Communication device and control method

Abstract

Provided is a communication device comprising: a plurality of line concentration devices with a plurality of ports connected to one or more higher-level networks; and a control unit that changes the state of connection between the one or more higher-level networks and the plurality of line concentration devices on the basis of information that affects the volume of communication between the one or more higher-level networks and the plurality of line concentration devices, and closes ports that have become unused due to the change in the state of connection from among the plurality of ports included in the plurality of line concentration devices.　

Description

Communication device and control method

[0001] The present invention relates to a communication device and a control method.

[0002] In conventional communication devices, a link aggregation group (LAG) is configured and connected in a network connection using a plurality of line concentrator switches (see, for example, Patent Document 1). For example, in the configuration shown in Patent Document 1, two line concentrator switch devices configure LAG #1 for upper network #1, LAG #2 for upper network #2, and LAG #M for upper network #M.

[0003] As a method of accommodating each ONU (Optical Network Unit) in a higher-level network, for example, allocation according to the service provided by each higher-level network or allocation according to the number of ONUs accommodated in each higher-level network can be mentioned. Allocation according to the service provided by each higher-level network is a method of accommodating ONUs that receive service A in higher-level network #1, and ONUs that receive service B in higher-level network #2.

[0004] The allocation according to the number of ONUs accommodated in each upper network is a method of accommodating, for example, the first to 500th ONUs in the order of contract for service A to upper network #1, the 501st to 1,000th ONUs in the order of contract for service A to upper network #2, and the 1,001st to 1,500th ONUs in the order of contract for service A to upper network #3.

[0005] JP 2017-123563 A

[0006] Communication traffic increases from daytime to night in response to human activity, and drops to less than half of its peak volume from late at night to early morning. Communication traffic has been increasing exponentially and is expected to continue to increase in the future. Therefore, the imbalance (difference) in communication traffic volume throughout the day is expected to further widen in the future. Communication devices are designed to meet the expected maximum traffic volume and future maximum demand. In this case, it is expected that during low-traffic times, such as late at night, traffic flow will be significantly lower than the designed bandwidth. Conventional technologies determine the allocation between the upper network and the line-concentrating switch device based on the services provided, the number of ONUs accommodated, etc., and the allocation settings are generally not changed during operation. Therefore, as mentioned above, there was a problem of excessive power consumption to maintain unnecessary connections (number of links) with the upper network, even during low-traffic times, such as late at night.

[0007] In view of the above circumstances, an object of the present invention is to provide a technology that can reduce power consumption in a communication device that includes a plurality of concentrators.

[0008] One aspect of the present invention is a communication device comprising: a plurality of concentrators each having a plurality of ports connected to one or more upstream networks; and a control unit that changes the connection state between the one or more upstream networks and the plurality of concentrators based on information that affects the amount of communication between the one or more upstream networks and the plurality of concentrators, and blocks any unused ports among the plurality of ports owned by the plurality of concentrators due to the change in connection state.

[0009] One aspect of the present invention is a control method that changes the connection state between one or more upper networks and multiple concentrators having multiple ports connected to the one or more upper networks based on information that affects the amount of communication between the one or more upper networks and the multiple concentrators, and blocks ports that have become unused among the multiple ports of the multiple concentrators due to the change in connection state.

[0010] According to the present invention, it is possible to reduce power consumption in a communication device that includes a plurality of concentrators.

[0011] FIG. 1 is a diagram illustrating an example of the configuration of an optical communication system in a first embodiment. FIG. 2 is a flowchart illustrating the processing flow of an OLT in the first embodiment. FIG. 3 is a sequence diagram illustrating the processing flow of an optical communication system in the first embodiment. FIG. 4 is a diagram illustrating an example of the configuration of an optical communication system in a second embodiment. FIG. 5 is a flowchart illustrating the processing flow of an OLT in the second embodiment. FIG. 6 is a flowchart illustrating the processing flow of an OLT in a third embodiment. FIG. 7 is a flowchart illustrating the processing flow of an OLT in a fourth embodiment. FIG. 8 is a flowchart illustrating the processing flow of a controller in a fifth embodiment. FIG. 9 is a sequence diagram illustrating the processing flow of an optical communication system in the fifth embodiment. FIG. 10 is a flowchart illustrating the processing flow of an OLT in a sixth embodiment. FIG. 11 is a flowchart illustrating the processing flow of an OLT in a seventh embodiment. FIG. 12 is a flowchart illustrating the processing flow of an OLT in an eighth embodiment.

