JP6127613B2 - Communication system, home apparatus, communication control method, and station apparatus - Google Patents

Description

  The present invention relates to a communication system, a home apparatus, a communication control method, and a station apparatus, and more particularly, to a communication system, a home apparatus, a communication control method, and a station apparatus having a redundant configuration.

  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.

  In IEEE Std 802.3ah (registered trademark) -2004 (non-patent document 1), a plurality of home side devices (ONU: Optical Network Unit) share an optical communication line, and a station side device (OLT: Optical Line Terminal). One method of a passive optical network (PON), which is a medium-sharing communication that performs data transmission with the network, is disclosed. That is, EPON (Ethernet (registered trademark) PON) in which all information is communicated in the form of an Ethernet (registered trademark) frame, including user information passing through the PON and control information for managing and operating the PON, and EPON An 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. Non-Patent Document 1 describes a registration method for a new home device, a report indicating a bandwidth allocation request, and a gate indicating a transmission instruction using an MPCP message.

  As a next-generation technology of GE-PON, which is an EPON that realizes a communication speed of 1 gigabit / second, 10G-EPON standardized as IEEE 802.3av (registered trademark) -2009, that is, a communication speed of 10 gigabit / second. Even in EPON equivalent to seconds, the access control protocol is predicated on MPCP.

  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.

  As an example of the redundant configuration of the station side device in the PON system, for example, Japanese Patent No. 4807200 (Patent Document 1) discloses the following optical termination system. That is, a plurality of working optical termination units respectively connected to a plurality of user optical termination devices via an optical transmission line, each connected to each user optical termination device according to management information of each connected user optical termination device A plurality of working optical termination units that control communication, a standby optical termination unit comprising a storage device capable of storing priority management information of the management information of the plurality of working optical termination units, and the plurality of working light And a control device for controlling switching from the faulty unit in which the fault occurs in the termination unit to the backup optical termination unit. Prior to the occurrence of the failure, the control device transfers the priority management information of the working optical termination unit to the backup optical termination unit, and the failure occurs in the backup optical termination unit in response to the occurrence of the failure. Instruct the unit to act. In accordance with the proxy instruction from the control device, the standby optical termination unit substitutes the faulty unit using the priority management information of the faulty unit, and transmits the priority management information other than the faulty unit. Discard it and free its memory space.

IEEE Std 802.3ah (registered trademark) -2004

Japanese Patent No. 4807200

  In the PON system, in order to communicate between the station side apparatus and the ONU, the station side apparatus and the ONU need to be synchronized.

  When the station-side apparatus includes a plurality of OSUs (Optical Subscriber Units) for transmitting and receiving optical signals to and from the ONU, in the redundant switching from the active OSU to the standby OSU, the ONU switches to the switching destination OSU. Need to synchronize anew. A certain amount of time is required for the synchronization state of the switching destination OSU in the ONU to become stable. However, if communication is started between the switching destination OSU and the ONU before the synchronization state of the ONU is stabilized, Communication data may be lost.

  The present invention has been made to solve the above-described problems, and its purpose is to prevent loss of communication data between the station side device and the home side device when performing redundant switching of the station side device, and to improve reliability. To provide a communication system, a home side apparatus, a communication control method, and a station side apparatus that can provide a high communication system.

  In order to solve the above problems, a communication system according to an aspect of the present invention includes one or a plurality of home-side devices and a plurality of optical line units for transmitting and receiving control frames and data frames to and from the home-side devices. A switching control unit for performing switching processing from the active optical line unit to the standby optical line unit, and a communication partner of the switching source optical line unit. The condition for guaranteeing the synchronization between the home side device and the switching destination optical line unit is satisfied in a state in which a control frame can be transmitted from the home side device to the switching destination optical line unit. And a communication control unit for performing processing for starting transmission of a data frame from the home device to the switching destination optical line unit; Provided.

  In this way, by confirming the synchronization state of the home side device and then starting transmission of the data frame from the switching destination optical line unit to the home side device, loss of communication traffic after the switching process can be prevented. it can. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  A communication system according to another aspect of the present invention includes one or a plurality of home-side devices and a station-side device including a plurality of optical line units for transmitting and receiving control frames and data frames to and from the home-side devices. A switching control unit for performing a switching process from the active optical line unit to the standby optical line unit, and the home apparatus that is a communication partner of the switching source optical line unit. The home side device after determining that the data frame can be transmitted from the home side device to the switching destination optical line unit in a state where a control frame can be sent from the home side device to the switching destination optical line unit. And a communication control unit for performing a process of starting transmission of a data frame to the switching destination optical line unit.

  In this way, by confirming the synchronization state of the home side device and then starting transmission of the data frame from the switching destination optical line unit to the home side device, loss of communication traffic after the switching process can be prevented. it can. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  Preferably, the communication control unit is configured to switch from the home-side apparatus to the switching destination optical line after a predetermined time has elapsed since the switching process from the active optical line unit to the standby optical line unit has been performed. A process for starting transmission of a data frame to the unit is performed.

  With such a configuration, it is possible to determine whether or not the synchronization state of the home device is stable by a simple process.

  Preferably, the home-side device performs synchronization processing for synchronizing itself with the station-side device using a signal received from the station-side device, and the communication control unit acquires information indicating completion of the synchronization processing. Then, a process of starting transmission of a data frame from the home device to the switching destination optical line unit is performed.

  With such a configuration, it is possible to accurately determine that the synchronization state of the home device is stable.

  In order to solve the above problems, a home apparatus according to an aspect of the present invention is a home apparatus for transmitting / receiving a frame to / from a station apparatus including a plurality of optical line units. A synchronization processing unit for performing synchronization processing to synchronize with the station side device, the state of the synchronization processing unit includes an unsynchronized state, a quasi-synchronized state, and a synchronization completion state. Furthermore, the communication control part for suppressing the data length of the said frame which the said home side apparatus transmits in the said quasi-synchronization state shorter than the data length of the said frame which the said home side apparatus transmits in the said synchronization completion state is provided. .

  In this way, after the switching process, three states are provided regarding the synchronization of the synchronization processing unit in the home-side device, and the data length of the frame transmitted to the station-side device is suppressed according to the state transition of the synchronization processing unit. It is possible to prevent a loss of communication traffic due to a transmission clock shift in the home device. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  Preferably, the state of the synchronization processing unit transits from the non-synchronized state to the synchronization completed state via the quasi-synchronized state.

  In this way, the data length of the frame to be transmitted to the station side device is suppressed in the quasi-synchronous state which is the previous stage of the synchronization completion state, so that after the switching process, the communication traffic accompanying the transmission clock shift in the home side device is reduced. Defects can be prevented.

  Preferably, the synchronization processing unit includes a PLL circuit, and includes a reception clock recovery circuit for extracting a reception clock from a signal received from the station side device using the PLL circuit, and a PLL circuit. A transmission clock for generating a transmission clock synchronized with the reception clock extracted by the reception clock recovery circuit using a circuit and for retiming data to be transmitted to the station side device with the generated transmission clock A time constant of the PLL circuit in the transmission clock recovery circuit is larger than a time constant of the PLL circuit in the reception clock recovery circuit.

  With such a configuration, in particular, the reception margin of the downstream optical signal from the station side device is increased, and the frequency accuracy of the upstream optical signal to the station side device is increased, and after the switching process, the transmission clock of the home side device is increased. Loss of communication traffic due to the deviation can be prevented. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  In order to solve the above problems, a communication control method according to an aspect of the present invention includes one or a plurality of home-side devices, and a plurality of optical line units for transmitting and receiving control frames and data frames to and from the home-side devices. A communication control method in a communication system including a station-side device including the home-side device, wherein the home-side device performs reception recovery processing that extracts a reception clock from a signal received from the station-side device, and is extracted by the reception recovery processing. In addition to generating a transmission clock synchronized with the reception clock, the transmission recovery processing is performed to transmit the data to be transmitted to the station-side device to the station-side device according to the timing of the generated transmission clock. Performing a switching process from the optical line unit to the standby optical line unit; After the reprocessing is enabled in the home side device that is the communication partner of the switching source optical line unit, transmission of the control frame from the home side device to the switching destination optical line unit is permitted. And holding the transmission permission of the data frame from the home side device to the switching destination optical line unit, and performing the transmission recovery processing at the communication partner of the switching source optical line unit. And permitting transmission of the reserved data frame after it becomes possible in a certain home device.

  In this way, by confirming the synchronization state of the home side device and then starting transmission of the data frame from the switching destination optical line unit to the home side device, loss of communication traffic after the switching process can be prevented. it can. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  In order to solve the above problems, a station apparatus according to an aspect of the present invention includes a plurality of optical line units for transmitting / receiving control frames and data frames to / from one or a plurality of home apparatuses, A switching control unit for performing a switching process from the line unit to the standby optical line unit, and a control frame between the home-side apparatus and the switching destination optical line unit after the switching process is performed. And a communication control unit for performing a process of starting transmission of a data frame from the home-side device to the switching destination optical line unit after a period of transmitting / receiving.

  In this way, by confirming the synchronization state of the home side device and then starting transmission of the data frame from the switching destination optical line unit to the home side device, loss of communication traffic after the switching process can be prevented. it can. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  A station apparatus according to another aspect of the present invention includes a plurality of optical line units for transmitting / receiving control frames and data frames to / from one or a plurality of home-side apparatuses, and a standby system from the above-mentioned optical line units in the operating system. A switching control unit for performing switching processing to the optical line unit, and a state in which a control frame can be transmitted from the home side device which is a communication partner of the switching source optical line unit to the switching destination optical line unit. The transmission of the data frame from the home side device to the switching destination optical line unit is started after the condition for guaranteeing the synchronization between the home side device and the switching destination optical line unit is satisfied. And a communication control unit for performing processing.

  In this way, by confirming the synchronization state of the home side device and then starting transmission of the data frame from the switching destination optical line unit to the home side device, loss of communication traffic after the switching process can be prevented. it can. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  A station apparatus according to another aspect of the present invention includes a plurality of optical line units for transmitting / receiving control frames and data frames to / from one or a plurality of home-side apparatuses, and a standby system from the above-mentioned optical line units in the operating system. A switching control unit for performing switching processing to the optical line unit, and a communication control unit for performing processing for starting communication between the optical line unit and the home-side device, and the communication control unit includes: Data from the home-side device to the switch-destination optical line unit in a state in which a control frame can be transmitted from the home-side device that is a communication partner of the switch-source optical line unit to the switch-destination optical line unit After determining that the transmission of the frame is possible, the transmission of the data frame from the home-side device to the optical line unit at the switching destination is started. The process of performing.

