JP2018157518A - Communication system, optical line termination device and communication switching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system and the like capable of shortening a time required for completing communication switching.SOLUTION: A communication system comprises: a first OLT that connects between a first ONU and an optical line network; a second OLT that connects between a second ONU and the optical line network, and that is arranged at a position different from the first OLT; and an optical splitter that optically branches an optical signal between the first ONU and the first OLT to the second OLT. The second OLT has a monitoring unit, a generation unit, and a communication unit. The monitoring unit monitors optically-branched communication between the first OLT and the first ONU. The generation unit generates setting information used for the communication between the first ONU and the first OLT, from the monitoring result. The communication unit notifies the first OLT of stopping of the communication with the first ONU, and establishes communication with the first ONU on the basis of the setting information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication system, an optical line termination device, and a communication switching method.

  For example, in a PON (Passive Optical Network) communication system of FTTH (Fiber To The Home), an ONU (Optical Network Unit) that is an optical terminal device on the user side and an OLT (Optical Network) that is an optical line terminal device on the optical network side. Line Unit). The OLT aggregates a plurality of ONUs.

  For example, in the PON communication system defined by IEEE 802.3, multiple ONUs are connected to one OLT via an optical splitter, and bidirectional communication is realized using an optical fiber connecting the OLT and the ONU. doing. Accordingly, different optical wavelengths are used for data transmission from the OLT to the ONU and data transmission from the ONU to the OLT so that communication between the OLT and the ONU does not collide. For example, in data transmission from the OLT to the ONU, data is transmitted from the OLT to the subordinate ONUs all at once. In data transmission from the ONU to the OLT, data is transmitted by a time division multiplexing method based on setting information stored in a control frame from the OLT. The setting information is, for example, LLID (Logical Link Identifier), which is identification information of the ONU, reference time information for adjusting output timing, DBA (Dynamic Bandwidth Allocation) information, and the like. Each ONU sets the data transmission timing and transmission data amount of each ONU based on the setting information, and transmits data by the time division multiplexing method according to the setting contents.

  In the PON communication system, since the OLT is responsible for all communication in the system, if the OLT fails, the communication of the ONU under the failure OLT is cut off, which greatly affects the users of the ONU. Therefore, in order to avoid such an influence, for example, there is a PON communication system having a redundant configuration of two OLTs, that is, an operation OLT used for operation and a standby OLT that is switched when the operation OLT fails. In the PON communication system, the operation OLT and the standby OLT can be switched by an optical switch, and when a failure of the operation OLT is detected, the ONU under the operation OLT is switched from the operation OLT to the backup OLT, thereby communicating the ONU due to the operation OLT failure. Blocking can be avoided.

JP 2009-171041 A Japanese Patent Laid-Open No. 2006-143950

  However, in the PON communication system, when the operation OLT is switched from the operation OLT to the backup OLT due to a failure of the operation OLT, it is necessary for the backup OLT to communicate with ONUs under the operation OLT and acquire setting information again. As a result, when the setting information is acquired, the data communication of the ONU under the operation OLT is interrupted, and it takes time to complete the communication recovery, that is, the communication switching for switching from the operation OLT to the standby OLT.

  In one side, it aims at providing the communication system etc. which can shorten the time until completion of communication switching.

  One proposed communication system includes a first optical line terminator, a second optical line terminator, and an optical branching unit. The first optical line termination device connects the first optical termination device and the optical line network. The second optical line termination device connects the second optical termination device and the optical line network, and is disposed at a different position from the first optical line termination device. The optical branching unit transmits communication between the first optical terminator and the first optical line terminator and between the first optical terminator and the first optical line terminator. Is optically branched to the second optical line terminating device. The second optical line termination device includes a monitoring unit, a generation unit, and a communication unit. The monitoring unit monitors communication between the first optical line terminator and the first optical terminator optically branched by the optical branching unit. The generation unit generates setting information used for communication between the first optical terminal device and the first optical line terminal device from the monitoring result of the monitoring unit. The communication unit notifies the first optical line termination device of communication stoppage with the first optical termination device, and based on the setting information, communicates with the first optical termination device. Establish communication.

  Time to complete communication switching can be shortened.

FIG. 1 is an explanatory diagram illustrating an example of a PON communication system according to the first embodiment. FIG. 2 is an explanatory diagram illustrating an example of an external configuration of the OLT. FIG. 3 is an explanatory diagram illustrating an example of a functional configuration of the first OLT. FIG. 4 is an explanatory diagram illustrating an example of a functional configuration of the second OLT. FIG. 5 is an operation sequence illustrating an example of the OLT switching process of the PON communication system. FIG. 6 is a flowchart illustrating an example of the processing operation of the first OLT related to the monitoring process. FIG. 7 is a flowchart showing an example of the processing operation of the second OLT related to the setting process. FIG. 8 is an explanatory diagram illustrating an example of a time relationship of signal arrival of the first OLT, the second OLT, and the first ONU with respect to the first optical splitter. FIG. 9 is an explanatory diagram showing an example of a time relationship of signal arrival until a control frame arrives at the first ONU from the first OLT. FIG. 10 is an explanatory diagram illustrating an example of an operation sequence and a time relationship for setting a reference time for inter-OLT communication between the first OLT and the second OLT. FIG. 11 is an explanatory diagram illustrating an example of an operation sequence and a time relationship of regular communication between the first OLT and the first ONU. FIG. 12 is an explanatory diagram of an example of the PON communication system according to the second embodiment. FIG. 13 is an explanatory diagram illustrating an example of a shelf-type device.

