JP2015082772A - Optical communication system, signal transmission control method, and subscriber side optical line termination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a probability of succeeding in normal reception of registration request signals if collision occurs between the registration request signals received from a plurality of subscriber side optical line termination devices.SOLUTION: An optical communication system comprises a station side optical line termination device and a subscriber side optical line termination device connected with the station side optical line termination device via an optical communication path. The subscriber side optical line termination device randomly determines optical signal output power at a time of transmitting a registration request signal in response to reception of a registration request transmission control signal transmitted by the station side optical line termination device, and transmits the registration request signal to the station side optical line termination device by the determined optical signal output power.

Description

  The present invention relates to an optical communication system, a signal transmission control method, and a subscriber-side optical line terminator.

  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.

  Among the PONs, those in which the OLT and the ONU communicate with each other using an Ethernet (registered trademark, hereinafter the same) frame are referred to as EPON (Ethernet (registered trademark, the same hereinafter) PON).

  Among EPONs, GE-PON (Gigabit Ethernet PON) with a transmission speed of 1 Gbps is a high-speed and inexpensive FTTH (Fiber To The Home) network structure for access optical communication that draws optical fiber directly into the subscriber's home. System) service can be provided. For this reason, GE-PON is widely used especially in Japan. Recently, a standard specification of 10G-EPON having a transmission rate increased to 10 Gbps has been studied.

In recent years, studies have been made on optical repeaters for PON, and it has become possible to expand the standard and increase the number of branches. Specifically, conventional PONs were often used with 32 branches or less due to optical signal intensity restrictions, but multi-branch connections such as 1000 branches became possible.
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, upstream communication is performed by time division multiple access. By controlling the transmission timing of each ONU by the OLT, a plurality of ONUs can perform time division communication with the OLT. Similarly, 10G-EPON upstream communication is performed by time division multiple access. In 10G-EPON, a method in which a plurality of ONUs having different uplink transmission rates can be connected to one OLT is being studied. At this time, uplink communication is realized by time division multiple access even between ONUs of different speeds.

In many PONs in which uplink communication is performed by time-division multiple access, in order to efficiently use the uplink communication band, a band permitting uplink communication for each ONU is set as a communication status. It has a dynamic bandwidth allocation function that dynamically changes according to the frequency.
Here, the bandwidth for each ONU in the PON can be allocated, for example, by the OLT calculating a transmission permission amount for each ONU and securing the transmission time zone exclusively. The ONU transmits an upstream signal only in the time zone assigned by the OLT. For this reason, the waiting time for waiting for the assigned time zone is added to the transmission delay time.

  In EPON, a protocol called MPCP (Multi Point-Control Protocol) for controlling communication between a plurality of ONUs by one OLT is defined as a standard. As MPCP, there are known Discovery Processing for detecting an unregistered ONU and REPORT Processing / GATE Processing for controlling the transmission timing of an upstream signal transmitted by the ONU.

  In the EPON, when the ONU is connected to the PON, the OLT discovers the ONU, assigns an LLID (Logical Link ID) to the ONU, and automatically establishes a communication link. This function is called P2MP discovery (Point to multi-point Discovery). MPCP Discovery Processing is a protocol for realizing P2MP discovery.

The sequence diagram of FIG. 5 shows a communication procedure in P2MP discovery processing as Discovery Processing.
In the Discovery Processing, first, the OLT transmits a Discovery GATE frame, which is a GATE frame storing Discovery Information, to each ONU, and notifies the transmission timing (Step S1).
The GATE frame is a frame for notifying the ONU of control information related to transmission such as transmission timing, and the Discovery GATE frame is a frame for notifying the unregistered ONU of control information indicating the transmission timing of the REGISTER_REQ frame. The GATE frame is transmitted using Messages sent on broadcast cannel.

  Next, when the ONU not registered in the OLT receives the Discovery GATE frame, it waits for a random delay time (Random delay) for collision avoidance, and then transmits a REGISTER_REQ frame (step S2). The REGISTER_REQ frame is transmitted using Messages sent on broadcast cannel. The OLT sets the Discovery Window only for a time during which the REGISTER_REQ frame from the ONU may be received, and receives the REGISTER_REQ frame from each unregistered ONU during the set Discovery Window period.

