JP6190311B2 - Optical communication system, control method, and computer program - Google Patents

Description

  The present invention relates to a technique for controlling optical line communication.

  As one form of access network, PON (Passive Optical Network) is known. The PON is between an OLT (Optical Line Terminal) installed on the telecommunications carrier side and an ONU (Optical Network Unit: subscriber side optical line termination device) installed on the subscriber side. In the communication, the access network is configured to branch the optical signal into a plurality of parts by using a splitter which is a passive element without performing photoelectric conversion. In such a PON, since a single optical fiber can be shared by a plurality of users, an economical network can be constructed.

  Of the PONs, those in which the OLT and the ONU communicate with each other using an Ethernet (registered trademark) frame are called EPON (Ethernet (registered trademark) PON). In general, in PON, the direction of communication from the OLT to the ONU is referred to as the downstream direction, and the direction of communication from the ONU to the OLT is referred to as the upstream direction. In many PONs including EPON, uplink communication is performed by TDMA (Time Division Multiple Access). In TDMA, the OLT transmits a GATE frame to notify a plurality of ONUs of a frame transmission start time and a transmission permission time. Each ONU starts frame transmission to the OLT at the notified transmission start time, and transmits a frame during the notified transmission permission time. In TDMA control, the transmission start time and the transmission permission time are determined so that the time for each ONU to transmit a frame does not overlap with other ONUs.

  Thus, in TDMA, the ONU can transmit a frame to the OLT only at the transmission timing notified from the OLT. Therefore, the ONU accumulates the generated uplink transmission signal in an internal buffer until the transmission timing notified from the OLT arrives. When the transmission timing arrives, the ONU transmits the frames accumulated in the buffer in bursts. In the following description, this burst signal transmitted from the ONU is referred to as a burst signal.

FIG. 6 is a timing chart showing a specific example of timing at which a burst signal is transmitted to the OLT.
In FIG. 6, the horizontal axis represents time. Reference numerals 90-1 to 90-4 correspond to burst signals transmitted from each ONU. Burst signal 90-1 represents the signal transmitted during time _{t 12} from the time _{t 11.} Similarly, the burst signal 90-2, represents the signal transmitted during time _{t 22} from the time _{t 21.} Similarly, the burst signal 90-3 represents the signal transmitted during time _{t 32} from the time _{t 31.} Similarly, the burst signal 90-4 represents the signal transmitted during time _{t 42} from the time _{t 41.} In the following description, the burst signals 90-1 to 90-4 are referred to as burst signals 90 unless otherwise specified.
That is, the time at the left end of the burst signal 90 represents the transmission start time, and the width of the burst signal 90 represents the transmission permission time. T _g is a guard time that is inserted in order to absorb a deviation in timing at which each ONU transmits a burst signal.

FIG. 7 is a diagram illustrating a specific example of the configuration of the burst signal 90.
As shown in FIG. 7, the burst signal 90 includes a preamble signal 901, LLID (Logical Link ID) 902-1 to 902-3, MAC (Media Access Control) frames 903-1 to 903-3, IFGs 904-1 and 904-. 2 The preamble signal 901 is a synchronization signal added so that the OLT on the receiving side detects the burst signal 90. The LLIDs 902-1 to 902-3 are identification information of each ONU assigned by the OLT. The MAC frames 903-1 to 903-3 are MAC frames including transmission data. The LLIDs 902-1 to 902-3 are assigned to the header portions of the MAC frames 903-1 to 903-3, respectively. IFGs 904-1 and 904 are IFGs (Inter Frame Gap) inserted to adjust reception of consecutive frames. In the following description, LLID 902-1 to 902-3 will be referred to as LLID 902 unless otherwise specified. Similarly, the MAC frames 903-1 to 903-3 are referred to as MAC frames 903. Similarly, IFG904-1 and 904-2 are referred to as IFG904. The burst signal 90 is generated as a signal including a plurality of MAC frames 903 with the IFG 904 interposed therebetween.