  Hereinafter, embodiments of a communication system, an optical line termination device, and a communication switching method disclosed in the present application will be described in detail based on the drawings. The disclosed technology is not limited by the present embodiment. Moreover, you may combine suitably the Example shown below in the range which does not cause contradiction.

  FIG. 1 is an explanatory diagram illustrating an example of the PON communication system 1 according to the first embodiment. A PON communication system 1 shown in FIG. 1 is a communication system applied to, for example, a PON network in an FTTH network. The PON communication system 1 includes a plurality of ONUs 2, a first optical splitter 3A, a second optical splitter 3B, a first OLT 4A (4), and a second OLT 4B (4). Further, the PON communication system 1 includes a higher level aggregation SW 5, an aggregation SW 6, a core SW 7, a core network 8, and a higher level control device 9.

  The ONU 2 is, for example, an optical termination device that optically terminates the telephone 11 and the personal computer 12 in the user's home. For example, the ONU 2 of the users # 1 to #n is the first ONU 2A, for example, the ONU 2 of the users # 1A to #nA is the second ONU 2B. The first optical splitter 3A is connected to the first ONU 2A, the first OLT 4A, and the second OLT 4B through an optical fiber. The first optical splitter 3A transmits an optical signal between the first OLT 4A and the first ONU 2A under the first OLT 4A, and transmits an optical signal between the first OLT 4A and the first ONU 2A. The light is branched to the second OLT 4B. The first OLT 4A is a first optical line terminating device on the core network 8 side that aggregates the first ONUs 2A under its control. The second optical splitter 3B connects the second ONU 2B and the second OLT 4B with an optical fiber. The second optical splitter 3B transmits an optical signal between the second OLT 4B and the second ONU 2B under the second OLT 4B. The second OLT 4B is a second optical line terminating device on the core network 8 side that aggregates the second ONUs 2B under its control. The second OLT 4B is an optical line terminator arranged at a position different from that of the first OLT 4A. FIG. 2 is an explanatory diagram illustrating an example of an external configuration of the OLT 4. The OLT 4 shown in FIG. 2 is a pizza box type card, for example.

  The upper aggregation SW5 is an L2 switch that switches and connects the first OLT 4A and the second OLT 4B. The aggregation SW6 is an L3 switch that switches between the upper aggregation SW5 and the core SW7. The core SW 7 is a switch that switches between the core network 8 and the aggregation SW 6. The core network 8 is an optical line network. The host controller 9 is a controller that monitors and controls the OLT 4 in the PON communication system 1.

  FIG. 3 is an explanatory diagram illustrating an example of a functional configuration of the first OLT 4A. The first OLT 4A shown in FIG. 3 includes a first optical / electrical converter 21A and a first MAC (Media Access Controller) / PHY (Physical Layer) LSI (Large Scale Integration) 22A. The first OLT 4A includes a first field programmable gate array (FPGA) 23A, a higher level integrated SWIF (switch interface) 24, and a higher level control device IF25. The first optical / electrical conversion unit 21A is connected to an optical fiber, and has an electrical conversion function for electrically converting an optical signal from the optical fiber, and an optical conversion function for converting an electrical signal into an optical signal. The first PHY / MAC LSI 22A is a signal processing unit that executes PHY layer processing and MAC layer processing. The upper aggregation SWIF 24 is a communication IF with the upper aggregation SW5. The host controller IF 25 is a communication IF with the host controller 9.

  The first PHY / MAC LSI 21A includes a transmission unit 31, a transmission processing unit 32, a control frame generation unit 33, a timing generation unit 34, a reception unit 35, a reception processing unit 36, and a failure processing unit 37. . The transmission unit 31 is a circuit that transmits transmission data and a control frame to the ONU 2. The transmission processing unit 32 is a processing unit that generates transmission data. The control frame generation unit 33 is a circuit that generates a control frame. The timing generation unit 34 is a circuit that generates transmission timing of transmission data and control frames.

  The receiving unit 35 is a circuit that receives received data from the ONU 2. The reception processing unit 36 is a circuit that performs signal processing of received data, for example, distributes received data to data addressed to the ONU 2 or the upper aggregation SW 5. The failure processing unit 37 is a circuit that determines the validity of received data. The first FPGA 23 </ b> A includes a distribution unit 41 and a band adjustment unit 42. The distribution unit 41 is a circuit that distributes received data to the upper aggregation SW 5 and the ONU 2. The band adjustment unit 42 is a circuit that adjusts the band of received data after switching to the own system.

