JP2011061479A - Optical communication system and optical communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical communication system and an optical communication method, for suppressing instantaneous interruption to be equal to or less than a failure rate allowed for traffic. <P>SOLUTION: The optical communication system is for sharing a time domain and a plurality of wavelength regions between a plurality of ONU-As (11-1-A) and one OLT (21-1), utilizing an optical splitter 12, and transmitting and receiving signal light. The OLT (21-1) monitors the communication state of the optical transmitters A-C (10-1-A to C) of the ONU-As (11-1-A), calculates the failure rate for each of the optical transmitters A-C (10-1-A to C), makes it possible to switch wavelengths to be allocated to the optical transmitters A-C (10-1-A to C) when the failure rate is lower than a predetermined fixed value, and suppresses the changeover of the wavelengths to be allocated to the optical transmitters A-C (10-1-A to C) when the failure rate is equal to or higher than the fixed value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a communication system in which a plurality of optical transmitters are allocated and accommodated in a plurality of groups, and more particularly to an optical communication system and an optical communication method using wavelength division multiplexing technology or core line multiplexing.

  PON (Passive Optical Network) is known as an optical network for realizing an economical high-speed access network. Assuming a low-cost SiGe-BiCMOS process, intensity modulation-direct detection, and time division multiplexing (TDM) similar to those conventionally used in access networks, PON is 10 Gbit / s due to restrictions on electronic devices. It is considered an upper limit.

  Therefore, in order to further increase the speed, a technique of applying wavelength division multiplexing (WDM) or core line (route) multiplexing to user multiplexing has been proposed. However, since the technology using wavelength division multiplexing uses different wavelengths for each user, it is necessary to renew the ONU (Optical Network Unit) which is a user side device, and assign and control the number of wavelengths for the number of users, and the station side Since an optical transmission terminal (20-1) corresponding to the number of users is required for an OLT (Optical Line Terminal), which is a device, a problem of cost increase occurs. Core wire multiplexing requires the light transmission / reception receiver (20-1) and the core wire by the amount corresponding to the core wire, which causes a problem of cost increase.

  In response to this problem, a WDM / TDM-PON system that divides ONUs into a plurality of groups, wavelength-division-multiplexes between groups, and time-division-multiplexes within the group as a total band expansion system that extends the total band that can be allocated to the entire user (For example, refer nonpatent literature 1.). This solves the problem of an increase in cost due to the expansion of the total bandwidth by sharing the wavelength among a plurality of ONUs.

  There is also a method of using a spare core wire for a redundant configuration as an active core wire (for example, see Non-Patent Document 2). This method solves the problem of an increase in cost due to the expansion of the total bandwidth by utilizing redundant core wires.

"A proposal for total bandwidth expansion WDM / TDM-PON and dynamic wavelength band allocation", Manabu Yoshino, Kazutaka Hara, Hirotaka Nakamura, Shunji Kimura, Naoto Yoshimoto, Kiyomi Kumozaki (Nippon Telegraph and Telephone Corporation, Access Service) System Research Laboratories), 2009 IEICE General Conference, Communication Lectures 2, 426 pages. "Examination of ATM-PON protection method and cooperative operation with dynamic bandwidth allocation", Toshikazu Yoshida, Hiroaki Mukai, Mitsuka Iwasaki, Yoshihiro Asashiba, Hiroshi Ichibanse, Tetsuya Yokoya, May 2001 CS System Study Group Electronic Information IEICE Technical Report vol. 101 (53): CS2001-21, pp. 25-30

  However, when switching the wavelength or core used by the ONU, the time required for switching may be longer than the interval between transmission frames. In the case of application data in which real-time property is regarded as important, such as telephone and TV broadcasting, there is a problem that reception is interrupted if the time required for switching is long. In the case of such traffic, for example, an operation rate of 99.999%, that is, a failure rate of 0.001% is required. Therefore, there has been a problem that the required operating rate cannot be satisfied if the number of instantaneous interruptions during switching increases.

  FIG. 6 shows an example of the failure rate in the conventional optical communication system. Before the time t1 when switching is performed, the failure rate of the optical communication system itself. Along with the switching, an instantaneous interruption that is considered as a failure occurs, and the apparent failure rate increases. The apparent failure rate increases with the passage of time after switching. If switching is repeated before the apparent failure rate after switching sufficiently decreases, the apparent failure rate gradually increases and eventually exceeds the allowable failure rate. In this way, when switching is performed without considering the failure rate, the apparent failure rate exceeds the allowable failure rate at time t4.

