OPTICAL COMMUNICATION SYSTEM, CONTROL CIRCUIT, STORAGE MEDIUM AND OPTICAL COMMUNICATION METHOD

Abstract

Optical communication system (100) for transmitting data over a plurality of stages, comprising a plurality of redundant systems (50), each designed to have redundancy, using a plurality of optical transmitters (1) and a plurality of optical receivers (2), wherein the optical communication system (100) comprises: Transmission control units (12), each provided for a corresponding plurality of redundant systems (50) to control transmission times of the plurality of optical transmitters (1) contained in the corresponding plurality of redundant systems (50); Signal loss detection units (10), each provided on a corresponding plurality of optical receivers (2) to detect a loss of a received signal of the corresponding plurality of optical receivers (2); a fault management unit (13) to obtain first fault occurrence information from a signal loss detection unit (10) among the signal loss detection units (10) that has detected a fault in a transmission path between each of the plurality of optical transmitters (1) and a corresponding one of the plurality of optical receivers (2), indicating information about the fault in the transmission path, and to collectively manage parts of the first fault occurrence information from the plurality of redundant systems (50), and to determine, using the parts of first fault occurrence information under collective management, in which of the plurality of redundant systems (50) a switching of paths for the transmission of the data must be carried out; and a switching control unit (14) to control the switching of the paths depending on a result of the determination in at least one redundant system (50) from the plurality of redundant systems (50) in which the fault has occurred.

Description

AREA

[0001] The present disclosure relates to an optical communication system for implementing redundancy, a control circuit, a storage medium and an optical communication method. BACKGROUND

[0002] Conventional optical communication systems capable of implementing redundancy include an optical communication system as described in patent reference 1. The optical communication system disclosed in patent reference 1 can implement redundancy as follows: specifically, since each of the optical receivers can receive two transmission signals with different priorities using time-division multiplexing, a signal loss detection unit of the optical receiver connected to the higher-priority path exhibiting the fault sends a warning signal to each of the signal selection units. Each signal selection unit then switches the paths to obtain a signal via a lower-priority path if a fault has occurred in a higher-priority path. The optical communication system disclosed in patent reference 1 can be implemented using a passive component, such as...an optical coupler can be set up without using an active component, such as an optical switch, and can thus advantageously achieve an improvement in reliability, a reduction in energy consumption, a saving in space, a reduction in weight, a reduction in cost and the like. REFERENCE LIST PATENT LITERATURE

[0003] Patent literature 1: WO 2021 / 100083 A1 SUMMARY OF THE TECHNICAL PROBLEM

[0004] However, according to the conventional technology described above, the signal loss detection unit of the optical receiver connected to the higher-priority path containing the fault detects a loss of signal when a fault occurs in the higher-priority path and directly notifies only the signal selection unit in each optical receiver of the alarm signal to provide notification of the fault's occurrence. In a case where the conventional technology described above is applied to an optical communication system using multiple transmission paths designed for redundancy, a redundant system at a subsequent stage has no way of knowing that a fault has occurred in a redundant system at a preceding stage.The problem is that an error that occurred in the redundant system at the preceding stage is mistakenly still recorded as an error in the subsequent redundant system, even though no error has occurred in the subsequent redundant system.

[0005] The present disclosure was prepared in view of these circumstances and one objective of the present disclosure is to provide an optical communication system capable of reducing erroneous error detection in a configuration for transmitting data across multiple stages comprising multiple systems, each designed to have redundancy. SOLUTION TO THE PROBLEM

[0006] To solve the problems described above and achieve the objective, the present invention proposes an optical communication system according to the main claim, as well as a control circuit, a storage medium, and a communication method according to the dependent claims. In particular, the present disclosure describes an optical communication system for transmitting data across a plurality of stages, comprising a plurality of redundant systems, each designed to be redundant, using a plurality of optical transmitters and a plurality of optical receivers. The optical communication system includes: transmission control units, each provided for a corresponding plurality of redundant systems and each controlling transmission times of the plurality of optical transmitters contained in the corresponding plurality of redundant systems;Signal loss detection units, each provided at a corresponding optical receiver of the plurality to detect a loss of a received signal from a corresponding optical receiver of the plurality; a fault management unit that obtains initial fault occurrence information from a signal loss detection unit among the signal loss detection units that has detected a fault in a transmission path between each optical transmitter and a corresponding optical receiver of the plurality, providing information about the fault in the transmission path, and collectively manages information about the faults in the transmission paths in the plurality of redundant systems; and a switching control unit that controls the switching of paths for the transmission of data in a redundant system in which the fault occurred in the plurality of redundant systems. ADVANTAGEOUS EFFECTS OF THE INVENTION

[0007] The optical communication system according to the present disclosure has the effect of being able to reduce erroneous error detection in the configuration for transmitting data through the multitude of stages, including the multitude of systems, each designed for redundancy. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a representation showing an example configuration of an optical communication system according to a first embodiment. Fig. Figure 2 is a representation illustrating an example of the optical communication system according to the embodiment in which the number M of redundant stages is 2 and the number N of input ports is 3. Fig. Figure 3 is a representation showing exemplary configurations of packet signals in each of the redundant systems of the in Fig. The optical communication system shown in Figure 2 is illustrated. Fig. Figure 4 is a first sequence diagram illustrating an operation in which the optical communication system, according to the embodiment, performs a switch from an active system to a standby system when a fault has occurred in the optical communication system. Fig. Figure 5 is a second sequence diagram illustrating an operation in which the optical communication system, according to the embodiment, performs a switch from the active system to the standby system when a fault has occurred in the optical communication system. Fig. Figure 6 is a first representation illustrating a state in which an error has occurred of the optical communication system according to the embodiment in which the number M of redundant stages is 2 and the number N of input terminals is 3. Fig. Figure 7 is a representation showing exemplary configurations of packet signals in each of the redundant systems of the in Fig. The optical communication system shown in section 6 is illustrated. Fig. Figure 8 is a second representation illustrating a state in which an error has occurred of the optical communication system according to the embodiment in which the number M of redundant stages is 2 and the number N of input ports is 3. Fig. Figure 9 is a representation showing exemplary configurations of packet signals in each of the redundant systems of the in Fig. The optical communication system shown in section 8 is illustrated. Fig. Figure 10 is a representation showing an example configuration of a processing circuit in a case where a processor and a working memory implement the processing circuit that implements the optical communication system according to the embodiment. Fig. Figure 11 is a representation showing an example configuration of a processing circuit in a case where dedicated hardware forms the processing circuit that implements the optical communication system according to the embodiment. DESCRIPTION OF THE EXECUTION FORMS

[0008] Below, with reference to the drawings, an optical communication system, a control circuit, a storage medium and an optical communication method according to an embodiment of the present disclosure are described in detail. Design.

[0009] Fig. Figure 1 is a representation showing an example configuration of an optical communication system 100 according to the present embodiment. The optical communication system 100 is an optical communication system with a plurality of stages of transmission paths designed to exhibit redundancy using time division multiplexing (TDM). In particular, the optical communication system 100 is configured to implement redundancy by using TDM with a number of N input ports, a number of N+1 output ports, and a number of M redundant stages.The optical communication system 100 comprises optical transmitters 1-1-1 to 1-M-(N+1), optical receivers 2-1-1 to 2-M-(N+1), first optical couplers 3-1-1 to 3-M-(N+1), each provided on a corresponding transmitter from the plurality of optical transmitters 1-1-1 to 1-M-(N+1), second optical couplers 4-1-1 to 4-M-(N+1), each provided on a corresponding optical receiver from the plurality of optical receivers 2-1-1 to 2-M-(N+1), transmission control units 12-1 to 12-M, a fault management unit 13 and a switching control unit 14. Each of the optical transmitters 1-1-1 to 1-M-(N+1) comprises a corresponding signal generation unit 8-1-1 to 8-M-(N+1). Each of the optical receivers 2-1-1 to 2-M-(N+1) comprises a corresponding receive signal selection unit 9-1-1 to 9-M-(N+1) and a corresponding signal loss detection unit 10-1-1 to 10-M-(N+1).It should be noted that the number M of redundant stages and the number N of input ports are positive integers of two or more.

