Relay device, optical access system, and relay method

Abstract

Provided is a relay device for performing relaying between a plurality of optical communication devices that communicate using at least time-division multiplexing, the relay device comprising: a data length acquisition unit that, using an upstream signal transmitted from an optical communication device, acquires information pertaining to the data length of the upstream signal; a management control signal generation unit that generates a management control signal used for the purpose of management and control; a management control signal division unit that divides the generated management control signal on the basis of the information pertaining to the data length of the upstream signal as acquired by the data length acquisition unit; and a management control signal superimposition unit that superimposes the divided management control signals onto the upstream signal and transfers the management control signals to the other optical communication devices.　

Description

[Technical field]

[0001] The present invention relates to a relay device, an optical access system, and a relay method. [Background technology]

[0002] Fiber To The Home (FTTH) is becoming more and more popular worldwide, and the majority of FTTH is provided using the cost-effective Time Division Multiplexing-Passive Optical Network (TDM-PON) system. In the TDM-PON system, one Optical Line Terminal (OLT) accommodates multiple Optical Network Units (ONUs) using time division multiplexing (TDM).

[0003] Fig. 10 shows the configuration of a conventional TDM-PON system. As shown in Fig. 10, the conventional TDM-PON system 500 includes one OLT 510 and multiple ONUs 520. The OLT 510 and the multiple ONUs 520 are connected to one or more optical splitters 530, 540, 550 by optical fibers. Fig. 10 shows a configuration in which the optical splitter 530 is connected to the OLT 510 by optical fibers, the optical splitters 540 and 550 are connected to the optical splitter 530 by optical fibers, and two ONUs 520 are connected to each of the optical splitters 540 and 550 by optical fibers. The multiple ONUs 520 transmit data at transmission timings assigned by the OLT 510.

[0004] The OLT 510 includes an optical multiplexing / demultiplexing unit 511, an optical transmitting unit 512, an optical receiving unit 513, and a media access control unit 514. The optical multiplexing / demultiplexing unit 511 separates an upstream signal from a downstream signal. The optical transmitting unit 512 converts the data of an electrical signal to be transmitted into an optical signal. The optical receiving unit 513 converts the optical signal output from the optical multiplexing / demultiplexing unit 511 into an electrical signal. The media access control unit 514 schedules the transmission amount and transmission timing for each ONU 520 and generates a gate frame in order to share an optical fiber among multiple ONUs 520. The optical transmitting unit 512 transmits the generated gate frame to the ONU 520.

[0005] The ONU 520 includes an optical multiplexing / demultiplexing unit 521, an optical transmitting unit 522, an optical receiving unit 523, and a media access control unit 524. The optical multiplexing / demultiplexing unit 521 separates an upstream signal from a downstream signal. The optical transmitting unit 522 converts the data of the electrical signal to be transmitted into an optical signal. The optical receiving unit 523 converts the optical signal output from the optical multiplexing / demultiplexing unit 521 into an electrical signal. The media access control unit 524 processes the gate frame transmitted from the OLT 510 and generates a report frame for requesting a bandwidth from the OLT 510. The ONU 520 determines the transmission timing of the data from the transmission timing information included in the gate frame, and transmits the data at the assigned transmission timing.

[0006] Meanwhile, the ITU-T (International Telecommunication Union Telecommunication Standardization sector) G.989.2 recommendation specifies a PON system that performs wavelength multiplexing, called PtP WDM-PON (Point to Point Wavelength Division Multiplexing-PON) (see, for example, Non-Patent Document 1). In the PtP WDM-PON system, communication is performed using different wavelengths for each ONU in the upstream direction from the ONU to the OLT and the downstream direction from the OLT to the ONU.

[0007] As described in Non-Patent Document 1, in the PtP WDM-PON system, a management and control signal called AMCC (Auxiliary Management and Control Channel) is used as a signal for management and control used between the OLT and the ONU. The AMCC signal is a signal in which information to be transmitted is modulated in a predetermined manner and then superimposed on a main signal and transmitted. By superimposing the AMCC signal on the main signal and transmitting it, the ONU can transmit a signal for management and control within the wavelength range of the wavelength used by the main signal. In other words, management and control can be realized without using a wavelength range dedicated for management and control. When the AMCC signal is used for management and control, the wavelength determination process in which the upstream wavelength and downstream wavelength are determined in the PtP WDM-PON system is performed using the AMCC signal.

[0008] According to Non-Patent Document 1, there are two methods for superimposing an AMCC signal. The first method, "baseband modulation," is a method in which an AMCC signal is superimposed on a main signal as a baseband signal on the transmitter (e.g., ONU) side. In the "baseband modulation" superimposition method, the AMCC signal is separated by a filter such as a low-pass filter (LPF) on the receiver (e.g., OLT) side. The second method, "low-frequency pilot tone," involves up-converting the AMCC signal to a certain carrier frequency at the transmitter and superimposing it onto the main signal. With the "low-frequency pilot tone" superimposition method, the AMCC signal is obtained by demodulating it using signal processing at the receiver.

[0009] FIG. 11 shows the configuration of a PtP WDM-PON system using "low-frequency pilot tone". As shown in FIG. 11, a conventional PtP WDM-PON system 600 includes a plurality of OLTs 610 and a plurality of ONUs 620. The plurality of OLTs 610 and the plurality of ONUs 620 are connected to a wavelength demultiplexing unit 630 and an optical splitter 640 by optical fibers. FIG. 11 shows a configuration in which the wavelength demultiplexing unit 630 is connected to the OLT 610 by optical fibers, the optical splitter 640 is connected to the wavelength demultiplexing unit 630 by optical fibers, and the ONUs 520 are connected to the optical splitter 640 by optical fibers. As described above, the plurality of OLTs 610 communicate with each ONU 620 in the upstream and downstream directions using different wavelengths.

