Communication system, control device, and communication method

Abstract

First branch parts for M terminal devices (where M is an integer of 2 or more) output, to the terminal devices, upstream signals received from M first transmission paths and output, to the M first transmission paths, downstream signals from the terminal devices. M second branch parts output, to second transmission paths, uplink signals from the termination devices and transmit, to the termination devices, downlink signals received from the second transmission paths. Path switching parts for the second branch parts are connected by the M first branch parts and the M first transmission paths. The M path switching parts each output, on the basis of the connection relationship between the second branch parts and the terminal devices, the uplink signals received from the second transmission paths to the first transmission paths according to a connection destination of the second branch parts, and output, to the second transmission paths, the downlink signals received from the first transmission paths according to the connection destination of the second branch parts. The control unit determines the connection relationship on the basis of the number of termination devices accommodated in each of the terminal devices and brings the terminal devices which are not connected to the second branch parts into a sleep state.

Description

[Technical Field]

[0001] The present invention relates to a communication system, a control device, and a communication method. [Background technology]

[0002] There are optical communication systems that perform load balancing. Figure 5 shows an example of an optical communication system to which N:M protection is applied. N:M protection distributes the load of N devices among M devices.

[0003] The four OLTs (Optical Line Terminals) shown in Figure 5 can each accommodate up to 64 ONUs (Optical Network Units). Under normal conditions, each OLT communicates with 32 ONUs. An N:2 splitter is provided between the fiber connected to each ONU and the two fibers under the OLT. An optical switch is placed between the OLT and the N:2 splitter, traversing the paths under each OLT. This means that if one OLT fails, one of the remaining three OLTs can communicate with all 32 ONUs under the failed OLT via the optical switch. In other words, one functioning OLT takes over all the ONUs under the failed OLT and communicates with a total of 64 ONUs (the original 32 ONUs plus the 32 ONUs it took over). Furthermore, since the fibers between the N:2 splitter and the optical switch are redundant, the system can also handle fiber breaks at this point. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2011-071951 [Overview of the project] [Problems that the invention aims to solve]

[0005] In conventional optical communication systems, even if there are few ONUs connected to the N:2 splitters leading to each OLT, and even if there is ample capacity for ONUs in each OLT, the same number of OLTs as the number of splitters must be constructed. Therefore, conventional optical communication systems cannot reduce construction and operation costs even when the number of ONUs is small, resulting in an uneconomical equipment configuration. Furthermore, even when there is ample capacity for ONUs, the OLT consumes power equivalent to that at maximum capacity. In the example in Figure 5, under normal circumstances, one OLT can accommodate 32 ONUs. However, because N:2 splitters are installed in four locations, four OLTs are constructed regardless of the number of ONUs connected to the N:2 splitters. Therefore, even when the number of ONUs is small, the construction and operation costs and power consumption of four OLTs are incurred.

[0006] In view of the above circumstances, the present invention aims to provide a communication system, a control device, and a communication method that can reduce costs and power consumption when the number of termination devices is small. [Means for solving the problem]

[0007] One aspect of the present invention comprises M terminal devices (where M is an integer of 2 or more), M first branching units provided for each terminal device, which transmit uplink signals received from each of the M first transmission lines to the terminal device and branch downlink signals transmitted from the terminal device to each of the M first transmission lines, M second branching units which output uplink signals transmitted from each of the multiple terminal devices to a second transmission line and branch downlink signals received from the second transmission line to each of the multiple terminal devices, and M second branching units provided for each of the M first branching units and connected to each of the first transmission lines, which, based on the connection relationship between the second branching unit and the terminal device, transmit uplink signals received from the second branching unit via the second transmission line to the terminal device to which the second branching unit is connected The communication system comprises: M route switching units that perform a first transfer process to output to the first transmission path between the first branch and the first branch; a second transfer process that outputs to the second transmission path between the second branch and the first branch, out of the downlink signals received from each of the M first branch units, the downlink signals received from the first transmission path between the first branch and the terminal station corresponding to the terminal station connected to the second branch; a control unit that determines the connection relationship between the second branch and the terminal station based on the number of terminal stations housed in each terminal station, controls the route switching units to perform the first and second transfer processes based on the determined connection relationship, and instructs terminal stations that are determined not to be connected to any of the second branch units to enter a sleep state.

[0008] One aspect of the present invention comprises M terminal devices (where M is an integer of 2 or more), M first branching units provided for each terminal device, which transmit uplink signals received from each of the M first transmission lines to the terminal device and branch downlink signals transmitted from the terminal device to each of the M first transmission lines, M second branching units which output uplink signals transmitted from each of the plurality of terminal devices to a second transmission line and branch downlink signals received from the second transmission line to each of the plurality of terminal devices, and M second branching units provided for each of the M first branching units and connected to each of the first transmission lines, which, based on the connection relationship between the second branching unit and the terminal device, transmit uplink signals received from the second branching unit via the second transmission line to the first branching unit corresponding to the terminal device to which the second branching unit is connected. A control device for controlling a communication system having M route switching units that perform a first transfer process to output to a first transmission path, and a second transfer process to output to a second transmission path between the second branch and the first branch, from among the downlink signals received from each of the M first branch units, the downlink signals received from the first transmission path between the first branch unit and the terminal station corresponding to the terminal station connected to the second branch unit, the control device further comprising a control unit that determines the connection relationship between the second branch unit and the terminal station based on the number of terminal stations housed in each terminal station, controls the route switching units to perform the first transfer process and the second transfer process based on the determined connection relationship, and instructs terminal stations that are determined not to be connected to any of the second branch units to enter a sleep state.