[0010] In the optical communication system 100, a redundant system 50-1 at the first stage comprises optical transmitters 1-1-1 to 1-1-N and optical receivers 2-1-1 to 2-1-(N+1). A redundant system 50-2 at the second stage comprises optical transmitters 1-2-1 to 1-2-(N+1) and optical receivers 2-2-1 to 2-2-(N+1). A redundant system 50-M at the M-th stage comprises optical transmitters 1-M-1 to 1-M-(N+1) and optical receivers 2-M-1 to 2-M-(N+1).

[0011] In the following description, the optical transmitters 1-1-1 to 1-M-(N+1) can each be referred to as optical transmitter 1 if they are not distinguished from each other, the optical receivers 2-1-1 to 2-M-(N+1) can each be referred to as optical receiver 2 if they are not distinguished from each other, the first optical couplers 3-1-1 to 3-M-(N+1) can each be referred to as a first optical coupler 3 if they are not distinguished from each other, and the second optical couplers 4-1-1 to 4-M-(N+1) can each be referred to as a second optical coupler 4 if they are not distinguished from each other.Additionally, in the following description, the signal generation units 8-1-1 to 8-M-(N+1) can each be referred to as signal generation unit 8 if they are not distinguished from one another; the receive signal selection units 9-1-1 to 9-M-(N+1) can each be referred to as receive signal selection unit 9 if they are not distinguished from one another; the signal loss detection units 10-1-1 to 10-M-(N+1) can each be referred to as a signal loss detection unit 10 if they are not distinguished from one another; and the transmission control units 12-1 to 12-M can each be referred to as a transmission control unit 12 if they are not distinguished from one another. Furthermore, the redundant systems 50-1 to 50-M can each be referred to as a redundant system 50 in the following description if they are not distinguished from one another. In the example of . Fig. The optical transmitter 1 comprises the signal generation unit 8. Furthermore, the optical receiver 2 comprises the received signal selection unit 9 and the signal loss detection unit 10. The optical communication system 100 is an optical communication system for transmitting data across a plurality of stages, comprising the plurality of redundant systems 50, each designed to have redundancy, using the plurality of optical transmitters 1 and a plurality of optical receivers 2.

[0012] In the first stage of the redundant network, optical transformer 1-1-1 is connected to the first optical coupler 3-1-1 via optical fiber 5-1-1. Optical transformer 1-1-2 is connected to the first optical coupler 3-1-2 via optical fiber 5-1-2. Optical transformer 1-1-N is connected to the first optical coupler 3-1-N via optical fiber 5-1-N.

[0013] Furthermore, the first optical coupler 3-1-1 is connected to the second optical coupler 4-1-1 via optical fiber 6-1-1a and to the second optical coupler 4-1-2 via optical fiber 6-1-1b. The first optical coupler 3-1-2 is connected to the second optical coupler 4-1-2 via optical fiber 6-1-2a and to the second optical coupler 4-1-3 via optical fiber 6-1-2b. The first optical coupler 3-1-N is connected to the second optical coupler 4-1-N via optical fiber 6-1-Na and to the second optical coupler 4-1-(N+1) via optical fiber 6-1-Nb.

[0014] Additionally, the second optical coupler 4-1-1 is connected to the optical receiver 2-1-1 via optical fiber 7-1-1. The second optical coupler 4-1-2 is connected to the optical receiver 2-1-2 via optical fiber 7-1-2. The second optical coupler 4-1-(N+1) is connected to the optical receiver 7-1-(N+1) via optical fiber 2-1-(N+1).

[0015] In redundant system 50, optical transformer 1-M-1 in the M-th stage is connected to the first optical coupler 3-M-1 via optical fiber 5-M-1. Optical transformer 1-M-2 is connected to the first optical coupler 3-M-2 via optical fiber 5-M-2. Optical transformer 1-M-(N+1) is connected to the first optical coupler 3-M-(N+1) via optical fiber 5-M-(N+1).

[0016] Furthermore, the first optical coupler 3-M-1 is connected to the second optical coupler 4-M-1 via optical fiber 6-M-1a and to the second optical coupler 4-M-2 via optical fiber 6-M-1b. Additionally, the first optical coupler 3-M-2 is connected to the second optical coupler 4-M-2 via optical fiber 6-M-2a and to the second optical coupler 4-M-3 via optical fiber 6-M-2b. The first optical coupler 3-M-(N+1) is connected to the second optical coupler 4-M-(N+1) via optical fiber 6-M-(N+1)a and to the second optical coupler 4-M-1 via optical fiber 6-M-(N+1)b.

[0017] Additionally, the second optical coupler 4-M-1 is connected to the optical receiver 2-M-1 via optical fiber 7-M-1. The second optical coupler 4-M-2 is connected to the optical receiver 2-M-2 via optical fiber 7-M-2. The second optical coupler 4-M-(N+1) is connected to the optical receiver 2-M-(N+1) via optical fiber 7-M-(N+1).

[0018] Each of the first optical couplers 3 has the function of splitting the optical signal transmitted by a corresponding optical transmitter 1 and outputting the split optical signals to corresponding second optical couplers 4. Each of the second optical couplers 4 has the function of combining a multitude of optical signals output by the first optical couplers 3 and outputting the combined optical signal to a corresponding optical receiver 2. Here, the first optical couplers 3 and the second optical couplers 4 refer to power dividers.

[0019] It should be noted that optical receiver 2-1-1 outputs the selected packet signal in the subsequent stage via transmission path 11-1-1 to optical transmitter 1-2-1. Optical receiver 2-1-2 outputs the selected packet signal in the subsequent stage via transmission path 11-1-2 to optical transmitter 1-2-2. Optical receiver 2-1-(N+1) outputs the selected packet signal in the subsequent stage via transmission path 11-1-(N+1) to optical transmitter 1-2-(N+1). Additionally, optical receiver 2-M-1 outputs the selected packet signal via transmission path 11-M-1. Optical receiver 2-M-2 outputs the selected packet signal via transmission path 11-M-2. Optical receiver 2-M-(N+1) outputs the selected packet signal via transmission path 11-M-(N+1).

[0020] In the following description, optical fibers 5-1-1 to 5-M-(N+1) can each be referred to as optical fiber 5 if they are not distinguished from one another; optical fibers 6-1-1a to 6-M-(N+1)b can each be referred to as optical fiber 6 if they are not distinguished from one another; optical fibers 7-1-1 to 7-M-(N+1) can each be referred to as optical fiber 7 if they are not distinguished from one another; and transmission paths 11-1-1 to 11-M-(N+1) can each be referred to as transmission path 11 if they are not distinguished from one another. That is, optical receiver 2 outputs the selected packet signal via transmission path 11. It should be noted that optical fibers 5, 6, and 7 can also be referred to as transmission paths.

[0021] The optical transmitters 1-1-1 to 1-M-(N+1) each receive a data signal for which a transmission request is made and each receives two types of control signals: a reference clock and a transmission time signal, generated by one of the corresponding transmission control units 12-1 to 12-M. The reference clock is a time or similar reference used for synchronization among the optical transmitters 1-1-1 to 1-M-(N+1). The transmission time signal specifies a time at which each of the optical transmitters 1-1-1 to 1-M-(N+1) is to transmit data. In the optical transmitters 1-1-1 to 1-M-(N+1), the data signals input into the signal generation units 8-1-1 to 8-M-(N+1) are temporarily stored once and output as packet signals according to the transmission time signals. In the following description, the data signals can simply be referred to as data.

