JP2011071951A - Optical communication system and optical communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical communication system and optical communication method of PON protection, capable of suppressing reduction in the number of ONUs to be accommodated at normal times, with respect to the maximum number of ONUs to be accommodated for each OLT by having the conventional N:M protection developed. <P>SOLUTION: In an optical communication system includes a system configuration, in a PON system connecting a plurality of ONUs and OLTs via a first splitter and a second splitter, where a controller is connected to each OLT; a switching device for making a connection destination OLT of an ONU changeable through the controller is connected between the first splitter and the second splitter; one branch of the first splitter is opened for switching; and when the controller discovers an OLT failure, the controller controls the switching device so that an ONU which is to be connected to the relevant OLT is connected to other normal OLTs, while verifying the band to be used for each OLT. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a PON system using a redundancy technology and having a protection function.

  As broadband spreads, network communication plays an increasingly important role, and it is required to provide a stable service. In particular, Passive Optical Network (PON), which is a widely used communication method, has one station-side terminal device (OLT: Optical Line Terminal) per N: 1 splitter and a plurality of (for example, 32) subscriber-side terminal devices (for example, 32 devices). ONU (Optical Network Unit) is connected, and the fiber between the OLT and the OLT-N: 1 splitter is shared by N ONUs. For this reason, if a service interruption occurs due to a fiber break or OLT failure in the shared portion, there is a possibility that the influence may affect a large number of users. Therefore, in order to supply a stable service, it is important to make the OLT and the path redundant in preparation for a device failure or a fiber break.

  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, see Non-Patent Document 1). For example, a method in which the correspondence between active and backup is 1: 1, such as providing one backup device for one active device, is referred to as 1: 1 protection. There are four descriptions of types A to D. FIG. 1 is a block diagram illustrating an optical communication system employing Type B 1: 1 protection. Type B is a method of making redundant between the OLT and the splitter, which has a great influence at the time of device failure or fiber breakage, and can be realized at a lower cost than the type C and type D that make redundant between the OLT and the ONU. However, twice as many OLTs and shared fibers are required as compared with the case where redundancy is not provided. Therefore, the cost of the OLT and the shared fiber borne by each user is doubled compared to the case where no redundancy is made.

  Other protection methods that can reduce the redundant OLT additional cost per user due to OLT redundancy have been proposed (see Non-Patent Document 2, for example). This method is called N: 1 protection because the correspondence between active and backup is N: 1. FIG. 2 is a block diagram illustrating an optical communication system employing N: 1 protection. The difference between N: 1 protection and type B in FIG. 1 is that there is one backup OLT that does not transmit data for N active OLTs at normal times, and an optical switch is used. . Assuming that the maximum number of ONUs that can be accommodated per OLT is A, the normal active OLT communicates with ONUs of A or less. When one of the N active OLTs fails, the backup OLT communicates with the ONUs under the failure OLT via the optical switch. With N: 1 protection, the additional cost of one backup OLT can be shared by users under N OLTs. Therefore, the redundant OLT additional cost per user in N: 1 protection can be reduced as compared with the case of 1: 1 protection.

  However, for both N: 1 protection and 1: 1 protection, the backup OLT is not used at all when the active OLT is normal, and bears the cost of redundant equipment due to the short time between the failure of the active OLT and the repair. The point of having to do it was a problem of cost reduction.

  Therefore, a protection method has been proposed that does not require data transmission during normal operation and does not require a device that performs only during failure (see, for example, Non-Patent Document 3). This method is called N: M protection because N loads are distributed by M units. FIG. 3 is a block diagram illustrating an optical communication system employing N: M protection.

  In this N: M protection, four OLTs each capable of accommodating a maximum of 64 ONUs communicate with 32 ONUs at normal times. An optical switch is arranged between the OLT and the splitter so as to cross the path under each OLT. When one OLT fails, one of the remaining three OLTs is under the failure OLT via the optical switch. It is possible to communicate with all ONUs (32 units). That is, one normal OLT takes over all ONUs under the fault OLT, and communicates with a total of 64 ONUs including the 32 units taken over from the original 32 subordinates. Further, the fibers between the N: 2 splitter and the optical switch are duplexed, and it is possible to cope with the fiber breakage at this point.

  This N: M protection is different from 1: 1 and N: 1 protection, and has a protection function capable of avoiding communication disconnection even when an OLT failure occurs while all OLTs are active. In addition, if the number is 1: 1 or N: 1 for 128 ONUs in total, 2 active OLTs are accommodated (the maximum capacity that can be accommodated per OLT is 64), so that 128 users can be assigned to 128 users. The bandwidth is equivalent to 2 OLTs, but in this system, 2 OLTs are added and a total of 4 OLTs are active, so the bandwidth allocated to 128 users is equivalent to 4 OLTs. In other words, in this system, the extra bandwidth for the two added OLTs can be allocated to the user even at the normal time, so the bandwidth per user at the normal time is doubled compared to 1: 1 or N: 1.

  In the optical communication system of FIG. 3, originally, 64 OLTs that can accommodate 128 ONUs by 2 OLTs are accommodated 32 by 4 OLTs and the load is distributed. Therefore, the optical communication system of FIG. 3 can be said to have a 2: 4 protection configuration from the viewpoint of N: M protection.

  As described above, this protection method does not require a device that does not perform data transmission during normal operation and performs only during a failure. In addition, the normal operation can allocate an extra OLT surplus bandwidth to the ONU during normal operation. This is an advantage over protection and N: 1 protection.

"SEREIES G: TRANSMISSION SYSTEM AND MEDIA, DIGITAL SYSTEMS AND NETWORKS; Digital transmission systems - Digital sections and digital line system - Optical line systems for local and access networks; Broadband optical access systems based on Passive Optical Networks (PON)", ITU- T, G. 983.1, p. 107-109 K. Tanaka and Y.M. Horizon, “1: N OLT Redundant Protection Architecture in Ethernet (registered trademark) PON System,” OFC / NFOEC, pp. 1-6, 2008. W. T.A. P'ng, S.M. Khatun et al. "A Novel Protection Scheme for Ethernet (R) PON FTTH Access Network," IEEE International Conference on Networks, Vol. 1, pp. 487-490, 2005.

  However, in the conventional N: M protection system of FIG. 3, all the ONUs under the fault OLT are collectively transferred to another OLT. For this reason, the number of ONUs that can be accommodated per OLT in a normal state is reduced by half (from 64 to 32) in preparation for the ONU takeover at the time of another OLT failure. That is, the number of OLTs required to accommodate the same number of users is doubled as compared with the case without redundancy. Therefore, when accommodating the same number of users as in the case without redundancy, there is a problem that the OLT cost per user is doubled compared to the OLT cost without redundancy.

  In order to solve this problem, the present invention develops conventional N: M protection and suppresses a reduction in the number of ONUs in a normal state with respect to the maximum number of ONUs in each OLT, and an optical communication system and an optical communication for PON protection It aims to provide a method.

  In order to achieve the above object, the optical communication system and the optical communication method according to the present invention employs an N: M protection method in which ONUs under the fault OLT are distributed and inherited to a plurality of OLTs.

  Specifically, the first optical communication system according to the present invention includes M (M is an integer of 2 or more) station-side terminal devices and a branching ratio of 1: X (X is an integer of 2 or more). For each of the station-side terminators, the merging side is connected to one of the station-side terminators, the branch side is connected to X first branch fibers, and K (K is 2 or more and (M -1) An integer equal to or less than X) One branch fiber and a branching ratio of 1: Y (Y is an integer of 2 or more), and for each branch fiber, the merging side is connected to one of the branch fibers. K second splitters whose sides are connected to Y second branch fibers, and Z (Z is a natural number equal to or less than K × Y) connected to any one of K × Y second branch fibers. Arbitrary combinations of subscriber-side terminator, branch fiber and first branch fiber connected at 1: 1 And a switching device that enables instead of viewing.

  The present optical communication system includes a switching device that can freely recombine the connection between the first branch fiber and the branch fiber. The switching device can reconnect the branch fiber that was communicating with the failed OLT to the open first branch fiber that is connected to the other OLT. Here, a plurality of branch line fibers whose communication has been interrupted by the switching device are dispersed and connected to a plurality of open first branch fibers. Thereby, it can avoid that load concentrates on specific OLT at the time of abnormality. That is, since the N: M protection is possible even if the capacity of the ONU remaining in the OLT is small, the number of ONUs accommodated in the OLT at the normal time can be increased.

  Therefore, the present invention can provide an optical communication system for PON protection that can develop conventional N: M protection and can suppress a reduction in the number of ONUs in a normal state with respect to the maximum number of ONUs in each OLT.

  The first optical communication system according to the present invention obtains registration information and failure information of each of the subscriber-side terminators from all the station-side terminators, and the branch fiber is normally supplied to the switching device. At least one or more of the first branch fibers in an open state that are not connected to each of the first splitters, and issues a connection instruction to connect the branch fiber and the first branch fiber; When an incommunicable path occurs between the terminating device and the subscriber-side terminating apparatus, the open first state is connected to the first splitter in the communicable path through the branch fiber of the incommunicable path. A controller is further provided that issues a switching instruction to reconnect to one of the one branch fibers.

  Further, the optical communication method in the first optical communication system according to the present invention obtains registration information and failure information of each of the subscriber-side terminators from all the station-side terminators, and the switching device normally The branch fiber and the first branch fiber are connected so that there is at least one or more of the first branch fiber in an open state that is not connected to the branch fiber for each first splitter, and the station-side termination is connected. When an incommunicable path is generated between a device and the subscriber-side terminal device, the first state in an open state is connected to the first splitter of the path capable of communicating the branch fiber of the incommunicable path It is characterized by reconnecting to one of the branch fibers.

  When the controller finds a failure of the OLT, the controller controls the switching device so that the ONU connected to the OLT is connected to another normal OLT. Therefore, this invention can implement | achieve the optical communication system of the PON protection which can reduce OLT cost, and its optical communication method.

  Specifically, the second optical communication system according to the present invention includes M (M is an integer of 2 or more) station-side terminal devices and a branching ratio of 1: X (X is an integer of 2 or more). For each of the station-side terminators, the merging side is connected to one of the station-side terminators, the branch side is connected to X first branch fibers, and K (K is 2 or more and (M -1) X or less integer) branch fiber, L spare fibers arranged in parallel with L (L is an integer not less than 1 and not more than K) of the branch fibers, and the branching ratio is 1. : Y (Y is an integer of 2 or more), and for each branch fiber, KL second splitters in which the merge side is connected to one of the branch fibers and the branch side is connected to Y second branch fibers. And the branching ratio is 2: Y (Y is an integer of 2 or more), and the merging side is the branch line for each branch fiber. Any one of L third splitters connected to one of the fibers and the spare fiber in parallel with the branch fiber and connected to Y second branch fibers on the branch side, and any of K × Y second branch fibers When Z (Z is a natural number equal to or less than K × Y) number of subscriber-side terminators connected to each other and the branch fiber connected at 1: 1, or the branch fiber and the backup fiber are connected in parallel A switching device that can arbitrarily recombine the pair of either one and the first branch fiber.

