JP2014209773A - Communication control method, maintenance management method, and station side device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent instantaneous interruption of communication when redundant switching is performed in a communication system having a redundant configuration.SOLUTION: In a station side device 1a, each optical line unit 12 transmits a downlink communication signal to a plurality of house side devices 2 via an optical switch 11a, and receives uplink communication signals from the plurality of house side devices 2 via the optical switch 11a. A control unit 14 controls switching timing of the optical switch 11a and transmission timing of the plurality of house side devices 2 so that the optical switch 11a will not receive the uplink communication signals from the plurality of house side devices 2 during the switching transition period from start to completion of the switching in which the optical switch 11a switches from a communication path outputting a downlink communication signal received from a switching source optical line unit 12 to a passive optical network 3 to a communication path outputting a downlink communication signal received from a switching destination optical line unit 12 to the passive optical network 3.

Description

  The present invention relates to a PON (Passive Optical Network) that is a medium-shared communication in which a plurality of home-side devices share a medium and transmit data, and in particular, a plurality of optical line units (hereinafter referred to as OSUs) that terminate at a station side. The present invention relates to a communication control method, a maintenance management method, and a station-side device that have a fault-tolerant function improved by making the network (Optical Subscriber Unit) redundant.

  In recent years, the Internet has become widespread, and users can access various information on sites operated in various parts of the world and obtain the information. Along with this, devices capable of broadband access such as ADSL (Asymmetric Digital Subscriber Line) and FTTH (Fiber To The Home) are rapidly spreading.

  As prior arts related to this, there are technologies disclosed in Patent Document 1, Patent Document 2, and Non-Patent Document 1 below. In the invention disclosed in Patent Document 1, the working optical termination unit communicates with a plurality of user optical termination devices via an optical transmission line. The unit includes a management information storage device that stores management information of a plurality of user optical terminal devices. The backup optical termination unit includes a storage device capable of storing the management information transferred from the active optical termination unit. The control device controls switching from the working optical termination unit to the backup optical termination unit.

  In the invention disclosed in Patent Document 2, an L3 switch having a port mirroring function is arranged upstream of a station side device (OLT (Optical Line Terminal)), and a 2: 1 optical coupler is arranged downstream. Before starting the switching, the management information and the setting information are transferred from the first OLT to the second OLT. When a special frame indicating the start of switching is input from the switch to the first and second OLTs, the first OLT stops taking downlink data, and the second OLT starts taking downlink data. Temporarily suspending bandwidth allocation to the home side device (ONU (Optical Network Unit)), instructing the second OLT to capture upstream data, and restarting bandwidth allocation to the ONU. When there is no downlink data of the first OLT, the management information is transferred from the first OLT to the second OLT. The second OLT is operated in a normal operation.

  Non-Patent Document 1 describes one method of PON. All information including user information passing through the PON and control information for managing and operating the PON is in the form of an Ethernet (registered trademark) frame. An EPON (Ethernet (registered trademark) PON) to be communicated, an EPON access control protocol (MPCP (Multi-Point Control Protocol)), and an OAM (Operations, Administration and Maintenance) protocol are defined. By exchanging MPCP frames between the station side device and the home side device, the home side device joins and leaves, and uplink access multiplexing control is performed.

  Even in 10GEPON (EPON corresponding to a communication speed of 10 Gbps) that is standardized as IEEE 802.3av, MPCP is assumed as the access control protocol.

  Patent Document 3 shows that a layer 2 switch (L2SW) is generally used to further aggregate the uplinks of a plurality of PONs. In L2SW, relay processing is performed in units of terminal MAC addresses.

JP 2007-036926 A JP 2007-067601 A JP 2004-201013 A

IEEE Std 802.3ah (registered trademark) -2004

  By the way, in general, in a network service for business, in order to provide a high quality service, it is essential to make a system redundant (redundant). Also, a highly reliable system can be provided by using a duplex system in an audio / video distribution service. In the redundant system, a redundant configuration is adopted in which each of the devices, components, and network has an active system and a standby system as required. When a failure occurs in a part of the operating system, it is possible to make the system stop time due to the failure as short as possible by performing redundant switching from the active system to the standby system.

  Even if a failure has not become apparent, the module may be replaced proactively in consideration of the deterioration tendency of characteristics, the life of parts, and the like. If the system has a redundant configuration for the module, it is possible to shorten the system stop time due to such maintenance work as much as possible.

  In a PON having a redundant configuration, for example, in an optical switch, switching from a communication path using an active OSU to a communication path using a standby OSU is performed. Here, since a certain amount of time is required for the switching destination path in the optical switch to become stable, switching the communication path by the optical switch without stopping the transmission of the communication signal causes an unstable switching. Communication signals that pass through the previous path are discarded. If it does so, a momentary interruption will occur in communication between the station side device and the home side device in the transition period of switching of the optical switch.

  However, Patent Documents 1 to 3 and Non-Patent Document 1 do not disclose a configuration for solving such a problem.

  Therefore, an object of the present invention is to provide a communication control method, a maintenance management method, and a station-side device capable of preventing instantaneous interruption of communication when performing redundant switching in a communication system having a redundant configuration. is there.

  In order to solve the above-described problem, a communication control method according to an aspect of the present invention includes a plurality of standby optical line units that communicate with a plurality of home-side devices via a plurality of passive optical networks. , An optical switch for switching communication paths between a plurality of passive optical networks and a plurality of optical line units, and control for controlling switching of the optical switch and transmission of uplink communication signals by a plurality of home-side devices Each optical line unit transmits a downlink communication signal to a plurality of home devices via an optical switch, and receives an upstream communication signal from the plurality of home devices via an optical switch. A communication control method in which a switching source optical line unit stops outputting a downstream communication signal to an optical switch, and received from the switching source optical line unit Switching from the communication path that outputs the communication signal to the passive optical network to the communication path that outputs the downlink communication signal received from the switching destination optical line unit to the passive optical network is completed after the optical switch starts. A step of setting a switching timing of the optical switch and a transmission timing of the plurality of home-side devices so that the optical switch does not receive uplink communication signals from the plurality of home-side devices during the switching transition period up to Includes a step of switching the communication path based on the set switching timing, and a step of starting output of the downlink communication signal to the optical switch by the switching destination optical line unit.

  Preferably, the station side device further includes a concentrating unit that distributes the downlink communication signal from the upper network to each optical line unit, and each optical line unit has a buffer for storing the downlink communication signal received from the concentration unit. The accumulated downlink communication signals are transmitted to a plurality of home-side devices via the optical switch, and the communication control method further includes a concentrator that selects the output destination of the downlink communication signal before the optical switch switches the communication path. Including the step of switching from the switching source optical line unit to the switching destination optical line unit, and in the step of setting the switching timing and the transmission timing, the control unit downloads the switching source optical line unit stored in its own buffer. Predict the timing to complete the transmission of the communication signal, after the predicted timing and longer than the switching transition period And a plurality of optical network units is set to a gap period for stopping the transmission of the uplink communication signal, the switching transition period to set the switching timing of the optical switch to be included in the gap period.

  Preferably, the station side device further includes a concentrating unit that distributes the downlink communication signal from the upper network to each optical line unit, and each optical line unit has a buffer for storing the downlink communication signal received from the concentration unit. The accumulated downlink communication signals are transmitted to a plurality of home-side devices via the optical switch, and the communication control method further includes a concentrator that selects the output destination of the downlink communication signal before the optical switch switches the communication path. Including the step of switching from the switching source optical line unit to the switching destination optical line unit, and in the step of setting the switching timing and the transmission timing, the control unit downloads the switching source optical line unit stored in its own buffer. In response to the notification that the transmission of the communication signal is completed, it is longer than the switching transition period and a plurality of home side devices Set the gap period to stop sending, to set the switching timing of the optical switch so that switching transition period included in the gap period.

  More preferably, in the step of setting the switching timing and the transmission timing, the control unit sets a plurality of gap periods, and the downlink communication in which the switching source optical line unit is accumulated in its own buffer among the plurality of gap periods. The switching timing of the optical switch is set so that the optical switch switches the communication path in any gap period after receiving the notification that the signal transmission is completed.

  More preferably, in the step of setting the switching timing and the transmission timing, the control unit sets a discovery period in which a new home device that desires communication with the station side device transmits an uplink communication signal to the station side device as a gap period. Set as.

  More preferably, in the step of setting the switching timing and the transmission timing, the control unit includes a plurality of homes provided during each period in which the plurality of home-side devices exclusively transmit uplink communication signals to the station-side device. A period in which the side apparatus does not transmit an uplink communication signal to the station side apparatus is set as a gap period.

  In order to solve the above problems, a maintenance management method according to an aspect of the present invention is a maintenance management method in a station side apparatus for executing the communication control method, and the backup optical line unit performs maintenance management. A standby optical line unit is a switching-destination optical line unit, an optical line unit other than the standby optical line unit is a switching-source optical line unit, and a standby optical line unit is a downlink communication signal After starting the output to the optical switch, a step of performing maintenance management by the maintenance management unit is included.

  In order to solve the above-described problems, a station apparatus according to an aspect of the present invention includes a plurality of standby optical line units and communicates with a plurality of home apparatuses via a plurality of passive optical networks. , An optical switch for switching communication paths between a plurality of passive optical networks and a plurality of optical line units, and control for controlling switching of the optical switch and transmission of uplink communication signals by a plurality of home-side devices Each optical line unit transmits a downlink communication signal to a plurality of home-side devices via an optical switch, and receives uplink communication signals from the plurality of home-side devices via an optical switch. From the communication path that outputs the downstream communication signal received from the switching source optical line unit to the passive optical network, the downstream communication signal received from the switching destination optical line unit is passively transmitted. Switching timing of the optical switch and a plurality of optical switches so that the optical switch does not receive uplink communication signals from a plurality of home-side devices during a switching transition period from the start to the completion of switching of the optical switch to the communication path to be output to the network The transmission timing of the home device is controlled.

  According to still another aspect of the present invention, a station-side apparatus includes one or a plurality of spare optical line units, and a plurality of optical line units that communicate with a plurality of home-side apparatuses via a plurality of passive optical networks. An optical switch that switches communication paths between a plurality of passive optical networks and a plurality of optical line units, and a control unit that controls transmission of uplink communication signals by a plurality of home-side devices, and each optical line The unit transmits the downlink communication signal to the plurality of home side devices via the optical switch, and receives the uplink communication signal from the plurality of home side devices via the optical switch, and the control unit receives from the switching source optical line unit. Communication that outputs the downlink communication signal received from the switching optical line unit to the passive optical network from the communication path that outputs the received downlink communication signal to the passive optical network The switching timing of the optical switch and the timing of the plurality of home devices so that the optical switch does not receive the uplink communication signal from the plurality of home devices during the switching transition period from the start to the completion of switching of the optical switch to the road Control transmission timing.

  Preferably, the backup optical line unit includes a memory for storing a program to be executed by the home side device, and a maintenance management unit for downloading the program stored in the memory to the home side device.

  According to the above, in a communication system having a redundant configuration, it is possible to prevent a momentary communication interruption when performing redundant switching.

