JP6148142B2 - Optical communication system - Google Patents

Description

  The present invention relates to an optical communication system, and more particularly to a PON system with redundant OSUs.

  FIG. 1 shows a configuration comprising a Passive Optical Network (PON) 11 and a Layer 2 switch (L2SW) 12 which are typical configurations of the current access network. The PON 11 includes an optical line terminal (OLT) 14, an optical coupler 18, an optical fiber 19, and an optical network unit (ONU, subscriber termination device) 17. The OLT 14 includes a plurality of optical subscriber units (OSUs) 15 and a control panel (CONT) 20 that controls the OSUs 15. Each OSU 15 connects a plurality (for example, 32) of ONUs 17. In the PON 11, since the optical fiber 19 between the OSU 15 and the OSU 15 and the optical coupler 18 is shared by a plurality of ONUs, a service can be provided at low cost.

  The L2SW 12 includes a large number of ports that are connected to the PON 11 and the core network 13, and each port on the PON 11 side is connected to one OSU 15 by one wiring. Since the L2SW 12 has a concentrating function, a smaller number of wires than the number of wires connected to the PON side port are connected to the core network 13 port, and the wires from the OSU 15 are concentrated and connected to the core network 13. . Therefore, this L2SW 12 is referred to as a concentrator switch 40.

  When the concentrator switch 40 receives a downstream frame from a higher level, it reads an identifier (for example, Virtual LAN Identifier (VID)) attached to the frame. Since the corresponding VID number is registered in advance in each PON side port of the line concentrator switch 40, the line concentrator switch 40 knows to which PON side port the received downstream frame should be distributed. Since the ONU 17 corresponding to the VID number registered in each PON side port is accommodated via the OSU 15 connected to the PON side port, any VID number assigned to any PON side port is stored. The downstream frame is delivered to the corresponding ONU 17 via the OSU 15. On the other hand, the upstream frame from each OSU 15 is received and then output from the line collecting switch to the upper level according to the transmission order determined by an arbitrary scheduling method.

  In the example shown in FIG. 1, the connection between the PON side port of the line concentrator switch 40 and the OSU 15 has a 1: 1 relationship, and the line concentrator switch 40 includes a number of PON side ports that can accommodate a plurality of OLTs 14. Therefore, for example, when accommodating the OLT 14 to the maximum extent, the same number of wirings as the number of all OSUs 15 accommodated in all the OLTs 14 are connected between the concentrator switches 40 and the OLT 14.

  In the above description, the concentrator switch 40 is externally attached to the OLT 14, but may be incorporated in the OLT 14. Further, the line concentration switch 40 may be shared by a plurality of OLTs 14. In the configuration of FIG. 1, the line concentrator switch 40 is externally attached to the OLT 14 and is shared by a plurality of OLTs 14. Further, the line collecting switch 40 may have a multi-stage configuration.

  Under the access network having such a configuration, various services are currently in widespread use. For example, a video distribution service based on multicast frame transfer is realized by the network configuration shown in FIG. A user terminal (host) 21 that receives a video service is connected to the ONU 17, and a video distribution server 32 is connected to a higher level of the line collecting switch 40 via a multicast router 31. Here, a plurality of hosts 21 connected to one ONU 17 may be used. The video distribution server 32 always sends each multicast frame corresponding to each program (channel (Ch)) toward the multicast router 31. The multicast router 31 transmits the multicast frame of the channel requested to be viewed from the host 21 via the ONU 17, the OSU 15, and the concentration switch 40 to the OSU 15 that accommodates the viewing request source host 21 via the concentration switch 40. The OSU 15 holds a multicast table (hereinafter referred to as a table) for controlling the transfer of multicast frames between the OSU 15 and the ONU 17. In this table, the correspondence between the self-distributed ONUs 17 and the distribution channels to each of those OUNs 17 is described, and the OSU 15 grasps to which ONU 17 under its subordinates which channel is to be distributed. ing. When the OSU 15 receives a viewing request or a withdrawal request from the ONU 17, this table is updated according to the contents, and the OSU 15 transmits a viewing request or a delivery stop message to the multicast router via the line collecting switch 40 as necessary. .

  These viewing request and withdrawal request signals correspond to IGMP (Internet Group Management Protocol) and MLD (Multicast Listener Discovery) that are commonly used in multicast communications. For example, as one of the MLD operations, it is known that the multicast router 31 periodically transmits a general query to confirm the presence of a multicast receiver. This operation is a video distribution service in the above-described PON system. It has also been applied. The OSU 15 having a table periodically transmits a general query to all of the subordinate ONUs 17, and the ONU 17 that has received the general query returns a channel for which continuation of distribution is desired to the OSU 15. The OSU 15 that has transmitted the general query updates its own table based on the response from the ONU 17. For the ONU 17 that has not responded or the channel that has not been requested to continue, the distribution stop request for the multicast channel of the corresponding channel is transmitted to the upper level in order to stop the distribution to the ONU 17 or the distribution of the channel.