[0022] The transmission control units 12-1 to 12-M control the transmission times of the respective optical transmitters 1 such that the optical transmitters 1, each having the path via which the packet signal is input into the same second optical coupler 4, do not transmit the packet signals at the same transmission time. The transmission control units 12-1 to 12-M are each provided for a corresponding plurality of redundant systems 50-1 to 50-M and each control transmission times of the plurality of optical transmitters 1 contained in the corresponding plurality of redundant systems 50. For example, it is assumed that all optical transmitters 1-1-1 to 1-1-N receive transmission requests for packet signals of the same size.With regard to optical transmitters 1-1-1 and 1-1-2, each of which carries the path through which the packet signal is input into the second optical coupler 4-1-2 of the redundant system 50-1 at the first stage, the transmission control unit 12-1 performs a control operation in the first timeslot 1 to cause optical transmitter 1-1-1 to transmit the packet signal and to prevent optical transmitter 1-1-2 from transmitting the packet signal. The transmission control unit 12-1 performs a control operation in the next timeslot 2 to cause optical transmitter 1-1-2 to transmit the packet signal and to prevent optical transmitter 1-1-1 from transmitting the packet signal.

[0023] With regard to optical transmitters 1-1-2 and 1-1-3, each of which has the path via which the packet signal is input into the second optical coupler 4-1-3 of the redundant system 50-1 at the first stage, the transmission control unit 12-1 additionally performs a control operation in the first timeslot 1 to cause optical transmitter 1-1-3 to transmit the packet signal and to prevent optical transmitter 1-1-2 from transmitting the packet signal. The transmission control unit 12-1 performs a control operation in the next timeslot 2 to cause optical transmitter 1-1-2 to transmit the packet signal and to prevent optical transmitter 1-1-3 from transmitting the packet signal.It should be noted that the transmission control units 12-1 to 12-M can control the transmission times of the optical transmitters 1, which transmit packet signals that are not input into the same second optical coupler 4, so that the transmission times coincide or do not coincide.

[0024] In addition to generating the reference clock and the transmission timing signals, the transmission control units 12-1 to 12-M generate portions of timeslot allocation information, specifying which timeslots the data packets output by the respective optical transmitters 1, i.e., the packet signals to be transmitted, have been assigned to, and communicate these portions of timeslot allocation information to the switching control unit 14 and the respective optical receivers 2-1-1 to 2-M-(N+1). For example, the transmission control unit 12-1 communicates to the switching control unit 14 and the optical receivers 2-1-1 to 2-1-(N+1) the timeslot allocation information indicating that data 1 was transmitted from optical transmitter 1-1-1 in timeslot 1 and data 2 was transmitted from optical transmitter 1-1-2 in timeslot 2.

[0025] The packet signal, for which the transmission time has been determined, is converted from an electrical signal into an optical signal and transmitted by each of the optical transmitters 1-1-1 to 1-M-(N+1), divided by the corresponding first optical coupler 3, and fed into the corresponding second optical coupler 4. The second optical coupler 4 combines the multiple optical signals output by the first optical couplers 3 and outputs the composite optical signal to the corresponding optical receiver 2.

[0026] Optical receivers 2-1-1 to 2-M-(N+1) convert all received optical signals into electrical signals. Packet signals received by optical receivers 2-1-1 to 2-M-(N+1) include packet signals transmitted via at least one of the optical fibers 6-X-Ya, 6-X-Ya and 6-X-Yb, or 6-X-Yb. Note that X ranges from 1 to M and Y ranges from 1 to (N+1). For example, in redundant system 50-1, optical receiver 2-1-2 at the first stage can receive packet signals transmitted by optical transmitters 1-1-1 and 1-1-2 via optical fibers 6-1-1b and 6-1-2a. In the present embodiment, the optical communication system 100 assigns priorities to the optical fibers 6-1-1a to 6-M-(N+1)b, ​​which are transmission paths through which packet signals are transmitted from the plurality of optical transmitters 1 to an optical receiver 2.The paths with optical fibers 6 ending with "a" are higher priority paths, and the paths with optical fibers 6 ending with "b" are lower priority paths.

[0027] The following is a description of a company for the in Fig. Figure 1 describes an optical communication system 100 for selecting an output signal from a received signal. As described above, the optical receiver 2 comprises the received signal selection unit 9 and the signal loss detection unit 10.

[0028] The signal loss detection units 10-1-1 to 10-M-(N+1) each detect a loss of the received signal based on the time slot allocation information obtained from a corresponding transmission control unit 12-1 to 12-M, and each output a result of the detected loss of the received signal as fault occurrence information to the fault management unit 13. The signal loss detection units 10-1-1 to 10-M-(N+1) are each provided at a corresponding plurality of optical receivers 2-1-1 to 2-M-(N+1) and each detect a loss of a received signal from a corresponding plurality of optical receivers 2. For example, it is assumed that in the redundant system 50-1, at the first stage, data 1 is transmitted from optical transmitter 1-1-1 in an odd time slot and data 2 is transmitted from optical transmitter 1-1-2 in an even time slot.If a fault occurs in optical fiber 6-1-2a, the signal loss detection unit 10-1-2 of optical receiver 2-1-2 cannot detect the data 2 transmitted by optical transmitter 1-1-2 in the even time slot of the received signal and therefore outputs fault occurrence information to fault management unit 13, indicating that the fault occurred in the higher priority path of optical receiver 2-1-2. It should be noted that, with regard to the fault occurrence information to be output to fault management unit 13, the signal loss detection unit 10 can also output fault occurrence information even when no fault has occurred, without being limited to the case where a fault has occurred.

[0029] Each of the receive signal selection units 9-1-1 to 9-M-(N+1) has a function to select time slots for data acquisition from the received signal of a corresponding optical receiver 2-1-1 to 2-M-(N+1), based on time slot allocation information obtained from a corresponding transmission control unit 12-1 to 12-M. Additionally, each of the receive signal selection units 9-1-1 to 9-M-(N+1) has the function to switch time slots to be selected for data acquisition based on a switching request from the switching control unit 14. The receive signal selection units 9-1-1 to 9-M-(N+1) can be, for example, demuplexers (demux), and the signal selection method is not restricted.The receive signal selection units 9-1-1 to 9-M-(N+1) are each provided on a corresponding plurality of optical receivers 2-1-1 to 2-M-(N+1) and each selects time slots based on the data contained in the receive signal, to which the data output by the corresponding optical receiver 2 to a subsequent stage have been assigned.

[0030] Using the example of the optical communication system 100, where the number M of redundant stages is 2 and the number N of input ports is 3, an example of a functional configuration for selecting an output signal from a received signal is now described, in a case where each device in the optical communication system 100 operates normally. Fig. Figure 2 is a representation illustrating an example of the optical communication system 100 according to the present embodiment, in which the number M of redundant stages is 2 and the number N of input ports is 3. Fig. Figure 3 is a representation showing exemplary configurations of packet signals in each redundant system 50 of the in Fig. 2 shows optical communication system 100. Fig. Figure 3 shows examples of packet signals output by each optical transmitter 1, packet signals input by each optical receiver 2, and packet signals output by each receive signal selection unit 9. It should be noted that in Fig. 3. For a better understanding of the relationship between input and output, the packet signal to be input is referred to as the input signal and the packet signal to be output as the output signal. Furthermore, the redundant system 50-1 is referred to as the redundant first-stage configuration, and the redundant system 50-2 is referred to as the redundant second-stage configuration. The same applies to the following similar drawings.

