JP2017034429A - Office side device and optical transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely reduce a time needed to link up a new ONU even in the case of a multiport PON system.SOLUTION: A port setting unit 13A sets a discovery window only to a selection port. A discovery control unit 13B, when performing discovery processing, transmits a discovery gate frame from the selection port selected in the port setting unit 13A, to link up the ONU on the basis of a register request frame returned in response thereto from the ONU of the selection port within the discovery window period. A collision detector unit 13C detects the occurrence of a collision between register request frames returned from a plurality of different ONUs within the discovery window period. The port setting unit 13A selects, as a selection port, a collision port in which the occurrence of the collision is detected by the collision detector unit 13C preferentially to other ports.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an OLT in an optical transmission system for transferring a frame between a plurality of ONUs (subscriber side devices: Optical Network Unit) connected via a PON (Passive Optical Network) and a host device. In particular, the present invention relates to a discovery processing technique for linking up an ONU to an OLT in response to a registration request signal from a new ONU.

  Normally, in an optical transmission system comprising a PON system such as 10G-EPON (10 Gigabit Ethernet Passive Optical Network: Ethernet is a registered trademark), an unregistered ONU to which an OLT is newly connected is discovered and a communication link is automatically established. In order to connect, a discovery process is periodically executed between the OLT and the ONU. FIG. 13 is a configuration example of a general optical transmission system (single port format). FIG. 14 is a sequence diagram illustrating the discovery process.

  In this discovery process, first, a Discovery Gate frame is broadcast from the OLT to all ONUs. In the Discovery Gate frame, a Discovery Slot is described as a period during which the ONU can be transmitted. When the new ONU receives this Discovery Gate frame, it transmits a Register Request frame for requesting link-up to the OLT within the Discovery Slot period described in the Discovery Gate frame. At this time, the ONU delays from the discovery slot start time by a random time Random Delay within a range obtained by subtracting the length of the register request frame from the discovery slot in order to avoid a collision with a register request frame transmitted from another ONU. And send a Register Request frame.

  The OLT waits for and receives a Register Request frame from the ONU only during a Discovery Window period in which a round trip time as a transmission delay is added to the Discovery Slot. After receiving the Register Request frame by the OLT, a Register frame that permits link-up is transmitted to the transmission source ONU, and the link-up is completed when a Register Ack frame that is a response to the Register frame is returned from the ONU.

In such a discovery process, each ONU transmits a Register Request frame with a delay of Random Delay in order to avoid a collision of Register Request frames from these ONUs that may occur when there are multiple new ONUs. However, when the number of new ONUs is large, there is a possibility that the collision of the Register Request frame is repeated and it takes time until the link up.
In order to solve this problem, there has conventionally been proposed a method of extending the standby period in the OLT in the next cycle, that is, the Discovery Window when a Register Request frame collision occurs (Non-patent Document 1). Thereby, since the Discovery Window after the collision becomes long, the setting range of the delay time when transmitting the Register Request frame can be expanded, and the probability of collision can be reduced. Thereby, the time required for link-up of a new ONU is shortened.

S. Bhatia, R. Bartos, "Performance of the IEEE 802.3 EPON Registration Scheme Under High Load", Proceedings of the SPIE Optics East Conference on Performance, pp. 112-122, 2004

  However, in such a conventional technique, when the optical transmission system is a multi-port PON system using an OLT having a plurality of ports, there is a possibility that a Register Request frame collides with a new ONU connected to a different port. As a result, there is a problem that the time required for link-up of the new ONU cannot be reliably reduced.

  FIG. 15 is a configuration example of a multi-port PON system. In this configuration, a plurality of ports (optical transceivers) are provided in the OLT as compared with the single port format of FIG. 13, and a plurality of ONUs are connected to each port via a splitter. At this time, as described above, when discovery processing is executed in parallel at each port, a Discovery Window period is provided for all ports at the same time.

  Therefore, for example, even if a plurality of new ONUs are connected to port 1 and a Register Request frame collision occurs, even if the Discovery window is extended in the next cycle using the above-described conventional technique, a new ONU is newly added to the other port 2. Is connected, a Register Request frame collision may occur with the new ONU of port 2. Thereby, the collision probability of the Register Request frame from the new ONU of port 1 is not reduced so much, and the time required for link-up may not be shortened.

  An object of the present invention is to provide a discovery processing technique that can reliably reduce the time required for link-up of a new ONU even in the case of a multi-port PON system.

  In order to achieve such an object, the station-side device according to the present invention has a plurality of PON ports, and frames exchanged between each ONU accommodated in these ports and a host device via an optical splitter. A station side apparatus that periodically executes a discovery process for linking up a newly connected ONU to the port, the processing target of the discovery process being selected from the ports. A port setting unit that sets a Discovery Window indicating a period for receiving a frame from the ONU only for the selected selected port, and the port selected by the port setting unit when performing the discovery process A Discovery Gate frame is transmitted from the selected port, and is returned from the ONU of the selected port within the period of the Discovery Window accordingly. A discovery control unit that links up the ONU based on the Register Request frame, and a collision detection unit that detects a collision between the Register Request frames returned from different ONUs within the Discovery Window period. And the port setting unit selects the collision port in which the occurrence of the collision is detected by the collision detection unit as a selection port with priority over other ports.