[0009] One aspect of the present invention is a first branching step in which each first branching unit provided for each M terminal station (where M is an integer of 2 or more) transmits an uplink signal received from each of the M first transmission lines to the terminal station, and branches the downlink signal transmitted from the terminal station and outputs it to each of the M first transmission lines; each of the M second branching units outputs an uplink signal transmitted from each of the multiple terminal stations to a second transmission line, and branches the downlink signal received from the second transmission line and transmits it to each of the multiple terminal stations; and each path switching unit provided for each of the M first branching units and connected to each of the first transmission lines transmits an uplink signal received from the second branching unit via the second transmission line to the destination of the second branching unit based on the connection relationship between the second branching unit and the terminal station. A communication method comprising: a transfer step of performing a first transfer process to output to the first transmission path between the terminal station device and the first branch corresponding to the terminal station device; a second transfer process of outputting the downlink signal received from the first transmission path between the second branch and the terminal station device to which the second branch is connected, from among the downlink signals received from each of the M first branch, to the second transmission path between the second branch; a control step of the control unit determining the connection relationship between the second branch and the terminal station device based on the number of terminal devices housed in each of the terminal station devices, controlling the route switching unit to perform the first transfer process and the second transfer process based on the determined connection relationship, and instructing the terminal station device that is determined not to be connected to any of the second branch to enter a sleep state. [Effects of the Invention]

[0010] This invention makes it possible to reduce costs and power consumption when the number of termination devices in a communication system is small. [Brief explanation of the drawing]

[0011] [Figure 1] This is a diagram illustrating the configuration of an optical communication system according to one embodiment of the present invention. [Figure 2] This is a functional block diagram of the optical communication system according to the same embodiment. [Figure 3] It is a flowchart showing the processing of the optical communication system according to the same embodiment. [Figure 4] It is a diagram showing the hardware configuration of the controller according to the same embodiment. [Figure 5] It is a configuration diagram of an optical communication system according to the prior art.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] FIG. 1 is a configuration diagram of an optical communication system 1 according to an embodiment of the present invention. The optical communication system 1 includes M OLTs 2 (M is an integer of 2 or more), M M:1 splitters 3, an optical switch 4, M N:2 splitters 5, a plurality of ONUs 6, and a controller 7. The OLT 2 is an example of an end office device, the ONU 6 is an example of a terminal device, and the controller 7 is an example of a control device. The physical configuration of the optical communication system 1 shown in FIG. 1 is a configuration in which an M:1 splitter is added between each OLT and the optical switch in a conventional optical communication system. This makes it possible to aggregate the communications of a plurality of N:2 splitters 5 to one OLT 2. Further, the optical communication system 1 shown in FIG. 1 connects a controller 7 that controls connection aggregation and redispersion to each OLT 2 and the optical switch 4. FIG. 1 is an example when M = 4.

[0014] The M:1 splitter 3 is connected to the OLT 2 by one optical transmission line 81 and is connected to the optical switch 4 by M optical transmission lines 82. The N:2 splitter 5 is connected to the optical switch 4 by two optical transmission lines 83 and is connected to each of two to N ONUs 6 by an optical transmission line 84. The optical transmission lines 81, 82, 83, and 84 are, for example, core wires. The core wire is an optical fiber covered with a coating. The optical transmission lines 81 and 82 to which the N:2 splitter 5 is connected via the optical switch 4 are called upper-level core wires. The optical switch 4 switches the path between the optical transmission line 82 and the optical transmission line 83 so that the upper-level core wires of the N:2 splitter 5 become the optical transmission lines 81 and 82 between any OLT 2 according to the instruction from the controller 7.

[0015] Hereinafter, the M OLTs 2 are described as OLT2-1 to 2-M respectively, the M M:1 splitters 3 are described as M:1 splitter 3-1 to 3-M respectively, and the M N:2 splitters 5 are described as N:2 splitter 5-1 to 5-M respectively. The optical transmission line 81 between the OLT2-y (y is an integer from 1 to M) and the M:1 splitter 3-y is described as the optical transmission line 81-y, and the M optical transmission lines 82 between the M:1 splitter 3-y and the optical switch 4 are described as the optical transmission lines 82-y-1 to 82-y-M respectively. Also, the optical transmission line 83 between the optical switch 4 and the N:2 splitter 5-y is described as the optical transmission line 83-y. One of the two optical transmission lines 83-y is the active system, and the other is the backup system. The optical transmission line 84 between the N:2 splitter 5-y and each of two to N ONUs 61 is described as the optical transmission line 84-y, and the ONU 61 connected to the N:2 splitter 5-y via the optical transmission line 84-y is described as the ONU 61-y.

[0016] From immediately after the construction of the equipment, the optical communication system 1 connects to OLT2 and aggregates communications by connecting the upper core lines of all N:2 splitters 5-1 to 5-M to one OLT2 until the number of ONU6 that are running exceeds N.N is the maximum number of ONU6 that one OLT2 can accommodate, i.e., one splitter or less.N may also be the maximum number of ONU6 that one OLT2 can accommodate under normal circumstances. Normally, the optical switch 4 uses the operational optical transmission line 83 and does not use the backup optical transmission line 83. If a failure occurs in the operational optical transmission line 83-y, the controller 7 instructs the optical switch 4 to change the backup optical transmission line 83-y to the operational system and make the failed optical transmission line 83-y the backup system. The optical switch 4 changes the transmission path of optical signals that were previously input / output destinations to the backup optical transmission line 83-y so that the newly operational optical transmission line 83-y becomes the input / output destination.