  FIG. 4 is an explanatory diagram illustrating an example of a functional configuration of the second OLT 4B. In addition, the same code | symbol is attached | subjected to the structure same as 1st OLT4A, and description about the overlapping structure and operation | movement is abbreviate | omitted. The second OLT 4B shown in FIG. 4 includes a first optical / electrical converter 21A, a first PHY / MAC LSI 22A, a first FPGA 23A, a higher level aggregation SWIF 24, a higher level control device IF25, and a monitoring device 26. Have The monitoring device 26 monitors communication between the first OLT 4A and the first ONU 2A through an optical fiber connected to the first optical splitter 3A.

  The monitoring device 26 includes a second optical / electrical conversion unit 21B, a second PHY / MAC LSI 22B, a second FPGA 27, and a storage unit 28. The second optical / electrical converter 21B includes an electrical conversion function that electrically converts an optical signal between the first OLT 4A to be monitored and the first ONU 2A under the first OLT 4A, and the electrical signal as an optical signal. And a light conversion function for conversion into The second PHY / MAC LSI 22B is a signal processing unit that executes PHY layer processing and MAC layer processing. The second PHY / MAC LSI 22B includes a transmission unit 31, a transmission processing unit 32, a control frame generation unit 33, a timing generation unit 34, a reception unit 35, a reception processing unit 36, and a failure processing unit 37. .

  The second FPGA 27 includes a monitoring unit 51 </ b> A, a determination unit 51, a first generation unit 52, a second generation unit 53, and a communication unit 54. The monitoring unit 51A monitors communication between the first OLT 4A and the first ONU 2A that are optically branched by the first optical splitter 3A. The determination unit 51 detects a failure of the first OLT 4A or the first ONU 2A under the first OLT 4A based on the monitoring result between the first OLT 4A and the first ONU 2A. The first generation unit 52 generates communication setting information based on a monitoring result between the first OLT 4A and the first ONU 2A under the first OLT 4A. The communication setting information includes the frame information and output band output to the upper aggregation SW 5, the LLID of the first ONU 2A under the first OLT 4A, and the encryption information when communicating with the first ONU 2A under the first OLT 4A. Etc.

  The second generation unit 53 generates timing information based on a monitoring result between the first OLT 4A and the first ONU 2A under the first OLT 4A. The second generation unit 53 includes basic timing information for executing monitoring and control of the first ONU 2A under the first OLT 4A, and the timing of regular communication between the first OLT 4A and the first ONU 2A under the control. Based on the timing information. The timing information is the monitoring / control timing for the second OLT 4B to communicate with the first ONU 2A under the first OLT 4A. The timing information includes response time information from each first ONU 2A for the first OLT 4A to perform time division multiplexing communication with the first ONU 2A under its control, and the first OLT 4A to the second OLT 4B. This is response time information from the second OLT 4B when the reference time is set.

  The communication unit 54 uses the optical wavelength for image communication defined in the PON communication, for example, without affecting the operation of data communication between the first OLT 4A and the first ONU 2A. Communicate with one OLT 4A. The communication unit 54 acquires the communication setting information of the first OLT 4A from the first OLT 4A. The communication setting information is information necessary for operations such as LLID (Logical Link Identifier), encryption information, bandwidth information, and priority processing used for communication between the first OLT 4A and the first ONU 2A. . Further, the communication setting information includes, for example, output band information, VLAN (Virtual Local Area Network) information, and installation information such as priority control, which are used for communication with the upper aggregation SW 5. The storage unit 28 includes communication setting information generated by the first generation unit 52, timing information generated by the second generation unit 53, and communication setting information of the first OLT 4A acquired by the communication unit 54. Is stored. The monitoring device 26 in the second OLT 4B monitors communication between the first OLT 4A and the first ONU 2A under the first OLT 4A.

  Next, the operation of the PON communication system 1 according to the first embodiment will be described. FIG. 5 is an operation sequence illustrating an example of the OLT switching process of the PON communication system 1. When the second OLT 4B receives the detection frame from the first OLT 4A (step S11), the second OLT 4B transmits a response frame to the first OLT 4A (step S12). The detection frame is a frame for detecting a newly arranged ONU 2 in the PON communication system 1 and a frame for searching for a spare OLT 4. The response frame is a frame indicating a response to the detection frame. When the first OLT 4A receives the response frame from the second OLT 4B, the first OLT 4A recognizes the presence of the second OLT 4B (step S13). When the first OLT 4A recognizes the presence of the second OLT 4B, the first OLT 4A transmits communication setting information on the first OLT 4A side to the second OLT 4B using inter-OLT communication (step S14).

  When the second OLT 4B receives the communication setting information, the second OLT 4B stores the communication setting information in the storage unit 28 (step S15). Thereafter, the first OLT 4A transmits a control frame to the subordinate first ONU 2A (step S16). Note that the first OLT 4A outputs a control frame at predetermined intervals. The second OLT 4B monitors the control frame from the first OLT 4A to the subordinate first ONU 2A through the first optical splitter 3A (step S17). Further, the subordinate first ONU 2A transmits a response frame to the control frame to the first OLT 4A (step S18). For convenience of explanation, a response frame is illustrated, but user data may be used instead of the response frame. The second OLT 4B monitors a response frame from the subordinate first ONU 2A to the first OLT 4A (step S19). The second OLT 4B monitors the periodic transmission cycle between the first OLT 4A and the subordinate first ONU 2A, and updates the timing information (step S20).