[0031] As in Fig. As shown in Figure 3, data 1 is input into optical transmitter 1-1-1, data 2 into optical transmitter 1-1-2, and data 3 into optical transmitter 1-1-3. Optical transmitters 1-1-1 to 1-1-3 transmit packet signals within predetermined time slots, based on the transmission time signals obtained by the transmission control unit 12-1. In the example of Fig. Optical transmitter 1-1-1 transmits the packet signals of data 1 in time slots 1 and 3, optical transmitter 1-1-2 transmits the packet signals of data 2 in time slots 2 and 4, and optical transmitter 1-1-3 transmits the packet signals of data 3 in time slots 1 and 3. The packet signals are converted from electrical signals to optical signals in optical transmitters 1-1-1 to 1-1-3, split by the first optical couplers 3, combined by the second optical couplers 4, and fed into the corresponding optical receivers 2-1-1 to 2-1-4.

[0032] Optical receivers 2-1-1 to 2-1-4 convert the received optical signals into electrical signals. Within optical receivers 2-1-1 to 2-1-4, signal loss detection units 10-1-1 to 10-1-4 determine, based on the time slot allocation information obtained from the transmission control unit 12-1, whether the packet signals transmitted by optical transmitters 1-1-1 to 1-1-3, to which optical receivers 2-1-1 to 2-1-4 are connected, have been lost. For example, since optical transmitters 1-1-1 and 1-1-2 are connected to optical receiver 2-1-2, signal loss detection unit 10-1-2 checks whether the packet signals in time slots 1 and 3 and the packet signals in time slots 2 and 4 have been lost. If no loss of packet signals occurs in the corresponding time slots, the signal loss detection unit 10-1-2 determines that no error has occurred.

[0033] In the event of no error, each receive signal selection unit 9, based on the timeslot allocation information, must select only the packet signals in the timeslots that are transmitted via the higher priority path. Thus, receive signal selection unit 9-1-1 of optical receiver 2-1-1 outputs data 1 to optical transmitter 1-2-1, receive signal selection unit 9-1-2 of optical receiver 2-1-2 outputs data 2 to optical transmitter 1-2-2, and receive signal selection unit 9-1-3 of optical receiver 2-1-3 outputs data 3 to optical transmitter 1-2-3. In the optical communication system 100, each device of the redundant system 50-2 at the second stage also performs the same operation as each device of the redundant system 50-1 at the first stage, in order to enable the transfer of data 1 to data 3 without using the standby system.

[0034] Next, an example of a functional configuration of the optical communication system 100 is described in order to switch from the active system to the standby system in the event of an error occurring in the optical communication system 100. Fig. Figure 4 is a first sequence diagram illustrating an operation in which the optical communication system 100 according to the present embodiment performs a switching from the active system to the standby system when a fault has occurred in the optical communication system 100. Fig. Figure 5 is a second sequence diagram illustrating an operation in which the optical communication system 100, according to the present embodiment, switches from the active system to the standby system when a fault occurs in the optical communication system 100. The operation of each device, in which the packet signal, the timing of which has been adjusted in the optical transmitter 1, is converted from an electrical signal to an optical signal by the optical transmitter 1, is fed via the optical fiber 5, the first optical coupler 3, the optical fiber 6, the second optical coupler 4, and the optical fiber 7 into the corresponding optical receiver 2, and is converted from the optical signal to the electrical signal by the optical receiver 2, is similar to the operation of each device in a case in which each device in the optical communication system 100 is operating normally.

[0035] Fault Management Unit 13 manages and updates fault occurrence information relating to each of a multitude of redundant paths, based on fault occurrence information obtained from each of the Signal Loss Detection Units 10-1-1 to 10-M-(N+1). Furthermore, based on this fault occurrence information, Fault Management Unit 13 determines whether or not switching control is required and outputs the fault occurrence information to Switching Control Unit 14 if it determines that switching control is necessary.The fault management unit 13 obtains fault occurrence information from the signal loss detection unit 10, which has detected the loss of the transmission path between the optical transmitter 1 and the optical receiver 2. This information specifies details of the loss of the transmission path and collectively manages the transmission path fault information across the multitude of redundant systems 50. For example, if a fault has occurred in optical fiber 6-1-1a, the signal loss detection unit 10-1-1 of optical receiver 2-1-1 detects a loss of signal and outputs fault occurrence information to the fault management unit 13, indicating that the fault occurred in the higher-priority path at optical receiver 2-1-1.If a fault occurs in a higher-priority path in one of the optical receivers 2, the fault management unit 13 determines that switching control must be performed and outputs the fault occurrence information to the switching control unit 14. It should be noted that even after receiving notification of the fault occurrence information from the signal loss detection unit 10, the fault management unit 13 may still determine not to perform the switching control. For example, if a fault occurs in optical fiber 6-1-1b, the signal loss detection unit 10-1-2 of optical receiver 2-1-2 detects a loss of signal and outputs fault occurrence information to the fault management unit 13, indicating that the fault occurred in the lower-priority path in optical receiver 2-1-2.In such a case, the fault management unit 13 can determine that switching control does not need to be performed and that the fault occurrence information does not need to be output to the switching control unit 14. In the following description, the fault occurrence information output by the signal loss detection unit 10 to the fault management unit 13 can be referred to as first fault occurrence information, and the fault occurrence information output by the fault management unit 13 to the switching control unit 14 can be referred to as second fault occurrence information.

[0036] If a fault has occurred in optical fiber 6-1-2a of redundant system 50-1 in the first stage, it is also possible that during a period from immediately after the occurrence of the fault until the completion of the switching control, not only fault occurrence information indicating that the fault occurred in the higher priority path in optical receiver 2-1-2, but also parts of fault occurrence information indicating that faults occurred in the higher priority paths in optical receivers 2-2-2, ..., and 2-M-2 of redundant systems 50-2, ..., and 50-M in the second and subsequent stages, will be entered into the fault management unit 13.At this point, the fault management unit 13 determines, based on the managed fault occurrence information, that the fault occurred in the redundant system 50 at the front stage and communicates the fault occurrence information corresponding to the redundant system 50 at the front stage to the switching control unit 14. After the switching control unit 14 has executed the switching control, the fault management unit 13 updates the fault occurrence information if no fault has occurred in the optical receivers 2-2-2, ..., and 2-M-2 of the redundant systems 50-2, ..., and 50-M at the second and subsequent stages.

[0037] As described above, if the fault management unit 13 determines, based on the fault occurrence information from the signal loss detection unit 10, that the fault has occurred and path switching must be performed in one of the redundant systems 50, the fault management unit 13 outputs the fault occurrence information to the switching control unit 14, specifying information about the fault relating to the redundant system 50 in which path switching is to be performed, and requests the switching control unit 14 to perform the path switching.When obtaining the multitude of parts of fault occurrence information from the signal loss detection units 10, the fault management unit 13 also first determines, on the basis of the fault occurrence information corresponding to the redundant system 50 in the front stage, whether the switching of the paths in the redundant system 50 in the front stage must be carried out or not.It should be noted that in the case of transmitting certain data in the optical communication system 100, switching the paths includes not only a case in which the optical fiber 5, the first optical coupler 3, the optical fiber 6, a second optical coupler 4 and the optical fiber 7, through which the certain data each pass, are switched between the active system and the standby system, but also a case in which the optical receiver 2, the optical transmitter 1 and the like, through which the certain data each pass, are switched between the active system and the standby system.