  In this optical communication system, the branch fiber is made redundant in addition to the protection described in the first optical communication system. The present optical communication system can also protect between the OLT and the switching device and between the switching device and the second splitter.

  The second optical communication system according to the present invention acquires registration information and failure information of each of the subscriber-side terminators from all the station-side terminators, and normally sends the branch line fiber to the switching device. At least one or more of the first branch fibers in an open state that are not connected to each of the first splitters, and issues a connection instruction to connect the branch fiber and the first branch fiber; When an incommunicable path occurs between the terminating apparatus and the subscriber-side terminating apparatus, if there is a cause of incommunicable communication between the station-side terminating apparatus and the switching device, the incommunicable path A switching instruction is issued so that the branch fiber is reconnected to one of the open first branch fibers connected to the first splitter on the communicable path, and the branch fiber is aligned with the spare fiber. If the certain cause of communication failure in the branch line fiber, further comprising a controller issues a switching instruction to re-connect said supporting line fiber to said protection fiber to.

  Further, the optical communication method in the second optical communication system according to the present invention obtains registration information and failure information of each of the subscriber-side terminators from all the station-side terminators, and in the switching device during normal time The branch fiber and the first branch fiber are connected so that there is at least one or more of the first branch fiber in an open state that is not connected to the branch fiber for each first splitter, and the station-side termination is connected. If there is a cause of communication failure between the station-side termination device and the switching device when a communication-disabled route occurs between the device and the subscriber-side termination device, the branch line of the communication-disabled route The branch line which is reconnected to one of the open first branch fibers connected to the first splitter of the path through which the fiber can communicate, and is parallel to the backup fiber If there is a cause of communication failure in Aiba, characterized in that reconnect from said supporting line fiber to the protection fiber.

  In addition to the confirmation described in the first optical communication system, the controller also confirms the state of the branch fiber, and controls the switching device to switch to the backup fiber in parallel when there is an abnormality.

  The controllers of the first optical communication system and the second optical communication system according to the present invention have also acquired the bandwidth usage rate of the subscriber-side termination device, and the switching device is connected to the station-side termination device and the When communication failure occurs with the switching device, the highest load among the branch fibers of the route that cannot be communicated based on the bandwidth utilization rate obtained from any point in time until communication failure occurs. A switching instruction is issued so as to connect to the first branch fiber in an open state connected to the station-side terminator having the lowest load in order from the first.

  Further, the optical communication method in the first optical communication system and the second optical communication system according to the present invention also acquires the bandwidth utilization rate of the subscriber-side termination device, and between the station-side termination device and the switching device. When communication failure occurs, the lowest load in order from the highest load among the branch fibers of the route where communication is impossible, based on the bandwidth utilization obtained from the arbitrary time until communication failure occurs It connects to the said 1st branch fiber of the open state connected to the said station side termination | terminus apparatus.

  The controller confirms the bandwidth used by each OLT, and controls the switching device so that the ONU is connected to the OLT having a sufficient bandwidth. Therefore, the present invention can realize a PON protection optical communication system and an optical communication method thereof that can efficiently use a band and reduce OLT costs.

  The controllers of the first optical communication system and the second optical communication system according to the present invention also acquire the bandwidth usage rate of the subscriber-side terminating device, and can perform any period or arbitrary moment for the switching device. Based on the obtained bandwidth utilization ratio, the branch fiber having the highest load is switched to be connected to the first branch fiber in the open state connected to the station-side terminating device having the lowest load. It is characterized by issuing instructions.

  In addition, the optical communication method in the first optical communication system and the second optical communication system according to the present invention also acquires the bandwidth usage rate of the subscriber-side terminating device and acquires the bandwidth usage acquired at an arbitrary period or at an arbitrary moment. Based on the rate, the branch fiber having the highest load is connected to the first branch fiber in the open state connected to the station-side terminating device having the lowest load.

  The controller confirms the used bandwidth of each OLT even when it is not at fault, and controls the switching device so that the ONU is connected to the OLT having a sufficient bandwidth. Therefore, the present invention can realize a PON protection optical communication system and an optical communication method thereof that can efficiently use a band and reduce OLT costs.

  The third optical communication system according to the present invention includes M (M is an integer of 2 or more) station-side termination devices capable of accommodating a maximum of A subscriber terminals (A is an integer of 2 or more), and a branching ratio. Is 1: M, and for each of the station-side terminators, M first splitters whose merging side is connected to one of the station-side terminators and a branching ratio of 1: M−1, Each time, the M optical switches are connected to one port on the branch side of the first splitter on the merge side, and the branch ratio is 2: Y ′ (Y ′ is an integer satisfying 2 or more and A / M or less). , (M-1) × M second or less second splitters and (M-1) × Y ′ × M or less subscribers connected to each port on the Y ′ side branch number of the second splitter 1 terminal unit, another port on the branch side of the first splitter, and one port on the side where the number of branches of the second splitter is 2 1 for each of the first splitters connected by K (K is an integer not less than 2 and not more than (M−1) × M) and the first splitters connected by the branch fibers. Forming a group, and the second splitter belonging to one group is coupled to the optical switches belonging to different other groups. And K spare branch fibers that connect the port and the port on the side where the number of branches of the optical switch is M-1 on a 1: 1 basis.

  This optical communication system includes an optical switch and a backup branch fiber. The spare branch fiber is connected to the second splitter of another group. When one OLT fails, the second splitter under the OLT can be distributed to another OLT using the optical switch and the spare branch fiber. it can. Thereby, it can avoid that load concentrates on specific OLT at the time of abnormality. That is, since the N: M protection is possible even if the capacity of the ONU remaining in the OLT is small, it is possible to increase the number of ONUs accommodated in the normal OLT.

  Therefore, the present invention can provide an optical communication system for PON protection that can develop conventional N: M protection and can suppress a reduction in the number of ONUs in a normal state with respect to the maximum number of ONUs in each OLT.

  The third optical communication system according to the present invention obtains registration information and failure information of each of the subscriber-side termination devices from all the station-side termination devices, and the station-side termination device and the subscriber side When a path that cannot be communicated with the terminating device occurs, the spare branch line is set so that the spare branch fiber connected to the second splitter to which the branch fiber used by the path is connected becomes a new path. A controller that issues a switching instruction to the optical switch to which the fiber is connected is further provided.

  Further, the optical communication method in the third optical communication system according to the present invention acquires registration information and failure information of each of the subscriber-side termination devices from all the station-side termination devices, and the station-side termination When a path incapable of communication between a device and the subscriber-side terminating device occurs, the backup branch fiber connected to the second splitter connected to the branch fiber used by the path is set as a new path. It is characterized by switching to do.

  When the controller discovers that an incommunicable path has occurred between the OLT and the ONU, the controller controls the optical switch so that the ONU connected to the OLT is connected to another normal OLT. Therefore, this invention can implement | achieve the optical communication system of the PON protection which can reduce OLT cost, and its optical communication method.

  The third optical communication system according to the present invention further includes a branch optical shutter disposed on the branch fiber and blocking an optical signal propagating through the branch fiber. In addition, when a path that cannot be communicated between the station-side terminator and the subscriber-side terminator is generated, the controller uses the branch optical shutter disposed on the branch fiber used by the path. The route is blocked.

  By shutting off the branch line optical shutter on the path where communication is impossible, it is possible to prevent the downstream optical signal from reaching the ONU from the two OLTs when the repair of the OLT or the repair of the branch line fiber is completed.

  The fourth optical communication system according to the present invention includes M (M is an integer of 2 or more) station-side termination devices capable of accommodating a maximum of A subscriber terminals (A is an integer of 2 or more), and a branching ratio. Is 1: (M−1) × 2, and for each of the station-side terminators, the M first splitters whose merging side is connected to one of the station-side terminators, and the branching ratio is 2: Y ′ (Y 'Is an integer satisfying 2 or more and A / M or less), and (M−1) × M or less second splitters are connected to each port on the side where the number of branches of the second splitter is Y ′ ( M−1) × Y ′ × M or less subscriber-side terminators, M−1 ports that are one set of the branch side of the first splitter, and the number of branches of the second splitter are two K branch cables (K is an integer of 2 or more and (M−1) × M or less) connecting the 1 port of For each of the first splitters to be connected, the first splitter and the second splitter form a group, and the second splitter belonging to one of the groups belongs to another different group. To connect the other port on the side where the number of branches of the second splitter is 2 and the M−1 ports which are the other set on the branch side of the first splitter in a ratio of 1: 1. A spare branch fiber, and a spare optical shutter disposed on the spare branch fiber and blocking an optical signal propagating through the spare branch fiber.

  The present optical communication system includes a spare optical shutter and a spare branch fiber. The spare branch fiber is connected to the second splitter of another group, and when one OLT fails, the spare splitter and the spare branch fiber are used to distribute the second splitter under the OLT to the other OLT. Can do. Thereby, it can avoid that load concentrates on specific OLT at the time of abnormality. That is, since the N: M protection is possible even if the capacity of the ONU remaining in the OLT is small, the number of ONUs accommodated in the OLT at the normal time can be increased.

  Therefore, the present invention can provide an optical communication system for PON protection that can develop conventional N: M protection and can suppress a reduction in the number of ONUs in a normal state with respect to the maximum number of ONUs in each OLT.

  The fourth optical communication system according to the present invention obtains registration information and failure information of each of the subscriber-side terminal devices from all the station-side terminal devices, and normally uses the standby optical shutter for the standby optical device. When the path of the branch fiber is cut off and a path incapable of communication occurs between the station-side terminal device and the subscriber-side terminal apparatus, the branch fiber used by the path is connected to the first fiber A controller that issues an opening instruction to the auxiliary optical shutter to which the auxiliary branch fiber is connected so that the auxiliary branch fiber connected to the two splitters becomes a new path;

  Further, the optical communication method in the fourth optical communication system according to the present invention acquires registration information and failure information of each of the subscriber-side termination devices from all the station-side termination devices, When the path of the backup branch fiber is blocked by a backup optical shutter and an incommunicable path is generated between the station-side terminating device and the subscriber-side terminating device, the branch used by the path is used. The auxiliary optical shutter connected to the auxiliary branch fiber is opened so that the auxiliary branch fiber connected to the second splitter to which the fiber is connected becomes a new path.