  Further, the first OLT 4A transmits a control frame to the subordinate first ONU 2A (step S16A). At this time, the second OLT 4B monitors the control frame from the first OLT 4A to the subordinate first ONU 2A through the first optical splitter 3A (step S17A). Further, the subordinate first ONU 2A transmits a response frame to the control frame to the first OLT 4A (step S18A). The second OLT 4B monitors a response frame from the subordinate first ONU 2A to the first OLT 4A (step S19A). The second OLT 4B monitors the periodic transmission cycle between the first OLT 4A and the subordinate first ONU 2A, and updates the timing information (step S20A).

  When there is no periodic control frame of the first OLT 4A (step S17B), the second OLT 4B determines that the communication between the first OLT 4A and the subordinate first ONU 2A is disconnected, and the first OLT 4A Abnormality is detected (step S21). When the second OLT 4B detects an abnormality in the first OLT 4A, the second OLT 4B notifies the host controller 9 and the first OLT 4A of the failure of the first OLT 4A (step S22). When the host controller 9 detects a failure notification, it executes a switching process (step S22A), and notifies the first OLT 4A of a switching instruction (step S23). The switching process is a process for switching the communication between the upper aggregation SW5 and the first OLT 4A to the communication between the upper aggregation SW5 and the second OLT 4B. When the first OLT 4A detects a switching instruction, the first OLT 4A stops monitoring / control of the subordinate first ONU 2A (step S24).

  The first OLT 4A stops the monitoring / control, and then notifies the second OLT 4B and the host control device 9 of the switching completion notification (steps S25 and S25A). The switching completion notification is, for example, a failure notification response frame. When the second OLT 4B detects the switch completion notification, the second OLT 4B starts monitoring and controlling the first ONU 2A under the first OLT 4A (step S26). As a result, the second OLT 4B can restore communication with the first ONU 2A instead of the first OLT 4A based on the communication setting information and timing information in the storage unit 28. That is, the second OLT 4B uses the communication setting information and the timing information, so that it is not necessary to detect the ONU 2 or perform the initial setting, so that the failure can be recovered in a short time. The second OLT 4B transmits the control frame to the subordinate first ONU 2A (step S27). Further, the subordinate first ONU 2A transmits a response frame to the control frame from the second OLT 4B to the second OLT 4B (step S28).

  FIG. 6 is a flowchart showing an example of the processing operation of the first OLT 4A related to the monitoring process. The first OLT 4A transmits a detection frame (step S31). The first OLT 4A determines whether or not a response frame corresponding to the detected frame has been received (step S32). If the first OLT 4A does not receive a response frame corresponding to the detected frame (No at Step S32), the first OLT 4A transmits a control frame to the subordinate first ONU 2A that has been set at a predetermined timing (Step S33).

  After transmitting the control frame, the first OLT 4A determines whether a response frame for the control frame has been received (step S34). When the first OLT 4A receives the control frame (Yes at Step S34), the first ONU 2A under control is determined to be normal (Step S35), and the processing operation shown in FIG. 6 is terminated. When the first OLT 4A does not receive a response frame to the control frame (No at Step S34), the first ONU 2A under the set is determined to be abnormal (Step S36), and the failure process is executed (Step S37). ), The processing operation shown in FIG.

  When the first OLT 4A receives a response frame for the detected frame (Yes at Step S32), the first OLT 4A determines whether the response frame is a response from the ONU 2 or the OLT 4 (Step S38). The ONU 2 and OLT 4 are identified by an LLID (Logical Link Identifier) or an identification code in an OAM (Operation Administration and Maintenance) area in the frame.

  When the response frame is a response from the ONU 2, the first OLT 4A transmits an initial setting to the new ONU 2 of the response (step S39). The first OLT 4A determines whether or not a response to the initial setting has been received from the new ONU 2 (step S40). When the first OLT 4A receives a response to the initial setting (Yes at Step S40), the first OLT 4A determines that the new ONU 2 is normal (Step S41), and ends the processing operation shown in FIG.

  If the first OLT 4A does not receive a response to the initial setting (No at Step S40), the first OLT 4A determines that the new ONU 2 is abnormal (Step S42), and proceeds to Step S37 to execute the failure process. If the response frame is a response from the OLT 4 in step S38, the first OLT 4A transmits a reference time frame to the response OLT 4 (step S43). The first OLT 4A determines whether or not a reference time setting completion as a response to the reference time frame has been received (step S44).

  If the first OLT 4A has not received the completion of the reference time setting (No at Step S44), the first OLT 4A determines whether or not an abnormal end notification has been received from the response OLT 4 (Step S45). When the first OLT 4A receives the abnormal end notification (Yes at Step S45), the first OLT 4A determines that the response OLT 4 is abnormal (Step S46), and proceeds to Step S37 to execute the failure process. If the first OLT 4A has not received the abnormal termination notification (No at Step S45), the first OLT 4A proceeds to Step S44 to determine whether or not the reference time setting completion has been received.