[0012] An embodiment of the present invention will be described below with reference to the drawings. (First Embodiment) Fig. 1 is a diagram showing an example of the configuration of an optical communication system 100 in the first embodiment. The optical communication system 100 includes an OLT 10, an OLT operation unit 20, and a host NW operation unit 30. The OLT 10 is connected to the host NW operation unit 30 via the OLT operation unit 20.

[0013] The OLT 10 is an optical line termination device provided on the electric utility side that terminates optical signals. The OLT 10 accommodates one or more ONUs 50 via optical fibers and an optical splitter 40. For example, the OLT 10 accommodates one or more ONUs 50 via optical fibers and an optical splitter 40-1, and one or more ONUs 50 via an optical fiber and an optical splitter 40-K, where K is an integer equal to or greater than 2. The OLT 10 is one aspect of a communication device.

[0014] The OLT operation unit 20 manages the OLT 10. The OLT operation unit 20 transfers, for example, a control signal transmitted from the OLT 10 to the upper NW operation unit 30. The OLT operation unit 20 transfers, for example, a control signal transmitted from the upper NW operation unit 30 to the OLT 10. The OLT operation unit 20 is, for example, an EMS (Element Management System).

[0015] The upper NW operation unit 30 manages a plurality of upper NWs 60. The upper NW operation unit 30 transfers, for example, a control signal transmitted from the OLT operation unit 20 to an upper device 61 arranged in the upper NW 60. The upper NW operation unit 30 transfers, for example, a control signal transmitted from the upper device 61 to the OLT operation unit 20. The upper NW operation unit 30 is, for example, an EMS.

[0016] The optical splitter 40 connects the OLT 10 and each ONU 50. The optical splitter 40 splits an optical signal transmitted from the OLT 10 and transmits it to each ONU 50. The optical splitter 40 combines the optical signals transmitted from each ONU 50 and transmits it to the OLT 10.

[0017] The ONUs 50 are optical network units (ONUs) installed in user homes that terminate optical signals. One or more user terminals are connected to each ONU 50. The ONUs 50 transmit, for example, main signals transmitted from the user terminals to the OLT 10.

[0018] The upper NW 60 provides various services to the ONUs 50 connected to the OLT 10. At least one upper NW 60 is provided in each upper NW 60. The upper device 61 has a plurality of ports. The plurality of ports of the upper device 61 are connected to a plurality of first ports of the multiplexing unit 16.

[0019] [Specific Configuration of OLT 10] Next, a specific configuration of the OLT 10 will be described. The OLT 10 includes a plurality of PON interface units 11-1 to 11-K, a plurality of line concentrators 12-1 to 12-O, and an OLT control unit 13. Note that O is an integer equal to or greater than 2. Hereinafter, when there is no need to distinguish between the PON interface units 11-1 to 11-K, they will be referred to as PON interface units 11, and when there is no need to distinguish between the plurality of line concentrators 12-1 to 12-O, they will be referred to as line concentrators 12.

[0020] Each PON interface unit 11 is connected to a plurality of line concentrators 12-1 to 12-O. Furthermore, one or more ONUs 50 are connected to each PON interface unit 11 via optical fibers and optical splitters 40. For example, the PON interface unit 11-1 is connected to a plurality of line concentrators 12-1 to 12-O, and an ONU 50 is connected to each PON interface unit 11 via optical fibers and optical splitter 40-1. A plurality of ONUs 50 can be connected to each PON interface unit 11.

[0021] A main signal line for transmitting and receiving a main signal is provided between each PON interface unit 11 and each concentrator switch 12, and each PON interface unit 11 is connected to each concentrator switch 12 via the main signal line. For example, the PON interface unit 11-1 is connected to each concentrator switch 12 via the main signal line, and the PON interface unit 11-K is connected to each concentrator switch 12 via the main signal line.