  In this way, by confirming the synchronization state of the home side device and then starting transmission of the data frame from the switching destination optical line unit to the home side device, loss of communication traffic after the switching process can be prevented. it can. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  Preferably, the optical line unit receives a control frame and a data frame from each of the home side devices via a common communication line, and the control frame and the data frame from each of the home side devices to the optical line unit are sometimes received. Divided and multiplexed, the communication control unit performs a process of allocating a bandwidth in the communication line to the home side device, and the communication control unit transmits a data frame from the home side device to the switching destination optical line unit. As a process for starting the transmission, a process for allocating the band for transmitting the data frame to the home-side apparatus that is the communication partner of the switching destination optical line unit is started.

  With such a configuration, in a communication system in which frames from each home-side device to the station-side device are time-division multiplexed, the stability of the synchronization status of the home-side device can be confirmed with a simple process using existing bandwidth allocation. After that, transmission of the data frame from the switching destination optical line unit to the home device can be started.

  Preferably, the communication control unit receives a notification from the home side device that the home side device is synchronized with the switching destination optical line unit, and then the switching destination optical line from the home side device. A process for starting transmission of a data frame to the unit is performed.

  With such a configuration, it is possible to accurately determine that the synchronization state of the home device is stable.

  More preferably, the communication control unit inquires of the home side device whether or not the home side device is synchronized with the switching destination optical line unit.

  As described above, the configuration in which the station side apparatus confirms the synchronization state with respect to the home side apparatus can acquire information on whether or not the synchronization state of the home side apparatus has been stabilized earlier and more reliably.

  Preferably, the optical line unit receives a control frame and a data frame from each of the home side devices via a common communication line, and the control frame and the data frame from each of the home side devices to the optical line unit are sometimes received. The communication control unit performs a process of allocating the band to the home device based on a bandwidth allocation request in the communication line received from each home device, and the communication control unit When the allocation request is received a predetermined number of times from the home side device that is a communication partner of the switching destination optical line unit, the home side device starts a process of assigning the band for transmitting a data frame.

  With such a configuration, whether or not the synchronization state of the home side device is stabilized by a simple process using existing bandwidth allocation in a communication system in which frames from each home side device to the station side device are time-division multiplexed. Can be judged.

  A home-side apparatus according to another aspect of the present invention is a station-side apparatus including a plurality of optical line units, and performs a switching process from the active optical line unit to the standby optical line unit. In a state in which the above-mentioned switching process is performed and the control frame can be transmitted from the home-side device to the switching destination optical line unit, the communication unit for transmitting and receiving control frames and data frames with the side device. After a condition for guaranteeing synchronization between the home side device and the switching destination optical line unit is satisfied, transmission of a data frame from the home side device to the switching destination optical line unit is started. And a communication control unit for performing processing.

  In this way, by confirming the synchronization state of the home side device and then starting transmission of the data frame from the switching destination optical line unit to the home side device, loss of communication traffic after the switching process can be prevented. it can. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  A home-side apparatus according to another aspect of the present invention is a station-side apparatus including a plurality of optical line units, and performs a switching process from the active optical line unit to the standby optical line unit. In a state in which the above-mentioned switching process is performed and the control frame can be transmitted from the home-side device to the switching destination optical line unit, the communication unit for transmitting and receiving control frames and data frames with the side device. After determining that the data frame can be transmitted from the home side device to the switching destination optical line unit, the transmission of the data frame from the home side device to the switching destination optical line unit is started. And a communication control unit for performing processing.

  In this way, by confirming the synchronization state of the home side device and then starting transmission of the data frame from the switching destination optical line unit to the home side device, loss of communication traffic after the switching process can be prevented. it can. Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  Preferably, the home side device transmits a control frame and a data frame to the optical line unit by time division multiplexing via a common communication line with other home side devices, and the communication control unit is connected to the communication line. Processing for requesting the station side device to allocate its own bandwidth to the home side device, and the communication control unit starts transmitting a data frame from the home side device to the switching destination optical line unit As the processing to be performed, the self-side device starts processing to request the band for transmitting the data frame to the switching-destination optical line unit from the station-side device.

  With such a configuration, in a communication system in which frames from each home-side device to the station-side device are time-division multiplexed, after the synchronization state of the home-side device is stabilized by simple processing using existing bandwidth allocation The transmission of the data frame from the switching destination optical line unit to the home device can be started.

  ADVANTAGE OF THE INVENTION According to this invention, the loss | deletion of the communication data between the station side apparatus at the time of performing redundant switching of a station side apparatus and a home side apparatus can be prevented, and a highly reliable communication system can be provided.

It is a block diagram which shows schematic structure of the PON system which concerns on embodiment of this invention. It is a figure which shows the structure of OSU in the station side apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of ONU which concerns on embodiment of this invention. It is a figure which shows the structure of the reception clock recovery circuit in the synchronous process part which concerns on embodiment of this invention. It is a figure which shows the structure of the transmission clock recovery circuit in the synchronous process part which concerns on embodiment of this invention. It is a figure which shows an example of the band allocation process between a station side apparatus and ONU, and the flow of data in the PON system which concerns on embodiment of this invention. It is a figure which shows an example of the band allocation process between a station side apparatus and ONU, and the flow of data in the PON system which concerns on embodiment of this invention. 6 is a flowchart defining an example of an operation procedure for a switching destination OSU to start bandwidth allocation in the PON system according to the embodiment of the present invention. It is a figure which shows an example of the band allocation process between a station side apparatus and ONU, and the flow of data in the PON system which concerns on embodiment of this invention. It is a figure which shows an example of the band allocation process between a station side apparatus and ONU, and the flow of data in the PON system which concerns on embodiment of this invention. It is a figure which shows an example of the band allocation process between a station side apparatus and ONU, and the flow of data in the PON system which concerns on embodiment of this invention. 6 is a flowchart defining an example of an operation procedure for a switching destination OSU to start bandwidth allocation in the PON system according to the embodiment of the present invention. It is a figure which shows an example of the band allocation process between a station side apparatus and ONU, and the flow of data in the PON system which concerns on embodiment of this invention. 6 is a flowchart defining an example of an operation procedure for an ONU to start a bandwidth allocation request in the PON system according to the embodiment of the present invention. It is a figure which shows an example of the band allocation process between a station side apparatus and ONU, and the flow of data in the PON system which concerns on embodiment of this invention. It is a figure which shows an example of the band allocation process between a station side apparatus and ONU, and the flow of data in the PON system which concerns on embodiment of this invention. 6 is a flowchart defining an example of an operation procedure for an ONU to start a bandwidth allocation request in the PON system according to the embodiment of the present invention. It is the flowchart which defined an example of the operation | movement procedure in which the PON system which concerns on embodiment of this invention starts the band allocation between a station side apparatus and ONU.

  Hereinafter, embodiments 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.

[Configuration and basic operation]
FIG. 1 is a block diagram showing a schematic configuration of a PON system according to an embodiment of the present invention.

  Referring to FIG. 1, a PON system 301 includes a station-side device 101, N PON lines 1 to N (203-1 to 203-N), which are optical fibers, and N optical couplers 204-1 to 204-1. 204-N and a plurality of ONUs 202. The station-side apparatus 101 performs overall control of the optical line units (hereinafter also referred to as OSU (Optical Subscriber Unit)) 1 to N + 1 (12-1 to 12-N + 1), the optical switch 14, and the station-side apparatus 101. And an overall control unit (switching control unit) 11 that performs the operation. Here, N is an integer of 1 or more. In addition, a direction from the ONU to the upper network (hereinafter also referred to as “uplink”) is referred to as an uplink direction, and a direction from the uplink to the ONU is referred to as a downlink direction.

  Here, in the PON system 301, each PON line corresponds to 10G-EPON, which is an EPON that realizes a communication speed of 10 gigabits / second, and the uplink is Ethernet (registered) that realizes a communication speed of 10 gigabits / second. The description will be made on the assumption that it corresponds to the trademark. Further, description will be made on the assumption that ONU registration, withdrawal, bandwidth allocation to the ONU, and bandwidth request from the ONU are performed by the MPCP frame. The PON system 301 may be a GE-PON.

  The station apparatus 101 accommodates a plurality of PON lines corresponding to 10G-EPON. One or a plurality of ONUs are connected to one PON line. The station side apparatus 101 multiplexes data from these PON lines to an uplink having one or a plurality of communication lines. Further, the station side apparatus 101 distributes data from the uplink and transmits it to each ONU in each PON line. Further, the station apparatus 101 allocates the upstream band and downstream band of the PON line to each ONU. For example, the upstream optical signal from each ONU to the station apparatus 101 is a burst signal, and the downstream optical signal from the station apparatus 101 to each ONU is a continuous signal. In the PON system 301, an optical signal from each ONU 202 to the station apparatus 101 is time-division multiplexed.

  Specifically, the station apparatus 101 is connected to N PON lines 1 to N, and terminates the N PON lines. Each OSU is provided corresponding to a PON line, and transmits / receives a frame to / from one or more ONUs connected to a subordinate ONU, that is, a corresponding PON line. The PON lines 1 to N are connected to the optical couplers 204-1 to 204-N, respectively, and are connected to the respective ONUs 202 through these optical couplers.

  The station side device 101 has, for example, an N: 1 redundant configuration. That is, among N + 1 OSUs, OSU1 to N are active (current) OSUs, and OSU N + 1 is a standby (reserved) OSU. The station apparatus 101 may include two or more standby OSUs.

  The OSU 12 transmits and receives control frames and data frames, which are burst signals, to each of the subordinate ONUs 202. In the upstream direction, the OSU 12 receives a control frame and a data frame from each subordinate ONU 202 via a common PON line, and the control frame and the data frame from each ONU 202 to the OSU 12 are time-division multiplexed. That is, the ONU 202 transmits a control frame and a data frame to the OSU 12 by time division multiplexing via a common PON line together with other ONUs 202.

  The ONU 202 performs a reception recovery process for extracting a reception clock from the optical signal received from the station apparatus 101. The ONU 202 also generates a transmission clock that is synchronized with the reception clock extracted by the reception recovery process, and transmits data to be transmitted to the station side device 101 to the station side device 101 according to the timing of the generated transmission clock. Perform recovery processing.

  Further, the OSU 12 transmits a part or all of the uplink frame received from each ONU 202 to the uplink, and transmits a part or all of the downlink frame received from the uplink to each ONU 202.

  The overall control unit 11 performs a switching process for switching the OSU 12 that should transmit / receive a frame with the ONU 202 from the active OSU 12 to the standby OSU 12.

  In accordance with an instruction from the overall control unit 11, the optical switch 14 includes N + 1 OSU1 to N + 1 (12-1 to 12-N + 1) and N PON lines 1 to N (203-1 to 203-N). Switch between communication paths.

  FIG. 2 is a diagram showing the configuration of the OSU in the station side apparatus according to the embodiment of the present invention.

