and the lower-level device 7-1 are connected to the secondary-side port. Multiple PON-PKGs 120 and transfer PKGs 130 are each connected to the secondary-side port. Not only the active system PON-PKGs 120 but also the standby system PON-PKGs 120 are connected to the optical switch 201. The optical switch 201 outputs an upstream optical signal input from the primary-side port to the secondary-side port and outputs a downstream optical signal input from the secondary-side port to the primary-side port, in accordance with the correspondence between the primary-side port and the secondary-side port indicated by the lines set by the control unit 202. Specifically, the optical switch 201 transfers the optical signal input from the transfer PKG 130 to the slave station 300 via the main signal line 250. The optical selector 200 transfers the optical signal input from the PON-PKG 120 of the working system to the corresponding lower-level device 7-1.

[0026] In another embodiment, the optical selector 200 may include multiple 2x2 splitters corresponding to the active PON-PKGs 120. The 2x2 splitter includes two ports on each of the primary and secondary sides, and outputs a signal input to the secondary side from each of the two ports on the primary side. The first port on the secondary side of the 2x2 splitter is connected to the active PON-PKG 120, and the lower-level device 7-1 is connected to the first port on the primary side, so that the active PON-PKG 120 may be connected to the lower-level device 7-1 without going through the optical switch 201. The second ports on the secondary sides of each 2x2 splitter are all connected to the primary-side port of the optical switch 201. The backup PON-PKG 120 is then connected to the secondary-side port of the optical switch 201. With this configuration, communication is possible without using the optical switch 201 during normal operation when the redundant PON-PKG 120 is not operating, and the optical switch 201 can be replaced without interrupting communication.

[0027] <Configuration of slave station 300> The slave station 300 includes a control PKG 310 , a plurality of PON-PKGs 320 , a transfer PKG 330 , and an optical selector 400 . The PON-PKG 320 converts optical signals into electrical signals and vice versa. The PON-PKG 320 terminates optical signals between the lower-level device 7-2. For example, the PON-PKG 320 is equipped with a PON interface of an OSU. The electrical signal interface of the PON-PKG 320 is connected to the transfer PKG 330, and the optical signal interface is connected to the optical switch 401 of the optical selector 400. Some of the multiple PON-PKGs 320 (M PON-PKGs 320) are used as active systems, and the remaining (N PON-PKGs 320) are used as standby systems. The standby PON-PKG 320 is not connected to the lower-level device 7-2 in a normal state in which no abnormality occurs in any of the active PON-PKGs 320. The PON-PKG 320 is an example of a second termination device.

[0028] The control PKG 310 is a control panel. The control PKG 310 monitors and controls each unit in the slave station 300. If the control PKG 310 detects an abnormality in any of the PKGs, it executes PON protection. For example, if the control PKG 310 detects an abnormality in the active PON-PKG 320, it performs control to switch the connection destination of the lower-level device 7-2 that was connected to that PON-PKG 320 to the standby PON-PKG 320. The control PKG 310 is connected to the monitor and control device 500 via a control signal line 530. The control signal line 530 is an example of a second communication path. The control PKG 310 notifies the monitor and control device 500 of the status of the slave station 300, and also receives instructions from the monitor and control device 500. Furthermore, when the control PKG 310 receives a control signal including setting information for the PON-PKG 320 from the monitor and control device 500, the control PKG 310 performs PON protection based on the setting information. The control PKG 310 is an example of a second control unit and a switching unit.

[0029] The transfer PKG 330 has a function of converting optical signals to and from electrical signals, and relays optical signals related to the lower device 7-2 between the master station 100 and the lower device 7-2. Specifically, the transfer PKG 330 converts optical signals transmitted from the master station 100 into electrical signals and transmits them to the corresponding PON-PKG 320, which then converts the electrical signals into optical signals and forwards them to the lower device 7-2. The transfer PKG 330 also forwards optical signals transmitted from the lower device 7-2 to the master station 100 via the PON-PKG 320. The transfer PKG 330 also transmits control signals to the master station 100 via the main signal line 250. The transfer PKG 330 is an example of a second transfer device. The transfer PKG 330 includes an internal control unit 331. The control unit 331 is independent of the control PKG 310. When an abnormality occurs in the PON-PKG 320, the control unit 331 receives a control signal including setting information from the master station 100 to implement PON protection. The control unit 331 is an example of a switching unit.

[0030] The optical selector 400 includes an optical switch 401 and a control unit 402. The control unit 402 sets the lines in the optical switch 401. The optical switch 401 has a primary-side port and a secondary-side port. The optical transmission line connected to the lower-level device 7-1 is connected to the primary-side port. Multiple PON-PKGs 320 are each connected to the secondary-side port. Not only the active system PON-PKGs 320 but also the standby system PON-PKGs 320 are connected to the optical switch 401. The optical switch 401 outputs an upstream optical signal input from the primary-side port to the secondary-side port and outputs a downstream optical signal input from the secondary-side port to the primary-side port, in accordance with the correspondence between the primary-side port and the secondary-side port indicated by the lines set by the control unit 402. Specifically, the optical switch 401 forwards the optical signal input from the lower-level device 7-2 to the corresponding forwarding PKG 330. The optical selector 200 forwards the optical signal input from the active system PON-PKG 120 to the corresponding lower-level device 7-2.