  As a method of distributing a multicast frame from the OSU 15 to the ONU 17, a method in which the OSU 15 distributes to all the ONUs 17 under broadcast by broadcast is known. In this method, since a multicast frame arrives at all ONUs 17, a multicast frame of a channel that is not desired to be viewed may reach the ONU 17. Therefore, each ONU 17 needs to transfer only a multicast frame of a necessary channel (a channel requested by a subordinate host) to the host 21 and discard a multicast frame of an unnecessary channel. Each ONU has a filter function for realizing this. When there is a request for viewing an arbitrary channel from the host 21 via the ONU 17, the OSU 15 sets the ON / OFF filter of the ONU 17 so that only the multicast frame of the corresponding channel is transmitted and the other multicast frames are discarded. Thus, the corresponding host 21 can view a desired video. In such a GE-PON (Gigabit Ethernet (registered trademark) PON) system described in Non-Patent Document 1, such an ONU filter setting is performed by OAM (Operation, Operation, which indicates the Open or Close of the corresponding filter to the ONU 17 under control of the OSU 15. (Administration and Maintenance) frame. Here, the OAM frame is a frame used for controlling the PON section.

  Generally, when there is a need for function expansion or defect correction in an operating device constituting an access network, the firmware (FW) of the corresponding device is updated through an operation operation. However, at this time, since the corresponding device is restarted, for example, when the FW of the OSU 15 is updated, the communication of all of the subordinate ONUs 17 is cut off. Particularly in the video distribution service that is popular through the above-described method, since it is important to supply the service stably, it is required to complete the FW update of the apparatus without interruption of service. As a method for realizing this, application of PON protection in which the OSU 15 is made redundant is effective. PON protection is described below.

  Making a part or all of the devices and fibers constituting the PON redundant is called PON protection, and there are various methods depending on the redundant part and the redundant method. For example, a system in which the correspondence between the normal system and the standby system is N: 1, such as having one spare system device for N normal system devices, is called N: 1 protection, and that method is proposed in Non-Patent Document 2. Has been.

  FIG. 3 shows a configuration example of N: 1 protection. One OLT 14 in which N normal OSUs 15 and one spare OSU 15 are accommodated, one N × 1 optical switch 16, N B: 2 optical couplers 18, and A × N or less ONU 17 is used. Here, A is the maximum number of ONUs accommodated per OSU, and B is 1 ≦ B ≦ A. However, if the cost is not considered, technically, B> A is also possible. N normal system OSUs are respectively connected to one port on the two sides of N B: 2 optical couplers 18 by one trunk fiber, and one standby system OSU 15 is one of N × 1 optical switch 16. It is connected to the side (input side) with one optical fiber. The other port on the two sides of the N number of B: 2 optical couplers 18 is connected to the N side (output side) of the N × 1 optical switch 16 with one spare trunk fiber, and B: 2 optical coupler. The B side of 18 is connected to a maximum of B ONUs 17 through a maximum of B optical fibers. If the N side of the N × 1 optical switch 16 has one open port (NC port) that is not connected to the optical fiber, in addition to the N ports that are assumed to be connected to the standby trunk fiber. To do.

  At the time of initial construction, the output light from the standby OSU 15 does not collide with the output light from the normal OSU 15 in the lower part of the B: 2 optical coupler 18 via the N × 1 optical switch 16 and the standby trunk fiber. It is assumed that the standby OSU 15 is in a light-off state and that one side of the N × 1 optical switch 16 has established a route with the NC port. In such a system, when normal, the normal OSU 15 communicates with the subordinate ONUs 17 without going through the optical switch 16. When updating the FW of the normal OSU 15, the path of the N × 1 optical switch 16 is switched so that the path between the ONU 17 under the normal OSU 15 and the standby OSU 15 is established, and the normal OSU 15 is turned off. At the same time, when the standby OSU 15 is turned on, the corresponding ONU 17 can start communication with the standby OSU 15. While the ONU 17 is communicating with the standby OSU 15, the FW update of the OSU 15 can be performed without service interruption of the ONU 17 by performing the FW update of the normal OSU 15 as the switching source.

  As described above, if the video distribution service is performed under the PON system having the configuration in which the OSU is made redundant, the service interruption can be avoided even when the OSU FW is updated.

  Although it has been described above that the OSU 15 has a table for multicast control between the ONU 17 and the OSU 15, the line concentrator switch 40 may also have a table for multicast control between the OSU 15 and the line concentrator switch 40. In this case, in the table of the line concentrator switch 40, the correspondence between each OSU 15 and the distribution channel to the OSU 15 is described. Similarly to the table of the OSU 15, the table of the concentration switch 40 is updated through the reception of a viewing request and a withdrawal request from the OSU 15 and the presence / absence of a response to the transmission of the general query from the concentration switch 40 to the OSU 15.