[0022] Each concentrator switch 12 is connected to a plurality of upper NWs 60-1 to 60-L and a plurality of PON interface units 11-1 to 11-K. For example, the concentrator switch 12-1 is connected to a plurality of upper NWs 60-1 to 60-L and a plurality of PON interface units 11-1 to 11-K, and the concentrator switch 12-O is connected to a plurality of upper NWs 60-1 to 60-L and a plurality of PON interface units 11-1 to 11-K. Note that L is an integer equal to or greater than 2. The concentrator switch 12 is one aspect of a concentrator.

[0023] A main signal line for transmitting and receiving a main signal is provided between each concentrator switch 12 and each upper NW 60, and link aggregation is applied to the main signal lines between a plurality of concentrators 12 and one upper NW 60. For example, link aggregation LAG#1 is applied to the main signal lines between the concentrator switches 12-1 and 12-O and the upper NW 60-1, and link aggregation LAG#L is applied to the main signal lines between the concentrator switches 12-1 and 12-O and the upper NW 60-L.

[0024] In the following description, as an example, a case will be described in which link aggregation is applied to main signal lines between a plurality of line concentrators 12 and one upper NW 60, but link aggregation may not be applied to some connections. For example, link aggregation may be applied to main signal lines between the line concentrators 12-1 and 12-O and the upper NW 60-1, and link aggregation may not be applied to main signal lines between the line concentrators 12-1 and 12-O and the upper NW 60-L.

[0025] The OLT control unit 13 is connected to each PON interface unit 11, each line concentrator switch 12, and the OLT operation unit 20. In Fig. 1, paths between devices along which main signals are transmitted are indicated by solid lines, and paths between devices along which control signals are transmitted are indicated by dotted lines. The control signals include, for example, inquiries between devices, responses to inquiries, port sleep instructions, port sleep release instructions, or connection switching instructions.

[0026] The port sleep instruction is an instruction to put one of the multiple ports of the line concentrator 12 and one of the multiple ports of the higher-level device 61 arranged in the higher-level NW 60 into a sleep state. Putting a port into a sleep state means blocking the port and disabling its use, thereby halting transmission and reception functions. When the network interface of the line concentrator 12 has functions on a port-by-port basis, blocking the port also makes it possible to suspend the functions assigned to that port. This prevents the port from being used, thereby reducing power consumption.

[0027] The port sleep release instruction is an instruction to release one of the multiple ports of the concentrator switch 12 and one of the multiple ports of the higher-level device 61 arranged in the higher-level NW 60 from sleep mode. Releasing a port from sleep mode means opening the port and making functions related to transmission and reception available. If the network interface of the concentrator switch 12 has functions on a port-by-port basis, those functions are also used. This makes it possible to use unused ports.

[0028] The PON interface unit 11 relays signals between each concentrator switch 12 and the ONUs 50. The PON interface unit 11 includes a PON signal processor 14 and a PON controller 15. The PON signal processor 14 converts optical main signals transmitted from the ONUs 50 into electrical signals and outputs the signals to the concentrator switch 12 that serves as the output destination. Here, the concentrator switch 12 that serves as the output destination refers to the concentrator switch 12 that serves as the output destination of the signals transmitted from the ONUs 50.

[0029] The PON control unit 15 controls the operation of the PON interface unit 11. The PON control unit 15 performs link aggregation settings in accordance with the control of the OLT control unit 13, for example.

[0030] The concentrator switch 12 relays signals between each upper network 60 and each PON interface unit 11. The concentrator switch 12 includes a multiplexer 16 and a SW controller 17. The multiplexer 16 has a plurality of first ports and a plurality of second ports. The plurality of first ports are connected to ports of upper devices 61 arranged in each of the plurality of upper networks 60. The plurality of second ports are connected to a plurality of PON interface units 11. The multiplexer 16 outputs the input main signal to an output destination.