  When the controller discovers that a path that cannot be communicated between the OLT and the ONU has occurred, the controller controls the spare optical shutter so that the ONU connected to the OLT is connected to another normal OLT. . Therefore, this invention can implement | achieve the optical communication system of the PON protection which can reduce OLT cost, and its optical communication method.

  The fourth optical communication system according to the present invention further includes a branch optical shutter arranged on the branch fiber and blocking an optical signal propagating through the branch fiber. In addition, the controller keeps the branch line optical shutter open at normal times, and when a path that cannot be communicated between the station-side terminator and the subscriber-side terminator occurs, the controller uses the path. Further, the path is interrupted by the branch line optical shutter arranged in the branch line fiber.

  By shutting off the branch line optical shutter on the path where communication is impossible, it is possible to prevent the downstream optical signal from reaching the ONU from the two OLTs when the repair of the OLT or the repair of the branch line fiber is completed.

A fifth optical communication system according to the present invention includes M (M is an integer of 2 or more) station-side termination devices capable of accommodating a maximum of A subscriber terminals (A is an integer of 2 or more), and a branching ratio. Is 1: (M−1) × M, and for each of the station-side terminators, the M first splitters whose merging side is connected to one of the station-side terminators and the branching ratio are M: Y ′ (Y 'Is an integer greater than or equal to 2 and satisfying A / M), and (M-1) × M or less second splitters are connected to each port on the side where the number of branches of the second splitter is Y ′ (M -1) No more than × Y ′ × M subscriber-side terminators, M−1 ports that are one set on the branch side of the first splitter, and the number of branches of the second splitter on the M side 1 K port (K is an integer of 2 or more and (M−1) × M or less) branch cables connected by 1: 1, and the branch fiber is connected. For each of the first splitters, the first splitter and the second splitter form a group, and the other branch ports of the second splitter belonging to one group are different from each other on the M side. The number of branches of the second splitter is the other set on the branch side of the first splitter and the other branch on the branch side of the first splitter so as to be coupled to the first splitter belonging to the group (M−1) ^2. K × (M−1) spare branch fibers that connect the ports 1: 1, and a spare optical shutter that is disposed on the spare branch fiber and blocks an optical signal propagating through the spare branch fiber; A branch line optical shutter disposed on the branch line fiber and blocking an optical signal propagating through the branch line fiber.

  The difference between the fifth optical communication system and the fourth optical communication system is that all ONUs can be connected to any OLT by path switching, and load distribution is enabled. The fifth optical communication system can also distribute the load of the OLT.

  The sixth optical communication system according to the present invention includes M (M is an integer of 2 or more) station-side termination devices capable of accommodating a maximum of A (A is an integer of 2 or more) subscriber-side termination devices, and a branching ratio. Is 1: B (B is an integer greater than or equal to M), and for each station-side termination device, the merging side is connected to each of the first splitters and M first splitters connected to one of the station-side termination devices. And M branch line optical shutters for opening and closing B optical paths coupled to the B ports on the branch side of the first splitter, respectively, and a branching ratio of M: Y ″ (Y ″ is 2 or more and A / B number of second splitters that are equal to or less than B− (M−1)}, and the number of branches of the second splitter is less than or equal to B × Y ′ number connected to each port on the Y ′ side. A subscriber-side terminator, a B optical path of the branch line optical shutter, and a port on the M side where the number of branches of the second splitter is M side. And B × M branch fibers that are connected in a 1: 1 ratio, and the branch light shutter opens at least one optical path for each of the first splitters, and each of the second splitters The number of paths formed at any time with any of the first splitters is 1 or 0.

  Unlike the fifth optical communication system, the sixth optical communication system has no limitation on the number of ONUs accommodated by the OLT. The sixth optical communication system has a higher degree of freedom of load distribution than the fifth optical communication system.

  The fifth optical communication system and the sixth optical communication system obtain the bandwidth utilization rate of the subscriber-side termination device for any period or arbitrary moment from all the station-side termination devices, And a controller for switching the branch line optical shutter and reconnecting the second splitter to the first splitter so that a bandwidth utilization factor is substantially equal. The controller issues a reconnection instruction to the branch line optical shutter. To do.

  Further, the optical communication methods in the fifth optical communication system and the sixth optical communication system according to the present invention include the subscriber-side terminations in any period or in any moment from all the station-side termination apparatuses. A bandwidth utilization factor of the apparatus is acquired, and the branch light shutter is switched so that the second splitter and the first splitter are reconnected so that the bandwidth utilization rates are substantially equal.

  When the controller discovers that a path that cannot be communicated between the OLT and the ONU has occurred, the controller controls the spare optical shutter so that the ONU connected to the OLT is connected to another normal OLT. . Therefore, this invention can implement | achieve the optical communication system of the PON protection which can reduce OLT cost, and its optical communication method.

  The present invention can provide an optical communication system and an optical communication method for PON protection that can develop conventional N: M protection and can suppress a reduction in the number of ONUs in a normal state with respect to the maximum number of ONUs in each OLT.

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  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. Moreover, when it demonstrates without attaching | subjecting a branch number to a code | symbol, it is description common to all the branch numbers of the code | symbol.

(Embodiment 1)
FIG. 4 is a block diagram illustrating the optical communication system 301 of the present embodiment. The optical communication system 301 has M (M is an integer of 2 or more) OLTs 11 and a branching ratio of 1: X (X is an integer of 2 or more). For each OLT 11, the merging side is connected to one of the OLTs 11, M first splitters 12 connected to X first branch fibers 13 on the branch side, K (K is an integer of 2 or more and (M−1) × X or less) branch fibers 14, and a branching ratio is 1: Y (Y is an integer of 2 or more), and for each branch fiber 14, K second splitters in which the merge side is connected to one of the branch fibers 14 and the branch side is connected to Y second branch fibers 18. 15, Z (Z is a natural number equal to or less than K × Y) ONUs 16 connected to any one of the K × Y second branch fibers 18, the branch fiber 14 connected in a 1: 1 ratio, and the first The pair with the branch fiber 13 can be arbitrarily changed. It provided with a replacement device 17, a.

  In the configuration of the optical communication system 301, M OLTs 11 are connected to one side of the first splitter 12 having a branching ratio of 1: X. The X side of the first splitter 12 is connected to the switching device 17 via X first splitter fibers 13 in a total of M × X per splitter. In addition, from the lower side (ONU side) of the switching device 17, K branch fibers 14 are connected to one side of the second splitter 15 having a branching ratio of 1: Y. Y second branch fibers 18 are connected to the Y side of the second splitter 15, and up to Y ONUs 16 can be connected respectively. That is, the optical communication system 301 can connect a maximum of K × Y ONUs 16.

  The switching device 17 can connect the K branch fibers 14 and any first branch fiber 13, and can arbitrarily change the combination of connections between the branch fibers 14 and the first branch fiber 13. The switching device 17 is an optical switch or an optical shutter using, for example, MEMS (micro electro mechanical systems).

  Here, “switching” changes the connection of an arbitrary branch fiber 14 connected to the first branch fiber 13 by the switching device 17 to another first branch fiber 13 (corresponding to M × X−1). Represents that. Therefore, the branch fiber 14 is not switched to another branch fiber 14.

  In order to enable such switching, the relationship between the number of M × X first branch fibers 13 and K branch fibers 14 satisfies K ≦ (M−1) × X. Since the switching device 17 connects the K branch fibers 14 and the K first branch fibers 13, M × X−K of the M × X first branch fibers 13 are in an open state. As an initial construction, the switching device 17 connects the branch fiber 14 and the first branch fiber 13 such that one or more first branch fibers 13 in the open state are present in each first splitter 12. At this time, the switching device 17 includes the first branch fiber 14 and the first branch fiber 14 so that the first branch fiber 13 in the open state is connected to each first splitter 12 approximately in the same number without being biased toward the specific first splitter 12. The fiber 13 is connected.

  The branch fiber 14 connected to the arbitrary first branch fiber 13 can be switched to another first branch fiber 13 by designing so as to satisfy the above configuration and conditions. In other words, when any OLT 11 fails, the fiber between the OLT 11 and the first splitter 12 is disconnected, or the first branch fiber 13 is disconnected, the switching device 17 replaces the branch fiber 14 that has been disconnected with the other first branch fiber. 13 can be switched. When there are a plurality of branch fibers 14 that are disconnected, the switching device 17 switches each to a separate first branch fiber 13. For example, when the OLT 11-2 fails, the branch fibers (14-2, 14-3) are disconnected. The switching device 17 connects the branch fiber 14-2 to the first branch fiber 13 in the open state connected to the first splitter 12-1, and opens the branch fiber 14-3 to the first splitter 12-M. The first branch fiber 13 in the state is connected. Thereby, the branch line fiber 14-2 communicates with the OLT 11-1, and the branch line fiber 14-3 communicates with the OLT 11-M.

  For this reason, ONUs under the fault OLT can be added to the subordinates of a plurality of different OLTs in units of Y units and can be taken over. In this way, by distributing and taking over ONUs under the fault OLT by a plurality of OLTs, the number of ONUs that can be accommodated in a normal state per OLT can be increased as compared with the optical communication system of FIG.

  FIG. 5 is a diagram illustrating a case where the same conditions as the PON protection of the optical communication system in FIG. 3 are used as an example of the present embodiment. The optical communication apparatus 302 in FIG. 5 includes four OLTs 11 (M = 4) capable of accommodating a maximum of 64 ONUs 16, a first splitter 12 having a branching ratio of 1: 4 (X = 4), and a branching ratio of 1:16 ( Y = 16) second splitter 15 is provided. As shown in FIG. 5, the optical communication apparatus 302 can accommodate 48 ONUs per unit when the OLT 11 is normal, which can be larger than 32 in the optical communication system of FIG.

  In the optical communication system 302, the switching device 17 has three branch fibers 14 connected to each first splitter 12. Each first splitter 12 has one open first branch fiber 13. In addition, 16 ONUs 16 are connected to each second splitter 15. For example, when the OLT 11-1 breaks down, the three branch fibers (14-1, 14-2, 14-3) that cause communication interruption are respectively connected to the OLT (11-2, 11-3, 11-4). Switch. As a result, the three normal OLTs (11-2, 11-3, 11-4) each take over 16 ONUs 16 and communicate with a total of 64 ONUs 16 respectively.

  Switching of the switching device 17 is performed by a controller 19 that grasps the state of the OLT 11. The controller 19 is connected to the OLT 11 and acquires registration information and failure information of each ONU 16 from all the OLTs 11. Furthermore, the controller 19 is also connected to the switching device 17. The controller 19 includes a control mechanism that controls connection and disconnection between the branch fiber 14 and the first branch fiber 13 with respect to the switching device 17. Normally, the controller 19 is not connected to the branch fiber 14 with respect to the switching device 17. At least one or more open first branch fibers 13 are provided for each first splitter 12, and a connection instruction is issued to connect the branch fiber 14 and the first branch fiber 13. On the other hand, when a path that cannot be communicated between the OLT 11 and the ONU 16 is generated, the controller 19 is connected to the first splitter 12 of the path that can communicate with the branch fiber 14 of the path that cannot be communicated. A switching instruction is issued to reconnect to one of the branch fibers 13.