[0010] Each OLT 610 accommodates a different ONU 620, and processes the optical signal input after being demultiplexed by the wavelength demultiplexing unit 630. The OLT 610 includes an optical multiplexing / demultiplexing unit 611, an optical transmitting unit 612, a management and control unit 613, and an optical receiving unit 614. The optical multiplexing / demultiplexing unit 611 separates the upstream signal from the downstream signal. The optical transmitting unit 612 converts the data of the electrical signal to be transmitted into an optical signal. The management and control unit 613 superimposes the AMCC signal on the main signal in the electrical stage, or acquires the AMCC signal in the electrical stage. The optical receiving unit 614 converts the optical signal output from the optical multiplexing / demultiplexing unit 611 into an electrical signal.

[0011] The ONU 620 includes an optical multiplexing / demultiplexing unit 621, an optical transmitting unit 622, a management and control unit 623, and an optical receiving unit 624. The optical multiplexing / demultiplexing unit 621 separates an upstream signal from a downstream signal. The optical transmitting unit 622 converts the data of an electrical signal to be transmitted into an optical signal. The management and control unit 623 superimposes an AMCC signal on a main signal in the electrical stage or acquires an AMCC signal in the electrical stage. The optical receiving unit 624 converts the optical signal output from the optical multiplexing / demultiplexing unit 621 into an electrical signal. [Prior art documents] [Non-patent literature]

[0012] [Non-Patent Document 1] “ITU-T G.989.2 Recommendation, “40-Gigabit-capable-passive optical networks (NG-PON2): Physical media dependent (PMD) layer specification,” Feb. 2019. [Non-Patent Document 2] Y. Luo, H. Roberts, K. Grobe, M. Valvo, D. Nesset, K.Asaka, H. Rohde, J. Smith, JS Wey, and F. Effenberger, “Physical Layer Aspects of G-PON2 Standards-Part 2:System Design and Technology Feasibility,” J. Opt. Com-mun. Netw., 8(1), pp.43-52, Jan. 2016. Summary of the Invention [Problem to be solved by the invention]

[0013] If AMCC signals can be used in TDM-PON, management and control signals can be transmitted within the wavelength range of the wavelength used for the main signal, so there is no need to use a dedicated optical wavelength range. Furthermore, there is no need to embed management and control signals in the main signal, so the transmission efficiency of the main signal can be improved. AMCC signals are low-speed signals on the order of kb / s (kilo bit / sec) (see, for example, Non-Patent Document 2). On the other hand, TDM-PON signals are high-speed signals on the order of Gb / s (Giga bit / sec). In the upstream direction of TDM-PON, burst signals that control the transmission timing so that frames from each ONU do not collide are exchanged between the OLT and ONU.

[0014] The frame length of a low-speed AMCC signal is expected to be significantly longer than that of a high-speed burst signal, making it difficult to superimpose the AMCC signal, which is a management and control signal, on the burst signal. This has led to the problem that management and control signals cannot be used in TDM-PON. This problem is not limited to TDM-PON, but is common to all systems that use time division multiplexing.

[0015] In view of the above circumstances, an object of the present invention is to provide a technique that enables a management control signal to be used in a system in which time division multiplexing is performed. [Means for solving the problem]

[0016] One aspect of the present invention is a relay device that relays between multiple optical communication devices that communicate using at least a time division multiplexing method, and includes a data length acquisition unit that acquires information about the data length of an upstream signal transmitted from an optical communication device using the upstream signal, a management control signal generation unit that generates a management control signal used for management and control, a management control signal division unit that divides the generated management control signal based on the information about the data length of the upstream signal acquired by the data length acquisition unit, and a management control signal superposition unit that superimposes the divided management control signal on the upstream signal and forwards it to another optical communication device.

[0017] One aspect of the present invention is an optical access system including a first optical communication device that communicates using at least a time division multiplexing method, a second optical communication device, and a relay device that relays between the first optical communication device and the second optical communication device, wherein the relay device includes a data length acquisition unit that acquires information on a data length of an upstream signal transmitted from the first optical communication device using the upstream signal, a management control signal generation unit that generates a management control signal used for management and control, a management control signal division unit that divides the generated management control signal based on the information on the data length of the upstream signal acquired by the data length acquisition unit, and a management control signal superposition unit that superimposes the divided management control signal on the upstream signal and forwards it to another optical communication device, andThe above The optical access system includes a signal extraction unit that extracts the divided management control signal superimposed on an upstream signal, and an integration unit that integrates the divided management control signal to restore the management control signal.

[0018] One aspect of the present invention is a relay method performed by a relay device that relays between multiple optical communication devices that communicate using at least a time division multiplexing method, the optical communication method comprising: using an upstream signal transmitted from an optical communication device, obtaining information on the data length of the upstream signal, generating a management control signal to be used for management and control, dividing the generated management control signal based on the obtained information on the data length of the upstream signal, and superimposing the divided management control signal on the upstream signal and forwarding it to another optical communication device. Effect of the Invention

[0019] The present invention makes it possible to use a management control signal in a system in which time division multiplexing is performed. [Brief description of the drawings]

[0020] [Figure 1] 1 is a diagram illustrating an example of the configuration of an optical access system according to a first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a configuration of a relay device in the first embodiment. [Diagram 3] FIG. 2 is a diagram illustrating a configuration of an OLT in the first embodiment. [Figure 4] FIG. 2 is a diagram for explaining a process for transmitting an AMCC signal in the first embodiment. [Diagram 5] FIG. 4 is a sequence diagram showing a processing flow of the optical access system in the first embodiment. [Figure 6] FIG. 11 is a diagram illustrating a configuration of a relay device in a second embodiment. [Figure 7] FIG. 11 is a diagram for explaining a process for transmitting an AMCC signal in the second embodiment. [Figure 8]FIG. 11 is a sequence diagram showing a processing flow of the optical access system in the second embodiment. [Figure 9] FIG. 13 is a diagram illustrating a configuration example of an optical access system according to a modified example. [Figure 10] FIG. 1 is a diagram illustrating a configuration of a conventional TDM-PON system. [Figure 11] FIG. 1 is a diagram illustrating a configuration of a conventional PtP WDM-PON system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (overview) In the optical access system of the present invention, an AMCC signal is generated in a relay device that relays communication between an ONU and an OLT, the generated AMCC signal is divided based on an upstream burst signal transmitted from an ONU, and the divided AMCC signal is superimposed on the upstream burst signal. This makes it possible to superimpose the AMCC signal on the upstream burst signal. As a result, it becomes possible to use the AMCC signal in a TDM-PON. The details are explained below.

