Optical communication system, optical communication device, control method for optical communication system, and control method for optical communication device

Abstract

To provide a technique for enabling downsizing and stable operation of an optical communication system.SOLUTION: An optical communication system includes a first communication apparatus and a second communication apparatus each configured to perform optical communication on a trunk optical fiber and a branch optical fiber. The first and second communication apparatuses are optically connected to the branch optical fiber by a branching unit arranged in the branch optical fiber. One of the first and second communication apparatus is an active system and the other is a standby system. The active system performs optical communication on the branch optical fiber. Physical links on the branch optical fibers of the active system and the standby system are logically integrated to form Multi-chassis Link Aggregation. In redundancy switching between the active system and the standby system, the active system transfers operation information for taking over the operation of the active system, to the standby system.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to an optical communication system, an optical communication device, a control method for an optical communication system, and a control method for an optical communication device. [Background technology]

[0002] For example, Japanese Patent Application Laid-Open No. 2015-35760 (Patent Document 1) discloses a PON (Passive Optical Network) system as an example of an optical communication system. The PON system includes a redundant optical line terminal (OLT). The OLT includes multiple optical line units (OSUs) and a switching unit. One of the multiple OSUs is a standby system. The standby OSU can be switched to each of multiple active OSUs for redundancy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-35760 Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration disclosed in JP 2015-35760 A, multiple OSUs are housed in a large enclosure. Therefore, PON protection (redundancy switching) is performed within the same enclosure. Since large devices can accommodate a larger number of users, they are suitable for deployment in areas where optical communication systems are being introduced (e.g., urban areas).

[0005] On the other hand, for example, in rural areas, where the number of users is small, introducing large equipment may be unnecessarily costly. Therefore, it is considered desirable to introduce a small-scale system in areas with a relatively small number of users. One way to reduce the system scale is to simplify the system configuration. However, simplifying the system configuration may reduce tolerance to failures.

[0006] An object of the present disclosure is to provide a technology that enables both miniaturization and stable operation of an optical communication system. [Means for solving the problem]

[0007] An optical communication system according to one embodiment of the present disclosure comprises a first communication device and a second communication device, each configured to enable optical communication over a trunk optical fiber and a branch optical fiber, the first communication device and the second communication device being optically connected to the branch optical fiber by a branching device provided on the branch optical fiber, one of the first communication device and the second communication device being a working system and the other being a standby system, the working system being responsible for optical communication on the branch optical fiber side, the physical links on the trunk optical fiber side of each of the working system and the standby system being logically bundled to form a multi-chassis link aggregation, and in redundant switching between the working system and the standby system, the working system transfers operational information to the standby system for taking over the operation of the working system.

[0008] An optical communication device according to one embodiment of the present disclosure comprises a first communication unit for communicating via a branch optical fiber, a second communication unit for communicating via a trunk optical fiber, and a control unit, wherein when the optical communication device is operated as a current system, the control unit operates the first communication unit and also operates the second communication unit so that physical links on the trunk optical fiber side are logically bundled to form link aggregation, and when the optical communication device is switched from a current system to a standby system, the control unit outputs operational information regarding the operation of the current system from a port for communicating with other optical communication devices.

[0009] A control method for an optical communication system according to one embodiment of the present disclosure is a control method for an optical communication system having a first communication device and a second communication device, each configured to enable optical communication over a trunk optical fiber and a branch optical fiber, wherein the first communication device and the second communication device are optically connected to the branch optical fiber by a branching device provided on the branch optical fiber, one of the first communication device and the second communication device is a working system and the other is a standby system, the working system is responsible for optical communication on the branch optical fiber side, and the physical links on the trunk optical fiber side of each of the working system and the standby system are logically bundled to form a multi-chassis link aggregation, and the control method includes a step of the working system determining that a redundant switchover to the standby system will be performed, a step of transferring operational information for taking over operation of the working system from the working system to the standby system, and a step of transferring control authority from the working system to the standby system.

[0010] A control method for an optical communication device according to one aspect of the present disclosure is a control method for an optical communication device that performs optical communication via a branch optical fiber and a trunk optical fiber, and includes the steps of: when operating the optical communication device as a working system, performing optical communication on the branch optical fiber side and logically bundling physical links on the trunk optical fiber side to form link aggregation; and when switching the optical communication device from the working system to a standby system, outputting operational information regarding the operation of the working system from a port for communicating with other optical communication devices. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to achieve both miniaturization and stable operation of an optical communication system. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram schematically illustrating an application example of an optical communication system according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a diagram schematically illustrating the appearance of an optical communication unit that constitutes an optical communication system according to an embodiment of the present disclosure. [Figure 3]FIG. 3 is a diagram showing an example of the external appearance of the optical communication unit shown in FIG. 2 as seen from the front. [Figure 4] FIG. 4 illustrates a first example of a redundant configuration on the uplink side using optical communication units according to an embodiment of the present disclosure. [Figure 5] FIG. 5 illustrates a second example of a redundant configuration on the uplink side using optical communication units according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a block diagram showing the internal configuration of the optical communication unit shown in FIG. [Figure 7] FIG. 7 is a diagram showing a schematic configuration of an OLT for realizing PON protection. [Figure 8] FIG. 8 is a diagram showing state transitions of the primary and secondary optical communication units shown in FIG. [Figure 9] FIG. 9 is a diagram showing the flow of downstream data during normal operation. [Figure 10] FIG. 10 is a diagram showing the flow of downstream data when the uplink of the primary optical communication unit fails. [Figure 11] FIG. 11 is a diagram illustrating a flow of downstream data when a failure occurs on the uplink side according to an embodiment of the present disclosure. [Figure 12] FIG. 12 is a functional block diagram illustrating functions of an optical communication unit for realizing redundancy switching according to an embodiment of the present disclosure. [Figure 13] FIG. 13 is a sequence diagram illustrating the flow of redundancy switching when a failure occurs in the primary (working) PON side link. [Figure 14] FIG. 14 is a sequence diagram showing the flow of redundancy switching when a failure occurs in the uplink of the active system. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0014] (1) An optical communication system according to one embodiment of the present disclosure includes a first communication device and a second communication device, each configured to enable optical communication over a trunk optical fiber and a branch optical fiber, the first communication device and the second communication device being optically connected to the branch optical fiber by a branching device provided on the branch optical fiber, one of the first communication device and the second communication device being a working system and the other being a standby system, the working system being responsible for optical communication on the branch optical fiber side, the physical links on the trunk optical fiber side of each of the working system and the standby system being logically bundled to form a multi-chassis link aggregation, and in redundant switching between the working system and the standby system, the working system transfers operational information to the standby system for taking over the operation of the working system.