  When the first OLT 4A receives the completion of the reference time setting (Yes at Step S44), the first OLT 4A transmits the communication setting information and the reference time error information of the first OLT 4A to the second OLT 4B in response (Step S47). The first OLT 4A determines whether or not setting information completion, which is a response to the communication setting information of the first OLT 4A, has been received (step S48). When the first OLT 4A receives the setting information completion (Yes in step S48), the first OLT 4A ends the processing operation shown in FIG.

  When the first OLT 4A does not receive the setting information completion (No at Step S48), the first OLT 4A determines whether an abnormal end notification is received from the response OLT 4 (Step S49). When the first OLT 4A receives the abnormal termination notification (Yes at Step S49), the first OLT 4A determines that the response OLT 4 is abnormal (Step S50), and proceeds to Step S37 to execute the failure process. If the first OLT 4A has not received the abnormal termination notification (No at Step S49), the first OLT 4A proceeds to Step S48 to determine whether or not the setting information completion has been received.

  FIG. 7 is a flowchart showing an example of the processing operation of the second OLT 4B related to the setting process. In FIG. 7, the second OLT 4B determines whether a detection frame is received from the first OLT 4A (step S61). When the second OLT 4B receives the detection frame from the first OLT 4A (Yes in step S61), the second OLT 4B transmits connection information and device information, which are responses to the detection frame, to the first OLT 4A (step S62).

  The second OLT 4B determines whether or not a reference time frame has been received from the first OLT 4A (step S63). When the second OLT 4B receives the reference time frame (Yes at Step S63), the second OLT 4B sets the reference time (Step S64), and transmits the reference time setting completion to the first OLT 4A (Step S65). The second OLT 4B determines whether the communication setting information and the reference time error information are received from the first OLT 4A (step S66).

  When the second OLT 4B receives the communication setting information and the reference time error information from the first OLT 4A (Yes at Step S66), the second OLT 4B stores the communication setting information and the reference time error information in the storage unit 28 (Step S67). The second OLT 4B transmits setting information completion to the first OLT 4A (step S68), and ends the processing operation shown in FIG. Further, when the second OLT 4B does not receive the detection frame from the first OLT 4A (No at Step S61), the processing operation illustrated in FIG. 7 ends.

  If the second OLT 4B does not receive the reference time frame from the first OLT 4A (No at Step S63), the second OLT 4B transmits an abnormal end notification to the first OLT 4A (Step S69), and whether or not a detection frame is received. The process proceeds to step S61. When the second OLT 4B does not receive the communication setting information and the reference time error information from the first OLT 4A (No at Step S66), the second OLT 4B transmits an abnormal end notification to the first OLT 4A (Step S70). Then, the second OLT 4B proceeds to step S61 in order to determine whether or not a detection frame has been received.

  When switching from the first OLT 4A to the second OLT 4B, the output timing of the control frame of the second OLT 4B is set so that the control frame of the first ONU 2A under the first OLT 4A before switching can be received at the same timing. Need to adjust.

  FIG. 8 is an explanatory diagram illustrating an example of a time relationship of signal arrival of the first OLT 4A, the second OLT 4B, and the first ONU 2A with respect to the first optical splitter 3A. FIG. 8 shows the time relationship until the first OLT 4A arrives at the first ONU 2 under the second OLT 4B and the first OLT 4A via the first optical splitter 3A. For convenience of explanation, the signal arrival time between the first OLT 4A and the first optical splitter 3A is ta, the signal arrival time between the second OLT 4B and the first optical splitter 3A is tx, and the first The signal arrival time between the first optical splitter 3A and the first ONU 2A of # 1 is tb1. The signal arrival time between the first optical splitter 3A and the first ONU 2A of # 2 is tb2, and the signal arrival time between the first optical splitter 3A and the first ONU 2A of #m is tbm. To do.

  FIG. 9 is an explanatory diagram showing an example of the time relationship of signal arrival until the control frame reaches the first ONU 2A from the first OLT 4A. The first OLT 4A transmits the control frame to the first ONU 2A and the second OLT 4B under the first OLT 4A via the first optical splitter 3A. The transmission time of the control frame of the first OLT 4A is T1, the reception time of the control frame of the first optical splitter 3A is T2, the reception time of the control frame of the first ONU 2A is T3, and the reception of the control frame of the second OLT 4B The time is T4.

  To prevent the reception time T3 of the first ONU 2A from shifting before and after switching from the first OLT 4A to the second OLT 4B, the same as the reception time T2 of the control frame on the first optical splitter 3A before and after the switching. It is necessary to. The second OLT 4B takes tx as a signal arrival time until the control frame arrives from the first optical splitter 3A. Therefore, the timing T5 at which the second OLT 4B after switching transmits the control frame is a delay time between the first optical splitter 3A and the first OLT 4A from the reception time T4 of the control frame from the first OLT 4A. The timing is obtained by subtracting the time (2tx) that is twice tx. As a result, the control frame reception time T3 on the first ONU 2A is the same as the control frame reception time before and after switching. The method for calculating the time of 2tx is as follows.