  On the other hand, there is a technique called signal superposition transmission that improves the transmission efficiency of an optical line by superimposing and transmitting a part of a transmitted signal and restoring a collided signal (for example, see Non-Patent Document 1). ). Non-Patent Document 1 discloses a technique related to signal superposition transmission in which a frequency band used for signal transmission is superimposed. When such signal superposition transmission is performed in TDMA, the OLT determines the transmission start time and the transmission permission time so that a part of the time transmitted by each ONU overlaps, and notifies each ONU. Therefore, some of the signals transmitted from each ONU to the OLT collide. When performing signal superimposition transmission in TDMA, the OLT has a function of detecting and correcting a signal error caused by signal collision. Information for detecting and correcting an error is added to a signal transmitted from the ONU, and the OLT detects and corrects an error in the received signal based on this information to restore the collided signal.

FIG. 8 is a diagram showing a state in which burst signals transmitted by signal superposition transmission in TDMA collide.
In FIG. 8, the horizontal axis represents time. P ₁ and P ₂ are burst signals transmitted from the ONU. T ₁ is a transmission start time permitted for transmission of the burst signal P ₁ . T _P1 is the transmission permitted time allowed for transmission of the burst signal P _1. T ₂ is a transmission start time permitted for transmission of the burst signal P ₂ . T _P2 is the transmission permitted time allowed for transmission of the burst signal P _2. In the example of FIG. 8, OLT, the time represented by T _d is to overlap, thereby controlling the transmission start time and transmission permitted time of the burst signal P ₁ and the burst signal P _2.

If the burst signal P ₁ and the burst signal P ₂ is impacted by the signal superimposing transmission in TDMA, the length of time that the signal collision is the same time for both. However, since the burst signal P ₁ and the burst signal P ₂ have different ONUs that have transmitted these signals, the situation in which signals such as coding rate and signal quality are transmitted may be different. Therefore, the limit of the ratio (superimposition ratio) of signals that can be superimposed in the signals to the entire signal may be different. Therefore, it is necessary to superimpose signals in TDMA according to the situation in which each signal is transmitted.

J.Mashino et.al, “Total Frequency Utilization Efficiency Improvement by Superposed Multicarrier Transmission Scheme”, IEEE PIMRC 2009

  In the conventional optical communication system, the station side optical line terminator (OLT) only notifies the subscriber side optical line terminator (ONU) of the transmission start time and the transmission permission time. For this reason, it has not been possible to control signal superimposition transmission according to each transmission situation for the subscriber-side optical line terminator that transmits signals in different situations as described above.

  In view of the above circumstances, in the TDMA in an optical communication system, the present invention can control signal superposition transmission according to each transmission status for a subscriber-side optical line terminating device that transmits signals in different situations. An object of the present invention is to provide an optical communication system and a control method that can be used.

  One aspect of the present invention includes a station-side optical line terminator and a subscriber-side optical line terminator that communicate via an optical communication path, and the station-side optical line terminator includes a transmission timing and a transmission permission time of an optical signal. To the subscriber side optical line terminator, and the subscriber side optical line terminator transmits the optical signal to the station side optical line terminator during the transmission permission time from the notified timing. In the optical communication system, the station side optical line terminator can be used for transmission of actual data within a communication unit communicating with the subscriber side optical line terminator and the transmission permission time. A generating unit that calculates a filling permission time and generates a notification signal for notifying the filling permission time to the subscriber side optical line terminator, wherein the subscriber side optical line terminator is the station side A communication unit that communicates with the optical line termination device; An optical communication system comprising: an analysis unit that analyzes the notification signal and obtains the filling permission time; and a generation unit that generates a transmission signal to be transmitted to the station-side optical network unit based on the filling permission time. .

  One aspect of the present invention is the above-described optical communication system, wherein the generation unit of the subscriber-side optical line termination device transmits the transmission signal to a time difference between the transmission permission time and the filling permission time. In this optical communication system, a dummy signal having a possible signal length is added, and the transmission signal to which the dummy signal is added is encoded.

  One aspect of the present invention is the optical communication system as described above, wherein in the optical communication system, when the signal superposition transmission is performed to superimpose the optical signals transmitted by the plurality of subscriber-side optical line terminators, the station The side optical line terminator is an optical communication system that controls a superposition rate in signal superposition transmission by changing the filling permission time.