  In order to solve the above-described problems, an object of the present invention is to provide an optical communication system and an optical communication method that suppress instantaneous interruption below a failure rate allowed for traffic.

  In order to achieve the above object, the optical communication system and the optical communication method according to the present invention require a long time for switching, and when the communication is momentarily interrupted, the communication system is assumed from the failure rate allowed by the traffic. By suppressing switching so that the failure rate is less than the failure rate after subtracting the failure rate, it was decided to suppress quality degradation below the allowable failure rate.

  Specifically, the optical communication system according to the present invention shares a time domain and a plurality of wavelength domains between a plurality of optical subscriber-side apparatuses and a single station-side apparatus, and uses a passive optical branch circuit to transmit signal light. The station side device calculates the failure rate for each optical transmitter by monitoring the communication state of the optical transmitter of the subscriber side device, and the failure when switching is performed. If the rate is less than a predetermined value, it is possible to switch the wavelength allocated to the optical transmitter of the subscriber side device, and if the failure rate when switching is greater than or equal to the predetermined value, the subscriber It is an optical communication system which suppresses switching of the wavelength allocated to the optical transmitter of a side apparatus.

  Wavelength switching can be suppressed so that the failure rate does not exceed a certain value. Thereby, it is possible to provide an optical communication system and an optical communication method that suppress instantaneous interruption below a failure rate allowed for traffic.

  In the optical communication system according to the present invention, the station side device determines whether or not the optical transmitter of the subscriber side device is communicating, and a predetermined wavelength to be assigned to the optical transmitter of the subscriber side device. It is preferable to monitor the number of switching times during communication time or the communication interruption time per communication time, and calculate a failure rate due to wavelength switching during communication for each optical transmitter.

  Specifically, the optical communication system according to the present invention shares a time domain and a plurality of core line areas between a plurality of optical subscriber-side apparatuses and one station-side apparatus, and uses a passive optical branch circuit to transmit signal light. The station side device calculates the failure rate for each optical transmitter by monitoring the communication state of the optical transmitter of the subscriber side device, and the failure when switching is performed. If the rate is less than a predetermined value, it is possible to switch the core line assigned to the optical transmitter of the subscriber side device, and if the failure rate at the time of switching is equal to or greater than the certain value, the subscriber It is an optical communication system which suppresses switching of the core wire allocated to the optical transmitter of a side apparatus.

  Switching of the core wire can be suppressed so that the failure rate does not exceed a certain value. Thereby, it is possible to provide an optical communication system and an optical communication method that suppress instantaneous interruption below a failure rate allowed for traffic.

  In the optical communication system according to the present invention, the station side device determines whether or not the optical transmitter of the subscriber side device is in communication and a predetermined core line assigned to the optical transmitter of the subscriber side device. It is preferable to monitor the number of switching times in communication time or the communication interruption time per communication time, and calculate a failure rate due to switching of the core wire during communication for each optical transmitter.

  In the optical communication system according to the present invention, the predetermined constant value is a failure rate obtained by subtracting a failure rate assumed in the optical communication system from a failure rate allowed for the optical transmitter of the subscriber side device. It is preferable that

  Specifically, the optical communication method according to the present invention shares a time domain and a plurality of wavelength domains between a plurality of optical subscriber-side apparatuses and one station-side apparatus, and uses a passive optical branch circuit to transmit signal light. The station-side device calculates the failure rate for each optical transmitter by monitoring the communication state of the optical transmitter of the subscriber-side device and switches the failure. If the rate is less than a predetermined value, it is possible to switch the wavelength allocated to the optical transmitter of the subscriber side device, and if the failure rate when switching is greater than or equal to the predetermined value, the subscriber This is an optical communication method that suppresses switching of the wavelength allocated to the optical transmitter of the side device.

  Wavelength switching can be suppressed so that the failure rate does not exceed a certain value. Thereby, it is possible to provide an optical communication system and an optical communication method that suppress instantaneous interruption below a failure rate allowed for traffic.

  In the optical communication method according to the present invention, the station side device determines whether or not the optical transmitter of the subscriber side device is communicating and a predetermined wavelength to be assigned to the optical transmitter of the subscriber side device. It is preferable to monitor the number of switching times during communication time or the communication interruption time per communication time, and calculate a failure rate due to wavelength switching during communication for each optical transmitter.