[0015] According to this configuration, the optical communication system is composed of at least two communication devices. One of the two communication devices is assigned to a working system, and the other of the two communication devices is assigned to a standby system. This allows a redundant system to be configured. In the event of a failure in the working system, operational information for taking over the operation of the working system is transferred from the working system to the standby system by redundant switching. This allows the standby system to handle communications for both the trunk optical fiber and the branch optical fiber. This enables the optical communication system to be miniaturized and operate stably.

[0016] In this specification, the terms "active system" and "standby system" are used to distinguish two communication devices from the perspective of optical communication on the branch optical fiber side. The two communication devices are optically connected to the branch optical fiber by a branching device installed on the branch optical fiber, so that only one of the two communication devices communicates through the branch optical fiber. Therefore, in this specification, the communication device responsible for optical communication on the branch optical fiber side is referred to as the "active system," and the other communication device is referred to as the "standby system." Note that the term "optically connected" is not limited to two elements being directly connected, but also includes two elements being connected via an optical device.

[0017] (2) In the optical communication system described in (1) above, the active system and the standby system are connected by a control line for transmitting operational information and an optical fiber for connecting between the active system and the standby system in a multi-chassis link aggregation.

[0018] With this configuration, the active and standby systems can be switched back and forth by transmitting operational information between them via a control line. Furthermore, if data to be transmitted to the trunk optical fiber (or branch optical fiber) exists in the active system, that data can be transferred between the active and standby systems via the handover optical fiber. For example, when redundancy switching between the active and standby systems is performed by remote control, the time required for redundancy switching can be long. With this configuration, redundancy switching can be achieved in a shorter time.

[0019] (3) In the optical communication system described in (1) or (2) above, the active system transfers control authority to the standby system by redundancy switching.

[0020] According to this configuration, the subject of control can be easily switched during redundancy switchover, and therefore redundancy switchover can be achieved in a short time.

[0021] (4) In the optical communication system according to any one of (1) to (3) above, when a fault is detected in the multi-chassis link aggregation on the trunk optical fiber side, the working system determines whether or not to perform redundancy switching.

[0022] According to this configuration, redundancy switching can be performed not only when there is an abnormality in optical communication on the branch optical fiber side, but also when there is an abnormality in the multi-chassis link aggregation.

[0023] (5) In the optical communication system described in (4) above, if the failure in the multi-chassis link aggregation is a failure in the link aggregation of the active system, the active system performs redundancy switching, and the standby system performs optical communication on the branch optical fiber side and the trunk optical fiber side.

[0024] According to this configuration, in the event of a failure in the link aggregation of the active system, optical communication on the trunk optical fiber is performed by the link aggregation of the standby system. If the active system continues optical communication on the branch optical fiber, data needs to be transferred between the active system and the standby system. However, because the bandwidth on the trunk optical fiber is reduced, data transmission delays can become a problem. By having the standby system perform optical communication on the branch optical fiber and the trunk optical fiber, data transfer between the active system and the standby system does not occur, thereby solving the problem of data transmission delays.

[0025] (6) An optical communication device according to one embodiment of the present disclosure includes a first communication unit for communicating via a branch optical fiber, a second communication unit for communicating via a trunk optical fiber, and a control unit, wherein the control unit operates the first communication unit when the optical communication device is operated as a current system and also operates the second communication unit so that physical links on the trunk optical fiber side are logically bundled to form link aggregation, and the control unit outputs operational information regarding the operation of the current system from a port for communicating with other optical communication devices when the optical communication device is switched from a current system to a standby system.

[0026] According to this configuration, the optical communication device can be combined with other optical communication devices to form a redundant system. In the event of a failure in the working system, operation information for taking over the operation of the working system can be transferred to the other optical communication device by redundant switching. This allows the other optical communication device to take over the information regarding the operation of the original working system and handle communication for each of the trunk optical fiber and branch optical fiber. This enables the optical communication system to be miniaturized and operate stably.