  In the configuration example of the station-side device according to the present invention, the port setting unit selects one of the selected ports in a predetermined order from the ports, and the collision detection unit detects a collision occurrence. In this case, the collision port is continuously selected as the selection port until no collision is detected at the collision port.

  In the configuration example of the station-side device according to the present invention, the port setting unit selects one of the selected ports in a predetermined order from the ports, and the collision detection unit detects a collision occurrence. In this case, the collision port is selected as the selection port at a higher frequency than other ports until the occurrence of a collision at the collision port is not detected.

  Also, in one configuration example of the station-side device according to the present invention, the port setting unit selects a plurality of the selected ports in a predetermined order from the ports, and a collision occurrence is detected by the collision detection unit. Any one or more of the collision ports are continuously selected until no collision is detected in all of the collision ports.

  Also, in one configuration example of the station-side device according to the present invention, the port setting unit selects a plurality of the selected ports in a predetermined order from the ports, and a collision occurrence is detected by the collision detection unit. One or more of the collision ports are selected as the selection port at a higher frequency than other ports.

  Also, in one configuration example of the station-side device according to the present invention, the port setting unit selects the selected port according to the predetermined order when the number of repeated selections of the collision port reaches a threshold value. It is what I did.

  Also, in one configuration example of the station-side device according to the present invention, when the port setting unit reselects the collision port as the selection port, the length of the Discovery Window set to the collision port is temporarily set. It is designed to be long.

  Also, one configuration example of the station side device according to the present invention is such that the collision detection unit receives an FCS error indicating a frame error or an error correction by FEC in the received signal of the selected port received within the period of the Discovery Window. When it is detected that the frame is not recognized from the received signal of the selected port even though the loss signal related to the selected port indicates that an optical signal is input, the frame signal detected from the received signal of the selected port When the length is longer than a specified value, or when signals are simultaneously received from a plurality of different ports included in the selected port, the occurrence of the collision at the selected port is detected.

  An optical transmission system according to the present invention includes a plurality of optical splitters, and a station-side device that performs transfer processing of frames exchanged between a plurality of ONUs connected via these optical splitters and a host device. In the optical transmission system, the station side device includes any one of the station side devices described above.

  According to the present invention, in the discovery process, a collision port in which a Register Request frame has collided is selected as a selected port preferentially over other ports, and the probability that a Register Request frame is received is increased. Accordingly, even in the case of a multi-port PON system in which a plurality of ports are provided in the OLT, it is possible to reliably reduce the time required for link-up of a new ONU.

It is a block diagram which shows the structure of the optical transmission system and OLT concerning 1st Embodiment. It is a flowchart which shows the port setting process concerning 1st Embodiment. It is a flowchart which shows a discovery process. FIG. 3 is a sequence diagram illustrating a port selection example corresponding to FIG. 2. It is a flowchart which shows the other port setting process concerning 1st Embodiment. It is a flowchart which shows the other port setting process concerning 1st Embodiment. FIG. 7 is a sequence diagram illustrating a port selection example corresponding to FIG. 6. It is a block diagram which shows the structure of the optical transmission system and OLT concerning 2nd Embodiment. It is a flowchart which shows the port setting process concerning 2nd Embodiment. FIG. 10 is a sequence diagram illustrating a port selection example corresponding to FIG. 9. It is a sequence diagram which shows the other example of port selection concerning 2nd Embodiment. It is a sequence diagram which shows the other example of port selection concerning 2nd Embodiment. It is a structural example of a general optical transmission system (single port format). It is a sequence diagram which shows a discovery process. It is a structural example of a multi-port PON system.

Next, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
First, an optical transmission system 1 and an OLT (station side apparatus) 10 according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram illustrating a configuration of the optical transmission system and the OLT according to the first embodiment.
The optical transmission system 1 includes a multiport PON system, and includes an OLT 10, a splitter 20, and an ONU (subscriber side device) 30.

  The OLT 10 is provided with N (N is an integer equal to or greater than 2) ports (optical transceivers), to which the splitters 20 are respectively connected via optical fibers. A plurality of ONUs 30 are connected to each other through optical fibers. In general, a maximum of 32 ONUs 30 can be connected to one splitter 20, and a maximum of N × 32 ONUs 30 are accommodated in the OLT 10. Note that the splitter 20 and the ONU 30 are general.

[OLT]
Next, the OLT 10 according to the present embodiment will be described in detail with reference to FIG. The OLT 10 is provided with N optical transceivers 11, a selection / distribution circuit 12, and a PON control circuit 13 as main circuit units.

  The optical transceiver 11 is a circuit unit that is provided corresponding to each port and performs optical transmission with the ONU 30 via the optical fiber and the splitter 20. The optical transceiver 11 receives an upstream frame transmitted from the ONU 30 as an optical signal, performs photoelectric conversion to an electrical signal, and then outputs the electrical frame to the selection / distribution circuit 12, and outputs the electrical signal from the selection / distribution circuit 12. The downstream frame is converted into an optical signal and then transmitted to the ONU 30.