  Specifically, the optical communication method according to the present invention shares a time domain and a plurality of core line areas between a plurality of optical subscriber-side apparatuses and a single station-side apparatus, and uses a passive optical branch circuit to transmit signal light. The station-side device calculates the failure rate for each optical transmitter by monitoring the communication state of the optical transmitter of the subscriber-side device and switches the failure. If the rate is less than a predetermined value, it is possible to switch the core line assigned to the optical transmitter of the subscriber side device, and if the failure rate at the time of switching is equal to or greater than the certain value, the subscriber This is an optical communication method that suppresses switching of the core wire assigned to the optical transmitter of the side device.

  Switching of the core wire can be suppressed so that the failure rate does not exceed a certain value. Thereby, it is possible to provide an optical communication system and an optical communication method that suppress instantaneous interruption below a failure rate allowed for traffic.

  In the optical communication method according to the present invention, the station side device determines whether or not the optical transmitter of the subscriber side device is communicating, and a predetermined core line assigned to the optical transmitter of the subscriber side device. It is preferable to monitor the number of switching times in communication time or the communication interruption time per communication time, and calculate a failure rate due to switching of the core wire during communication for each optical transmitter.

  In the optical communication method according to the present invention, the predetermined constant value is a failure rate obtained by subtracting a failure rate assumed in the optical communication system from a failure rate allowed for the optical transmitter of the subscriber side device. It is preferable that

  The above inventions can be combined as much as possible.

  According to the present invention, it is possible to provide an optical communication system and an optical communication method that suppress instantaneous interruption below a failure rate allowed for traffic.

1 is a schematic configuration diagram illustrating an example of an optical communication system according to the present embodiment. An example of a time chart of signal light from an optical transmitter at point X is shown. An example of the failure rate which concerns on this embodiment is shown. It is a conceptual diagram explaining the optical communication system of this embodiment. An example of a time chart of signal light from an optical transmitter at point X is shown. An example of failure rate in a conventional optical communication system

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 1 is a schematic configuration diagram illustrating an example of an optical communication system according to the present embodiment. The optical communication system according to the present embodiment includes ONU-A (11-1-A), ONU-B (11-1-B), and ONU-C (11-1-C) as a plurality of optical subscriber side devices. ), An OLT (21-1) as a station side device, and an optical splitter 12 as a passive optical branching circuit.

  The optical communication system according to the present embodiment shares the time domain and the plurality of wavelength domains between the ONU-A to C (11-1-A to C) and the OLT (21-1), and includes the optical splitter 12. Signal light is transmitted and received through the transmission path. The optical communication system is typically applied to a PON, for example, but a passive tree other than the PON can also be applied.

  The optical communication system according to the present embodiment includes a controller (not shown) and executes the optical communication method according to the present embodiment. The controller (not shown) monitors the communication state of the optical transmitters A to C (10-1-A to C) and determines the failure rate for each of the optical transmitters A to C (10-1-A to C). If the failure rate when calculated and switched is less than a predetermined value, switching of wavelengths allocated to the optical transmitters A to C (10-1-A to C) is enabled, and the failure when switched If the rate is equal to or higher than a certain value, switching of wavelengths allocated to the optical transmitters A to C (10-1-A to C) is suppressed. Hereinafter, the optical communication system and the optical communication method according to the present embodiment will be specifically described.

  The controller (not shown) is connected to a position where the communication states of the optical transmitters A to C (10-1-A to C) can be monitored. For example, it is connected to the optical transmission path between the optical splitter 12 and the OLT (21-1). A controller (not shown) is arrange | positioned at OLT (21-1), for example.

  The ONU-A (11-1-A) includes an optical transmitter A (10-1-A). The same applies to ONU-B (11-1-B) and ONU-C (11-1-C). The OLT (21-1) includes an optical multiplexer / demultiplexer (25), a light receiver a (22-1-a), and a light receiver b (22-1-b). The optical multiplexer / demultiplexer (25) is, for example, a wavelength filter. The light receivers a and b (22-1-a and b) are, for example, photodiodes. Here, the optical receiver (20-1) mounted on the ONU-A to C (11-1-A to C) and the optical transmitter mounted on the OLT (21-1) are omitted.