[0017] In the optical communication system 1 shown in Figure 1, until the total number of active ONUs 6-1 to 6-4 exceeds N units, the upper cores of all N:2 splitters 5-1 to 5-4 are connected to OLT2-1. In other words, the optical switch 4 is configured with paths between the operational optical transmission lines 83-1 and 82-1-1, 83-2 and 82-1-2, 83-3 and 82-1-3, and 83-4 and 82-1-4. OLT2-2 to 2-4 are in sleep mode. Sleep mode is a state in which power supply to some circuits is cut off. Therefore, power consumption is lower in sleep mode than in normal operating mode.

[0018] In the above case, the optical communication system 1 performs uplink communication as follows: N:2 splitters 5-m1 (m1=1,2,3,4) split the uplink optical signals transmitted from each ONU 6-m1 and output them to the operational optical transmission line 83-m1 and the backup optical transmission line 83-m1. The optical switch 4 outputs the uplink optical signal input from the operational optical transmission line 83-m1 to the optical transmission line 82-1-m1 between it and the M:1 splitter 3-1 according to the set path. The M:1 splitter 3-1 outputs the uplink optical signals from ONU 6-m1 transmitted via each N:2 splitter 5-m1 to the OLT2-1.

[0019] Furthermore, the optical communication system 1 performs downlink communication as follows: OLT2-1 outputs a downlink optical signal destined for ONU6-m1. M:1 splitter 3-1 splits the downlink optical signal into four, and outputs each of the split optical signals to optical switch 4 via optical transmission lines 82-1-1 to 82-1-4. Optical switch 4 outputs the optical signal input from optical transmission line 82-1-m1 to the operational optical transmission line 83-m1 according to the set path. N:2 splitter 5-m1 splits the downlink optical signal input from optical transmission line 83-m1, and transmits the split downlink signals to ONU6-m1 via optical transmission line 84-m1.

[0020] If the total number of ONU6 connected to one OLT2 and currently running exceeds N, the optical communication system 1 changes the connection of one of the upper-level cores of the N:2 splitter 5 connected to that OLT2 to another OLT2. This connection change is performed by the controller 7 controlling the mirror in the optical switch 4 and changing the path.

[0021] Let's explain using the example shown in Figure 1, where the total number of ONUs 6-1 to 6-4 housed in OLT2-1 reaches N units, and the upper core of the N:2 splitter 5-4 is changed from OLT2-1 to OLT2-2. In this case, the controller 7 instructs the optical switch 4 to change the connection destination of the N:2 splitter 5-4 from OLT2-1 to OLT2-2. The optical switch 4 switches the path to change the connection destination of the operational optical transmission line 83-4 from optical transmission line 82-1-4 to optical transmission line 82-2-4. The controller 7 also switches OLT2-2 from sleep state to wake state.

[0022] The optical communication system 1 performs uplink communication as follows: Each N:2 splitter 5-m1 (m1=1,2,3,4) outputs the uplink optical signal transmitted from ONU 6-m1 to the active optical transmission line 83-m1 and the backup optical transmission line 83-m1. The optical switch 4 outputs the uplink optical signal input from the active optical transmission line 83-m2 (m2=1,2,3) to the optical transmission line 82-1-m2 between it and M:1 splitter 3-1, and outputs the uplink optical signal input from the active optical transmission line 83-4 to the optical transmission line 82-2-4 between it and M:1 splitter 3-2. The M:1 splitter 3-1 outputs the uplink optical signal from ONU 6-m2 transmitted via N:2 splitter 5-m2 to OLT2-1, and the M:1 splitter 3-2 outputs the uplink optical signal from ONU 6-4 transmitted via N:2 splitter 5-4 to OLT2-2.

[0023] Furthermore, the optical communication system 1 performs downlink communication as follows: OLT2-1 outputs a downlink optical signal destined for ONU6-m2. M:1 splitter 3-1 splits the downlink optical signal into four, and outputs each of the split optical signals to optical switch 4 via optical transmission lines 82-1-1 to 82-1-4. Optical switch 4 outputs the optical signal input from optical transmission line 82-1-m2 to the operational optical transmission line 83-m2, but does not output the optical signal input from optical transmission line 82-1-4. N:2 splitter 5-m2 splits the downlink optical signal input from optical transmission line 83-m2 and transmits the split downlink signals to ONU6-m2 via optical transmission line 84-m2. Also, OLT2-2 outputs a downlink optical signal destined for ONU6-4. M:1 splitter 3-2 splits the downstream optical signal into four, and outputs each of the split optical signals to optical switch 4 via optical transmission lines 82-2-1 to 82-2-4. Optical switch 4 does not output the optical signal input from optical transmission line 82-2-m2, but outputs the optical signal input from optical transmission line 82-2-4 to the operational optical transmission line 83-4. N:2 splitter 5-4 splits the downstream optical signal input from optical transmission line 83-4, and transmits the split downstream signals to ONU 6-4 via optical transmission line 84-4.

[0024] Each OLT2 monitors the operational status of the connected ONU6 and, if it detects a decrease in the number of running ONU6, notifies the controller 7 of the decrease in the number of ONUs. Upon receiving the notification, the controller 7 instructs all OLT2s to check the number of running ONUs and report the results. Upon receiving the instruction, each OLT2 checks the number of ONU6s connected to its device and running, and notifies the controller 7 of the results. Alternatively, the controller 7 may receive all notifications from each OLT2 regarding increases or decreases in the number of running ONU6s and manage the number of running ONU6s connected to each OLT2 internally.