Specifically, the optical communication systems (301, 302) operate with the following switching algorithm.
(1) Under normal conditions, the controller 19 sends information about each ONU 16 from each OLT 11 (ID number, Round Trip Time, etc.), bandwidth utilization of each ONU 16, failure information of the OLT 11 (whether there is a decrease in OLT output, SNI (Service Node Interface)) Receive an error).
(2) When an OLT failure occurs, the controller 19 recognizes the failure by receiving information indicating that there is a failure from the OLT 11.
(3) The controller 19 uses the bandwidth utilization information of each ONU 16 from an arbitrary time point to the time of failure information reception to select the branch fiber 14 with the highest load among the branch fibers 14 that are disconnected. Switch to the first splitter 12 connected to the OLT 11. Specifically, the branch fiber 14 is switched to the open first branch fiber 13 connected to the first splitter 12. Subsequently, the controller 19 switches the branch fiber 14 having the second highest load to the first splitter 12 connected to the OLT 11 having the second lowest load. As described above, the controller 19 determines which first splitter 12 to switch the branch fiber 14 of which communication is disconnected based on the band use information of the ONU 16. Note that if the bandwidth of the switching destination OLT 11 is completely used, the controller 19 may perform the following control. Prior to switching, the controller 19 controls the OLT 11 and the ONU 16 so as to create a vacant space that can be switched to the bandwidth of the switching destination OLT 11. Next, the controller 19 instructs switching, performs dynamic bandwidth control on the originally connected ONU 16 and the newly connected ONU 16, and performs bandwidth allocation again.
(4) The controller 19 instructs the switching device 17 to switch the branch fiber 14 based on the determination.
(5) The switching device 17 switches the connection between the branch line fiber 14 and the first branch fiber 13 in accordance with an instruction from the controller 19.

  Here, the reconnection of the ONU 16 when the OLT 11 is switched will be described in detail. The controller 19 acquires the authentication information of the ONU 16 from each OLT 11 and, when a failure of a certain OLT 11 is found, transmits the authentication information of the ONU 16 connected to the OLT 11 to the switching destination OLT 11.

  After the switching destination OLT 11 receives the authentication information, the controller 19 issues a switching instruction to the switching device 17, switches the branch fiber 14, and establishes a new path. Thereafter, ONU information (for example, ID number and RTT (Round Trip Time)) is exchanged between the switching destination OLT 11 and the newly connected ONU 16 to establish a connection.

  At this time, if it is set so that the RTT does not change at all before and after switching, if the controller 19 acquires ONU information from the switching source OLT 11 and transmits it to the switching destination OLT 11, the switching destination OLT 11 is the same as the succeeding ONU. Ranging (RTT measurement) is not necessary, and communication can be performed immediately after switching, and high-speed switching can be realized.

  The optical communication systems (301, 302) do not require a backup OLT that does not perform data transmission at the normal time and can use the surplus bandwidth for the allocation at the normal time by the configuration and the switching algorithm as described above. Furthermore, the optical communication systems (301, 302) can be designed so that the number of ONUs accommodated per OLT in a normal state approaches the maximum number of accommodable units. Therefore, the optical communication system (301, 302) can suppress the OLT cost per user more than the PON protection of FIG.

(Embodiment 2)
FIG. 6 is a block diagram illustrating the optical communication system 303 of the present embodiment. The optical communication system 303 has M (M is an integer of 2 or more) OLTs 11 and a branching ratio of 1: X (X is an integer of 2 or more). For each OLT 11, the merging side is connected to one of the OLTs 11. M first splitters 12 connected on the branch side to X first branch fibers 13, K (K is an integer of 2 or more and (M−1) × X or less) branch fibers 14, and branch fibers 14 L (L is an integer not less than 1 and not more than K) of L spare fibers 24 arranged in parallel, the branching ratio is 1: Y (Y is an integer not less than 2), and each branch fiber 14 In addition, the KL second splitters 15 whose junction side is connected to one of the branch fibers 14 and whose branch side is connected to the Y second branch fibers 18, and the branching ratio is 2: Y (Y is an integer of 2 or more) ), And for each branch fiber 14, the merging side is one branch fiber 14. And any one of the L third splitters 25 connected to the auxiliary fibers 24 in parallel to the branch fibers and connected to the Y second branch fibers 18 on the branch side, and the K × Y second branch fibers 18. The Z ONUs 16 to be connected (Z is a natural number equal to or less than K × Y) and the branch fiber 14 connected at 1: 1, or when the branch fiber 14 and the backup fiber 24 are arranged in parallel, And a switching device 17 that can arbitrarily recombine the pair with the one-branch fiber 13.

  The difference between the communication system 303 and the communication system 301 of FIG. 4 is that a part or all of the second splitter 15 having a branch ratio of 1: Y is the third splitter 25 having a branch ratio of 2: Y. The spare fiber 24 is arranged in parallel with the branch line fiber 14 in the system in which 25 is introduced. In FIG. 6, the system of the second splitter and the system of the third splitter are described together, but the present invention is not limited to such connection, and the system of the second splitter and the system of the third splitter are optional with the switching device 17. It can be connected at the position. Also, the number L of the third splitter system is arbitrary in the range of 1 to K.

  The controller 19 of the communication system 303 normally performs the operation described with reference to the controller 19 in FIG. On the other hand, the controller 19 of the communication system 303, when a path that cannot be communicated between the OLT 11 and the ONU 16 occurs, and there is a cause of communication failure between the OLT 11 and the switching device 17, the branch line of the path that cannot be communicated A switching instruction is issued to reconnect the fiber 14 to one of the open first branch fibers 13 connected to the first splitter 12 on the communicable path, and the fiber 14 communicates with the branch fiber 14 in parallel with the backup fiber 24. If there is a cause for the failure, a switching instruction is issued so that the branch fiber 14 is reconnected to the backup fiber 24.

  The communication system 303 operates as described in the communication system 301 of FIG. 4 and can obtain the same effect. Further, the communication system 303 can maintain communication between the OLT 11 and the ONU 16 by the switching device 17 switching the branch fiber 14 to the backup fiber 24 even when the branch fiber 14 is disconnected.

(Embodiment 3)
FIG. 7 is a block diagram illustrating the optical communication system 304 of the present embodiment. A difference between the communication system 304 and the communication system 301 in FIG. 4 is that a controller 29 is provided as an alternative to the controller 19. The controller 29 is obtained by adding a load distribution function to the controller 19.

  Specifically, the controller 29 sets the highest one of the branch fibers 14 on the basis of the bandwidth utilization rate of the ONU acquired at an arbitrary period or an arbitrary moment with respect to the switching device 17 regardless of the failure of the OLT 11 or the like. A switching instruction is issued so that the load is connected to the open first branch fiber 13 connected to the OLT 11 having the lowest load.

  The controller 29 constantly monitors the bandwidth of each OLT 11 and each branch fiber 14 and moves the high-band branch fiber 14 to the first splitter 12 under the low load OLT 11 at any time, not only when the OLT 11 fails or when the branch fiber 14 is disconnected. Switch. The optical communication system 304 can realize load distribution among the OLTs 11 by the controller 29, and can always average the load between the OLTs 11. As a result, the optical communication system 304 can be combined with dynamic bandwidth allocation (DBA) that secures allocated bandwidth fairness between the ONUs 16 accommodated in the same OLT 11, and between users accommodated in different OLTs 11. Can also be achieved.

(Embodiment 4)
FIG. 8 is a block diagram illustrating the optical communication system 305 of the present embodiment. The optical communication system 305 has an MLT (M is an integer of 2 or more) OLTs 11 capable of accommodating a maximum of AUs (A is an integer of 2 or more) and a branching ratio of 1: M. The M first splitters 12 whose side is connected to one of the OLTs 11 and the branching ratio are 1: M−1, and for each first splitter 12, the merging side is connected to one port on the branching side of the first splitter 12. M optical switches 31; (M−1) × M or less second splitters 15 having a branching ratio of 2: Y ′ (Y ′ is an integer satisfying 2 or more and A / M or less); The number of branches of the two splitter 15 is connected to each port on the Y ′ side (M−1) × Y ′ × M or less ONUs 16, other ports on the branch side of the first splitter 12, and the second splitter 15 K for connecting 1: 1 port with 1 branch on the side with 2 branches (K is 2 or more and For each of the first splitter 12 connected by one (M−1) × M or less) branch fiber 14 and the branch fiber 14, the second splitter 15 and the optical switch 31 form a group. The number of branches of the second switch 15 and the number of branches of the optical switch 31 is M− so that the second splitter 15 belonging to the other group is coupled to the optical switch 31 belonging to another different group. K spare branch fibers 34 that connect the ports on the one side 1: 1.

  The optical communication system 305 acquires registration information and failure information of each ONU 16 from all the OLTs 11, and when a path that cannot be communicated between the OLT 11 and the ONU 16 occurs, the branch line used by the path The controller 19 further issues a switching instruction to the optical switch 31 to which the auxiliary branch fiber 15 is connected so that the auxiliary branch fiber 34 connected to the second splitter 15 to which the fiber 14 is connected becomes a new path.

  The optical communication system 305 is a case where M = 4. The optical communication system 305 includes four OLTs 11 capable of accommodating a maximum of 64 ONUs 16 per unit, and the OLTs 11 are connected to the merging side of the first splitter 12 having a branching ratio of 1: 4. Four optical fibers are connected to the branch side of the first splitter 12, and three of them are branch fibers 14. The branch fiber 14 is connected to the side where the number of branches of the second splitter 15 having three branching ratios 2:16 is two. The remaining one is connected to the merging side of the optical switch 31 having a branching ratio of 1: 3. The controller 19 that controls path switching at the time of failure is connected to the OLT 11 and the optical switch 31. Sixteen ONUs 16 are connected to the branching number 16 side of each second splitter 15, and one branch fiber 14 and one auxiliary branching fiber 34 are connected to the branching number 2 side. Each of the auxiliary branch fibers 34 is connected to the branch side of the optical switch 31.