  ONU-A to C (11-1-A to C) are installed in the subscriber's house. The optical transmitters A to C (10-1-A to C) output signal light having an allocated wavelength. The assigned wavelength is one of a plurality of selectable wavelengths. The output signal light is transmitted through the optical fiber and is coupled by the optical splitter (12). The optical transmission line couples the signal light from the optical transmitters A to C (10-1-A to C) to the optical receiver (20-1) by wavelength division multiplexing and time division multiplexing. The optical multiplexer / demultiplexer (25) demultiplexes and outputs the signal light from the optical transmission path for each wavelength. The light receivers a and b (22-1-a, b) respectively receive the signal light from the optical multiplexer / demultiplexer (25). Accordingly, the optical receiver (20-1) receives the signal light from the optical transmitters A to C (10-1-A to C) for each of a plurality of wavelengths.

  A controller (not shown) assigns a wavelength and a time at which signal light can be transmitted to the optical transmitters A to C (10-1-A to C). For example, the optical transmitters A to C (10-1-A to C) output signal light at a predetermined one wavelength assigned from two wavelengths (λ1, λ2). In this way, the controller (not shown) assigns the wavelength and time to the optical transmitters A to C (10-1-A to C), whereby the allocated band is determined.

  The optical transmission line combines the signal light from the optical transmitters A to C (10-1-A to C) and couples it to the optical receiver (20-1). Here, signal lights of different wavelengths can be received simultaneously, but optical signals of the same wavelength cannot be received simultaneously. Therefore, the controller (not shown) can communicate with the optical transmitters A to C (10-1-A to C) so that signal light of the same wavelength does not reach the optical receiver (20-1) at the same time. You need to specify the time.

  FIG. 2 shows an example of a time chart of signal light from the optical transmitter at point X. In the transmission allocation, the vertical direction is a transmission wavelength region given to the optical transmitters A to C (10-1-A to C), and the horizontal direction is the optical transmitters A to C (10-1-A to C). Shows the assigned transmission time. The optical transmitter A (10-1-A) transmits the signal light having the wavelength λ1 in the allocation time region from the time t1 to the time t2, and transmits the signal light having the wavelength λ2 in the allocation time region from the time t2 + Δt to the time t3. Send. The optical transmitter B (10-1-B) transmits the signal light having the wavelength λ2 in the allocated time region from the time t1 to the time t2. The optical transmitter C (10-1-C) transmits the signal light having the wavelength λ1 in the allocated time region from time t2 to time t3. As described above, the optical communication system according to the present embodiment performs wavelength division multiplexing and time division multiplexing on the signal light from the optical transmitters A to C (10-1-A to C), and the optical receiver (20-1). ). As described above, the optical communication system according to the present embodiment performs wavelength division multiplexing and time division multiplexing on the signal light from the optical transmitters A to C (10-1-A to C), and the optical receiver (20-1). ).

  In this case, the controller (not shown) instructs the optical transmitter A (10-1-A) to output the signal light having the wavelength λ1 at time t1, and instructs the optical transmitter B (10-1-B). Instructs the optical transmitter C (10-1-C) to stop transmitting the signal light, and instructs the optical transmitter C (10-1-C) to stop transmitting the signal light. The controller (not shown) switches the wavelength to be transmitted to the optical transmitter A (10-1-A) at time t2, and instructs to output the signal light having the wavelength λ2 instead of the wavelength λ1. The optical transmitter B (10-1-B) is instructed to stop sending the signal light having the wavelength λ2, and the optical transmitter C (10-1-C) is instructed to send the signal light having the wavelength λ1. . In accordance with the wavelength switching instruction, the optical transmitter A (10-1-A) transmits the signal light having the wavelength λ2 after the time Δt required for switching has elapsed.

  Here, the time Δt required for switching may include a time required for a controller (not shown) to transmit an instruction to the optical transmitters A to C (10-1-A to C). Also, the controller (not shown) does not overlap when the transmission distances from the optical transmitters A to C (10-1-A to C) to the optical receiver (20-1) are different. Adjust the interval between the signal lights. When the signal light is composed of frames, a controller (not shown) adjusts the frame interval.