[0022] (First embodiment) FIG. 1 is a diagram showing an example of the configuration of an optical access system 1 in the first embodiment. The optical access system 1 includes an OLT 10, one or more ONUs 20, and a repeater 60. The OLT 10 and the repeater 60 are connected by optical fibers. The ONUs 20 and the repeater 60 are connected by optical fibers to one or more optical couplers 30, 40, 50. FIG. 1 shows a configuration in which the optical coupler 30 is connected to the repeater 60 by optical fibers, the optical couplers 40 and 50 are connected to the optical coupler 30 by optical fibers, and two ONUs 20 are connected to each of the optical couplers 40 and 50 by optical fibers. Hereinafter, the direction from the OLT 10 to the ONUs 20 is referred to as the downstream direction, and the direction from the ONUs 20 to the OLT 10 is referred to as the upstream direction.

[0023] 1 is an example, and the numbers of ONUs 10, ONUs 20, and optical couplers included in the optical access system 1 are not particularly limited. In the optical access system 1, the following description will be given assuming that communication is performed between the OLT 10 and the ONUs 20 by the TDM-PON method. In the optical access system 1, "baseband modulation" is used, which is a method of superimposing an AMCC signal as a baseband signal onto a main signal.

[0024] The OLT 10 allocates bandwidth to the ONUs 20. Specifically, the OLT 10 allocates data transmission timing and transmission amount to each ONU 20. The data transmission timing indicates the timing at which the ONU 20 starts transmitting a main signal. The transmission amount indicates the amount of data that the ONU 20 can transmit in one transmission.

[0025] The ONU 20 transmits an upstream burst signal to the OLT 10 based on the transmission timing and transmission amount assigned by the OLT 10. The configuration of the ONU 20 is the same as that of the conventional ONU. For example, the ONU 20 has the same configuration as that shown in FIG.

[0026] The optical coupler 40 or the optical coupler 50 multiplexes the optical signals transmitted from the ONU 20 and outputs the multiplexed signal to the optical coupler 30. The optical coupler 30 multiplexes the optical signals output from the optical couplers 40 and 50 and outputs the multiplexed signal to an optical fiber. The optical signal output by the optical coupler 30 is input to the repeater 60 via the optical fiber.

[0027] The repeater 60 superimposes an AMCC signal on an upstream burst signal transmitted from the ONU 20 and transfers it to the OLT 10. Specifically, the repeater 60 generates an AMCC signal to be transmitted to the OLT 10, divides the generated AMCC signal, and superimposes it on the upstream burst signal, which is the main signal. For example, the repeater 60 divides the AMCC signal to a range that can be superimposed on the upstream burst signal, and superimposes the divided AMCC signals on the upstream burst signal to generate transmission data. Dividing an AMCC signal means dividing one AMCC signal into multiple signals. For example, it means dividing the AMCC signal into signals of a size that can be superimposed on the upstream burst signal, in order from the beginning. In the following description, the divided AMCC signal is referred to as a divided AMCC signal.

[0028] FIG. 2 is a diagram showing a configuration of the relay device 60 in the first embodiment. The repeater 60 includes an optical multiplexer / demultiplexer 61 , a splitter 62 , an optical receiver 63 , a burst length acquisition unit 64 , an AMCC signal generator 65 , an AMCC signal splitter 66 , a delay unit 67 , an AMCC signal superimposing unit 68 , and an optical multiplexer / demultiplexer 69 .

[0029] The optical multiplexing / demultiplexing unit 61 separates the upstream signal from the downstream signal. For example, the optical multiplexing / demultiplexing unit 61 outputs the upstream signal to the splitter 62 and outputs the downstream signal to the optical coupler 30. The optical multiplexing / demultiplexing unit 69 outputs the upstream signal to the OLT 10 and outputs the downstream signal to the optical multiplexing / demultiplexing unit 61.

[0030] The splitter 62 splits the upstream signal (e.g., an upstream burst signal) separated by the optical multiplexing / splitting unit 61 and outputs the split signal to a first path and a second path. An example of the splitter 62 may be an optical splitter. An optical splitter with a split ratio of 1:9 may be used to output an optical signal with 10% of the intensity to the optical receiving unit 63 and an optical signal with 90% of the intensity to the delay unit 67. The first path is a path that passes through the optical receiving unit 63, and the second path is a path that passes through the delay unit 67.

[0031] The optical receiving unit 63 includes an O / E (Optical / Electrical) converter such as a photodetector. The optical receiving unit 63 receives the upstream signal branched by the branching device 62, converts the received upstream signal into an electrical signal by the O / E converter, and outputs the electrical signal to the burst length acquisition unit 64. The optical receiving unit 63 receives an upstream burst signal transmitted from the ONU 20, for example.

[0032] The burst length acquisition unit 64 acquires burst length information of the upstream signal received by the optical receiving unit 63. The burst length information is information that indicates the transmission amount of the upstream signal. For example, the burst length acquisition unit 64 may acquire the burst length information from the burst length information written in the header of the received upstream signal, or may acquire the burst length information by measuring the optical intensity of the burst signal. The burst length acquisition unit 64 outputs the acquired burst length information to the AMCC signal division unit 66, and instructs the AMCC signal generation unit 65 to generate an AMCC signal. The burst length acquisition unit 64 is one aspect of a data length acquisition unit.

[0033] The AMCC signal generating unit 65 generates an AMCC signal used for management and control according to an instruction from the burst length acquiring unit 64. Items managed and controlled by the AMCC signal may be control information and monitoring information of the transmission wavelength, etc., as specified in the ITU-T G.989.2 recommendation, or may include other information. The AMCC signal generating unit 65 is one aspect of a management and control signal generating unit.

[0034] The AMCC signal division unit 66 acquires burst length information output from the burst length acquisition unit 64. Based on the burst length information, the AMCC signal division unit 66 divides the AMCC signal generated by the AMCC signal generation unit 65 within a range not exceeding the burst length indicated by the burst length information. For example, the AMCC signal division unit 66 divides the AMCC signal so that the length is the same as the burst length. The AMCC signal division unit 66 generates a divided AMCC signal by the above method. The AMCC signal division unit 66 is one aspect of a management control signal division unit.