[0031] The SW control unit 17 controls the operation of the line concentrator switch 12. The SW control unit 17 controls, for example, the connection of a plurality of first ports and a plurality of second ports included in the multiplexing unit 16. For example, in response to an instruction from the OLT control unit 13, the SW control unit 17 puts a first port that is a sleep target among the plurality of first ports included in the multiplexing unit 16 into a sleep state. For example, in response to an instruction from the OLT control unit 13, the SW control unit 17 releases a first port that is a sleep release target among the plurality of first ports included in the multiplexing unit 16 from the sleep state.

[0032] The OLT control unit 13 controls the connection state between the upper network 60 and the plurality of concentrator switches 12 based on information that affects the amount of communication between the upper network 60 and the plurality of concentrator switches 12. Information that affects the amount of communication between the upper network 60 and the plurality of concentrator switches 12 is, for example, the amount of traffic flowing through the first port of the multiplexer 16 or the number of ONUs 50 accommodated in the upper network 60. The ONUs 50 accommodated in the upper network 60 are ONUs 50 that are connected to the OLT 10 and communicate with a higher-level device 61 arranged in the upper network 60 via the OLT 10.

[0033] The number of ONUs 50 accommodated in the upper NW 60 does not need to include inactive ONUs 50 (hereinafter referred to as "inactive ONUs") such as ONUs 50 that are not powered on (powered OFF) or ONUs 50 that are in a sleep state. This is because inactive ONUs do not generate communication and do not affect the amount of communication between the upper network 60 and the multiple concentrator switches 12. In the first embodiment, a configuration will be described in which the OLT control unit 13 controls the connection state between the upper NW 60 and the concentrator switches 12 in accordance with the amount of traffic flowing through the first port of the multiplexer 16.

[0034] The OLT control unit 13 acquires from each concentrator switch 12 information on the amount of traffic flowing through the first port of the multiplexer 16 of each concentrator switch 12. The OLT control unit 13 determines whether or not there is a port capable of sleeping based on the acquired traffic amount information. If the OLT control unit 13 determines that there is a port capable of sleeping, it generates a control signal including information specifying the port to be put into sleep mode. The OLT control unit 13 transmits the generated control signal to the concentrator switch 12 having the port to be put into sleep mode.

[0035] Furthermore, the OLT control unit 13 generates a control signal for putting into sleep the port of the higher-level device 61 arranged in the higher-level NW 60 that is connected to the port to be put into sleep in the OLT 10. This control signal includes information for identifying the port to be put into sleep in the OLT 10, information for identifying the line concentrator switch 12, and a sleep instruction. The OLT control unit 13 transmits the generated control signal to the OLT operation unit 20.

[0036] The control signal transmitted from the OLT control unit 13 to the OLT operation unit 20 is transferred from the OLT operation unit 20 to the upper NW operation unit 30. Based on the received control signal, the upper NW operation unit 30 puts a port to be put into sleep mode among the multiple ports of the upper device 61. The OLT control unit 13 may be configured by a processor such as a CPU (Central Processing Unit), or may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0037] In the above description, the OLT operation unit 20 and the upper NW operation unit 30 cooperate to put not only the line concentrator 12 but also the upper device 61 into sleep mode, but the above description is merely an example. In the present invention, only the port of the line concentrator 12 may be put into sleep mode. In this case, the OLT control unit 13 does not need to generate a control signal for putting the port of the upper device 61 arranged in the upper NW 60 into sleep mode.

[0038] 2 is a flowchart showing the processing flow of the OLT 10 in the first embodiment. When an ONU 50 is newly connected to the OLT 10 (step S101), the OLT control unit 13 detects the newly connected ONU 50. For example, the OLT control unit 13 detects which PON interface unit 11 the newly connected ONU 50 (hereinafter referred to as the "new ONU") is connected to based on a notification from the PON interface unit 11 to which the new ONU is connected. The OLT control unit 13 then determines the upstream NW 60 that will accommodate the detected new ONU (step S102).

[0039] The OLT 10 measures the traffic volume for each port of each concentrator switch 12 (step S103). Specifically, the SW control unit 17 of each concentrator switch 12 measures the traffic volume flowing through each first port of the multiplexer 16 (a port connected to a port of an upper-level device 61 arranged in each of the multiple upper-level NWs 60). The SW control unit 17 of each concentrator switch 12 outputs information on the measured traffic volume of each first port to the OLT control unit 13.