Next, in response to reception of the REGISTER_REQ frame, the OLT newly registers an LLID that is an identifier of the ONU (or UNI port) that is the transmission source of the REGISTER_REQ frame. Then, the registered LLID is notified by a REGISTER frame (step S3). The REGISTER frame is transmitted using Messages sent on broadcast channel.
In this way, when the LLID is notified from the OLT to the ONU, the OLT and the ONU can execute communication using the LLID. That is, a link is established between the OLT and the ONU.

Subsequently, the OLT notifies the uplink transmission timing by the GATE frame (step S4), and the ONU returns REGISTER_ACK according to the notified timing (step S5).
The P2MP discovery process is realized by the processes in steps S1 to S5. This GATE frame and REGISTER_ACK are transmitted using Messages sent on unicast channels.
Thus, communication as Discovery Processing is executed between the OLT and the ONU (see, for example, Non-Patent Document 1).

The timing chart of FIG. 6 shows an example of transmission / reception timings of the Discovery GATE frame and the REGISTER_REQ frame in the P2MP discovery process. In correspondence with FIG. 5, transmission / reception of the Discovery GATE frame shown in FIG. 6 corresponds to step S1, and transmission / reception of the REGISTER_REQ frame corresponds to step S2.
Moreover, ONU200-k and ONU200-n shown by the figure each show one of several ONU. In the description of FIG. 6, a plurality of ONUs including the ONU 200-k and ONU 200-n are described as ONU 200 unless otherwise distinguished.

In FIG. 6, first, the OLT 100 transmits a Discovery GATE frame to each ONU 200 by broadcasting at time t0. Discovery GATE frame transmitted as described above, it includes a transmission permitted time _{T G,} the information specifying the start time t1 of the transmission permitted time _{T G} as control information.

In response to receiving the Discovery GATE frame, the unregistered ONU 200 transmits a REGISTER_REQ frame at random timing at a transmission permission time _TG that starts from the start time t1 specified by the Discovery GATE frame. When the communication distance of the ONU 200-n is the longest communication distance in the allowable range, the period according to the time length T _D0 shown in the figure is the Discovery Window. Start timing of the period of the Discovery Window is the start time t1 in OLT 100, the end timing is the time delayed according to the propagation time until the OLT 100 from the end time of the transmission permitted time _{T G} in ONU 200-n. That is, the Discovery Window is a period during which a REGISTER_REQ frame from the unregistered ONU 200 is preferentially received.

The time length T _D0 of the Discovery Window period is set based on the timing at which the OLT 100 transmits the Discovery GATE frame. During the Discovery Window period, the OLT performs control so that the registered ONU does not perform uplink transmission to the OLT.
For the EPON upstream communication, the OLT calculates the upstream transmission data amount of each ONU, and notifies the calculated transmission data amount, thereby performing bandwidth control so as to secure the transmission time for each ONU. . The Discovery Window period is a period during which a REGISTER_REQ frame from an unregistered ONU is received. In view of this, during the Discovery Window period, the OLT performs bandwidth control so that uplink transmission by registered ONUs is not performed. Thereby, it is possible to avoid a collision between a signal transmitted from a registered ONU and a REGISTER_REQ frame transmitted from an unregistered ONU.

IEEE std 802.3-2012 SECTION FIVE

If a REGISTER_REQ frame collision occurs in the P2MP discovery processing sequence, the collided REGISTER_REQ frame is discarded. In this case, for the ONU that is the source of the discarded REGISTER_REQ frame, the P2MP discovery sequence is not completed, and the link with the OLT is not established.
In this case, the ONU that is the transmission source of the collided REGISTER_REQ frame needs to perform registration processing again by the next P2MP discovery processing.
In particular, when the transmission permission time _TG is short or when the number of unregistered ONUs to establish a link is large, the frequency of collision increases, until the ONU can start communication after the P2MP discovery process is completed. May take a long time.