[0027] (7) In the optical communication device described in (6) above, when the optical communication device operates in combination with another optical communication device, the operation of the optical communication device can be switched between a mode in which one of the optical communication device and the other optical communication device is used as the active system and the other is used as the standby system, allowing redundancy switching between the active system and the standby system, and a mode in which the optical communication device operates alone.

[0028] With this configuration, the optical communication device can operate both independently and in cooperation with other optical communication devices, allowing the operation of the optical communication device to be flexibly set according to the environment in which the optical communication device is installed.

[0029] (8) A control method for an optical communication system according to one embodiment of the present disclosure is a control method for an optical communication system having a first communication device and a second communication device, each configured to enable optical communication over a trunk optical fiber and a branch optical fiber, wherein the first communication device and the second communication device are optically connected to the branch optical fiber by a branching device provided on the branch optical fiber, one of the first communication device and the second communication device is a working system and the other is a standby system, the working system is responsible for optical communication on the branch optical fiber side, and the physical links on the trunk optical fiber side of each of the working system and the standby system are logically bundled to form a multi-chassis link aggregation, and the control method includes the steps of: the working system determining to perform redundant switching to the standby system; transferring operational information for taking over the operation of the working system from the working system to the standby system; and transferring control authority from the working system to the standby system.

[0030] According to this configuration, the optical communication system is composed of at least two communication devices. One of the two communication devices is assigned to a working system, and the other of the two communication devices is assigned to a standby system. This allows a redundant system to be configured. In the event of a failure in the working system, operational information for taking over the operation of the working system is transferred from the working system to the standby system by redundant switching. This allows the standby system to handle communications for both the trunk optical fiber and the branch optical fiber. This makes it possible to miniaturize the optical communication system and ensure stable operation.

[0031] (9) A control method for an optical communication device according to one embodiment of the present disclosure is a control method for an optical communication device that performs optical communication via a branch optical fiber and a trunk optical fiber, and includes the steps of: when operating the optical communication device as a working system, performing optical communication on the branch optical fiber side and logically bundling physical links on the trunk optical fiber side to form link aggregation; and when switching the optical communication device from the working system to a standby system, outputting operational information regarding the operation of the working system from a port for communicating with other optical communication devices.

[0032] With this configuration, the optical communication device can be combined with other optical communication devices to form a redundant system. In the event of a failure in the working system, the other optical communication device can take over information about the operation of the original working system and handle communications for both the trunk optical fiber and the branch optical fiber. This allows for the miniaturization and stable operation of the optical communication system.

[0033] [Details of the embodiments of the present disclosure] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0034] An optical communication system according to an embodiment of the present disclosure is an optical communication system configured to enable optical communication for each of a trunk optical fiber and a branch optical fiber. Therefore, the type or application of the optical communication system according to the embodiment of the present disclosure is not particularly limited. According to one embodiment, the optical communication system can be realized as an optical line terminal (OLT) of a PON system. A PON system will be described below as an application example of the embodiment of the present disclosure.

[0035] 1 is a diagram schematically illustrating an application example of an optical communication system according to an embodiment of the present disclosure. As shown in FIG. 1, a communication network 1000 includes devices that perform optical communication between a trunk optical fiber and a branch optical fiber. Specifically, the communication network 1000 includes an optical line terminal (OLT) 101 that functions as a trunk-branch device, and a trunk device 151 that is connected to an upper network 150.

[0036] The OLT 101 is connected to a trunk optical fiber and a branch optical fiber, and is configured to enable optical communication to each of the trunk optical fiber and the branch optical fiber. For example, the OLT 101 is installed in a remote station to realize a PON system for users in rural areas. The OLT 101 is configured to enable redundancy switching. In the example shown in FIG. 1, the optical communication unit 111A is the active system, and the optical communication unit 111B is the standby system. The configurations of the optical communication units 111A and 111B will be described in detail later. The branch optical fiber 211 is branched by an optical coupler 212. An ONU (ONU 311 is shown in FIG. 1 as an example), which is an optical line terminal, is connected to the branched branch optical fiber. The branch optical fiber 211 is further branched into two branch optical fibers 214 and 215 by an optical coupler 213. The PON card 20 of the optical communication unit 111A is optically connected to a branch optical fiber 214, and the PON card 20 of the optical communication unit 111B is optically connected to a branch optical fiber 215.

[0037] The PON cards 20 of the optical communication unit 111A are connected to each other by a physical link 44. The uplink ports of the PON cards 20 of the optical communication units 111A and 111B are connected to a trunk device 151 via trunk optical fibers 100A and 100B. The uplink physical links of the optical communication units 111A and 111B are logically combined into one to form a multi-chassis link aggregation (MC-LAG). The control cards 10 of the optical communication units 111A and 111B are connected to each other by a control line 45.

[0038] Fig. 2 is a diagram schematically illustrating the appearance of an optical communication unit constituting an optical communication system according to an embodiment of the present disclosure. As shown in Fig. 2, the optical communication unit 111 is a rack-mounted device housed in a housing 1. The optical communication unit 111 operates as an OLT by itself.

[0039] Each of the optical communication units 111A and 111B is realized by the optical communication unit 111 shown in Fig. 2. In one embodiment of the present disclosure, as shown in Fig. 1, the optical communication units 111A and 111B, which are two independent OLTs, cooperate to behave as if they were a single OLT.