  Here, it is assumed that the backup branch fiber 34 from the second splitter 15 under the arbitrary OLT 11 is connected to the optical switches 31 under the OLT 11 different from each other other than the OLT 11. In FIG. 8, for example, the backup branch fiber 34 from the second splitter (15-1, 15-2, 15-3) under the OLT 11-1 is light under the OLT (11-2, 11-3, 11-4). Connected to the switches (31-2, 31-3, 31-4), respectively. Note that, under the OLT 11-1, the first splitter 12-1, the optical switch 31-1, the second splitter (15-1, 15-2, 15-3), and the second splitter (15-1, 15-2). 15-3) is included. These may be referred to as a group of first splitters 12-1. The same applies to the other OLTs 11.

  When normal, the optical switch 31 does not pass the upstream / downstream optical signal of the standby branch fiber 34. Then, the controller 19 acquires in advance connection information between the ONU 16 and the optical switch 31 via the backup branch fiber 34. As a result, the controller 19 can instruct the appropriate optical switch 31 to open an appropriate path, and can switch the branch fiber 14 that is disconnected when a failure such as an OLT failure occurs to the standby branch fiber 34. In accordance with an instruction from the controller 19, the optical switch 31 opens only the corresponding path and passes the upstream / downstream optical signal.

  The OLT 11 of the optical communication system 305 communicates with 48 ONUs 16 when normal. FIG. 9 is a diagram for explaining path switching when the OLT 11-4 fails. As shown in FIG. 9, when the OLT 11-4 fails, the optical switches (31-1, 31-2, 31-3) follow the instructions of the controller 19 to route the three branch fibers 14 under the OLT 11-4, respectively. Switch to the fiber 34 path. As a result, three normal OLTs (11-1, 11-2, 11-3) take over 16 ONUs 16 subordinate to the OLT 11-4. That is, the OLT (11-1, 11-2, 11-3) communicates with a total of 64 ONUs 16 including 16 units inherited by 48 units under each of them.

  FIG. 10 is a diagram illustrating path switching when the branch line fiber 14 that connects the first splitter 12-1 and the second splitter 15-1 is disconnected. In this case, the optical switch 31-2 switches only the path of the single branch fiber 14 that has been disconnected by an instruction from the controller 19 to the path of the standby branch fiber 34. As a result, the normal OLT 11-2 having the optical switch 31-2 connected to the corresponding auxiliary branch fiber 34 takes over 16 ONUs 16 under the broken branch fiber 14. In other words, the OLT 11-2 communicates with a total of 64 ONUs 16 including the succeeding 48 units and the 16 units inherited. The OLT 11-1 having the disconnected branch fiber 14 under control communicates with 32 ONUs 16 except 16 units under the disconnected branch fiber 14. Each of the OLTs (11-3, 11-4) communicates with 48 ONUs 16 continuously.

  As described above, the optical communication system 305 can take over all 48 ONUs under the failed OLT, with the other 3 OLTs sharing 16 units each at the time of any OLT failure. Therefore, considering the case where the OLT has failed in the N: M protection system of FIG. 3, the number of ONUs accommodated by one OLT during normal operation is reduced (32 units). The system 305 can increase the number of normal ONUs (48 units).

The number of OLTs is M, the branching ratio of the M first splitters 12 is 1: X, the branching ratio of the maximum (M−1) × M second splitters 15 is 2: Y, and the branching ratio of the M optical switches Is 1: Z, and the maximum number of ONUs per OLT is A. If the optical communication system is designed to satisfy the following conditional expression 1, in addition to the configuration of FIG. 8 (M = 4), normal The number of ONUs that can be accommodated can be increased.
(Condition 1)
M ≧ 2,
Z = M−1,
X = M,
Y × M ≦ A

  For example, if an optical communication system is designed with M = 8, Z = 7, X = 8, A = 64, and Y = 8, each OLT can accommodate 56 ONUs at normal time, which is more than the optical communication system 305 in FIG. It is possible to increase the number of ONUs that can be accommodated when each OLT is normal.

  The optical switch 31 is switched by the controller 19 that grasps the state of the OLT 11. The controller 19 is connected to the OLT 11 and acquires registration information and failure information of each ONU 16 from all the OLTs 11. Further, the controller 19 is also connected to the optical switch 31. The controller 19 includes a control mechanism that controls connection and disconnection between the first splitter 12 and the auxiliary branch fiber 34 with respect to the optical switch 31, and all the auxiliary branch fibers 34 are normally connected to the optical switch 31. And the first splitter 12 are shut off. On the other hand, when a path that cannot be communicated between the OLT 11 and the ONU 16 (for example, between the first splitter 12-1 and the second splitter 15-1) occurs, the branch fiber 14 used by the path is connected. A switching instruction is issued to the optical switch 31-2 connected to the auxiliary branch fiber 34 so that the auxiliary branch fiber 34 connected to the second splitter 15-1 is used as a new path.

Specifically, the optical communication system 305 operates by the following switching algorithm.
(1) When normal, the controller 19 periodically sends information on each ONU 16 (authentication information, ID number, round trip time (RTT), etc.), OLT failure information (whether there is a decrease in OLT output, whether there is an SNI abnormality, etc.) from each OLT 11. Receive at random or irregular intervals.
(2) At the time of OLT failure or branch fiber disconnection, the controller 19 receives the notification of the failure occurrence from the OLT 11 and recognizes the branch fiber 14 that is disconnected.
(3) Based on the correspondence information of the ONU 16 and the optical switch 31 set in advance, the controller 19 is connected to the optical switch 31 (the switching destination optical switch and the switch branch optical fiber 14 to which the branch fiber 14 of the branch fiber 14 to be disconnected is disconnected. Recognize).
(4) The controller 19 transmits the information (authentication information, ID number, RTT, etc.) of the ONU 16 under the branch fiber 14 that is disconnected from communication to the OLT 11 (referred to as the switching destination OLT) having the switching destination optical switch. .
(5) In order to switch the branch fiber 14 to be disconnected to the backup branch fiber 34, the controller 19 instructs the switching destination optical switch to open only the path of the corresponding backup branch fiber 34.

  The optical switch 31 that has received an instruction from the controller 19 by the above algorithm switches the path from the current branch fiber 14 to the standby branch fiber 34. After switching, RTT is measured between the switching destination OLT 11 and the succeeded ONU 16, and data transmission is started.

  However, if the RTT is designed in advance so as not to change at all before and after switching, the ONU information (authentication information, ID number, RTT, etc.) obtained by the switching destination OLT 11 in the algorithm (4) can be used as it is. The subsequent measurement of RTT between the switching destination OLT 11 and the succeeding ONU 16 becomes unnecessary.

(Embodiment 5)
FIG. 11 is a block diagram illustrating the optical communication system 306 of the present embodiment. The optical communication system 306 further includes a branch optical shutter disposed on the branch fiber 14 of the optical communication system 305 of FIG. 8 and blocking an optical signal propagating through the branch fiber 14. In the case of the optical communication system 306, a branch line optical shutter is not separately provided in addition to the optical switch 31, but a hybrid device 31 ′ combining an optical switch function and an optical shutter function is used instead of the optical switch 31.

  As in the optical communication system 305 in FIG. 8, the optical switch function part of the hybrid device 31 ′ is connected with the auxiliary branch fiber 34 from the second splitter 15 under the other OLT, and the optical shutter function part of the hybrid device 31 ′. A branch fiber 14 is connected to the. Under the instruction of the controller 19, the optical shutter function part keeps the shutters of the respective paths open under normal conditions, and the OLT 11-ONU 16 communicates via the branch fiber 14, while the optical switch function part receives the up / down signal. Do not pass through.

  FIG. 12 is a diagram for explaining path switching when the OLT 11-4 fails. When a failure such as an OLT failure or a branch fiber disconnection occurs, the corresponding path of the shutter function part connecting the branch line to be disconnected is closed, and the switch function part connecting the spare branch fiber 34 is the up / Pass downstream signals together.

  There is an advantage that the troubled part can be easily repaired by closing the corresponding route of the shutter function part at the time of communication trouble. In other words, when the corresponding path of the shutter function portion remains open or when the branch line is directly connected to the first splitter as shown in FIG. 8, for example, after the arbitrary branch line is disconnected and switched to the spare branch fiber 34. When the OLT 11-ONU 16 repairs the branch fiber 14 disconnected during communication via the backup branch fiber 34, the downstream signals from the upper OLT 11 of the standby branch fiber 34 in communication and the upper OLT 11 of the repaired branch fiber 14 are transmitted. There is a risk of collision at the second splitter 15. However, if the shutter function part closes the corresponding path, even if it is repaired, the downstream signals from two different OLTs 11 do not reach the same second splitter 15 unless the path is opened. Can work.

(Embodiment 6)
FIG. 13 is a block diagram illustrating the optical communication system 307 of the present embodiment. The difference between the optical communication system 307 and the optical communication system 305 in FIG. 8 is that the optical communication system 307 includes a backup optical shutter 32 as an alternative to the optical switch 31. In the case of the optical switch 31, the first splitter 12 can make substantially one branch as a receiving port for the auxiliary branch fiber 34 regardless of the number of branch fibers 14 per OLT, whereas in the case of the auxiliary optical shutter 21, It is necessary to use the same number of branches as the number of branch fibers 14 per OLT as a receiving port for the backup branch fibers 34. Therefore, the branching ratio of the first splitter 12 is 1: 4 for the optical communication system 305, whereas the optical communication system 307 is 1: 6.

  The optical communication system 307 will be described in detail. The optical communication system 307 has M (M is an integer greater than or equal to 2) OLTs 11 capable of accommodating a maximum of A (A is an integer greater than or equal to 2) ONUs 16 and a branching ratio of 1: (M−1) × 2. For each OLT 11, the M first splitters 12 whose merging side is connected to one of the OLTs 11 and the branching ratio are 2: Y ′ (Y ′ is an integer satisfying 2 or more and A / M or less) (M− 1) No more than xM second splitters 15; (M-1) xY 'x no more than ONUs 16 connected to each port on the Y' side, and the first splitter 15; K (K is 2 or more and (M−)), which connects M−1 ports as one set on the 12 branch side and 1 port on the side where the number of branches of the second splitter 15 is 2 on a 1: 1 basis. 1) Integer less than or equal to M) First branch fiber 14 and the first splitter connected by the branch fiber 14 Every 12, the first splitter 12 and the second splitter 15 form a group, and the second splitter 15 belonging to one group is coupled to the first splitter 12 belonging to another different group. K spare branch fibers 34 for connecting the other ports of the two splitters 15 on the side where the number of branches is 2 and the M-1 ports which are the other set on the branch side of the first splitter 12 in a 1: 1 ratio; A preliminary optical shutter 32 disposed on the auxiliary branch fiber 34 and blocking an optical signal propagating through the auxiliary branch fiber 34.