In communication systems, in general, the shorter the time from link establishment to the start of communication, and the shorter the delay time, the higher the communication performance.
The interval at which the P2MP discovery process is executed in EPON is as long as about 0.1 to 1.5 seconds. For this reason, even if only one retry occurs in the P2MP discovery process, the influence on the delay is great. Furthermore, when the P2MP discovery process is executed simultaneously with a large number of ONUs, such as when the system is started up, the frequency of REGISTER_REQ frame signal collision increases. In such a state, there may be two or more retries, and the delay further increases.

  The present invention has been made in view of such circumstances, and increases the probability of successful successful reception of a registration request signal when a collision occurs in registration request signals received from a plurality of subscriber-side optical line terminators. For the purpose.

  One aspect of the present invention includes a station-side optical line terminator, and a subscriber-side optical line terminator connected to the station-side optical line terminator via an optical communication path. Transmits a registration request signal for requesting registration of the station side optical line terminator by the station side optical line terminator in response to reception of a registration request transmission control signal transmitted from the station side optical line terminator. An optical signal output power determination unit that randomly determines an optical signal output power at the time, and an optical signal that transmits a registration request signal to the station-side optical line termination device by the optical signal output power determined by the optical signal output power determination unit An optical communication system including a transmission unit.

  One aspect of the present invention is a signal transmission control method in an optical communication system including a station side optical line termination device and a subscriber side optical line termination device connected to the station side optical line termination device via an optical communication path. The subscriber side optical line terminator has the optical signal output power determination unit in response to reception of a registration request transmission control signal transmitted from the station side optical line terminator. A step of randomly determining an optical signal output power when transmitting a registration request signal for requesting registration of the station side optical line terminator, and an optical signal transmitter determined by the optical signal output power determiner And a step of transmitting a registration request signal to the station side optical network unit by using optical signal output power.

  One aspect of the present invention is a subscriber-side optical line terminator connected to a station-side optical line terminator via an optical communication path, and a registration request transmission control signal transmitted from the station-side optical line terminator. In response to reception, an optical signal output power determination unit that randomly determines an optical signal output power when transmitting a registration request signal for requesting registration of the station side optical line termination device by the station side optical line termination device; A subscriber-side optical line terminating device comprising: an optical signal transmitting unit that transmits a registration request signal to the station-side optical line terminating device based on the optical signal output power determined by the optical signal output power determining unit.

  As described above, according to the present invention, there is an effect that the probability of successful reception of a registration request signal when a collision occurs in registration request signals received from a plurality of subscriber-side optical line terminators increases. It is done.

It is a figure which shows the structural example of the optical communication system in this embodiment. It is a figure which shows an example of the transmission / reception timing of the REGISTER_REQ frame according to transmission of a Discovery GATE frame in the P2MP discovery process in this embodiment. It is a figure which shows the structural example of ONU in this embodiment. It is a flowchart which shows the example of a process sequence which ONU in this embodiment performs in relation to transmission of a REGISTER_REQ frame. It is a sequence diagram which shows the example of a communication procedure in a P2MP discovery process. It is a figure which shows an example of the transmission / reception timing of a Discovery GATE frame and a REGISTER_REQ frame in a P2MP discovery process.

FIG. 1 shows a configuration example of an optical communication system in the present embodiment. The optical communication system shown in the figure corresponds to, for example, 10G-EPON.
The optical communication system shown in FIG. 1 includes 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, the ONUs 200-1 to 200-n are described as ONUs 200 unless otherwise distinguished.

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

  The ONU 200 is an optical line terminating device installed on the subscriber side. A lower network 400 (400-1 to 400-N) is connected to the downstream side of the ONU 200 (200-1 to 200-n). The lower network 400 includes network devices such as a personal computer used at a subscriber's home.