[0025] When the controller 7 detects a decrease in the number of running ONU6s, it checks for each combination of OLT2s consisting of two or more OLT2s whether the total number of ONU6s housed in each OLT2 constituting the combination is N or less. If the controller 7 determines that there is a combination in which the total number of ONU6s is N or less, it aggregates the upper-level cores of the N:2 splitter 5 connected to each OLT2 constituting that combination into optical transmission paths 81 and 82 connected to one of the OLT2s in that combination. The controller 7 puts the OLT2s not connected to any running ONU6s into sleep mode.

[0026] For example, suppose OLT2-1 houses ONU6-1 to 6-3 and OLT2-2 houses ONU6-4, and the total number of active ONU6-1 to 6-4 falls below N. The controller 7 detects that the total number of ONU6 connected to the combination of OLT2-1 and OLT2-2 has fallen below N, and decides to consolidate the housing of these ONU6 to OLT2-1. The controller 7 instructs the optical switch 4 to change the connection destination of the N:2 splitter 5-4 from OLT2-2 to OLT2-1. The optical switch 4 switches the path to change the connection destination of the operational optical transmission line 83-4 from optical transmission line 82-2-4 to optical transmission line 82-1-4. Furthermore, the controller 7 puts OLT2-2 into sleep mode.

[0027] Furthermore, if an operational OLT2 fails, the controller 7 selects one of the operational OLT2s that is not experiencing a failure. The controller 7 may also instruct the optical switch 4 to change the upper core wire of the N:2 splitter 5 connected to the failed OLT2 to optical transmission paths 81 and 82 connected to the selected OLT2.

[0028] As described above, the controller 7 connects to each OLT2 and maximizes the number of ONU6 that are running. This minimizes the number of OLTs required when only a small number of ONU6 are connected and running, thereby achieving cost reduction and power saving.

[0029] Figure 2 is a functional block diagram of each device in the optical communication system 1. Note that the auxiliary optical transmission lines 83-1 to 83-4 are omitted from Figure 2. The OLT2 comprises a control unit 21, a signal transmission / reception unit 22, and a signal processing unit 23. For example, the control unit 21, the signal transmission / reception unit 22, and the signal processing unit 23 are mounted on an OSU (Optical Subscriber Unit).

[0030] The control unit 21 performs control for communication with the ONU 6 located in the OLT 2. This control includes registration management of the ONU 6 and uplink bandwidth allocation. The control unit 21 stores information related to these controls as configuration information and uses it when performing the control.

[0031] The signal transmission / reception unit 22 converts the upstream optical signal received from the ONU 6 via the optical transmission path 81 into an electrical signal and outputs it to the signal processing unit 23. The signal transmission / reception unit 22 also converts the electrical signal output by the signal processing unit 23 into a downstream optical signal destined for the ONU 6 and transmits it via the optical transmission path 81. The signal transmission / reception unit 22 has a light source for receiving and generating optical signals.

[0032] The signal processing unit 23 acquires the main signal destined for the higher-level device from the upstream signal output by the signal transmission / reception unit 22 and outputs it to the higher-level network (not shown). The signal processing unit 23 also converts the downstream main signal received from the higher-level network (not shown) into an optical signal format and outputs it to the signal transmission / reception unit 22.

[0033] The M:1 splitter 3-y outputs the uplink optical signal input from optical transmission lines 82-y-1 to 82-yM to optical transmission line 81-y. In addition, the M:1 splitter 3-y splits the downlink optical signal input from optical transmission line 81-y into M signals, and outputs each of the branched optical signals to optical transmission lines 82-y-1 to 82-yM, respectively.

[0034] The optical switch 4 comprises an optical switch control unit 41 and a switch unit 42. The optical switch control unit 41 outputs a path switching signal to control the transfer path of the optical signal in the switch unit 42 according to a path switching instruction from the controller 7.

[0035] The switch unit 42 includes M path switching units 43. The M path switching units 43 are denoted as path switching units 43-1 to 43-M. Path switching unit 43-y is connected to optical transmission paths 82-1-y to 82-My and optical transmission path 83-y. Path switching unit 43-y connects one of the M:1 splitters 3-1 to 3-M to the N:2 splitter 5-y by controlling a mirror according to path switching instructions from the optical switch control unit 41. The M:1 splitter 3 connected to the N:2 splitter 5-y by the path set in the path switching unit 43-y is connected to the M:1 splitter 3-m y (m y (where is an integer between 1 and M). The path switching unit 43-y receives the uplink optical signal from the optical transmission path 83-y between it and the N:2 splitter 5-y, and sends it to the M:1 splitter 3-m y Optical transmission path 82-m between y -y outputs. Also, the path switching unit 43-y outputs the downstream optical signals input from each of the optical transmission paths 82-1-y to 82-My to the M:1 splitter 3-m y Optical transmission path 82-m between y - The optical signal input from -y is output to the N:2 splitter 5-y via the optical transmission path 83-y, and no other optical signals are output.