  FIG. 10 is an explanatory diagram showing an example of an operation sequence and a time relationship for setting a reference time for inter-OLT communication between the first OLT 4A and the second OLT 4B. The first OLT 4A stores the frame transmission time: T in the reference time frame for setting the reference time of the second OLT 4B, and transmits the reference time frame to the second OLT 4B. The second OLT 4B corrects the internal time T ′ (= T) at the data transmission time T in the received reference time frame. Based on the internal time T ′, the second OLT 4B stores the data transmission time: Tm ′ in the response frame, and transmits the response frame to the first OLT 4A. When the first OLT 4A receives the response frame, the first OLT 4A obtains the response frame reception time: Tn. The second OLT 4B stores the reception time Tn in the frame, and transmits the frame to the first OLT 4A.

  The time (Tn-T) required for the reference time setting communication is the signal arrival time ta between the first OLT 4A and the first optical splitter 3A, and the time between the first optical splitter 3A and the second OLT 4B. Let tx be the signal arrival time. In this case, Tn−T = ta + tx + (Tm′−T ′) + tx + ta (Formula 1). When formula (1) is arranged, formula (2) of Tn−Tm ′ = 2ta + 2tx−T + T ′ is obtained. Furthermore, since T and T ′ have the same value, Tn−Tm ′ = 2ta + 2tx (Formula 3).

  FIG. 11 is an explanatory diagram illustrating an example of an operation sequence and a time relationship of regular communication between the first OLT 4A and the first ONU 2A. The signal arrival time between the first ONU 2A under the first OLT 4A and the first optical splitter 3A is tbα, from the start of control frame transmission of the first OLT 4A to the reception of the response frame from the subordinate first ONU 2A. Is assumed to be Tonuα. Furthermore, the response time of the first ONU 2A under the first OLT 4A during monitoring by the second OLT 4B is T'onu α, the ONU number is α (1... M), and the internal delay of the first ONU 2A is Δβ. In this case, the response time (Tonuα) of the first ONU 2A of the first OLT 4A is as follows (Formula 4): Tonuα = ta + tbα + Δβ + tbα + ta = 2ta + 2tbα + Δβ. Further, the response time (T′onuα) of the first ONU 2A under the control of the first OLT 4A at the time of monitoring by the second OLT 4B is as follows (Equation 5): T′onuα = ta + tbα + Δβ + tbα + tx− (ta + tx) = 2tbα + Δβ . (Formula 4)-(Formula 5) gives (Formula 6) of Tonuα-T′onuα = 2ta.

  The time ta in (Expression 3) and (Expression 6) is the signal arrival time between the first OLT 4A and the first optical splitter 3A, and is the same value if the networks are the same. Therefore, by substituting the value of 2ta obtained by (Formula 5) into (Formula 4), (Formula 7) is obtained by Tn−Tm ′ = (Tonuα−T′onuα) + 2tx.

  A time 2tx that is twice the signal arrival time tx between the first optical splitter 3A and the second OLT 4B is (Tn−Tm ′) − (Tonuα−T′onuα). In the reference time setting between the first OLT 4A and the second OLT 4B, the response frame reception time Tn from the second OLT 4B on the first OLT 4A, and between the first OLT 4A and the second OLT 4B The response frame transmission time Tm ′ of the second OLT 4B to be used in the reference time setting becomes a fixed value when the network construction is completed. As for Tonuα, which is the response time of the first ONU 2A under the first OLT 4A, the second OLT 4B can acquire information from the first OLT 4A. Regarding T'onuα, which is the response time of the first ONU 2A under the control of the first OLT 4A monitored by the second OLT 4B, the second OLT 4B monitors the communication of the first ONU 2A under the control of the first OLT 4A. By doing so, a value can be obtained, and a fixed value can be obtained.

  Tonuα and T′onuα may be changed by, for example, replacement of the first ONU 2A under the first OLT 4A, and the second OLT 4B may change the first one when the value of T′onuα changes. It is necessary to inquire the value of Tonuα again on the OLT 4A side. Further, the values of Tonuα and T′onuα after switching are the same values because the second OLT 4B performs the replacement of the first OLT 4A, and when the values are changed, the first ONU 2A under the normal operation is changed. Will be treated as a change.

  The failure determination is performed by monitoring periodic communication of control frames from the first OLT 4A on the second OLT 4B. The second OLT 4B can monitor the communication of a specific ONU 2 by using information such as LLID for identification of ONU and MAC in the control frame. As a result, the second OLT 4B not only monitors the total number of transmission frames from the first OLT 4A, but also detects the periodic transmission abnormality to a specific ONU 2 and the detection of an intermittent failure of a control frame for an arbitrary ONU 2. The failure of one OLT 4A can be determined.

  When the second OLT 4B detects a failure of the first OLT 4A, the second OLT 4B transmits a failure notification to the first OLT 4A and the host controller 9 through inter-OLT communication. The host control device 9 executes a switching process from the first OLT 4A to the second OLT 4B for the upper aggregation SW 5 in response to the failure notification. Upon receiving the failure notification, the first OLT 4A returns a failure notification reception response to the second OLT 4B, and stops monitoring and controlling the subordinate ONU 2. After receiving the failure notification response, the second OLT 4B starts control / monitoring of the ONU 2 under the first OLT 4A. As a result, the second OLT 4B can restore communication with the first ONU 2A instead of the first OLT 4A based on the communication setting information and timing information in the storage unit 28. That is, the second OLT 4B uses the communication setting information and the timing information, so that it is not necessary to detect the ONU 2 or perform the initial setting, so that the failure can be recovered in a short time.