[0031] In another embodiment, the optical selector 400 may include a plurality of 2x2 splitters corresponding to the active PON-PKG 320. The first port on the secondary side of the 2x2 splitter is connected to the active PON-PKG 320, and the lower-level device 7-2 is connected to the first port on the primary side, so that the active PON-PKG 320 may be connected to the lower-level device 7-2 without going through the optical switch 401. The second port on the secondary side of each 2x2 splitter is all connected to a port on the primary side of the optical switch 401. The backup PON-PKG 320 is then connected to a port on the secondary side of the optical switch 401. With this configuration, during normal operation when the redundant PON-PKG 320 is not operating, communication is possible without using the optical switch 401, and the optical switch 401 can be replaced without stopping communication.

[0032] <<Monitoring and Control Device 500>> The monitoring control device 500 is connected to the master station 100 via a control signal line 510, and is connected to the slave station 300 via a control signal line 530. The monitoring control device 500 monitors the communication system 1 by receiving information indicating the status of the PKG from the master station 100 and the slave station 300. The monitoring control device 500 also manages accommodation information of the lower-level device 7. When the monitoring control device 500 receives a report of PON protection of the master station 100 or the slave station 300 from the master station 100, it updates the accommodation information of the lower-level device 7 based on the report. When the monitoring control device 500 receives a notification from the master station 100 indicating that an abnormality has occurred in the PON-PKG 120 of the active system, it transmits setting information for PON protection to the master station 100 and causes the control PKG 110 of the master station 100 to execute PON protection. When the monitoring control device 500 receives a notification from the slave station 300 indicating that an abnormality has occurred in the active PON-PKG 320, it transmits setting information for PON protection to the slave station 300 and causes the control PKG 310 of the slave station 300 to execute PON protection. The setting information includes information about the lower-level device 7-2 that should be accommodated in the switching destination PON-PKG 320, that is, information about the lower-level device 7-2 that is accommodated in the working PON-PKG 320 in which the abnormality has occurred.

[0033] <<Operation of slave station 300 when an error occurs>> FIG. 2 is a flowchart showing the operation of the slave station 300 when an abnormality occurs according to the first embodiment. The control PKG 310 of the slave station 300 monitors whether or not there is an abnormality in each PKG of the slave station 300. If an abnormality is confirmed in any of the PKGs, the control PKG 310 notifies the monitoring control device 500 of the occurrence of the abnormality. Furthermore, the control unit 331 of the transfer PKG 330 notifies the master station 100 of the occurrence of the abnormality (step S1). The notification to the master station 100 is made via the transfer PKG 330 and the main signal line 250. The notification to the monitoring control device 500 is made via the control signal line 530.

[0034] If an abnormality occurs in the active PON-PKG 320, the control PKG 310 waits to receive an instruction for PON protection from the monitor and control device 500 and determines whether the instruction has been received (step S2). If an instruction for PON protection is received from the monitor and control device 500 (step S2: YES), the control PKG 310 relays communication between the monitor and control device 500 and each PKG. First, when the control PKG 310 receives a switching preparation instruction from the monitor and control device 500, it outputs the switching preparation instruction to the active PON-PKG 320 in which the abnormality has occurred, the standby PON-PKG 320 to which the abnormality has occurred, and the optical selector 400 (step S3). When the optical selector 400 receives the switching preparation instruction, it switches the connection destination of the lower-level device 7-2 connected to the PON-PKG 320 in which the abnormality has occurred to the standby PON-PKG 320. When the switching is completed, the control unit 402 of the optical selector 400 outputs a notification of the completion of the switching to the control PKG 310. When the optical selector 400 completes the switching of the connection destination, the control PKG 310 transmits a notification of the completion of the switching to the monitor and control device 500.

[0035] When the control PKG 310 receives the setting information including information about the lower device 7-2 from the monitoring and control device 500, it outputs the setting information to the switching destination PON-PKG 320 of the standby system (step S4). The switching destination PON-PKG 320 configures the accommodated lower device 7-2 based on the setting information. When the configuration is complete, the PON-PKG 320 outputs a setting completion notification to the control PKG 310. When the configuration of the lower device 7-2 in the standby PON-PKG 320 is complete, the control PKG 310 transmits a setting completion notification to the monitoring and control device 500.

[0036] When the control PKG 310 receives the light emission stop instruction from the monitor and control device 500, the control PKG 310 outputs the light emission stop instruction to the PON-PKG 320 in which the abnormality occurred (step S5). As a result, the PON-PKG 320 in which the abnormality occurred stops light emission. When the PON-PKG 320 stops light emission, it outputs a stoppage completion notification to the control PKG 310. Then, the control PKG 310 transmits the stoppage completion notification to the monitor and control device 500.