  Referring to FIG. 2, the OSU 12 includes an uplink 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, and a PON control unit (communication control). Part) 36, a FIFO 37 for accumulating upstream frames, a FIFO 38 for accumulating downstream frames, and a clock generator 39. It should be noted that a part or all of the operation of the PON control unit 36 described below may be performed by the overall control unit 11, or the PON control unit 36 itself may be provided outside the OSU 12.

  The clock generation unit 39 includes, for example, a VCO (Voltage Controlled Oscillator), and generates a clock for operating each unit in the OSU 12.

  That is, in the station apparatus 101, each of the plurality of OSUs 12 has a separate clock generation unit 39 for generating a clock. The OSU 12 generates time information, that is, a time stamp according to the timing of this clock, and transmits / receives a frame according to the time stamp. Further, the OSU 12 includes time information in a frame and transmits it to each subordinate ONU 202.

  The PON transmission / reception unit 35 is connected to one optical fiber, which is a PON line, via the optical switch 14 as a master station side starting point of the PON line. The PON transmission / reception unit 35 receives an upstream optical signal of a specific wavelength, for example, a 1310 nm band, and converts it into an electrical signal so as to enable bidirectional communication with each ONU via the optical fiber, and converts it to an electrical signal. In addition to outputting, the electrical signal received from the transmission processing unit 34 is converted into a downstream optical signal of another wavelength and transmitted. For example, the PON transmission / reception unit 35 converts a 10 Gbps electrical signal received from the transmission processing unit 34 into a downstream optical signal in the 1570 nm band and transmits the converted signal.

  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 PON control unit 36 or the FIFO 37 according to the type of the frame. Specifically, the data frame is output to the FIFO 37 and the control frame is output to the PON control unit 36.

  Further, the reception processing unit 33 may receive grant information indicating when to receive a frame from which logical link from the transmission processing unit 34 and output a control signal for supporting burst reception to the PON transmission / reception unit 35. Good. Further, the reception processing unit 33 may receive this grant information and filter, that is, discard, a received frame that is not indicated in the grant information.

  The uplink IF unit 31 transmits the uplink frame stored in the FIFO 37 to the uplink. Further, upon receiving a frame from the uplink, the uplink IF unit 31 outputs the frame to the FIFO 38 when the frame is a normal data frame, and outputs the frame to the PON control unit 36 when the frame is a control frame. To do.

  When receiving the control frame from the PON control unit 36, the uplink IF unit 31 outputs the control frame to the uplink in preference to the frame from the FIFO 37 between the frame sequences from the FIFO 37.

  When the FIFO 38 or the PON control unit 36 has a frame to be transmitted, the transmission processing unit 34 receives the frame according to the priority order and outputs it to the PON transmission / reception unit 35.

  The PON control unit 36 performs station-side processing related to control and management of the PON line such as MPCP and OAM. In other words, by exchanging MPCP messages and OAM messages with each ONU connected to the PON line, upstream access control including ONU registration, withdrawal and bandwidth allocation, downstream access control, ONU operation management, and the like are performed. .

  For example, the PON control unit 36 allocates the upstream bandwidth in the PON line to each ONU 202 based on the upstream bandwidth allocation request in the PON line received from each ONU 202. Specifically, the PON control unit 36 allocates a bandwidth in the PON line to the ONU 202 based on a report frame indicating a bandwidth allocation request in the PON line received from the ONU 202, that is, transmits a gate frame indicating a grant to the ONU 202. . The PON control unit 36 notifies the ONU 202 of the transmission start timing and the transmittable data length to the ONU 202 using the gate frame.

  The control IF unit 32 performs settings in the uplink IF unit 31, the reception processing unit 33, the transmission processing unit 34, the PON transmission / reception unit 35, and the PON control unit 36 based on instructions from the overall control unit 11. Notify the overall control unit 11 of the state of the unit. Further, when an abnormality occurs in each of these units, the state of the unit in which the abnormality has occurred is notified to the overall control unit 11 without depending on an instruction from the overall control unit 11. The overall control unit 11 may perform redundant switching of the OSU 12 based on such information, for example.

  FIG. 3 is a diagram showing the configuration of the ONU according to the embodiment of the present invention.

  Referring to FIG. 3, an ONU 202 includes an optical transceiver 21, a PON reception processing unit (communication unit) 22, a buffer memory 23, a UNI transmission processing unit 24, a UNI (User Network Interface) port 25, and a UNI reception. A processing unit 26, a buffer memory 27, a PON transmission processing unit (communication unit) 28, a control unit (communication control unit) 29, a lock determination circuit 43, and a lock counter 44 are provided. The PON reception processing unit 22 includes a reception clock recovery circuit (reception CDR (Clock and Data Recovery)) 41. The PON transmission processing unit 28 includes a transmission clock recovery circuit (transmission CDR) 42. The reception clock recovery circuit 41 and the transmission clock recovery circuit 42 constitute a synchronization processing unit 45.

  The PON reception processing unit 22 and the PON transmission processing unit 28 transmit and receive control frames and data frames to and from the station side device 101 via the optical transceiver 21.

  More specifically, the optical transceiver 21 converts a downstream optical signal transmitted from the station side device 101 into an electrical signal and outputs the electrical signal to the PON reception processing unit 22.

  The PON reception processing unit 22 receives an electrical signal from the optical transceiver 21, reconstructs a frame from the electrical signal, and distributes the frame to the control unit 29 or the UNI transmission processing unit 24 according to the type of the frame. Specifically, the PON reception processing unit 22 outputs the data frame to the UNI transmission processing unit 24 via the buffer memory 23 and outputs the control frame to the control unit 29.

  The UNI transmission processing unit 24 transmits the data frame received from the PON reception processing unit 22 to a user terminal such as a personal computer (not shown) via the UNI port 25.

  The UNI reception processing unit 26 outputs the data frame received from the user terminal via the UNI port 25 to the PON transmission processing unit 28 via the buffer memory 27.

  The control unit 29 performs home-side processing related to control and management of the PON line such as MPCP and OAM. That is, various controls such as access control are performed by exchanging MPCP messages and OAM messages with the station-side apparatus 101 connected to the PON line. The control unit 29 generates a control frame including various control information and outputs it to the PON transmission processing unit 28 via the buffer memory 27.

  The PON transmission processing unit 28 outputs the data frame received from the UNI reception processing unit 26 and the control frame received from the control unit 29 to the optical transceiver 21.

  The optical transceiver 21 converts the electrical signal received from the PON transmission processing unit 28 into an upstream optical signal and transmits it to the station apparatus 101.

  The synchronization processing unit 45 performs a synchronization process for synchronizing its own ONU 202 with the station apparatus 101. The synchronization processing unit 45 generates a reference timing signal, for example, a clock, for the own ONU 202 to operate in synchronization with the station apparatus 101 based on the downstream optical signal received from the station apparatus 101. Each unit in the ONU 202 operates according to the timing of the clock generated by the synchronization processing unit 45.

  More specifically, the reception clock recovery circuit 41 includes a PLL circuit, and extracts a reception clock from a signal received from the station side apparatus 101 using the PLL circuit.

  The transmission clock recovery circuit 42 includes a PLL circuit. Using the PLL circuit, the transmission clock recovery circuit 42 generates a transmission clock synchronized with the reception clock extracted by the reception clock recovery circuit 41, and transmits data to be transmitted to the station side device 101. Retime with the generated transmit clock.

  Specifically, the reception clock recovery circuit 41 generates a reception clock that is a reference timing signal based on the electrical signal received from the optical transceiver 21. The reception clock recovery circuit 41 samples the reception burst signal, which is an electrical signal received from the optical transceiver 21, using the reception clock, that is, samples and outputs the reception burst signal at the timing of the reception clock. The reception clock recovery circuit 41 outputs the reception clock to the transmission clock recovery circuit 42.

  The transmission clock recovery circuit 42 generates a transmission clock that is a reference timing signal based on the reception clock received from the reception clock recovery circuit 41. The transmission clock recovery circuit 42 retimes the data frame received from the UNI reception processing unit 26 and the control frame received from the control unit 29 using the transmission clock, that is, outputs the frame according to the timing of the transmission clock.

  For example, the lock determination circuit 43 receives the reception clock based on the phase difference signal indicating the phase comparison result in the PLL circuit of the reception clock recovery circuit 41 and the phase difference signal indicating the phase comparison result in the PLL circuit of the transmission clock recovery circuit 42. The locked state of the PLL circuit of the recovery circuit 41 and the locked state of the PLL circuit of the transmission clock recovery circuit 42 are monitored.

  The lock determination circuit 43 starts the counting operation of the lock counter 44 when the PLL circuit of the reception clock recovery circuit 41 and the PLL circuit of the transmission clock recovery circuit 42 are in a locked state. The lock determination circuit 43 stops the count operation of the lock counter 44 and resets the count value of the lock counter 44 when the PLL circuit of the reception clock recovery circuit 41 or the PLL circuit of the transmission clock recovery circuit 42 is unlocked. To do.

  Here, the locked state is, for example, a state in which the deviation between the frequency of the downstream optical signal from the station side device 101 and the frequency of the reception clock or the frequency of the transmission clock is smaller than a threshold, and from the station side device 101 This is a state in which the deviation between the phase of the downstream optical signal and the phase of the reception clock or the phase of the transmission clock is smaller than the threshold value. The unlocked state is a state not corresponding to the above.

  The control unit 29 refers to the count value of the lock counter 44. The lock determination circuit 43 can also notify the control unit 29 that the PLL circuit of the reception clock recovery circuit 41 is locked and that the PLL circuit of the transmission clock recovery circuit 42 is locked. is there.

  FIG. 4 is a diagram showing a configuration of a reception clock recovery circuit in the synchronization processing unit according to the embodiment of the present invention.

  Referring to FIG. 4, reception clock recovery circuit 41 includes a frequency divider circuit 54, a sampling circuit 55, a multiplier circuit 56, a frequency comparator 57, and a PLL circuit 58. The PLL circuit 58 includes a phase comparator 51, a charge pump & loop filter 52, and a VCXO (Voltage Controlled Crystal Oscillator) 53.

  The PLL circuit 58 controls the VCXO 53 based on the timing of the received burst signal received from the optical transceiver 21. More specifically, the PLL circuit 58 includes the VCXO 53, generates the control voltage VC based on the received burst signal received from the optical transceiver 21 and the reference clock generated in the ONU 202, and supplies the control voltage VC to the VCXO 53. As a result, the PLL circuit 58 generates a reception clock that has a frequency component in which a component equal to or higher than a predetermined frequency is attenuated among the frequency components of the reception burst signal received from the optical transceiver 21 and is synchronized with the reception burst signal. To do.