[0035] The AMCC signal division unit 66 assigns identification information including division identification information to each divided AMCC signal. The position where the division identification information is assigned may be the beginning or the end of the divided AMCC signal. The division identification information is identification information indicating that the AMCC signal is divided. For example, the division identification information may be separated into identification information indicating that division is in progress and division identification information indicating the end of division, or may include information indicating the order of transmission. Note that the AMCC signal division unit 66 does not need to use the division identification information.

[0036] The delay unit 67 applies a delay to the upstream signal branched by the branching device 62. Specifically, the delay unit 67 applies a delay that is the same as the processing time required for the upstream signal to reach the AMCC signal superimposing unit 68 via the first path. For example, the delay unit 67 may be a delay line, or may have another configuration that can apply a delay.

[0037] The AMCC signal superimposing unit 68 superimposes the divided AMCC signal on the upstream signal (main signal) delayed by the delay unit 67. The AMCC signal superimposing unit 68 superimposes the divided AMCC signal on the main signal using, for example, a VOA (Variable Optical Attenuator). The AMCC signal superimposing unit 68 outputs the upstream signal on which the divided AMCC signal is superimposed to the optical multiplexer / demultiplexer 69. The upstream signal on which the divided AMCC signal is superimposed and output to the optical multiplexer / demultiplexer 69 is output to the OLT 10 by the optical multiplexer / demultiplexer 69. The AMCC signal superimposing unit 68 is one aspect of a management and control signal superimposing unit.

[0038] FIG. 3 is a diagram showing the configuration of the OLT 10 in the first embodiment. The OLT 10 includes an optical multiplexing / demultiplexing unit 11, an optical transmitting unit 12, a media access control unit 13, an optical receiving unit 14, and a management control unit 15. The optical multiplexing / demultiplexing unit 11 separates an upstream signal from a downstream signal. The optical transmitting unit 12 converts data of an electrical signal to be transmitted into an optical signal and transmits it to the repeater 60.

[0039] The media access control unit 13 schedules the transmission timing and transmission amount for each OLT 10 .

[0040] The optical receiving unit 14 includes an O / E converter such as a photodetector. The optical receiving unit 14 receives an optical signal via the optical multiplexing / demultiplexing unit 11, converts the received optical signal into an electrical signal by the O / E converter, and outputs the electrical signal to the media access control unit 13 and the management control unit 15. The optical receiving unit 14 receives an upstream signal (optical signal) on which a divided AMCC signal transmitted from the relay device 60 is superimposed, for example.

[0041] The management and control unit 15 performs processing related to acquisition of an AMCC signal. The management and control unit 15 includes an AMCC signal extraction unit 151, an AMCC signal integration unit 152, and an AMCC signal reception unit 153.

[0042] The AMCC signal extraction unit 151 extracts the divided AMCC signals superimposed on the electrical signal by signal processing etc. For example, the AMCC signal extraction unit 151 uses an LPF to extract the divided AMCC signals superimposed on the electrical signal.

[0043] The AMCC signal integrating unit 152 integrates the divided AMCC signals extracted by the AMCC signal extracting unit 151. Integrating the divided AMCC signals means restoring one AMCC signal by combining a plurality of divided AMCC signals.

[0044] If the divided AMCC signals include division identification information, the AMCC signal integrating unit 152 restores the AMCC signal by arranging the divided AMCC signals in order. If the divided AMCC signals do not include division identification information, the AMCC signal integrating unit 152 restores the AMCC signal by arranging the divided AMCC signals in the order in which they were acquired.

[0045] The AMCC signal receiving unit 153 performs management and control based on the restored AMCC signal.

[0046] FIG. 4 is a diagram for explaining a process for transmitting an AMCC signal in the first embodiment. 4 shows a situation in which an AMCC signal is divided in a repeater 60, and the divided AMCC signal is superimposed on user data of an uplink signal. The repeater 60 divides the AMCC signal based on burst length information obtained based on the uplink signal. As a result, the AMCC signal is divided into divided AMCC signals 55-1 and 55-2. In the example of FIG. 4, identification information 57-1 and 57-2 are assigned to the divided AMCC signals 55-1 and 55-2.

[0047] The repeater 60 superimposes the divided AMCC signal 55-1 on the user data of the first obtained upstream signal. The repeater 60 transfers the upstream signal on which the divided AMCC signal 55-1 is superimposed to the OLT 10. After that, the repeater 60 superimposes the divided AMCC signal 55-2 on the user data of the next received upstream signal. If the divided AMCC signal 55-2 does not fit within the burst length of the next received upstream signal, the repeater 60 divides the divided AMCC signal 55-2 so that it fits within the burst length. The repeater 60 transfers the upstream signal on which the divided AMCC signal 55-2 is superimposed to the OLT 10.

[0048] As described above, in the relay device 60 in the first embodiment, the AMCC signal contains common information regardless of the ONU 20. Therefore, the relay device 60 only needs to superimpose the divided AMCC signals in order on the received upstream signal.

[0049] FIG. 5 is a sequence diagram showing a process flow of the optical access system 1 in the first embodiment. The ONU 20 generates an upstream signal (optical signal) and transmits it to the optical fiber at the transmission timing assigned to the OLT 10 (step S101). The optical signal transmitted from the ONU 20 is input to the repeater 60.

[0050] The optical multiplexer / demultiplexer 61 of the repeater 60 outputs the upstream signal input via the optical fiber to the splitter 62 (step S102). The upstream signal input to the splitter 62 is split and output to a first path and a second path (step S103). The upstream signal output to the first path is input to the optical receiver 63. The upstream signal output to the second path is delayed by the delay unit 67.

[0051] The optical receiving unit 63 converts the upstream signal into an electrical signal and outputs it to the burst length acquiring unit 64. The burst length acquiring unit 64 acquires burst length information based on the electrical signal converted by the optical receiving unit 63 (step S104). The burst length acquiring unit 64 outputs the acquired burst length information to the AMCC signal dividing unit 66, and instructs the AMCC signal generating unit 65 to generate an AMCC signal.