  In FIG. 1, three optical transmitters A to C (10-1-A to C) and two wavelengths are illustrated, but the number of optical transmitters A to C (10-1-A to C) is illustrated. The number of wavelengths to be wavelength-division multiplexed may be 3 or more. In FIG. 1, one optical receiver (20-1) receives a wavelength division multiplexed signal, but there may be a plurality of optical receivers (20-1). Further, the optical communication system may be a bidirectional communication system. As described above, in this optical communication system, a controller (not shown) assigns a wavelength and a time at which signal light can be transmitted to the optical transmitters A to C (10-1-A to C). In this way, the communication amount that can be communicated with the wavelength and time allocated to the optical transmitters A to C (10-1-A to C) by the controller (not shown) is the allocated band.

  A controller (not shown) monitors the communication state of the optical transmitters A to C (10-1-A to C). For example, the controller (not shown) monitors whether or not the optical transmitters A to C (10-1-A to C) are communicating, and the optical transmitters A to C (10-1-A). To C), the number of switching times in a predetermined communication time of the wavelength to be assigned to or the communication interruption time per communication time is monitored. At this time, the allowable failure rate of the optical transmitters A to C (10-1-A to C) is also monitored.

  For example, a controller (not shown) identifies the type of traffic to be transmitted and whether communication is in progress. The allowable failure rate of the traffic is determined from the traffic type. If the traffic type is an upstream traffic of GE-PON, the allowable failure rate of the traffic is determined from the data frame by the user priority bit (priority) of the LLID (Logical Link ID) and VLAN (Virtual Local Area Network) tag. Can be identified by reading. Further, if the traffic transmission is a type of traffic that starts and ends with a control frame such as SIP, the allowable failure rate of the traffic is determined according to the type of traffic using a control frame such as SIP (Session Initiation Protocol). Can be identified.

  Whether the number of frames of user priority bits of the same LLID or VLAN tag in a certain time is equal to or greater than a predetermined value or whether the frames of user priority bits of the same LLID or VLAN tag are in a certain time. Judgment can be made based on whether the data is stored in the buffer. If the traffic starts and ends with a control frame such as SIP, it can be determined that communication is in progress until the communication starts and ends.

  Note that the method using the frame continuity or the presence or absence of accumulation in the buffer starts from the viewpoint of dealing with equipment that does not transmit signal light during silent periods due to traffic such as telephone traffic. Alternatively, in order to reduce the possibility of misjudging whether communication is in progress due to a lack of a control frame such as SIP, which means termination, it is desirable to use them together.

  A controller (not shown) calculates a failure rate due to wavelength switching during communication for each of the optical transmitters A to C (10-1-A to C). For example, the controller (not shown) integrates the number of times of wavelength switching or the communication interruption time per communication time during a predetermined communication time during the communication of the traffic, and responds from the number of times in the past predetermined time and the communication interruption time. Calculate the failure rate. Then, it is determined whether or not the calculated failure rate exceeds a predetermined value. Switching is inhibited while the calculated failure rate exceeds a predetermined value. The suppression is canceled when the calculated failure rate falls below a predetermined value.

  When the failure rate calculated when a new switch is performed exceeds a predetermined value, the switching of the wavelength is suppressed. When the failure rate that can be calculated when switching is newly performed is below a predetermined value, it is desirable to cancel the suppression of wavelength switching.

  FIG. 3 shows an example of the failure rate according to the present embodiment. As time passes after switching, the apparent failure rate increases. However, if the next switching is performed during the time t4 after the switching of the time t2, the allowable failure rate is exceeded. In this case, the control unit suppresses wavelength switching. Even if the next switching is performed, the next switching is performed after time t4 when the apparent failure rate has decreased until the allowable failure rate is not exceeded (the switching is stopped once in this figure). For this reason, the apparent failure rate does not exceed the allowable failure rate.

  Here, the predetermined constant value is set according to the type of traffic. For example, the predetermined constant value is a failure obtained by subtracting a failure rate assumed in the optical communication system from a failure rate allowed for traffic transmitted by the optical transmitters A to C (10-1-A to C). Rate. The communication system is made redundant by wavelength, and when the assumed failure rate of the communication system is sufficiently low, the assumed failure rate of the communication system may not be subtracted from the failure rate allowed by traffic. In this case, when calculating the failure rate, it is not necessary to account for an apparent increase in failure rate due to switching when the traffic is not communicating.