[0038] The switching control unit 14 has the function of executing various switching controls based on the portions of time slot allocation information obtained by the transmission control units 12-1 to 12-M and the fault occurrence information obtained by the fault management unit 13. The switching control unit 14 controls the switching of the paths for transmitting data in the redundant system 50 where the fault occurred. The various switching controls described above are described in more detail in sections 1 to 5 below. 1. The switching control unit 14 requests the transmission control unit 12 of the redundant system 50, in which the fault occurred, to stop the output of the optical transmitter 1, which transmits the packet signal to the path in which the fault occurred. 2. The switching control unit 14 determines the time slots to be selected by the receive signal selection units 9-1-1 to 9-M-(N+1) depending on the error occurrence information. 3. The switching control unit 14 reports the occurrence of the error to the receive signal selection units 9-1-1 to 9-M-(N+1) and requests the receive signal selection units 9-1-1 to 9-M-(N+1) to switch the paths for transmitting data, i.e. the time slots to be selected. 4. The switching control unit 14 requests the transmission control units 12-1 to 12-M to switch the transmission controls, i.e., to switch the optical transmitters 1, in each of which the transmission time is to be controlled. 5. The switching control unit 14 requests the transmission control unit 12 of the redundant system 50, in which the fault occurred, to start, i.e. continue, the output of the optical transmitter 1, which stopped transmitting the packet signal to the path in which the fault occurred.

[0039] With regard to the various switching controls to be implemented, the switching control unit 14, as described in Fig. 4 shown, e.g., having a processing counter of 20 and can execute the next switching control after a fixed time period, or, as in Fig. As shown in Figure 5, the switching control unit 14 can be configured such that each device issues a completion message for each of the different switching controls and, upon receiving a completion message from a specific switching control, can execute the next switching control. It should be noted that the processing counter 20 can be located either outside or inside the switching control unit 14. That is, with respect to the operation of each switching control, the switching control unit 14 either executes the operation of the specific switching control and then, after a prescribed period of time has elapsed using a timer such as the processing counter 20, executes the operation of the next switching control, or it checks the completion message each time the operation of the specific switching control is executed and then executes the operation of the next switching control.

[0040] As described above, the switching control unit 14 determines the time slots to be selected by the receive signal selection unit 9 based on the time slot allocation information obtained from the transmission control unit 12, which specifies which time slots the data transmitted by the optical transmitter 1 has been assigned to, and the fault occurrence information obtained from the fault management unit 13, which specifies information about the fault with respect to the redundant system 50 in which the path switching is to take place. The switching control unit 14 requests the receive signal selection unit 9 to switch the selected time slots and requests the transmission control unit 12, corresponding to the redundant system 50 in which the fault occurred, to switch the optical transmitters 1 in which the data transmission timing is to be controlled.In this case, the receive signal selection unit 9 switches the time slots to be selected for data acquisition based on the switching request of the switching control unit 14. The transmission control unit 12 switches the optical transmitters 1 based on the switching request of the switching control unit 14, to which the transmission time signal is output, indicating the time at which the data is to be transmitted.

[0041] Additionally, the switching control unit 14 requests the transmission control unit 12, which corresponds to the redundant system 50 in which the fault occurred, to stop the data transmission of the optical transmitter 1, which transmits data to the transmission path in which the fault occurred, and, after the receive signal selection unit 9 switches the time slots to be selected, requests the transmission control unit 12 to resume the data transmission of the optical transmitter 1, which requested the data transmission to be stopped.In this case, the transmission control unit 12 stops outputting the transmission time signals to the optical transmitters 1, which apply to the data transmission stop request, based on a data transmission resumption request from the switching control unit 14, and resumes outputting the transmission time signals to the optical transmitters 1, which apply to the data transmission resumption request, based on a data transmission resumption request from the switching control unit 14. It should be noted that the switching control unit 14 may omit controls to stop and resume data transmission from the optical transmitter 1 that transmits data on the transmission path where the fault occurred.

[0042] Using the example of the optical communication system 100, where the number M of redundant stages is 2 and the number N of input ports is 3, the operation of each device of the optical communication system 100 at the time of switching from the active system to the standby system is now described when a fault has occurred in the optical fiber 6-1-1a of the redundant system 50-1 in the first stage. Fig. Figure 6 is a first representation illustrating a state in which an error has occurred of the optical communication system 100 according to the present embodiment, in which the number M of redundant stages is 2 and the number N of input ports is 3. Fig. Figure 7 is a representation showing exemplary configurations of packet signals in each redundant system 50 of the in Fig. The optical communication system 100 is shown in the illustration 6. Fig. Figure 7 shows examples of packet signals output by each optical transmitter 1, packet signals input by each optical receiver 2, and packet signals output by each receive signal selection unit 9.

[0043] As in Fig. As shown in Figure 7, data 1 is input into optical transmitter 1-1-1, data 2 into optical transmitter 1-1-2, and data 3 into optical transmitter 1-1-3. Optical transmitters 1-1-1 to 1-1-3 transmit the packet signals within predetermined time slots, based on the transmission time signals obtained by the transmission control unit 12-1. In the example of Fig. 7. Optical transmitter 1-1-1 transmits the packet signals of data 1 in time slots 1 and 3, optical transmitter 1-1-2 transmits the packet signals of data 2 in time slots 2 and 4, and optical transmitter 1-1-3 transmits the packet signals of data 3 in time slots 1 and 3. The packet signals are converted from electrical signals to optical signals in optical transmitters 1-1-1 to 1-1-3, split by the first optical couplers 3, combined by the second optical couplers 4, and fed into the corresponding optical receivers 2-1-1 to 2-1-4.

[0044] Optical receivers 2-1-1 to 2-1-4 convert the received optical signals into electrical signals. Within optical receivers 2-1-1 to 2-1-4, signal loss detection units 10-1-1 to 10-1-4 determine, based on the time slot allocation information obtained from the transmission control unit 12-1, whether the packet signals transmitted by optical transmitters 1-1-1 to 1-1-3, to which optical receivers 2-1-1 to 2-1-4 are connected, have been lost. For example, since optical transmitter 1-1-1 is connected to optical receiver 2-1-1, signal loss detection unit 10-1-1 checks whether the packet signals in time slots 1 and 3 have been lost.Since, for example, optical transmitters 1-1-1 and 1-1-2 are connected to optical receiver 2-1-2, the signal loss detection unit 10-1-2 additionally checks whether the packet signals in timeslots 1 and 3 and the packet signals in timeslots 2 and 4 have been lost. If a fault has occurred in optical fiber 6-1-1a of the redundant system 50-1 in the first stage, the signal loss detection unit 10-1-1 of optical receiver 2-1-1 and the signal loss detection unit 10-2-1 of optical receiver 2-2-1 cannot detect the packet signals in timeslots 1 and 3. Thus, the signal loss detection unit 10-1-1 outputs the fault occurrence information to the fault management unit 13, indicating that the fault occurred in the higher priority path in the optical receiver 2-1-1.Furthermore, the signal loss detection unit 10-2-1 outputs the fault occurrence information to the fault management unit 13, indicating that the fault occurred in the higher priority path in the optical receiver 2-2-1.

[0045] Fault management unit 13 determines, among the parts of fault occurrence information to be managed, whether or not switching control must be performed at the frontier level with respect to the fault occurrence information. In the examples of Fig. 6 and Fig. Fault management unit 13 determines whether or not switching control must be performed with respect to the fault in the higher priority path of optical receiver 2-1-1. Fault management unit 13 determines that switching control must be performed because the fault occurred in the higher priority path and communicates the fault occurrence information to switching control unit 14.