  The selection / distribution circuit 12 switches and selects one of the ports according to the SEL signal from the PON control circuit 13, receives the upstream frame output from the corresponding optical transceiver 11, and receives the PON control circuit. 13 and a function of receiving a downstream frame output from the PON control circuit 13 and distributing it to the optical transceiver 11 of each port.

  The PON control circuit 13 has a function of transmitting an upstream frame transferred from the selection / distribution circuit 12 to a higher-level device (not shown) and a function of transferring a downstream frame received from the higher-level device to the selection / distribution circuit 12. Have.

  In this embodiment, discovery processing is performed on one selected port selected in order from each port, and when a collision occurs in a Register Request frame from the ONU 30 connected to the port, A discovery process is repeatedly performed on a port. Thereby, the collision of the Register Request frame between the ONUs 30 connected to different ports can be reliably avoided, and the collision probability of the Register Request frame can be reduced.

  In the present embodiment, the PON control circuit 13 includes a port setting unit 13A, a discovery control unit 13B, and a collision detection unit 13C as processing units related to discovery processing for performing link-up of a new ONU 30 connected to each port. have.

  The port setting unit 13A has a function of selecting a port to be subjected to the discovery process from among the ports, a function of setting a Discovery Window indicating a period for receiving a frame from the ONU 30 only for the selected selected port, The collision detection unit 13 </ b> C has a function of selecting a collision port that has been detected as having been detected as a selected port with priority over other ports.

  When performing the discovery process, the discovery control unit 13B transmits a Discovery Gate frame from the selected port selected by the port setting unit 13A, and is returned from the ONU 30 of the selected port within the period of the Discovery Window accordingly. And a function of linking up the ONU 30 based on the Register Request frame.

The collision detection unit 13C has a function of detecting the occurrence of a collision between Register Request frames returned from a plurality of different ONUs 30 during the Discovery Window period.
Further, the collision detection unit 13C performs discovery based on the received signal related to the upstream frame received by the optical transceiver 11 of the port selected as the target of the discovery process and the LOS signal indicating the presence or absence of the optical signal detected by the optical transceiver 11. It has a function of detecting a collision port where a Register Request frame collision has occurred during processing.

[Operation of First Embodiment]
Next, operations related to the discovery process of the OLT 10 according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart illustrating the port setting process according to the first embodiment. FIG. 3 is a flowchart showing the discovery process.

  The PON control circuit 13 of the OLT 10 executes the port setting process of FIG. 2 when periodically executing the discovery process for linking up the ONU 30 newly connected to each port. In the present embodiment, as a specific example, when the port setting unit 13A selects one selected port in a predetermined order from the ports and a collision occurrence is detected by the collision detection unit 13C, a collision occurs at the collision port. It is assumed that there is a function of continuously selecting the collision port as a selected port until no more is detected.

First, the port setting unit 13A selects one of the ports 1 to N as a selected port that has not been subjected to discovery processing in a predetermined order set in advance (step 100). At this time, the selected ports are selected one by one in the order of ports 1 to N or round robin.
Subsequently, the PON control circuit 13 executes the discovery process of FIG. 3 for the selected port selected by the port setting unit 13A (step 101).

Thereafter, the collision detection unit 13C detects the occurrence of a collision between Register Request frames returned from a plurality of different ONUs 30 within the Discovery Window period by the discovery process of FIG. 3 (Step 102).
Here, when the occurrence of a collision is detected (step 102: YES), the port setting unit 13A returns to step 101 while continuously selecting the collision port where the occurrence of the collision is detected as the selected port. As a result, the collision port is selected in preference to the next selected port in a predetermined order set in advance, and the discovery process of FIG. 3 is continuously performed on the collision port.

On the other hand, when the occurrence of a collision is not detected in step 102 (step 102: NO), the port setting unit 13A confirms whether there are any unprocessed ports in which the discovery process is unprocessed among the ports 1 to N ( Step 103).
If an unprocessed port exists (step 103: YES), the port setting unit 13A returns to step 100 and selects the next unprocessed port.
If no unprocessed ports remain (step 103: NO), the discovery process has been executed for all of the ports 1 to N, and the series of port setting processes ends.

  The PON control circuit 13 executes the discovery process of FIG. 3 when performing the discovery process on the selected port selected by the port setting unit 13A in step 101 of FIG. The details of the discovery process are the same as the known procedures described in Non-Patent Document 1 described above.

First, the port setting unit 13A sets a Discovery Window indicating a period during which a frame is received from the ONU 30 for the selected port (Step 110).
Next, the discovery control unit 13B transmits a Discovery Gate frame from the selected port, and waits for a Register Request frame from the new ONU 30 connected to the selected port during the Discovery Window period (step 111).

Here, when the Register Request frame is normally received (step 112: YES), the new ONU 30 is linked up based on the Register Request frame (step 113), and the series of discovery processing is terminated.
If the Register Request frame is not normally received (step 112: NO), the series of discovery processing is terminated.

  At this time, the port setting unit 13A notifies the selection / distribution circuit 12 of the selection signal SEL indicating the selected port only during the Discovery Window period set for the selected port. As a result, the selection / distribution circuit 12 switches and connects the selection port that receives the Register Request frame to the PON control circuit 13, and the reception signal RX received by the optical transceiver 11 of the selection port is input to the PON control circuit 13.