  One aspect of the present invention includes a station-side optical line terminator and a subscriber-side optical line terminator that communicate via an optical communication path, and the station-side optical line terminator includes a transmission timing and a transmission permission time of an optical signal. To the subscriber side optical line terminator, and the subscriber side optical line terminator transmits the optical signal to the station side optical line terminator during the transmission permission time from the notified timing. In the optical communication system, the station side optical line terminator communicates with the subscriber side optical line terminator, and the filling permission that can be used for transmission of actual data within the transmission permission time. Generating a notification signal for calculating a time and notifying the subscriber-side optical line terminator of the filling permission time, and the subscriber-side optical line terminator includes the station-side optical signal. Communicate with line termination equipment A communication step, an analysis step of analyzing the notification signal and obtaining the filling permission time, and a generation step of generating a transmission signal to be transmitted to the station side optical network unit based on the filling permission time. This is a communication control method.

  One aspect of the present invention includes a station-side optical line terminator and a subscriber-side optical line terminator that communicate via an optical communication path, and the station-side optical line terminator includes a transmission timing and a transmission permission time of an optical signal. To the subscriber side optical line terminator, and the subscriber side optical line terminator transmits the optical signal to the station side optical line terminator during the transmission permission time from the notified timing. A station-side optical line terminator in an optical communication system, a communication unit that communicates with the subscriber-side optical line terminator, and a filling permission that can be used for transmission of actual data within the transmission permission time A computer program for causing a computer to function as a station-side optical line terminator, comprising: a generation unit that calculates a time and generates a notification signal for notifying the subscriber-side optical line terminator of the filling permission time It is a non.

  One aspect of the present invention includes a station-side optical line terminator and a subscriber-side optical line terminator that communicate via an optical communication path, and the station-side optical line terminator includes a transmission timing and a transmission permission time of an optical signal. To the subscriber side optical line terminator, and the subscriber side optical line terminator transmits the optical signal to the station side optical line terminator during the transmission permission time from the notified timing. A subscriber-side optical line terminator in an optical communication system, comprising: a communication unit communicating with the station-side optical line terminator; and a signal transmitted from the station-side optical line terminator; Of the time, an analysis unit that acquires a filling permission time that can be used for transmission of actual data, a generation unit that generates a transmission signal to be transmitted to the station side optical line termination device based on the filling permission time, Subscriber-side optical line A computer program for causing a computer to function as an end device.

  According to the present invention, in TDMA in an optical communication system, it is possible to control signal superposition transmission according to each transmission status for a subscriber-side optical line terminating device that transmits signals in different situations.

1 is a system configuration diagram showing a system configuration of an optical communication system in an embodiment. The functional block diagram which shows the function structure of OLT100. The functional block diagram which shows the function structure of ONU200. Schematic which shows a mode that the burst signal transmitted to OLT100 is produced | generated by the transmission control part 250. FIG. The flowchart which shows the flow of the process which ONU200 transmits a flame | frame to OLT100 based on an extended GATE frame. The timing chart which shows the specific example of the timing which a burst signal is transmitted to OLT. The figure which shows the specific example of a structure of the burst signal 90. FIG. The figure which shows a mode that the burst signal transmitted by the signal superimposition transmission in TDMA collides.

FIG. 1 is a system configuration diagram illustrating a system configuration of an optical communication system according to an embodiment.
The optical communication system shown in FIG. 1 is an optical communication system realized by EPON, for example. In the optical communication system shown in FIG. 1, one OLT (Optical Line Terminal) 100 and a plurality of ONUs (Optical Network Units: subscriber side optical line terminators) 200-1 to 200-n Are connected via the optical communication path 500. The optical communication path 500 is formed with an optical splitter, an optical fiber or the like. In the following description, unless otherwise specified, ONUs 200-1 to 200-n are described as ONUs 200.

  The OLT 100 is an optical line terminating device installed on the telecommunications carrier side. An upstream network 300 is connected upstream of the OLT 100. The host network 300 includes various servers that exist on the Internet, for example. For example, in communication between the upper network 300 and the optical communication path 500, the OLT 100 performs signal conversion between an electrical signal and an optical signal, signal multiplexing, and the like.

  The ONU 200 is an optical line terminating device installed on the subscriber side. Lower networks 400-1 to 400-n are connected to the downstream sides of the ONUs 200-1 to 200-n, respectively. The lower networks 400-1 to 400-n include network devices such as personal computers used in subscriber homes, for example. In the following description, the lower networks 400-1 to 400-n are referred to as the lower network 400 unless otherwise specified.