[0037] When the control PKG 310 receives the light emission start instruction from the monitor and control device 500, the control PKG 310 outputs the light emission start instruction to the switching destination PON-PKG 320 (step S6). This causes the switching destination PON-PKG 320 to start emitting light. This switches the backup PON-PKG 320 to the active system. When the PON-PKG 320 starts emitting light, it outputs a start completion notification to the control PKG 310. The control PKG 310 then transmits the start completion notification to the monitor and control device 500.

[0038] On the other hand, if setting information for PON protection is not received from the monitor and control device 500 (step S2: NO), the control unit 331 of the transfer PKG 330 determines whether a control signal including an instruction for PON protection has been received from the master station 100 (step S7). If a control signal has been received from the master station 100 (step S7: YES), the control unit 331 of the transfer PKG 330 relays communication between the monitor and control device 500 and each PKG. First, when the control unit 331 of the transfer PKG 330 receives a switching preparation instruction from the master station 100, it outputs the switching preparation instruction to the working PON-PKG 320 in which the abnormality has occurred, the standby PON-PKG 320 to which the abnormality has occurred, and the optical selector 400 (step S8). When the optical selector 400 receives the switching preparation instruction, it switches the connection destination of the lower-level device 7-2 connected to the PON-PKG 320 in which the abnormality has occurred to the standby PON-PKG 320. When the switching is completed, the control unit 402 of the optical selector 400 outputs a notification of the completion of the switching to the control unit 331 of the transfer PKG 330. When the optical selector 400 completes the switching of the connection destination, the control unit 331 of the transfer PKG 330 transmits a notification of the completion of the switching to the master station 100.

[0039] When the setting information including information about the lower device 7-2 is received from the master station 100, the control unit 331 of the transfer PKG 330 outputs the setting information to the switching destination backup PON-PKG 320 (step S9). The switching destination PON-PKG 320 configures the accommodated lower device 7-2 based on the setting information. When the configuration is complete, the PON-PKG 320 outputs a setting completion notification to the control unit 331 of the transfer PKG 330. When the configuration of the lower device 7-2 in the backup PON-PKG 320 is complete, the control unit 331 of the transfer PKG 330 transmits a setting completion notification to the master station 100.

[0040] When receiving the light emission stop instruction from the master station 100, the control unit 331 of the transfer PKG 330 outputs the light emission stop instruction to the PON-PKG 320 in which the abnormality occurred (step S10). As a result, the PON-PKG 320 in which the abnormality occurred stops light emission. When the PON-PKG 320 stops light emission, it outputs a stoppage completion notification to the control unit 331 of the transfer PKG 330. The control unit 331 of the transfer PKG 330 then transmits the stoppage completion notification to the master station 100.

[0041] Upon receiving the light emission start instruction from the master station 100, the control unit 331 of the transfer PKG 330 outputs the light emission start instruction to the switching destination PON-PKG 320 (step S11). As a result, the switching destination PON-PKG 320 starts light emission. As a result, the backup PON-PKG 320 is switched to the active system. When the PON-PKG 320 starts light emission, it outputs a start completion notification to the control unit 331 of the transfer PKG 330. Then, the control unit 331 of the transfer PKG 330 transmits the start completion notification to the master station 100.

[0042] In this way, the slave station 300 can achieve PON protection based on instructions received from the monitor and control device 500 or the master station.

[0043] <<Operation of Master Station 100>> FIG. 3 is a flowchart showing the operation of the master station 100 according to the first embodiment. The control PKG 110 of the master station 100 determines whether or not it has received a control signal including a notification of a PKG abnormality from the slave station 300 (step S21). If it has received a control signal including a notification of a PKG abnormality from the slave station 300 (step S21: YES), it temporarily records information about the PKG abnormality in a storage device (step S22). The information about the PKG abnormality may be stored for a time period corresponding to the cycle of keep-alive communication by the monitoring control device 500, for example.

[0044] The control PKG 110 determines whether or not an inquiry about the status of the slave station 300 has been received from the monitoring control device 500 (step S23). If the control PKG 110 has received an inquiry about the status of the slave station 300 (step S23: YES), the control PKG 110 refers to the storage device and determines whether or not abnormality information has been received from the slave station 300 (step S24). If abnormality information has not been received from the slave station 300 (step S24: NO), the control PKG 110 notifies the monitoring control device 500 that there is no abnormality in the slave station 300 (step S25). On the other hand, if abnormality information has been received from the slave station 300 (step S24: YES), the control PKG 110 transfers the information about the abnormality in the slave station 300 to the monitoring control device 500 (step S26).

[0045] Thereafter, the control PKG 110 relays communication between the monitoring control device 500 and the slave station 300 via the transfer PKG 130. First, when the control PKG 110 receives a switching preparation instruction from the monitoring control device 500, it transmits the switching preparation instruction to the slave station 300 (step S27). When the control PKG 110 receives a switching completion notification from the slave station 300, it transmits this to the monitoring control device 500.