  FIG. 4 is a sequence diagram illustrating a port selection example corresponding to FIG. Here, the port setting unit 13A of the OLT 10 first selects port 1 as a selected port based on a predetermined order set in advance, a Discovery Gate frame is transmitted from the port 1, and only a Discovery Window period is Register Request. A frame is awaited. Here, when only one new ONU 30 is connected to the port 1 and no collision occurs in the Register Request frame returned from the ONU 30, the link-up of the ONU 30 is performed based on the Register Request frame.

  Subsequently, port 2 is selected as the selected port, a Discovery Gate frame is transmitted from port 2 of OLT 10, and a Register Request frame is awaited only during the Discovery Window period. Here, when a plurality of new ONUs 30 are connected to the port 2 and a collision occurs between the Register Request frames from these ONUs 30, the port setting unit 13A determines that the port 2 (collision port) until no collision is detected. Is selected repeatedly as the selected port. When the collision between the Register Request frames in the port 2 disappears, the link-up of each ONU 30 is performed based on these Register Request frames.

  Thereafter, since the occurrence of the collision is eliminated, the ports setting unit 13A sequentially selects the ports 3, 4,..., N as the selected ports based on a predetermined order set in advance, and according to the detection of the occurrence of the collision, The collision port is repeatedly selected as the selected port until no collision occurs. Discovery processing is executed for all of the ports 1 to N, and when there are no unprocessed ports, discovery processing is started again from port 1 based on a predetermined order again.

  For collision detection, a loss signal indicating that the optical signal has been received and output from the optical transceiver 11 corresponding to each port is input to the collision detection unit 13C of the PON control circuit 13, and the loss signal is output by the collision detection unit 13C. May be used to detect a collision of the Register Request frame and output the detection result to the port setting unit 13A.

  The Discovery Gate frame may be transmitted to all ports and received from only the selected port. For example, an identification number is provided in the frame, or the selection / distribution circuit 12 is switched. Thus, it may be transmitted only to the selected port. By doing this, the Register Request frame is returned only from the selected port, so that the selection / distribution circuit 12 receives signals from the port receiving the signal using the loss signal or from all ports. It doesn't matter. When transmitting only to the selected port, transmission of uplink signals is not permitted to other ports in the Discovery Window.

Next, with reference to FIG. 5, another operation related to the discovery process of the OLT 10 according to the present embodiment will be described. FIG. 5 is a flowchart illustrating another port setting process according to the first embodiment.
In FIG. 2, the case where the collision port is repeatedly selected continuously as the selection port when the occurrence of the collision is detected has been described as an example. FIG. 5 illustrates a case where a limit is imposed on the number of repeated collision port selections.

First, the port setting unit 13A selects one of the ports 1 to N as a selected port that has not been subjected to the discovery process in a predetermined order set in advance (step 120). At this time, the selected ports are selected one by one in the order of ports 1 to N or round robin.
Subsequently, the PON control circuit 13 executes the discovery process of FIG. 3 for the selected port selected by the port setting unit 13A (step 121).

Thereafter, the collision detection unit 13C detects the occurrence of a collision between Register Request frames returned from a plurality of different ONUs 30 within the Discovery Window period by the discovery process of FIG. 3 (Step 122).
When the occurrence of a collision is detected (step 122: YES), the port setting unit 13A compares the number of repetitions of selection of the collision port with a preset threshold value (step 124), and the number of repetitions of selection is When the threshold is reached (step 124: NO), the process proceeds to step 123 described later.

  On the other hand, if the number of selection repetitions is less than the threshold value (step 124: YES), the process returns to step 121 while continuously selecting the collision ports where the occurrence of the collision is detected as the selected ports. As a result, the collision port is selected in preference to the next port to be selected in the predetermined order set in advance, and the discovery process of FIG. 3 is continuously executed.

On the other hand, if no collision is detected in step 122 (step 122: NO), the port setting unit 13A confirms whether there are any unprocessed ports in which the discovery process is not processed among the ports 1 to N ( Step 123).
If an unprocessed port exists (step 123: YES), the port setting unit 13A returns to step 120 and selects the next unprocessed port.
If no unprocessed ports remain (step 123: NO), the discovery process has been executed for all of the ports 1 to N, and the series of port setting processes is terminated.

  Therefore, since the same port is not repeatedly selected as the selected port continuously more than the threshold number of times, it is possible to avoid a bias in discovery processing with respect to the specific port. The extension of the time required for link up can be avoided reliably.

Next, with reference to FIG. 6, another operation related to the discovery process of the OLT 10 according to the present embodiment will be described. FIG. 6 is a flowchart illustrating another port setting process according to the first embodiment.
In FIGS. 2 and 5, the case where the collision port is repeatedly selected continuously as the selection port when the occurrence of the collision is detected has been described as an example. FIG. 6 illustrates a case where a collision port is selected as a selected port at a higher frequency than other ports by alternately selecting ports and collision ports selected in a predetermined order.