It is a block diagram which shows schematic structure of the station side apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows the structural example of the optical switch 11a. It is a block diagram which shows the structural example of OSU. It is a block diagram which shows the structural example of the concentrating part 13a. 3 is a block diagram illustrating a configuration example of a control unit 14. FIG. 4 is a flowchart for explaining a procedure of initialization processing by a control unit 14; 4 is a flowchart for explaining a procedure of an interrupt processing routine by a control unit 14; It is a flowchart for demonstrating the detail of the discovery process (S26) shown in FIG. It is a flowchart for demonstrating the detail of RP timeout process (S27) shown in FIG. It is a flowchart for demonstrating the detail of the management communication master process (S28) shown in FIG. It is a flowchart for demonstrating the detail of the management communication slave process (S31) shown in FIG. 12 is a flowchart for explaining details of a scheduled confirmation process (S72) shown in FIG. It is a flowchart for demonstrating the detail of the control system switching (on) process (S32) shown in FIG. It is a flowchart for demonstrating the detail of the message reception process (S23) shown in FIG. 15 is a flowchart for explaining details of a register request process (S103) shown in FIG. 15 is a flowchart for explaining details of a register confirmation process (S104) shown in FIG. It is a flowchart for demonstrating the detail of the deregister process (S105) shown in FIG. It is a flowchart for demonstrating the detail of the report reception process (S106) shown in FIG. It is a flowchart for demonstrating the detail of a RTT update process. 15 is a flowchart for explaining details of OAM message processing (S108) shown in FIG. 14; 15 is a flowchart for explaining details of OSU management message processing (S109) shown in FIG. 14; It is a flowchart for demonstrating the detail of the OAM process (S24) shown in FIG. It is a flowchart for demonstrating the detail of the operation IF process (S25) shown in FIG. It is a figure which shows schematic structure regarding the uninterruptible switching operation in the station side apparatus which concerns on the 1st Embodiment of this invention. It is a figure which shows schematic structure regarding transmission of the downlink control frame in the station side apparatus which concerns on the 1st Embodiment of this invention. It is a flowchart for demonstrating the detail of the OSU switching process (S221) shown in FIG. It is a flowchart for demonstrating the detail of the band allocation process (S107) shown in FIG. It is a figure which shows the timing relationship of the uninterruptible switching operation in the station side apparatus which concerns on the 1st Embodiment of this invention. 24 is a flowchart for explaining details of a control system switching (off) process (S223) shown in FIG. It is a flowchart for demonstrating the detail of the OSU switching process (S221) shown in FIG. It is a flowchart for demonstrating the detail of the band allocation process in the station side apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the timing relationship of the uninterruptible switching operation in the station side apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart for demonstrating the detail of the modification of the band allocation process in the station side apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart for demonstrating the detail of the discovery process in the station side apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structural example of the spare system OSU in the station side apparatus which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows schematic structure of the station side apparatus in the 4th Embodiment of this invention. It is a figure which shows the structural example of the optical switch 11b in the 4th Embodiment of this invention. It is a block diagram which shows schematic structure of the station side apparatus in the 5th Embodiment of this invention. It is a block diagram which shows schematic structure of the optical switch part in the 5th Embodiment of this invention. It is a figure which shows schematic structure regarding the uninterruptible switching operation in the station side apparatus which concerns on the 5th Embodiment of this invention. It is a flowchart for demonstrating the detail of the switching process in the station side apparatus which concerns on the 5th Embodiment of this invention. It is a flowchart for demonstrating the detail of the instantaneous switching process (S304) shown in FIG. 42 is a flowchart for explaining details of a PON line switching process (S306) shown in FIG. 42 is a flowchart for explaining details of a PON line switching process (S306) shown in FIG.

  Hereinafter, the details of the embodiment of the present invention will be described. As a premise common to the embodiments, the PON is an Ethernet (registered trademark) -based PON (EPON), and is based on an MPCP frame defined in IEEE 802.3ah. It is assumed that ONU registration, withdrawal, bandwidth allocation to the ONU, bandwidth request from the ONU, and the like are performed.

<First Embodiment>
FIG. 1 is a block diagram showing a schematic configuration of a station-side apparatus according to the first embodiment of the present invention.

  Referring to FIG. 1, a PON system 301 includes a station-side device 1a, N PON lines 1 to N (3-1 to 3-N), which are optical fibers, and N optical couplers 4-1 to 4-1. 4-N and a plurality of home-side devices (ONUs) 2 are provided. The station side device 1a includes an optical switch 11a, OSU1 to N + 1 (12-1 to 12-N + 1), a concentrator 13a, and a control unit 14 that performs overall control of the station side device 1a. N is an integer of 2 or more.

  The station side device 1a is connected to N PON lines 1 to N, and terminates the N PON lines. The PON lines 1 to N are connected to the optical couplers 4-1 to 4-N, respectively, and are connected to a plurality of ONUs 2 through these optical couplers.

  The station side device 1a has a redundant configuration of N: 1. That is, out of N + 1 OSUs 12, OSU1 to N are active (active) OSUs, and OSU N + 1 is a standby (standby) OSU. The station side device 1a may include two or more standby OSUs.

  The optical switch 11a is connected between the N + 1 OSU1 to N + 1 (12-1 to 12-N + 1) and the N PON lines 1 to N (3-1 to 3-N) according to an instruction from the control unit 14. Switch the communication path.

  The concentrator 13a multiplexes the uplink frames from OSU1 to N + 1 (12-1 to 12-N + 1) and transmits them to the upper network (hereinafter also referred to as uplink), and appropriately receives the downlink frames received from the uplink. The process of distributing to the appropriate OSU is performed.

  FIG. 2 is a diagram illustrating a configuration example of the optical switch 11a. In the optical switch 11a, N optical fibers on the PON side and N optical fibers on the OSU side are arranged to face each other. Hereinafter, these N sets of optical fibers are also referred to as operational optical fibers.

  Collimating lenses 23-1 to 23-N are arranged near the end face of each optical fiber on the OSU side, and collimating lenses 24-1 to 24-N are arranged near the end face of each optical fiber on the PON line side. In the state, optical space transmission is performed between the optical fibers facing each other. N optical axes of the N sets of operational optical fibers are arranged to be parallel on the same plane.

  The movable mirror 22 is driven by the actuator 21 and moves on an axis orthogonal to the optical axes of the N optical fibers 3-1 to 3-N. The movable mirror 22 is located at any of the intersections of the N optical axes of the operational optical fiber and the moving axis of the movable mirror 22 and in the vicinity of the end face of the standby optical fiber. The actuator 21 moves the movable mirror 22 to one of the (N + 1) positions according to a control signal from the control unit 14. The control signal from the control unit 14 indicates the presence / absence of OSU redundancy switching and the number of the PON line connected to the standby OSU, and the actuator 21 moves the movable mirror 22 based on this control signal.

  The movable mirror 22 is inclined by 45 ° with respect to the optical axis of the operational optical fiber, and reflects the light beam from the optical fiber on the PON line side in the moving axis direction of the movable mirror 22. The light beam reflected by the movable mirror 22 enters the standby optical fiber 3-N + 1 via the collimator lens 23-N + 1.

  Further, since the light beam from the standby optical fiber 3-N + 1 is reflected by the movable mirror 22 and is incident on the optical fiber on the PON line side corresponding to the position of the movable mirror 22, the PON line corresponding to the position of the movable mirror 22. Optical space transmission can be performed between the side optical fiber and the standby optical fiber 3-N + 1.

  Here, when the movable mirror 22 is moved, the facing light is moved by temporarily moving the movable mirror 22 in the z direction (the direction from the front to the back in FIG. 2) and then moving in the x direction. The optical space transmission between the optical fiber pairs that are irrelevant to the switching among the fiber pairs is not affected.

FIG. 3 is a block diagram illustrating a configuration example of the OSU. The OSU 12 includes a concentrator IF (Interface) unit 31, a control IF unit 32, a reception processing unit 33, a transmission processing unit 34, a PON transmission / reception unit 35, a local control unit 36, and a FIFO 1 (37 ) And FIFO2 (38) for accumulating downstream frames.

  3 to 5, the configurations of the OSU, the concentrator, and the controller are described so as to include duplication described in a fourth embodiment described later. In the station-side device according to the first embodiment of the present invention, the concentrating IF unit 31 and the control IF unit 32 are not duplicated and are connected to one concentrating unit 13a and the control unit 14, respectively. The same applies to FIGS. 4 and 5. The PON transceiver unit 35 is connected to the optical switch 11a.

  The PON transmission / reception unit 35 is connected to the optical switch 11a by a single optical fiber, receives an upstream optical signal of a specific wavelength, for example, a 1310 nm band so that bidirectional communication can be performed on the optical fiber, and transmits an electrical signal. To the reception processing unit 33, and the electrical signal output from the transmission processing unit 34 is converted into a downstream optical signal of another wavelength, for example, 1490 nm band and transmitted.

  The reception processing unit 33 reconstructs a frame from the electrical signal received from the PON transmission / reception unit 35 and distributes the frame to the control IF unit 32, the local control unit 36, or the FIFO 1 (37) according to the type of the frame. Specifically, the user frame is output to the FIFO 1 (37), a special control frame such as a loopback test is output to the local control unit 36, and other general control frames are output to the control IF unit 32.

  The reception processing unit 33 receives grant information indicating when to receive a frame from which logical link from the transmission processing unit 34, and filters a received frame that is not indicated in the grant information, that is, discards the received frame. Also good. Further, the time stamp at the time of reception may be overwritten on the MPCP frame and output.

  The concentration IF unit 31 sends the upstream frame stored in the FIFO 1 (37) to the concentration unit 13a and stores the downstream frame received from the concentration unit 13a in the FIFO 2 (38). At this time, the concentrating IF unit 31 performs conversion between the signal format of the concentrating unit 13a and the internal signal format.

  When the FIFO 2 (38), the control IF unit 32, or the local control unit 36 has a frame / message to be transmitted, the transmission processing unit 34 receives the frame / message according to the priority order, assembles the frame, and sends it to the PON transmission / reception unit 35. Output. At this time, the time stamp at the time of transmission may be overwritten on the MPCP frame and output. In addition, the transmission processing unit 34 outputs the grant information described in the gate message from the control IF unit 32 to the reception processing unit 33.

  The control IF unit 32 outputs the control message received from the reception processing unit 33 to the control unit 14 and outputs the control message received from the control unit 14 to the transmission processing unit 34. At this time, the control IF unit 32 performs conversion between the signal format of the control unit 14 and the internal signal format.

  As a general rule, the control unit 14 terminates the control protocol for managing and operating the PON. However, in order to reduce the processing load on the control unit 14, the local control unit 36 terminates a specific protocol. In the present embodiment, the local control unit 36 performs a loopback test for an ONU that is a kind of OAM in accordance with an instruction from the control unit 14. That is, the local control unit 36 sets the loopback test mode, generates a loopback test frame, inspects the frame returned by the loopback, notifies the result, and cancels the loopback mode.

  The transmission processing unit 34 collects statistical information such as the number of transmission frames and notifies the control unit 14 via the control IF unit 32.

  Similarly, the reception processing unit 33 collects statistical information such as the number of received frames and the number of received signal code errors and notifies the control unit 14 via the control IF unit 32. This statistical information is used when determining switching of the system in a configuration in which the OSU is made redundant. For example, when the number of code errors in the received signal is large, control such as switching to a standby OSU is performed.

  Further, the PON transmission / reception unit 35 monitors its own transmission light level. When the transmission light level is out of the specified range due to a failure or aged deterioration of the light emitting element, the control unit 14 via the control IF unit 32. Notify the alarm.

  FIG. 4 is a block diagram illustrating a configuration example of the concentrator 13a. The line concentrator 13a includes an uplink transmitter / receiver 41, a downlink distributor 42, a line concentrator 43, a control IF 44, an OSU IF 1 to N + 1 (45-1 to 45-N + 1), and a filter. 1 to N + 1 (46a-1 to 46a-N + 1), FIFOs 47-1 to 47-N + 1, and a selector 48.

  The OSU IF unit i (i = 1 to N + 1) converts the upstream frame sent from the corresponding OSUi into an internal signal format, and temporarily buffers each of the FIFOs 47-1 to 47-N + 1 via the filter unit i. To do.

  The line concentrator 43 manages the state of the FIFOs 47-1 to 47-N + 1, determines the output order to the uplink for the non-empty FIFO, and transfers the upstream frame from the FIFO to the uplink transceiver 41. Instruct. At this time, the line concentrator 43 controls the selector 48 and performs setting so that the uplink frame output from the FIFO reaches the uplink transceiver 41 via the selector 48.

  The uplink transmission / reception unit 41 transmits the uplink frame output from the selector 48 to the uplink, and outputs the downlink frame received from the uplink to the downlink distribution unit 42.

  The downlink distribution unit 42 copies the downlink frame received from the uplink transmission / reception unit 41 and outputs it to the filter units 1 to N + 1 (46a-1 to 46a-N + 1).

  The filter unit i (i = 1 to N + 1) refers to VLAN (Virtual LAN) header information stored in the downstream frame, and determines which PON line i the frame is to be transmitted to. The filter unit i filters downstream frames that should not be transmitted, performs necessary processing such as header conversion on the downstream frames to be transmitted, and outputs the result to the OSU IF unit i. Further, the filter unit i connects or disconnects the uplink path and the downlink path based on information regarding the redundant configuration of the control unit 14.

  The filter unit N + 1 (46a-N + 1) corresponding to OSU N + 1 may hold the settings of all other filter units and select and apply the setting corresponding to the switched line. Here, the setting of the filter unit means connection / disconnection of the entire path according to VLAN information, information used for filtering a downstream frame such as a special reserved MAC address for each frame, and a redundant configuration. Information used for such purposes.