  Specifically, in PLL circuit 58, phase comparator 51 compares the phase of the received burst signal with the phase of the output signal of VCXO 53, and outputs a phase difference signal indicating the comparison result to charge pump & loop filter 52. .

  The followability of the PLL circuit 58 is set by the time constant of the charge pump & loop filter 52. Specifically, the time constant of the charge pump & loop filter 52 is set so that the PLL circuit 58 does not follow noise having high frequency components such as harmonics.

  The VCXO 53 generates and outputs an oscillation signal. The VCXO 53 receives the phase difference signal that has passed through the charge pump & loop filter 52 as the control voltage VC, and changes the frequency of the oscillation signal in accordance with the control voltage VC. The oscillation signal output from the VCXO 53 is output to the phase comparator 51 and the frequency dividing circuit 54.

  The frequency divider 54 divides the oscillation signal received from the VCXO 53 and outputs it as a reception clock.

  In response to the reception clock received from the frequency dividing circuit 54, the sampling circuit 55 holds the reception burst signal from the optical transceiver 21 and outputs it as reception data. The PON reception processing unit 22 reconstructs a frame from this received data.

  The multiplier 56 outputs a clock obtained by multiplying the reference clock generated in the ONU 202 by a predetermined number.

  The frequency comparator 57 compares the clock received from the multiplication circuit 56 with the reception clock received from the frequency dividing circuit 54 and outputs a frequency difference signal indicating the frequency difference between these clocks to the charge pump & loop filter 52.

  The control voltage VC is adjusted by the frequency difference signal output from the frequency comparator 57 to the charge pump & loop filter 52 so that the frequency of the reception clock matches the frequency of the clock output from the multiplication circuit 56.

  FIG. 5 is a diagram showing a configuration of a transmission clock recovery circuit in the synchronization processing unit according to the embodiment of the present invention.

  Referring to FIG. 5, transmission clock recovery circuit 42 includes a frequency divider circuit 64, a retiming circuit 65, a multiplier circuit 66, a frequency comparator 67, and a PLL circuit 68. The PLL circuit 68 includes a phase comparator 61, a charge pump & loop filter 62, and a VCXO 63.

  The PLL circuit 68 controls the VCXO 63 based on the timing of the reception clock received from the reception clock recovery circuit 41. More specifically, the PLL circuit 68 includes a VCXO 63, generates the control voltage VC based on the reception clock received from the reception clock recovery circuit 41 and the reference clock generated in the ONU 202, and supplies the control voltage VC to the VCXO 63. Thus, the PLL circuit 68 generates a transmission clock having a frequency component in which a component equal to or higher than a predetermined frequency is attenuated among the frequency components of the reception clock received from the reception clock recovery circuit 41 and synchronized with the reception clock. To do.

  Specifically, in the PLL circuit 68, the phase comparator 61 compares the phase of the received clock with the phase of the output signal of the VCXO 63 and outputs a phase difference signal indicating the comparison result to the charge pump & loop filter 62.

  The followability of the PLL circuit 68 is set by the time constant of the charge pump & loop filter 62. Specifically, the time constant of the charge pump & loop filter 62 is set so that the PLL circuit 68 does not follow noise having high frequency components such as harmonics.

  The VCXO 63 generates and outputs an oscillation signal. The VCXO 63 receives the phase difference signal that has passed through the charge pump & loop filter 62 as the control voltage VC, and changes the frequency of the oscillation signal in accordance with the control voltage VC. The oscillation signal output from the VCXO 63 is output to the phase comparator 61 and the frequency dividing circuit 64.

  The frequency dividing circuit 64 divides the oscillation signal received from the VCXO 63 and outputs it as a transmission clock.

  In response to the transmission clock received from the frequency dividing circuit 64, the retiming circuit 65 holds and outputs transmission data that is a data frame or a control frame from the buffer memory 27. The optical transceiver 21 converts the transmission data output from the retiming circuit 65 into an upstream optical signal and transmits it to the station apparatus 101.

  The multiplier circuit 66 outputs a clock obtained by multiplying the reference clock generated in the ONU 202 by a predetermined number.

  The frequency comparator 67 compares the clock received from the multiplier circuit 66 and the transmission clock received from the frequency divider circuit 64, and outputs a frequency difference signal indicating the frequency difference between these clocks to the charge pump & loop filter 62.

  The control voltage VC is adjusted by the frequency difference signal output from the frequency comparator 67 to the charge pump & loop filter 62 so that the frequency of the transmission clock matches the frequency of the clock output from the multiplier circuit 66.

  Here, the time constant T2 of the PLL circuit 68 of the transmission clock recovery circuit 42 is set to be larger than the time constant T1 of the PLL circuit 58 of the reception clock recovery circuit 41. For example, the time constant T1 is several tens of microseconds to several hundreds of microseconds, and the time constant T2 is several milliseconds to several tens of milliseconds.

  By setting the time constants T1 and T2 in this way, it is possible to increase the reception margin of the downstream optical signal from the station side apparatus 101 and to improve the frequency accuracy of the upstream optical signal to the station side apparatus 101.

  That is, the state of the synchronization processing unit 45 includes an unsynchronized state where the PLL circuit 58 of the reception clock recovery circuit 41 and the PLL circuit 68 of the transmission clock recovery circuit 42 are unlocked, and a PLL circuit 58 of the reception clock recovery circuit 41. Is in the locked state and the PLL circuit 68 of the transmission clock recovery circuit 42 is unlocked, and the PLL circuit 58 of the reception clock recovery circuit 41 and the PLL circuit 68 of the transmission clock recovery circuit 42 are in the locked state. There is a certain synchronization completion state. The state of the synchronization processing unit 45 transitions from the unsynchronized state to the synchronized completion state via the semi-synchronized state.

  FIG. 6 is a diagram showing an example of bandwidth allocation processing and data flow between the station-side device and the ONU in the PON system according to the embodiment of the present invention.

  Referring to FIG. 6, the OSU causes a registered ONU to transmit a report frame indicating a bandwidth request, and then causes the ONU that requested the bandwidth to transmit one or more data frames. The OSU instructs the ONU to send a report frame by creating one gate frame for each ONU and sending it to the ONU before sending the report frame to the ONU. Further, when the OSU causes the ONU to transmit a data frame, the OSU instructs the transmission of the report frame and the data frame with one gate frame. Thereafter, the OSU repeats these operations in a predetermined cycle, that is, a bandwidth allocation cycle.

  Here, consider the case where redundant switching of the OSU 12 in the station-side apparatus 101 (hereinafter also referred to as OSU redundant switching) occurs in the PON system 301.

  As described above, the time constant T1 of the PLL circuit 58 of the reception clock recovery circuit 41 is set to a value smaller than the time constant T2 of the PLL circuit 68 of the transmission clock recovery circuit 42.

  In this case, before the PLL circuit 68 of the transmission clock recovery circuit 42 is locked, the PLL circuit 58 of the reception clock recovery circuit 41 is locked. That is, before the PON transmission processing unit 28 synchronizes with the OSU 12, the PON reception processing unit 22 can synchronize with the OSU 12 and receive a downstream frame from the OSU 12.

  If the PON reception processing unit 22 receives a gate frame before the PON transmission processing unit 28 synchronizes with the OSU 12, the PON transmission processing unit 28 displays the report frame created by the control unit 29 before the OSU 12 synchronizes with the OSU 12. Send to.

  When receiving a report frame from the ONU 202, the OSU 12 transmits a gate frame to the ONU 202.

  Then, the ONU 202 transmits a data frame to the OSU 12 based on the gate frame received from the OSU 12.

  In such a case, the OSU 12 may not be able to receive a frame from the ONU 202. The reason is as follows, for example. That is, the OSU 12 determines the frequency and phase of the clock for receiving the burst signal using the head portion of the burst signal that is a frame from the ONU 202.

  When the PON transmission processing unit 28 in the ONU 202 transmits an upstream frame to the OSU 12 before synchronizing with the OSU 12, the frequency of the transmission clock in the ONU 202 may differ between the head portion and the tail portion of the burst signal.

  When the data length of a burst signal, such as a control frame, is relatively short, the OSU 12 may be able to receive the burst signal because the difference in frequency of the transmission clock is small between the beginning and end of the burst signal. high.

  On the other hand, when the data length of the burst signal, such as a data frame, is relatively long, the frequency shift of the transmission clock becomes large between the head portion and the tail portion of the burst signal. There is a high possibility that a reception error will occur and communication data will be lost.

  Therefore, the PON system according to the embodiment of the present invention solves the above problems by the following operation.

  That is, in the OSU 12, after the switching process from the active OSU 12 to the standby OSU 12 is performed, the PON control unit 36 passes through a period of transmitting and receiving control frames between the ONU 202 and the switching destination OSU. To start transmission of a data frame from to the switching destination OSU.

  More specifically, the PON control unit 36 has a condition for guaranteeing synchronization between the ONU 202 and the switching destination OSU in a state in which a control frame can be transmitted from the ONU 202 that is a communication partner of the switching source OSU to the switching destination OSU. After being satisfied, a process of starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed.

  In other words, the PON control unit 36 determines that the data frame can be transmitted from the ONU 202 to the switching destination OSU in a state where the control frame can be transmitted from the ONU 202 that is the communication partner of the switching source OSU to the switching destination OSU. After that, processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed.

  For example, the PON control unit 36 performs a process of allocating a band for transmitting a data frame to the ONU 202 that is a communication partner of the switching destination OSU, as a process of starting transmission of the data frame from the ONU 202 to the switching destination OSU. Start.

  Next, the operation when the PON system according to the embodiment of the present invention performs OSU redundancy switching and bandwidth allocation processing for the ONU will be described with reference to the drawings.

[Operation]
FIG. 7 is a diagram showing an example of bandwidth allocation processing and data flow between the station apparatus and the ONU in the PON system according to the embodiment of the present invention.

  Referring to FIG. 7, the switching destination OSU starts transmission of an MPCP frame after a predetermined time has elapsed after OSU redundancy switching. That is, in the OSU 12, the PON control unit 36 performs a process of starting transmission of a data frame from the ONU 202 to the switching destination OSU after a predetermined time has elapsed since the switching process from the active OSU 12 to the standby OSU 12 is performed. Do.

  More specifically, the switching destination OSU stops bandwidth allocation to the ONU 202 until the time Tw elapses after the OSU redundancy switching is performed, specifically, does not transmit a gate frame to the ONU 202. Here, the time Tw is, for example, a time corresponding to a plurality of band allocation periods.

  Next, the switching destination OSU starts bandwidth allocation to the ONU 202 when the time Tw elapses. That is, the switching destination OSU instructs the ONU 202 to transmit the report frame Ra by creating the gate frame Ga and transmitting it to the ONU 202.