[0046] When the control PKG 110 receives the setting information including the information of the lower device 7-2 from the monitoring control device 500, it transmits the setting information to the slave station 300 (step S28). When the control PKG 110 receives a setting completion notification from the slave station 300, it transmits this to the monitoring control device 500.

[0047] When the control PKG 110 receives the light emission stop instruction from the monitor and control device 500, it transmits the light emission stop instruction to the slave station 300 (step S29). When the control PKG 110 receives a notification of the completion of the stop from the slave station 300, it transmits this to the monitor and control device 500.

[0048] When the control PKG 110 receives the light emission start instruction from the monitor control device 500, it transmits the light emission start instruction to the slave station 300 (step S30). When the control PKG 110 receives a notification of start completion from the slave station 300, it transmits this to the monitor control device 500.

[0049] <<Operation of the monitoring and control device 500>> FIG. 4 is a flowchart showing the monitoring operation of the slave station 300 by the monitoring control device 500 according to the first embodiment. The monitoring control device 500 determines whether communication with the slave station 300 is possible via the control signal line 530 (step S41). The monitoring control device 500 determines whether communication with the slave station 300 is possible, for example, by performing keep-alive communication with the slave station 300. If communication with the slave station 300 is possible (step S41: YES), the monitoring control device 500 determines whether a notification of a PKG abnormality has been received from the slave station 300 (step S42).

[0050] If a notification of a PKG abnormality is received from the slave station 300 (step S42: YES), the monitoring control device 500 updates the status of the slave station 300 stored in the storage device based on the received notification (step S43). Next, the monitoring control device 500 determines whether the abnormality indicated by the notification is an abnormality in the active PON-PKG 320 (step S44). If an abnormality is found in the active PON-PKG 320 (step S44: YES), the monitoring control device 500 transmits a switching preparation instruction to the slave station 300 (step S45). Upon receiving a switching completion notification from the slave station 300, the monitoring control device 500 reads, from the storage device, information related to the lower-level device 7-2 accommodated in the active PON-PKG 320 where the abnormality occurred, and generates setting information for setting this information in the standby PON-PKG 320 (step S46). The monitoring control device 500 transmits the setting information to the slave station 300 (step S47).

[0051] When the monitoring control device 500 receives a notification of the completion of the setting from the slave station 300, it transmits to the slave station 300 an instruction to stop light emission to stop the light emission of the working PON-PKG 320 where the abnormality occurred (step S48). When the monitoring control device 500 receives a notification of the completion of the stop from the slave station 300, it transmits to the slave station 300 an instruction to start light emission of the switching destination PON-PKG 320 (step S49).

[0052] On the other hand, if the monitoring control device 500 cannot communicate with the slave station 300 via the control signal line 530 (step S41: NO), there is a possibility that an abnormality has occurred in the control PKG 110 of the slave station 300 or the control signal line 530. In this case, the monitoring control device 500 transmits an inquiry about the status of the slave station 300 to the master station 100 (step S50). The monitoring control device 500 determines, in the response to the inquiry received from the master station 100, whether or not there is an abnormality in the PKG of the slave station 300 (step S51).

[0053] If an abnormality exists in the PKG of the slave station 300 (step S51: YES), the monitoring control device 500 updates the status of the slave station 300 stored in the storage device based on the received notification (step S52). Next, the monitoring control device 500 determines whether or not an abnormality exists in the active PON-PKG 320 (step S53). If an abnormality exists in the active PON-PKG 320 (step S53: YES), the monitoring control device 500 transmits a switching preparation instruction to the master station 100 (step S54). Upon receiving the switching completion notification from the master station 100, the monitoring control device 500 reads, from the storage device, information related to the lower-level device 7-2 accommodated in the active PON-PKG 320 where the abnormality occurred, and generates setting information for setting this information in the standby PON-PKG 320 (step S55). The monitoring control device 500 transmits the setting information to the master station 100 (step S56).

[0054] When the monitoring control device 500 receives the notification of completion of setting from the master station 100, it transmits to the master station 100 an instruction to stop light emission to stop light emission of the working PON-PKG 320 where the abnormality occurred (step S57). When the monitoring control device 500 receives the notification of completion of stop from the master station 100, it transmits to the master station 100 an instruction to start light emission of the switching destination PON-PKG 320 (step S58).

[0055] By having the master station 100, slave station 300, and monitoring control device 500 operate as described above, the communication system 1 can switch the PON-PKG 320 of the standby system of the slave station 300 to the active system even if a complex abnormality occurs in the slave station 300.

[0056] First Example Here, the processing of the communication system 1 will be described using specific examples. FIG. 5 is a sequence diagram showing the operation of the communication system 1 in a first specific example. In the first specific example, a case will be described where an abnormality occurs in the active PON-PKG 320 of the slave station 300 and in the control signal line 530. First, the slave station 300 notifies the master station 100 via the main signal line 250 that an abnormality has occurred in the active PON-PKG 320 (step S101). The slave station 300 also attempts to notify the monitoring control device 500 via the control signal line 530 that an abnormality has occurred in the active PON-PKG 320. In this case, since the abnormality has occurred in the control signal line 530, the notification does not reach the monitoring control device 500.