[0052] The AMCC signal generating unit 65 generates an AMCC signal according to an instruction from the burst length acquiring unit 64 (step S105). The AMCC signal generating unit 65 outputs the generated AMCC signal to the AMCC signal dividing unit 66. The AMCC signal dividing unit 66 divides the AMCC signal output from the AMCC signal generating unit 65 according to the burst length notified by the burst length acquiring unit 64 (step S106).

[0053] Specifically, the AMCC signal division unit 66 divides the AMCC signal so that the signal has a size not exceeding the burst length. In this way, the AMCC signal division unit 66 generates a divided AMCC signal. The AMCC signal division unit 66 assigns identification information to the generated divided AMCC signal. The AMCC signal division unit 66 outputs the divided AMCC signal to the AMCC signal superimposition unit 68.

[0054] The AMCC signal division unit 66 may output the divided AMCC signals each time burst length information is obtained from the burst length acquisition unit 64, rather than outputting the divided AMCC signals collectively. This prevents a plurality of divided AMCC signals from being output at the transfer timing of one upstream data.

[0055] The AMCC signal superimposing unit 68 superimposes the divided AMCC signal output from the AMCC signal dividing unit 66 on the upstream signal delayed by the delay unit 67 (step S107). Specifically, the AMCC signal superimposing unit 68 uses a VOA to superimpose the divided AMCC signal on the upstream signal delayed. The upstream signal on which the divided AMCC signal is superimposed is input to an optical multiplexer / demultiplexer 69. The optical multiplexer / demultiplexer 69 outputs the input upstream signal on which the divided AMCC signal is superimposed to the OLT 10 (step S107).

[0056] The optical multiplexing / demultiplexing unit 11 of the ONU 20 outputs the upstream signal input via the optical fiber to the optical receiving unit 14. The optical receiving unit 14 converts the upstream signal input via the optical multiplexing / demultiplexing unit 11 into an electrical signal. The AMCC signal extracting unit 151 extracts the divided AMCC signal from the electrical signal converted by the optical receiving unit 14 (step S109). The AMCC signal extracting unit 151 outputs the extracted divided AMCC signal to the AMCC signal integrating unit 152. At this point in time, there is only one divided AMCC signal. In this case, the AMCC signal cannot be restored in the AMCC signal integrating unit 152.

[0057] The process from step S102 to step S108 is repeatedly executed every time an upstream signal is obtained in the relay device 60. For example, the process from step S102 to step S108 is repeatedly executed until the relay device 60 finishes transmitting the divided AMCC signal.

[0058] The AMCC signal integrating unit 152 waits until all the divided AMCC signals are collected (step S110). For example, if the divided AMCC signals are provided with division identification information, the AMCC signal integrating unit 152 waits to process until a divided AMCC signal to which division identification information indicating the end of division is provided is acquired. If the divided AMCC signals are not provided with division identification information, the AMCC signal integrating unit 152 waits to process until a predetermined period of divided AMCC signals is acquired. The predetermined period may be set in advance.

[0059] When the AMCC signal integrating unit 152 acquires all of the divided AMCC signals, the AMCC signal integrating unit 152 integrates the acquired divided AMCC signals (step S111). This restores the AMCC signal. The AMCC signal integrating unit 152 outputs the restored AMCC signal to the AMCC signal receiving unit 153. The AMCC signal receiving unit 153 receives the restored AMCC signal (step S112). Thereafter, the AMCC signal receiving unit 153 performs management and control based on the received AMCC signal.

[0060] According to the optical access system 1 in the first embodiment configured as above, it becomes possible to use an AMCC signal in a TDM-PON. Specifically, the repeater device 60 divides the AMCC signal according to burst length information in an upstream signal transmitted from the ONU 20. The repeater device 60 superimposes the divided AMCC signal on the received upstream signal. This makes it possible to superimpose the AMCC signal on the burst signal transmitted from the ONU 20. Therefore, it becomes possible to use an AMCC signal in a TDM-PON.

[0061] Furthermore, in the optical access system 1, the AMCC signal can be inserted from a relay point of the network by superimposing the AMCC signal between the OLT 10 and the ONU 20. This makes it possible to transmit the AMCC signal without passing through a user terminal.

[0062] Furthermore, in the optical access system 1, by dividing the AMCC signal, it is possible to superimpose a low-speed AMCC signal on a high-speed burst signal. Therefore, even in TDM-PON, it is not necessary to embed a signal for management and control in the main signal, and the transmission efficiency of the main signal can be improved.

[0063] Second embodiment In the first embodiment, the repeater device superimposes a divided AMCC signal every time an upstream signal is obtained from an ONU, regardless of the ONU that is the source of the upstream signal. In the second embodiment, a configuration will be described in which the repeater device 60 generates an AMCC signal for each ONU, divides the AMCC signal corresponding to each ONU, and superimposes it on the upstream signal.

[0064] In the second embodiment, the basic system configuration is the same as that of the first embodiment. The difference from the first embodiment is the configuration of the relay device. Therefore, the relay device will be described below.

[0065] FIG. 6 is a diagram showing a configuration of a relay device 60a in the second embodiment. The repeater 60a includes an optical multiplexer / demultiplexer 61, a splitter 62, an optical receiver 63, a burst length acquirer 64, AMCC signal generators 65-1 to 65-n, a delay unit 67, an AMCC signal superimposing unit 68a, an optical multiplexer / demultiplexer 69, a management and control unit 70, an AMCC signal extractor 71, and a user information acquirer 72. n is an integer equal to or greater than 2. For example, the number of AMCC signal generators 65-1 to 65-n is the same as the number of ONUs 20 accommodated in the repeater 60a.

[0066] The configuration of the relay device 60a is different from that of the relay device 60 in that it includes a plurality of AMCC signal generators 65-1 to 65-n and an AMCC signal superimposing unit 68a instead of the AMCC signal generator 65 and the AMCC signal superimposing unit 68, and in that it newly includes a management and control unit 70, an AMCC signal extracting unit 71, and a user information acquiring unit 72. The other configuration of the relay device 60a is similar to that of the relay device 60. Therefore, a description of the entire relay device 60a will be omitted, and only the AMCC signal generators 65-1 to 65-n, the AMCC signal superimposing unit 68a, the management and control unit 70, the AMCC signal extracting unit 71, and the user information acquiring unit 72 will be described.