  In this way, the line concentrator switch 40 is also provided with a table, and in the PON system having a configuration in which the OSU 15 is made redundant, consider the case of performing OSU switching for FW update of the OSU 15 (here, N = 2) (In the configuration of FIG. 3, switching from OSU # 1 to OSU # 3). At the time of switching from OSU # 1 to OSU # 3, the line concentrator switch 40 recognizes that the connection destination OSU15 of the ONU 17 under OSU # 1 has changed to OSU # 3, and the table of the line concentrator switch 40 is also updated at this time. Is done.

  For example, when normal before switching, ONU # 1 and ONU # 2 under OSU # 1 receive Ch1 and Ch2, respectively, and ONU # 3 and ONU # 4 under OSU # 2 both receive Ch2. FIG. 4 shows a table of the line collecting switch 40, OSU # 1 and OSU # 3 in this case. Thus, the concentrator switch when the OSU switching from OSU # 1 to OSU # 3 is completed in a distribution situation where the concentrator switch 40 transfers Ch1 and Ch2 to OSU # 1 and Ch2 to OSU # 2. FIG. 5 shows a table of 40 and OSU # 3.

  During the switching, the distribution of the Ch1 and Ch2 from the line concentration switch 40 to the OSU # 1 is stopped by changing the accommodation destination OSU15 of the ONU # 1 and ONU # 2 from the OSU # 1 to the OSU # 3. Distribution of Ch2 to # 2 is continued, and distribution of Ch1 and Ch2 to OSU # 3 is started. As a result, the table of the line concentrator switch 40 is as shown in FIG. 5, and the line concentrator switch 40 can transfer the distribution of Ch1 and Ch2 to OSU # 3 immediately after OSU switching.

  However, since OSU # 3 is not communicating with any ONU 17 in the normal state before switching, the table before switching of OSU # 3 does not transfer any multicast frame to all ONUs 17, as shown in FIG. It becomes the contents of the status (not registered). The OSU # 3 table remains exactly the same as before the switching even when the switching is completed, unless a mechanism for transferring the table contents of the OSU # 1 to the OSU # 3 is implemented during the OSU switching. Therefore, even if OSU # 3 receives Ch1 and Ch2 transmitted from the line collecting switch 40 to OSU # 3 after OSU switching, Ch1 and Ch2 are not distributed to the subordinate ONUs # 1 and # 2. (* However, after OSU switching, OSU # 3 builds its own table through sending General Queries to subordinate ONUs # 1 and # 2, and then updates the subordinate ONUs # 1 and # 2. Distribution of Ch1 and Ch2 is started.) As a result, the video service of these ONUs # 1 and # 2 is interrupted by OSU switching.

  Furthermore, if OSU # 3 receives the general query from the line concentrator switch 40 before the OSU # 3 constructs its own table through the general query transmission after switching, the OSU # 3 will display the non-delivery status table at that time. Since the response is returned to the concentration switch 40 based on the above, it is impossible to notify the continuation of the distribution of Ch1 and Ch2. As a result, there is a problem that even the transmission of Ch1 and Ch2 from the line collecting switch 40 to the OSU # 3 is stopped.

  In FIG. 5, the list for the switching source OSU (OSU # 1) in the table of the line concentrator switch 40 is also updated during switching, but may not be updated during switching. This is because, when only the list for the switching destination OSU 15 is updated without updating the list for the switching source OSU 15 during switching, the line concentrator switch 40 transmits a multicast frame of the same channel to the switching source OSU 15 and the switching destination OSU 15. As described above, in the configuration of FIG. 3, the switching source OSU 15 and the switching destination OSU 15 are not turned on at the same time, so even if the concentration switch 40 transmits the same multicast frame to the switching source OSU 15 and the switching destination OSU 15. This is because those multicast frames do not collide at the ONU 17.

  In the following description, it is assumed that the list for the switching source OSU 15 in the table of the line collecting switch 40 is not updated during switching.

IEEE Std 802.3ah, CSMA / CD Access Method and Physical Layer Specializations, Amendment: Media Access Control Parameters, Physical Layers, Physical Layers, Physical Layers. 185-234, 421-475 “5.8 Type B with N: 1”, ITU-T Series G Supplement 51, p. 11-12 ITU-T G. 983.1, SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS, digital sections and digital lines system and optical lines 3 systems and optical lines. 119-121

  An object of the present invention is to avoid service interruption for ONUs under the switching source OSU while reducing the OSU switching processing time compared to the case where the switching destination OSU takes over the management table from the switching source OSU.

  The optical communication system of the present invention is a PON system in which the OSU and the concentrator switch have a multicast proxy function. When switching the OSU, all the channels to be distributed to the switching destination OSU after switching the concentrating switch are managed in the switching destination OSU. Is registered in the “Dummy ONU” field as the viewing status of the dummy ONU.