[0057] When the monitoring control device 500 detects that communication with the slave station 300 has become impossible, it transmits an inquiry about the status of the slave station 300 to the master station 100 (step S102). The control PKG 110 of the master station 100 transfers the notification of the abnormality received in step S101 to the monitoring control device 500 (step S103). This enables the monitoring control device 500 to recognize the abnormality in the active PON-PKG 320 of the slave station 300.

[0058] The monitoring control device 500 transmits a switching preparation instruction to the slave station 300 via the master station 100 and the main signal line 250 (step S104). As a result, the optical selector 400 of the slave station 300 executes line switching processing (step S105) and transmits a switching completion notification to the monitoring control device 500 via the master station 100 and the main signal line 250 (step S106).

[0059] The monitoring and control device 500 generates setting information for PON protection (step S107) and transmits the setting information to the slave station 300 via the master station 100 and the main signal line 250 (step S108). As a result, the PON-PKG 320 of the standby system, which is the switching destination of the slave station 300, sets information about the lower-level device 7-2 it accommodates, and transmits a setting completion notification to the monitoring and control device 500 via the master station 100 and the main signal line 250 (step S109).

[0060] The monitoring control device 500 transmits the light emission stop instruction to the slave station 300 via the master station 100 and the main signal line 250 (step S110). As a result, the PON-PKG 320, which is the switching source of the slave station 300, stops light emission and transmits a stop completion notification to the monitoring control device 500 via the master station 100 and the main signal line 250 (step S111).

[0061] The monitoring control device 500 transmits the light emission start instruction to the slave station 300 via the master station 100 and the main signal line 250 (step S112). As a result, the PON-PKG 320 to which the slave station 300 is switched starts light emission, and transmits a start completion notification to the monitoring control device 500 via the master station 100 and the main signal line 250 (step S113).

[0062] As described above, according to the first embodiment, even if a combined abnormality occurs in the active PON-PKG 320 of the slave station 300 and the control signal line 530, communication can be restored by PON protection.

[0063] Second Specific Example 6 is a sequence diagram showing the operation of the communication system 1 in the second specific example. In the second specific example, a case will be described in which an abnormality occurs in the active PON-PKG 320 of the slave station 300 and in the control unit 331 of the transfer PKG 330. First, the slave station 300 attempts to notify the master station 100 via the main signal line 250 that an abnormality has occurred in the active PON-PKG 320. In this case, because the abnormality has occurred in the control unit 331 of the transfer PKG 330, the slave station 300 cannot send the notification to the master station 100. The slave station 300 also notifies the monitoring control device 500 via the control signal line 530 that an abnormality has occurred in the active PON-PKG 320 (step S121).

[0064] When the monitoring control device 500 receives the abnormality notification from the slave station 300, it transmits a switching preparation instruction to the slave station 300 via the control signal line 530 (step S122). As a result, the optical selector 400 of the slave station 300 executes line switching processing (step S123), and transmits a switching completion notification to the monitoring control device 500 via the control signal line 530 (step S124).

[0065] The monitoring control device 500 generates setting information for PON protection (step S125) and transmits the setting information to the slave station 300 via the control signal line 530 (step S126). As a result, the PON-PKG 320 of the standby system, which is the switching destination of the slave station 300, sets information about the lower-level device 7-2 it accommodates, and transmits a setting completion notification to the monitoring control device 500 via the control signal line 530 (step S127).

[0066] The monitor and control device 500 transmits the light emission stop instruction to the slave station 300 via the control signal line 530 (step S128). As a result, the PON-PKG 320 from which the slave station 300 is switched stops light emission, and transmits a stop completion notification to the monitor and control device 500 via the control signal line 530 (step S129).

[0067] The monitoring control device 500 transmits a light emission start instruction to the slave station 300 via the control signal line 530 (step S130). As a result, the PON-PKG 320 to which the slave station 300 is switched starts light emission, and transmits a start completion notification to the monitoring control device 500 via the control signal line 530 (step S131).

[0068] As described above, according to the first embodiment, even if a combined abnormality occurs in the active PON-PKG 320 of the slave station 300 and the control unit 331 of the transfer PKG 330, communication can be restored by PON protection.

[0069] In addition to the above configuration, the control PKG 310 of the slave station 300 according to the first embodiment may have a function for autonomously realizing PON protection. In this case, PON protection can be realized even if control signals cannot be transmitted or received between the monitoring control device 500 and the master station 100. On the other hand, if the control PKG 310 does not have a function for autonomously realizing PON protection, the configuration can be simplified, which can contribute to the miniaturization of the slave station 300.