[0040] The OLT control unit 13 acquires information on the traffic volume of each first port output from the SW control unit 17 of each concentrator switch 12. This allows the OLT control unit 13 to grasp information on the traffic volume flowing through each first port of the multiplexing unit 16-1 of the concentrator switch 12-1 and information on the traffic volume flowing through each first port of the multiplexing unit 16-O of the concentrator switch 12-O.

[0041] The OLT control unit 13 determines whether there is a port whose traffic volume exceeds a threshold value X1 by referring to the acquired information on the traffic volume of each first port of the multiplexing unit 16 of each line concentrator switch 12 (step S104). The threshold value X1 is a value that serves as a reference when the traffic volume per port is large. For example, the threshold value X1 is set to a value that indicates that the traffic volume per port is large.

[0042] The value indicating a large amount of traffic flowing per port may be a value that can be determined as a generally large amount of traffic flowing per port based on experience, experiment, etc. The value indicating a large amount of traffic flowing per port is set in advance.

[0043] The OLT control unit 13 compares the traffic volume of each first port of the multiplexing unit 16 of each line concentrator 12 with the threshold X1 to determine whether there is a port whose traffic volume exceeds the threshold X1. If there is even one port whose traffic volume exceeds the threshold X1, the OLT control unit 13 determines that there is a port whose traffic volume exceeds the threshold X1. On the other hand, if there is no port whose traffic volume exceeds the threshold X1, the OLT control unit 13 determines that there is no port whose traffic volume exceeds the threshold X1.

[0044] If the OLT control unit 13 determines that there is no port whose traffic volume exceeds the threshold value X1 (step S104-NO), the OLT control unit 13 determines whether there is a port whose traffic volume is below the threshold value Y1 by referring to the acquired traffic volume information of each first port of the multiplexing unit 16 of each line concentrator switch 12 (step S105). The threshold value Y1 is a value that serves as a reference when the traffic volume per port is low. For example, the threshold value Y1 is set to a value that indicates that the traffic volume per port is low.

[0045] The value indicating that the amount of traffic flowing per port is small may be a value that can be determined as a generally small amount of traffic flowing per port based on experience, experiment, etc. The value indicating that the amount of traffic flowing per port is small is set in advance.

[0046] The OLT control unit 13 compares the acquired traffic volume of each first port of the multiplexing unit 16 of each line concentrator 12 with a threshold Y1 to determine whether there is a port whose traffic volume is below the threshold Y1. If there is even one port whose traffic volume is below the threshold Y1, the OLT control unit 13 determines that there is a port whose traffic volume is below the threshold Y1. On the other hand, if there is no port whose traffic volume is below the threshold Y1, the OLT control unit 13 determines that there is no port whose traffic volume is below the threshold Y1.

[0047] If the OLT control unit 13 determines that there is no port whose traffic volume is below the threshold Y1 (step S105-NO), the OLT control unit 13 puts unused ports of the line concentrator 12 into a sleep state (step S106). An unused port of the line concentrator 12 is a port that is not being used for communication.

[0048] The OLT control unit 13 puts the unused ports of the line concentrator switch 12 into a sleep state and then waits for a predetermined time (step S107). The OLT control unit 13 executes the process of step S103 after the predetermined time has elapsed. In the process of step S104, if the OLT control unit 13 determines that there is a port whose traffic volume exceeds the threshold X1 (step S104-YES), the OLT control unit 13 determines whether the number of upper-level NWs 60 in use is less than the maximum number N1 of upper-level NWs 60 (hereinafter referred to as the "maximum number of upper-level NWs N1") (step S108). In other words, the OLT control unit 13 determines whether the number of upper-level NWs 60 currently in use is less than the number of all upper-level NWs 60 assigned to the ONUs 50. The upper-level NWs 60 in use are, for example, upper-level NWs 60 that accommodate the ONUs 50.

[0049] If the OLT control unit 13 determines that the number of upper NWs 60 in use is not less than the maximum number N1 of upper NWs (step S108-NO), the OLT control unit 13 waits for a predetermined time (step S107). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S103.