FIG. 2 is a functional block diagram showing a functional configuration of the OLT 100.
The OLT 100 includes a CPU (Central Processing Unit), a memory, an auxiliary storage device, and the like connected by a bus, and executes an OLT control program. The OLT 100 functions as an apparatus including the wavelength multiplexer / demultiplexer 110, the optical receiver 120, the optical transmitter 130, and the controller 140 by executing the OLT control program.
Note that all or part of the functions of the OLT 100 may be realized using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA). The OLT control program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built in the computer system. The OLT control program may be transmitted via a telecommunication line.

  The wavelength multiplexer / demultiplexer 110 includes a wavelength filter corresponding to the wavelength of each optical signal in the upstream direction and the downstream direction. The wavelength multiplexer / demultiplexer 110 extracts the optical signal transmitted from the ONU 200 by separating the wavelength corresponding to the upstream optical signal from the optical signal transmitted by the optical fiber, and outputs the optical signal to the optical receiver 120. Further, the wavelength multiplexer / demultiplexer 110 synthesizes an optical signal having a wavelength corresponding to the downlink direction output from the optical transmission unit 130 into an optical signal transmitted through an optical fiber, and transmits the optical signal to the ONU 200.

The optical receiving unit 120 receives the optical signal output from the wavelength multiplexer / demultiplexer 110, demodulates the optical signal into a data signal, and outputs the data signal to the control unit 140.
The optical transmission unit 130 receives the transmission signal output from the control unit 140 and converts it into an optical signal having a wavelength corresponding to the downlink direction. Then, the optical transmission unit 130 outputs the converted optical signal to the wavelength multiplexer / demultiplexer 110.
The control unit 140 performs control related to communication with the ONU 200 and communication with the upper network 300. The control unit 140 includes a transmission permission information generation unit 141, a filling permission time calculation unit 142, and an extended GATE generation unit 143.

Transmission permission information generating section 141 calculates a transmission start time t and the transmission permitted time _{T P} and notifies the ONU 200. The calculation of the transmission start time t and the transmission permitted time _{T P} uses existing conventional method based on the status of communication between the OLT100 the ONU 200. For example, the transmission permission information generating section 141, based on the communication conditions, such as size and communication speed of the communication overhead, calculates the transmission start time t and the transmission permitted time T _P. The transmission permission information generation unit 141 outputs the calculated transmission start time t to the extended GATE generation unit 143. The transmission permission information generation unit 141 outputs the calculated transmission permission time _TP to the filling permission time calculation unit 142 and the extended GATE generation unit 143.

Replenishing permission time calculating unit 142 calculates the replenishment permission time T _'P to notify the ONU200 based on the transmission permitted time _{T P} calculated by the transmission permission information generating section 141. Replenishing permission time T _'P, of the transmission permitted time T _P, representing the time used to transmit the actual data. That the filling rate the rate at which the filling allow time T _'P occupied in the transmission permitted time T _P. The closer the filling rate is to “1”, the higher the percentage of actual data in the burst signal, and the closer to “0”, the smaller the percentage of actual data in the burst signal. Therefore, the higher the filling rate, the higher the possibility of collision between superimposed signals, and the smaller the filling rate, the lower the possibility of collision between superimposed signals. That is, the OLT 100 can control the substantial superposition rate in the signal superposition transmission by controlling the filling rate of the signal transmitted by the ONU 200.

The filling permission time calculation unit 142 calculates the filling permission time T ′ _P according to the communication status between the OLT 100 and the ONU 200. For example, the filling permission time calculation unit 142 assigns a shorter filling permission time T ′ _P to the ONU 200 that transmits a burst signal having a high collision occurrence frequency, and performs control so as to suppress the collision occurrence frequency. Good. Further, for example, the filling permission time calculating unit 142 may assign a longer filling permission time T ′ _P to the ONU 200 that transmits a burst signal having a low collision occurrence frequency, and control the direction so as to increase the transmission efficiency. . Replenishing permission time calculating unit 142 outputs the replenishment permission time T _'P calculated for extended GATE generator 143.

The extended GATE generation unit 143 generates an extended GATE frame. Expansion The GATE frame is a GATE frame area for storing the replenishment permission time T _'P normal GATE frame is added. The extended GATE generation unit 143 generates an extended GATE frame including the transmission start time t, the transmission permission time _TP, and the filling permission time T ′ _P output from the transmission permission information generation unit 141 and the filling permission time calculation unit 142. . The extended GATE generation unit 143 outputs the generated extended GATE frame to the optical transmission unit 130 and transmits it to the ONU 200 that is the transmission target of the GATE frame.