Specifically, the optical communication system of the present invention is
A plurality of OSUs (Optical Subscriber Units);
At least one ONU (Optical Network Unit) that can be connected to any of the OSUs by switching routes;
An optical communication system comprising:
Each OSU has a multicast table (hereinafter referred to as OSU table) including a list of distribution channels of each ONU connected to the OSU,
The OSU table includes a list of temporary dummy ONU distribution channels that are not connected to any OSU.

In the optical communication system of the present invention,
Further comprising a line concentrator switch that distributes the data to be distributed by multicast to the OSU according to the ONU to be distributed,
The line concentrator switch includes a multicast table (hereinafter referred to as a line concentrator switch table) that stores a list of channels distributed by each ONU connected to the OSU for each OSU.
When a path is switched from one OSU (hereinafter referred to as a switching source OSU) to another OSU (hereinafter referred to as a switching destination OSU), a list of channels of the switching destination OSU in the line concentration switch table is displayed. In addition to taking over from the channel list of the switching source OSU, an update instruction for updating the channel list for the dummy ONU in the OSU table (hereinafter referred to as switching destination OSU table) in the switching destination OSU is sent to the switching destination OSU. You may send it.

In the optical communication system of the present invention,
The line concentrator switch sends the update instruction to the switching destination OSU when the distribution channel list of the switching destination OSU in the line concentrating switch table is taken over from the list of distribution channels of the switching source OSU.
The switching destination OSU may update the list of distribution channels for the dummy ONU in the switching destination OSU table in accordance with the received update instruction and start communication with the ONU.

In the optical communication system of the present invention,
The line concentrator switch transmits the update instruction to the switching destination OSU, and when registration of the list of distribution channels of the switching destination OSU in the line concentrating switch table is completed from the list of distribution channels of the switching source OSU, a registration completion notification is sent. Issue,
The switching destination OSU updates the distribution channel list for the dummy ONU in the switching destination OSU table in accordance with the update instruction received from the line concentration switch, and the ONU is triggered when the registration completion notification is issued from the line concentration switch. You may start communication with.

In the optical communication system of the present invention,
The line concentrator switch transmits the update instruction to the switching destination OSU after starting to take over the distribution channel list of the switching destination OSU in the line concentrating switch table from the list of distribution channels of the switching source OSU. When the handover of the distribution channel list of the switching destination OSU is completed from the distribution channel list of the switching source OSU, a registration completion notification is issued.
The switching destination OSU updates the distribution channel list of the dummy ONU in the switching destination OSU table according to the received update instruction, updates the switching destination OSU table, and issues the registration completion notification from the line concentration switch. The communication with the ONU may be started when both are completed.

Specifically, the OSU of the present invention is
A plurality of OSUs (Optical Subscriber Units);
At least one ONU (Optical Network Unit) that can be connected to any of the OSUs by switching routes;
An OSU of an optical communication system comprising:
A multicast table (hereinafter referred to as OSU table) including a list of distribution channels of each ONU connected to itself is provided.
The OSU table includes a list of temporary dummy ONU distribution channels that are not connected to any OSU.

Specifically, the line concentration switch of the present invention is
A plurality of OSUs (Optical Subscriber Units);
At least one ONU (Optical Network Unit) that can be connected to any of the OSUs by switching routes;
A concentrator switch that distributes the data to be distributed by multicast to the OSU according to the ONU to be distributed;
The line concentrator switch of an optical communication system comprising:
A multicast table (hereinafter referred to as a concentrator switch table) that stores a list of channels distributed by each ONU connected to the OSU for each OSU;
When a path is switched from one OSU (hereinafter referred to as a switching source OSU) to another OSU (hereinafter referred to as a switching destination OSU), a list of channels of the switching destination OSU in the line concentration switch table is displayed. In addition to taking over from the channel list of the switching source OSU, an update instruction for updating the channel list for the dummy ONU in the OSU table (hereinafter referred to as switching destination OSU table) in the switching destination OSU is sent to the switching destination OSU. Send.

  The above inventions can be combined as much as possible.

  According to the present invention, it is possible to avoid service interruption for ONUs under the switching source OSU while reducing the OSU switching processing time compared to the case where the switching destination OSU takes over the management table from the switching source OSU.

An example of a PON system is shown. 2 shows an example of a network configuration when performing multicast distribution. A configuration example of N: 1 protection is shown. An example of a table provided in the OSU and the line concentrator switch in N: 1 protection is shown. An example of the table with which the OSU and the line concentrator switch are provided when the ONU accommodation destination OSU is switched is shown. 2 shows an example of a configuration of an OLT according to the first embodiment. An example of the timing chart in Embodiment 1 is shown. An example of the management switch management table before route switching is shown. An example of the management table of OSU # 3 before route switching is shown. An example of the management table of the concentrator switch after a path change is shown. An example of the management table of OSU # 3 after path switching is shown. An example of the timing chart in Embodiment 2 is shown. An example of the timing chart in Embodiment 3 is shown.