  Next, based on the gate frame Ga received from the switching destination OSU, the ONU 202 transmits a report frame Ra indicating the data length of the frame desired to be transmitted to the switching destination OSU.

  Next, based on the report frame Ra received from the ONU 202, the switching destination OSU transmits to the ONU 202 a gate frame Gb indicating the data length of a frame that can be transmitted by the ONU 202.

  Next, based on the gate frame Gb received from the switching destination OSU, the ONU 202 transmits a report frame Rb indicating the data length of the frame that the ONU 202 wants to transmit to the switching destination OSU and responds to the data length indicated by the gate frame Gb. A predetermined amount of data frames are transmitted to the switching destination OSU.

  Thereafter, transmission / reception of a gate frame, a report frame, and a data frame is performed between the switching destination OSU and the ONU 202.

  FIG. 8 is a flowchart defining an example of an operation procedure for the switching destination OSU to start bandwidth allocation in the PON system according to the embodiment of the present invention.

  Referring to FIG. 8, first, when OSU redundancy switching occurs (YES in step S1), the switching destination OSU suspends the start of bandwidth allocation to the subordinate ONU 202 (step S2), and in the ONU 202, It is determined whether or not synchronization has been established (step S3).

  The switching destination OSU continues to hold the start of bandwidth allocation for the ONU 202 until it determines that synchronization with itself is established in the subordinate ONU 202 (NO in step S3) (step S2).

  On the other hand, if the switching destination OSU determines that synchronization with itself is established in the subordinate ONU 202 (YES in step S3), the switching destination OSU starts bandwidth allocation to the ONU 202 (step S4). For example, in the example shown in FIG. 7, the switching destination OSU determines that synchronization with itself is established in the subordinate ONU 202 when the time Tw has elapsed since the OSU redundancy switching was performed.

  FIG. 9 is a diagram showing an example of bandwidth allocation processing and data flow between the station-side device and the ONU in the PON system according to the embodiment of the present invention.

  Referring to FIG. 9, the switching destination OSU starts bandwidth allocation for a data frame after a predetermined time elapses after OSU redundancy switching. That is, in the OSU 12, the PON control unit 36 starts transmission of a data frame from the ONU 202 to the switching destination OSU after a predetermined time has elapsed since the switching processing from the active OSU 12 to the standby OSU 12 is performed. To do.

  More specifically, when OSU redundancy switching is performed, the switching destination OSU starts to allocate a bandwidth for a control frame to the ONU 202, while data for the ONU 202 is passed until time Tw elapses after the OSU redundancy switching is performed. Stop bandwidth allocation for frames. Here, the time Tw is, for example, a time corresponding to a plurality of band allocation periods.

  For example, the PON control unit 36 in the OSU 12 has a data band allocation permission flag. Then, the PON control unit 36 starts band allocation for data frames to the ONU 202 by enabling the data band allocation permission flag from invalid to valid.

  Specifically, for example, in the PON system according to the IEEE Std 802.3-2008 standard, the PON control unit 36 indicates that the grant number indicates 1 when the data band allocation permission flag is invalid, and the ForceReportFlag field is set as the grant. A gate frame whose valid and grant length indicates the data length of the report frame is transmitted to the ONU 202. That is, the PON control unit 36 allocates only the bandwidth necessary for the ONU 202 to transmit the report frame to the ONU 202.

  At this time, the ONU 202 transmits a report frame indicating the data length of the frame that the ONU 202 wants to transmit to the switching destination OSU based on the gate frame received from the switching destination OSU. The data frame is not transmitted to the switching destination OSU.

  Next, when the time Tw elapses after the OSU redundancy switching is performed, the switching destination OSU starts allocating data frames for the ONU 202. That is, the switching destination OSU transmits to the ONU 202 the gate frame Ga indicating the data length of the frame that can be transmitted by the ONU 202 based on the report frame received from the ONU 202 until the time Tw elapses.

  Next, based on the gate frame Ga received from the switching destination OSU, the ONU 202 transmits a report frame Ra indicating the data length of the frame that it wants to transmit to the switching destination OSU and responds to the data length indicated by the gate frame Ga. A predetermined amount of data frames are transmitted to the switching destination OSU.

  Thereafter, transmission / reception of a gate frame, a report frame, and a data frame is performed between the switching destination OSU and the ONU 202.

  FIG. 10 is a diagram showing an example of bandwidth allocation processing and data flow between the station-side device and the ONU in the PON system according to the embodiment of the present invention.

  In the OSU 12, when the PON control unit 36 acquires information indicating the completion of the synchronization processing in the ONU 202, the PON control unit 36 performs processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU.

  More specifically, after receiving a notification from the ONU 202 that the ONU 202 is synchronized with the switching destination OSU, the PON control unit 36 performs a process of starting transmission of a data frame from the ONU 202 to the switching destination OSU.

  For example, the PON control unit 36 inquires of the ONU 202 whether the ONU 202 is synchronized with the switching destination OSU.

  Specifically, referring to FIG. 10, the switching destination OSU determines the synchronization state of ONU 202 by transmitting / receiving a dedicated extended OAM frame to / from ONU 202 after OSU redundancy switching.

  More specifically, when OSU redundancy switching is performed, the switching destination OSU starts to allocate a bandwidth for a control frame to the ONU 202, while the ONU 202 determines that the data synchronization with the ONU 202 is stable. Stop bandwidth allocation for frames.

  At this time, the ONU 202 transmits a report frame indicating the data length of the frame that the ONU 202 wants to transmit to the switching destination OSU based on the gate frame received from the switching destination OSU. The data frame is not transmitted to the switching destination OSU.

  Here, for example, after receiving the report frame Ra for the gate frame Ga from the ONU 202, the switching destination OSU transmits the extended OAM frame F1 to the ONU 202 together with the gate frame Gb. Here, the extended OAM frame F 1 indicates a request for reporting the synchronization state of the ONU 202. The gate frame Gb indicates the total data length of the report frame and the extended OAM frame, for example.

  Next, the ONU 202 receives the report frame Gb and the extended OAM frame F1, and transmits the report frame Rb and the extended OAM frame F2 to the switching destination OSU. Here, it is assumed that the extended OAM frame F2 indicates that the synchronization processing of the ONU 202 has not been completed.

  Specifically, the control unit 29 in the ONU 202 refers to the count value of the lock counter 44 and switches the extended OAM frame indicating that the synchronization processing of the ONU 202 is not completed when the count value is less than a predetermined value. Transmit to the destination OSU.

  Next, the switching destination OSU receives the report frame Rb and the extended OAM frame F2, and transmits the gate frame Gc to the ONU 202. Here, the report frame Gc indicates, for example, the total data length of the report frame and the extended OAM frame.

  Next, the ONU 202 receives the report frame Gc and transmits the report frame Rc and the extended OAM frame F3 to the switching destination OSU. Here, it is assumed that the extended OAM frame F3 indicates that the synchronization processing of the ONU 202 has been completed.

  Specifically, the control unit 29 in the ONU 202 refers to the count value of the lock counter 44, and when the count value is equal to or greater than the predetermined value, switches the extended OAM frame indicating that the synchronization processing of the ONU 202 is completed. Send to OSU.

  Next, the switching destination OSU receives the report frame Rc and the extended OAM frame F3, and starts allocating a bandwidth for the data frame to the ONU 202. That is, based on the report frame Rc received from the ONU 202, the switching destination OSU transmits to the ONU 202 a gate frame Gd indicating the data length of a frame that can be transmitted by the ONU 202.

  Next, based on the gate frame Gd received from the switching destination OSU, the ONU 202 transmits a report frame Rd indicating the data length of the frame that it wants to transmit to the switching destination OSU and responds to the data length indicated by the gate frame Gd. A predetermined amount of data frames are transmitted to the switching destination OSU.

  Thereafter, transmission / reception of a gate frame, a report frame, and a data frame is performed between the switching destination OSU and the ONU 202.

  FIG. 11 is a diagram showing an example of bandwidth allocation processing and data flow between the station apparatus and the ONU in the PON system according to the embodiment of the present invention.

  When the PON control unit 36 receives a bandwidth allocation request from the ONU 202 serving as a communication partner of the switching destination OSU a predetermined number of times, the PON control unit 36 starts processing for allocating a bandwidth for the ONU 202 to transmit a data frame.

  Specifically, referring to FIG. 11, when the switching destination OSU receives a report frame from ONU 202 a predetermined number of times, it starts allocating bandwidth for the data frame.

  More specifically, when OSU redundancy switching is performed, the switching destination OSU starts to allocate the bandwidth for the control frame to the ONU 202, while the data for the ONU 202 is received until the report frame R is received from the ONU 202 a predetermined number of times, for example, three times. Stop bandwidth allocation for frames.

  At this time, based on the gate frame G received from the switching destination OSU, the ONU 202 transmits a report frame R indicating the data length of the frame that the ONU 202 desires to transmit to the switching destination OSU, but no data frame band is allocated. Therefore, the data frame is not transmitted to the switching destination OSU.

  Next, after the OSU redundancy switching is performed, the switching destination OSU receives the report frame R from the ONU 202 a predetermined number of times, for example, three times, and starts allocating data frames for the ONU 202. That is, the switching destination OSU transmits to the ONU 202 the gate frame Ga indicating the data length of a frame that can be transmitted by the ONU 202 based on the report frame R that has been received from the ONU 202.

  Next, based on the gate frame Ga received from the switching destination OSU, the ONU 202 transmits a report frame Ra indicating the data length of the frame that it wants to transmit to the switching destination OSU and responds to the data length indicated by the gate frame Ga. A predetermined amount of data frames are transmitted to the switching destination OSU.

  Thereafter, transmission / reception of a gate frame, a report frame, and a data frame is performed between the switching destination OSU and the ONU 202.

  In the example shown in FIG. 11, since the report frame can be reliably transmitted from the ONU 202 by using the aforementioned data band allocation permission flag, the data band allocation permission flag is more effective.

  FIG. 12 is a flowchart defining an example of an operation procedure for the switching destination OSU to start bandwidth allocation in the PON system according to the embodiment of the present invention.

  Referring to FIG. 12, first, when OSU redundancy switching occurs (YES in step S11), the switching destination OSU starts allocating bandwidth for a control frame to the subordinate ONU 202, while the data frame for the ONU 202 is The start of bandwidth allocation is suspended (step S12), and it is determined whether or not synchronization with itself is established in the ONU 202 (step S13).

  The switching destination OSU continues to hold the start of data frame bandwidth allocation for the ONU 202 until it determines that the subordinate ONU 202 has established synchronization with itself (NO in step S13).

  On the other hand, if the switching destination OSU determines that synchronization with itself is established in the subordinate ONU 202 (YES in step S13), the switching destination OSU starts allocating data frame bandwidth to the ONU 202 (step S14).