  In the first embodiment, the first optical splitter 3A connected to the first OLT 4A and the first OLT 4A and the second OLT 4B at a different location are connected by an optical fiber. The second OLT 4B monitors the regular communication between the first OLT 4A and the first ONU 2A under the first OLT 4A, and generates setting information of the first OLT 4A from the monitoring result. As a result, compared with the prior art, periodic exchange of information between the first OLT 4A and the second OLT 4B becomes unnecessary, and the network can be operated efficiently.

  The second OLT 4B monitors communication between the first OLT 4A and the first ONU 2 under the first OLT 4A, and executes failure determination based on the monitoring result. As a result, it is possible to accurately determine whether the first OLT 4A or the first ONU 2A under the first OLT 4A is in failure. Furthermore, it becomes possible to determine an intermittent failure of data transmitted and received by time axis multiplexing, and an accurate and quick failure determination can be realized.

  The second OLT 4B acquires initial setting information through inter-OLT communication with the first OLT 4A, and the first ONU 2A is a communication monitor between the first OLT 4A and the first ONU 2A under the first OLT 4A. The time-division multiplexing timing information is updated in real time. As a result, since the re-recognition of the first ONU 2A at the time of switching becomes unnecessary, the time until failure recovery can be shortened.

  In the PON communication system 1, communication between the first OLT 4 </ b> A and the second OLT 4 </ b> B can be performed between OLTs without an ONU, so that it is possible to avoid interruption of operation of data communication with the subordinate ONU 2 due to inter-OLT communication. As a result, efficient operation of the PON communication system 1, accurate failure determination in the PON section, and shortening of processing time until early failure recovery can be achieved.

  The second OLT 4B updates, in real time, the time division multiplexing timing of the first ONU 2A necessary for the operation after switching based on the monitoring result of the communication between the first OLT 4A and the first ONU 2A. The switching time from the first OLT 4A to the second OLT 4B is shortened. Furthermore, in the PON communication system 1, the second OLT 4B that is operating the second ONU 2B is used in the vicinity of the first OLT 4A, rather than installing a device for the failure of the first OLT 4A outside. Thus, communication recovery from an OLT failure can be performed quickly.

  In the PON communication system 1 according to the first embodiment, inter-OLT communication can be performed between the first OLT 4A and the second OLT 4B via the first optical splitter 3. However, in the PON communication system 1, when inter-OLT communication between the first OLT 4A and the second OLT 4B is not supported, the first OLT 4A and the second OLT 4B are connected via the host controller 9. Data communication may be executed between them.

  The upper aggregation SW5 stops data reception from the first OLT 4A and enables data reception from the second OLT 4B. In the second OLT 4B, the communication between the second ONU 2B subordinate to the second OLT 4B and the first ONU 2A subordinate to the first OLT 4A is congested in communication with the upper aggregation SW 5 to maintain communication stability. It may be possible that this is not the case. Therefore, the second OLT 4B may perform bandwidth management on the data of the first ONU 2A under the control of the first OLT 4A using priority information stored in advance as communication setting information.

  In the PON communication system 1 of the first embodiment, the first OLT 4A is configured as shown in FIG. 3, but the monitoring device 26 may be built in the first OLT 4A. The embodiment in this case will be described below as Example 2.

  FIG. 12 is an explanatory diagram of an example of the PON communication system 1A according to the second embodiment. The same components as those in the PON communication system 1 according to the first embodiment are denoted by the same reference numerals, and the description of the overlapping configuration and operation is omitted.

  The difference between the PON communication system 1 of the first embodiment and the PON communication system 1A of the second embodiment is that a third OLT 4C having a built-in monitoring device 26 is provided instead of the first OLT 4A.

  Further, the second optical splitter 3B is connected to the third OLT 4C by an optical fiber in addition to the second OLT 4B and the second ONU 2B under the second OLT 4B. The third OLT 4C monitors the regular communication between the second OLT 4B and the second ONU 2B under the second OLT 4B via the second optical splitter 3B.

  The second OLT 4B aggregates the second ONUs 2B of the users # 1A to #nA, and the communication with the second ONU 2B is in operation. In addition, the third OLT 4C aggregates the first ONUs 2A of the users # 1 to #n, and communication with the first ONU 2A is in operation.

  That is, the second OLT 4B monitors the regular communication between the third OLT 4C and the first ONU 2A under the third OLT 4C through the second optical splitter 3B. Similarly, the third OLT 4C monitors the regular communication between the second OLT 4B and the second ONU 2B under the second OLT 4B through the first optical splitter 3A.

  The second OLT 4B generates communication setting information and timing information of the third OLT 4C based on the monitoring result, and stores the communication setting information and timing information of the third OLT 4C in the storage unit 28. Further, the third OLT 4C generates communication setting information and timing information of the second OLT 4B based on the monitoring result, and stores the communication setting information and timing information of the second OLT 4B in the storage unit 28.