[0040] Since the optical communication unit 111 can operate as an OLT by itself, the number of optical communication units constituting the OLT 101 is not particularly limited. The OLT 101 may be configured so that one optical communication unit 111 corresponds to one PON line. Alternatively, as shown in FIG. 1, two optical communication units 111 (optical communication units 111A and 111B) may be provided for one PON line (branch optical fiber). Redundancy switching can be performed between these two optical communication units (optical communication units 111A and 111B). The operation of the optical communication unit 111 can be switched between a mode that enables redundancy switching between a working system and a standby system, and a mode in which the optical communication unit 111 operates independently. Therefore, depending on the requirements for the optical communication unit 111, the operation of the optical communication unit 111 can be set to either a mode in which the optical communication unit 111 operates independently or a mode in which redundancy switching is possible.

[0041] Fig. 3 is a diagram showing an example of the external appearance seen from the front of the optical communication unit 111 shown in Fig. 2. As shown in Fig. 3, the optical communication unit 111 has a housing that is, for example, 1U in size for a 19-inch rack. "1U" is a pitch unit that specifies the mounting height on a rack as defined by the Electronic Industries Alliance (EIA) standard, and is approximately 44.45 mm.

[0042] The optical communication unit 111 includes a control card 10 and a PON card 20. The control card 10 includes a control port 11. In the example shown in FIG. 3, there is one control card 10 and one PON card 20. However, the embodiment of the present disclosure is not limited to one control card 10 or one PON card 20. The control port 11 includes ports 11A, 11B, and 11C. In this embodiment, at least one of the ports 11A, 11B, and 11C is used to transmit control signals to and from a control port of another optical communication unit. Note that at least one other port of the ports 11A, 11B, and 11C can also be used as a port for transmitting control signals to and from a control device (not shown), such as a control server.

[0043] The PON card 20 performs optical communication with an ONU (not shown in FIG. 3) via a PON line (not shown in FIG. 3) consisting of branch optical fibers, and also performs optical communication with devices on the trunk optical fiber side. The PON card 20 includes PON ports 21 for optical communication via the PON line and uplink ports 22 for optical communication with trunk devices. In the example shown in FIG. 3, the PON card has 16 PON ports 21. However, the number of PON ports 21 included in one PON card 20 is not limited as long as it can be accommodated within the size of the optical communication unit 111.

[0044] The PON ports 21 are configured to accept detachable optical transceivers having a predetermined form factor. For example, but not limited to, the PON ports 21 are configured to accept detachable SFP (Small Form-factor Pluggable) transceivers or SFP+ transceivers. In this configuration, each PON port 21 supports a transmission speed of 10 Gbps / 1 Gbps.

[0045] Like the PON port 21, the uplink port 22 is configured to allow optical transceivers having a predetermined form factor to be attached or detached. The configuration of the uplink port 22 is not particularly limited, but in the example shown in FIG. 3, the uplink port 22 includes two ports 22A configured to allow QSFP (Quad Small Form Factor Pluggable) 28 transceivers to be attached or detached, and four ports 22B configured to allow SFP+ transceivers to be attached or detached. Each of the two ports 22A supports a transmission speed of 100 Gbps, and each of the four ports 22B supports a transmission speed of 10 Gbps. In other words, the uplink port 22 supports a transmission speed higher than that of the PON port 21.

[0046] According to the embodiment of the present disclosure, the OLT 101 has multiple uplink ports. Therefore, the uplink side of the OLT 101 can be made redundant. The redundancy on the uplink side may be realized by one optical communication unit 111, or may be realized by at least two optical communication units 111. Although not shown in detail in the drawings described below, in order for the optical communication units 111 to perform optical communication with the branch optical fiber and the trunk optical fiber, optical transceivers are inserted into the corresponding PON ports and uplink ports, and optical fibers are optically connected to the optical transceivers.

[0047] FIG. 4 is a diagram illustrating a first example of a redundant configuration on the uplink side using an optical communication unit 111 according to an embodiment of the present disclosure. As shown in FIG. 4, the OLT 101 may be realized by a single optical communication unit 111. The connection (uplink) between the optical communication unit 111 and a trunk device (not shown) is realized by logically bundling the physical links 41 and 42 at the uplink port into one. In other words, a LAG is configured on the uplink side. By using the LAG, two physical links can be used simultaneously. Therefore, it is possible to improve the communication speed and fault tolerance in uplink communication.

[0048] 5 is a diagram illustrating a second example of a redundant configuration on the uplink side using optical communication units 111 according to an embodiment of the present disclosure. In the configuration illustrated in FIG. 5, the OLT 101 is realized by two optical communication units 111. In FIG. 5 and the diagrams described below, the two optical communication units 111 are referred to as "optical communication unit 111A" and "optical communication unit 111B" to distinguish them from one another. The physical links on the uplink side of the two optical communication units 111A and 111B are logically bundled to configure an MC-LAG.

[0049] Specifically, one uplink port (port 22A) of the optical communication unit 111A and one uplink port (port 22A) of the optical communication unit 111B are connected to a trunk device (not shown) via physical links 41 and 43, respectively, and the physical links 41 and 43 are logically bundled together. Furthermore, another uplink port of the optical communication units 111A and 111B is used as a crossover port.