  The control IF unit 44 communicates with the control unit 14 to perform setting and status notification of each unit of the concentrator 13a, alarm transfer, and the like.

  Further, the uplink transmission / reception unit 41 collects statistical information such as the number of transmission frames, the number of received frames, and the number of code errors in the received signal, and sends these statistical information to the control IF unit 44 according to an inquiry from the control unit 14. Is output to the control unit 14. In addition, the uplink transmission / reception unit 41 detects link establishment / disconnection at the physical layer level with the opposite device in the uplink, and detects transmission abnormality by monitoring its own output signal. When the uplink transmission / reception unit 41 detects uplink disconnection or transmission abnormality, the uplink transmission / reception unit 41 notifies the control unit 14 of a corresponding alarm via the control IF unit 44.

FIG. 5 is a block diagram illustrating a configuration example of the control unit 14. The control unit 14 includes a CPU (Central Processing Unit) 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, an IO (Input Output) control unit 54, an OSU IF unit 55,
A shared RAM 56 and a clock / timer 57 are included.

  The OSU IF unit 55 is connected to the OSUs 1 to N + 1 (12-1 to 12-N + 1), and is transmitted / received to / from the ONU, and the OSU for managing and controlling the OSU. Send and receive information via message communication. These messages are transmitted / received to / from the CPU 51 via the input message queue and the output message queue included in the shared RAM 56.

  In response to a command from the CPU 51, the IO control unit 54 performs setting and status management of the concentrator 13a and the optical switch 11a, and also provides an operator with an operation interface (hereinafter also referred to as an operation IF) of the station side device 1a. )I will provide a. In addition, when receiving an event such as a response and an alarm from the operation IF, the concentrator 13a and the optical switch 11a, the IO controller 54 notifies the CPU 51 as an interrupt.

  The clock / timer 57 manages a clock and various timers for managing the PON, and outputs a time and timer end interrupt to the CPU 51.

  The ROM 52 stores a program for controlling the entire control unit 14 and fixed data. The RAM 53 is used as a work area for temporarily storing data.

  The CPU 51 reads and executes a program from the ROM 52, and reads out fixed data stored in the ROM 52 and reads / writes data to / from the RAM 53 to execute processing described later.

  The reference clock for driving the PON clock is also given to each OSU, and the PON clock of each OSU is synchronized with the periodic time notification by management communication.

  The processing in the control unit 14 is basically the same as the well-known processing in the local control unit in the OSU. However, a single CPU and a program control all the PONs while quickly switching / switching back redundant OSUs. In order to implement, the concept of virtual OSU and OSU conversion is introduced. Note that switching back refers to returning to the state before redundant switching after performing redundant switching.

  The OSU that normally interfaces with the CPU 51 executing the program is a virtual OSU. That is, the virtual OSU is interfaced with the real OSU by performing OSU conversion. For example, when switching the end of the PON line i from OSUi to OSU N + 1, the OSU conversion is changed from (virtual OSUi⇔real OSUi) to (virtual OSUi⇔real OSU N + 1). As a result, the virtual OSUi can be made to correspond to the PON line i regardless of the redundant switching / switchback state of the OSU.

  Such implementation of OSU conversion may be software processing by the CPU 51, but in this embodiment, hardware processing by the OSU IF unit 55 is used as described later. However, regarding OSU control information for managing and controlling the OSU, the CPU 51 can execute a program and directly specify the real OSU to perform message communication.

  FIG. 6 is a flowchart for explaining the procedure of the initialization process by the control unit 14. This initialization process performs necessary initial settings for each part of the station side apparatus 1a. Here, a logical link table LLT and a final allocation time TE are provided for each virtual OSU. Each element of the logical link table LLT stores information unique to the logical link. Specifically, the logical link table LLT includes a logical link state LLstat, report information RPinfo, a latest report reception time RPtime, a round trip propagation time RTT, and an OAM link connectivity confirmation frame latest reception time OAMt.

  First, the input message queue Qin and the output message queue Qeg are emptied, the logical link tables LLTij (i = 1, 2,..., N: j∈ {LLID of OSU i}) are all NULL, and the final allocation time TEi is all The current time is ctime, and the OSU conversion setting is OSUmap (i) = i (i = 1, 2,..., N) (S11).

  Next, by performing management communication with another system control unit (S12), it is determined whether the control unit is duplexed or a standby system control unit (S13). Although the control unit is not duplexed in the present embodiment, the control unit according to the first embodiment of the present invention is also described in order to explain the duplexing of the control unit described in the fourth embodiment together. Such a procedure is included in the flowchart showing the operation procedure of the station side apparatus. Therefore, in the present embodiment, operational processing is always performed.

  If the control unit is duplicated and the control unit is a standby system (S13, Yes), the management information of the active control unit is copied, and the current time ctime is set as the active system ctime. Match to the operational system (S14). Then, the management communication timer (TMC) is set (S15), and the process ends.

  If the control unit is not duplexed or the control unit is an active system (S13, No), the configuration definition information is taken in via the operation IF and the optical switch 11a is set to the normal state. Then, based on the transfer rule included in the configuration definition information, for example, information indicating the correspondence between the VLAN ID and the PON line in the upper network via the uplink, the setting of each filter unit in the concentrator 13a is performed (S16). ).

  Finally, the discovery timer (TD) is set, the management communication timer (TMC) is set (S17), and the process ends.

  FIG. 7 is a flowchart for explaining the procedure of the interrupt processing routine by the control unit 14. Since most of the processes in the control unit 14 occur irregularly, interrupts are used, and priority is given to each interrupt process. In the processes of steps S23 to S28, the process of S23 has the highest priority, and the process of S28 has the lowest priority. Further, in the processes of steps S30 to S32, the process of S30 has the highest priority, and the process of S32 has the lowest priority.

  First, when an interrupt occurs, it is determined whether or not the control unit 14 is an active system (S21). If the control unit 14 is an active system (S21, Yes), the process branches depending on the interrupt type (S22). If the interrupt type indicates that there is a message in the input message queue (S22, Qin is not empty), a message reception process is performed (S23), and the process is terminated.

  If the interrupt type is the expiration of the OAM process activation timer TOAMij (S22, TOAMij has expired), the OAM process is performed (S24) and the process is terminated. If the interrupt type is an interrupt from the operation IF (S22, operation IF), the operation IF process is performed (S25), and the process ends.

  If the interrupt type is the expiration of the discovery timer (TD) (S22, TD expiration), the discovery process is performed (S26), and the process is terminated. If the interrupt type is the expiration of the timer TLij (S22, TLij expiration), a report (RP) timeout process is performed (S27), and the process is terminated. If the interrupt type is the expiration of the management communication timer TMC (S22, TMC expiration), the management communication master process is performed (S28), and the process is terminated.

  In step S21, if the control unit 14 is a standby system (S21, No), the process branches depending on the interrupt type (S29). If the interrupt type indicates that there is a message in the input message queue (S29, Qin non-empty), a message reception process is performed (S30), and the process ends.

  If the interrupt type is management communication (S29, management communication), a management communication slave process is performed (S31), and the process ends. If the interrupt type is the expiration of the management communication timer TMC (S29, TMC is expired), the control system switching (ON) process is performed (S32), and the process is terminated.

  FIG. 8 is a flowchart for explaining details of the discovery process (S26) shown in FIG. This discovery process may not be performed if all the contracted logical links are in the registered state, and if all the logical links contracted for a certain PON are in the registered state, steps S41 and S42 are performed. The transmission of the discovery gate message for the PON (virtual OSU) may be skipped.

  First, discovery gate messages for OSUk (k = 1, 2,..., N) are sequentially created and placed in the output message queue Qeg. At this time, the start time is based on TEk or the later of the current time (S41). Then, the end of the discovery period is set as a new TEk (S42). That is, the arrangement of the discovery window is determined based on the immediately preceding TEk or the later of the current time and taking into account the assumed RTT range, the congestion status of register requests, and the like.

  Finally, the discovery timer TD is set (S43), and the process ends. The value set in the discovery timer TD is discovery_interval which is a predetermined period. That is, discovery gate messages for OSUs are sequentially issued at a predetermined cycle.

  FIG. 9 is a flowchart for explaining details of the RP timeout process (S27) shown in FIG. This RP timeout process is a process when no report message is received during the reception window period due to the expiration of the timer TLij.

  First, it is determined whether or not the logical link is being registered by referring to LLstat of LLTij (S51). If the logical link is not registered (S51, No), a value obtained by subtracting the latest report reception time RPtime from the current time ctime is substituted into RPlossT (S52). This RPlossT is the elapsed time from the latest report reception time.

  If RPlossT is greater than 1 second (S53, Yes), the process proceeds to step S56. If RPlossT is 1 second or less (S53, No), in order to receive the report message from the logical link j again, a gate message for LIDj of OSUi is created and placed in the output message queue Qeg. At this time, a report forced flag is set. A reception window is assigned with the start time as a reference based on TEi or the current time, and the grant length as an amount capable of transmitting only a report frame (S54).

  Then, the start of laser off of the grant is set as a new TEi, a timer TLij is set at a time when a certain amount of blur time is anticipated (S55), and the process is terminated.

  If the logical link is being registered in step S51 (S51, Yes), a deregistering process described later is performed (S56), the standby control unit is notified of the deregistering of LLIDij (S57), and the process is terminated. .

  FIG. 10 is a flowchart for explaining details of the management communication master process (S28) shown in FIG. First, the current time ctime is notified to the control unit of the other system (standby system) to notify that the active system is normal, the status is inquired to the control unit of the standby system, the presence / absence of the duplex system and the other system The normal / abnormal of (standby system) is recorded (S61).

  Next, it notifies the optical switch 11a and the concentrator 13a that the operation control unit is normal, inquires about the states of the optical switch 11a and the concentrator 13a, and records them (S62). Finally, the management communication timer (TMC) is set (S63), and the process ends.

  FIG. 11 is a flowchart for explaining details of the management communication slave process (S31) shown in FIG. It is determined whether the process is a scheduled confirmation process or an individual process (S71). If it is a regular confirmation process (S71, regular confirmation), a regular confirmation process is performed (S72), and the process is terminated. This scheduled confirmation process responds to the standby system status inquiry shown in step S61 of the management communication master process of FIG.

  If the process is an individual process (S71, individual process), the individual process is performed (S73), and the process is terminated. This individual process includes a management communication process for synchronizing the state of the standby system with the active system and a system switching instruction. Details of these processes will be described later.

  FIG. 12 is a flowchart for explaining the details of the regular confirmation process (S72) shown in FIG. First, the current time ctime of the active system received from the active control unit is set to the current time ctime of the standby system so that the clock is set to the active system and an inquiry from the active system control unit is answered (S81).

  Finally, it notifies the optical switch 11a and the concentrator 13a that the standby control unit is normal, inquires about the status of the optical switch 11a and the concentrator 13a, records it (S82), and manages communication. A timer (TMC) is set (S83), and the process ends.

  FIG. 13 is a flowchart for explaining details of the control system switching (on) processing (S32) shown in FIG.

  In the control system switching (on) process, the operation system is shifted to (S95), the discovery timer (TD) is set, and the management communication timer (TMC) is set (S96).

  Then, LLTij (i = 1, 2,..., N: jε {LLUID of OSUi}) is examined in order, and if LLstat is already registered, the timer TLij is set. Further, if OAMt is not NULL, the OAM process activation timer TOAMij is set (S97), and the process is terminated.

  At this time, the value set in the timer TLij is obtained by adding the upper limit value of the bandwidth allocation period to the current time ctime, and the value set in the OAM process activation timer TOAMij is obtained by adding OAM maxinterval (described later) to the current time ctime. .

  FIG. 14 is a flowchart for explaining details of the message reception process (S23) shown in FIG. First, the head message is taken out from the input message queue Qin (S101), and branched depending on the message type (S102).

  If the message type is a register request message (S102, register request), register request processing is performed (S103), and the process proceeds to step S110. If the message type is a register confirmation message (S102, register confirmation), register confirmation processing is performed (S104), and the process proceeds to step S110.

  If the message type is a deregister request message (S102, deregister request), deregister processing is performed (S105), and the process proceeds to step S110. If the message type is a report message (S102, report), a report reception process is performed (S106), a bandwidth allocation process is performed (S107), and the process proceeds to step S110.