[0036] The controller 7 comprises an operation processing unit 71 and a light emission control unit 72. The operation processing unit 71 receives operational ONU notifications from each OLT2. The operational ONU notification indicates the number of operational ONUs. The number of operational ONUs indicates the number of ONUs 6 connected to the OLT2 that sent the operational ONU notification and that are currently operational. The operation processing unit 71 determines the number of operational ONUs in each OLT2 based on the received operational ONU notifications. Based on the number of operational ONUs in each OLT2, the operation processing unit 71 determines the change of the OLT2 to which the ONUs 6 are housed, on a per-N:2 splitter 5 basis. The operation processing unit 71 determines the upper-level core wire of the N:2 splitter 5 so that the ONUs 6 are housed in the new OLT2 after the change. The operation processing unit 71 outputs a route switching instruction to the optical switch 4, instructing it to switch the route so that the N:2 splitter 5 is connected to the determined upper-level core wire. Furthermore, the operation processing unit 71 outputs a housing combination instruction to the light emission control unit 72 indicating the OLT2 to which each N:2 splitter 5 is connected by the upper core wire.

[0037] The light emission control unit 72 understands the change in whether or not an ONU 6 is housed in each OLT2 based on the accommodation combination instruction from the operation processing unit 71. The light emission control unit 72 instructs an OLT2 that no longer houses an ONU 6 due to a switch in its accommodation destination to turn off light emission. When the control unit 21 of the OLT2 receives the instruction to turn off light emission, it stops the light emission of the light source of the signal transmitting and receiving unit 22. This puts the OLT2 into a sleep state and reduces power consumption. The light emission control unit 72 also instructs an OLT2 that will house an ONU 6 due to a switch in its accommodation destination to turn on light emission. When the control unit 21 of the OLT2 receives the instruction to turn on light emission, it starts the light emission of the light source of the signal transmitting and receiving unit 22. This causes the OLT2 to exit the sleep state.

[0038] Figure 3 is a flowchart showing the processing of the optical communication system 1. The operation processing unit 71 of the controller 7 keeps track of the number of operational ONUs in each OLT2 based on the operational ONU notification received from OLT2. The number of operational ONUs in OLT2-y is the number of ONUs n y Let's assume that.

[0039] The operation processing unit 71 of the controller 7 determines whether any of the OLTs 2 under the controller 7 accommodates the ONU 6 (step S1). When the operation processing unit 71 determines that any of the OLTs 2 accommodates the ONU 6 (step S1: YES), the total number of ONUs Σn under the controller 7 y is calculated. The total number of ONUs Σn y is the sum of the number of ONUs n1 to n of each of the OLTs 2-1 to 2-M M .

[0040] The controller 7 determines whether the total number of ONUs Σn y satisfies the following formula (1) (step S2). Here, X (≤ M) is the number of OLTs 2 in operation, and N is the number of ONUs 6 that one OLT 2 can accommodate.

[0041] N(X - 1) < Σn y ≤ NX …(1)

[0042] When the operation processing unit 71 determines that the formula (1) is satisfied (step S2: YES), it puts the OLT 2 that does not accommodate the ONU 6 into the sleep state (step S3). Specifically, the operation processing unit 71 outputs an accommodation combination instruction indicating the OLT 2 to which each N:2 splitter 5 is connected to the light emission control unit 72. Based on the accommodation combination instruction, the light emission control unit 72 determines that the OLT 2 not connected to any N:2 splitter 5 does not accommodate the ONU 6. The light emission control unit 72 instructs the OLT 2 that does not accommodate the ONU 6 to turn off the light emission. When receiving the instruction to turn off the light emission, the control unit 21 of the OLT 2 stops the light emission of the light source of the signal transmission / reception unit 22. Note that the light emission control unit 72 does not need to instruct the OLT 2 that has already stopped the light emission of the light source to turn off the light emission.

[0043] On the other hand, when the operation processing unit 71 determines in step S2 that the formula (1) is not satisfied (step S2: NO), the number of ONUs n of each of the X OLTs 2-y in operation yThe operation processing unit 71 obtains the following. The operation processing unit 71 generates different combinations consisting of multiple OLT2s selected from the X OLT2s that are currently running. For each combination, the operation processing unit 71 determines the number of ONUs n for each OLT2-y that constitute the combination. y The sum of the ONUs n is calculated. The operation processing unit 71 calculates the sum of the ONUs n. y Select a combination whose sum is less than or equal to N. The operation processing unit 71 determines whether there are multiple selected combinations (step S4).

[0044] If the operation processing unit 71 determines that there is only one selected combination (step S4: NO), it controls the optical switch 4 to set the number of ONUs n y The upper core wire of the N:2 splitter 5 is switched so that the sum of the two values ​​is less than or equal to N, and the ONU 6 is rearranged (step S5).

[0045] For example, suppose the selected combination consists of OLT2-y1 and OLT2-y2 (where y1 and y2 are integers between 1 and M, and y1 ≠ y2). ONU number n y1 and n y2 The sum of these is less than or equal to N. Also, assume that OLT2-y1 houses ONU6-z1, and OLT2-y2 houses ONU6-z2 and ONU6-z3 (z1, z2, and z3 are integers between 1 and M, and z1 ≠ z2 ≠ z3). The operation processing unit 71 decides which of OLT2-y1 and OLT2-y2 will be the aggregation destination. For example, the operation processing unit 71 may select OLT2, which has more ONUs. This reduces the number of ONU6 whose destination changes. Here, we assume that OLT2-y1 is selected.

[0046] The operation processing unit 71 outputs a route switching instruction to the optical switch 4 to switch the connection destination of N:2 splitter 5-z2 and N:2 splitter 5-z3 to OLT2-y1. Based on the received route switching instruction, the optical switch control unit 41 of the optical switch 4 switches the route in the route switching unit 43-z2 to change the connection destination of optical transmission path 83-z2 from optical transmission path 82-y2-z2 to optical transmission path 82-y1-z2, and switches the route in the route switching unit 43-z3 to change the connection destination of optical transmission path 83-z3 from optical transmission path 82-y2-z3 to optical transmission path 82-y1-z3. As a result, the upper core of the N:2 splitter 5-z2 is changed to optical transmission paths 81-y1 and 82-y1-z2 with respect to OLT2-y1, and the upper core of the N:2 splitter 5-z3 is changed to optical transmission paths 81-y1 and 82-y1-z3 with respect to OLT2-y1.