[0050] The optical communication units 111A and 111B are connected to each other by a physical link 44 that connects the crossover ports. The physical link 44 is realized by an optical fiber and an optical transceiver. To realize the physical link 44, an active optical cable (AOC) or a direct attach cable (DAC) may be used. For example, the transmission bandwidth between the crossover ports is 100 Gbps. The physical link 44 forms an inter-chassis link (ICL). During normal operation, control traffic and BUM traffic (broadcast, unknown destination unicast, and multicast) pass through the ICL.

[0051] In both the configurations shown in Figure 4 and 5, the maximum bandwidth on the uplink side is 100 Gbps × 2 + 160 Gbps = 360 Gbps. In the configuration shown in Figure 5, the maximum bandwidth when the uplink is degenerated is 100 Gbps.

[0052] Fig. 6 is a block diagram showing the internal configuration of the optical communication unit 111 shown in Fig. 2. As shown in Fig. 6, the optical communication units 111A and 111B have the same configuration. The optical communication unit 111B differs from the optical communication unit 111A in that it performs optical communication with the ONU 332. Therefore, the configuration of the optical communication unit 111A will be described as a representative example.

[0053] The optical communication unit 111A includes a control card 10 and a PON card 20. The PON card 20 includes a PON-LSI 24 and a switch LSI (SW-LSI) 25.

[0054] When the chassis is started, the control card 10 confirms that the control card 10 and the PON card 20 are started, and then configures the PON card 20. This puts the PON card 20 into an operable state. The configuration of the control card 10 is performed by a control server 400 external to the optical communication unit 111A. In this embodiment, the configuration of the control card 10 or the synchronization of the PON card 20 is not performed between multiple communication units.

[0055] The PON-LSI 24 is provided corresponding to each PON port, and controls communication with the ONU 331 connected to the PON line via the PON port. The switch LSI 25 controls the flow of data inside the optical communication unit 111A.

[0056] Main signals (i.e., upstream and downstream data) are transmitted via a path connecting the UNI, ONU, PON-LSI, SW-LSI, and uplink. Therefore, the main signals do not pass through the backplane. Specifically, in the case of upstream data, the ONU 331 receives upstream data from a user terminal (not shown) via a UNI (User Network Interface) port. The ONU 331 transmits the upstream data to the optical communication unit 111A in the form of an optical signal. The PON-LSI 24 transfers the received upstream data to the switch LSI 25. The switch LSI 25 transfers the upstream data to a higher-level device via the uplink.

[0057] On the other hand, when the optical communication unit 111A receives downstream data from a higher-level device, the switch LSI 25 distributes the downstream data to the corresponding PON-LSI 24. The PON-LSI 24 that receives the downstream data transmits the downstream data to the corresponding PON line in the form of an optical signal. For example, if the destination of the downstream data is a user terminal connected to the ONU 331, the downstream data is sent to the ONU 331.

[0058] As described above, each of the optical communication units 111A and 111B has a standalone operation mode in which it can operate as an OLT by itself. The optical communication unit 111A is equipped with the number of PON ports allowed by the size of its housing, making it compact and suitable for introducing optical communication services to areas with a small number of users (e.g., rural areas). On the other hand, if the OLT is installed in a location remote from the usual location of a worker or engineer, the worker or engineer may not be able to immediately respond to a failure in the optical communication unit 111. Therefore, from the perspective of fault tolerance, it is desirable for the OLT to be redundant. In the embodiment of the present disclosure, PON protection (redundant configuration) can be achieved by using multiple optical communication units 111.

[0059] Fig. 7 is a diagram schematically illustrating the configuration of an OLT for achieving PON protection. As shown in Fig. 7, a branch optical fiber 211 is branched into two branch optical fibers 214 and 215 by an optical coupler 213 (branching device). The branched branch optical fibers 214 and 215 are optically connected via optical transceivers inserted into the PON ports 21 of the optical communication units 111A and 111B, respectively. Meanwhile, as described with reference to Fig. 5, an MC-LAG is configured on the uplink side of the optical communication units 111A and 111B.

[0060] The control cards 10 of the optical communication units 111A and 111B are connected to each other by connecting their ports 11A with a control line 45. The port 11A is a port for receiving and transmitting control signals. The control signals transmitted from the port 11A are electrical signals.

[0061] Due to the PON configuration, only one of the two optical communication units can communicate with the ONU. The optical communication unit 111A is a device (working system) that normally performs optical communication with the ONU, and is designated as "primary" in Fig. 7. On the other hand, the optical communication unit 111B is a device (standby system) that performs optical communication with the ONU when the working system fails, and is designated as "secondary" in Fig. 7.

[0062] FIG. 8 is a diagram showing state transitions of the active (primary) and standby (secondary) optical communication units shown in FIG. 7. First, the two optical communication units 111A and 111B are powered on, thereby starting up the two optical communication units 111A and 111B. The control server 400 shown in FIG. 6 configures the control cards 10 of the optical communication units 111A and 111B. As a result, the optical communication units 111A and 111B are configured to a mode enabling redundant switching. The control cards 10 of each optical communication unit configure the PON card 20. As a result, the PON card of the optical communication unit 111A is configured as the active system and enters an active (ACT) state. Meanwhile, the PON card of the optical communication unit 111B is configured as the standby system and enters a standby (SBY) state. Note that, on the uplink side, communication is possible regardless of whether the PON card 20 is in the active or standby state.