  If the message type is an OAM message (S102, OAM), OAM message processing is performed (S108), and the process proceeds to step S110. If the message type is an OSU management message (S102, OSU management), OSU management message processing is performed (S109), and the process proceeds to step S110.

  In step S110, it is determined whether or not the input message queue Qin is empty. If the input message queue is not empty (S110, No), the process returns to step S101, the next message is extracted, and the subsequent processing is performed. If the input message queue Qin is empty (S110, Yes), the process ends.

  FIG. 15 is a flowchart for explaining the details of the register request process (S103) shown in FIG. When a register request message is received from the home side device with OSUi and MAC address m, it is first determined whether or not the transmission source ONU is valid (S111).

  If the transmission source ONU is valid (S111, Yes), a new LLIDj is assigned to OSUi. Then, the logical link state LLstat is set during registration for LLTij, the report information RPinfo is set to NULL, and (T2-T1) is set as the round trip propagation time RTT (S112). Here, T1 is a time stamp recorded in the message by the home side device, and T2 is a time stamp added by OSUi at the time of reception.

  Next, it is determined whether or not the control unit is an active system (S113). If the control unit is a standby system (S113, No), the process is terminated as it is.

  If the control unit is an active system (S113, Yes), a register message (w / Ack) for OSUi is created and placed in the output message queue Qeg (S114). At this time, the transmission destination address DA of the register message is set to m, and the LLID is set to j. Note that (w / Ack) indicates a register message to which Ack is added.

  Next, a gate message for LLIDj of OSUi is created and placed in the output message queue Qeg. At this time, the start time is based on TEi or the current time, and the grant window is assigned a reception window as an amount that can transmit only the register confirmation frame (S115).

  It should be noted that the arrangement of the reception window takes into account accuracy errors and, of course, does not overlap the reception window of other logical links even if the laser on / off overlap is allowed. The RTT and ONU processing times are arranged ahead of the scheduled transmission time.

  Then, the start of laser off of the grant is set as a new TEi, and a time when a certain amount of blur time is expected is set in the timer TLij (S116), and the process is terminated.

  In step S111, if the ONU is not valid (S111, No) and the control unit is the active system (S118, Yes), a register message (w / Nack) for OSUi is created and placed in the output message queue. At this time, the transmission destination address of the register message is set to m (S117), and the process ends. On the other hand, if the control unit is a standby system (S118, No), the process is terminated as it is.

  FIG. 16 is a flowchart for explaining details of the register confirmation processing (S104) shown in FIG. Assume that a register confirmation message is received from LLIDj of OSUi. First, an RTT update process, which will be described later, is performed, and it is determined whether or not the RTT update process has ended normally (S121). If the RTT update process does not end normally (S121, NG), the process ends.

  If the RTT update process ends normally (S121, OK), the logical link state LLstat is set to registered for LLTij, and the current time ctime is set to the latest report reception time RPtime (S122). Then, it is determined whether or not the control unit is an active system (S123). If the control unit is a standby system (S123, No), the process is terminated as it is.

  If the control unit is an active system (S123, Yes), a gate message for LLIDj of OSUi is created and placed in the output message queue Qeg. At this time, a report forced flag is set. The start time is based on TEi or the current time, and the grant length is assigned as a reception window so that only the report frame can be transmitted (S124).

  Then, the start of laser off of the grant is set as a new TEi, a time when a certain blur time is expected is set in the timer TLij (S125), the OAM process activation timer TOAMij is set (S126), and the process is terminated.

  FIG. 17 is a flowchart for explaining details of the deregister processing (S105) shown in FIG. This process deregisters LLIDj of OSUi. First, the logical link state LLstat is set to NULL for LLTij, and the logical link j is released (S131). Next, if the control unit is an active system (S132, Yes), a deregister message for LLIDj of OSUi is created and placed in the output message queue Qeg, and the process ends (S133). On the other hand, if the control unit is a standby system (S132, No), the process is terminated as it is.

  FIG. 18 is a flowchart for explaining details of the report reception process (S106) shown in FIG. In this process, a report is received from LLIDj of OSUi. First, for the LLTij, the latest report reception time RPtime is set to the current time ctime (S141), RTT update processing described later is performed, and it is determined whether the RTT update processing has ended normally (S142).

  If the RTT update process ends normally (S142, OK), the total of the ONU upstream queue length queueK_report included in the report information extracted from the input message queue Qin is substituted into the report information RPinfo for LLTij (S143). ), The process is terminated.

  If the RTT update process does not end normally (S142, NG), the process ends.

  FIG. 19 is a flowchart for explaining details of the RTT update processing. First, a value obtained by subtracting the time stamp T1 recorded in the message by the home side device from the time stamp T2 added by the OSUi at the time of reception is set as a new RTT (newRTT) (S151). Then, it is determined whether the absolute value of the difference between newRTT and RTT exceeds the allowable drift value DRIFTmax (S152).

  If it is equal to or less than the allowable drift value DRIFTmax (S152, No), the RTT is set to newRTT with respect to LLTij (S153), and the process is terminated assuming that the RTT update process has ended normally. If the allowable drift value DRIFTmax is exceeded (S152, Yes), it is determined whether or not the control unit is an active system (S154).

  If the control unit is an active system (S154, Yes), the deregistration process shown in FIG. 17 is performed (S155), the deregistration of LLIDij is notified to the standby control unit (S156), and the RTT update process ends normally. If not, the process ends. If the control unit is a standby system (S154, No), it is assumed that the RTT update process has not ended normally, and the process ends.

  In the OSU switching process (S221) and the OSU switchback process (S222), when the transition period necessary for switching the path can be referred to and the reception time of the control frame corresponds to the transition period, the drift is performed in S152. The allowable value may be increased by taking into account fluctuations associated with path switching, or the comparison may be ignored (S152 is always No).

  FIG. 20 is a flowchart for explaining details of the OAM message processing (S108) shown in FIG. Assume that an OAM message is received from LLIDj of OSUi. First, when the OAM message is an OAM link connectivity confirmation message, OAMt is set to the current time ctime for LLTij (S171), and it is determined whether or not the control unit is an active system (S172).

  If the control unit is not the active system (S172, No), the process is terminated as it is. If the control unit is an active system (S172, Yes), processing according to the content of the OAM message is performed (S173), and the processing is terminated.

  FIG. 21 is a flowchart for explaining the details of the OSU management message processing (S109) shown in FIG. Assume that an OSU management message is received from OSUi. First, it is determined whether or not the control unit is an active system (S211). If the control unit is a standby system (S211, No), the process is terminated as it is.

  If the control unit is an active system (S211, Yes), it is determined whether a failure notification has been received (S212). If there is a failure notification (S212, Yes), an OSU switching process described later is performed (S213), and the process is terminated. If there is no failure notification (S212, No), processing according to the message content is performed (S214), and the processing is terminated.

  FIG. 22 is a flowchart for explaining details of the OAM processing (S24) shown in FIG. This OAM process is performed independently for each virtual OSU (denoted i) and logical link (denoted j), and ONU setting and status confirmation are performed by OAM communication with the corresponding ONU.

  First, it is determined whether or not OAMt of LLTij is NULL (S191). If the OAMt of LLTij is NULL (S191, Yes), this indicates that the OAM link is in the initial state, so an OAM loopback test is performed (S192), and it is determined whether or not it is successful (S193).

  If the OAM loopback test is successful (S193, Yes), the ONU corresponding to PONi and LLIDj is initialized (S194), and the OSUi is allowed to communicate between the PON side and the uplink side of LLIDj (S195). . Then, an OAM link connectivity confirmation message is transmitted, and LLIDij. OAMt = ctime is set (S204). Then, the OAM process activation timer TOAMij is set (S196), and the process ends.

  If the OAM loopback test is not successful (S193, No), deregister processing is performed (S197), the standby control unit is notified of LLIDij deregister (S198), and the processing is terminated.

  In step S191, if the OAMt of LLTij is not NULL (S191, No), it is determined whether or not the value obtained by subtracting the OAMt of LLTij from the current time ctime is smaller than OAMmaxinterval (S199). This OAM max interval is determined in advance, and this value determines whether or not the OAM communication is interrupted.

  If the value obtained by subtracting OLMt of LLTij from the current time ctime is smaller (S199, Yes), an OAM link connectivity confirmation message is sent to ONUi (S200), and an OAM process activation timer TOAMij is set (S201). ), The process is terminated.

  If the value obtained by subtracting OLTt of LLTij from the current time ctime is not smaller (No in S199), deregister processing is performed (S202), the deregistration of LLIDij is notified to the standby control unit (S203), End the process.

  FIG. 23 is a flowchart for explaining details of the operation IF process (S25) shown in FIG. If the instruction by the operation IF is an OSU switching instruction, an OSU switching process is performed (S221), and the process ends.

  If the instruction by the operation IF is an OSU switchback instruction, an OSU switchback process is performed (S222), and the process ends. If the instruction by the operation IF is a control system switching instruction, a control system switching process is performed (S223), and the process ends. If the instruction by the operation IF is other, the process according to the instruction is performed (S224), and the process is terminated.

  Next, the redundant switching operation performed by the station side apparatus according to the first embodiment of the present invention will be described.

  Redundant switching performed by the station side apparatus according to the first embodiment of the present invention is uninterrupted switching. Non-instantaneous switching refers to eliminating communication signal (frame) discarding at the time of redundant switching, or making communication signal discarding extremely limited and preserving the frame order of communication signals. Since uninterruptible switching has already caused communication signal discard at the time of failure, it is more redundant for OSU periodic maintenance and pre-planned OSU replacement work than when redundant switching is performed at the time of failure. It is more useful when switching.

  Therefore, it is more desirable that the station side apparatus 1a performs non-instantaneous switching according to the present embodiment at the time of maintenance of the OSU and performs conventional redundant switching that is not uninterrupted at the time of failure of the OSU as quickly as possible. Even when there is a failure, it is desirable to perform non-instantaneous switching when switching back after removing the failure. With such a configuration, appropriate redundancy switching can be performed according to the situation.

  FIG. 24 is a diagram illustrating a schematic configuration relating to a non-instantaneous switching operation in the station-side apparatus according to the first embodiment of the present invention. Here, a case where switching from OSUi (i = 1 to N + 1) to OSUj (j = 1 to N + 1, i ≠ j) will be described.

  Referring to FIG. 24, in the down direction, there is communication path switching by the down switch DSW and communication path switching by the optical switch 11a (OSW) in the concentrator 13a. An OSU downstream buffer, that is, a FIFO 2 is provided between the downstream switch DSW and the optical switch 11a.

  The station apparatus according to the first embodiment of the present invention performs redundant switching processing in the following order (1) to (4) in order to prevent downstream frame discard and overtaking. That is, (1) the down switch DSW is switched in the concentrator 13a. Subsequent downstream frames are stored in the FIFO 2 of OSUj. (2) Flush the FIFO2 of the OSUi, that is, complete transmission of the downstream frame stored in the FIFO2, and empty the FIFO2. (3) The optical switch 11a is switched. (4) Start transmission of a downstream frame by OSUj, that is, start transmission of a downstream frame stored in FIFO 2 of OSUj.

  In the PON line and the optical switch 11a, the downstream communication signal and the upstream communication signal are wavelength-multiplexed. Therefore, the optical switch 11a simultaneously switches the downstream communication path and the upstream communication path.

  Here, for the uplink direction, the control unit 14 sets a gap in the band allocation process described later so that the uplink frame from the ONU does not reach the station side device during the switching period of the redundancy switching process (3).

  FIG. 25 is a diagram illustrating a schematic configuration regarding transmission of a downlink control frame in the station-side apparatus according to the first embodiment of the present invention.

  Referring to FIG. 25, OSU IF unit 55 includes a transmission control unit 61, an OSU conversion unit 62, and an OSU distribution unit 63.

  In the shared RAM 56, control messages sent from the CPU 51 are queued for each virtual OSU. The OSU conversion unit 62 receives the control message from the shared RAM 56, converts the virtual OSU described in the control message into a real OSU, that is, converts the virtual OSU to the OSU, and sends it to the OSU distribution unit 63. Then, the OSU distribution unit 63 sends the control message received from the OSU conversion unit 62 to the real OSU.

  The transmission control unit 61 controls reading of control messages queued in the shared RAM. Further, the transmission control unit 61 sets the queue reading temporarily and sets and changes the OSU conversion according to an instruction from the CPU 51. These timings will be described later.

  FIG. 26 is a flowchart for explaining the details of the OSU switching process (S221) shown in FIG.