  When the second OLT 4B detects a failure on the third OLT 4C side based on the monitor result, the second OLT 4B switches from the third OLT 4C to the first ONU 2A based on the communication setting information and timing information of the third OLT 4C. . As a result, the second OLT 4B can quickly restore the first ONU 2A under the third OLT 4C even when a failure on the third OLT 4C side is detected. In addition, when the third OLT 4C detects a failure on the second OLT 4B side based on the monitoring result, the third OLT 4C determines the second ONT 2B under the second OLT 4B based on the communication setting information and timing information of the second OLT 4B. Switch connection. As a result, the third OLT 4C can quickly restore the second ONU 2B under the second OLT 4B even when a failure on the second OLT 4B side is detected.

  In the PON communication system 1A, since the third OLT 4C and the second OLT 4B monitor communication with each other, mutual monitoring is performed between the third OLT 4C and the second OLT 4B without using an extra band. Switching is possible.

  In the above embodiment, the pizza box type OLT 4 is exemplified, but a shelf type device on which a plurality of OLT cards are mounted may be used. FIG. 13 is an explanatory diagram illustrating an example of the shelf-type device 100. The shelf type apparatus 100 shown in FIG. 13 includes a plurality of OLT cards 111, a SW card 112, and a CPU card 113. The OLT card 111 is an IF card on which the OLT 4 is mounted. The SW card 112 is a SW that switches and connects the OLT cards 111 to each other. The CPU card 113 is a card that controls the entire shelf type device 100. The first OLT 4A and the second OLT 4B are OLT cards 111 built in different shelf type devices 100.

  In addition, each component of each part illustrated does not necessarily need to be physically configured as illustrated. In other words, the specific form of distribution / integration of each part is not limited to the one shown in the figure, and all or a part thereof may be functionally or physically distributed / integrated in arbitrary units according to various loads and usage conditions. Can be configured.

  Furthermore, various processing functions performed in each device are performed on a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit), MCU (Micro Controller Unit), etc.) in whole or in part. You may make it perform. Various processing functions may be executed entirely or arbitrarily on a program that is analyzed and executed by a CPU (or a microcomputer such as an MPU or MCU) or hardware based on wired logic. Needless to say.

1 PON communication system 2A First ONU
2B Second ONU
3A 1st optical splitter 3B 2nd optical splitter 4A 1st OLT
4B 2nd OLT
51A Monitoring Unit 51 Determination Unit 52 First Generation Unit 53 Second Generation Unit 54 Communication Unit

Claims (5)

A first optical line terminator for connecting the first optical terminator and the optical line network;
A second optical line terminator connected to the second optical terminator and the optical line network, and disposed at a position different from the first optical line terminator;
Communication between the first optical terminator and the first optical line terminator is transmitted, and communication between the first optical terminator and the first optical line terminator is the first. An optical branching unit that splits the light into two optical line terminators,
The second optical line terminator is:
A monitoring unit that monitors communication between the first optical line termination device and the first optical termination device that are optically branched at the optical branching unit;
A generating unit that generates setting information used for communication between the first optical terminal device and the first optical line terminal device from a monitoring result of the monitoring unit;
Notifying the first optical line termination device that communication with the first optical termination device is stopped, and establishing communication with the first optical termination device based on the setting information A communication system comprising: a communication unit. A determination unit that determines whether a failure on the first optical network unit side is detected based on a monitoring result of the monitoring unit;
The communication unit is
When a failure on the first optical line termination device side is detected, a communication stop with the first optical termination device is notified to the first optical line termination device. Item 12. The communication system according to Item 1. The generator is
A first generation unit that generates communication setting information related to identification information for each first optical termination device;
The reception timing of the control signal reaching the first optical termination device from the first optical network termination device is the reception timing of the control signal reaching the first optical termination device from the second optical network termination device. 3. The communication system according to claim 1, further comprising: a second generation unit configured to generate timing information for adjusting an output timing of the second optical line terminator so as to coincide with each other. An optical line termination device for connecting an optical termination device and an optical network,
Connect to another optical terminator, connect to the optical branching unit that optically branches communications between other optical line terminators and other optical terminators located at different positions from the optical line terminator. A monitoring unit for monitoring communication between the other optical line terminator branched and the other optical terminator;
A generating unit that generates setting information used for communication between the other optical termination device and the other optical line termination device from a monitoring result of the monitoring unit;
A communication unit that notifies the other optical line terminator of the communication stop with the other optical terminator and establishes communication with the other optical terminator based on the setting information; An optical line terminating device comprising: A first optical line terminator for connecting the first optical terminator and the optical line network;
A second optical line terminator connected to the second optical terminator and the optical line network, and disposed at a position different from the first optical line terminator;
Communication between the first optical terminator and the first optical line terminator is transmitted, and communication between the first optical terminator and the first optical line terminator is the first. A communication switching method for a communication system having an optical branching unit that splits light into two optical line terminators,
The second optical line terminator is:
Monitoring communication between the first optical line terminator and the first optical line terminator optically branched at the optical branch unit;
Generating setting information used for communication between the first optical terminator and the first optical line terminator from the monitoring result;
Notifying the first optical line termination device that communication with the first optical termination device is stopped, and establishing communication with the first optical termination device based on the setting information A communication switching method characterized by executing processing.

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