[0067] The user information acquisition unit 72 acquires source information from information included in the upstream signal received by the optical receiving unit 63. For example, the user information acquisition unit 72 acquires information for identifying the ONU 20 that is the source.

[0068] The management control unit 70 holds information for managing and controlling each ONU 20. The information for management and control is information included in an AMCC signal and is used for managing and controlling the ONU 20. The management control unit 70 may be provided outside the relay device 60.

[0069] The AMCC signal generating units 65-1 to 65-n generate an AMCC signal for each ONU 20 from information for managing and controlling the ONU 20 held in the management control unit 70. For example, the AMCC signal generating unit 65-1 generates an AMCC signal for the ONU 20-1. In this manner, the AMCC signal generating units 65-1 to 65-n generate an AMCC signal for the ONU 20 related to the information held in the management control unit 70. That is, the AMCC signal generating units 65-1 to 65-n generate an AMCC signal including information for the ONU 20 for which the management and control information held in the management control unit 70 exists.

[0070] The AMCC signal extractor 71 extracts an AMCC signal based on the source information acquired by the user information acquirer 72 and the burst length information acquired by the burst length acquirer 64. Specifically, the AMCC signal extractor 71 divides and extracts the AMCC signal for the ONU 20 specified by the source information within a range not exceeding the transmission amount indicated by the burst length information. In this way, the AMCC signal extractor 71 has a function of dividing and extracting the AMCC signal for the ONU 20 specified by the source information from among the AMCC signals for each ONU generated by the AMCC signal generators 65-1 to 65-n. The AMCC signal extractor 71 is one aspect of a management control signal divider.

[0071] The AMCC signal superimposing unit 68a superimposes the extracted divided AMCC signal on the upstream signal (main signal) that has been delayed by the delay unit 67. The AMCC signal superimposing unit 68a is one aspect of a management and control signal superimposing unit.

[0072] FIG. 7 is a diagram for explaining a process for transmitting an AMCC signal in the second embodiment. FIG. 7 shows a situation where the AMCC signal for each ONU 20 is divided in the repeater 60a, and the divided AMCC signal is superimposed on the user data of the upstream signal. Assume that the repeater 60a first receives the upstream signal sent from the ONU 20-1 as shown in FIG. 7. In this case, the AMCC signal generator 65-1 corresponding to the ONU 20-1 generates an AMCC signal for the ONU 20-1 based on information obtained from the management control unit 70. The AMCC signal extractor 71 divides the AMCC signal for the ONU 20-1 based on burst length information obtained based on the upstream signal. As a result, the AMCC signal for the ONU 20-1 is divided into divided AMCC signals 55-1 and 55-2. In the example of FIG. 7, identification information 57-1 is assigned to the divided AMCC signal 55-1. It is preferable that the identification information assigned here includes information for identifying the ONU 20-1 and identification information indicating that the AMCC signal is divided.

[0073] The repeater 60a superimposes the divided AMCC signal 55-1 on the user data of the upstream signal sent from the ONU 20-1. The repeater 60a transfers the upstream signal on which the divided AMCC signal 55-1 is superimposed to the OLT 10. The divided AMCC signal 55-2 divided from the AMCC signal for the ONU 20-1 is put on hold for transmission until the upstream signal sent from the ONU 20-1 is obtained. The divided AMCC signal put on hold for transmission may be stored in a memory (not shown).

[0074] Next, it is assumed that the repeater 60a receives an upstream signal sent from the ONU 20-2. In this case, the AMCC signal generator 65-2 corresponding to the ONU 20-2 generates an AMCC signal for the ONU 20-2 based on information obtained from the management and control unit 70. The AMCC signal extractor 71 divides the AMCC signal for the ONU 20-2 based on burst length information obtained based on the upstream signal. As a result, the AMCC signal for the ONU 20-2 is divided into divided AMCC signals 56-1 and 56-2.

[0075] The repeater 60a superimposes the divided AMCC signal 56-1 on the user data of the upstream signal sent from the ONU 20-2. The repeater 60a transfers the upstream signal on which the divided AMCC signal 56-1 is superimposed to the OLT 10. The divided AMCC signal 56-2, which is divided from the AMCC signal for the ONU 20-2, is put on hold for transmission until the upstream signal sent from the ONU 20-2 is obtained.

[0076] As described above, the relay device 60a in the second embodiment generates a different AMCC signal for each ONU 20. This makes it possible to superimpose a different AMCC signal for each ONU 20.

[0077] Fig. 8 is a sequence diagram showing the flow of processing in the optical access system 1 in the second embodiment. The processing in Fig. 8 will be described assuming that, among the multiple ONUs 20, the ONU 20-1 transmits an upstream signal.

[0078] The ONU 20-1 generates an upstream signal (optical signal) and transmits it to the optical transmission line (step S201) at the transmission timing assigned to the OLT 10. The optical signal transmitted from the ONU 20-1 is input to the repeater 60a.

[0079] The optical multiplexer / demultiplexer 61 of the repeater 60a outputs the upstream signal input via the optical fiber to the splitter 62 (step S202). The upstream signal input to the splitter 62 is split and output to a first path and a second path (step S203). The upstream signal output to the first path is input to the optical receiver 63. The upstream signal output to the second path is delayed by the delay unit 67.

[0080] The optical receiving unit 63 converts the upstream signal into an electrical signal and outputs it to the user information acquiring unit 72. The user information acquiring unit 72 acquires source information based on the electrical signal received by the optical receiving unit 63 (step S204). For example, the user information acquiring unit 72 acquires information for identifying ONU 20-1 as source information from the electrical signal. The user information acquiring unit 72 outputs the acquired source information to the AMCC signal extracting unit 71. The user information acquiring unit 72 outputs the electrical signal received by the optical receiving unit 63 to the burst length acquiring unit 64.

[0081] The burst length acquisition unit 64 acquires burst length information based on the electrical signal output from the user information acquisition unit 72 (step S205). The burst length acquisition unit 64 outputs the acquired burst length information to the AMCC signal extraction unit 71.