[0050] On the other hand, if the OLT control unit 13 determines that the number of used upper NWs 60 is less than the maximum number N1 of upper NWs (step S108-YES), the OLT control unit 13 determines whether or not the traffic volume of each first port of the multiplexing unit 16 of each concentrator switch 12 can be reduced to a threshold value X1 or less by using unused upper NWs 60 (step S109). For example, the OLT control unit 13 determines whether or not the traffic volume of each first port of the multiplexing unit 16 of each concentrator switch 12 can be reduced to a threshold value X1 or less by averaging the traffic using unused upper NWs 60.

[0051] If the OLT control unit 13 determines that the traffic volume of each first port of the multiplexing unit 16 of each line concentrator 12 can be reduced to or below the threshold X1 using unused upstream NWs 60 (step S109—YES), the OLT control unit 13 reallocates the upstream NWs 60 so as to minimize the number of upstream NWs (step S110). For example, assuming that the sleeping ports are released from sleep, the OLT control unit 13 allocates the upstream NWs 60 so that the traffic volume at each port is reduced to or below a threshold (e.g., threshold X1 in FIG. 2 ) and the number of upstream NWs (the number of ports connected to the upstream NWs) is minimized when the traffic volume is proportionally distributed among the ports. Note that the method for reallocating the upstream NWs 60 is not limited to the method described here. Any method for reallocating the upstream NWs 60 may be used as long as the upstream NWs 60 can be reallocated so as to minimize the number of upstream NWs. While FIG. 2 has been used as an example, the same applies to the following description. In the following description, for the sake of understanding the invention, a configuration in which reallocation of the upper NW 60 is performed using the method described above will be described as an example.

[0052] Thereafter, the OLT control unit 13 releases the sleeping port (step S111). The OLT control unit 13 releases the sleep of the port that has become the target of use through reallocation, for example, among each first port of the multiplexing unit 16 of each concentrator 12. At this time, the OLT control unit 13 outputs a control signal including information for identifying the first port to be used and a sleep release instruction to the target concentrator 12. Here, the target concentrator 12 is the concentrator 12 that has the first port to be used.

[0053] The SW control unit 17 of the target line concentrator 12 acquires the control signal output from the OLT control unit 13. The SW control unit 17 releases the sleep state of the first port of the multiplexing unit 16, which is indicated by the information for identifying the first port included in the acquired control signal. As a result, the released first port becomes available for use.

[0054] Furthermore, the OLT control unit 13 releases the sleep mode of the port that has become the target of use through reallocation, for example, among the ports of the higher-level devices 61 arranged in each higher-level NW 60. At this time, the OLT control unit 13 transmits to the OLT operation unit 20 a control signal including information for identifying the port that is the target of use, information for identifying the higher-level device 61, and a sleep release instruction.

[0055] The OLT operation unit 20 receives a control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30. The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transfers the control signal to the upper device 61 identified based on information for identifying the upper device 61 included in the received control signal.

[0056] The upper device 61 receives the control signal transferred from the upper NW operation unit 30. The upper device 61 releases the sleep mode of the port indicated by the information for identifying the port included in the received control signal. This makes the released port available for use. Thereafter, the OLT control unit 13 waits for a predetermined time (step S107). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S103.

[0057] If the OLT control unit 13 determines that the traffic volume of each first port of the multiplexing unit 16 of each line concentrator 12 cannot be reduced to or below the threshold X1 using unused upper NWs 60 (step S109-NO), the OLT control unit 13 allocates the traffic volume proportionally using all upper NWs 60 (step S112). Thereafter, the OLT control unit 13 waits for a predetermined time (step S107). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S103.

[0058] In the process of step S105, if the OLT control unit 13 determines that there is a port whose traffic volume is below the threshold Y1 (step S105-YES), the OLT control unit 13 determines whether there are multiple upstream NWs 60 in use (step S113). If the OLT control unit 13 determines that there are not multiple upstream NWs in use (step S113-NO), the OLT control unit 13 puts the unused ports of the line concentrator 12 into a sleep state (step S114). After putting the unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S107). The OLT control unit 13 executes the process of step S103 after the predetermined time has elapsed.