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

  A list for “dummy ONU” is provided in the table of each OSU 15 as the ONU 17 that does not exist under any OSU 15 and does not exist. Then, at the time of OSU switching, all the channels transferred by the line concentrator switch 40 to the switching source OSU 15 are registered in the list for the dummy ONU 17 in the table of the switching destination OSU 15 as channels being distributed. As a result, in the table of the switching destination OSU 15, all the ONUs 17 other than the dummy ONU 17 are in an unregistered state as before the switching, but the dummy ONU 17 has all the subordinates of the switching source OSU 15 before the switching. All channels distributed to the ONU 17 are being distributed. Therefore, even if the switching destination OSU 15 receives the channel transmitted to the ONU 17 under the switching source OSU 15 transmitted from the line concentrator switch 40, it can be transferred to the subordinate ONU 17 without being discarded. The ONU 17 that has been able to avoid the video service interruption.

  Further, when the list for the dummy ONU 17 in the table of the switching destination OSU 15 is registered, even if the switching destination OSU 15 receives the general query from the line collecting switch 40, the switching destination OSU 15 lists the list for the dummy ONU 17 in its own table. Based on the viewing status, the request for continued distribution of the corresponding channel can be returned to the concentrator switch 40. Therefore, it is possible to avoid the stop of distribution from the line collecting switch 40 to the switching destination OSU 15.

  Compared with the case where the table contents (viewing CH for each ONU 17) of the switching source OSU 15 are handed over to the switching destination OSU 15, it is only necessary to register a list for the dummy ONU 17, and the amount of table handing over can be reduced. Can be reduced.

(Embodiment 1)
FIG. 6 shows an example of the configuration of the OLT 14 according to the present embodiment. The OLT 14 according to the first embodiment includes a total of (N + 1) OSUs 15, one CONT 20, and one concentrator switch 40 each including at least one standby OSU 15. Each OSU 15 includes a PON-IF 54, a multicast signal processing unit 53, a multicast control unit 52, and a management table (OSU table) 51 for each ONU. The line concentrator switch 40 includes a multicast signal processing unit 43, a multicast control unit 42, and a management table (concentration switch table) 41 for each OSU. Other configurations unnecessary for the description are omitted.

The OLT 14 of this configuration is assumed to be applied to a PON protection system in which the OSU 15 is made redundant in the presence of a host that uses a multicast video distribution service. As a PON protection system in which the OSU 15 is made redundant, for example, the Type B configuration described in Non-Patent Document 3 or the N: 1 configuration shown in FIG. Here, in the Type B configuration and the N: 1 configuration in FIG. 3, in order to avoid the downstream light of the normal system OSU 15 and the standby system OSU 15 from colliding below the optical coupler 18, the standby system OSU 15 is in the light emission OFF state when normal. In the present invention, the standby OSU 15 is in a light emission OFF state when it is normal. In such a PON protection system in which the OSU 15 is made redundant, when the FW update of the normal OSU 15 is performed, the normal OSU 15 is switched from the corresponding normal OSU 15 to the standby OSU 15 while the FW update of the normal OSU 15 is being performed. The purpose is to update the FW of the OSU 15 without interruption of the video distribution service by the standby OSU 15 taking over communication with the ONU 17. Here, the contents related to multicast will be mainly explained and illustrated. However, in the PON protection system to which this OLT 14 is applied, it is possible to cope with the failure of OSU15, which is the original purpose of PON protection, by the function blocks other than the above. is there. In addition, an OLT 14 configuration in which these are doubled in preparation for failure of the line collecting switch 40 or CONT 20 or the line collecting switch 40 is externally attached is also conceivable.
Hereinafter, the operation of each functional block will be described.

Each functional block of the OSU 15 will be described.
The management table 51 of the OSU 15 is a list that describes the correspondence between the subordinate ONU 17 and the channel being viewed. However, the main management table 51 includes a list for dummy ONUs 17 that do not exist under the main OLT 14. The management table 51 updates the management table 51 in accordance with an update instruction from the multicast control unit 52 in the OSU 15. When the multicast control unit 52 requests acquisition of the contents of the management table 51, the multicast control unit 52 is notified of the table contents at that time.

  The PON-IF 54 receives the multicast frame of the electrical signal from the multicast signal processing unit 53 in the OSU 15, converts it into an optical signal, and outputs it to the outside of the PON-IF 54 (ONU side). In addition, a light emission ON / OFF instruction is received from the multicast control unit 52 in the OSU 15, and light emission is stopped from the light emission state or light emission is started from the light emission stop state according to the instruction.

  The multicast signal processing unit 53 receives the multicast frame and the general query from the line concentrator switch 40. In the case of receiving the former, if the multicast frame is described as being delivered to any ONU 17 in the management table 51 of the same OSU 15, a broadcast address is assigned to the received multicast frame and then transmitted to the PON-IF 54 To do. If not described, the received multicast frame is discarded. When the latter is received, the fact is notified to the multicast control unit 52 of the OSU 15. When a response instruction to the general query is received from the multicast control unit 52 in the OSU 15, a response according to the content is transmitted to the line collecting switch 40. Here, the response to the general query is a message for informing the concentration switch 40 of the channel being delivered to the subordinate ONU 17 based on the management table 51 of the OSU 15 that has received the general query. For example, a multicast listener report in MLD It is equivalent to.