  In some cases, the traffic is a video broadcast or the like, and channel switching can be identified. In this case, if the time required for channel switching when the wavelength is not switched is sufficiently longer than the time required for wavelength switching, an increase in the apparent failure rate due to wavelength switching during channel switching is not counted. Good. In the above description, the single optical transmitters A to C (10-1-A to C) communicate with only a single wavelength at the same time, but simultaneously communicate using a plurality of wavelengths. The same applies to

  As described above, the optical communication system according to this embodiment secures the quality required by traffic, and distributes and accommodates a plurality of users to a plurality of transmitters / receivers to expand the total bandwidth. A method can be provided.

(Embodiment 2)
FIG. 4 is a conceptual diagram illustrating the optical communication system of the present embodiment. The difference between the present optical communication system and the optical communication system of FIG. 1 is that each optical transmitter is distributed and accommodated in a plurality of core wires instead of being distributed and accommodated in a plurality of wavelengths.

  The optical communication system according to the present embodiment includes a controller (not shown) and executes the optical communication method according to the present embodiment. The controller (not shown) monitors the communication state of the optical transmitters A to C (10-2-A to C) and determines the failure rate for each of the optical transmitters A to C (10-2-A to C). If calculated and the failure rate is less than a predetermined value, the cores assigned to the optical transmitters A to C (10-2-A to C) can be switched. The switching of the core line assigned to the optical transmitters A to C (10-2-A to C) is suppressed. Hereinafter, the optical communication system and the optical communication method according to the present embodiment will be specifically described.

  The controller (not shown) is connected to a position where the communication states of the optical transmitters A to C (10-2-A to C) can be monitored. For example, it is connected to the optical transmission line between the optical splitter 12 and the OLT (21-2). A controller (not shown) is arrange | positioned at OLT (21-2), for example.

  The controller is the same if the wavelength in the first embodiment is read as the core wire. A controller allocates the core wire and time which can transmit signal light with respect to optical transmitter A-C (10-2-A-C). For example, the optical transmitters A to C (10-2-A to C) output signal light using a predetermined single core line assigned from the two core lines (H1, H2). As described above, the controller (not shown) assigns the core wire and time to the optical transmitters A to C (10-2-A to C), thereby determining the allocation band.

  The optical communication system includes optical transmitters A to C (10-2-A to C), a plurality of optical transmission lines, an optical receiver (20-2), and a controller (not shown). The optical transmitters A to C (10-2-A to C) are owned by each user, and output optical signals to one of the selectable core wires. The optical receiver (20-2) receives optical signals from the optical transmitters A to C (10-2-A to C) for each of the plurality of core wires. In the optical transmission line, optical signals from the optical transmitters A to C (10-2-A to C) are time-division multiplexed and coupled to the optical receiver (20-2) for each core wire.

  The controller is the same if the wavelength in the first embodiment is read as the core wire. The controller allocates a band to the optical transmitters A to C (10-2-A to C) by time division multiplexing for each core wire. For example, the optical transmitters A to C (10-2-A to C) output signal light using a predetermined single core line assigned from the two core lines (H1, H2). The optical transmitter A (10-2-A) transmits the signal light in the transmittable area through the core wire H1. The optical transmitter B (10-2-B) transmits the signal light of the core wire H1 in the transmittable area. The optical transmitter C (10-2-C) transmits the signal light of the core wire H2 in the transmittable area.

  The optical transmission path couples signal light from the optical transmitters A to C (10-2-A to C) to the optical receiver (20-2), respectively. Here, although signal light of different core wires can be received simultaneously, optical signals of the same core wire cannot be received simultaneously. Therefore, the controller designates the communicable time to the optical transmitters A to C (10-2-A to C) so that the signal light of the same core wire does not reach the optical receiver (20-2) at the same time. There is a need.

  FIG. 5 shows an example of a time chart of signal light from the optical transmitter at point X. The horizontal axis is time, and the vertical axis is the core or band. The controller instructs the optical transmitter A to output the signal light of the core wire H1 at the time t1, instructs the optical transmitter B to output the signal light of the core wire H2, and outputs the signal light to the optical transmitter C. To stop sending. The controller switches the core wire to be transmitted to the optical transmitter A at time t2, instructs the optical transmitter B to output the signal light of the core wire H2 instead of the core wire H1, and transmits the signal light of the core wire H2 to the optical transmitter B. Instructs the transmission to stop, and instructs the optical transmitter C to transmit the signal light of the core wire H1. In accordance with the instruction for switching the core wire, the optical transmitter A transmits the signal light of the core wire H2 after the time Δt required for switching has elapsed. As described above, the optical communication system shown in FIG. 4 is an optical receiver (20-2) in which signal light from the optical transmitters A to C (10-2-A to C) is subjected to core line multiplexing and time division multiplexing. To join.