  Referring to FIG. 26, first, the control unit 14 stops transmission of the downlink frame of OSUj and clears FIFO2 of OSUj (S230).

  Next, the control unit 14 instructs the concentrator 13a to switch the down switch DSW from the OSUi side to the OSUj side. (S231).

  The contents of step S231 will be described in detail with reference to FIG. Before the switching of the down switch DSW, the path settings of the filter units i and j are “connected” and “disconnected”, respectively. In the switching process of the down switch DSW of the concentrator 13a, first, the setting of the filter unit j is made the same as the setting of the filter unit i. Then, the path settings of the filter units i and j are simultaneously changed to “disconnected” and “connected”, that is, each path setting is changed in the same inter-frame gap in the downstream frame sequence.

  Next, the control unit 14 predicts a time TF when the FIFO 2 of OSUi becomes empty. Further, the control unit 14 refers to the uplink burst allocation final time TEi calculated in the band allocation process shown in FIG. 27 described later. Then, the control unit 14 provides the optical switch OSW switching period P1 after max {TF, TEi, ctimeP}, that is, the later time of the time TF, the time TEi, and the time ctimeP. The control unit 14 associates the period P1 with the identifier i of the virtual OSU representing the switching target and shares it with the band allocation process, that is, enables the period P1 and the identifier i to be referred to in the band allocation process (S232). Here, the time ctimeP is a time obtained by adding a delay time due to the OSU switching process to the current time ctime. The optical switch OSW switching period is obtained by adding the ONU reception overhead time to the switching transition period from when the optical switch 11a starts switching the communication path to when it is completed. Here, the reception overhead time in the ONU is the sum of the time required for the optical receiver to become stable again and the resynchronization time of the data recovery circuit due to the instantaneous interruption of the optical signal in the ONU. In addition, the period P1 may be distinguished from the down direction and the up direction, and the up period P1 may be only the switching transition period of the optical switch 11a.

  Next, the control unit 14 instructs the OSU IF unit 55 to change the setting related to the virtual OSUi for OSU conversion from OSUmap (i) = i to OSUmap (i) = j in the period P1 (S233). That is, the destination OSU described in the downlink control message received from the output message queue Qeg is changed from OSUi to OSUj. Further, the OSU IF unit 55 temporarily stops taking out the control message from the output message queue Qeg corresponding to the virtual OSUi in the period P1. As a result, the communication path of the control frame is switched from via OSUi to OSUj after the period P1.

  Then, when the current time is the start time of the period P1, the control unit 14 instructs the optical switch 11a to switch from the OSUi side to the OSUj side (S234).

  Then, when the current time reaches the end time of the period P1, the control unit 14 instructs the OSUj to start transmission of the downlink frame. Further, the transmission control unit 61 resumes the output of the control message from the control unit 14, that is, the control frame to the OSU (S235).

  Next, the control unit 14 notifies the standby control unit of switching from OSUi to OSUj, and ends the process (S236).

  Note that in the uplink direction, the OSUi communication period and the OSUj communication period are exclusively assigned across the period P1, and therefore, according to the detailed description of FIG. 4, the OSUi uplink communication path and the OSUj uplink communication path In the concentrating part 13a, it merges simply.

  FIG. 27 is a flowchart for explaining details of the bandwidth allocation processing (S107) shown in FIG. This process assigns a bandwidth to LLIDj of OSUi. First, the time REPORT_length required for report frame transmission is added to LLTij report information RPinfo (ONU upstream queue length) to set Len, and the synchronization period Sync is added to the laser on period Ton to set the overhead time OVL. The smaller value of the sum of Len, OVL and laser off period Toff and the upper limit value GLmax of the grant length is defined as GL.

  Further, the sum of the last allocation time TEi of OSUi and the burst gap burst_gap is TSi, and the sum of the current time ctime, the RTT, and the processing time proc_time of the home side device is TSc. The latest time among TSi and TSc is set as TS (S162).

  Next, when the period from TS to TS + GL, that is, the period from the time TS to the lapse of GL overlaps with the optical switch OSW switching period P1 obtained in the OSU switching process (S221), the time TS is changed to the optical switch OSW switching period P1. Is changed to a later time (S163). Here, when the identifier associated with the switching period P1 is different from i, that is, different from the identifier corresponding to the OSU to be switched, the switching period P1 is not set.

  Next, a gate message for LLIDj of OSUi is created and placed in the output message queue Qeg. At this time, a report forced flag is set. The start time is a value obtained by subtracting RTT from TS, and a grant window is assigned as a grant length GL (S164).

  Then, a value obtained by subtracting Toff from a value obtained by adding GL to TS is set as a final allocation time TEi (S165), a timer TLij is set at a time at which a certain amount of fluctuation is expected in TEi (S166), and the process ends.

  In the Len calculation process, parity data for error correction may be added.

  Further, the bandwidth allocation process may be performed in cooperation with virtual OSUs concentrated on the same uplink. In particular, if the bandwidth allocation of each PON line is performed so that the uplink frame output from the virtual OSU can pass through without staying in the concentrator based on the uplink uplink bandwidth allocation, the FIFO of the concentrator The amount may be small, and the time for the user frame to pass through the station side device can be shortened.

  FIG. 28 is a diagram showing a timing relationship of the non-instantaneous switching operation in the station side apparatus according to the first embodiment of the present invention.

  Referring to FIG. 28, the transmission of the downlink user frame is stopped at time TF when FIFO 2 of OSUi becomes empty. Since the last arrival time TEi of the upstream burst from the ONU is later than the time TF, the optical switch OSW switching period P1 is provided after the time TEi (S232).

  The time TS is set so that the period from TS to TS + GL does not overlap with the period P1 (S163). Further, the transmission of the downlink frame is resumed after the period P1.

  In the station side apparatus according to the first embodiment of the present invention, there is no essential difference between the OSU switching process and the OSU switching back process. That is, the detailed contents of the OSU switch-back process are the same as those in which the relationship between OSUi and OSUj is exchanged in the flowchart shown in FIG. 26, and therefore detailed description will not be repeated here.

  FIG. 29 is a flowchart for explaining details of the control system switching (off) process (S223) shown in FIG. First, a system switching instruction is given to the control unit of the other system (standby system) (S251), and the process proceeds to the standby system (S252). Then, the management communication timer (TMC) is set (S253), and the process ends.

  Here, with the optical switch 11a according to the present embodiment, normal communication is possible on the communication path other than the switching target even in the switching period P1. However, if the communication of all the communication paths is allowed to become unstable in the switching period P1, the structure of the optical switch can be simplified and the economy can be achieved. Even when such an optical switch is used, instantaneous switching can be performed by changing the operation as follows.

  That is, in step S232 of the OSU switching process shown in FIG. 26, the setting of the switching period P1 is set to max {TF, TEk} (k = 1, 2,..., N), and the step of the bandwidth allocation process shown in FIG. In S163, the switching period P1 is valid regardless of whether the identifier is i, that is, whether the identifier corresponds to the OSU to be switched. Further, the OSU IF unit 55 temporarily stops taking out control messages from all the output message queues Qeg in the period P1, and instructs the OSUs 12-1 to N to temporarily stop downlink communication in the period P1. To do. Upon receiving the instruction, each OSU 12 temporarily stops reading and transmission of the FIFO2 (38) in the period P1.

  As described above, in the station side apparatus according to the first embodiment of the present invention, first, the switching source OSUi stops the output of the downlink communication signal to the optical switch 11a. Next, the optical switch 11a starts switching from the communication path that outputs the downlink communication signal received from the switching source OSUi to the PON line to the communication path that outputs the downlink communication signal received from the switching destination OSUj to the PON line. Then, the control unit 14 sets the switching timing of the optical switch 11a and the transmission timing of the plurality of ONUs so that the optical switch 11a does not receive the upstream communication signal from the plurality of ONUs during the switching transition period from the completion to the completion. Next, the optical switch 11a switches the communication path based on the set switching timing. Next, the switching destination OSUj starts outputting the downlink communication signal to the optical switch 11a.

  With such a configuration, it is possible to prevent the upstream communication signal from being discarded and to prevent the downstream communication signal from being discarded in the optical switch. Therefore, the station apparatus according to the first embodiment of the present invention can prevent instantaneous interruption of communication when performing redundant switching in a communication system having a redundant configuration.

  In the station apparatus according to the first embodiment of the present invention, before the optical switch 11a switches the communication path from OSUi to OSUj, the concentrator 13a switches the output destination of the downlink communication signal to the source OSUi. To switch to the destination OSUj. Then, the control unit 14 predicts the timing at which the switching source OSUi completes the transmission of the downlink communication signal accumulated in its own FIFO 2. The control unit 14 sets a gap period that is after the predicted timing and is longer than the switching transition period, and in which a plurality of ONUs stop transmission of the uplink communication signal, so that the switching transition period is included in the gap period. The switching timing of the switch 11a is set.

  That is, the redundancy switching method for the station side apparatus according to the first embodiment of the present invention is suitable when the flash time is short because the capacity of the FIFO 2 is small and the flash time can be predicted. For example, a time obtained by dividing the maximum capacity of the downstream buffer, that is, the FIFO 2 by the downstream bandwidth of the PON line is an indication of the upper limit of the flash time. With such a configuration, when the capacity of the down buffer, that is, the FIFO 2 is small, it is possible to quickly perform redundant switching without interruption. Further, the gap period can be set flexibly in accordance with the length of the period required for switching the optical switch.

  Moreover, in the station side apparatus which concerns on the 1st Embodiment of this invention, the control part 14 performs control of OSU1-OSU N + 1 (12-1-12-N + 1) collectively. As a result, the cost of the station side device can be reduced. Since the MPCP frame transmission / reception timing has a large allowable range, there is no problem even if the transmission / reception timing slightly varies. Therefore, even if the termination of the MPCP frame is performed by one control unit, there is no particular problem.

  Further, the control unit 14 performs redundant switching of OSUs only by changing the communication path while maintaining the registered state of the ONU. As a result, the redundant switching can be performed quickly and it is not affected by the abnormality of the OSU.

  Further, since redundant switching can be performed by preparing only one spare (standby system) OSU for N OSUs, it is possible to improve the fault tolerance performance without significantly impairing the economy.

  First, redundant switching from the active OSU to the standby OSU is performed without instantaneous interruption, then the operational OSU is replaced, and finally redundant switching from the standby OSU to the replacement active OSU is performed without instantaneous interruption. By doing so, the OSU can be exchanged without affecting the service to the user, so that the maintainability of the network can be improved.

  In the present embodiment, the OSU may have a configuration corresponding to a system in which EPON and 10GEPON coexist. In other words, the station side device is connected to the EPON ONU and the 10GEPON ONU via the same PON line.

  When the above two PONs coexist by performing wavelength multiplexing for both upstream and downstream, OSU redundancy switching is equivalent to switching two OSUs to two standby OSUs in parallel. In this case, among the switching periods obtained individually for the two PONs, the later one may be selected as the switching period.

  Also, when the above two PONs coexist by performing time division multiplexing on the upstream and wavelength multiplexing on the downstream, two systems of FIFO2 (38) and transmission processing unit 34 are provided for EPON and 10GEPON in the OSU 12. . Then, the PON transmission / reception unit 35 converts the electrical signal from the transmission processing unit for EPON and the electrical signal from the transmission processing unit for 10GEPON into optical signals having different wavelengths. Further, the PON transceiver 35 and the reception processor 33 can receive dual rate signals having different rates for each burst. For the downlink signal switching period, the later one of the two times when the two EPON and 10GEPON FIFOs 2 are emptied may be selected as the switching period. Since the uplink signal is time-division multiplexed, the uplink signal switching period is the same for EPON and 10GEPON. Note that the control unit 14 determines from which system the control frame is received, and selects which system to transmit the control frame to.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Second Embodiment>
The present embodiment relates to a station-side device in which the setting method of the redundancy switching timing is changed compared to the station-side device according to the first embodiment. The contents other than those described below are the same as those of the station side apparatus according to the first embodiment.

  In the station side apparatus according to the second embodiment of the present invention, unlike the station side apparatus according to the first embodiment of the present invention, the control unit 14 predicts the time TF when the FIFO 2 of the OSUi becomes empty. Rather than receiving a flash completion notification from the OSUi that the FIFO2 is empty.

  Then, after receiving the flash completion notification, the control unit 14 assigns an upstream gap for optical switch switching.