First, the port setting unit 13A selects one of the ports 1 to N as a selected port that has not been subjected to the discovery process in a predetermined order set in advance (step 130). At this time, the selected ports are selected one by one in the order of ports 1 to N or round robin.
Subsequently, the PON control circuit 13 executes the discovery process of FIG. 3 for the selected port selected by the port setting unit 13A (step 131).

  Thereafter, the port setting unit 13A confirms whether or not the priority port is set (step 132). If no priority port is set (step 132: NO), the collision detection unit 13C performs the discovery window by the discovery process of FIG. The occurrence of a collision between Register Request frames returned from a plurality of different ONUs 30 during the period of (1) is detected (step 137).

  If the occurrence of a collision is detected (step 137: YES), the port setting unit 13A sets the collision port as a priority port (step 138), and proceeds to step 136 described later. If no collision is detected (step 137: NO), the port setting unit 13A proceeds to step 136 described later.

On the other hand, if there is a priority port setting in step 132 (step 132: YES), the PON control circuit 13 executes the discovery process of FIG. 3 for the priority port (step 133).
Thereafter, the collision detection unit 13C detects the occurrence of a collision between Register Request frames returned from a plurality of different ONUs 30 within the Discovery Window period by the discovery process of FIG. 3 (Step 134).

  If no collision is detected (step 134: NO), the port setting unit 13A clears the setting of the priority port (step 135), and proceeds to step 136 described later. If the occurrence of a collision is detected (step 134: YES), the port setting unit 13A proceeds to step 136 described later.

Next, the port setting unit 13A checks whether there are any unprocessed ports that have not been processed for discovery among the ports 1 to N (step 136).
If there is an unprocessed port (step 136: YES), the port setting unit 13A returns to step 130 and selects the next unprocessed port.

  If no unprocessed port remains (step 136: NO), the discovery processing has been executed for all of the ports 1 to N, and the series of port setting processing ends.

  Therefore, it is possible to select a collision port more frequently than other ports, instead of continuously selecting a collision port as a selection port repeatedly. As a result, a new ONU 30 of another port due to the influence of a specific port can be selected. The extension of the time required for link up can be avoided reliably. Further, in FIG. 6, the case where the collision port is selected with a frequency of once every two ports selected in a predetermined order has been described as an example, but the frequency is not limited to this, and other frequencies are selected. The collision port may be selected with.

  FIG. 7 is a sequence diagram illustrating a port selection example corresponding to FIG. Here, the port setting unit 13A of the OLT 10 first selects port 1 as a selected port based on a predetermined order set in advance, a Discovery Gate frame is transmitted from the port 1, and only a Discovery Window period is Register Request. A frame is awaited. Here, when a plurality of new ONUs 30 are connected to the port 1 and a collision occurs between Register Request frames from these ONUs 30, the port setting unit 13A sets the collision port 1 as a priority port, and the next Port 2 is selected as a selected port based on a predetermined order.

Here, when only one new ONU 30 is connected to the port 2 and no collision has occurred in the Register Request frame returned from the ONU 30, the link-up of the ONU 30 is performed based on the Register Request frame.
Thereafter, the port setting unit 13A alternately selects a priority port and a port based on a predetermined order until no collision is detected in the port 1 set as the priority port. As a result, ports 1, 3, and 1 are selected as the selected ports, and the priority port setting is cleared when no collision is detected on port 1, and thereafter, ports 4,... N is sequentially selected as the selected port.

[Effect of the first embodiment]
As described above, in the present embodiment, the port setting unit 13A selects a port to be subjected to the discovery process from each port and receives a frame from the ONU 30 only for the selected port. When the discovery control unit 13B performs the discovery process, the discovery control unit 13B transmits a Discovery Gate frame from the selected port selected by the port setting unit 13A, and in response to this, the selected port is within the period of the Discovery Window. Based on the Register Request frame returned from the ONU 30, the ONU 30 is linked up, and the collision detection unit 13C detects the occurrence of a collision between the Register Request frames returned from a plurality of different ONUs 30 during the Discovery Window period. The port setting unit 13A uses another collision port where the collision detection is detected by the collision detection unit 13C. The selected port is selected in preference to the other port.

  As a result, the target port for the discovery process is limited to any one of the ports, so that it is possible to reliably avoid the collision of Register Request frames between the ports. Also, in the discovery process, the probability that the collision port where the collision of the Register Request frame has occurred is selected as the selected port with priority over the other ports, and the Register Request frame from the new ONU 30 connected to the collision port is received. Is increased. Therefore, even in the case of a multi-port PON system in which a plurality of ports are provided in the OLT 10, it is possible to reliably reduce the time required for link-up of the new ONU 30.

  Further, in the present embodiment, when the port setting unit 13A selects one selected port from the ports in a predetermined order, and the collision detection unit 13C detects the occurrence of a collision, the collision occurrence at the collision port is detected. The collision port may be continuously selected as the selected port until it is not. As a result, the new ONU 30 connected to the collision port can be linked up in the shortest time.

Further, in the present embodiment, when the port setting unit 13A selects one selected port from the ports in a predetermined order, and the collision detection unit 13C detects the occurrence of a collision, the collision occurrence at the collision port is detected. Until it is not performed, the collision port may be selected as the selected port with a higher frequency than the other ports.
As a result, the new ONU 30 connected to the collision port can be linked up in a short time, and an increase in the link-up delay of the new ONU 30 connected to another port due to the influence of the collision at the collision port is avoided. It becomes possible.