  The optical communication system 307 acquires the registration information and failure information of each ONU 16 from all the OLTs 11, and normally blocks the path of the backup branch fiber 34 by the backup optical shutter 32, so that the OLT 11 and the ONU 16 When a path incapable of communication occurs between the first and second splitter fibers 34, the spare branch fiber 34 connected to the second splitter 15 to which the branch fiber 34 used by the path is connected becomes a new path. It further includes a controller 19 that issues an opening instruction to the auxiliary light shutter 32 to be connected.

  The optical communication system 307 is a case where M = 4. The optical communication system 307 includes four OLTs 11 that can accommodate up to 64 ONUs 16 per unit, and the OLTs 11 are connected to the merging side of the first splitter 12 having a branching ratio of 1: 6. Six optical fibers are connected to the branch side of the first splitter 12, and three of the optical fibers are auxiliary branch fibers 34 in which auxiliary optical shutters 32 that open and close three paths are arranged. The other three optical fibers are branch fibers 14 connected to the branch number 2 side of the second splitter 15 having three branch ratios of 2:16. Further, one auxiliary branch fiber 34 is connected to each of the two second splitters on the branching number 2 side, and the three auxiliary branch fibers 34 in total are connected to separate auxiliary optical shutters 32 one by one.

  Here, it is assumed that the auxiliary branch fiber 34 from the second splitter 15 under the arbitrary OLT 11 is connected to the auxiliary optical shutter 32 under the OLT 11 different from the OLT 11. In FIG. 13, for example, spare branch fibers 34 from the second splitters (15-1, 15-2, 15-3) under the OLT 11-1 are spares under the OLT (11-2, 11-3, 11-4). Each is connected to an optical shutter (32-2, 32-3, 32-4). Note that the OLT 11-1 has a first splitter 12-1, a spare optical shutter 32-1, a second splitter (15-1, 15-2, 15-3), and a second splitter (15-1, 15-). 2, 15-3) is included. These may be referred to as a group of first splitters 12-1. The same applies to the other OLTs 11.

  The standby optical switch 32 does not pass the upstream / downstream optical signal of the standby branch fiber 34 at the normal time. Then, the controller 19 acquires in advance connection information between the ONU 16 and the auxiliary light shutter 32 via the auxiliary branch fiber 34. As a result, the controller 19 can instruct the appropriate auxiliary light shutter 32 to open an appropriate path, and can switch the path of the branch fiber 14 that is disconnected when a failure such as an OLT failure occurs to the standby branch fiber 34. . In accordance with an instruction from the controller 19, the spare light shutter 32 opens only the corresponding path and passes the upstream / downstream optical signal.

  The OLT 11 of the optical communication system 307 communicates with 48 ONUs 16 when normal. FIG. 14 is a diagram for explaining path switching when the OLT 11-4 fails. As shown in FIG. 14, when the OLT 11-4 fails, the spare light shutters (32-1, 32-2, 32-3) follow the instructions of the controller 19 and the second splitters (15-10, 15-11, 15-12). ) From the auxiliary branch fiber 34 is opened. Thereby, the path | route of the three branch fiber 14 under OLT11-4 can be switched to the path | route of the backup branch fiber 34, respectively. As a result, three normal OLTs (11-1, 11-2, 11-3) take over 16 ONUs 16 subordinate to the OLT 11-4. That is, the OLT (11-1, 11-2, 11-3) communicates with a total of 64 ONUs 16 including 16 units inherited by 48 units under each of them.

  FIG. 15 is a diagram for explaining path switching when the branch fiber 14 connecting the first splitter 12-1 and the second splitter 15-1 is disconnected. In this case, the auxiliary light shutter 32-2 opens a path on the auxiliary branch fiber 34 connected to the second splitter 15-1 in accordance with an instruction from the controller 19. Thereby, it is possible to switch only the route of one disconnected branch fiber 14 to the route of the backup branch fiber 34. As a result, the normal OLT 11-2 having the auxiliary optical shutter 32-2 connected to the corresponding auxiliary branch fiber 34 takes over 16 ONUs 16 under the broken branch fiber 14. In other words, the OLT 11-2 communicates with a total of 64 ONUs 16 including the succeeding 48 units and the 16 units inherited. The OLT 11-1 having the disconnected branch fiber 14 under control communicates with 32 ONUs 16 except 16 units under the disconnected branch fiber 14. Each of the OLTs (11-3, 11-4) communicates with 48 ONUs 16 continuously.

  As described above, the optical communication system 307 can take over all the 48 ONUs under the failed OLT, with the other 3 OLTs sharing each 16 units, at the time of any OLT failure. Therefore, considering the case where the OLT has failed in the N: M protection system of FIG. 3, the number of ONUs accommodated by one OLT during normal operation is reduced (32 units). The system 307 can increase the number of normal ONUs (48 units).

(Embodiment 7)
FIG. 16 is a block diagram illustrating the optical communication system 308 of the present embodiment. The optical communication system 308 further includes a branch optical shutter that is disposed on the branch fiber 14 of the optical communication system 307 in FIG. 13 and blocks an optical signal propagating through the branch fiber 14. In the case of the optical communication system 308, a branch line light shutter is not separately provided in addition to the spare light shutter 32, but an optical shutter 32 ′ in which the spare light shutter 32 and the branch line light shutter are combined in place of the spare light shutter 32 is provided. Used.

  Similarly to the optical communication system 307 in FIG. 13, the auxiliary optical fiber portion from the second splitter 15 under the other OLT is connected to the auxiliary optical shutter portion of the optical shutter 32 ′, and the auxiliary optical shutter portion of the optical shutter 32 ′. A branch fiber 14 is connected to the. Under the direction of the controller 19, under normal conditions, the branch line optical shutter part keeps the respective paths open, and the OLT 11-ONU 16 communicates via the branch line fiber 14, while the spare optical shutter part transmits both upstream and downstream signals. Do not pass.

  FIG. 17 is a diagram for explaining path switching when the OLT 11-4 fails. When a failure such as an OLT failure or a branch fiber disconnection occurs, the branch optical shutter portion connecting the branch line that causes communication disconnection closes each path, and the spare optical shutter portion connecting the spare branch fiber 34 is in the corresponding path. Pass upstream / downstream signals together. Specifically, as in the description of the optical communication system 307 in FIG. -10, 15-11, 15-12) to the path on the backup branch fiber 34. At the same time, in accordance with an instruction from the controller 19, the optical shutter 32'-4 blocks the path of the branch fiber 14 from the second splitter (15-10, 15-11, 15-12).

  By closing the corresponding path of the branch line optical shutter portion of the optical shutter 32 ′ at the time of communication failure, there is an advantage that the troubled part can be easily repaired as described in the optical communication system 307 of FIG. 14. In other words, the optical communication system 308 not only can increase the number of ONUs that can be accommodated in each OLT in a normal state, but also can easily repair a failure in the event of a failure.

The number of OLTs is M, the branching ratio of M first splitters 12 is 1: X, the maximum (M−1) × the branching ratio of M second splitters 15 is 2: Y, and the maximum number of ONUs accommodated per OLT If A is designed so that the following conditional expression 2 is satisfied, in addition to the configuration of FIG. 16 (M = 4), the number of ONUs that can be accommodated in a normal state can be increased.
(Condition 2)
M ≧ 2,
X = (M−1) × 2,
Y × M ≦ A

  For example, when designing with M = 3, X = 4, A = 64, and Y = 21, the configuration is as shown in FIG. Or if M = 8, X = 14, A = 64, and Y = 8, each OLT can accommodate 56 ONUs at normal time, and each OLT can be accommodated at normal time than the configurations of FIGS. The number of ONUs can be increased.

  The optical shutter (32, 32 ') is switched by the controller 19 that grasps the state of the OLT 11. The controller 19 is connected to the OLT 11 and acquires registration information and failure information of each ONU 16 from all the OLTs 11. Furthermore, the controller 19 is also connected to the optical shutter (32, 32 '). The controller 19 includes a control mechanism for controlling the opening and closing of the branch fiber 14 and the standby branch fiber 34 with respect to the optical shutter (32, 32 ′). Normally, the controller 19 controls the optical shutter (32, 32 ′). Thus, all the auxiliary branch fibers 34 are blocked. On the other hand, when a path that cannot be communicated between the OLT 11 and the ONU 16 (for example, between the first splitter 12-1 and the second splitter 15-1) occurs, the branch fiber 14 used by the path is connected. Instruction to open the spare optical shutter portion connected to the auxiliary branch fiber 34 to the optical shutter (32-2, 32'-2) so that the auxiliary branch fiber 34 connected to the second splitter 15-1 is a new path. Put out.

Specifically, the optical communication system 308 operates with the following switching algorithm.
(1) When normal, the controller 19 periodically sends information on each ONU 16 (authentication information, ID number, round trip time (RTT), etc.), OLT failure information (whether there is a decrease in OLT output, whether there is an SNI abnormality, etc.) from each OLT 11. Receive at random or irregular intervals.
(2) At the time of OLT failure or branch fiber disconnection, the controller 19 receives the notification of the failure occurrence from the OLT 11 and recognizes the branch fiber 14 that is disconnected.
(3) The controller 19 recognizes the optical shutter 32 ′ to which the auxiliary branch fiber 34 of the branch fiber 14 to be disconnected is connected based on the preset correspondence information between the ONU 16 and the optical shutter 32 ′.
(4) The controller 19 transmits the information (authentication information, ID number, RTT, etc.) of the ONU 16 under the branch fiber 14 that is disconnected from communication to the OLT 11 (referred to as a switching destination OLT) having a switching destination optical shutter. .
(5) In order to switch the branch fiber 14 to be disconnected to the backup branch fiber 34, the controller 19 instructs the switching destination optical shutter to open only the path of the corresponding backup branch fiber 34.

  The optical shutter 32 ′ that receives an instruction from the controller 19 by the above algorithm switches the path from the current branch fiber 14 to the standby branch fiber 34. After switching, RTT is measured between the switching destination OLT 11 and the succeeded ONU 16, and data transmission is started.

  However, if the RTT is designed in advance so as not to change at all before and after switching, the ONU information (authentication information, ID number, RTT, etc.) obtained by the switching destination OLT 11 in the algorithm (4) can be used as it is. The subsequent measurement of RTT between the switching destination OLT 11 and the succeeding ONU 16 becomes unnecessary.

  Although the optical communication system 308 uses a plurality of optical shutters 32 ', the optical communication system 309 using one optical shutter 33 operates similarly as shown in FIG.