[0063] The PON side of the OLT 101 can have a 1:1 redundant configuration. If the PON card in the primary optical communication unit fails, the control card 10 of the primary optical communication unit changes the state of that PON card from active to standby. The control card 10 then sends a switchover command to the control card of the other (secondary) optical communication unit. In response to the switchover command, the control card 10 of the secondary optical communication unit changes the state of the PON card 20 from standby to active. As described above, due to the PON mechanism, only one of the two PON cards 20 is capable of communicating with the ONU. Therefore, only the active PON card 20 emits light, and the standby PON card 20 is in a non-light-emitting state. This executes redundancy switching.

[0064] In the embodiment of the present disclosure, redundancy switching is not performed by an instruction from a control server, but by an instruction from a primary optical communication unit to a secondary optical communication unit, so that the delay of redundancy switching can be short (instantaneous, so to speak).

[0065] When the cause of the failure of the optical communication unit 111A is removed, the optical communication unit 111A becomes operable. In this case, the control server 400 shown in FIG. 6 transmits a recovery command to each of the control cards 10 of the optical communication units 111A and 111B. In response to the recovery command, the optical communication unit 111A (primary) transitions its state from standby to active. Meanwhile, in response to the recovery command, the optical communication unit 111B (secondary) transitions its state from standby to active.

[0066] During redundancy switching, the primary optical communication unit transfers operational information, which is information about its operation, to the secondary optical communication unit. The operational information is transferred via the link between the control cards. This allows the information about the operation of the primary optical communication unit to be taken over by the secondary optical communication unit, allowing optical communication to continue for each of the trunk optical fiber and branch optical fiber. However, if a failure occurs in communication between the control cards, redundancy switching is not performed.

[0067] If a failure occurs in communication between the control card 10 and the PON card 20 inside the active optical communication unit, the power to the optical communication unit is turned off and the PON card of the standby optical communication unit is switched to the active state.

[0068] In the event of an internal failure of the active optical communication unit or an abnormality in the optical transceiver connected to the active optical communication unit, the optical communication unit stops emitting light and transitions to a standby state, so that the PON card in the standby optical communication unit switches to the active state.

[0069] Fig. 9 is a diagram showing the flow of downstream data during normal operation. As shown in Fig. 9, during normal operation, the uplink side of OLT 101 can widen the bandwidth by MC-LAG.

[0070] Figure 10 shows the flow of downstream data when the uplink of the primary optical communication unit fails. In the primary optical communication unit 111A, the PON link side is normal. Therefore, link switching on the PON side is not performed. The optical communication unit 111A continues communication with the ONU 311. In this case, downstream data from the uplink side is received only by the secondary optical communication unit 111B. The downstream data received by the optical communication unit 111B is sent to the optical communication unit 111A via the crossover port.

[0071] For example, assume that the normal uplink bandwidth is 200 Gbps (= 100 Gbps × 2) due to MC-LAG. Also, assume that the bandwidth of the crossover port is 100 Gbps. Note that these numerical values ​​are examples for ease of explanation and are not intended to limit the embodiments of the present disclosure.

[0072] As shown in Figures 9 and 10, when the secondary optical communication unit 111B receives downstream data, it transfers the downstream data to the primary optical communication unit 111A via the ICL. This causes a transmission delay. Under normal circumstances, the uplink bandwidth is 200 Gbps and the transfer port bandwidth is 100 Gbps, so the uplink bandwidth is significantly larger than the transfer port bandwidth. Therefore, the impact of the delay due to data transfer via the transfer port on the overall data transmission time is relatively small. However, if the uplink of the primary optical communication unit 111A fails, the overall uplink bandwidth of the optical communication units 111A and 111B decreases from 200 Gbps to 100 Gbps. Therefore, the impact of the delay due to data transfer via the transfer port on the overall data transmission time becomes relatively large.

[0073] 11 is a diagram showing the flow of downstream data when a failure occurs on the uplink side according to an embodiment of the present disclosure. As shown in FIG. 11, when a failure occurs in the uplink of the optical communication unit 111A (primary), the downstream data path is switched, and the downstream data is transmitted to the ONU via the uplink of the original standby system (new active system) and the PON side link. The downstream data is transmitted to the ONU without passing through the crossover port. Therefore, delays due to data transfer via the crossover port can be eliminated.

[0074] The flow direction of the upstream data may be considered to be opposite to the flow direction of the downstream data shown in Figures 9 to 11. Therefore, according to the embodiment of the present disclosure, even in the transmission of upstream data, it is possible to eliminate the influence of delay due to the bandwidth of the crossover port when a failure occurs in the uplink of the primary optical communication unit.

[0075] On the uplink side, communication is possible whether the PON card 20 is in the active or standby state. Therefore, during normal operation (see FIG. 9), a failure may occur in the uplink of the secondary optical communication unit 111B. In this case, however, the primary optical communication unit 111A can continue to operate independently. Therefore, no delay occurs due to data transfer via the crossover port.

[0076] Fig. 12 is a functional block diagram showing functions of an optical communication unit for realizing redundancy switching according to an embodiment of the present disclosure. Fig. 12 is a diagram explaining the configuration shown in Fig. 6 from the perspective of functional blocks. The configuration shown in Fig. 12 may be realized by hardware alone or by a combination of hardware and software. Since the optical communication units 111A and 111B have the same configuration, the configuration of the optical communication unit 111A will be described below as a representative.