FIG. 3 is a functional block diagram showing the functional configuration of the ONU 200.
The ONU 200 includes a CPU, a memory, an auxiliary storage device, and the like connected by a bus, and executes an ONU control program. The ONU 200 functions as a device including the wavelength multiplexer / demultiplexer 210, the optical receiver 220, the optical transmitter 230, the signal discriminator 240, and the transmission controller 250 by executing the ONU control program.
All or some of the functions of the ONU 200 may be realized using hardware such as an ASIC, a PLD, or an FPGA. The ONU control program may be recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built in the computer system. The ONU control program may be transmitted via a telecommunication line.

  The wavelength multiplexer / demultiplexer 210 includes a wavelength filter corresponding to the wavelength of each optical signal in the upstream direction and the downstream direction. The wavelength multiplexer / demultiplexer 210 extracts the optical signal transmitted from the OLT 100 by separating the wavelength corresponding to the upstream optical signal from the optical signal transmitted by the optical fiber, and outputs the optical signal to the optical receiver 220. Further, the wavelength multiplexer / demultiplexer 210 synthesizes an optical signal having a wavelength corresponding to the downlink direction output from the optical transmission unit 230 into an optical signal transmitted by an optical fiber, and transmits the optical signal to the OLT 100.

The optical receiver 220 receives the optical signal output from the wavelength multiplexer / demultiplexer 210, demodulates the optical signal into a data signal, and outputs the data signal to the signal discriminator 240.
The optical transmission unit 230 receives the transmission signal output from the transmission control unit 250 and converts it into an optical signal having a wavelength corresponding to the downlink direction. Then, the optical transmission unit 230 outputs the converted optical signal to the wavelength multiplexer / demultiplexer 210.

  The signal discriminating unit 240 discriminates the signal input from the light receiving unit 220. In the signal transmitted from the OLT 100, a signal to be transmitted to each ONU 200 is multiplexed. The signal discriminating unit 240 determines whether or not the received signal (frame) is addressed to itself. Here, the signal addressed to itself is a signal transmitted by broadcast from the OLT 100, or a signal whose LLID (Logical Link ID) stored in the frame matches its own LLID. In the case of a signal transmitted by broadcast, a predetermined address corresponding to broadcast is stored in the destination address. The signal discriminating unit 240 can determine whether or not the signal is transmitted by broadcasting by referring to the destination address.

  Furthermore, when the received signal is a signal transmitted to itself, the signal discriminating unit 240 determines the type of the received signal. For example, when the type of information stored in the frame of the signal transmitted by broadcasting indicates that it is an extended GATE frame, the signal discriminating unit 240 uses the received extended GATE frame as an extended GATE analyzing unit 251 of the transmission control unit 250. Output to.

  The transmission control unit 250 receives a frame transmitted from the lower network 400 and controls communication to be transmitted to the OLT 100. The transmission control unit 250 includes an extended GATE analysis unit 251, a transmission signal storage unit 252, and a transmission signal generation unit 253.

The extended GATE analysis unit 251 analyzes the extended GATE frame transmitted from the OLT 100. The extended GATE analyzing unit 251 acquires the extended GATE frame output from the signal discriminating unit 240. The extended GATE analysis unit 251 acquires the transmission start time t, the transmission permission time _TP, and the filling permission time T ′ _P from the acquired extended GATE frame. Extended GATE analysis unit 251 outputs the acquired information of the replenishing permission time T _'P was the transmission signal storage unit 252. Further, the extended GATE analysis unit 251 outputs the acquired transmission start time t and transmission permission time _TP to the transmission signal generation unit 253.

The transmission signal accumulation unit 252 is a buffer that temporarily accumulates transmission signals transmitted from the lower network 400 and waiting to be transmitted to the OLT 100. Transmission signal storage unit 252, based on the replenishment permission time output from the extended GATE analysis unit 251 T _'P, and outputs a transmission signal which is accumulated in the transmission signal generator 253. Specifically, the transmission signal storage unit 252 outputs a possible frame transmitted to the transmission signal generating unit 253 within the replenishment permission time T _'P.

The transmission signal generation unit 253 adds a dummy bit to the frame output from the transmission signal accumulation unit 252. The number of dummy bits added to the frame is a signal length that can be transmitted within the time difference between the transmission permission time T _P and the filling permission time T ′ _P.