  For example, in the example illustrated in FIG. 9, the switching destination OSU determines that synchronization with itself is established in the subordinate ONU 202 when the time Tw has elapsed since the OSU redundancy switching was performed. In the example illustrated in FIG. 10, the switching destination OSU determines that synchronization with itself has been established in the ONU 202 by receiving the extended OAM frame indicating that the synchronization processing has been completed from the subordinate ONU 202. Further, in the example shown in FIG. 11, the switching destination OSU determines that synchronization with itself is established in the ONU 202 by receiving a predetermined number of report frames from the subordinate ONU 202 after the OSU redundancy switching is performed. .

  The operation shown in FIGS. 7 to 12 is an operation for ensuring synchronization between the OSU 12 and the ONU 202 on the station side apparatus 101 side. These may be partly or wholly combined as long as there is no contradiction in operation.

  On the other hand, the following operations shown in FIGS. 13 to 17 are operations for ensuring synchronization between the OSU 12 and the ONU 202 on the ONU 202 side. These may be combined partially or wholly as long as there is no contradiction in operation.

  That is, the PON system according to the embodiment of the present invention solves the above-described problems by the following operation.

  In the ONU 202, the control unit 29 performs the switching process of the OSU 12 in the station side device 101, and after the condition for guaranteeing the synchronization between the own ONU 202 and the switching destination OSU is satisfied, the switching unit OSU from the own ONU 202. A process for starting transmission of a data frame to is performed.

  In other words, the control unit 29 determines that the OSU 12 switching process is performed in the station side device 101 and that the data frame can be transmitted from the own ONU 202 to the switching destination OSU. A process for starting transmission of a data frame to is performed.

  For example, as a process for starting transmission of a data frame from the ONU 202 to the switching destination OSU, the control unit 29 performs a process for requesting the station-side apparatus 101 for a band for the own ONU 202 to transmit the data frame to the switching destination OSU. Start.

  FIG. 13 is a diagram showing an example of bandwidth allocation processing and data flow between the station apparatus and the ONU in the PON system according to the embodiment of the present invention.

  In the ONU 202, the control unit 29 suppresses the data length of the frame transmitted by the own ONU 202 in the semi-synchronized state to be shorter than the data length of the frame transmitted by the own ONU 202 in the synchronized completion state.

  That is, referring to FIG. 13, after synchronization with the switching destination OSU is established, ONU 202 starts a bandwidth allocation request for a data frame, that is, a report indicating a value that takes into account the data length of the data frame to be transmitted The frame is transmitted to the switching destination OSU.

  More specifically, when OSU redundancy switching is performed, the ONU 202 starts a control frame bandwidth allocation request to the switching destination OSU, while the data for the switching destination OSU is completed until synchronization processing with the switching destination OSU is completed. Stops bandwidth allocation requests for frames.

  Specifically, the control unit 29 in the ONU 202 refers to the count value of the lock counter 44 and does not start a data frame bandwidth allocation request when the count value is less than a predetermined value. This predetermined value is, for example, a value corresponding to 1522 bytes which is the maximum frame length of Ethernet (registered trademark).

  At this time, the ONU 202 transmits a report frame R indicating the data length of the report frame to the switching destination OSU based on the gate frame G received from the switching destination OSU, but does not request a bandwidth for the data frame. The data frame is not transmitted to the switching destination OSU.

  Next, when the synchronization processing with the switching destination OSU is completed, the ONU 202 starts a data frame bandwidth allocation request to the switching destination OSU. That is, the ONU 202 transmits a report frame Ra indicating a value including the data length of the data frame that the ONU 202 desires to transmit to the switching destination OSU.

  Specifically, the control unit 29 in the ONU 202 refers to the count value of the lock counter 44 and starts a data frame bandwidth allocation request when the count value is equal to or greater than the predetermined value.

  Next, based on the report frame Ra received from the ONU 202, the switching destination OSU transmits to the ONU 202 a gate frame Ga indicating the data length of a frame that can be transmitted by the ONU 202.

  Next, based on the gate frame Ga received from the switching destination OSU, the ONU 202 transmits a report frame Rb indicating a value including the data length of the data frame to be transmitted to the switching destination OSU and An amount of data frames corresponding to the indicated data length is transmitted to the switching destination OSU.

  Thereafter, transmission / reception of a gate frame, a report frame, and a data frame is performed between the switching destination OSU and the ONU 202.

  FIG. 14 is a flowchart defining an example of an operation procedure in which an ONU starts a bandwidth allocation request in the PON system according to the embodiment of the present invention.

  Referring to FIG. 14, first, after the OSU redundancy switching occurs (YES in step S21), ONU 202 allocates a control frame bandwidth to the switching destination OSU when reception recovery processing becomes possible (YES in step S22). While the request is started, the start of the data frame bandwidth allocation request for the switching destination OSU is suspended (step S23).

  Specifically, the control unit 29 in the ONU 202 recognizes whether or not the PLL circuit 58 of the reception clock recovery circuit 41 has changed from the unlocked state to the locked state based on the notification from the lock determination circuit 43.

  Next, the ONU 202 continues to hold the start of the data frame bandwidth allocation request for the switching destination OSU until the transmission recovery process becomes possible (NO in step S24).

  On the other hand, when the transmission recovery process is possible (YES in step S24), the ONU 202 starts a data frame bandwidth allocation request to the switching destination OSU (step S25).

  Specifically, the control unit 29 in the ONU 202 recognizes whether or not the PLL circuit 68 of the transmission clock recovery circuit 42 has changed from the unlocked state to the locked state based on the notification from the lock determination circuit 43.

  FIG. 15 is a diagram showing an example of bandwidth allocation processing and data flow between the station-side device and the ONU in the PON system according to the embodiment of the present invention.

  Referring to FIG. 15, after synchronization with the switching destination OSU is established, ONU 202 starts a bandwidth allocation request for control frames and data frames, that is, starts transmission of a report frame to switching destination OSU. .

  More specifically, after the OSU redundancy switching is performed, the ONU 202 holds the bandwidth allocation request for the switching destination OSU, specifically, does not transmit a report frame to the switching destination OSU.

  At this time, the ONU 202 receives the gate frame G from the switching destination OSU, but does not transmit the report frame and the data frame to the switching destination OSU.

  Next, when the synchronization process with the switching destination OSU is completed, the ONU 202 starts a bandwidth allocation request for the switching destination OSU. That is, the ONU 202 transmits a report frame Ra indicating the data length of the frame that it wants to transmit to the switching destination OSU.

  Next, based on the report frame Ra received from the ONU 202, the switching destination OSU transmits to the ONU 202 a gate frame Ga indicating the data length of a frame that can be transmitted by the ONU 202.

  Next, based on the gate frame Ga received from the switching destination OSU, the ONU 202 transmits a report frame Rb indicating the data length of the frame that it wants to transmit to the switching destination OSU and responds to the data length indicated by the gate frame Ga. A predetermined amount of data frames are transmitted to the switching destination OSU.

  Thereafter, transmission / reception of a gate frame, a report frame, and a data frame is performed between the switching destination OSU and the ONU 202.

  FIG. 16 is a diagram showing an example of bandwidth allocation processing and data flow between the station-side device and the ONU in the PON system according to the embodiment of the present invention.

  Referring to FIG. 16, when the ONU 202 receives a gate frame from the switching destination OSU a predetermined number of times, the ONU 202 starts a bandwidth allocation request for the control frame and the data frame, that is, transmits a report frame to the switching destination OSU. Start.

  More specifically, the ONU 202 holds a bandwidth allocation request for the switching destination OSU until the gate frame G is received from the switching destination OSU a predetermined number of times, for example, three times after the OSU redundancy switching is performed. The report frame is not transmitted to the switching destination OSU.

  At this time, the ONU 202 receives the gate frame G from the switching destination OSU, but does not transmit the report frame and the data frame to the switching destination OSU.

  Next, after the OSU redundancy switching is performed, the ONU 202 starts a bandwidth allocation request to the switching destination OSU when receiving the gate frame G from the switching destination OSU a predetermined number of times, for example, three times. That is, the ONU 202 transmits a report frame Ra indicating the data length of the frame that it wants to transmit to the switching destination OSU.

  Next, based on the report frame Ra received from the ONU 202, the switching destination OSU transmits to the ONU 202 a gate frame Ga indicating the data length of a frame that can be transmitted by the ONU 202.

  Next, based on the gate frame Ga received from the switching destination OSU, the ONU 202 transmits a report frame Rb indicating the data length of the frame that it wants to transmit to the switching destination OSU and responds to the data length indicated by the gate frame Ga. A predetermined amount of data frames are transmitted to the switching destination OSU.

  Thereafter, transmission / reception of a gate frame, a report frame, and a data frame is performed between the switching destination OSU and the ONU 202.

  FIG. 17 is a flowchart defining an example of an operation procedure in which an ONU starts a bandwidth allocation request in the PON system according to the embodiment of the present invention.

  Referring to FIG. 17, first, after the OSU redundancy switching has occurred (YES in step S31), the ONU 202 holds the start of the bandwidth allocation request for the switching destination OSU (step S32), and the ONU 202 determines itself with the switching destination OSU. It is determined whether synchronization has been established (step S33).

  The ONU 202 continues to hold the start of the bandwidth allocation request for the switching destination OSU until it is determined that the synchronization with the switching destination OSU has been established (NO in step S33).

  On the other hand, when the ONU 202 determines that synchronization with the switching destination OSU has been established (YES in step S33), the ONU 202 starts a bandwidth allocation request to the switching destination OSU (step S34).

  For example, in the example illustrated in FIG. 15, the ONU 202 refers to the count value of the lock counter 44 and determines that synchronization with the switching destination OSU has been established when the count value is equal to or greater than the predetermined value. In the example shown in FIG. 16, the ONU 202 determines that synchronization with the switching destination OSU has been established by receiving a gate frame from the switching destination OSU a predetermined number of times after the OSU redundancy switching has been performed.

  In the PON system according to the embodiment of the present invention, the overall control unit 11 in the station side device 101 performs the OSU 12 switching process, and the PON control unit 36 in the OSU 12 or the control unit 29 in the ONU 202 performs data on the PON line. Although it is configured to perform processing for starting transmission / reception of frames, the present invention is not limited to this. Instead of the station-side device 101 or the ONU 202, a device other than the station-side device 101 and the ONU 202 in the PON system 301 controls the station-side device 101 to perform redundant switching of the OSU 12, and transmits and receives data frames on the PON line. It may be configured to perform a process to allow.

  More specifically, the PON system 301 includes a switching control unit and a communication control unit. The switching control unit performs switching processing from the active OSU 12 to the standby OSU 12.