[0047] Furthermore, the operation processing unit 71 may send a switching instruction to OLT2-y1 and OLT2-y2 instructing them to change the destination of ONU6-z2 and ONU6-z3 to OLT2-y1. The control unit 21 of OLT2-y2 notifies the destination OLT2-y1 of the setting information for ONU6-z2 and ONU6-z3, which are the targets of the switching. The control unit 21 of OLT2-y1 uses the setting information received from OLT2-y2 to accommodate ONU6-z2 and ONU6-z3.

[0048] After the processing in step S5, the operation processing unit 71 of the controller 7 puts the OLT2 that does not house the ONU6 into sleep mode (step S3). As a result, in the above case, OLT2-y2 enters a sleep state.

[0049] Furthermore, if the operation processing unit 71 determines that there are multiple combinations selected in step S4 (step S4: YES), it performs the process in step S6. That is, the operation processing unit 71 determines whether there are multiple combinations among the multiple selected combinations that result in the minimum number of OLT2 units X running after destination aggregation (step S6). Specifically, the operation processing unit 71 determines whether there are multiple combinations among the multiple combinations selected in step S4 that consist of the largest number of OLT2 units.

[0050] If the operation processing unit 71 determines that there is only one combination that minimizes the number of OLT2 units X that are running after the consolidation of destinations (step S6: NO), it uses that combination to reconfigure the ONU6 (step S7). The reconfiguration is performed in the same way as in step S5. After the processing in step S7, the operation processing unit 71 of the controller 7 puts the OLT2 units that do not contain an ONU6 into sleep mode (step S3).

[0051] If the operation processing unit 71 determines that there are multiple combinations that result in the minimum number of OLT2s X running after destination consolidation (step S6: YES), it performs the process in step S8. That is, the operation processing unit 71 selects the combination from among these multiple combinations that, when the ONU6s are consolidated into one of the OLT2s constituting that combination, has the fewest number of ONU6s whose destination OLT2s are changed. The operation processing unit 71 performs the ONU6 relocation using the selected combination (step S8). The relocation is performed in the same manner as in step S5. After the process in step S8, the operation processing unit 71 of the controller 7 puts the OLT2s that do not contain ONU6s to sleep (step S3).

[0052] After the processing in step S3, the operation processing unit 71 determines the total number of ONUs Σn based on the operational ONU notification received from OLT2. y The operation processing unit 71 determines whether there has been an increase or decrease in the total number of ONUs Σn yIf it is determined that the number has decreased (step S9: decrease), the process from step S1 is repeated. Meanwhile, the operation processing unit 71 determines the total number of ONUs Σn y If it is determined that the value has increased (Step S9: Increase), the process from Step S2 is repeated.

[0053] Furthermore, if the total number of ONU6s accommodated by any operational OLT2-y1 reaches N, the operation processing unit 71 of the controller 7 changes the connection destination of one of the N:2 splitter 5-z (where z is an integer between 1 and M) among the multiple N:2 splitters 5 connected to OLT2-y1 to another OLT2. The operation processing unit 71 may choose any sleeping OLT2 as the new connection destination, or it may choose an operational OLT2 in which the number of connected ONUs does not exceed N even if all the operational ONU6s connected to N:2 splitter 5-z are further accommodated.

[0054] For example, the operation processing unit 71 decides to switch the upper core wire of N:2 splitter 5-z, one of the multiple N:2 splitters 5 connected to OLT2-y1, to optical transmission paths 81-y2 and 82-y2-z between it and OLT2-y2. The operation processing unit 71 outputs a path switching instruction to the optical switch 4 to switch the connection destination of N:2 splitter 5-z to OLT2-y2. The optical switch control unit 41 of the optical switch 4 changes the path in the path switching unit 43-z to change the connection destination of optical transmission path 83-z from optical transmission path 82-y1-z to optical transmission path 82-y2-z based on the received path switching instruction. The operation processing unit 71 also outputs a housing combination instruction to the light emission control unit 72 indicating the OLT2 to which each N:2 splitter 5 is connected. When the light emission control unit 72 detects that the connection destination of OLT2-y2 has changed from none to N:2 splitter 5-z based on the accommodation combination instruction, it instructs OLT2-y2 to turn on light emission. When the control unit 21 of OLT2-y2 receives the instruction to turn on light emission, it starts emitting light from the light source of the signal transmission / reception unit 22.

[0055] According to this embodiment, the number of ONUs 6 housed in an operational OLT2 can be maximized so that the number of operational OLT2s is minimized. Therefore, when the number of ONUs 6 is small, the number of OLT2s in sleep mode can be increased, thereby reducing operating costs and power consumption.

[0056] The following describes examples of hardware configurations for each device. Figure 4 is a device configuration diagram showing an example of the hardware configuration of controller 7. Controller 7 comprises a processor 91, a storage unit 92, a communication interface 93, and a user interface 94.

[0057] The processor 91 is a central processing unit that performs calculations and control. The processor 91 is, for example, a CPU (central processing unit) or a GPU (Graphics Processing Unit). The processor 91 reads and executes programs from the memory unit 92. The memory unit 92 further includes a work area for when the processor 91 executes various programs. The communication interface 93 connects to other devices for communication. The user interface 94 consists of input devices such as a keyboard, pointing device (mouse, tablet, etc.), buttons, and touch panel, as well as display devices such as a display. Human input is received through the user interface 94.