  When the multicast control unit 52 receives the general query reception notification from the multicast signal processing unit 53 in the OSU 15, the multicast control unit 52 acquires the current table contents from the management table 51 in the OSU 15 and distributes the current table contents to the ONU 17 under the current contents. The multicast signal processing unit 53 in the same OSU 15 is instructed to grasp the channel in the middle and respond to the channel number to the line collecting switch 40.

When the table information for registering the list for the dummy ONU 17 is received from the line collecting switch 40, the multicast control unit 52 updates the table to register the contents in the list for the dummy ONU 17 in the management table 51 in the OSU 15. Give instructions. When registration of the dummy ONU 17 in the list is completed, a registration completion notification to that effect is transmitted to the CONT 20.
Further, when receiving a light emission ON / OFF instruction from the CONT 20, the PON-IF 54 in the OSU 15 is instructed to start or stop the light emission according to the contents.

Next, functional blocks of the line collecting switch 40 will be described.
The management table 41 of the line collecting switch 40 is a list in which the correspondence of distribution channels is described in units of OSUs, whereas the management table 51 of OSU 15 is a list in which correspondences of distribution channels are described in units of ONUs 17. However, it is not necessary to provide a list for the non-existent OSU 15 like a list for the dummy ONU 17. The management table 41 of the line collection switch 40 updates the management table 41 in accordance with an update instruction from the multicast control unit 42 of the line collection switch 40. Further, when there is a request for acquisition of table contents from the multicast control unit 42, the table contents at that time are notified to the multicast control unit 42.

  The multicast signal processing unit 43 receives the multicast frame received from the upper OLT 14, and if there is an OSU 15 that is delivering (or requesting) the multicast frame according to the management table 41 of the line concentrator switch 40, the multicast frame is sent to the OSU 15. If there is no OSU 15 being delivered (or requested), the multicast frame is discarded.

  Further, the multicast signal processing unit 43 transmits a general query to all subordinate OSUs 15 in accordance with an instruction from the multicast control unit 42 of the line collecting switch 40. When a response to the general query is received from the subordinate OSU 15, the contents are notified to the multicast control unit 42 of the line collecting switch 40.

  The multicast control unit 42 receives the general query response notification from the multicast signal processing unit 43 of the line collecting switch 40 and the switching OSU information (numbers of the switching source OSU and the switching destination OSU) from the CONT 20. When the former is received, a table update instruction is issued to the management table 41 of the line collecting switch 40 so as to register the channel being distributed to the OSU 15 according to the content. When the latter is received, a table update instruction is issued to the management table 41 of the line concentration switch 40 in order to change the channel that has been distributed to the switching source OSU 15 until then to the switching destination OSU 15. Further, when the table update based on the reception of the switching OSU information is completed, the multicast control unit 42 can issue a registration completion notification to the CONT 20.

  The multicast control unit 42 acquires the table contents from the management table 41, and controls the multicast signal processing unit 43 of the line concentrator switch 40 to appropriately distribute the multicast frame received from the OLT 14 higher level to the OSU 15 based on the contents. Further, in order to register the acquired table contents in the list for the dummy ONU 17 of the management table 51 of the switching destination OSU 15 designated by the CONT 20, the table information for registering the dummy ONU is notified to the multicast control unit 52 of the OSU 15.

  Finally, the CONT 20 notifies the multicast control unit 42 of the line concentration switch 40 of the numbers of the switching source OSU 15 and the switching destination OSU 15 that are grasped through the input of the switching command. Also, a registration completion notification from the multicast control unit 42 of the line concentrator switch 40 and a registration completion notification from the multicast control unit 52 of the OSU 15 are received, and upon receiving these, a light emission ON / OFF instruction is sent to the multicast control unit 52 of the OSU 15. Send.

  By applying the OLT 14 composed of functional blocks as described above to the PON protection system in which the OSU 15 is made redundant, it is possible to avoid the video service interruption of the ONU 17 due to OSU switching.

  FIG. 7 shows an OSU switching procedure by an operation operation in the PON system in which the OSU 15 is made redundant using the OLT 14. Here, it is assumed that the system is applied to the system shown in FIG.

  In such a system, when switching from OSU # 1 (switching source OSU) to OSU # 3 (switching destination OSU), first, a switching command specifying these OSUs 15 is input to the CONT 20. As a result, since the switching OSU information is notified from the CONT 20 that the OSU # 1 is the switching source and the OSU # 3 is the switching destination, the concentrating switch 40 displays its own OSU unit management table 41. Update from 8 to as shown in FIG.