  In a state in which a control frame can be transmitted from the ONU 202, which is the communication partner of the switching source OSU, to the switching destination OSU, the communication control unit satisfies the condition for guaranteeing the synchronization between the ONU 202 and the switching destination OSU. Processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed.

  In other words, the communication control unit determines that the data frame can be transmitted from the ONU 202 to the switching destination OSU in a state where the control frame can be transmitted from the ONU 202 that is the communication partner of the switching source OSU to the switching destination OSU. Thereafter, processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed.

  FIG. 18 is a flowchart defining an example of an operation procedure in which the PON system according to the embodiment of the present invention starts band allocation between the station-side device and the ONU.

  Referring to FIG. 18, first, the switching control unit in the PON system 301 performs a switching process from the active OSU 12 to the standby OSU 12 (step S41).

  Next, after the communication control unit in the PON system 301 can perform the reception recovery process in the ONU 202 that is the communication partner of the switching source OSU 12 (YES in step S42), the ONU 202 switches to the switching destination OSU 12. The control frame is allowed to be transmitted, and the transmission permission of the data frame from the ONU 202 to the switching destination OSU 12 is suspended (step S43).

  Next, the communication control unit in the PON system 301 permits transmission of the suspended data frame after the ONU 202 that is the communication partner of the switching source OSU 12 can perform the transmission recovery process (YES in step S44). (Step S45).

  In the PON system according to the embodiment of the present invention, transmission / reception of a data frame that starts after determining or confirming the stability of the synchronization state of the ONU 202 is performed in both the upstream and downstream directions according to various conditions. The structure which makes it may be sufficient, and the structure made only to an up direction may be sufficient. For example, after the OSU redundancy switching is performed, the switching destination OSU may start transmission of the downlink data frame without waiting for the transition of the transmission clock recovery circuit 42 in the ONU 202 to the locked state of the PLL circuit 68.

  By the way, in the PON system, in order to communicate between the station side device and the ONU, the station side device and the ONU need to be synchronized.

  Specifically, for example, the ONU needs to be frequency-synchronized and phase-synchronized with the downstream optical signal from the station side device. Here, the frequency synchronization is to output the upstream optical signal according to the timing of the clock having the same frequency as the clock extracted from the downstream optical signal. The phase synchronization is to output the upstream optical signal according to the clock timing having the same phase as the clock extracted from the downstream optical signal.

  When the station-side apparatus includes a plurality of OSUs (Optical Subscriber Units) for transmitting and receiving optical signals to and from the ONU, in the redundant switching from the active OSU to the standby OSU, the ONU switches to the switching destination OSU. Need to synchronize anew. That is, in the redundant switching from the active OSU to the standby OSU, the ONU needs to newly synchronize with the downstream optical signal from the switching destination OSU.

  Even if the operating frequency between the active OSU and the standby OSU is the same, the optical path length between the OSU and the ONU is different, so that the downstream optical signal from the switching source OSU and the downstream from the switching destination OSU There is a phase shift in the optical signal. For this reason, a certain amount of time is required until the synchronization state with the switching destination OSU in the ONU is stabilized.

  As described above, a certain amount of time is required until the synchronization state of the ONU with the switching destination OSU is stabilized, and communication is started between the switching destination OSU and the ONU before the synchronization state of the ONU is stabilized. If this is done, communication data may be lost.

  On the other hand, in the PON system according to the embodiment of the present invention, the communication control unit and the ONU 202 and the switching destination in a state where the control frame can be transmitted from the ONU 202 that is the communication partner of the switching source OSU to the switching destination OSU. After a condition for guaranteeing synchronization with the OSU is satisfied, processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed. In other words, the communication control unit determines that the data frame can be transmitted from the ONU 202 to the switching destination OSU in a state where the control frame can be transmitted from the ONU 202 that is the communication partner of the switching source OSU to the switching destination OSU. Thereafter, processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed.

  In the PON system according to the embodiment of the present invention, first, switching processing from the active OSU 12 to the standby OSU 12 is performed. Next, after the ONU 202 that is the communication partner of the switching source OSU can perform the reception recovery processing, the control frame is permitted to be transmitted from the ONU 202 to the switching destination OSU, and from the ONU 202 to the switching destination OSU. The transmission permission of the data frame is suspended. Next, after the transmission recovery process can be performed in the ONU 202, transmission of the suspended data frame is permitted.

  In the station apparatus according to the embodiment of the present invention, the PON control unit 36 performs control between the ONU 202 and the switching destination OSU after the switching process from the active OSU 12 to the standby OSU 12 is performed. After a frame transmission / reception period, processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed. More specifically, in the station-side device according to the embodiment of the present invention, the PON control unit 36 transmits the control frame from the ONU 202 that is the communication partner of the switching source OSU to the switching destination OSU. After a condition for guaranteeing synchronization with the switching destination OSU is satisfied, a process for starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed. In other words, the PON control unit 36 determines that the data frame can be transmitted from the ONU 202 to the switching destination OSU in a state where the control frame can be transmitted from the ONU 202 that is the communication partner of the switching source OSU to the switching destination OSU. After that, processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU is performed.

  Further, in the ONU according to the embodiment of the present invention, the control unit 29 performs the switching process of the OSU 12 in the station side apparatus 101, and the condition for guaranteeing the synchronization between the own ONU 202 and the switching destination OSU is satisfied. After that, a process for starting transmission of a data frame from its own ONU 202 to the switching destination OSU is performed. In other words, the control unit 29 determines that the OSU 12 switching process is performed in the station side device 101 and that the data frame can be transmitted from the own ONU 202 to the switching destination OSU. A process for starting transmission of a data frame to is performed.

  That is, after redundancy switching, communication between the OSU 12 and the ONU 202 is started after ensuring that the ONU 202 is stably synchronized with the newly accommodated OSU 12.

  In this way, after the receiver and transmitter in the ONU 202 synchronize with the downstream optical signal of the switching destination OSU, that is, after confirming that the synchronization state of the ONU 202 is stable, transmission of the data frame from the switching destination OSU to the ONU 202 is performed. By starting the configuration, it is possible to prevent loss of communication traffic after OSU redundancy switching.

  Therefore, loss of communication data between the station side device and the home side device when performing redundant switching of the station side devices can be prevented, and a highly reliable communication system can be provided.

  In the PON system according to the embodiment of the present invention, the communication control unit switches from the ONU 202 to the switching destination OSU after a predetermined time has elapsed since the switching processing from the active OSU 12 to the standby OSU 12 is performed. Processing for starting transmission of a data frame is performed.

  With such a configuration, it can be determined by simple processing whether the synchronization state of the ONU 202 is stable.

  Further, in the PON system according to the embodiment of the present invention, the ONU 202 performs a synchronization process for synchronizing itself with the station side apparatus 101 using the signal received from the station side apparatus 101. When the communication control unit acquires information indicating the completion of the synchronization processing, the communication control unit performs processing for starting transmission of a data frame from the ONU 202 to the switching destination OSU.

  With such a configuration, it can be accurately determined that the synchronization state of the ONU 202 is stable.

  In the ONU according to the embodiment of the present invention, the synchronization processing unit 45 performs a synchronization process for synchronizing the ONU 202 with the station apparatus 101. The state of the synchronization processing unit 45 includes an unsynchronized state, a semi-synchronized state, and a synchronization completion state. Then, the control unit 29 suppresses the data length of the frame transmitted by the own ONU 202 in the semi-synchronized state to be shorter than the data length of the frame transmitted by the own ONU 202 in the synchronized completion state.

  As described above, the OSU redundancy switching is achieved by providing three states regarding the synchronization of the synchronization processing unit 45 in the ONU 202 and suppressing the data length of the frame transmitted to the station side device 101 according to the state transition of the synchronization processing unit 45. Thereafter, loss of communication traffic due to a transmission clock shift in the ONU 202 can be prevented.

Therefore, in the ONU according to the embodiment of the present invention, it is possible to prevent loss of communication data between the station side device and the home side device when performing redundant switching of the station side device, and to provide a highly reliable communication system. it can.
In the ONU according to the embodiment of the present invention, the state of the synchronization processing unit 45 transitions from the unsynchronized state to the synchronized completion state via the semi-synchronized state.
As described above, the data length of the frame to be transmitted to the station-side apparatus 101 is suppressed in the quasi-synchronization state that is the previous stage of the synchronization completion state. Defects can be prevented.

  In the ONU according to the embodiment of the present invention, in the synchronization processing unit 45, the reception clock recovery circuit 41 includes a PLL circuit 58, and a reception clock from a signal received from the station side device 101 using the PLL circuit 58. To extract. The transmission clock recovery circuit 42 includes a PLL circuit 68, generates a transmission clock that is synchronized with the reception clock extracted by the reception clock recovery circuit 41 using the PLL circuit 68, and transmits data to be transmitted to the station apparatus 101. Are retimed with the generated transmission clock. The time constant of the PLL circuit 68 in the transmission clock recovery circuit 42 is larger than the time constant of the PLL circuit 58 in the reception clock recovery circuit 41.

  With such a configuration, in particular, while increasing the reception margin of the downstream optical signal from the station side apparatus 101 and improving the frequency accuracy of the upstream optical signal to the station side apparatus 101, the transmission clock in the ONU 202 is switched after OSU redundancy switching. It is possible to prevent communication traffic from being lost due to the deviation.

  Further, in the station side apparatus according to the embodiment of the present invention, the PON control unit 36 performs a process of allocating the bandwidth in the PON line to the ONU 202. The PON control unit 36 starts a process of allocating a bandwidth for transmitting a data frame to the ONU 202 that is a communication partner of the switching destination OSU as a process of starting transmission of the data frame from the ONU 202 to the switching destination OSU. .

  With such a configuration, in a PON system in which frames from each ONU 202 to the station side device 101 are time-division multiplexed, after confirming the stability of the synchronization state of the ONU 202 with simple processing using existing bandwidth allocation, Data frame transmission from the switching destination OSU to the ONU 202 can be started.

  In the station apparatus according to the embodiment of the present invention, the PON control unit 36 receives a notification from the ONU 202 that the ONU 202 is synchronized with the switching destination OSU, and then transmits a data frame from the ONU 202 to the switching destination OSU. Processing to start transmission is performed.

  With such a configuration, it can be accurately determined that the synchronization state of the ONU 202 is stable.

  In the station apparatus according to the embodiment of the present invention, the PON control unit 36 inquires of the ONU 202 whether the ONU 202 is synchronized with the switching destination OSU.

  As described above, the station-side device 101 can acquire information on whether or not the synchronization state of the ONU 202 is stabilized earlier and more reliably by the configuration in which the station-side device 101 confirms the synchronization state with respect to the ONU 202.