[0070] Second Embodiment FIG. 7 is a schematic block diagram showing the configuration of a communication system 1 according to the second embodiment. In the communication system 1 according to the second embodiment, the main signal line 250 connecting the transfer PKG 130 of the master station 100 and the transfer PKG 330 of the slave station 300 is made redundant by a plurality of links. In the communication system 1 according to the second embodiment, when an abnormality occurs in the working link of the main signal line 250, the standby link can be switched to the working link based on an instruction from the monitor and control device 500.

[0071] When the monitoring and control device 500 according to the second embodiment receives notification of an abnormality in the main signal line 250 from the master station 100 or the slave station 300, it transmits a link switching instruction to the master station 100. The control PKG 110 of the master station 100 transfers the link switching instruction to the control unit 131 of the transfer PKG 130, and the control unit 131 switches the link of the backup system to the link of the working system in accordance with the link switching instruction.

[0072] 《Third specific example》 Here, the processing of the communication system 1 will be described using a specific example. FIG. 8 is a sequence diagram showing the operation of the communication system 1 in a third specific example. In the third specific example, a case will be described in which an abnormality occurs in the active PON-PKG 320 of the slave station 300, the main signal line 250, and the control PKG 310. First, the slave station 300 attempts to notify the master station 100 via the main signal line 250 that an abnormality has occurred in the active PON-PKG 320. Here, because the abnormality has occurred in the main signal line 250, the notification does not reach the master station 100. The slave station 300 also attempts to notify the monitoring control device 500 via the control signal line 530 that an abnormality has occurred in the active PON-PKG 320. Here, because the abnormality has occurred in the control PKG 310, the notification cannot be sent to the monitoring control device 500.

[0073] Meanwhile, the transfer PKG 130 of the master station 100 detects an abnormality in the main signal line 250 because it is no longer able to communicate optical signals with the slave station 300. The control PKG 110 notifies the monitoring control device 500 of the abnormality in the main signal line 250 (step S201). Upon receiving the abnormality notification from the master station 100, the monitoring control device 500 transmits an instruction to switch the link of the main signal line 250 to the master station 100 (step S202). The control unit 131 of the transfer PKG 130 of the master station 100 executes processing to switch the link of the backup system to the link of the working system based on the received switching instruction with the transfer PKG of the slave station 300 (step S203).

[0074] When the main signal line 250 is restored, the transfer PKG 330 of the slave station 300 transmits a notice of the abnormality in the active PON-PKG 320 to the master station 100 (step S204). The slave station 300 also attempts to notify the monitoring control device 500 of the occurrence of the abnormality via the control signal line 530. In this case, because the abnormality has occurred in the control PKG 310, it is not possible to transmit a notice to the monitoring control device 500. When the monitoring control device 500 detects that communication with the slave station 300 has become impossible, it transmits an inquiry about the status of the slave station 300 to the master station 100 (step S205). The control PKG 110 of the master station 100 transfers the notification of the abnormality received in step S204 to the monitoring control device 500 (step S206). This enables the monitoring control device 500 to recognize the abnormality in the active PON-PKG 320 of the slave station 300.

[0075] The monitoring control device 500 transmits a switching preparation instruction to the slave station 300 via the master station 100 and the main signal line 250 after the link switching (step S207). As a result, the optical selector 400 of the slave station 300 executes line switching processing (step S208) and transmits a switching completion notification to the monitoring control device 500 via the master station 100 and the main signal line 250 (step S209).

[0076] The monitoring and control device 500 generates setting information for PON protection (step S210) and transmits the setting information to the slave station 300 via the master station 100 and the main signal line 250 (step S211). As a result, the PON-PKG 320 of the standby system, which is the switching destination of the slave station 300, sets information about the lower-level device 7-2 it accommodates, and transmits a setting completion notification to the monitoring and control device 500 via the master station 100 and the main signal line 250 (step S212).

[0077] The monitoring control device 500 transmits the light emission stop instruction to the slave station 300 via the master station 100 and the main signal line 250 (step S213). As a result, the PON-PKG 320, which is the switching source of the slave station 300, stops light emission and transmits a stop completion notification to the monitoring control device 500 via the master station 100 and the main signal line 250 (step S214).

[0078] The monitoring control device 500 transmits the light emission start instruction to the slave station 300 via the master station 100 and the main signal line 250 (step S215). As a result, the PON-PKG 320 to which the slave station 300 is switched starts light emission, and transmits a start completion notification to the monitoring control device 500 via the master station 100 and the main signal line 250 (step S216).

[0079] Thus, according to the second embodiment, even if a complex abnormality occurs in the active PON-PKG 320 of the slave station 300, the main signal line 250, and the control PKG 310, communication can be restored by PON protection.

[0080] Third Embodiment In the communication system 1 according to the third embodiment, the control unit 331 of the transfer PKG 330 of the slave station 300 stores setting information for PON protection. This allows the communication system 1 according to the third embodiment to perform PON protection without waiting for the transfer of setting information from the master station.