In the optical communication system configured as described above, the ONU 200 that is not registered on the OLT 100 side cannot communicate with the OLT 100 because a link with the OLT 100 is not established. Therefore, for the ONU 200 that is not registered in the OLT 100, it is necessary to establish a link with the OLT 100 to enable communication.
For this purpose, a P2MP discovery process according to the procedure shown in FIG. 5 is executed between the OLT 100 and the unregistered ONU 200.

The OLT 100 broadcasts the Discovery GATE frame to all ONUs 200 connected via the optical communication path 500 in step S1 of FIG. In the Discovery GATE frame, a transmission permission time _TG and a start time t1 of the transmission permission time _TG are stored. The transmission permission time _TG is a time length of a period during which transmission of the REGISTER_REQ frame by the ONU 200 is permitted.
When the REGISTER_REQ frame is normally transmitted / received in step S2 of FIG. 5, the OLT 100 and the ONU 200 execute the processes after step S3 of FIG.

When transmitting the REGISTER_REQ frame, the ONU 200 transmits the REGISTER_REQ frame at a timing (random delay time) determined at random in the transmission permission time _TG to avoid collision as described in FIG. Yes. However, particularly in a situation where there are a large number of unregistered ONUs 200, the number of REGISTER_REQ frames transmitted during the limited transmission permission time _TG becomes large, so the probability that the REGISTER_REQ frames collide with each other increases.
FIG. 6 shows an example in which the REGISTER_REQ frame Rk transmitted from the ONU 200-k and the REGISTER_REQ frame Rn transmitted from the ONU 200-n collide with each other.

  When a collision occurs in the REGISTER_REQ frame, for example, when the reliability (for example, error rate) of the collision part of the REGISTER_REQ frame in which the collision occurs is below a certain level, the collided REGISTER_REQ frame is discarded. When the REGISTER_REQ frame is discarded in this way, the ONU 200 that is the transmission source of the collided REGISTER_REQ frame is not registered in the OLT 100, and therefore communication for retry is executed in the next P2MP discovery process. Such a retry causes a delay in communication time, which causes a deterioration in communication performance in an optical communication system, for example.

Therefore, in the present embodiment, the ONU 200 is configured to randomly change the output power (optical signal output power) of the optical signal at the time of transmission when transmitting the REGISTER_REQ frame in response to receiving the Discovery GATE frame. The This improves the probability that the REGISTER_REQ frame is normally received when a collision occurs in the REGISTER_REQ frame received by the OLT 100.
In the present embodiment, normal reception means that the REGISTER_REQ frame is normally restored by processing such as demodulation and error correction after reception.

The timing chart of FIG. 2 shows an example of transmission / reception timings of the Discovery GATE frame (registration request transmission control signal) and the REGISTER_REQ frame (registration request signal) in the P2MP discovery process in the present embodiment.
The OLT 100 transmits a Discovery GATE frame to each ONU 200 by broadcasting at time t0. Discovery GATE frame includes a transmission permitted time _{T G,} the information specifying the start time t1 of the transmission permitted time _{T G.} The transmission of the Discovery GATE frame by the OLT 100 corresponds to step S1 in correspondence with FIG.

After transmitting the Discovery GATE frame, the OLT 100 sets a Discovery Window period with a time length T _D0 with the start time t1 as the start time. The OLT 100 accepts reception of a REGISTER_REQ frame during the Discovery Window period.

The ONU 200 transmits a REGISTER_REQ frame in response to the reception of the Discovery GATE frame, as shown as Step S2 in FIG.
When conforming to the standard, each ONU transmits a REGISTER_REQ frame with a predetermined optical signal output power. Further, each time an ONU receives a Discovery GATE frame, it transmits a REGISTER_REQ frame with a predetermined optical signal output power.

  On the other hand, the ONU 200 of the present embodiment randomly determines the optical signal output power when transmitting the REGISTER_REQ frame in response to the reception of the Discovery GATE frame. Then, the ONU 200 transmits a Discovery GATE frame with the determined optical signal output power.