[0082] The AMCC signal generating units 65-1 to 65-n check whether information is stored in the management control unit 70. Here, it is assumed that information corresponding to ONU 20-1 is stored in the management control unit 70. The AMCC signal generating unit 65-1 corresponding to ONU 20-1 generates an AMCC signal using the information stored in the management control unit 70 (step S206). Specifically, the AMCC signal generating unit 65-1 generates an AMCC signal including information for ONU 20-1 stored in the management control unit 70.

[0083] The AMCC signal extractor 71 identifies the AMCC signal generators 65-1 to 65-n corresponding to the source ONU 20, based on the source information acquired from the user information acquirer 72. Since the source information acquired from the user information acquirer 72 includes information for identifying ONU 20-1, the AMCC signal extractor 71 identifies the AMCC signal generator 65-1 corresponding to ONU 20-1.

[0084] Next, the AMCC signal extractor 71 divides the AMCC signal generated by the specified AMCC signal generator 65-1 based on the burst length information acquired from the burst length acquirer 64. Specifically, the AMCC signal extractor 71 divides the AMCC signal generated by the AMCC signal generator 65-1 so as to obtain a signal having a size not exceeding the burst length. As a result, the AMCC signal extractor 71 extracts the divided AMCC signal for ONU 20-1 (step S207). The AMCC signal extractor 71 assigns identification information to the extracted divided AMCC signal. The AMCC signal extractor 71 outputs the divided AMCC signal to the AMCC signal superimposing unit 68a.

[0085] The AMCC signal extractor 71 may output the divided AMCC signals each time burst length information is obtained from the burst length acquirer 64, rather than outputting the divided AMCC signals all at once. This prevents a plurality of divided AMCC signals from being output at the transfer timing of one upstream data.

[0086] The AMCC signal superimposing unit 68a superimposes the divided AMCC signal output from the AMCC signal extracting unit 71 onto the upstream signal delayed by the delay unit 67 (step S208). The upstream signal on which the divided AMCC signal is superimposed is input to the optical multiplexer / demultiplexer 69. The optical multiplexer / demultiplexer 69 outputs the input upstream signal on which the divided AMCC signal is superimposed to the OLT 10 (step S209).

[0087] The optical multiplexing / demultiplexing unit 11 of the ONU 20 outputs the upstream signal input via the optical fiber to the optical receiving unit 14. The optical receiving unit 14 converts the upstream signal input via the optical multiplexing / demultiplexing unit 11 into an electrical signal. The AMCC signal extracting unit 151 extracts the divided AMCC signal from the electrical signal converted by the optical receiving unit 14 (step S210). The AMCC signal extracting unit 151 outputs the extracted divided AMCC signal to the AMCC signal integrating unit 152. At this point in time, there is only one divided AMCC signal for ONU 20-1. In this case, the AMCC signal cannot be restored in the AMCC signal integrating unit 152.

[0088] The process from step S202 to step S209 is repeatedly executed every time the relay device 60a obtains an upstream signal. For example, the process from step S202 to step S209 is repeatedly executed until the relay device 60a finishes transmitting the divided AMCC signal.

[0089] For example, assume that an upstream signal sent from ONU 20-1 is received by the repeater 60a. In this case, if there is a divided AMCC signal for ONU 20-1 that has not been divided and transmitted last time, the AMCC signal extractor 71 divides the divided AMCC signal for ONU 20-1 that has not been transmitted based on the newly obtained burst length information. If the divided AMCC signal for ONU 20-1 that has not been transmitted is smaller than the burst length indicated by the newly obtained burst length information, the AMCC signal extractor 71 does not need to divide it. Then, the AMCC signal extractor 71 outputs the obtained divided AMCC signal for ONU 20-1 to the AMCC signal superimposing unit 68a. As a result, the remaining divided AMCC signal for ONU 20-1 is transmitted to the OLT 10.

[0090] The AMCC signal integrating unit 152 waits until all the divided AMCC signals are collected (step S110). For example, if the divided AMCC signals are provided with division identification information, the AMCC signal integrating unit 152 waits to process until a divided AMCC signal to which division identification information indicating the end of division is provided is acquired. If the divided AMCC signals are not provided with division identification information, the AMCC signal integrating unit 152 waits to process until a predetermined period of divided AMCC signals is acquired. The predetermined period may be set in advance.

[0091] In the second embodiment, since a different AMCC signal is generated for each ONU 20, the AMCC signal integrating unit 152 classifies the divided AMCC signals for each ONU 20 and waits until all of the divided AMCC signals are collected. For example, the AMCC signal integrating unit 152 may perform a process of integrating the divided AMCC signals when the divided AMCC signals for one ONU 20 are collected.

[0092] When the AMCC signal integrating unit 152 acquires all of the divided AMCC signals corresponding to a certain ONU 20 (for example, ONU 20-1), the AMCC signal integrating unit 152 integrates the acquired divided AMCC signals (step S111). This restores the AMCC signal for ONU 20-1. The AMCC signal integrating unit 152 outputs the restored AMCC signal to the AMCC signal receiving unit 153. The AMCC signal receiving unit 153 receives the restored AMCC signal (step S112). Thereafter, the AMCC signal receiving unit 153 manages and controls the ONU 20-1 based on the received AMCC signal.

[0093] In the optical access system 1 in the second embodiment configured as above, it is possible to obtain the same effects as in the first embodiment.

[0094] Furthermore, in the optical access system 1 in the second embodiment, an AMCC signal is generated for each ONU 20, so that a different AMCC signal for each ONU 20 can be superimposed on the main signal.

[0095] Modifications of the first and second embodiments will be described. The topology of the OLT 10 and the ONU 20 in the first and second embodiments is not limited to a passive double star topology, but may be a bus topology or a ring topology. In the first and second embodiments, communication between the OLT 10 and the ONU 20 is described as being performed using the TDM-PON method, but it is not limited to TDM-PON, and various division multiplexing techniques such as wavelength division multiplexing, code division multiplexing, and frequency division multiplexing may be combined with TDM.