[0059] On the other hand, if the OLT control unit 13 determines that there are multiple upstream NWs 60 in use (step S113—YES), the OLT control unit 13 determines whether the sum of the traffic volumes of the first port with the smallest traffic volume and the first port with the second smallest traffic volume exceeds the threshold X1 (step S115). If the OLT control unit 13 determines that the sum of the traffic volumes exceeds the threshold X1 (step S115—YES), the OLT control unit 13 puts the unused ports of the line concentrator 12 into a sleep state (step S106). After putting the unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S107).

[0060] On the other hand, if the OLT control unit 13 determines that the sum of the traffic volumes does not exceed the threshold X1 (step S115—NO), the OLT control unit 13 aggregates the upstream networks 60 (step S116). For example, the OLT control unit 13 aggregates the upstream networks 60 by shifting the ONUs 50 accommodated in the port with the smallest traffic volume to the port with the second smallest traffic volume. Note that the method for aggregating the upstream networks 60 is not limited to the method described here. Any method for aggregating the upstream networks 60 may be used as long as it can reduce the number of upstream networks 60 in use. While the description here uses FIG. 2 as an example, the aggregation of the upstream networks 60 applies similarly in the following description. Note that, for the sake of understanding the invention, the following description assumes that the upstream networks 60 are aggregated using the method described above. After aggregating the upstream networks 60, the OLT control unit 13 again determines whether there are multiple upstream networks 60 in use (step S113).

[0061] 2 shows a configuration in which a threshold is used to determine whether a port should be opened or closed (e.g., port sleep control and port wake-up control), but the criteria for determining whether a port should be opened or closed are not limited to this. Even with the same traffic, there may be an upward or downward trend. If traffic is showing an upward trend, it is likely that traffic will increase in the future, and if traffic is showing a downward trend, it is likely that traffic will decrease in the future. Therefore, the OLT control unit 13 may use not only a threshold as a factor for determining whether a port should be opened or closed, but also predict future trends based on past trends, and may determine whether a port should be opened or closed by taking the prediction results into account. In the present invention, a trend refers to traffic trends over a certain period of time.

[0062] As an example, even if the OLT control unit 13 determines in the processing of step S105 in Fig. 2 that there is a port whose traffic volume is below the threshold Y1, if the predicted future trend shows an upward trend, it is possible that traffic will increase in the future. Therefore, even if the OLT control unit 13 determines that there is a port whose traffic volume is below the threshold Y1, if the predicted future trend shows an upward trend, it may determine that there is no port whose traffic volume is below the threshold Y1. Note that this determination criterion may be set appropriately depending on the system.

[0063] 2 , even if the OLT control unit 13 determines that the traffic volume at each first port of the multiplexing unit 16 of each concentrator switch 12 cannot be reduced to or below the threshold X1 using an unused upper-level NW 60, if the predicted future trend indicates a downward trend, it is possible that the traffic volume will decrease in the future. In this case, it may be possible to reduce the traffic volume at each first port of the multiplexing unit 16 of each concentrator switch 12 to or below the threshold X1 using an unused upper-level NW 60. Therefore, even if the OLT control unit 13 determines that the traffic volume at each first port of the multiplexing unit 16 of each concentrator switch 12 cannot be reduced to or below the threshold X1 using an unused upper-level NW 60, if the predicted future trend indicates a downward trend, the excess over the threshold is temporary. Therefore, if a temporary traffic excess can be handled between an arbitrarily set threshold X1 and the upper traffic limit value of the port, the OLT control unit 13 may determine that the traffic volume of each first port of the multiplexing unit 16 of each line concentrator 12 can be kept below the threshold X1 by using an unused upper NW 60. Note that this determination criterion may be set appropriately depending on the system.