[0077] The control card 10 includes a redundancy control unit 120. In the embodiment of the present disclosure, the redundancy control unit 120 corresponds to a "control unit" that controls the operation of the optical communication unit 111A when redundancy switching is performed.

[0078] The PON card 20 includes a status management unit 121, a PON link control unit 122, an MC-LAG control unit 123, and a concentrator 124. In the embodiment of the present disclosure, the PON link control unit controls the PON link between the optical communication unit 111A and the ONU. The PON link control unit corresponds to a "first communication unit" for communication via a branch optical fiber.

[0079] The concentrator 124 aggregates the uplink ports of the optical communication unit 111A. The MC-LAG controller 123 controls the MC-LAG configured from the uplinks of the optical communication units 111A and 111B. Although not limited thereto, the control of the MC-LAG may be, for example, Dynamic Link Aggregation (LACP) or Static Link Aggregation in accordance with the IEEE 802.1AX standard. In the embodiment of the present disclosure, the concentrator 124 and the MC-LAG controller 123 correspond to a "second communication unit" for communicating via the trunk optical fiber.

[0080] 13 is a sequence diagram illustrating the flow of redundancy switching when a failure occurs in the primary (working) PON side link. In step S10, the redundancy control unit 120 of the working system (optical communication unit 111A) inquires about the state of the PON link on the standby system side from the state management unit 121 of the standby system (optical communication unit 111A). In step S11, the state management unit 121 of the standby system returns information about the state of the PON link of the standby system to the redundancy control unit 120 of the working system. Communication between the redundancy control unit 120 of the working system and the state management unit 121 of the standby system may be performed, for example, via a control line 45 connecting the control port 11 of the working system and the control port 11 of the standby system. In this case, within the standby system, the control card 10 may mediate communication between the PON card 20 and the redundancy control unit 120 of the working system.

[0081] In step S12, the redundancy control unit 120 of the active system instructs the status management unit 121 of the active system to move data to the standby system. In step S13, the status management unit 121 of the active system moves data to the status management unit 121 of the standby system. This data includes data related to operational information for handing over operation of the active system to the standby system. The data related to operational information may be transferred from the active system to the standby system via a crossover port. The data related to operational information is transmitted directly between the two optical communication units without the intervention of control by a control server. This reduces the time required for redundancy switching.

[0082] When the data transfer is complete, in step S14, the status control unit 121 of the standby system notifies the status control unit 121 of the active system that the data transfer has been completed. In step S15, in response to the notification from the status control unit 121 of the standby system, the status control unit 121 of the active system notifies the redundancy control unit 120 of the active system that the data transfer from the active system to the standby system has been completed. As a result, the status control unit 121 of the active system returns a response to the instruction received from the redundancy control unit 120 of the active system.

[0083] In step S16, the redundancy control unit 120 of the active system instructs the PON link control unit 122 of the active system to block the optical transceiver for the PON link. The PON link control unit 122 of the active system stops the operation of the optical transceiver in response to the instruction. Therefore, the optical transceiver stops emitting light. In step S17, the PON link control unit 122 of the active system notifies the redundancy control unit 120 of the active system that the blocking of the optical transceiver of the active system has been completed.

[0084] When the blocking of the optical transceiver of the active system is completed, in step S18, the redundancy control unit 120 of the active system instructs the PON link control unit 122 of the standby system to release the optical transceiver for the PON link. In response to the instruction, the PON link control unit 122 of the standby system releases the optical transceiver for the PON link. This makes the optical transceiver for the PON link operational. In step S19, the PON link control unit 122 of the standby system notifies the redundancy control unit 120 of the active system that the release of the optical transceiver for the PON link is completed.

[0085] In step S20, the redundancy control unit 120 of the active system sends an instruction to the redundancy control unit 120 of the standby system to transfer control authority to the redundancy control unit 120 of the standby system. Thereafter, the original standby system operates as the new active system. This completes the redundancy switchover. With this configuration, the control entity can be easily switched during the redundancy switchover. Therefore, the redundancy switchover can be achieved in a short time.

[0086] 14 is a sequence diagram showing the flow of redundancy switching when a failure occurs in the uplink of the working system. As shown in FIG. 14, when a failure occurs on the uplink side of the working system, in step S1, the MC-LAG control unit 123 of the working system detects the failure. The MC-LAG control unit 123 of the working system notifies the redundancy control unit 120 of the working system of the occurrence of the failure. In response to the notification from the MC-LAG control unit 123 of the working system, the redundancy control unit 120 of the working system determines that redundancy switching should be performed and executes the redundancy switching. The subsequent processing flow is the same as the processing flow shown in FIG. 13, so description will not be repeated. As a result, optical communications on the uplink side and PON side are performed only by the original standby system (new working system) (see FIG. 11).

[0087] If a failure occurs on the uplink side of the standby system, the MC-LAG control unit 123 of the active system notifies the redundancy control unit 120 of the active system of the occurrence of the failure. However, in this case, since it is sufficient to continue the operation of the active system, the redundancy control unit 120 can determine that it is not necessary to perform redundancy switching.