  In FIG. 2, the transmission result of the REGISTER_REQ frame of the ONU 200-k and ONU 200-n when each ONU 200 randomly determines the optical signal output power as described above is shown. In the figure, a result is shown in which the ONU 200-k transmits a REGISTER_REQ frame Rk with a high optical signal output power, and the ONU 200-n transmits a REGISTER_REQ frame Rn with a low optical signal output power.

  FIG. 2 shows a state in which the REGISTER_REQ frame Rk and the REGISTER_REQ frame Rn received by the OLT 100 collide with each other due to overlapping of reception periods. However, the REGISTER_REQ frame Rk is transmitted with high optical signal output power, and the REGISTER_REQ frame Rn is transmitted with high optical signal output power. For this reason, the reception level of the REGISTER_REQ frame Rk received by the OLT 100 is high, and the reception level of the REGISTER_REQ frame Rn is low. That is, the REGISTER_REQ frame Rk and the REGISTER_REQ frame Rn have a reception level difference of a certain level or more.

  When there is a reception level difference of a certain level or more between the plurality of REGISTER_REQ frames in the collision state, for example, there is a high possibility that the REGISTER_REQ frame with the higher reception level can be normally received.

  In the example of FIG. 2, the probability that the REGISTER_REQ frame Rk is normally received is high. When the REGISTER_REQ frame Rk is normally received, the OLT 100 registers the ONU 200-k that is the transmission source of the REGISTER_REQ frame Rk by executing the processing from step S3 in FIG.

Note that according to the above description, in the transmission / reception sequence (P2MP discovery) of the Discovery GATE frame and the REGISTER_REQ frame shown in FIG. 2, the REGISTER_REQ frame transmitted by the ONU 200-n is discarded without being normally received. In this case, the ONU 200-n is not registered in the OLT 100.
However, for example, when the P2MP discovery sequence is repeated after the next time, the REGISTER_REQ frame transmitted by the ONU 200-n is normally received and registered.

As described above, in the present embodiment, by transmitting the REGISTER_REQ frame with the optical signal output power randomly determined by the ONU 200, the probability that the reception level difference of the REGISTER_REQ frame received by the OLT 100 becomes large is increased. By increasing the probability that the reception level difference becomes large in this way, even if a collision occurs in the REGISTER_REQ frame, the probability that a part of the REGISTER_REQ frame is normally received is increased.
Thereby, the time until all unregistered ONUs 200 complete the registration request process is shortened, and deterioration of communication quality can be suppressed.

In the present embodiment, the probability of normal reception of the REGISTER_REQ frame is improved by changing the optical signal output power when transmitting the REGISTER_REQ frame on the ONU 200 side. The OLT 100 may transmit a Discovery GATE frame in accordance with the standard, and execute processing according to reception of the REGISTER_REQ frame. That is, the OLT 100 according to the present embodiment can be used as it is based on the standard.
Further, the REGISTER_REQ frame in the present embodiment also changes only the optical signal output power at the time of transmission, and the structure as the REGISTER_REQ frame is not particularly changed from the standard. That is, in the present embodiment, a format conforming to the standard can be used for the REGISTER_REQ frame.

  Next, a configuration example of the ONU 200 according to the present embodiment will be described with reference to FIG. The ONU 200 shown in the figure includes a wavelength multiplexer / demultiplexer 201, an optical receiver 202, a controller 203, a user data transmitter 204, and an optical signal transmitter 205.

Similar to the wavelength multiplexer / demultiplexer 201 of the OLT 100, the wavelength multiplexer / demultiplexer 201 includes a wavelength filter corresponding to the wavelength of each optical signal in the upstream direction and the downstream direction. The wavelength multiplexer / demultiplexer 201 extracts the optical signal transmitted from the OLT 100 by separating the wavelength corresponding to the downstream optical signal from the optical signal transmitted by the optical fiber, and outputs the optical signal to the optical receiving unit 202.
The wavelength multiplexer / demultiplexer 201 synthesizes an optical signal having a wavelength corresponding to the upstream direction output from the optical signal transmission unit 205 into an optical signal transmitted by an optical fiber, and transmits the optical signal to the OLT 100.