[0058] The functions of the operation processing unit 71 and the light emission control unit 72 are realized by the processor 91 reading and executing a program from the memory unit 92. Note that all or part of these functions may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), or FPGA (Field Programmable Gate Array). The memory unit 92 is itself implemented by the memory unit 92. The communication interface 93 transmits and receives control signals between the OLT2 and the optical switch 4.

[0059] Alternatively, the controller 7 may be implemented using multiple computer devices connected to a network. In this case, it is arbitrary which of these multiple computer devices implements each function of the controller 7.

[0060] The configuration of OLT2 is the same as in Figure 4. In this case, the functions of the control unit 21 are realized by the processor 91 reading and executing a program from the memory unit 92. Note that all or part of the functions of the control unit 21 may be realized using hardware such as an ASIC, PLD, or FPGA. The signal transmission / reception unit 22 and the signal processing unit 23 are realized by the communication interface 93. The communication interface 93 also transmits and receives control signals with the controller 7.

[0061] Furthermore, the configuration of the optical switch 4 is the same as in Figure 4. In this case, the function of the optical switch control unit 41 is realized by the processor 91 reading and executing a program from the memory unit 92. Note that all or part of the function of the optical switch control unit 41 may be realized using hardware such as an ASIC, PLD, or FPGA. The switch unit 42 is realized by the communication interface 93. The communication interface 93 also transmits and receives control signals to and from the controller 7.

[0062] According to the embodiment described above, the communication system comprises M terminal devices (where M is an integer of 2 or more), M first branching units, M second branching units, M route switching units, and a control unit. For example, the communication system corresponds to the optical communication system 1 of the embodiment, the terminal device corresponds to the OLT2 of the embodiment, the first branching unit corresponds to the M:1 splitter 3 of the embodiment, the second branching unit corresponds to the N:2 splitter 5 of the embodiment, and the route switching unit corresponds to the route switching unit 43 of the embodiment.

[0063] Each first branch is provided for each terminal device. Each first branch transmits the uplink signals received from each of the M first transmission lines to the terminal device, and branches the downlink signals transmitted from the terminal device and outputs them to each of the M first transmission lines. Each second branch outputs the uplink signals transmitted from each of the multiple terminal devices to the second transmission line, and branches the downlink signals received from the second transmission line and transmits them to each of the multiple terminal devices. A route switching unit is provided for each second branch and is connected to each of the M first branches by a first transmission line. Each route switching unit performs a first transfer process based on the connection relationship between the second branch and the terminal device, which involves outputting the uplink signal received from the second branch via the second transmission line to the first transmission line between the second branch and the terminal device to which the second branch is connected, and a second transfer process, which involves outputting the downlink signal received from each of the M first branch lines, specifically from the first transmission line between the second branch and the terminal device to which the second branch is connected, to the second transmission line between the second branch and the second branch. The control unit determines the connection relationship between the second branch and the terminal station based on the number of termination devices housed in each terminal station. The control unit also performs the following processes: controlling the route switching unit to perform the first and second transfer processes based on the determined connection relationship, and instructing terminal stations that are determined not to be connected to any of the second branch units to enter a sleep state.

[0064] The control unit may, within the limits that the number of termination devices accommodated in each terminal device does not exceed the maximum number of termination devices that can be accommodated, determine that some terminal devices will change the destination of the termination devices they accommodate to other terminal devices, and perform the process of changing the connection relationship so that the connection destination of the second branch connected to the termination device whose destination has been changed becomes the first branch corresponding to the terminal device whose destination has been changed, and the process of instructing terminal devices that are not connected to any second branch after the change in connection relationship to enter a sleep state.

[0065] The control unit selects a combination of terminal stations such that the total number of terminal stations currently accommodated is less than or equal to the number of terminal stations that can be accommodated in a single terminal station, and determines that the destinations of the terminal stations accommodated in each terminal station constituting the selected combination should be consolidated into one of the terminal stations constituting the selected combination. The control unit may also perform a process to change the connection relationship of the second branch connected to the terminal station whose destination has been changed by the consolidation, so that the destination of the second branch is the first branch corresponding to the terminal station whose destination is the consolidated terminal station, and a process to instruct the terminal station that was the destination before the change due to the consolidation to enter a sleep state.

[0066] The terminal unit may notify the control unit of the number of operational terminal units it houses. Furthermore, the uplink and downlink signals may be optical signals.

[0067] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments and include designs and the like that do not depart from the spirit of this invention. [Explanation of Symbols]

[0068] 1. Optical communication system 2-1~2-4 OLT 3 M:1 Splitter 4. Optical switch 5 N:2 Splitter 6-1~6-4 ONU 7 Controllers 21 Control Unit 22 Signal Transceiver Unit 23 Signal Processing Unit 41 Optical switch control unit 42 Switch section 43 Route switching section 81-1~81-4 Optical transmission path 82-1~82-4 Optical transmission path 83-1~83-4 Optical transmission path 84-1~84-4 Optical transmission path 91 processors 92 Memory section 93 Communication Interface 94 User Interface