[0046] The switching control unit 14 performs various switching operations based on the time slot allocation information obtained from each of the transmission control units 12-1 and 12-2, and the fault occurrence information obtained from the fault management unit 13. The switching control unit 14 first requests the optical transmitter 1-1-1, which is transmitting a packet signal to the optical fiber 6-1-1a where the fault occurred, to stop transmitting the packet signal. Specifically, the switching control unit 14 requests the transmission control unit 12-1 to stop the transmission timing control for the optical transmitter 1-1-1. The data 1 entered into the optical transmitter 1-1-1 during the transmission stop period is temporarily stored in the optical transmitter 1-1-1 until the switching control operation in the optical communication system 100 is completed.For the data 1 transmitted by optical transmitter 1-1-1, a delay time is introduced in the optical communication system 100, which corresponds to the time span from the start to the end of the operation of the switching control. However, the data fragments 1 accumulated in optical transmitter 1-1-1 can be transmitted collectively after the switching control has finished. Thus, the optical communication system 100 can control the path switching control in the redundant system 50 without causing any data loss.

[0047] Next, the switching control unit 14 determines the time slots to be selected by each receive signal selection unit 9 based on the time slot allocation information and the error occurrence information, and requests each receive signal selection unit 9 to switch the selected time slots. Additionally, the switching control unit 14 requests the transmission control unit 12 to switch the optical transmitters 1 at which the transmission time control is to be performed.

[0048] For example, the switching control unit 14 performs a switching control to cause the optical receiver 2 of the redundant system 50-1 in the first stage to select time slots assigned to optical transmitter 1, which outputs the packet signal to the lower-priority path. In this case, optical receiver 2-1-1 does not select a time slot. Furthermore, optical receiver 2-1-2 selects time slots 1 and 3 in which the packet signals from optical transmitter 1-1-1 are transmitted. Furthermore, optical receiver 2-1-3 selects time slots 2 and 4 in which the packet signals from optical transmitter 1-1-2 are transmitted. Furthermore, optical receiver 2-1-4 selects time slots 1 and 3 in which the packet signals from optical transmitter 1-1-3 are transmitted.The switching control unit 14 requests the transmission control unit 12-2 to perform transmission timing controls for the optical transmitters 1-2-2 to 1-2-4, which output the packet signals in the selected time slots as transmission signals.

[0049] In the redundant system 50-2 in the second stage, the optical receiver 2-2-1 selects the packet signals transmitted by the optical transmitter 1-2-4 in time slots 2 and 4, the optical receiver 2-2-2 selects the packet signals transmitted by the optical transmitter 1-2-2 in time slots 2 and 4, and the optical receiver 2-2-3 selects the packet signals transmitted by the optical transmitter 1-2-3 in time slots 1 and 3.

[0050] After the switching control is complete, the signal loss detection unit 10-2-1 of the optical receiver 2-2-1 can detect the packet signals in timeslots 2 and 4 and thus, with respect to the fault management unit 13, either stop outputting fault occurrence information or output fault occurrence information indicating that no fault occurred in the optical receiver 2-2-1. If the fault management unit 13 no longer obtains fault occurrence information or obtains fault occurrence information indicating that no loss occurred in the optical receiver 2-2-1 from the signal loss detection unit 10-2-1, the fault management unit 13 updates the managed portions of the fault occurrence information to reflect that the fault occurred only in the higher-priority path of the optical receiver 2-1-1.Consequently, in the first stage where the fault occurred, the optical communication system 100 can use the paths of the standby system in the redundant system 50-1, and in the second stage where no fault occurred, it can implement redundancy without using the paths of the standby system in the redundant system 50-2.

[0051] Using the example of the optical communication system 100, where the number M of redundant stages is 2 and the number N of input ports is 3, the operation of each device of the optical communication system 100 at the time of switching from the active system to the standby system is described next in a similar manner when a fault has occurred in the optical fiber 7-1-2 of the redundant system 50-1 in the first stage. Fig. Figure 8 is a second representation illustrating a state in which an error has occurred of the optical communication system 100 according to the present embodiment, in which the number M of redundant stages is 2 and the number N of input ports is 3. Fig. Figure 9 is a representation showing exemplary configurations of packet signals in each redundant system 50 of the in Fig. The optical communication system 100 is shown in the illustration 8. Fig. Figure 9 shows examples of packet signals output by each optical transmitter 1, packet signals input by each optical receiver 2, and packet signals output by each receive signal selection unit 9.

[0052] As in Fig. As shown in Figure 9, data 1 is input into optical transmitter 1-1-1, data 2 into optical transmitter 1-1-2, and data 3 into optical transmitter 1-1-3. Optical transmitters 1-1-1 to 1-1-3 transmit the packet signals within predetermined time slots, based on the transmission time signals obtained by the transmission control unit 12-1. In the example of Fig. 9. Optical transmitter 1-1-1 transmits the packet signals of data 1 in time slots 1 and 3, optical transmitter 1-1-2 transmits the packet signals of data 2 in time slots 2 and 4, and optical transmitter 1-1-3 transmits the packet signals of data 3 in time slots 1 and 3. The packet signals are converted from electrical signals to optical signals in optical transmitters 1-1-1 to 1-1-3, split by the first optical couplers 3, combined by the second optical couplers 4, and fed into the corresponding optical receivers 2-1-1 to 2-1-4.

[0053] Optical receivers 2-1-1 to 2-1-4 convert the received optical signals into electrical signals. If a fault occurs in optical fiber 7-1-2 of the redundant system 50-1 at the first stage, the signal loss detection unit 10-1-2 of optical receiver 2-1-2 and the signal loss detection unit 10-2-2 of optical receiver 2-2-2 cannot detect the packet signals in timeslots 1 and 3, and the packet signals in timeslots 2 and 4. Therefore, signal loss detection unit 10-1-2 outputs fault occurrence information to fault management unit 13, indicating that the fault occurred in the higher-priority path and the lower-priority path at optical receiver 2-1-2.Additionally, the signal loss detection unit 10-2-2 outputs the fault occurrence information to the fault management unit 13, indicating that the fault occurred in the higher priority path and the lower priority path in the optical receiver 2-2-2.

[0054] Fault management unit 13 determines, among the parts of fault occurrence information to be managed, whether or not switching control must be performed at the frontier level with respect to the fault occurrence information. In the examples of Fig. 8 and Fig. Fault management unit 13 determines whether switching control must be performed with respect to the fault in the higher-priority path and the lower-priority path of optical receiver 2-1-2. Fault management unit 13 determines that switching control must be performed because the fault occurred in the higher-priority path and communicates the fault occurrence information to switching control unit 14.

[0055] The switching control unit 14 performs various switching operations based on the time slot allocation information obtained from each of the transmission control units 12-1 and 12-2, and the fault occurrence information obtained from the fault management unit 13. The switching control unit 14 first requests the transmission control unit 12-1 to stop the transmission timing control for the optical transmitter 1-1-2. Next, the switching control unit 14 determines the time slots to be selected by each receive signal selection unit 9 based on the time slot allocation information and the fault occurrence information, and requests each receive signal selection unit 9 to switch the selected time slots. Additionally, the switching control unit 14 requests the transmission control unit 12 to switch the optical transmitters 1 for which transmission timing control is to be performed.

[0056] For example, the switching control unit 14 performs the switching control to cause the optical receiver 2 of the redundant system in the first stage to select time slots, as described above. As a result, the optical receiver 2-1-1 selects the packet signals transmitted by the optical transmitter 1-1-1 in time slots 1 and 3. The optical receiver 2-1-2 also does not select a time slot. Furthermore, the optical receiver 2-1-3 selects the packet signals transmitted by the optical transmitter 1-1-2 in time slots 2 and 4. Additionally, the optical receiver 2-1-4 selects the packet signals transmitted by the optical transmitter 1-1-3 in time slots 1 and 3. The switching control unit 14 requests the transmission control unit 12-2 to perform transmission timing controls for the optical transmitters 1-2-2 to 1-2-4, which output the packet signals in the selected time slots as transmission signals.