  The optical receiving unit 202 demodulates the optical signal input from the wavelength multiplexer / demultiplexer 201 into a data signal and outputs the data signal to the control unit 203.

The control unit 203 executes control related to communication with the OLT 100 and communication with the lower network 400.
The user data transmission unit 204 receives user data transmitted from the lower network 400 to the ONU 200 and passes it to the control unit 203. In addition, the user data transmission unit 204 transmits the user data transferred from the control unit 203 to the lower network 400.

The optical signal transmission unit 205 receives the transmission signal (user data, REPORT frame, REGISTER_REQ frame, etc.) output from the transmission signal storage unit 234 of the control unit 203 and converts it into an optical signal having a wavelength corresponding to the upstream direction. The converted optical signal is supplied to the wavelength multiplexer / demultiplexer 201 and transmitted to the OLT 100.
In addition, when transmitting the REGISTER_REQ frame to the OLT 100, the optical signal transmission unit 205 of the present embodiment transmits the optical signal output power determined by the optical signal output power determination unit 233 in the control unit 203.

  A configuration example of the control unit 203 will be described with reference to the same FIG. The control unit 203 shown in the figure includes a signal discrimination unit 231, a registration request signal generation unit 232, an optical signal output power determination unit 233, a transmission signal accumulation unit 234, a transmission control unit 235, and a REPORT frame generation unit 236.

The signal discriminating unit 231 discriminates the signal input from the light receiving unit 202.
In the signal transmitted from the OLT, a signal to be transmitted to each ONU is multiplexed. The signal discriminating unit 231 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 (DA). The signal discriminating unit 231 can determine whether or not the signal is transmitted by broadcasting by referring to the destination address (DA).

Furthermore, when the received signal is a signal transmitted to itself, the signal discriminating unit 231 determines the type of the received signal.
For example, when the information indicating the data (frame) type in the frame of the signal transmitted by broadcast indicates that it is a Discovery GATE frame, the signal discrimination unit 231 determines that the type of the received signal is a Discovery GATE frame. .
When the signal discriminating unit 231 determines that the Discovery GATE frame has been received, the signal discriminating unit 231 outputs the received Discovery GATE frame to the transmission control unit 235. If the signal discrimination unit 231 determines that the Discovery GATE frame has been received, the signal discrimination unit 231 notifies the registration request signal generation unit 232 and the optical signal output power determination unit 233 that the received signal is the Discovery GATE frame. Against.

Further, the signal discriminating unit 231 indicates that the received signal is a GATE frame when the information indicating the data (frame) type in the received signal frame is a GATE frame (other than the Discovery GATE frame). Is determined.
In this case, the signal discriminating unit 231 outputs the received GATE frame to the transmission control unit 235.

  The signal discriminating unit 231 determines that the received signal is user data when the information indicating the data (frame) type in the frame of the received signal addressed to the user indicates user data. In this case, the signal discriminating unit 231 transmits the received user data from the user data transmission unit 204 to the lower network 400.

The registration request signal generation unit 232 generates a REGISTER_REQ frame in response to receiving a notification from the signal discrimination unit 231 that the Discovery GATE frame has been received.
The REGISTER_REQ frame generated as described above is accumulated in the transmission signal accumulation unit 234.

The optical signal output power determination unit 233 transmits the REGISTER_REQ frame in response to the Discovery GATE frame notified of reception in response to receiving the notification that the Discovery GATE frame has been received from the signal discrimination unit 231. Determine the signal output power.
The optical signal output power determination unit 233 randomly determines the optical signal output power. As a specific example, the optical signal output power determination unit 233 may determine the optical signal output power randomly by generating a random number in a numerical range from the minimum value to the maximum value of the optical signal output power, for example.
The optical signal output power determination unit 233 outputs the determined optical signal output power to the optical signal output power change unit 252 of the optical signal transmission unit 205.

  The transmission signal accumulation unit 234 is a buffer that temporarily accumulates transmission signals waiting for transmission. The transmission signal accumulated by the transmission signal accumulation unit 234 is generated by, for example, user data transmitted from the lower network 400 via the user data transmission unit 204, the REGISTER_REQ frame generated by the registration request signal generation unit 232, and the REPORT frame generation unit 236. For example, a REPORT frame.