[0081] The slave station 300 according to the third embodiment may further record a copy of the setting information stored by the control unit 331 in advance in each PON-PKG 320. In other words, by always recording the setting information of the switching source PON-PKG 320 in the PON-PKG 320 that is a candidate for switching destination, it is possible to omit the process of transferring the setting information and shorten the time required for PON protection.

[0082] Furthermore, in the communication system 1 according to the third embodiment, the transfer PKG 330 of the slave station 300 voluntarily transmits a light emission stop instruction and an issuance start instruction to the PON-PKG 320. After completing PON protection, the transfer PKG 330 notifies the master station 100 and the monitoring control device 500 of the execution result of PON protection.

[0083] <Computer Configuration> The above-described control PKG 110, control unit 131, control PKG 310, and control unit 331 may each include a processor, memory, auxiliary storage device, and the like, connected via a bus, and the processor may execute a program to realize the above functions. The processor may be, for example, a central processing unit (CPU) or a graphics processing unit (GPU). Note that all or part of the functions of the control PKG 110, control unit 131, control PKG 310, and control unit 331 may be realized using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA). The programs for the control PKG 110, control unit 131, control PKG 310, and control unit 331 may be recorded on a computer-readable recording medium. Examples of the computer-readable recording medium include portable media such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and storage devices such as a hard disk built into a computer system. The programs of the control package 110, the control unit 131, the control package 310, and the control unit 331 may be transmitted via a telecommunications line.

[0084] Other Embodiments Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment and includes designs within the scope of the gist of the present invention. For example, the control unit 331 of the transfer PKG 330 of the slave station 300 according to the above-described embodiment has a function of transferring instructions, such as a switching preparation instruction, setting information, an instruction to stop light emission, and an instruction to start light emission, to each PKG based on instructions included in a control signal, but this is not limited to this. For example, the control unit 331 according to other embodiments may simply have a function of sending and receiving control signals. In this case, the control PKG 310 may control each PKG based on instructions received by the transfer PKG 330. In this case, communication can be restored when an abnormality occurs not only in the transfer PKG 130 but also in the main signal line 250 or the control signal line 530. However, communication cannot be restored when an abnormality occurs in the control PKG 310, as shown in FIG. 8.

[0085] Furthermore, the control unit 331 of the control PKG 310 or the transfer PKG 330 according to other embodiments may store in advance the setting information of the active PON-PKG 320. In this case, it is possible to switch the PON-PKG 320 without waiting for the setting information to be transferred from the monitoring control device 500.

[0086] Furthermore, although the communication system 1 according to the above-described embodiment switches the PON-PKG 320 based on an instruction from the monitor and control device 500, this is not limiting. For example, the master station 100 according to another embodiment may autonomously control the switching of the PON-PKG 120 of the master station 100 and the PON-PKG 320 of the slave station 300. In this case, the control PKG 110 of the master station 100 reports the completion of the switching to the monitor and control device 500 after the switching is performed.

[0087] Furthermore, although the communication system 1 according to the above-described embodiment transmits and receives optical signals between the master station 100 and the slave station 300, this is not limiting. For example, a communication system 1 according to another embodiment may transmit and receive electrical signals between the master station 100 and the slave station 300. In this case, the master station 100 includes a transfer device for electrical signals instead of the optical selector 200, and a relay device for electrical signals instead of the PON-PKG 120 and the transfer PKG 130. The transfer device transfers electrical signals transmitted from the relay device to a transfer destination (the slave station 300 or the lower-level device 7-1) corresponding to the relay device, and transfers electrical signals transmitted from the slave station 300 or the lower-level device 7-1 to the corresponding relay device. The relay device relays electrical signals between the switch 140 and the transfer device.

[0088] Furthermore, although the communication system 1 according to the above-described embodiment transmits and receives electrical signals between the host device 8 and the master station 100, this is not limiting. For example, a communication system 1 according to another embodiment may transmit and receive optical signals between the host device 8 and the master station 100. For example, the master station 100 may include an optical switch for forwarding optical signals instead of the switch 140, and an optical signal relay device instead of the PON-PKG 120 and the transfer PKG 130. The optical switch forwards optical signals transmitted from the relay device to the host device 8, and forwards optical signals transmitted from the host device 8 to a relay device corresponding to the destination of the optical signal. The relay device relays optical signals between the optical switch and the optical selector 200.