(Embodiment 8)
FIG. 20 is a block diagram illustrating the optical communication system 310 of the present embodiment. The optical communication system 310 has an MLT (M is an integer greater than or equal to 2) OLTs 11 that can accommodate a maximum of A (A is an integer greater than or equal to 2) ONUs 16 and a branching ratio of 1: (M−1) × M. For each OLT 11, the M first splitters 12 whose merging side is connected to one of the OLTs 11, and the branching ratio is M: Y ′ (Y ′ is an integer that satisfies 2 or more and satisfies A / M) (M−1) ) × M or less second splitters 15, (M−1) × Y ′ × M or less ONUs 16 connected to each port on the side where the number of branches of the second splitter 15 is Y ′, and the first splitter 12. M-1 ports which are one set on the branch side of the second splitter 15 and one port on the side where the number of branches of the second splitter 15 is M are connected 1: 1 (K is 2 or more and (M-1 ) × Integer less than or equal to M) For each first splitter 12 connected by 14 branch fibers 14 and branch fibers 14 The first splitter 12 and the second splitter 15 form a group, and the second splitter 15 belonging to one group belongs to another group in which the other ports on the M side have different numbers of branches. So that the number of branches of the second splitter 15 is M and the other pair of the other side of the branch of the first splitter 12 is (M−1) ^two ports 1: 1. K × (M−1) spare branch fibers 34 to be connected, a spare optical shutter disposed on the spare branch fiber 34 and blocking an optical signal propagating through the spare branch fiber 34, and disposed on the branch fiber 14. A branch line optical shutter that blocks an optical signal propagating through the branch line fiber 14. The optical communication system 310 of FIG. 20 uses an optical shutter 32 ′ that combines a standby optical shutter and a branch optical shutter.

  The optical communication system 310 obtains the bandwidth usage rate of each ONU 16 from any OLT 11 at any time period or at any moment, so that the bandwidth usage rates of the optical shutters 32 ′ are substantially equal. A controller 49 is further provided that issues a reconnection instruction to the optical shutter 32 'to reconnect the second splitter 15 and the first splitter 15 by opening the branch line optical shutter portion.

  An optical communication system 310 in FIG. 20 has a configuration that enables load distribution in the optical communication system in FIG. The main difference between the optical communication system 310 and the optical communication system of FIG. 19 is that the optical communication system 310 allows free connection between the ONU 16 and the OLT 11. For this reason, the optical communication system 310 changes the branching ratio of the second splitter 15 from 2:21 to 3:21 of the optical communication system of FIG. 19, and sets the number of spare branch fibers from the second splitter 15 to the optical communication of FIG. The number of paths through which the optical shutter 32 'opens and closes from one to two in the system is 4 to 6 in the optical communication system in FIG. 19, and the branching ratio of the first splitter 12 is 1: 4 in the optical communication system in FIG. To 1: 6. The optical communication system 310 includes a controller 49 to which a load distribution function is added.

  FIG. 21 shows an example of route switching for load distribution. For example, when the OLT 11-1 is a high load, the OLT 11-2 is a low load, and the OLT 11-3 is a medium load, the route of the branch fiber 14 under the OLT 11-1 that performs medium band data transmission is changed to the low load OLT 11 -2 to the path of the backup branch fiber 34 connected to -2. As a result, the load on the OLT 11-1 that was a high load is reduced, while the load on the OLT 11-2 that is a low load is increased, and the load on each OLT is moderately averaged. As described above, the optical communication system 310 can perform OLT load distribution.

(Embodiment 9)
FIG. 22 is a block diagram illustrating the optical communication system 311 of the present embodiment. The optical communication system 311 has M (M is an integer greater than or equal to 2) OLTs 11 that can accommodate up to A (A is an integer greater than or equal to 2) ONUs 16 and a branching ratio of 1: B (B is an integer greater than or equal to M). For each OLT 11, the merge side is connected to one of the OLTs 11 with M first splitters 12, and to each of the first splitters 12, B coupled to the B ports on the branch side of the first splitter 12. M branch-line optical shutters 32 ″ for opening and closing the respective optical paths, and B having a branching ratio of M: Y ″ (Y ″ is an integer satisfying 2 or more and A / {B− (M−1)} or less). Second splitter 15, the ONU 16 of B × Y ″ or less connected to each port on the Y ″ side of the number of branches of the second splitter 15, B optical paths of the branch optical shutter 32 ″ and the second splitter Connect 15 ports with M branch to 1: 1. × comprises an M number of branch fibers 14.

  The optical communication system 311 acquires the bandwidth usage rate of each ONU 16 from any OLT 11 at any time period or at any moment, so that the bandwidth usage rates are substantially equal so that the bandwidth usage rates are substantially equal. A controller 49 is further provided that issues a reconnection instruction to the optical shutter 32 "to reconnect the second splitter 15 and the first splitter 12 by opening the optical path.

  The controller 49 opens at least one path for each first splitter 12 and the number of paths opened at any time with any of the first splitters 12 formed in each second splitter 15. The optical shutter 32 ″ is controlled so that is 1 or 0.

  In the optical communication system 311, the number of OLTs 11 is M, the number of second splitters 15 having a branching ratio M: Y is B, the number of first splitters 12 having a branching ratio 1: B is M, and the B optical path is opened / closed per unit. The number of branch optical shutters 32 ″ to be performed is M, and the maximum number of ONUs 16 accommodated per OLT is A.

  M branch fibers 14 from each second splitter 15 are connected to M branch optical shutters 32 ″ one by one, and two or more paths out of the M branch fibers 14 are branch optical shutters 32. The controller 49 controls the branch light shutter 32 "so that it is not simultaneously opened through".

If the optical communication system is designed so as to satisfy the following conditional expression 3, in addition to the configuration of FIG. 22 (M = 3, B = 6), load distribution is possible.
(Condition 3)
M ≧ 2
B ≧ M
{B- (M-1)} × Y ″ ≦ A

  The optical communication system 310 of FIG. 20 can connect only a total of three branch fibers and spare branch fibers from the second splitter to an arbitrary optical shutter, so even if it is desired to connect a fourth optical fiber for load distribution. An impossible situation can occur. However, if the optical communication system 311 is designed so as to satisfy the conditional expression 3, the connection destination of the branch fiber 14 from the second splitter 15 can be freely switched to any branch light shutter 32 ″, so that load distribution is free. However, it is necessary that at least one branch line fiber 14 is connected to each branch line optical shutter 32 ″.

  For example, when designing with B = 6, M = 3, and Y = 16, the configuration is the same as that of the optical communication system 310 in FIG. 20 except for the number of ONUs 16 under each second splitter 15. However, as shown in FIG. 22, by restricting the number of ONUs 16 under the second splitter 15, it is possible for one branch line optical shutter 32 "-2 to open four paths. The system 311 can switch load distribution with a higher degree of freedom than the optical communication system 310.

11, 11-1, 11-2,..., 11-M: OLT (station side terminal device)
12, 12-1, 12-2,..., 12-M: first splitter 13: first branch fibers 14, 14-1, 14-2,..., 14-K: branch fibers 15, 15 -1, 15-2,..., 15-K: second splitter 16: ONU (subscriber-side terminating device)
17: Switching device 18: Second branch fibers 19, 29, 49: Controllers 24, 24-1, 24-2,..., 24-L: Spare fibers 25, 25-1, 25-2,. , 25-L: Third splitter (2: Y splitter)
31, 31-1, 31-2, ..., 31-M: optical switches 31 ', 31'-1, 31'-2, ..., 31'-M: hybrid devices 32, 32-1, 32-2, ..., 32-M: Preliminary light shutters 32 ', 32'-1, 32'-2, ..., 32'-M: Light shutters 32, 32 "-1, 32" -2 32 "-M: branch optical shutter 33: optical shutter 34: spare branch fibers 301 to 311: optical communication system

Claims (24)