  The transmission control unit 235 performs transmission control according to the band (data transmission amount) notified by the GATE frame and the transmission timing. That is, the transmission control unit 235 transmits the transmission signal of the data transmission amount notified by the GATE frame among the transmission signals stored by the transmission signal storage unit 234 at the transmission timing notified by the GATE frame. 205. Thereby, the transmission signal of the data transmission amount notified by the GATE frame is transmitted to the OLT 100 at the transmission timing notified by the GATE frame.

The REPORT frame generation unit 236 generates a REPORT frame. The REPORT frame is a frame for notifying the OLT 100 from the ONU 200 of the data amount of the transmission signal waiting for transmission stored in the transmission signal storage unit 234.
The REPORT frame generation unit 236 generates a REPORT frame storing data amount information indicating the data amount of transmission signals waiting to be transmitted that are accumulated in the transmission signal accumulation unit 234.
The generated REPORT frame is temporarily stored in the transmission signal storage unit 234 and then transmitted to the OLT 100 under the control of the transmission control unit 235.

The OLT 100 that has received the REPORT frame, based on the data amount indicated by the data amount information stored in the REPORT frame and the data amount of the ONU other than the REPORT frame transmission source, should be assigned to the ONU 200 that is the transmission source of the REPORT frame. Bandwidth (data transmission amount) and transmission timing are calculated. Transmission timing calculated here, the correspondence between the Discovery GATE frame, a transmission permitted time _{T G} in FIG. 2, corresponding to the start time t1 of the transmission permitted time _{T G.}
The OLT 100 generates a GATE frame storing information on the calculated data transmission amount and transmission timing, and transmits the GATE frame to the ONU 200 that is the transmission source of the REPORT frame. Thus, depending on the GATE frame, the ONU 200 is notified of the data transmission amount and the transmission timing.

  The GATE frame received by the ONU 200 is output to the transmission control unit 235 in the control unit 203 as described above, and the transmission control unit 235 performs transmission based on the data transmission amount and the transmission timing indicated by the input GATE frame. Transmission control is performed on transmission signals waiting for transmission stored in the signal storage unit 234.

The configuration of the optical signal transmission unit 205 will be described with reference to the same FIG. The optical signal transmission unit 205 shown in the figure includes an optical transmission unit 251 and an optical signal output power change unit 252.
The optical transmission unit 251 receives the transmission signal (user data, REPORT frame, REGISTER_REQ frame, etc.) output from the transmission signal storage unit 234 of the control unit 203 and converts it into an optical signal having a wavelength corresponding to the upstream direction. The optical transmission unit 251 outputs the optical signal obtained by the conversion with a predetermined optical signal output power for transmission to the OLT 100.

  The optical signal output power change unit 252 changes the optical signal output power of the optical signal input from the optical transmission unit 251 to the optical signal output power determined by the optical signal output power determination unit 233 and sends it to the wavelength multiplexer / demultiplexer 201. Output.

A variable optical attenuator can be used for the optical signal output power changing unit 252.
Or you may comprise so that the output power of the optical signal output from the optical transmission part 251 may be changed by voltage control at the time of converting the data of a Discovery GATE frame into an optical signal in the optical transmission part 251. In this case, the function as the optical signal output power changing unit 252 can be included in the optical transmission unit 251, for example.

  When the optical signal output power set by the optical transmission unit 251 of the optical signal transmission unit 205 corresponds to the maximum value, the optical signal output power determination unit 233 replaces the optical signal output power itself with You may make it set the attenuation factor with respect to the optical signal output power corresponding to the maximum value at random. In this case, the optical signal output power changing unit 252 may attenuate the optical signal output power of the REGISTER_REQ frame input from the optical transmission unit 251 according to the attenuation rate determined by the optical signal output power determination unit 233.