  In the station apparatus according to the embodiment of the present invention, the PON control unit 36 performs a process of allocating a band to the ONU 202 based on a band allocation request on the PON line received from each ONU 202. When the PON control unit 36 receives an allocation request from the ONU 202 serving as a communication partner of the switching destination OSU a predetermined number of times, the PON control unit 36 starts a process of allocating a bandwidth for the ONU 202 to transmit a data frame.

  With such a configuration, in a PON system in which frames from each ONU 202 to the station-side apparatus 101 are time-division multiplexed, it is determined whether or not the synchronization state of the ONU 202 is stabilized by simple processing using existing bandwidth allocation. be able to.

  In the ONU according to the embodiment of the present invention, the control unit 29 performs a process of requesting the station side device 101 to allocate the bandwidth of the PON line to the ONU 202 itself. Then, the control unit 29 performs a process of requesting a bandwidth for the ONU 202 to transmit a data frame to the switching destination OSU from the station side apparatus 101 as a process of starting transmission of the data frame from the ONU 202 to the switching destination OSU. Start.

  With such a configuration, in a PON system in which frames from each ONU 202 to the station-side apparatus 101 are time-division multiplexed, the switching destination after the ONU 202 synchronization state is stabilized by simple processing using existing bandwidth allocation. Transmission of a data frame from the OSU to the ONU 202 can be started.

  The above description includes the following features.

[Appendix 1]
A plurality of optical line units for transmitting / receiving control frames and data frames to / from one or more home-side devices;
A switching control unit for performing switching processing from the optical line unit of the active system to the optical line unit of the standby system;
In a state in which a control frame can be transmitted from the home side device that is a communication partner of the switching source optical line unit to the switching destination optical line unit, synchronization between the home side device and the switching destination optical line unit is possible. A communication control unit for performing processing for starting transmission of a data frame from the home side device to the switching destination optical line unit after a condition for guaranteeing is satisfied.

[Appendix 2]
A plurality of optical line units for transmitting / receiving control frames and data frames to / from one or more home-side devices;
A switching control unit for performing switching processing from the optical line unit of the active system to the optical line unit of the standby system;
A communication control unit for performing processing for starting communication between the optical line unit and the home-side device;
The communication control unit is configured to transmit the control frame from the home side device to the switching destination optical line unit from the home side device that is a communication partner of the switching source optical line unit. A station apparatus that performs a process of starting transmission of a data frame from the home apparatus to the switching destination optical line unit after determining that transmission of a data frame to the optical line unit is possible.

[Appendix 3]
The optical line unit receives a control frame and a data frame from each home-side device via a common communication line, and the control frame and the data frame from each home-side device to the optical line unit are time-division multiplexed. ,
The communication control unit performs a process of allocating a bandwidth in the communication line to the home device,
The communication control unit is configured to start transmission of a data frame from the home side device to the switching destination optical line unit with respect to the home side device serving as a communication partner of the switching destination optical line unit. The station-side device according to Supplementary Note 1 or Supplementary Note 2, wherein processing for assigning the band for transmitting a data frame is started.

[Appendix 4]
The communication control unit receives a notification from the home side device that the home side device is synchronized with the switching destination optical line unit, and then transmits the notification from the home side device to the switching destination optical line unit. 4. The station-side device according to any one of appendix 1 to appendix 3, which performs a process of starting transmission of a data frame.

[Appendix 5]
The station side device according to appendix 4, wherein the communication control unit inquires of the home side device whether or not the home side device is synchronized with the switching destination optical line unit.

[Appendix 6]
The optical line unit receives a control frame and a data frame from each home-side device via a common communication line, and the control frame and the data frame from each home-side device to the optical line unit are time-division multiplexed. ,
The communication control unit performs a process of allocating the band to the home device based on a bandwidth allocation request in the communication line received from each home device,
When the communication control unit receives the allocation request from the home-side device that is a communication partner of the switching destination optical line unit a predetermined number of times, the home-side device allocates the band for transmitting the data frame The station-side device according to any one of appendix 1 to appendix 3, wherein

[Appendix 7]
A station-side device including a plurality of optical line units, for transmitting / receiving control frames and data frames to / from a station-side device that performs switching processing from the active optical line unit to the standby optical line unit A communication department;
In the state where the switching process is performed and the control frame can be transmitted from the home device to the switching destination optical line unit, synchronization between the home device and the switching optical line unit is guaranteed. And a communication control unit for performing processing for starting transmission of a data frame from the home device to the switching-destination optical line unit after a condition for the device is satisfied.

[Appendix 8]
A station-side device including a plurality of optical line units, for transmitting / receiving control frames and data frames to / from a station-side device that performs switching processing from the active optical line unit to the standby optical line unit A communication department;
Transmission of a data frame from the home device to the switching optical line unit in a state where the switching process is performed and a control frame can be transmitted from the home device to the switching optical line unit. And a communication control unit for performing processing for starting transmission of a data frame from the home device to the switching destination optical line unit after determining that the communication is possible.

[Appendix 9]
The home side device transmits a control frame and a data frame to the optical line unit by time division multiplexing via a common communication line with other home side devices,
The communication control unit performs a process of requesting the station side device to allocate the bandwidth of the communication line to the home side device,
The communication control unit is configured to start transmission of a data frame from the home side device to the switching destination optical line unit, and the home side device transmits a data frame to the switching destination optical line unit. The home apparatus according to appendix 7 or appendix 8, which starts processing for requesting the band for transmission to the station apparatus.

  The above embodiment 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.

11 Overall control unit (switching control unit)
12, 12-1 to 12-N + 1 OSU (optical line unit)
14 Optical switch 21 Optical transceiver 22 PON reception processing part (communication part)
23 buffer memory 24 UNI transmission processing unit 25 UNI port 26 UNI reception processing unit 27 buffer memory 28 PON transmission processing unit (communication unit)
29 Control unit (communication control unit)
31 uplink IF unit 32 control IF unit 33 reception processing unit 34 transmission processing unit 35 PON transmission / reception unit 36 PON control unit (communication control unit)
37,38 FIFO
39 Clock Generation Unit 41 Reception Clock Recovery Circuit 42 Transmission Clock Recovery Circuit 43 Lock Determination Circuit 44 Lock Counter 45 Synchronization Processing Unit 51, 61 Phase Comparator 52, 62 Charge Pump & Loop Filter 53, 63 VCXO
54, 64 Dividing circuit 55 Sampling circuit 65 Retiming circuit 56, 66 Multiplication circuit 57, 67 Frequency comparator 58, 68 PLL circuit 101 Station side device 202 ONU (home side device)
203-1 to 203-N PON line 204-1 to 204-N optical coupler 301 PON system

Claims (9)

A communication system comprising one or more home-side devices and a station-side device including a plurality of optical line units for transmitting and receiving control frames and data frames with the home-side devices,
A switching control unit for performing switching processing from the optical line unit of the active system to the optical line unit of the standby system;
In a state in which a control frame can be transmitted from the home side device that is a communication partner of the switching source optical line unit to the switching destination optical line unit, synchronization between the home side device and the switching destination optical line unit is possible. A communication control unit for performing a process of starting transmission of a data frame from the home side device to the switching destination optical line unit after a condition for guaranteeing is satisfied. A communication system comprising one or more home-side devices and a station-side device including a plurality of optical line units for transmitting and receiving control frames and data frames with the home-side devices,
A switching control unit for performing switching processing from the optical line unit of the active system to the optical line unit of the standby system;
Data from the home side device to the switching destination optical line unit in a state in which a control frame can be transmitted from the home side device that is a communication partner of the switching source optical line unit to the switching destination optical line unit A communication system comprising: a communication control unit for performing a process of starting transmission of a data frame from the home-side device to the switching destination optical line unit after determining that frame transmission is possible.   The communication control unit is configured to switch from the home device to the switching destination optical line unit after a predetermined time has elapsed since the switching process from the active optical line unit to the standby optical line unit is performed. The communication system according to claim 1, wherein processing for starting transmission of a data frame is performed. The home side device performs synchronization processing for synchronizing itself with the station side device using a signal received from the station side device,
The said communication control part will perform the process which starts transmission of the data frame from the said home side apparatus to the said optical line unit of the said switching destination, if the information which shows the completion of the said synchronous process is acquired. 2. The communication system according to 2. A home-side device for transmitting and receiving frames to and from a station-side device including a plurality of optical line units,
A synchronization processing unit for performing synchronization processing for synchronizing the home-side device with the station-side device;
The state of the synchronization processing unit includes an unsynchronized state, a semi-synchronized state, and a synchronization completion state.
The home device further includes:
A communication control unit configured to suppress a data length of the frame transmitted by the home side device in the semi-synchronized state to be shorter than a data length of the frame transmitted by the home side device in the synchronization completion state; Side device.   The home apparatus according to claim 5, wherein the state of the synchronization processing unit transitions from the unsynchronized state to the synchronized completion state via the semi-synchronized state. The synchronization processing unit
A reception clock recovery circuit for extracting a reception clock from a signal received from the station side device using the PLL circuit;
Including a PLL circuit, and using the PLL circuit to generate a transmission clock synchronized with the reception clock extracted by the reception clock recovery circuit, and to transmit data to be transmitted to the station side device using the generated transmission clock Including a transmission clock recovery circuit for retiming,
The home device according to claim 5 or 6, wherein a time constant of the PLL circuit in the transmission clock recovery circuit is larger than a time constant of the PLL circuit in the reception clock recovery circuit. A communication control method in a communication system comprising one or more home-side devices and a station-side device including a plurality of optical line units for transmitting and receiving control frames and data frames with the home-side devices,
The home side device performs a reception recovery process for extracting a reception clock from a signal received from the station side device, generates a transmission clock synchronized with the reception clock extracted by the reception recovery process, and the station side Perform transmission recovery processing to transmit data to be transmitted to the device to the station side device according to the timing of the generated transmission clock,
Performing a switching process from the optical line unit of the active system to the optical line unit of the standby system;
After the reception-recovery processing can be performed in the home-side device that is a communication partner of the switching-source optical line unit, the control frame is transmitted from the home-side device to the switching-destination optical line unit. Suspending permission to transmit the data frame from the home side device to the switching destination optical line unit;
Permitting transmission of the suspended data frame after the transmission recovery processing is enabled in the home-side apparatus that is a communication partner of the switching source optical line unit. . A plurality of optical line units for transmitting / receiving control frames and data frames to / from one or more home-side devices;
A switching control unit for performing switching processing from the optical line unit of the active system to the optical line unit of the standby system;
After the switching process is performed, data from the home side device to the switching destination optical line unit passes through a period in which a control frame is transmitted and received between the home side device and the switching destination optical line unit. A station-side apparatus comprising: a communication control unit for performing processing for starting transmission of a frame.

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