[0089] Furthermore, although the communication system 1 according to the above-described embodiment transmits and receives optical signals between the lower-level device 7 and the slave station 300, this is not limiting. For example, the communication system 1 according to another embodiment may transmit and receive electrical signals between the lower-level device 7 and the slave station 300. For example, the slave station 300 may include an electrical signal forwarding device instead of the optical selector 400. The forwarding device forwards the electrical signal transmitted from the relay device to the lower-level device 7-2 corresponding to the relay device, and forwards the electrical signal transmitted from the lower-level device 7-2 to the corresponding PON-PKG 320. [Explanation of symbols]

[0090] 1. Communication Systems 100 Master station 110 Control Package 120 PON-PKG 130 Transfer PKG 131 Control Unit 140 Switch 200 Optical Selector 201 Optical Switch 202 Control section 250 Main signal line 300 slave stations 310 Control Package 320 PON-PKG 330 Transfer PKG 331 Control Unit 400 Optical Selector 401 Optical Switch 402 Control Unit 500 Monitoring and control device 510 Control signal line 530 Control signal line 7, 7-1, 7-2 Lower level devices 8 Upper device

Claims

1. a first communication device; a second communication device connected to the first communication device via a first communication path; a monitoring and control device connected to the first communication device and the second communication device via a second communication path different from the first communication path; A communication system comprising: The first communication device a switch for transmitting and receiving a main signal related to a lower device to and from a higher device; a first transfer device that relays, via the first communication path, a main signal related to a second lower-level device that is a lower-level device connected to the second communication device between the switch and the second communication device; a first control unit that controls the second communication device; Equipped with The second communication device a redundant second terminating device that terminates a main signal related to the second lower-level device; a second transfer device that relays a main signal related to the second lower-level device between the first communication device and the second terminal device via the first communication path; a switching unit for switching a second terminal device of a standby system among the redundant second terminal devices to a working system; a second control unit that controls the second communication device; Equipped with when the second control unit detects an abnormality in a second terminal device of the active system, it notifies the first communication device of the occurrence of the abnormality via the first communication path, and notifies the monitoring control device of the occurrence of the abnormality via the second communication path; the first control unit, when notified of the occurrence of an abnormality in the second terminal device, transmits setting information required for switching the second terminal device via the first communication path; the monitoring and control device transmits the setting information via the second communication path when notified of the occurrence of an abnormality in the second terminal device; The switching unit switches the second terminal device of the standby system to the working system based on the setting information received from the first communication device or the monitoring control device. Communication system.

2. the first communication path is made redundant, The first communication device switches the first communication path of a standby system to the working system when an abnormality is detected in the first communication path of a working system. The communication system of claim 1 .

3. when receiving a notification of an abnormality in the first communication path of the active system from the first communication device, the monitoring control device transmits a switching instruction for the first communication path to the first communication device; The first communication device switches the first communication path of the standby system to the working system based on the switching instruction. The communication system according to claim 2 .

4. when notified of the occurrence of an abnormality in the second terminal device, the first control unit notifies the monitoring control device of the occurrence of the abnormality in the second terminal device; when receiving a notification of an abnormality in the second terminal device from the first communication device, the monitoring control device transmits the setting information to the first communication device; The first communication device transmits the setting information received from the monitoring control device to the second communication device. The communication system according to any one of claims 1 to 3.

5. The first communication device a redundant first terminating device that terminates a main signal related to a first lower-level device that is a lower-level device connected to the first communication device; The communication system according to any one of claims 1 to 3, comprising:

6. a redundant termination device that terminates a main signal related to a lower-level device; a communication unit that relays a main signal related to the lower-level device between the terminating device and another communication device connected via a first communication path; a control unit that, when detecting an abnormality in a termination device of a working system, notifies the other communication device of the occurrence of the abnormality via the first communication path and notifies a monitoring control device of the occurrence of the abnormality via the second communication path; a switching unit that switches a termination device of a standby system to a working system based on setting information received from the other communication device or the monitoring control device; A communication device comprising:

7. a first communication device including a switch for transmitting and receiving a main signal related to a lower device between the first communication device and the upper device, and a first transfer device for relaying, via the first communication path, a main signal related to a second lower device which is a lower device connected to the second communication device via the first communication path; the second communication device including a transfer device that transfers a main signal related to the second lower-level device and a redundant second termination device that terminates the main signal related to the second lower-level device; a monitoring and control device connected to the first communication device and the second communication device via a second communication path different from the first communication path; An abnormality handling method in a communication system comprising: when the second communication device detects an abnormality in the second terminal device, notifying the first communication device of the occurrence of the abnormality via the first communication path; when the second communication device detects an abnormality in the second terminal device, notifying the occurrence of the abnormality to the monitoring control device via the second communication path; a step of transmitting, by the first communication device, setting information required for switching the second terminal device via the first communication path when the first communication device is notified of the occurrence of an abnormality in the second terminal device; a step in which the monitoring control device transmits the setting information via the second communication path when notified of the occurrence of an abnormality in the second terminal device; The second communication device switches the second terminal device of the standby system to the working system based on the setting information received from the first communication device or the monitoring and control device. How to deal with abnormalities.

8. a redundant termination device that terminates a main signal related to a lower-level device; and a transfer unit that relays the main signal related to the lower-level device between the termination device and another communication device connected via a first communication path; a computer of a communication device comprising: a control unit that, when detecting an abnormality in a termination device of the active system, notifies the other communication device of the occurrence of the abnormality via the first communication path and notifies the monitoring control device of the occurrence of the abnormality via the second communication path; a switching unit that switches a terminating device of a standby system to a working system based on setting information received from the other communication device or the monitoring control device; A program to function as a

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