  Here, the time Δt required for switching is determined by the controller from the controller to the device that changes the core wire in the case where the controller is away from the optical transmitter in this embodiment. The time required to transmit the instruction may be included. Further, when the transmission distances from the optical transmitters A to C (10-2-A to C) to the optical receiver (20-2) are different, the controller is configured to prevent the signal lights from overlapping. Adjust the interval. When the signal light is composed of frames, the controller adjusts the frame interval.

  The optical receiver (20-2) includes a plurality of light receivers a and b that receive light from the optical transmission path for each core wire. The light receivers a and b are, for example, photodiodes. The light receivers a and b each output the received signal light as an electrical signal.

  In FIG. 4, three optical transmitters and two core wires are illustrated, but the number of optical transmitters may be increased or decreased, and the number of core wires to be multiplexed may be three or more. In FIG. 3, the two optical receivers (20-2) side receive the signal multiplexed by the core wire, but a plurality of optical receivers (20-2) may be provided. Further, the optical communication system may be a bidirectional communication system.

  As described above, in the present optical communication system, the controller assigns a core line and time for transmitting signal light to the optical transmitters A to C (10-2-A to C). In this way, the amount of communication that can be communicated in time with the core assigned by the controller to the optical transmitter is the assigned bandwidth.

  A controller (not shown) monitors the communication state of the optical transmitters A to C (10-2-A to C). For example, the controller (not shown) monitors whether or not the optical transmitters A to C (10-2-A to C) are communicating, and the optical transmitters A to C (10-2-A). To C), the number of switching times of the core wires allocated to the predetermined communication time or the communication interruption time per communication time is monitored. At this time, the allowable failure rate of the optical transmitters A to C (10-2-A to C) is also monitored. Specific examples are the same as those in the first embodiment.

  A controller (not shown) calculates a failure rate due to switching of the core wire during communication for each of the optical transmitters A to C (10-2-A to C). For example, the controller (not shown) accumulates the number of core switching times or the communication interruption time per communication time during a predetermined communication time during the traffic communication, and responds from the number of times or communication interruption time in the past predetermined time. Calculate the failure rate. Then, it is determined whether or not the calculated failure rate exceeds a predetermined value. Switching is inhibited while the calculated failure rate exceeds a predetermined value. The suppression is canceled when the calculated failure rate falls below a predetermined value.

  When the failure rate calculated when switching is newly performed exceeds a predetermined value, switching of the core is suppressed. When the failure rate that can be calculated when a new switching is performed is below a predetermined value, it is desirable to cancel the suppression of the core switching.

  In some cases, the traffic is a video broadcast or the like, and channel switching can be identified. In this case, if the time required for channel switching when the core is not switched is sufficiently longer than the time required for core switching, an increase in the apparent failure rate due to core switching during channel switching is not counted. Good.

  In some cases, the traffic is a video broadcast or the like, and channel switching can be identified. In this case, if the time required for channel switching when the core is not switched is sufficiently longer than the time required for core switching, an increase in the apparent failure rate due to core switching during channel switching is not counted. Good.

  As described above, the optical communication system according to this embodiment secures the quality required by traffic, and distributes and accommodates a plurality of users to a plurality of transmitters / receivers to expand the total bandwidth. A method can be provided.

  In the above description, the single optical transmitters A to C (10-1-A to C) have been described as examples in which communication is performed using only a single core wire at the same time, but communication is performed using a plurality of core wires at the same time. The same applies to the case where the first embodiment of the present invention is combined with the present embodiment. When assigning, considering the difference in ONU-OLT distance difference, chromatic dispersion, and the difference in transmission time due to the distance difference between the plurality of core wires, the transmission time of the transmitter in the case where simultaneous transmission is not possible, When the signals cannot be received simultaneously, the arrival times of the signals arriving at the receiver are assigned so as not to overlap each other.

  The present invention can be applied to the information communication industry.