[0057] In the redundant system 50-2 in the second stage, the optical receiver 2-2-1 selects the packet signals transmitted by the optical transmitter 1-2-4 in time slots 2 and 4, the optical receiver 2-2-2 selects the packet signals transmitted by the optical transmitter 1-2-1 in time slots 1 and 3, and the optical receiver 2-2-3 selects the packet signals transmitted by the optical transmitter 1-2-3 in time slots 1 and 3.

[0058] After the switching control is complete, the signal loss detection unit 10-2-2 of the optical receiver 2-2-2 can detect the packet signals in timeslots 1 and 3 and the packet signals in timeslots 2 and 4, and thus, with respect to the fault management unit 13, either stop the output of fault occurrence information or output fault occurrence information indicating that no fault occurred in the optical receiver 2-2-2. If the fault management unit 13 no longer obtains fault occurrence information, or if it obtains fault occurrence information indicating that no loss occurred in the optical receiver 2-2-2 from the signal loss detection unit 10-2-2, the fault management unit 13 updates the portions of the fault occurrence information under management to indicate that the fault occurred only in the higher-priority path and the lower-priority path of the optical receiver 2-2-2.Consequently, in the first stage where the fault occurred, the optical communication system 100 can use the paths of the standby system in the redundant system 50-1, and in the second stage where no fault occurred, it can implement redundancy without using the paths of the standby system in the redundant system 50-2.

[0059] It should be noted that in the present embodiment, the optical transmitter 1 includes the signal generation unit 8. However, the signal generation unit 8 can also be provided outside the optical transmitter 1, since the plurality of signal generation units 8 are each provided with the corresponding plurality of optical transmitters 1.

[0060] Furthermore, in the present embodiment, the optical receiver 2 comprises the receive signal selection unit 9 and the signal loss detection unit 10. However, the receive signal selection unit 9 and the signal loss detection unit 10 can be provided outside the optical receiver 2, since each of the plurality of receive signal selection units 9 and each of the plurality of signal loss detection units 10 is provided for the corresponding plurality of optical receivers 2.

[0061] Next, a hardware configuration of the optical communication system 100 is described. In the optical communication system 100, the signal generation unit 8, the receive signal selection unit 9, the signal loss detection unit 10, the transmission control unit 12, the fault management unit 13, and the switching control unit 14 are implemented by processing circuits. The processing circuit may include a working memory that stores a program and a processor that executes the program stored in the working memory, or dedicated hardware. The processing circuit is also referred to as a control circuit.

[0062] Fig. Figure 10 is a representation showing an example configuration of a processing circuit 90 in a case where a processor 91 and a working memory 92 implement the processing circuit, which implements the optical communication system 100 according to the embodiment. The in Fig. The processing circuit 90 shown in Figure 10 is a control circuit and comprises the processor 91 and the main memory 92. Since the processing circuit 90 comprises the processor 91 and the main memory 92, each function of the processing circuit 90 is implemented by software, firmware, or a combination of software and firmware. The software or firmware is described as a program and stored in the main memory 92. In the processing circuit 90, the processor 91 reads the program stored in the main memory 92 and executes it to perform each function. That is, the processing circuit 90 includes the main memory 92 for storing a program that, as a result, performs processing of the optical communication system 100.It can also be stated that this program is a program that causes the optical communication system 100 to execute any function implemented by the processing circuit. This program may be provided by a storage medium in which the program is stored, or it may be provided by other means such as a communication medium.

[0063] It can also be determined that the program is a program that causes the optical communication system 100 to execute: a transmission control step of controlling, by each of the transmission control units 12, each of which is provided for a corresponding plurality of redundant systems 50, transmission times of the plurality of optical transmitters 1 contained in the corresponding redundant system 50; a signal loss detection step of detecting, by each of the signal loss detection units 10, each of which is provided at the corresponding plurality of optical receivers 2, a loss of a received signal of the corresponding optical receiver 2;a fault management step of obtaining, by the fault management unit 13, from the signal loss detection unit 10, which has detected the loss of the transmission path between the optical transmitter 1 and the optical receiver 2, the first fault occurrence information, which indicates the information about the loss of the transmission path, and collectively managing the parts of the information about the faults of the transmission paths in the plurality of redundant systems 50; and a switching control step of controlling, by the switching control unit 14, the switching of the paths for the transmission of data in the redundant system 50 in which the fault occurred.

[0064] Here, for example, the processor 91 is a central processing unit (CPU), a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a digital signal processor (DSP), or the like. Furthermore, the main memory 92 corresponds, for example, to non-volatile or volatile semiconductor memory such as random access memory (RAM), read-only memory (ROM), flash memory, erasable programmable ROM (EPROM), or electrically EPROM (EEPROM, registered trademark), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini-disc, a digital versatile disc (DVD), or the like.

[0065] Fig. Figure 11 is a representation showing an example configuration of a processing circuit 93 in a case where dedicated hardware forms the processing circuit that implements the optical communication system 100 according to the present embodiment. The Fig. The processing circuit shown in Figure 11 corresponds, for example, to a single circuit, a combined circuit, a programmed processor, a parallel programmed processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. Some of the functions of the processing circuit can be implemented by dedicated hardware, and some can be implemented by software or firmware. In this way, the processing circuit can implement any of the functions described above by dedicated hardware, software, firmware, or a combination thereof.

[0066] As described above, the optical communication system 100, according to the present embodiment, in the redundant N+1 configuration, shares and manages the fault occurrence situation among the multiple redundantly designed transmission paths with the redundant systems 50 using the TDM scheme and performs the switching control collectively. Consequently, the optical communication system 100 can implement redundancy and simultaneously reduce erroneous fault detection, even in the configuration using the multiple redundant systems 50 connected in several stages.If errors are detected at a large number of locations due to a fault, the optical communication system 100 can simultaneously correct the fault temporarily detected in the subsequent stage by performing the control described above for switching the paths from the previous stage, and a situation in which the fault continues to be detected erroneously can be prevented.

[0067] The configurations described in the above embodiment are only illustrative and can be combined with other known techniques; the embodiments can be combined with each other, and a part of each of the configurations can be omitted or modified without deviating from the core. REFERENCE SIGNATURE LIST

[0068] 1-1-1 to 1-M-(N+1) optical transmitter; 2-1-1 to 2-M-(N+1) optical receiver; 3-1-1 to 3-M-(N+1) first optical coupler; 4-1-1 to 4-M-(N+1) second optical coupler; 5-1-1 to 5-M-(N+1), 6-1-1a to 6-M-(N+1)b, ​​7-1-1 to 7-M-(N+1) optical fiber; 8-1-1 to 8-M-(N+1) signal generation unit; 9, 9-1-1 to 9-M-(N+1) receive signal selection unit; 10, 10-1-1 to 10-M-(N+1) signal loss detection unit; 11-1-1 to 11-M-(N+1) transmission path; 12,12-1 to 12-M transmission control unit; 13 fault management unit; 14 switching control unit; 20 processing counter; 50-1 to 50-M redundant system; 100 optical communication system.