  With such a configuration, even when the upper limit of the flash time is not efficient, such as when the maximum capacity of the downlink buffer, that is, the FIFO 2 is large, it is possible to quickly perform redundant switching without interruption. Further, the gap period can be set flexibly in accordance with the length of the period required for switching the optical switch.

  However, considering the communication processing between the station side device and the ONU required for this gap allocation, this gap is provided at least after the round trip time between the station side device and the ONU, so the communication stop time in the downlink direction becomes longer. End up.

  Therefore, in the station side apparatus according to the second exemplary embodiment of the present invention, the control unit 14 presets an optical switch switching gap that occurs intermittently in the uplink band allocation processing. Then, upon receiving the flash completion notification, the control unit 14 switches the optical switch 11a in the first optical switch switching gap after the received time, for example.

  FIG. 30 is a flowchart for explaining the details of the OSU switching process (S221) shown in FIG. Steps S260, S261, and S264 to S267 in FIG. 30 are the same as steps S230, S231, and S233 to S236 in the flowchart shown in FIG. 26, and thus detailed description thereof will not be repeated here.

  Referring to FIG. 30, after the processing in step S <b> 261, control unit 14 sets the OSU switching gap request flag to 1. In addition, the control unit 14 sets the next gap interval to the current time and shares it with the band allocation process, that is, enables the reference to the next gap interval in the band allocation process (S262).

  Next, the control unit 14 receives the flash completion notification from the OSUi, and provides the optical switch OSW switching period Pk in the first optical switch switching gap after the time obtained by adding the delay time due to the OSU switching process to the received time. Further, the control unit 14 sets the OSU switching gap request flag to 0 (S263).

  FIG. 31 is a flowchart for explaining details of the bandwidth allocation processing in the station side apparatus according to the second embodiment of the present invention. 27 is the same as the flowchart shown in FIG. 27 except for step S273 in FIG. 31 instead of step S163 in FIG. 27, and detailed description thereof will not be repeated here.

  When the gap request flag is 1 and the current time has passed the next gap interval, the control unit 14 sets TS = TS + ΔOSW. Then, the control unit 14 records TS-ΔOSW as the start time of the optical switch switching gap and sets the next gap interval (S273). Here, the start time of the optical switch switching gap is recorded in a time series on, for example, a ring buffer. Note that the start time before the current time is invalid and may be overwritten.

  Here, ΔOSW is a time set as a switching transition time from when the optical switch 11a starts switching the communication path to when it is completed. Even if the discard and overtaking of the communication signal at the time of redundancy switching is eliminated, it cannot be said that there is no instantaneous interruption if the stop period of the communication signal is too long. The standard of the stop period depends on the application, but in the case of telephone and video, the upper limit is several hundred ms. It is necessary to use the optical switch 11a in which ΔOSW falls within the allowable stop period.

  FIG. 32 is a diagram showing a timing relationship of the non-instantaneous switching operation in the station side apparatus according to the second embodiment of the present invention.

  Referring to FIG. 32, the transmission of the downstream frame is stopped at time TF when the FIFO 2 of OSUi becomes empty. Here, description will be made assuming that the control unit 14 receives a flash completion notification from the OSUi at the time TF.

  The control unit 14 provides the optical switch OSW switching period Pk in the first optical switch switching gap Gk after time TF. The start time of the optical switch switching gap Gk is set to TS-ΔOSW, and the end time is set to TS. Here, ΔOSW is set longer than the optical switch OSW switching period Pk in order to provide a margin.

  Here, as described above, a case is considered where the control unit 14 allocates an upstream gap for optical switch switching after receiving a flash completion notification from the OSUi. In this case, a gap allocation is instructed from the station side device to the ONU at time TF, and after the processing time TP in the ONU has elapsed, the gap GkD is generated. The start time of the gap GkD in the station side device is TG, and the switching timing of the optical switch 11a is after time TG.

  On the other hand, in the configuration in which the control unit 14 provides a plurality of optical switch switching gaps as in the station-side device according to the second embodiment of the present invention, in the optical switch switching gap Gk before time TG. Since the optical switch 11a can be switched, redundant switching can be performed more quickly.

  As described above, in the station side apparatus according to the second embodiment of the present invention, even when the capacity of the downlink buffer, that is, the FIFO 2, is large, the uninterrupted redundant switching can be performed more quickly. In addition, it is possible to prevent the downlink communication stop time from becoming long. Further, the gap period can be set flexibly in accordance with the length of the period required for switching the optical switch.

  In the station apparatus according to the second embodiment of the present invention, when the control unit 14 receives the flash completion notification, it switches the optical switch 11a in the first optical switch switching gap after the received time. Although it is the configuration, it is not limited to this. When the control unit 14 receives the flash completion notification, it receives the flash completion notification among a plurality of optical switch switching gaps set for a predetermined period, such as the second and third optical switch switching gaps after the received time. Even in the configuration in which the optical switch 11a is switched in any one of the optical switch switching gaps thereafter, the redundant switching can be quickly performed.

  FIG. 33 is a flowchart for explaining details of a modification of the band allocation processing in the station side apparatus according to the second embodiment of the present invention. Except for step S274 in FIG. 33 instead of step S273 in FIG. 31, the flowchart is the same as the flowchart shown in FIG. 31, and therefore detailed description will not be repeated here.

  In the station side apparatus according to the second embodiment of the present invention, an optical switch switching gap is provided exclusively for uplink band allocation. However, when ΔOSW is small, the optical switch may be switched in the burst gap period. Here, the burst gap period is a period in which a plurality of ONUs do not transmit uplink communication signals to the station-side apparatus, which are provided between periods in which the plurality of ONUs exclusively transmit uplink communication signals to the station-side apparatus. It is.

  Referring to FIG. 33, control unit 14 sets optical switch switching period Pk in the burst gap period. That is, the control unit 14 records TS−ΔOSW as the start time of the optical switch switching gap (S274).

  FIG. 34 is a flowchart for explaining details of a modified example of the discovery process in the station side apparatus according to the second embodiment of the present invention. Except for step S275 in FIG. 34 instead of step S41 in FIG. 8, it is the same as the flowchart shown in FIG. 8, and thus detailed description thereof will not be repeated here.

  When ΔOSW is large, the optical switch may be switched during the discovery period. Here, the discovery period is a period during which a new ONU that wishes to communicate with the station side apparatus transmits an uplink communication signal to the station side apparatus.

  Referring to FIG. 34, first, control unit 14 sequentially creates discovery gate messages for OSUk (k = 1, 2,..., N) and places them in output message queue Qeg. At this time, the start time is based on TEk or the later of the current time. Then, the control unit 14 sets this start time as the start time of the optical switch switching gap (S275).

  Since the frequency of discovery processing is usually not as high as once per second, for example, it is preferable to use the discovery period in OSU periodic maintenance and OSU replacement work planned in advance rather than at the time of failure.

  In the modification shown in FIGS. 33 and 34, it is necessary to use an optical switch 11a in which ΔOSW is equal to or shorter than these periods. If MEMS (Micro Electro Mechanical Systems) technology and silicon photonics technology are used, it is possible to make ΔOSW on the order of 10 ns.

  As described above, the configuration in which the optical switch is switched in the existing burst gap period or discovery period eliminates the need to separately allocate an upstream band for redundant switching, thereby improving the upstream bandwidth efficiency.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Third Embodiment>
The present embodiment relates to a station-side device in which an active OSU and a standby OSU are configured differently compared to the station-side device according to the first embodiment. The contents other than those described below are the same as those of the station side apparatus according to the first embodiment.

  FIG. 35 is a block diagram showing a configuration example of the standby OSU in the station side apparatus according to the third embodiment of the present invention.

  Referring to FIG. 35, the standby OSUj further includes a storage unit 72 and includes a local control unit 81 instead of the local control unit 36 as compared with the OSU 12 shown in FIG. The local control unit 81 includes a maintenance management unit 71.

  The maintenance management unit 71 performs various maintenance management in the station side device. For example, in order to add a function or solve a problem in advance, after performing redundant switching from OSUi to OSUj as shown in FIG. 26, OSUi is removed from the station side device and replaced. At this time, the OSUj communicates with the ONU instead of the OSUi and performs necessary maintenance management by the maintenance manager 71.

  The storage unit 72 is a flash memory, for example, and is accessed by the local control unit 81 and stores ONU firmware, that is, a program to be executed by the ONU. The maintenance management unit 71 downloads the program stored in the storage unit 72 to the ONU.

  There is known a network system that can update the program, that is, firmware, from a station side device to a terminal device having a generally programmable structure such as an ONU.

  In the PON, the program data is downloaded from the station side device to the ONU using the OAM link. In this way, it is possible to repair a defect caused by a program error and add a function of the terminal device without exchanging the terminal device and without taking time and effort for the user. Thereby, the maintainability of the network system can be remarkably improved.

  In the station apparatus according to the third embodiment of the present invention, only the OSUj has an ONU firmware update function. When it is desired to update the firmware of the ONU under the OSUi, after the redundant switching from the OSUi to the OSUj, the OSUj updates the ONU firmware. Then, redundant switching from OSUj to OSUi is performed, and switching back to OSUi.

  As another maintenance management function, the PON transmission / reception unit 35 in OSUj may have a function of monitoring the quality of an optical reception signal. The quality of the optical reception signal includes power, wavelength, extinction ratio, jitter deviation, error rate, and the like. Further, the control unit 14 may be configured to continuously receive the results monitored by the PON transmission / reception unit 35 and monitor changes with time.

  In the station side apparatus according to the first embodiment and the second embodiment of the present invention, the active OSUi (i = 1, 2,..., N) and the redundant OSUj (j = N + 1) Had the same configuration. However, as in the station side apparatus according to the third embodiment of the present invention, it is possible to reduce the cost of the entire station side apparatus by differentiating the operating OSU and the redundant OSU. is there. In other words, the overall cost can be reduced by concentrating the functions of the maintenance management system on the OSUj while limiting the other OSUi to simple functions.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Fourth embodiment>
The present embodiment relates to a station-side device in which a concentrator and a controller are duplicated compared to the station-side device according to the first embodiment. The contents other than those described below are the same as those of the station side apparatus according to the first embodiment.

  FIG. 36 is a block diagram showing a schematic configuration of the station side apparatus according to the fourth embodiment of the present invention.

  The station side device 1b includes a 1-system concentrator 13a-1, a 2-system concentrator 13a-2, a 1-system controller 14-1, and a 2-system controller 14-2.

  FIG. 37 is a diagram illustrating a configuration example of the optical switch 11b according to the fourth embodiment of the present invention. This optical switch 11b differs from the optical switch 11a in the first embodiment shown in FIG. 2 only in that a system selection unit 25 is added. The system selection unit 25 selects either a control signal from the first system control unit 14-1 or a control signal from the second system control unit 14-2.

  The system selection unit 25 continuously performs management communication with the first system control unit 14-1 and the second system control unit 14-2, autonomously determines the control unit that is the active system, and operates. A control signal from the control unit serving as a system is output to the actuator 21.

  The control IF unit 32 of the OSU 12 shown in FIG. 3 has an interface between the 1-system control unit 14-1 and the 2-system control unit 14-2. The control IF unit 32 continuously performs management communication with the first system control unit 14-1 and the second system control unit 14-2 via this interface, and autonomously controls the control unit that is in the operation system. Judgment. The control IF unit 32 processes only the signal from the active control unit, and outputs the same signal to both control units.

  Similarly, the concentrating IF unit 31 has an interface between the first system control unit 14-1 and the second system control unit 14-2. The concentrator IF31 outputs the upstream frame to both the concentrators 13a-1 and 13a-2, and outputs the downstream frame sent from both systems to the FIFO2 (38). Since no downstream frame is sent from the concentrator of the standby system, no collision occurs. Further, an input signal from the standby system may be blocked in preparation for an abnormality in the concentrator. In this case, the control unit 14-1 or 14-2 performs system selection via the control IF unit 32.

  The control IF unit 44 of the concentrator 13a shown in FIG. 4 has an interface between the first system control unit 14-1 and the second system control unit 14-2. The control IF unit 32 continuously performs management communication with the first system control unit 14-1 and the second system control unit 14-2 via this interface, and autonomously controls the control unit that is in the operation system. Judgment. The control IF unit 44 processes only the signal from the active control unit, and outputs the same signal to both control units.