  The transmission signal generation unit 253 distributes the dummy bits to the entire burst signal by performing an encoding process such as interleaving on the generated burst signal. By this encoding process, the effect of fluctuation of the filling rate on the frequency of occurrence of signal collision is made uniform throughout the burst signal. The transmission signal generation unit 253 starts transmission of the burst signal subjected to the encoding process at the transmission start time t.

FIG. 4 is a schematic diagram illustrating a state in which a burst signal transmitted to the OLT 100 is generated by the transmission control unit 250.
In FIG. 4, reference numeral 601 represents a set of frames accumulated in the transmission signal accumulation unit 252 (hereinafter referred to as “accumulated frames”). FIG. 4 shows a state in which frames F _{1 to} F _{n + 1} are stored in the transmission signal storage unit 252. Note that the numbers assigned to the frames indicate the order of accumulation in the transmission signal accumulation unit 252, and the frames are transmitted in this order. The width of each frame represents the time taken to transmit the frame, that is, is proportional to the signal length of the frame.

Transmission signal storage unit 252, based on the replenishment permission time output from the extended GATE analysis unit 251 T _'P, and outputs a transmission signal which is accumulated in the transmission signal generator 253. In the case of the example in FIG. 4, the transmission signal accumulation unit 252 outputs the frames from the frame F ₁ to the frame F _n in the accumulation frame 601 to the transmission signal generation unit 253.

Transmission signal generating unit 253 adds dummy bits to frames from frames F ₁ outputted from the transmission signal storage unit 252 to the frame F _n, and generates a burst signal of transmittable signal length at the transmission permitted time T _P . In the case of the example of FIG. 4, the transmission signal generation unit 253 generates the burst signal 602 by adding the dummy bit D. The transmission signal generation unit 253 performs an encoding process on the generated burst signal 602 to generate a burst signal 603.

FIG. 5 is a flowchart showing a flow of processing in which the ONU 200 transmits a frame to the OLT 100 based on the extended GATE frame.
First, the ONU 200 receives a burst signal transmitted from the OLT 100. The received burst signal is input to the signal discriminator 240. The signal discriminating unit 240 acquires a frame addressed to itself from the input burst signal. The signal discriminating unit 240 acquires an extended GATE frame from the acquired frame (step S101), and outputs it to the extended GATE analysis unit 251.

The extended GATE analysis unit 251 acquires the transmission start time t, the transmission permission time _TP, and the filling permission time T ′ _P from the extended GATE frame output from the signal discrimination unit 240 (Step S102). Extended GATE analysis unit 251 outputs the acquired information of the replenishing permission time T _'P was the transmission signal storage unit 252. Further, the extended GATE analysis unit 251 outputs the acquired transmission start time t and transmission permission time _TP to the transmission signal generation unit 253.

The transmission signal accumulation unit 252 outputs a frame that can be transmitted within the filling permission time T ′ _P output from the extended GATE analysis unit 251 among the accumulated transmission signals to the transmission signal generation unit 253 (step S103). .

  The transmission signal generation unit 253 adds a dummy bit to the frame output from the transmission signal accumulation unit 252 (step S104). The transmission signal generation unit 253 generates a burst signal to be transmitted to the OLT 100 by performing an encoding process such as interleaving on the frame to which the dummy bits are added (step S105). The transmission signal generator 253 starts transmission of the generated burst signal at the transmission start time t (step S106).

  The OLT 100 of the embodiment configured as described above notifies the ONU 200 of the amount (filling rate) of actual data that can be included in the burst signal transmitted to the OLT 100 by extending the GATE frame. With this extended GATE frame, the OLT 100 can control the filling rate that functions as a substantial superposition rate for each ONU 200 in signal superposition transmission in TDMA.