M (M is an integer of 2 or more) station-side terminal devices;
The branching ratio is 1: X (X is an integer greater than or equal to 2), and for each of the station-side terminators, the junction side is connected to one of the station-side terminators, and the branch side is connected to X first branch fibers. M first splitters;
K (K is an integer of 2 or more and (M−1) × X or less) branch fibers;
The branching ratio is 1: Y (Y is an integer of 2 or more), and for each branch fiber, the merging side is connected to one of the branch fibers, and the branching side is connected to Y second branch fibers. Two splitters,
Z (Z is a natural number equal to or less than K × Y) subscriber-side terminators each connected to any one of the K × Y second branch fibers;
A switching device that can arbitrarily recombine the set of the branch fiber and the first branch fiber connected at 1: 1;
An optical communication system comprising: Obtaining registration information and failure information of each of the subscriber side termination devices from all the station side termination devices,
For the switching device, at least one or more of the first branch fibers in an open state that are not connected to the branch fibers are normally present for each first splitter, and the branch fibers and the first branch fibers When a path that cannot be communicated between the station-side terminal device and the subscriber-side terminal device occurs, the path that can communicate with the branch fiber of the path that cannot be communicated is generated. 2. The optical communication system according to claim 1, further comprising a controller that issues a switching instruction to reconnect to one of the open first branch fibers connected to the first splitter. M (M is an integer of 2 or more) station-side terminal devices;
The branching ratio is 1: X (X is an integer greater than or equal to 2), and for each of the station-side terminators, the junction side is connected to one of the station-side terminators, and the branch side is connected to X first branch fibers. M first splitters;
K (K is an integer of 2 or more and (M−1) × X or less) branch fibers;
L spare fibers arranged in parallel with L (L is an integer of 1 to K) of the branch fibers;
The branching ratio is 1: Y (Y is an integer equal to or greater than 2), and for each branch fiber, the merging side is connected to one of the branch fibers, and the branch side is connected to Y second branch fibers. A second splitter of
The branching ratio is 2: Y (Y is an integer greater than or equal to 2), and for each branch fiber, the merge side is connected to one of the branch fibers and the spare fiber in parallel with the branch fiber, and the branch side has Y wires L third splitters connected to the second branch fiber;
Z (Z is a natural number equal to or less than K × Y) subscriber-side terminators each connected to any one of the K × Y second branch fibers;
A switching device that can arbitrarily recombine the set of the first branch fiber and any one of the branch fiber connected in 1: 1 or the branch fiber and the backup fiber in parallel.
An optical communication system comprising: Obtaining registration information and failure information of each of the subscriber side termination devices from all the station side termination devices,
For the switching device, at least one or more of the first branch fibers in an open state that are not connected to the branch fibers are normally present for each first splitter, and the branch fibers and the first branch fibers A connection instruction is issued to connect the station-side terminal device and the subscriber-side terminal device, and a communication-disabled path occurs between the station-side terminal device and the switching device. If there is a cause of this, a switching instruction is made so that the branch fiber in the incommunicable path is reconnected to one of the open first branch fibers connected to the first splitter in the communicable path. If there is a cause of communication failure in the branch fiber in parallel with the backup fiber, the controller issues a switching instruction to reconnect the branch fiber to the backup fiber. Optical communication system of claim 3, further comprising a chromatography la. The controller is
Obtaining the bandwidth utilization rate of the subscriber-side terminal device,
For the switching device, when communication failure occurs between the station-side terminal device and the switching device, based on the bandwidth utilization rate acquired from the arbitrary time until communication failure occurs, Instructing switching to connect to the first branch fiber in the open state connected to the station-side terminator having the lowest load in order from the highest load among the branch fibers of the path where communication is impossible The optical communication system according to claim 1, wherein the optical communication system is characterized in that: The controller is
Obtaining the bandwidth utilization rate of the subscriber-side terminal device,
For the switching device, based on the band utilization rate acquired at an arbitrary period or at an arbitrary moment, the branch fiber having the highest load is connected to the station-side terminator having the lowest load. 5. The optical communication system according to claim 1, wherein a switching instruction is issued so as to connect to the first branch fiber in an open state. An optical communication method for an optical communication system according to claim 1,
Obtaining registration information and failure information of each of the subscriber side termination devices from all the station side termination devices,
In the switching device, the branch fiber and the first branch fiber are normally connected so that there is at least one or more of the first branch fiber in an open state that is not connected to the branch fiber for each first splitter. When a path that cannot be communicated between the station-side terminator and the subscriber-side terminator occurs, the branch fiber of the path that cannot be communicated is connected to the first splitter that can communicate An optical communication method comprising reconnecting to any one of the first branched fibers in an open state. An optical communication method for an optical communication system according to claim 3,
Obtaining registration information and failure information of each of the subscriber side termination devices from all the station side termination devices,
In the switching device, the branch fiber and the first branch fiber are normally connected so that there is at least one or more of the first branch fiber in an open state that is not connected to the branch fiber for each first splitter. When a path that cannot be communicated between the station-side terminator and the subscriber-side terminator occurs when there is a cause of communication inability between the station-side terminator and the switching device, Reconnect the branch fiber in the incommunicable path to one of the open first branch fibers connected to the first splitter in the communicable path, and communicate with the branch fiber in parallel with the backup fiber An optical communication method characterized by reconnecting the branch line fiber to the backup fiber when there is a cause of the impossibility. Obtain the bandwidth usage rate of the subscriber-side terminal device,
When communication failure occurs between the station-side terminal device and the switching device, the branch line of the route that cannot be communicated based on the bandwidth utilization rate acquired from any point in time until communication failure occurs 9. The optical communication according to claim 7, wherein the optical communication is connected to the first branch fiber in an open state connected to the station-side terminator having the lowest load in order from the highest load among the fibers. Method. Obtain the bandwidth usage rate of the subscriber-side terminal device,
The first branch in an open state in which the one with the highest load among the branch fibers is connected to the station-side terminator with the lowest load based on the bandwidth utilization obtained at an arbitrary period or at an arbitrary moment The optical communication method according to claim 7, wherein the optical communication method is connected to a fiber. M (M is an integer of 2 or more) station-side termination devices capable of accommodating a maximum of A (A is an integer of 2 or more) subscriber-side termination devices;
A branching ratio of 1: M, and for each of the station-side terminators, M first splitters whose merging side is connected to one of the station-side terminators;
M optical switches having a branching ratio of 1: M-1 and having a merging side connected to one port on the branching side of the first splitter for each of the first splitters;
A branching ratio of 2: Y ′ (Y ′ is an integer satisfying 2 or more and A / M or less), and (M−1) × M or less second splitters;
(M-1) × Y ′ × M or less subscriber-side terminators connected to each port on the Y′-side branch number of the second splitter;
K (K is 2 or more and (M−1) × M or less) that connects the other port on the branch side of the first splitter and the 1 port on the side where the number of branches of the second splitter is 2 on a 1: 1 basis. An integer) of the branch fiber,
For each of the first splitters connected by the branch fiber, the second splitter and the optical switch form a group, and the second splitter belonging to one of the groups belongs to another different group. In order to couple with the optical switch, K spares for connecting the other port of the second splitter having the branch number of 2 and the port of the optical switch having the branch number of the M-1 side in a 1: 1 ratio. A branch fiber,
An optical communication system comprising:   The optical communication system according to claim 11, further comprising a branch optical shutter disposed on the branch fiber and blocking an optical signal propagating through the branch fiber. Obtaining registration information and failure information of each of the subscriber-side terminators from all the station-side terminators,
When a path that cannot be communicated between the station-side terminator and the subscriber-side terminator occurs, the spare branch fiber connected to the second splitter to which the branch fiber used by the path is connected The optical communication system according to claim 11, further comprising a controller that issues a switching instruction to the optical switch to which the auxiliary branch fiber is connected so as to be a new route.   The controller uses the branch optical shutter disposed in the branch fiber used by the path when the path that cannot be communicated between the station-side termination apparatus and the subscriber-side termination apparatus is generated. The optical communication system according to claim 13, wherein the optical communication system is cut off. An optical communication method for an optical communication system according to claim 11 or 12,
Obtaining registration information and failure information of each of the subscriber-side terminators from all the station-side terminators,
When a path that cannot be communicated between the station-side terminator and the subscriber-side terminator occurs, the spare branch fiber connected to the second splitter to which the branch fiber used by the path is connected An optical communication method characterized by switching to a new route. M (M is an integer of 2 or more) station-side termination devices capable of accommodating a maximum of A (A is an integer of 2 or more) subscriber-side termination devices;
A branching ratio of 1: (M−1) × 2, and for each of the station-side terminators, M first splitters whose merging side is connected to one of the station-side terminators;
A branching ratio of 2: Y ′ (Y ′ is an integer satisfying 2 or more and A / M or less), and (M−1) × M or less second splitters;
(M-1) × Y ′ × M or less subscriber-side terminators connected to each port on the Y′-side branch number of the second splitter;
K (K is equal to or greater than 2) that connects M−1 ports, which is one set on the branch side of the first splitter, and one port on the side where the number of branches of the second splitter is 2 on a 1: 1 basis. (M−1) × an integer less than or equal to M) branch fiber,
For each first splitter connected by the branch fiber, the first splitter and the second splitter form a group, and the second splitter belonging to one group belongs to different other groups. In order to couple with the first splitter, another port having the number of branches of the second splitter of 2 and the other set of M-1 ports on the branch side of the first splitter are 1: 1. K spare branch fibers connected by
A spare optical shutter disposed on the spare branch fiber and blocking an optical signal propagating through the spare branch fiber;
An optical communication system comprising:   The optical communication system according to claim 16, further comprising a branch optical shutter disposed on the branch fiber and blocking an optical signal propagating through the branch fiber. Obtaining registration information and failure information of each of the subscriber-side terminators from all the station-side terminators,
During normal operation, the auxiliary optical fiber path is blocked by the auxiliary optical shutter,
When a path that cannot be communicated between the station-side terminator and the subscriber-side terminator occurs, the spare branch fiber connected to the second splitter to which the branch fiber used by the path is connected 18. The optical communication system according to claim 16, further comprising a controller that issues an opening instruction to the auxiliary optical shutter to which the auxiliary branch fiber is connected so as to be a new path. The controller is
Normally, the branch line light shutter is opened,
When a path that cannot be communicated between the station-side terminator and the subscriber-side terminator occurs, the path is blocked by the branch optical shutter disposed on the branch fiber used by the path. The optical communication system according to claim 18. An optical communication method for an optical communication system according to claim 16 or 17,
Obtaining registration information and failure information of each of the subscriber-side terminators from all the station-side terminators,
During normal operation, the auxiliary optical fiber path is blocked by the auxiliary optical shutter,
When a path that cannot be communicated between the station-side terminator and the subscriber-side terminator occurs, the spare branch fiber connected to the second splitter to which the branch fiber used by the path is connected An optical communication method comprising: opening the spare optical shutter connected to the spare branch fiber so as to form a new path. M (M is an integer of 2 or more) station-side termination devices capable of accommodating a maximum of A (A is an integer of 2 or more) subscriber-side termination devices;
A branching ratio of 1: (M−1) × M, and for each of the station-side terminators, M first splitters whose merging side is connected to one of the station-side terminators;
A branching ratio of M: Y ′ (Y ′ is an integer satisfying A / M of 2 or more), and (M−1) × M or less second splitters;
(M-1) × Y ′ × M or less subscriber-side terminators connected to each port on the Y′-side branch number of the second splitter;
K (K is 2 or more) and connects M−1 ports, which is one set on the branch side of the first splitter, and one port on the side where the number of branches of the second splitter is M on a 1: 1 basis. (M−1) × an integer less than or equal to M) branch fiber,
For each of the first splitters connected by the branch fiber, the first splitter and the second splitter form a group, and the number of branches of the second splitter belonging to one group is other than M side. So that the number of branches of the second splitter is the other set on the branch side of the first splitter and the other port on the branch side of the first splitter. and K × (M-1) to be connected with one present preliminary branch fiber: is ^(M-1) and ^two ports 1
A spare optical shutter disposed on the spare branch fiber and blocking an optical signal propagating through the spare branch fiber;
A branch optical shutter disposed on the branch fiber and blocking an optical signal propagating through the branch fiber;
An optical communication system comprising: M (M is an integer of 2 or more) station-side termination devices capable of accommodating a maximum of A (A is an integer of 2 or more) subscriber-side termination devices;
A branching ratio of 1: B (B is an integer greater than or equal to M), and for each of the station-side terminators, M first splitters whose merging side is connected to one of the station-side terminators;
M branch-line optical shutters connected to each of the first splitters, each of which opens and closes B optical paths combined with B ports on the branch side of the first splitter;
B second splitters with a branching ratio of M: Y ″ (Y ″ is an integer satisfying 2 or more and A / {B− (M−1)});
A subscriber-side terminating device of B × Y ″ or less connected for each port on the Y ″ side branching number of the second splitter;
B × M branch fibers that connect the B optical paths of the branch light shutters and the ports on the side where the number of branches of the second splitter is M are 1: 1.
With
The branch line light shutter is
Opening at least one optical path for each first splitter;
An optical communication system characterized in that the number of paths formed at any time with any of the first splitters formed in each of the second splitters is 1 or 0. From all the station-side terminal devices, obtain the bandwidth utilization rate of the subscriber-side terminal device for each of an arbitrary period or an arbitrary moment,
The apparatus further comprises a controller that issues a reconnection instruction to the branch line optical shutter to switch the branch line optical shutter and reconnect the second splitter and the first splitter so that the bandwidth utilization is substantially uniform. An optical communication system according to claim 21 or 22. An optical communication method for an optical communication system according to claim 21 or 22,
From all the station-side terminal devices, obtain the bandwidth utilization rate of the subscriber-side terminal device for each of an arbitrary period or an arbitrary moment,
An optical communication method comprising switching the branch line optical shutter and reconnecting the second splitter and the first splitter so that the bandwidth utilization is substantially uniform.

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