[0088] As described above, according to the embodiment of the present disclosure, an optical communication system is configured with at least two optical communication units. One of the two optical communication units is assigned to a working system, and the other is assigned to a standby system. This allows for the configuration of a redundant system. Each optical communication unit is configured with a control card, a PON card portion, and an uplink port, which simplifies the overall configuration of the optical communication system. This allows for the optical communication system to be miniaturized and operated stably.

[0089] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments, and it is intended to include any modifications within the scope of the claims and meanings equivalent to the claims. [Explanation of symbols]

[0090] 1 chassis 10 Control Card 11 Control Port 11A, 11B, 11C, 21, 22A, 22B ports 20 PON Card 22 uplink ports 24 PON-LSI 25 Switch LSI 41~44 Physical Links 45 Control Line 100 trunk optical fiber 101,102 Main line-branch line equipment (OLT) 111, 111A, 111B Optical communication unit 120 Redundant control unit 121 Status Management Unit 122 PON link control unit 123 MC-LAG control section 124 Wire Concentrator 150 Upper Network 151 Main line equipment 211, 214, 215, 221 Branch optical fiber 212,213,222 Optical Coupler 311, 331, 332 Optical Line Unit (ONU) 400 Control Server 1000 Communication Network S1, S10 to S20 steps

Claims

1. 1. An optical communication system, comprising: a first communication device and a second communication device, each configured to be capable of optical communication with a trunk optical fiber and a branch optical fiber; the first communication device and the second communication device are optically connected to the branch optical fiber by a branching device provided on the branch optical fiber; one of the first communication device and the second communication device is a working system and the other is a standby system, and the working system is responsible for optical communication on the branch optical fiber side; physical links on the trunk optical fiber side of each of the active system and the standby system are logically bundled to form a multi-chassis link aggregation; the active system and the standby system are connected by a control line and an optical fiber for connecting between the active system and the standby system in the multi-chassis link aggregation, An optical communication system in which, when a failure in the multi-chassis link aggregation is a failure on the trunk optical fiber side of the active system, in redundant switching between the active system and the standby system, the active system transfers operational information for taking over the operation of the active system to the standby system via the control line, and the standby system performs optical communication on the branch optical fiber side and optical communication on the trunk optical fiber side without going through the optical fiber for the handover.

2. 2. The optical communication system according to claim 1, wherein said redundancy switching causes said active system to transfer control authority to said standby system.

3. 3. The optical communication system according to claim 1, wherein when the fault is detected in the multi-chassis link aggregation on the trunk optical fiber side, the active system determines whether or not to execute the redundancy switchover.

4. An optical communication device, a first communication unit for communicating via a branch optical fiber; a second communication unit for communicating via the trunk optical fiber; a control unit; the control unit, when operating the optical communication device as a working system, operates the first communication unit and also operates the second communication unit so that physical links on the trunk optical fiber side are logically bundled to form link aggregation; the control unit outputs operational information relating to an operation of the active system from a port for communicating with other optical communication devices when switching the optical communication device from the active system to a standby system due to a failure on the trunk optical fiber side of the active system; The control unit controls the optical communication device so that, when switching the optical communication device from a standby system to a new active system upon receiving the operational information, the optical communication device performs optical communication on the branch optical fiber side and optical communication on the trunk optical fiber side without going through a crossover port of the optical communication device.

5. The operation of the optical communication device is as follows: a mode in which, when the optical communication device operates in combination with the other optical communication device, one of the optical communication device and the other optical communication device is set as the active system and the other is set as the standby system, and redundancy switching is possible between the active system and the standby system; A mode in which the optical communication device operates independently can be switched between the above modes.

5. The optical communication device according to claim 4.

6. A control method for an optical communication system including a first communication device and a second communication device, each configured to be capable of optical communication with a trunk optical fiber and a branch optical fiber, comprising: the first communication device and the second communication device are optically connected to the branch optical fiber by a branching device provided on the branch optical fiber, one of the first communication device and the second communication device is a working system and the other is a standby system, the working system is responsible for optical communication on the branch optical fiber side, and physical links on the trunk optical fiber side of each of the working system and the standby system are logically bundled to form a multi-chassis link aggregation, the active system and the standby system are connected by a control line and an optical fiber for connecting between the active system and the standby system in the multi-chassis link aggregation, When the failure of the multi-chassis link aggregation occurs on the trunk optical fiber side of the working system, The control method includes: a step of determining that the active system should perform redundancy switching to the standby system; transferring operation information for taking over the operation of the active system from the active system to the standby system via the control line; a step of transferring control authority from the active system to the standby system, and switching the downstream data path to the standby system so that the standby system performs optical communication on the branch optical fiber side and optical communication on the trunk optical fiber side without using the optical fiber for the handover.

7. 1. A method for controlling an optical communication device that performs optical communication via a branch optical fiber and a trunk optical fiber, comprising: When the optical communication device is operated as a working system, optical communication is performed on the branch optical fiber side, and physical links on the trunk optical fiber side are logically bundled to form link aggregation; outputting operational information relating to the operation of the working system from a port for communicating with other optical communication devices when switching the optical communication device from the working system to a standby system due to a failure on the trunk optical fiber side of the working system; a step of controlling the optical communication device so that, when the optical communication device is switched from a standby system to a new active system upon receiving the operational information, the optical communication device performs optical communication on the branch optical fiber side and optical communication on the trunk optical fiber side without going through a crossover port of the optical communication device.

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