  In addition, in the port setting method for selecting the collision port continuously as the selected port or the port setting method for increasing the frequency of selecting the collision port as the selection port described in this embodiment, the collision port is selected again. When selected, the discovery window of the collision port may be changed to a reselection length longer than the length for the initial selection. Thereby, the probability that the Register Request frame from the new ONU 30 of the collision port is received is increased.

  Further, the above-described port setting methods may be used in any combination. For example, when a collision port is selected again, the Discovery Window may be lengthened in the same manner as described above, and when a collision still occurs, it may be selected alternately with another port. As a result, it is possible to execute an optimal discovery process according to the operation mode of the optical transmission system 1, particularly the connection status of the new ONU 30.

Further, in the present embodiment, when the collision detection unit 13C detects an FCS error indicating a frame error or an error correction impossible by FEC from the received signal of the selected port within the period of the Discovery Window, You may make it detect generation | occurrence | production of a collision. In this case, since a loss signal for each port is not necessary, it can be omitted from the configuration of FIG.
Further, when a loss signal related to the selected port indicates that an optical signal is input, a frame cannot be recognized from the received signal of the selected port, and the occurrence of a collision at the selected port may be detected. .

In addition, when the frame signal length detected from the received signal of the selected port is longer than the specified value, occurrence of a collision at the selected port may be detected, or simultaneously from a plurality of different ports included in the selected port. When a signal is received, occurrence of a collision at the selected port may be detected.
Moreover, you may use combining these collision detection methods arbitrarily.

  In this embodiment, when no collision occurs, the port selection method is given priority from the above-described method of selecting port 0 to port N in order, as well as the port with a small number of ONUs already linked up. You may make it select. This is because there is an upper limit on the number of ONUs that can be connected to a port, and a port with a smaller number of ONUs already linked up is more likely to be connected to a new ONU 30. Therefore, it is possible to reduce the time to link-up by preferentially selecting ports with a small number of ONUs already linked up or by lengthening the Discovery Window.

  In addition to the above, the number of collision signals may be estimated, and the frequency of selecting a collision port and the length of the Discovery Window may be determined accordingly. For example, the port selection frequency or the length of the Discovery Window may be proportional to the number of Register Request frames that have collided. Thereby, the time to link-up regarding more new ONUs 30 can be reduced. At this time, in order to determine the number of Register Request frames that have collided, for example, by dividing the received signal length by a prescribed signal length, a known method described in Non-Patent Document 1 described above may be used. .

  In the present embodiment, the ONU 30 connected to a port other than the selected port selected as the target of the discovery process is set to sleep in the Discovery Window period in which the transmitter of the ONU 30 is set as the selected port according to an instruction from the OLT 10. You may make it transfer to a state. As a result, power consumption in each ONU 30 can be reduced, and power saving in the entire optical transmission system 1 can be realized.

[Second Embodiment]
Next, an optical transmission system 1 and an OLT (station side apparatus) 10 according to a second embodiment of the present invention will be described with reference to FIG. FIG. 8 is a block diagram illustrating the configuration of the optical transmission system and the OLT according to the second embodiment.

  In the first embodiment, a case has been described as an example in which only one port to be subjected to discovery processing is selected. In this embodiment, a case will be described in which a plurality of ports are collectively selected as targets for discovery processing. In this embodiment, it is necessary to detect the presence / absence of a Register Request frame collision for each port. Therefore, compared with the configuration of FIG. 1 described above, the reception signal RX from the optical transceiver 11 of each port is individually supplied to the PON control circuit 13 via the selection / distribution circuit 12. The configuration is almost the same as that of FIG.

[Operation of Second Embodiment]
Next, an operation related to the discovery process of the OLT 10 according to the present embodiment will be described with reference to FIG. FIG. 9 is a flowchart illustrating the port setting process according to the second embodiment.

  The PON control circuit 13 of the OLT 10 executes the port setting process of FIG. 9 when periodically executing the discovery process for linking up the ONU 30 newly connected to each port. In this embodiment, as a specific example, when the port setting unit 13A selects a plurality of selected ports in a predetermined order from the ports, and collision detection is detected by the collision detection unit 13C, a collision occurs in all the collision ports. It is assumed that it has a function of selecting any one or more of the collision ports in succession until no occurrence is detected.

First, the port setting unit 13A selects a plurality of unprocessed ports in the predetermined order set in advance from the ports 1 to N as selected ports (step 200). At this time, the selected ports (M is an integer equal to or greater than 2) are selected in order of ports 1 to N or in round robin.
Subsequently, the PON control circuit 13 executes the discovery process of FIG. 3 for the selected port selected by the port setting unit 13A (step 201). At this time, a Discovery Window is set at the same time for each selected selected port (step 110), and a Discovery Gate frame is simultaneously transmitted from each selected port (step 111).