When the update of the table is completed, the line collection switch 40 notifies the list registration table information for the dummy ONU 17 so that Ch1 and Ch2 are registered in the list for the dummy ONU 17 of the management table 51 of OSU # 3. The OSU # 3 that has received the notification registers the list for the dummy ONU 17 and updates its management table 51 as shown in FIGS. 9 to 11, and notifies the CONT 20 that the registration of the list for the dummy ONU 17 is completed. . The CONT 20 receives the list registration completion notification from the OSU # 3 to the dummy ONU 17,
-OSU # 3 can deliver Ch1 and Ch2 to the ONU 17 under control.
-Even if the line concentrator switch 40 sends a general query to OSU # 3, the distribution of Ch1 and Ch2 will not be stopped.
In order to perform OSU switching, a light emission OFF instruction is transmitted to OSU # 1, and a light emission ON instruction is transmitted to OSU # 3. The OSU # 1 that has received the light emission OFF instruction stops the light emission. The OSU # 3 that has received the light emission ON instruction starts light emission, and transmits the Ch1 and Ch2 multicast frames transmitted from the line collecting switch 40 to the newly subordinate ONUs 17 (ONU1, 2).

  As described above, after the list for the switching destination OSU 15 in the management table 41 of the line collecting switch 40 is updated, the OSU switching is performed without interruption of the video service by the OSU switching procedure for updating the list for the dummy ONU 17 in the management table 51 of the switching destination OSU 15. Can be completed.

  Here, after the concentration switch 40 starts to distribute the channel registered in the list for the switching destination OSU 15 in its own management table 41 to the switching destination OSU 15, it is before the switching destination OSU 15 registers the list for the dummy ONU 17. Consider a case where 40 transmits a general query to the switching destination OSU 15. As described above, when the switching destination OSU 15 that has received the general query responds to the concentration switch 40 based on the unregistered table contents before registering the list for the dummy ONU 17, the concentration switch 40 switches to the switching destination. Distribution to the OSU 15 is stopped. In preparation for such a case, it is desirable to perform the following operations.

Operation 1: The line concentrator switch 40 immediately updates the list for the switching destination OSU 15 of its own management table 41 and immediately notifies the concentrator switch 40 of the list registration table information for the dummy ONU 17 Operation 2: The switching destination OSU 15 notifies the dummy ONU 17 When a general query is received from the line concentrator switch 40 while the list is being registered, it waits for the registration of the list to the dummy ONU 17 and then responds to the line concentrator switch 40 based on the updated management table 51.

  By such a method, even if the line concentrator switch 40 sends a general query to the switching destination OSU 15 before registering the list for the dummy ONU 17, the line concentrating switch 40 does not stop the distribution to the switching destination OSU 15, and therefore the OSU switching Video service interruptions associated with can be avoided.

  After OSU switching, the management table 51 of the switching destination OSU 15 responds to a viewing / leaving request from a host connected to the subordinate ONU 17 and a response to the general query transmitted from the switching destination OSU 15 to the subordinate ONU 17. By being updated, the steady state is restored. Note that since the dummy ONU 17 does not respond to the general query, the list for the dummy ONU 17 is not viewed after a while after OSU switching.

(Embodiment 2)
The OSU switching procedure in the first embodiment is as follows:
1. 1. Update management table 41 (list for switching destination OSU) of line collecting switch 40 Although the order of updating the management table 51 (list for dummy ONU) of the switching destination OSU 15 is the order, there is no problem even if this order is reversed. FIG. 12 shows an OSU switching procedure for updating the management table 41 of the line collecting switch 40 after updating the management table 51 of the switching destination OSU 15 first in the present embodiment.

  When a switch command is input to the CONT 20, the switch OSU information is notified to the line concentrator switch 40, and the line concentrator switch 40 that has received the information is a dummy to the switch destination OSU 15 before updating the list for the switch destination OSU 15 in its own management table 41. The list registration table information for the ONU 17 is notified. Here, in the first embodiment, when the list registration table information for the dummy ONU 17 is notified, the management table 41 of the line collection switch 40 has been updated. Therefore, the contents of the list registration table information for the dummy ONU 17 are updated. In the present management table 41, the channel number is being distributed to the switching destination OSU 15, but in this embodiment, when the list registration table information for the dummy ONU 17 is notified, the management table 41 of the line concentrator switch 40 is not updated. Therefore, the content of the list registration table information for the dummy ONU 17 is the channel number in the distribution of the list to the switching source OSU 15 in the management table 41 of the concentration switch 40 before the update.

  When the switching destination OSU 15 completes the registration of the list for the dummy ONU 17, it notifies the CONT 20 of a list registration completion notification for the dummy ONU 17. Instruct you to. The switching destination OSU 15 directly notifies the concentration switch 40 of the list registration completion notification for the dummy ONU 17, and the concentration switching switch 40 starts updating the list for the switching destination OSU 15 in its management table 41 when the notification is received. May be.