10-1-A to C, 10-2-A to C: Optical transmitters A to C
11-1-A to C, 11-2-A to C: ONU-A to C
12: Optical splitters 20-1, 20-2: Optical receivers 21-1, 21-2: OLT
22-1-a, b, 22-2-a, b: light receivers a, b
25: Optical multiplexer / demultiplexer

Claims (10)

An optical communication system that shares a time domain and a plurality of wavelength domains between a plurality of optical subscriber-side devices and a single station-side device, and transmits and receives signal light using a passive optical branch circuit,
The station side device
Monitor the communication state of the optical transmitter of the subscriber side device to calculate the failure rate for each optical transmitter,
If the failure rate when switching is less than a predetermined value, it is possible to switch the wavelength allocated to the optical transmitter of the subscriber side device,
An optical communication system that suppresses switching of the wavelength allocated to the optical transmitter of the subscriber side device when the failure rate when switching is equal to or greater than the predetermined value. The station side device
Monitor whether or not the optical transmitter of the subscriber side device is communicating, and the number of switching of the wavelength allocated to the optical transmitter of the subscriber side device in a predetermined communication time or the communication interruption time per communication time And
The optical communication system according to claim 1, wherein a failure rate due to wavelength switching during communication is calculated for each optical transmitter. An optical communication system that shares a time domain and a plurality of core line areas between a plurality of optical subscriber side apparatuses and one station side apparatus, and transmits / receives signal light using a passive optical branch circuit,
The station side device
Monitor the communication state of the optical transmitter of the subscriber side device to calculate the failure rate for each optical transmitter,
If the failure rate at the time of switching is less than a predetermined value, it is possible to switch the core assigned to the optical transmitter of the subscriber side device,
An optical communication system that suppresses switching of a core line allocated to an optical transmitter of the subscriber side device if the failure rate when switched is equal to or greater than the predetermined value. The station side device
Monitor whether or not the optical transmitter of the subscriber side device is communicating, and the number of switching of the core wire assigned to the optical transmitter of the subscriber side device in a predetermined communication time or communication interruption time per communication time And
The optical communication system according to claim 3, wherein a failure rate due to switching of the core wire during communication is calculated for each optical transmitter. The predetermined constant value is
5. The failure rate according to claim 1, wherein a failure rate is obtained by subtracting a failure rate assumed in the optical communication system from a failure rate allowed for the optical transmitter of the subscriber side device. Optical communication system. An optical communication method for sharing a time domain and a plurality of wavelength domains between a plurality of optical subscriber side apparatuses and a single station side apparatus, and transmitting and receiving signal light using a passive optical branch circuit,
The station side device
Monitor the communication state of the optical transmitter of the subscriber side device to calculate the failure rate for each optical transmitter,
If the failure rate when switching is less than a predetermined value, it is possible to switch the wavelength allocated to the optical transmitter of the subscriber side device,
An optical communication method for suppressing switching of a wavelength allocated to an optical transmitter of the subscriber side device when the failure rate when switching is equal to or greater than the predetermined value. The station side device
Monitor whether or not the optical transmitter of the subscriber side device is communicating, and the number of switching of the wavelength allocated to the optical transmitter of the subscriber side device in a predetermined communication time or the communication interruption time per communication time And
The optical communication method according to claim 6, wherein a failure rate due to wavelength switching during communication is calculated for each optical transmitter. An optical communication method in which a time domain and a plurality of core areas are shared between a plurality of optical subscriber side apparatuses and one station side apparatus, and signal light is transmitted and received using a passive optical branch circuit,
The station side device
Monitor the communication state of the optical transmitter of the subscriber side device to calculate the failure rate for each optical transmitter,
If the failure rate at the time of switching is less than a predetermined value, it is possible to switch the core assigned to the optical transmitter of the subscriber side device,
An optical communication method for suppressing switching of a core line assigned to an optical transmitter of the subscriber side device when the failure rate when switching is equal to or greater than the predetermined value. The station side device
Monitor whether or not the optical transmitter of the subscriber side device is communicating, and the number of switching of the core wire assigned to the optical transmitter of the subscriber side device in a predetermined communication time or communication interruption time per communication time And
The optical communication method according to claim 8, wherein a failure rate due to switching of the core wire during communication is calculated for each of the optical transmitters. The predetermined constant value is
The failure rate obtained by subtracting the failure rate assumed in the optical communication system from the failure rate allowed for the optical transmitter of the subscriber side device. Optical communication method.

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