Thereafter, the collision detection unit 13C detects the occurrence of a collision between Register Request frames returned from a plurality of different ONUs 30 within the Discovery Window period by the discovery process of FIG. 3 (Step 202).
Here, when the occurrence of a collision is detected (step 202: YES), the port setting unit 13A newly selects all the collision ports where the occurrence of the collision is detected as selection ports continuously (step 204). Return to. As a result, a collision port is selected in preference to the next port to be selected in a predetermined order set in advance, and the discovery process of FIG. 3 is continuously performed on these collision ports. .

On the other hand, when the occurrence of a collision is not detected in step 202 (step 202: NO), the port setting unit 13A confirms whether there are any unprocessed ports in which the discovery process is not processed among the ports 1 to N ( Step 203).
If there is an unprocessed port (step 203: YES), the port setting unit 13A returns to step 200 and selects the next unprocessed port.
If no unprocessed port remains (step 203: NO), the discovery processing has been executed for all of the ports 1 to N, and the series of port setting processing ends.

  FIG. 10 is a sequence diagram illustrating a port selection example corresponding to FIG. Here, the port setting unit 13A of the OLT 10 first selects ports 1 and 2 as selection ports based on a predetermined order set in advance, and a Discovery Gate frame is transmitted from the ports 1 and 2, and the Discovery Window A Register Request frame is awaited for a certain period. Here, when only one new ONU 30 is connected to the port 1 and no collision occurs in the Register Request frame returned from the ONU 30, the link-up of the ONU 30 is performed based on the Register Request frame.

  On the other hand, when a plurality of new ONUs 30 are connected to port 2 and a collision occurs between Register Request frames from these ONUs 30, port setting unit 13A determines port 2 (collision port) until no collision is detected. Select repeatedly as the selected port. Thereby, when there is no collision with respect to the Register Request frame from the port 2, the link-up of each ONU 30 is performed based on these Register Request frames.

  Subsequently, the ports 3 and 4 are selected as the selected ports, the Discovery Gate frame is transmitted from the ports 3 and 4, and the Register Request frame is awaited only during the Discovery Window period. Here, although one new ONU 30 is connected to each of the ports 3 and 4, when a Register Request frame collides between the ports, these 3 and 4 are selected again as the selected ports, and the Discovery Gate frame is A Register Request frame is awaited only during the Discovery Window period. Thereby, when there is no collision with respect to the Register Request frames from the ports 3 and 4, the link-up of each ONU 30 is performed based on these Register Request frames.

  In this way, the port setting unit 13A sequentially selects two ports 5, 6,..., N as selected ports in order based on a predetermined order set in advance. The collision port is repeatedly selected as the selected port until no more occur. Discovery processing is executed for all the ports 1 to N, and when there are no unprocessed ports, discovery processing is started again from ports 1 and 2 again based on a predetermined order.

  In the port setting method of FIG. 9, a threshold value may be provided for the number of repeated selections of collision ports as shown in FIG. 5 to limit the number of continuous selections. The frequency of selecting a port as a selected port may be increased.

Next, as shown in FIG. 11, all ports may be selected as selection ports first. FIG. 11 is a sequence diagram illustrating another port selection example according to the second embodiment.
In this case, first, all the ports are selected as the selected ports, the Discovery Gate frame is transmitted from the ports 1, 2,..., N, and the Register Request frame is awaited only during the Discovery Window period. Here, when there is no collision in the Register Request frame returned from the ONU 30 at each port other than the ports 2, 3, and 4, the link-up of the ONU 30 is performed based on these Register Request frames.

Subsequently, collision ports 2, 3, and 4 are selected as selected ports, Discovery Gate frames are transmitted from ports 2, 3, and 4, and a Register Request frame is awaited only during the Discovery Window period. Here, in the case where there is no collision with respect to the Register Request frame returned from the ONU 30 at the port 2, the link-up of the ONU 30 is performed based on the Register Request frame. Thereafter, the collision port is repeatedly selected as the selection port until there is no collision port.
Thereby, when the number of new ONUs 30 connected to each port is relatively small, the time until the link-up of each ONU 30 can be reduced extremely efficiently.

  In addition, as shown in FIG. 12, as a method of selecting a selection port for the second and subsequent times, instead of selecting all collision ports at once, select a selected port from among the collision ports one by one or a prescribed number M. May be. FIG. 12 is a sequence diagram illustrating another port selection example according to the second embodiment.

In this case, first, all ports are selected as selected ports, and the collision ports 2, 3, and 4 in which the occurrence of a collision is detected are sequentially selected, for example, one by one.
As a result, the number of reselected ports is limited to one or M. Therefore, when the number of new ONUs is large and the probability that the Register Request frame collides between ports is relatively high, the link up of each ONU 30 is performed. This time can be efficiently reduced.

  Further, in the port setting methods of FIGS. 10 and 11, as shown in FIG. 5 described above, a threshold may be provided for the number of repeated selections of collision ports to limit the number of continuous selections. As described above, the frequency of selecting the collision port as the selection port may be increased.

Also, when selecting a selected port from among the collided ports, the number of Register Request frames that collided in the previous discovery process is detected for each colliding port as the number of collisions, and the selected ports are selected in descending order of the number of collisions By doing so, a collision can be avoided, and the time to link-up of more new ONUs 30 can be reduced.
In addition, when the number of collisions is small, it can be estimated that the possibility of collision is low even if Register Request frames are received from multiple ports. If the threshold is less than or equal to the threshold value, these multiple ports may be selected as the selected ports.