  When the line collection switch 40 updates the list for the switching destination OSU 15 in its own management table 41, it sends a registration completion notification to the CONT 20, and the CONT 20 may perform OSU switching in the same manner as in the first embodiment upon receiving this notification. The light emission ON / OFF instruction may be transmitted to the switching destination OSU / switching source OSU, respectively.

  As described above, even when the list for the switching destination OSU 15 in the management table 41 of the line collecting switch 40 is updated after the list for the dummy ONU 17 in the management table 51 of the switching destination OSU 15 is updated, the OSU switching is performed without interruption of the video service. Can be completed. However, when the OSU switching procedure of FIG. 12 is adopted, in the configuration of the OLT 14 of FIG. 6, as a message to be notified from the CONT 20 to the multicast control unit 42 of the concentration switch 40, the management table of the concentration switch 40 is separated from the notification of the switching OSU information. A table update instruction for instructing only 41 updates is added.

(Embodiment 3)
In the first and second embodiments, the OSU switching procedure for updating either the list for the switching destination OSU 15 in the management table 41 of the line collecting switch 40 or the list for the dummy ONU 17 in the management table 51 of the switching destination OSU 15 and then updating the other table. showed that. In this embodiment, the OSU switching procedure for updating both tables in parallel is shown in FIG.

  Upon receiving the switching OSU information from CONT 20, the line concentrator switch 40 starts updating the list for the switching destination OSU 15 in its management table 41 and notifies the switching destination OSU 15 of the list registration table information for the dummy ONU 17. The CONT 20 switches the light emission ON / OFF instruction when the CONT 20 receives both of the registration completion notifications notified to the CONT 20 when the update of the respective tables is completed at the line concentrator switch 40 and the switching destination OSU 15. What is necessary is just to transmit to destination OSU15 / switch source OSU15.

  As described above, the video service is also performed by the OSU switching procedure in which the list updating operation for the dummy ONU 17 in the management table 51 of the switching destination OSU 15 and the list updating operation for the switching destination OSU 15 in the management table 41 of the line collecting switch 40 are performed in parallel. OSU switching can be completed without interruption.

  In this embodiment as well, the operation 2 described in the first embodiment may be satisfied in preparation for the case where the line concentrator switch 40 transmits the general query to the switching destination OSU 15 before the list is registered for the dummy ONU 17 in the switching destination OSU 15. desirable.

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

10: Optical transmission line 11: PON
12: L2SW
13: Core network 14: OLT
15: OSU
16: N × 1 optical switch 17: ONU
18: Optical coupler 19: Optical fiber 20: Control panel (CONT)
21: User terminal (host)
31: Multicast router 32: Video distribution server 40: Concentration switch 41, 51: Management table 42, 52: Multicast control unit 43, 53: Multicast signal processing unit 54: PON-IF

Claims (6)

A plurality of OSUs (Optical Subscriber Units) each having a multicast table (hereinafter referred to as an OSU table) including a list of delivery channels of each ONU (Optical Network Unit) connected to itself ;
It has a multicast table (hereinafter referred to as a concentrator switch table) that stores a list of channels to be distributed by each ONU connected to the OSU for each OSU, and sends data to be distributed by multicast to the OSU based on the concentrator switch table. Concentrating switch to distribute,
An optical communication system comprising:
The OSU table, only contains a list of the delivery channel of one of the dummy ONU that is not connected with any of the OSU,
The concentrator switch is
When the connection destination of the ONU is switched from one OSU (hereinafter referred to as switching source OSU) to another OSU (hereinafter referred to as switching destination OSU),
A list takeover process for taking over the list of channels of the switching source OSU in the line collection switch table to the list of channels of the switching destination OSU in the line collection switch table;
An update instruction process for transmitting an update instruction for registering the list of channels as a distribution channel list of the dummy ONU in the OSU table to the switching destination OSU;
An optical communication system, characterized in that: The concentrator switch, triggered by the completion of the list takeover process, carried out before Symbol update instruction process,
The switching destination OSU is in accordance with the update instruction received from the concentrator switch, and updates the list of distribution channels of said dummy ONU at its front SL O SU table, initiates communication with the ONU,
The optical communication system according to claim 1, wherein: The concentrator switch performs the update instruction process, and issues a registration completion notification after the completion of the list takeover process,
The switching destination OSU is, according to the update instruction received from the concentrator switch, to update the list of the delivery channel of the dummy ONU in self before Symbol O SU table, triggered by the issuance of the registration completion notification from the collection line switch Start communication with ONU
The optical communication system according to claim 1, wherein: The line concentrator switch performs the update instruction process after the start of the list takeover process, and issues a registration completion notification after the list takeover process is completed.
The switching destination OSU is in accordance with the update instruction received from the concentrator switch, and updates the list of distribution channels of said dummy ONU at its front SL O SU table, before Symbol O SU table update and from the concentrator switch Communicating with the ONU when the registration completion notification issuance is completed,
The optical communication system according to claim 1, wherein: OSU according to any one of claims 1 to 4. The line collecting switch according to any one of claims 1 to 4 .

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