  When the concentrator is a double system, the path selection is reflected in the path connection / path disconnection setting in the filter unit 46a. The active control unit gives this instruction via the control IF unit 44. For example, when the concentrating unit supports 1: 1 redundancy, both the upstream path and the downstream path of all the filter units may be set to be disconnected for the standby concentrating unit. Further, in the case of supporting 1 + 1 redundancy, it is only necessary to set the downstream paths of all the filter units to disconnection for the standby line concentrator.

  The IO control unit 54 of the control unit 14 shown in FIG. 5 can interface with the IO control unit of the other control unit. The CPU 51 performs management communication with another system CPU via the IO control unit 54 and autonomously determines whether to be an active system or a standby system. In some cases, the operation / standby system is explicitly instructed from the operation IF. Since signals from each part of the station side device are input to both systems, it is possible to trace the state change in the station side device and the state of the PON line even in the standby system.

  With the redundancy of the concentrator, 1: 1 redundancy, 1 + 1 redundancy, and load distribution are possible. Here, the load distribution means that the OSU is divided into two groups (group A and group B). In normal times, the 1-system concentrator 13a-1 collects the group A, and the 2-system controller 14-2 Concentrate Group B. For example, when a failure occurs in the first line concentrator 13a-1 or the uplink, the second line concentrator 13a-2 switches so that both groups are concentrated. When performing 1: 1 redundancy or load balancing, the uplink transmission / reception unit 41 of the concentrator 13a performs management communication via the uplink, monitors the uplink state, and receives a failure notification from the opposite device. When there is an abnormality, a corresponding alarm is notified to the control unit 14.

  When recognizing an abnormality in the active line concentrator, the control unit 14 switches to another system when the other line concentrator is normal. This switching is performed by changing the path setting of the filter unit 46a of the concentrator 13a according to the redundant configuration (1: 1, 1 + 1, load distribution). In the case of load distribution, the control unit 14 receives an instruction from the outside via the operation IF, and changes the path setting of the filter unit 46a of the line concentrator 13a to restore the load distribution state.

  When the control unit 14 is switched, the bandwidth allocation is taken over. There are an operation of strictly taking over the past allocation and an operation of performing a new bandwidth calculation without taking over the past allocation. In the former case, the active control unit notifies the standby control unit including the OSU that transmitted the control message transmitted to each PON line.

  As described above, according to the station side apparatus according to the fourth embodiment of the present invention, the control unit and the concentrator in the station side apparatus according to the first embodiment are made redundant. In addition to the effects described in the first embodiment, it is possible to further improve the fault tolerance performance without significantly impairing the economy.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Fifth embodiment>
The present embodiment relates to a station-side device in a PON system in which each PON line is duplicated as compared with the station-side device according to the first embodiment. The contents other than those described below are the same as those of the station side apparatus according to the first embodiment.

  In the station apparatus according to the first embodiment of the present invention, the downlink communication signal received from the switching destination OSUj is transferred to the PON line from the communication path for outputting the downlink communication signal received from the switching source OSUi to the PON line. When the optical switch 11a switches to the output communication path, it is assumed that the PON line is the same before and after the switching, but the present invention is not limited to such a configuration. For example, the PON line is duplexed in the PON system, and the downstream communication signal received from the switching destination OSUj is transmitted from the communication path that outputs the downstream communication signal received from the switching source OSUi to the active PON line. Even when the optical switch 11a performs switching to the communication path to be output to the PON line, the redundant switching according to the present embodiment can be applied.

  FIG. 38 is a block diagram showing a schematic configuration of the station side apparatus according to the fifth embodiment of the present invention.

  Referring to FIG. 38, in PON system 302, PON line i (i = 1, 2,..., N) is duplexed (hereinafter, PON line i is A-system PON line iA and B-system Including PON line iB). The PON system 302 includes a station-side device 1c, (2 × N) PON lines 1A to NA (3-1A to 3-NA) and 1B to NB (3-1B to 3-NB) which are optical fibers. , (2 × N) optical couplers 4-1A to 4-NA and 4-1B to 4-NB, and a plurality of home units (ONUs) 2. The station-side apparatus 1c includes an optical switch unit 11c, OSU1 to N + 1 (12-1 to 12-N + 1), a concentrator 13a, and a control unit 14 that performs overall control of the station-side apparatus 1c. N is an integer of 2 or more.

  The station side device 1c is connected to (2 × N) PON lines 1A to NA and 1B to NB, and terminates the (2 × N) PON lines. The PON lines 1A to NA and 1B to NB are connected to optical couplers 4-1A to 4-NA and 4-1B to 4-NB, respectively, and are connected to a plurality of ONUs 2 through these optical couplers. . The PON lines iA and iB are connected to a plurality of common ONUs 2 via optical couplers 4-iA and 4-iB, respectively.

  FIG. 39 is a block diagram showing a schematic configuration of the optical switch unit in the fifth embodiment of the present invention. FIG. 40 is a diagram showing a schematic configuration related to the uninterruptible switching operation in the station side apparatus according to the fifth embodiment of the present invention.

  Referring to FIGS. 39 and 40, the optical switch unit 11c has two interfaces for the PON line iA and the PON line iB in correspondence with the duplication of the PON line i (i = 1, 2,..., N). Is provided. That is, the optical switch unit 11c includes an N: 1 optical switch OSWn and a 2: 1 optical switch OSW2i (i = 1, 2,..., N).

  The N: 1 optical switch OSWn has the same configuration as the optical switch 11a according to the first embodiment of the present invention. In the present embodiment, a 2: 1 optical switch OSW2i (i = 1, 2,..., N) is further connected to the PON line side of the N: 1 optical switch OSWn for each PON line. That is, the N: 1 optical switch performs redundant switching of the OSU, and the 2: 1 optical switch performs redundant switching of the PON line. The configuration of the 2: 1 optical switch is the same as that of the optical switch when N = 1 in FIG. 2, but the left and right directions in FIG. 2 are reversed.

  That is, the N: 1 optical switch OSWn follows a command from the control unit 14 and communicates between N + 1 OSU1 to N + 1 (12-1 to 12-N + 1) and N 2: 1 optical switch OSW2i. Switch.

  The 2: 1 optical switch OSW2i switches the communication path between the N: 1 optical switch OSWn and the PON lines iA and iB in accordance with an instruction from the control unit 14.

  The ONU 2 in the PON system 302 is connected to the A-system and B-system PON lines. In the downstream direction, the ONU 2 selects a system to which a valid downstream frame is transmitted from the A-system and B-system PON lines. The ONU 2 operates in either the 1: 1 redundancy mode in which the uplink frame is transmitted to one of the A-system and B-system PON lines and the 1 + 1 redundancy mode in which the same uplink frame is transmitted to both systems in the uplink direction. To do. When the ONU 2 operates in the 1: 1 redundancy mode, the ONU 2 further selects the autonomous autonomous redundancy mode in which the effective downlink frame is transmitted with respect to the selection of the uplink system. The system operates in one of 1: 1 dependent redundancy modes in which a system is selected in accordance with an explicit instruction from the station side device by an OAM message or the like. Here, in order to simplify the explanation, it is assumed that these operation modes are unified between the ONUs 2 connected to the same PON line.

  FIG. 41 is a flowchart for explaining details of the switching processing in the station-side apparatus according to the fifth embodiment of the present invention. In the station apparatus according to the fifth embodiment of the present invention, the OSU switching process (S213) of FIG. 21 and the OSU switching process (S221) of FIG. 23 in the first embodiment of the present invention are shown in FIG. It replaces the switching process shown.

  Referring to FIG. 41, control unit 14 is in a case where execution of switching processing is instructed for the purpose of planned maintenance, that is, periodic maintenance of OSU or PON line and replacement work of OSU or PON line planned in advance ( If the purpose of OSU maintenance is YES (YES in S301), an OSU switching process is performed (S305), and the process is terminated. Since this OSU switching process is the same as the OSU switching process shown in FIG. 26, detailed description will not be repeated here.

  In addition, when the purpose is maintenance of the PON line (YES in S301, NO in S302, YES in S303), the control unit 14 performs the PON line switching process (S306) and ends the process.

  If execution of the switching process is instructed due to the occurrence of a failure (NO in S301), an instantaneous switching process is performed (S304), and the process is terminated.

  In planned maintenance, OSU redundancy switching and PON line redundancy switching may be considered independently. That is, when it is desired to maintain the OSU, the redundant switching of only the OSU is performed, and when it is desired to maintain the PON line, the redundant switching of only the PON line is performed. However, when a failure occurs, it is usually not possible to immediately identify which of the OSU and PON lines is defective, so it is reasonable to perform redundant switching of OSUs and redundant switching of PON lines in parallel.

  FIG. 42 is a flowchart for explaining details of the instantaneous switching process (S304) shown in FIG.

  First, the control unit 14 switches both the optical switches OSW and OSW2i (S311). That is, the control unit 14 performs redundant switching from, for example, OSUi to OSUj by switching the optical switch OSW. In parallel with this, the control unit 14 performs redundant switching from, for example, the PON line iA to the PON line iB by switching the optical switch OSW2i. Details of the PON line switching process will be described later.

  Next, when the ONU 2 is operating in the 1: 1 dependent redundancy mode, the control unit 14 instructs the ONU 2 connected to the PON line i via the PON line i using the OAM message. Is broadcast (S312).

  Next, the control unit 14 notifies the standby control unit of switching from OSUi to OSUj and switching from the PON line iA to the PON line iB, and ends the process (S313).

  FIG. 43 is a flowchart for explaining details of the PON line switching process (S306) shown in FIG.

  First, the control unit 14 refers to the uplink burst allocation final time TEi for the PON line i calculated in the band allocation process shown in FIG. Then, the control unit 14 provides the switching period P1 of the optical switch OSW2i after max {ctimeP, TEi}, that is, the time ctimeP and the later time of the time TEi. The control unit 14 associates the period P1 with the identifier i of the virtual OSU representing the switching target and shares it with the band allocation process, that is, enables the period P1 and the identifier i to be referred to in the band allocation process (S321). Here, the time ctimeP is a time obtained by adding a delay time due to the PON line switching process to the current time ctime. The switching period of the optical switch OSW2i is obtained by adding the ONU reception overhead time to the switching transition period from when the optical switch OSW2i starts switching the communication path to when it is completed. The reception overhead time in the ONU is the sum of the time required for the optical receiving unit to become stable again and the resynchronization time of the data recovery circuit due to the instantaneous interruption of the optical signal in the ONU.

  Next, the control unit 14 instructs the OSU IF unit 55 to change the setting related to the virtual OSUi for OSU conversion from OSUmap (i) = i to OSUmap (i) = i in the period P1 (S322). That is, the destination OSU described in the downlink control message received from the output message queue Qeg is changed from OSUi to OSUi. Further, the OSU IF unit 55 temporarily stops taking out the control message from the output message queue Qeg corresponding to the virtual OSUi in the period P1. That is, the control unit 14 does not substantially perform OSU conversion, but stops transmission of the control message in the period P1.

  Then, when the current time reaches the start time of the period P1, the control unit 14 instructs the optical switch OSW2i to stop the transmission of the downstream frame of the OSUi, for example, and switches from the PON line iA side to the PON line iB side. (S323).

  Then, when the current time reaches the end time of the period P1, the control unit 14 instructs the OSUi to start transmission of the downlink frame (S324).

  Next, when the ONU 2 is operating in the 1: 1 dependent redundancy mode, the control unit 14 instructs the ONU 2 connected to the PON line i via the PON line i using the OAM message. Is broadcast (S325).

  Next, the control unit 14 notifies the standby control unit of, for example, switching from the PON line iA side to the PON line iB side, and ends the process (S326).

  As described above, the communication control method according to the fifth embodiment of the present invention includes an optical line unit that terminates a passive optical network that is redundantly duplicated or more, and this redundant passive optical. An optical switch that switches a communication path between the network and the optical line unit, and a controller that controls switching of the optical switch and transmission of uplink communication signals by a plurality of home-side devices connected to the passive optical network, An optical line unit is a communication control method in a station-side device that transmits downlink communication signals to a plurality of home-side devices via an optical switch and receives uplink communication signals from the plurality of home-side devices via an optical switch. The control unit switches off the optical switch so that the optical switch does not receive uplink communication signals from a plurality of home-side devices during the switching transition period in which the optical switch switches the communication path. A step of setting a switching timing and a transmission timing of a plurality of home-side devices, a step of stopping the output of the downlink communication signal to the optical switch by the optical line unit prior to the switching timing of the optical switch set by the control unit, The switch includes a step of switching the communication path based on the set switching timing, and a step of the optical line unit starting output of the downlink communication signal to the optical switch.