  The OLT 100 and the ONU 200 in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system serving as a server or a client in that case may be included and a program held for a certain period of time. Further, the program may be a program for realizing a part of the above-described functions, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system. It may be realized using a programmable logic device such as an FPGA.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 100 ... OLT (Optical Line Terminal: Station side optical line termination | terminus device), 110 ... Wavelength multiplexer / demultiplexer, 120 ... Optical receiving part, 130 ... Optical transmission part, 140 ... Control part, 141 ... Transmission permission information generation part, 142 ... Filling permission time calculation unit, 143 ... Extended GATE generation unit, 200, 200-1 to 200-n ... ONU (Optical Network Unit: subscriber side optical line terminator), 210 ... Wavelength multiplexer / demultiplexer, 220 ... Optical Receiving unit, 230 ... optical transmission unit, 240 ... signal discrimination unit, 250 ... transmission control unit, 251 ... extended GATE analysis unit, 252 ... transmission signal storage unit, 253 ... transmission signal generation unit, 300 ... upper network, 400, 400 -1 to 400-n: lower network, 500 ... optical communication path, 601 ... accumulated frame, 602, 603, 90, 90-1 to 90-4 ... burst signal 901 ... Preamble signal, 902, 902-1 to 902-3 ... LLID (Logical Link ID), 903, 903-1 to 903-3 ... MAC (Media Access Control) frame, 904, 904-1 to 904-2 ... IFG (Inter Frame Gap)

Claims (4)

A station-side optical line terminator and a subscriber-side optical line terminator for communicating via an optical communication path, wherein the station-side optical line terminator indicates a transmission timing and a transmission permission time of an optical signal in the subscriber-side light An optical communication system in which the subscriber-side optical line terminator transmits the optical signal to the station-side optical line terminator during the transmission permission time from the notified timing. And
The station side optical line terminator is:
A communication unit that communicates with the subscriber-side optical line termination device;
A generating unit that calculates a filling permission time that can be used for transmission of actual data among the transmission permission times, and generates a notification signal for notifying the filling permission time to the subscriber-side optical line termination device; With
The subscriber side optical line terminator is:
A communication unit that communicates with the station-side optical line termination device;
An analysis unit for analyzing the notification signal and obtaining the filling permission time;
A generation unit that generates a transmission signal to be transmitted to the station side optical network unit based on the filling permission time ,
The generation unit of the subscriber-side optical network terminating device adds a dummy signal having a signal length that can be transmitted at a time difference between the transmission permission time and the filling permission time to the transmission signal, and the dummy signal is added. The encoded transmission signal is encoded.
Optical communication system. In the optical communication system, when performing signal superimposition transmission for superimposing optical signals transmitted by a plurality of subscriber-side optical line terminators,
The station side optical line termination device controls a superposition rate in signal superposition transmission by changing the filling permission time,
The optical communication system according to claim 1 . A station-side optical line terminator and a subscriber-side optical line terminator for communicating via an optical communication path, wherein the station-side optical line terminator indicates a transmission timing and a transmission permission time of an optical signal in the subscriber-side light In the optical communication system, the subscriber side optical line terminator transmits the optical signal to the station side optical line terminator during the transmission permission time from the notified timing.
The station side optical line terminator is
A communication step of communicating with the subscriber side optical line termination device;
A generation step of calculating a filling permission time that can be used for transmission of actual data among the transmission permission times, and generating a notification signal for notifying the filling permission time to the subscriber-side optical line termination device; Run ,
The subscriber side optical line terminator is:
A communication step of communicating with the station side optical line termination device;
Analyzing the notification signal and obtaining the filling permission time;
Perform a generation step of generating a transmission signal to be transmitted to the station-side optical network unit based on the replenishment permission time,
In the generation step executed by the subscriber-side optical line termination device, a dummy signal having a signal length that can be transmitted at a time difference between the transmission permission time and the filling permission time is added to the transmission signal, and the dummy signal The encoding process is performed on the transmission signal to which is added.
Control method. A station-side optical line terminator and a subscriber-side optical line terminator for communicating via an optical communication path, wherein the station-side optical line terminator indicates a transmission timing and a transmission permission time of an optical signal in the subscriber-side light A subscriber station optical network terminating device transmits the optical signal to the station optical network terminating device during the transmission permission time from the notified timing. A customer side optical line termination device,
A communication unit that communicates with the station-side optical line termination device;
Analyzing the signal transmitted from the station side optical line terminator, and obtaining the filling permission time that can be used for transmission of actual data among the transmission permission time,
A generation unit that generates a transmission signal to be transmitted to the station side optical network unit based on the filling permission time ,
The generation unit adds a dummy signal having a signal length that can be transmitted at a time difference between the transmission permission time and the filling permission time to the transmission signal, and encodes the transmission signal to which the dummy signal is added. I do,
A computer program for causing a computer to function as a subscriber-side optical line terminator.

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