Claims

1. M terminal devices (where M is an integer greater than or equal to 2), Each terminal station is provided with M first branching units that transmit the uplink signals received from each of the M first transmission lines to the terminal station, and branch the downlink signals transmitted from the terminal station and output them to each of the M first transmission lines. M second branching units that output the uplink signals transmitted from each of the multiple termination devices to a second transmission line, and branch the downlink signals received from the second transmission line and transmit them to each of the multiple termination devices, Each of the M path switching units is provided for each of the M first branch sections and connected to each of the M first branch sections by the first transmission path, and performs a first transfer process that outputs an uplink signal received from the second branch section via the second transmission path to the first branch section corresponding to the terminal station to which the second branch section is connected, based on the connection relationship between the second branch section and the terminal station device, and a second transfer process that outputs a downlink signal received from each of the M first branch sections via the first transmission path to the second branch section corresponding to the terminal station to which the second branch section is connected, to the second transmission path between the second branch section and the second branch section. A control unit that performs the following processes: determining the connection relationship between the second branch unit and the terminal units based on the number of terminal units housed in each of the terminal units, the number of terminal units that are running after the consolidation of destinations for multiple terminal units, or the number of terminal units whose destination terminal unit is changed due to the consolidation of destinations for multiple terminal units, controlling the route switching unit to perform the first transfer process and the second transfer process based on the determined connection relationship, and instructing the terminal units that are determined not to be connected to any of the second branch units to enter a sleep state. A communication system equipped with [the following features].

2. The control unit determines that some of the terminal devices will change the destination of the terminal devices they house, provided that the number of terminal devices housed in each terminal device does not exceed the maximum number of terminal devices that can be housed in each terminal device. The control unit then performs the following processes: modify the connection relationship so that the connection destination of the second branch connected to the terminal device whose destination has been changed is set to the first branch corresponding to the terminal device whose destination has been changed; and instruct the terminal devices that are not connected to any of the second branch after the change in the connection relationship to enter a sleep state. The communication system according to claim 1.

3. The control unit selects a combination of terminal stations such that the total number of terminal stations currently accommodated is less than or equal to the number of terminal stations that can be accommodated in one terminal station, determines that the destinations of the terminal stations accommodated in each of the terminal stations constituting the selected combination should be consolidated into one of the terminal stations constituting the selected combination, performs a process to change the connection relationship so that the connection destination of the second branch connected to the terminal station whose destination has been changed by the consolidation becomes the first branch corresponding to the terminal station whose destination is consolidated, and instructs the terminal station that was the destination before the change due to the consolidation to enter a sleep state. The communication system according to claim 1.

4. The terminal device notifies the control unit of the number of operational terminal devices it has connected. The communication system according to claim 1.

5. The aforementioned up-link signal and down-link signal are optical signals. The communication system according to claim 1.

6. M terminal devices (where M is an integer greater than or equal to 2), Each terminal station is provided with M first branching units that transmit the uplink signals received from each of the M first transmission lines to the terminal station, and branch the downlink signals transmitted from the terminal station and output them to each of the M first transmission lines. M second branching units that output the uplink signals transmitted from each of the multiple termination devices to a second transmission line, and branch the downlink signals received from the second transmission line and transmit them to each of the multiple termination devices, A control device for a communication system having M path switching units, each of which is provided for each of the M first branch units and connected to each of the M first branch units by the first transmission path, and which perform a first transfer process that outputs an uplink signal received from the second branch unit via the second transmission path to the first branch unit corresponding to the terminal unit to which the second branch unit is connected, based on the connection relationship between the second branch unit and the terminal unit, and a second transfer process that outputs a downlink signal received from each of the M first branch units via the first transmission path to the second branch unit corresponding to the terminal unit to which the second branch unit is connected, to the second transmission path to the second branch unit, A control unit that performs the following processes: determining the connection relationship between the second branch and the terminal devices based on the number of terminal devices housed in each of the terminal devices, the number of terminal devices that are running after the consolidation of destinations for multiple terminal devices, or the number of terminal devices whose destination terminal device is changed due to the consolidation of destinations for multiple terminal devices, controlling the route switching unit to perform the first transfer process and the second transfer process based on the determined connection relationship, and instructing the terminal devices that are determined not to be connected to any of the second branch units to enter a sleep state. A control device equipped with the following features.

7. Each of the first branch sections provided for each of the M terminal devices (where M is an integer of 2 or more) transmits the uplink signal received from each of the M first transmission lines to the terminal device, and branches the downlink signal transmitted from the terminal device and outputs it to each of the M first transmission lines in a first branch step, Each of the M second branching sections outputs the uplink signal transmitted from each of the multiple termination devices to the second transmission line, and branches the downlink signal received from the second transmission line and transmits it to each of the multiple termination devices in a second branching step, Each of the M path switching units provided for each of the second branch units and connected to each of the M first branch units by the first transmission path performs a first transfer process based on the connection relationship between the second branch unit and the terminal station device, outputting the uplink signal received from the second branch unit via the second transmission path to the first branch unit corresponding to the terminal station device to which the second branch unit is connected, and a second transfer process that outputs the downlink signal received from each of the M first branch units via the first transmission path to the second branch unit corresponding to the terminal station device to which the second branch unit is connected, to the second transmission path to the second branch unit. Control steps include: the control unit determining the connection relationship between the second branch and the terminal devices based on the number of terminal devices housed in each of the terminal devices, the number of terminal devices that are running after the consolidation of destinations for multiple terminal devices, or the number of terminal devices whose destination terminal device is changed due to the consolidation of destinations for multiple terminal devices, controlling the route switching unit to perform the first transfer process and the second transfer process based on the determined connection relationship, and instructing the terminal devices that are determined not to be connected to any of the second branch to enter a sleep state; A communication method that includes [something].

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