Thereby, redundant switching of the PON line can be performed without interruption.
A station apparatus according to the fifth embodiment of the present invention is a station apparatus in an optical network system provided with N sets of passive optical networks having at least one redundant configuration. Communication path switching between an optical line unit, J spare optical line units, N optical line units, J spare optical line units, and N sets of passive optical networks, and a redundant configuration The set of passive optical networks includes an optical switch that selects any one of the passive optical networks, and a control unit that controls switching of the optical switches. J is an integer of 1 or more.

  Preferably, in the station side device, the control unit controls transmission of the uplink communication signal to the plurality of home side devices connected to the plurality of passive optical networks.

  More preferably, in this station-side device, the control unit switches the optical switch switching timing and the plurality of optical switches so that the optical switch does not receive uplink communication signals from the plurality of home-side devices during the switching transition period in which the setting of the optical switch is changed. The transmission timing of the home device is controlled.

  When duplexing PON lines, OSUs are also usually duplexed, so (2 × N) OSUs are required. However, according to the fifth embodiment of the present invention, the number of OSUs may be (N + 1), so that the cost of the station side device can be reduced. Furthermore, since the control unit provided independently of the OSU collectively controls transmission of uplink communication signals by the ONU, it is possible to perform redundancy switching while maintaining the ONU registration state. Thereby, quick redundancy switching becomes possible. Furthermore, since the control unit controls the switching timing of the optical switch and the transmission timing of the plurality of home-side devices, it is possible to perform OSU maintenance and PON line maintenance without interruption.

  The station side apparatus according to the fifth embodiment of the present invention is configured such that redundant switching of the PON line is not performed during OSU maintenance, and redundant switching of the OSU is not performed during PON line maintenance. However, the present invention is not limited to this. In these maintenances, OSU redundancy switching and PON line redundancy switching may be performed in parallel. In this case, the longer one of the switching time of the optical switch OSWn and the switching time of the optical switch OSW2i may be selected as the optical switch switching time.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Sixth Embodiment>
The present embodiment relates to a station-side apparatus that is compatible with a PON system in which each PON line is duplicated as compared with the station-side apparatus according to the second embodiment to which a modification of the band allocation process shown in FIG. 33 is applied. In addition to the PON line switching process described below, the configuration and operation for supporting duplication of each PON line are the same as those in the station-side apparatus according to the fifth embodiment.

  In this embodiment, the ONU 2 operates in the 1 + 1 redundancy mode, and is adjusted so that the difference in the propagation time of the frames in the redundant PON line i, that is, the PON line iA and the PON line iB is smaller than the burst gap. Assuming that

  FIG. 44 is a flowchart for explaining details of the PON line switching process (S306) shown in FIG.

  First, the control unit 14 selects the earliest time after the time ctimeP from the recorded start times of the optical switch switching gap, and sets the optical switch OSW2i in the optical switch switching gap corresponding to the selected start time. A switching period P1 is provided (S331).

  Next, the control unit 14 instructs the OSU IF unit 55 to change the setting related to the virtual OSUi for OSU conversion from OSUmap (i) = i to OSUmap (i) = i in the period P1 (S332). That is, the destination OSU described in the downlink control message received from the output message queue Qeg is changed from OSUi to OSUi. Further, the OSU IF unit 55 temporarily stops taking out the control message from the output message queue Qeg corresponding to the virtual OSUi in the period P1. That is, the control unit 14 does not substantially perform OSU conversion, but stops transmission of the control message in the period P1.

  Then, when the current time reaches the start time of the period P1, the control unit 14 instructs the optical switch OSW2i to stop the transmission of the downstream frame of the OSUi, for example, and switches from the PON line iA side to the PON line iB side. Is instructed (S333).

  Then, when the current time reaches the end time of the period P1, the control unit 14 instructs the OSUi to start transmission of the downlink frame (S334).

  Next, the control unit 14 notifies the standby control unit of, for example, switching from the PON line iA side to the PON line iB side, and ends the process (S335).

  As described above, the communication control method according to the sixth embodiment of the present invention includes an optical line unit that terminates a passive optical network that is redundantly duplicated or more, and this redundant passive optical. An optical switch that switches a communication path between the network and the optical line unit, and a controller that controls switching of the optical switch and transmission of uplink communication signals by a plurality of home-side devices connected to the passive optical network, An optical line unit is a communication control method in a station-side device that transmits downlink communication signals to a plurality of home-side devices via an optical switch and receives uplink communication signals from the plurality of home-side devices via an optical switch. And a step of recording a gap period during which the plurality of home devices stop transmitting uplink communication signals, provided when the control unit sets transmission timings of the plurality of home devices. The step of selecting a gap period in which the switching timing of the optical switch should be set from the recorded gap period, and prior to the switching timing of the optical switch set by the control unit, the optical line unit A step of stopping output to the optical switch, a step of the optical switch switching the communication path based on the set switching timing, and a step of starting the output of the downlink communication signal to the optical switch by the optical line unit. including.

  In the fifth embodiment of the present invention, after a request for redundant switching of a PON line is generated, a switching period is set in a period in which a band is not yet allocated by band allocation processing. For this reason, a delay of at least a round-trip propagation time between the ONU and the OSU usually occurs until the actual redundant switching is performed. On the other hand, in the sixth embodiment of the present invention, since the burst gap period recorded in advance in the band allocation process is used as the optical switch switching period, redundant switching can be performed quickly.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1a, 1b Station side device, 2 home side device (ONU), 3-1 to 3-N PON line, 4-1 to 4-N optical coupler, 11a and 11b optical switch, 12-1 to 12-N + 1 OSU, 13, 13a-1, 13a-2 Concentrating part, 14, 14-1, 14-2 Control part, 21 Actuator, 22 Movable mirror, 23-1 to 23-N + 1, 241-1 to 24-N Collimating lens, 25 System selection unit, 31 Concentration IF unit, 32 Control IF unit, 33 Reception processing unit, 34 Transmission processing unit, 35 PON transmission / reception unit, 36 Local control unit, 37 FIFO1, 38 FIFO2, 41 Uplink transmission / reception unit, 42 Downstream distribution unit 43 Concentration control unit, 44 Control IF unit, 45-1 to 45-N + 1 OSU IF unit, 46a-1 to 46a-N + 1 Filter unit, 47-1 to 47-N + FIFO, 48 selector, 51 CPU, 52 ROM, 53 RAM, 54 IO controller, 55 OSU IF section, 56 shared RAM, 57 watch timer, 301 PON system.

Claims (10)

A plurality of optical line units including one or more backup optical line units and communicating with a plurality of home-side devices via a plurality of passive optical networks;
An optical switch for switching communication paths between the plurality of passive optical networks and the plurality of optical line units;
A controller that controls switching of the optical switch and transmission of uplink communication signals by the plurality of home-side devices,
Each optical line unit transmits a downlink communication signal to the plurality of home side devices via the optical switch, and receives an upstream communication signal from the plurality of home side devices via the optical switch. A communication control method,
The switching source optical line unit stops outputting the downlink communication signal to the optical switch;
From the communication path for outputting the downlink communication signal received from the switching source optical line unit to the passive optical network, the downlink communication signal received from the switching destination optical line unit is output to the passive optical network. During the switching transition period from the start of the optical switch to the completion of switching to the communication path, the control unit prevents the optical switch from receiving the uplink communication signal from the plurality of home-side devices. Setting switch switching timing and transmission timing of the plurality of home-side devices;
The optical switch switching the communication path based on the set switching timing;
A communication control method including the step of the switching destination optical line unit starting output of the downlink communication signal to the optical switch. The station side device further includes:
A concentrator that distributes downstream communication signals from the upper network to each optical line unit,
Each of the optical line units includes a buffer for accumulating the downlink communication signal received from the concentrator, and transmits the accumulated downlink communication signal to the plurality of home side devices via the optical switch,
The communication control method further includes:
Before the optical switch switches the communication path, the concentrator includes a step of switching the output destination of the downlink communication signal from the switching source optical line unit to the switching destination optical line unit;
In the step of setting the switching timing and the transmission timing, the control unit predicts the timing at which the switching source optical line unit completes transmission of the downlink communication signal stored in the buffer of the switching unit, A gap period after the predicted timing and longer than the switching transition period is set so that the plurality of home devices stop transmitting the uplink communication signal, and the switching transition period is included in the gap period. The communication control method according to claim 1, wherein a switching timing of the optical switch is set in the network. The station side device further includes:
A concentrator that distributes downstream communication signals from the upper network to each optical line unit,
Each of the optical line units includes a buffer for accumulating the downlink communication signal received from the concentrator, and transmits the accumulated downlink communication signal to the plurality of home side devices via the optical switch,
The communication control method further includes:
Before the optical switch switches the communication path, the concentrator includes a step of switching the output destination of the downlink communication signal from the switching source optical line unit to the switching destination optical line unit;
In the step of setting the switching timing and the transmission timing, the control unit receives a notification that the switching-source optical line unit has completed transmission of the downlink communication signal accumulated in its buffer. The switching timing of the optical switch is set so that the gap period is longer than the switching transition period and the plurality of home-side devices stop transmission of the uplink communication signal, and the switching transition period is included in the gap period. The communication control method according to claim 1, wherein:   In the step of setting the switching timing and the transmission timing, the control unit sets a plurality of the gap periods, and among the plurality of gap periods, the switching source optical line unit is accumulated in its own buffer. 4. The switching timing of the optical switch is set so that the optical switch switches the communication path in any of the gap periods after receiving notification that transmission of the downlink communication signal is completed. Communication control method.   In the step of setting the switching timing and the transmission timing, the control unit sets a discovery period in which a new home device that desires communication with the station-side device transmits the uplink communication signal to the station-side device. The communication control method according to claim 3, wherein the communication control method is set as the gap period.   In the step of setting the switching timing and the transmission timing, the control unit is provided between each period in which the plurality of home side devices exclusively transmit the uplink communication signal to the station side device. The communication control method according to claim 3, wherein a period in which a plurality of home-side devices do not transmit the uplink communication signal to the station-side device is set as the gap period. A maintenance management method in a station apparatus for executing the communication control method according to claim 1,
The backup optical line unit includes a maintenance management unit for performing maintenance management,
The backup optical line unit is the switching destination optical line unit, and the optical line unit other than the backup optical line unit is the switching source optical line unit,
A maintenance management method including a step of performing maintenance management by the maintenance management unit after the backup optical line unit starts outputting the downlink communication signal to the optical switch. A plurality of optical line units including one or more backup optical line units and communicating with a plurality of home-side devices via a plurality of passive optical networks;
An optical switch for switching communication paths between the plurality of passive optical networks and the plurality of optical line units;
A controller that controls switching of the optical switch and transmission of uplink communication signals by the plurality of home-side devices,
Each of the optical line units transmits a downlink communication signal to the plurality of home devices via the optical switch, and receives an uplink communication signal from the plurality of home devices via the optical switch,
The control unit receives the downlink communication signal received from the switching destination optical line unit from the communication path for outputting the downlink communication signal received from the switching source optical line unit to the passive optical network. The optical switch is configured so that the optical switch does not receive the uplink communication signals from the plurality of home-side devices during a switching transition period from when the optical switch starts to switch to a communication path that outputs to the optical network. A station-side device that controls switch switching timing and transmission timings of the plurality of home-side devices. A plurality of optical line units including one or more backup optical line units and communicating with a plurality of home-side devices via a plurality of passive optical networks;
A switch that controls switching of an optical switch that switches communication paths between the plurality of passive optical networks and the plurality of optical line units, and a control unit that controls transmission of uplink communication signals by the plurality of home-side devices,
Each of the optical line units transmits a downlink communication signal to the plurality of home devices via the optical switch, and receives an uplink communication signal from the plurality of home devices via the optical switch,
The control unit receives the downlink communication signal received from the switching destination optical line unit from the communication path for outputting the downlink communication signal received from the switching source optical line unit to the passive optical network. The optical switch is configured so that the optical switch does not receive the uplink communication signals from the plurality of home-side devices during a switching transition period from when the optical switch starts to switch to a communication path that outputs to the optical network. A station-side device that controls switch switching timing and transmission timings of the plurality of home-side devices. The backup optical line unit is:
A memory for storing a program to be executed by the home side device;
The station apparatus according to claim 8, further comprising a maintenance management unit that downloads the program stored in the memory to the home apparatus.

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