Claims

[1] Optical communication system (100) for transmitting data over a plurality of stages, comprising a plurality of redundant systems (50), each designed to have redundancy, using a plurality of optical transmitters (1) and a plurality of optical receivers (2), wherein the optical communication system (100) comprises: Transmission control units (12), each provided for a corresponding plurality of redundant systems (50) to control transmission times of the plurality of optical transmitters (1) contained in the corresponding plurality of redundant systems (50); Signal loss detection units (10), each provided on a corresponding plurality of optical receivers (2) to detect a loss of a received signal of the corresponding plurality of optical receivers (2); a fault management unit (13) to obtain first fault occurrence information from a signal loss detection unit (10) among the signal loss detection units (10) that has detected a fault in a transmission path between each of the plurality of optical transmitters (1) and a corresponding one of the plurality of optical receivers (2), indicating information about the fault in the transmission path, and to collectively manage parts of the first fault occurrence information from the plurality of redundant systems (50), and to determine, using the parts of first fault occurrence information under collective management, in which of the plurality of redundant systems (50) a switching of paths for the transmission of the data must be carried out; and a switching control unit (14) to control the switching of the paths depending on a result of the determination in at least one redundant system (50) from the plurality of redundant systems (50) in which the fault has occurred. [2] Optical communication system (100) according to claim 1, wherein, based on the first fault occurrence information, the fault management unit (13) determines that the fault has occurred and the switching of paths must be carried out in a redundant system among the plurality of redundant systems (50), the fault management unit (13) outputs second fault occurrence information to the switching control unit (14), which specifies information about the fault relating to the redundant system (50) in which the switching of paths is to be carried out, and requests the switching control unit (14) to carry out the switching of paths. [3] Optical communication system (100) according to claim 2, wherein, upon obtaining a plurality of parts of the first fault occurrence information, the fault management unit (13) determines, on the basis of the first fault occurrence information corresponding to the redundant system (50) in a front stage, whether the switching of the paths in the redundant system (50) in the front stage must be carried out. [4] Optical communication system (100) according to claim 1, comprising Receive signal selection units (9), each provided to a corresponding plurality of optical receivers (2) to select a time slot to which data has been assigned, based on data contained in the received signal, wherein the data is output by a corresponding plurality of optical receivers (2) to a subsequent stage, wherein The switching control unit (14), based on time slot allocation information and second fault occurrence information, determines the time slots to be selected by the receive signal selection units (9), requests the receive signal selection units (9) to switch the selected time slots, and requests the transmission control unit (12), corresponding to the redundant system (50) in which the fault occurred, to switch the optical transmitters (1) among the plurality of optical transmitters (1), each controlling a transmission time of data, wherein the time slot allocation information is obtained from each of the transmission control units (12) and indicates which time slots have been assigned data segments transmitted by the respective plurality of optical transmitters (1).the second fault occurrence information is obtained from the fault management unit (13) and provides information about the fault relating to the redundant system (50) in which the switching of the paths is to be carried out. [5] Optical communication system (100) according to claim 4, wherein the switching control unit (14) requests the transmission control unit (12), corresponding to the redundant system (50) in which the fault occurred, to stop the data transmission of the optical transmitter (1) which transmits data to the transmission path in which the fault occurred, and after the receive signal selection units (9) switch the time slots to be selected, requests the transmission control unit (12) to resume the data transmission of the optical transmitter (1) which requested the stopping of the data transmission. [6] Optical communication system (100) according to claim 4 or 5, wherein with respect to an operation of each of the switching controls, the switching control unit (14) performs an operation of a specific switching control and performs an operation of a next switching control after the expiry of a prescribed period of time using a timer, or each time an operation of a specific switching control is performed, checks a completion message and performs an operation of a next switching control. [7] Optical communication system (100) according to one of claims 4 to 6, wherein the receiving signal selection units (9) each switch a time slot to be selected for the procurement of data, based on a switching request from the switching control unit (14). [8] Optical communication system (100) according to claim 1, wherein the transmission control units (12) generate parts of time slot allocation information indicating which time slots data pieces output by the plurality of optical transmitters (1) have been allocated, notify the switching control unit (14) and the plurality of optical receivers (2) about the parts of time slot allocation information and, on the basis of a switching request from the switching control unit (14), switch the plurality of optical transmitters (1) to which a transmission time signal is output, indicating a time at which the data are to be transmitted. [9] Optical communication system (100) according to claim 8, wherein the transmission control units (12) stop the output of the transmission time signals to the optical transmitters (1) based on a data transmission stop request from the switching control unit (14), which apply to the data transmission stop request, and resume the output of the transmission time signals to the optical transmitters (1) based on a data transmission resumption request from the switching control unit (14), which apply to the data transmission resumption request. [10] Optical communication system (100) according to claim 1, wherein the signal loss detection units (10) each detect the loss of the received signal based on time slot allocation information obtained from a corresponding transmission control unit (12) and indicating which time slots have been allocated to data pieces transmitted by corresponding members of the plurality of optical transmitters (1), and each output a result of the loss of the received signal as the first error occurrence information to the error management unit (13). [11] Control circuit for controlling an optical communication system (100) for transmitting data over a plurality of stages, comprising a plurality of redundant systems (50), each designed to be redundant, using a plurality of optical transmitters (1) and a plurality of optical receivers (2), wherein the control circuit causes the optical communication system (100) to perform: Control of transmission times of the multitude of optical transmitters (1) contained in the multitude of redundant systems (50); Detection of a loss of a received signal of the corresponding plurality of optical receivers (2); Procurement of first fault occurrence information, which specifies information about a fault in a transmission path between each of the plurality of optical transmitters (1) and a corresponding of the plurality of optical receivers (2), and collective management of portions of the first fault occurrence information from the plurality of redundant systems (50); Determine, using the portions of first error occurrence information under collective management, in which of the multitude of redundant systems (50) a switching of paths for the transmission of the data must be carried out; and Control of switching the paths depending on a result of the determination in at least one redundant system (50) from the multitude of redundant systems (50) in which the fault has occurred. [12] Storage medium which stores a program for controlling an optical communication system (100) for transmitting data over a plurality of stages, comprising a plurality of redundant systems (50), each designed to be redundant, using a plurality of optical transmitters (1) and a plurality of optical receivers (2), wherein the program causes the optical communication system to perform: Control of transmission times of the multitude of optical transmitters (1) contained in the multitude of redundant systems (50); Detection of a loss of a received signal of the corresponding plurality of optical receivers (2); Procurement of first fault occurrence information, which specifies information about a fault in a transmission path between each of the plurality of optical transmitters (1) and a corresponding of the plurality of optical receivers (2), and collective management of portions of the first fault occurrence information from the plurality of redundant systems (50); Determine, using the portions of first error occurrence information under collective management, in which of the multitude of redundant systems (50) a switching of paths for the transmission of the data must be carried out; and Control of switching the paths depending on a result of the determination in at least one redundant system (50) from the multitude of redundant systems (50) in which the fault has occurred. [13] Optical communication method, for use in an optical communication system (100) for transmitting data over a plurality of stages, comprising a plurality of redundant systems (50), each designed to have redundancy, using a plurality of optical transmitters (1) and a plurality of optical receivers (2), wherein the optical communication system comprises: a transmission control step of the control of transmission times of the plurality of optical transmitters (1) contained in the corresponding plurality of redundant systems (50) by each of the transmission control units (12), each of which is provided for a corresponding plurality of redundant systems (50); a signal loss detection step of the detection of a loss of a received signal of the corresponding plurality of optical receivers (2) by each of the signal loss detection units (10), each of which is provided at a corresponding plurality of optical receivers (2); a fault management step of, by means of a fault management unit (13), procuring from a signal loss detection unit (10) among the signal loss detection units (10) that has detected a fault of a transmission path between each of the plurality of optical transmitters (1) and a corresponding of the plurality of optical receivers (2), first fault occurrence information that indicates information about the fault of the transmission path, and collectively managing parts of the first fault occurrence information from the plurality of redundant systems (50); a step of determining, using the parts of first error occurrence information under collective management, in which of the multitude of redundant systems (50) a switching of paths for the transmission of the data must be carried out and a switching control step of controlling the switching of the paths depending on a result of the determination at least in one redundant system (50) from the plurality of redundant systems (50) in which the fault has occurred.

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