  Next, an example of a processing procedure executed by the ONU 200 according to this embodiment in association with transmission of the REGISTER_REQ frame will be described with reference to the flowchart of FIG. It should be noted that the process shown in FIG.

  In the ONU 200, the signal discriminating unit 231 waits for a Discovery GATE frame to be received (step S101—NO). That is, the signal discriminating unit 231 waits until a discrimination result indicating that it is a Discovery GATE frame is obtained as a discrimination result for the received signal.

  In response to the reception of the Discovery GATE frame (step S101—YES), the registration request signal generation unit 232 generates a REGISTER_REQ frame to be transmitted in response to the Discovery GATE frame received in step S101 (step S101). S102). The generated REGISTER_REQ frame is accumulated in the transmission signal accumulation unit 234 until the transmission timing notified by the Discovery GATE frame received in step S101.

Further, the optical signal output power determining unit 233 randomly determines the optical signal output power for transmitting the REGISTER_REQ frame in response to the Discovery GATE frame received in Step S101 (Step S103).
The optical signal output power determining unit 233 sets the optical signal output power determined in step S103 in the optical signal output power changing unit 252 (step S104).

The transmission control unit 235 executes control for transmitting the REGISTER_REQ frame accumulated in the transmission signal accumulation unit 234 to the OLT 100 at a timing corresponding to the notification of the Discovery GATE frame received corresponding to step S101 (step S101). S105).
By executing such processing, the ONU 200 can transmit a REGISTER_REQ frame to the OLT 100 with random optical signal output power in response to reception of the Discovery GATE frame.

Note that 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 is recorded on a computer-readable recording medium, and the program recorded on this recording medium is read into a computer system and executed, whereby each operation of the OLT 100 and the ONU 200 is realized. May be. 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. You may implement | achieve using programmable logic devices, such as FPGA (Field Programmable Gate Array).
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the present embodiment, and includes design and the like within the scope not departing from the gist of the present invention.

  100 OLT, 200 ONU, 201 wavelength multiplexer / demultiplexer, 202 optical receiver, 203 controller, 204 user data transmitter, 205 optical signal transmitter, 231 signal discriminator, 232 registration request signal generator, 233 optical signal output Power decision unit, 234 transmission signal storage unit, 235 transmission control unit, 236 REPORT frame generation unit, 251 optical transmission unit, 252 optical signal output power change unit, 300 upper network, 400 lower network, 500 optical communication path

Claims (3)

A station-side optical line terminator, and a subscriber-side optical line terminator connected to the station-side optical line terminator via an optical communication path,
The subscriber side optical line terminator is:
In response to receiving a registration request transmission control signal transmitted from the station side optical line terminator, a registration request signal for requesting registration of the station side optical line terminator by the station side optical line terminator is transmitted. An optical signal output power determining unit that randomly determines the optical signal output power;
An optical communication system comprising: an optical signal transmission unit configured to transmit a registration request signal to the station-side optical network unit using the optical signal output power determined by the optical signal output power determination unit. A signal transmission control method in an optical communication system comprising a station side optical line termination device and a subscriber side optical line termination device connected to the station side optical line termination device via an optical communication path,
The subscriber side optical line terminator is:
The optical signal output power determining unit requests registration of the station side optical line termination device by the station side optical line termination device in response to reception of a registration request transmission control signal transmitted from the station side optical line termination device. Randomly determining an optical signal output power when transmitting a registration request signal;
A signal transmission control method comprising: an optical signal transmission unit transmitting a registration request signal to the station-side optical network unit using the optical signal output power determined by the optical signal output power determination unit. A subscriber side optical line terminator connected to a station side optical line terminator via an optical communication path,
In response to receiving a registration request transmission control signal transmitted from the station side optical line terminator, a registration request signal for requesting registration of the station side optical line terminator by the station side optical line terminator is transmitted. An optical signal output power determining unit that randomly determines the optical signal output power;
A subscriber-side optical line termination device comprising: an optical signal transmission unit that transmits a registration request signal to the station-side optical line termination device based on the optical signal output power determined by the optical signal output power determination unit.

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