[0096] In the first and second embodiments, a configuration in which the AMCC signal is extracted within the OLT 10 has been shown, but as shown in Fig. 9, a configuration in which the split AMCC signal is extracted between the OLT 10 and the repeater 60 may also be used. In such a configuration, a mechanism for splitting the upstream signal (for example, an optical splitter or a switch) may be provided between the OLT 10 and the repeater 60.

[0097] FIG. 9 is a diagram showing an example of the configuration of an optical access system 1b according to a modified example. The optical access system 1b includes an OLT 10, one or more ONUs 20, a relay device 60, and a management and control device 80. The optical access system 1b differs from the first and second embodiments in that an upstream signal is branched between the relay device 60 and the OLT 10 and input to the management and control device 80 to extract an AMCC signal, and that the OLT 10 does not include a management and control unit 15.

[0098] The management control device 80 is provided between the OLT 10 and the relay device 60, and extracts the divided AMCC signal superimposed on the upstream signal. The management control device 80 includes an optical receiving unit 81, an AMCC signal extracting unit 82, an AMCC signal integrating unit 83, and an AMCC signal receiving unit 84.

[0099] The optical receiving unit 81 includes an O / E converter such as a photodetector. The optical receiving unit 81 receives an upstream signal transferred from the relay device 60, converts the received upstream signal into an electrical signal by the O / E converter, and outputs the electrical signal to the AMCC signal extracting unit 82. The optical receiving unit 81 may receive an upstream signal branched from an optical splitter provided between the OLT 10 and the relay device 60, for example.

[0100] The AMCC signal extraction unit 82 performs the same processing as the AMCC signal extraction unit 151 . The AMCC signal integrating unit 83 performs the same processing as the AMCC signal integrating unit 152 . The AMCC signal receiving unit 84 performs the same processing as the AMCC signal receiving unit 153 .

[0101] The optical access system 1b may include a relay device 60a instead of the relay device 60. When configured in this way, each functional unit included in the management control device 80 performs the same process as the functional unit with the same name included in the OLT 10 in the second embodiment.

[0102] Some of the functions of the OLT 10, ONU 20, relay devices 60, 60a, and management control device 80 in the above-mentioned embodiment may be realized by a computer. In this case, a program for realizing the functions may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Note that the "computer system" here includes hardware such as an OS and peripheral devices.

[0103] In addition, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include those that dynamically hold a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and those that hold a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in such a case. Furthermore, the above program may be one that realizes part of the above-mentioned functions, or may be one that can realize the above-mentioned functions in combination with a program already recorded in the computer system, or may be one that is realized using a programmable logic device such as an FPGA.

[0104] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Industrial Applicability]

[0105] The present invention is applicable to at least an optical access system that performs time division multiplexing. [Explanation of symbols]

[0106] 10...OLT (optical communication device), 11...optical multiplexing / demultiplexing section, 12...optical transmitting section, 13...media access control section, 14...optical receiving section, 15...management control section, 20...ONU (optical communication device), 60, 60a...relay device, 61, 69...optical multiplexing / demultiplexing section, 62...branching device, 63, 81...optical receiving section, 64...burst length acquisition section, 65, 65-1 to 65-n...AMCC signal generation section, 66...AMCC signal division section, 67...delay section, 68, 68a...AMCC signal superimposition section, 69...optical multiplexing / demultiplexing device, 70...management control section, 71...AMCC signal extraction section, 72...user information acquisition section, 80...management control device (optical communication device), 82, 151...AMCC signal extraction section, 83, 152...AMCC signal integration section, 84, 153…AMCC signal receiving section

Claims

1. A relay device that relays signals between a plurality of optical communication devices that communicate using at least a time division multiplexing system, a data length acquisition unit that acquires information on a data length of an upstream signal transmitted from an optical communication device by using the upstream signal; a management and control signal generating unit for generating a management and control signal used for management and control; a management and control signal division unit that divides the generated management and control signal based on information on the data length of the uplink signal acquired by the data length acquisition unit; a management and control signal superimposing unit that superimposes the divided management and control signals on the upstream signal and transfers the superimposed signal to another optical communication device; A relay device comprising:

2. 2. The relay device according to claim 1, wherein the management and control signal division unit divides the management and control signal into pieces each having a size not exceeding a data length indicated by information on a data length of the upstream signal.

3. a branching unit for branching an upstream signal transmitted from the optical communication device, 3. The relay device according to claim 1, wherein the management and control signal superimposing unit superimposes the divided management and control signal onto the upstream signal that has been delayed on one of the branched paths.

4. the management and control signal generating unit is provided for each optical communication device, a user information acquisition unit that acquires, from the uplink signal, source information indicating a source of the uplink signal; the management and control signal division unit divides the management and control signal generated by a management and control signal generation unit associated with a source optical communication device indicated by the source information acquired by the user information acquisition unit, based on information on a data length of the upstream signal. The relay device according to claim 1 .

5. An optical access system including a first optical communication device that communicates using at least a time division multiplexing system, a second optical communication device, and a relay device that relays between the first optical communication device and the second optical communication device, The relay device is a data length acquisition unit that acquires information on a data length of an upstream signal transmitted from the first optical communication device by using the upstream signal; a management and control signal generating unit for generating a management and control signal used for management and control; a management and control signal division unit that divides the generated management and control signal based on information on the data length of the uplink signal acquired by the data length acquisition unit; a management and control signal superimposing unit that superimposes the divided management and control signals on the upstream signal and transfers the superimposed signal to another optical communication device; Equipped with a signal extraction unit that extracts the divided management and control signals superimposed on the upstream signal transferred from the relay device; an integration unit that integrates the divided management and control signals to restore the management and control signal; An optical access system comprising:

6. a management control device that manages and controls the first optical communication device; The management control device includes a receiving unit that receives the upstream signal transferred from the relay device; The signal extraction unit; The integration unit; The optical access system according to claim 5 .

7. A relay method performed by a relay device that relays between a plurality of optical communication devices that communicate at least using a time division multiplexing system, comprising: Using an upstream signal transmitted from an optical communication device, information on a data length of the upstream signal is obtained; generating a management control signal used for management and control; Dividing the generated management and control signal based on the acquired information on the data length of the upstream signal; An optical communication method in which the divided management and control signals are superimposed on the upstream signal and transferred to another optical communication device.

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