  In the present embodiment, the same method as that of the first embodiment is used as the collision detection method in the collision detection unit 13C. Here, when Register Request frames arrive at the optical transceiver 11 from a plurality of ports at exactly the same timing, it is difficult to recognize the reception of a signal and detect a collision by an FCS error or an FEC error. A collision can be detected by using the loss signal shown.

  Unlike the first embodiment, this embodiment receives the Register Request frame from all ports at the station side device when there is no collision of the Register Request frame, so the time until link up is shorter. There is a characteristic that

[Effect of the second embodiment]
As described above, in the present embodiment, when the port setting unit 13A selects a plurality of selected ports in a predetermined order from the ports, and collision detection is detected by the collision detection unit 13C, a collision occurs in all the collision ports. One or more of the collision ports are continuously selected until no occurrence is detected.
As a result, the number of discovery processes can be reduced as compared with the case where the selected ports are selected one by one, and the time required for link-up of the new ONU 30 can be reliably shortened.

Further, in the present embodiment, when the port setting unit 13A selects a plurality of selected ports in a predetermined order from the ports, and the collision detection is detected by the collision detection unit 13C, the collision port is detected more frequently than the other ports. Any one or more of these may be selected as a selection port.
As a result, the new ONU 30 connected to the collision port can be linked up in a short time, and an increase in the link-up delay of the new ONU 30 connected to another port due to the influence of the collision at the collision port is avoided. It becomes possible.

[Extended embodiment]
The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. In addition, each embodiment can be implemented in any combination within a consistent range.

  DESCRIPTION OF SYMBOLS 1 ... Optical transmission system, 10 ... OLT (station side apparatus), 11 ... Optical transceiver, 12 ... Selection / distribution circuit, 13 ... PON control circuit, 13A ... Port setting part, 13B ... Discovery control part, 13C ... Collision detection part , 20... Splitter, 30... ONU (subscriber side device).

Claims (9)

It has multiple ports for PON, transfers the frames exchanged between each ONU accommodated in these ports and the host device via the optical splitter, and links the newly connected ONU to the port A station-side device that periodically executes discovery processing for uploading,
A port setting unit that selects a port to be processed in the discovery process from among the ports, and sets a Discovery Window that indicates a period for receiving a frame from the ONU only for the selected port;
When performing the discovery process, a Discovery Gate frame is transmitted from the selected port selected by the port setting unit, and in response to the Register Request frame returned from the ONU of the selected port within the period of the Discovery Window. Based on the discovery control unit that links up the ONU,
A collision detection unit for detecting a collision between the Register Request frames returned from a plurality of different ONUs within the period of the Discovery Window,
The station setting device, wherein the port setting unit selects the collision port in which the collision occurrence is detected by the collision detection unit as a selection port with priority over other ports. In the station side apparatus of Claim 1,
The port setting unit selects one of the selected ports from the ports in a predetermined order, and when a collision occurrence is detected by the collision detection unit, until the collision occurrence at the collision port is not detected. A station-side device, wherein a collision port is continuously selected as the selection port. In the station side apparatus of Claim 1,
The port setting unit selects one of the selected ports in a predetermined order from the ports, and when a collision occurrence is detected by the collision detection unit, another port is detected until no collision occurrence is detected at the collision port. The station-side apparatus selects the collision port as the selection port at a frequency higher than that of the other port. In the station side apparatus of Claim 1,
The port setting unit selects a plurality of the selected ports in a predetermined order from the ports, and when a collision occurrence is detected by the collision detection unit, until the collision occurrence is not detected in all of the collision ports, the port setting unit One of the collision ports or a plurality of collision ports is continuously selected. In the station side apparatus of Claim 1,
The port setting unit selects a plurality of the selected ports in a predetermined order from the ports, and when a collision occurrence is detected by the collision detection unit, any one of the collision ports is more frequently detected than the other ports. Or, a plurality of stations are selected as the selection port. In the station side apparatus of Claim 2 or Claim 4,
The station side apparatus, wherein the port setting unit selects the selected port according to the predetermined order when the number of repetitions of selection of the collision port reaches a threshold value. In the station side apparatus in any one of Claims 1-6,
When the port setting unit reselects the collision port as the selected port, the station side device temporarily increases the length of the Discovery Window set to the collision port. In the station side apparatus in any one of Claims 1-7,
When the collision detection unit detects an FCS error indicating a frame error or an error correction failure due to FEC in the received signal of the selected port received during the Discovery Window period, the loss signal related to the selected port is an optical signal. The frame is not recognized from the received signal of the selected port even though the input is indicated, the frame signal length detected from the received signal of the selected port is longer than a specified value, or included in the selected port A station-side apparatus, wherein when a signal is simultaneously received from a plurality of different ports, the occurrence of the collision at the selected port is detected.   An optical transmission system comprising: a plurality of optical splitters; and a station-side device that transfers a frame exchanged between a plurality of ONUs and higher-level devices connected via the optical splitter, the station-side device An optical transmission system comprising the station side device according to any one of claims 1 to 8.

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