[0064] 3 is a sequence diagram showing the processing flow of the optical communication system 100 according to the first embodiment. The OLT control unit 13 inquires of each concentrator switch 12 about the number of upstream NWs 60 in use (step S121). The SW control unit 17 of each concentrator switch 12 responds to the inquiry from the OLT control unit 13 by reporting the number of upstream NWs 60 in use (step S122). The OLT control unit 13 then instructs each concentrator switch 12 to measure the traffic volume for each port of each concentrator switch 12 (step S123). In response to the instruction from the OLT control unit 13, the SW control unit 17 of each concentrator switch 12 measures the traffic volume flowing through each first port of the multiplexer 16. The SW control unit 17 of each concentrator switch 12 outputs the measured traffic volume information for each first port to the OLT control unit 13 as a response (step S124).

[0065] The OLT control unit 13 acquires information on the traffic volume of each first port output from the SW control unit 17 of each concentrator switch 12. The OLT control unit 13 considers changing the accommodation allocation of the upper network 60 based on the acquired information on the traffic volume of each first port of the multiplexing unit 16 of each concentrator switch 12 (step S125). Specific processing is as shown in FIG. 2 . If, as a result of the consideration, it becomes necessary to change the accommodation allocation of the upper network 60, the OLT control unit 13 checks with the upper network operation unit 30 whether the allocation of the upper network 60 can be changed.

[0066] For example, the OLT control unit 13 generates a control signal including an inquiry for confirming whether or not it is possible to change the allocation of the upper NW 60. The OLT control unit 13 transmits the generated control signal to the OLT operation unit 20 (step S126). The OLT operation unit 20 receives the control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30 (step S127).

[0067] The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 determines whether the allocation of the upper NW 60 can be changed based on the inquiry content included in the received control signal. Here, it is assumed that the upper NW operation unit 30 determines that the allocation of the upper NW 60 can be changed. In this case, the upper NW operation unit 30 generates a control signal including a response indicating that the allocation of the upper NW 60 can be changed. The upper NW operation unit 30 transmits the generated control signal to the OLT operation unit 20 (step S128).

[0068] The OLT operation unit 20 receives the control signal transmitted from the upper NW operation unit 30. The OLT operation unit 20 transfers the received control signal to the OLT 10 (step S129). The OLT control unit 13 receives the control signal transferred from the OLT operation unit 20. Based on the response included in the received control signal, the OLT control unit 13 determines that the allocation of the upper NW 60 can be changed. The OLT control unit 13 controls the allocation of the upper NW 60 in accordance with the result of the review of the processing in step S125 (step S130).

[0069] Thereafter, in accordance with the allocation control of the upper NW 60, the OLT control unit 13 puts the port of the upper device 61 of the upper NW 60 into a sleep state, or releases the sleep state of the port of the upper device 61. Furthermore, in accordance with the allocation control of the upper NW 60, the OLT control unit 13 puts the first port of the multiplexing unit 16 of the line concentrator 12 into a sleep state, or releases the sleep state of the first port of the multiplexing unit 16 of the line concentrator 12.

[0070] For example, when it is determined in the processing of step S113 that there are no multiple upstream NWs 60 in use, or when it is determined in the processing of step S115 that the sum of the traffic volumes exceeds the threshold X1, the OLT control unit 13 puts the port of the upstream device 61 of the upstream NW 60 and the first port of the multiplexing unit 16 of the line concentrator 12 into a sleep state. For example, after the processing of step S110, the OLT control unit 13 releases the sleep state of the port of the upstream device 61 of the upstream NW 60 and the first port of the multiplexing unit 16 of the line concentrator 12.

[0071] The OLT control unit 13 generates a control signal including a sleep instruction when putting a port of the upper device 61 of the upper NW 60 into a sleep state. On the other hand, the OLT control unit 13 generates a control signal including a sleep release instruction when releasing the sleep state of the port of the upper device 61 of the upper NW 60. The OLT control unit 13 transmits the generated control signal to the OLT operation unit 20 (step S131). The OLT operation unit 20 receives the control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30 (step S132).

[0072] The OLT control unit 13 generates a control signal including a sleep instruction when putting the first port of the multiplexing unit 16 of the line concentrator 12 into a sleep state. On the other hand, the OLT control unit 13 generates a control signal including a sleep cancellation instruction when releasing the sleep state of the first port of the multiplexing unit 16 of the line concentrator 12. The OLT control unit 13 outputs the generated control signal to the target line concentrator 12 (step S133).

[0073] The SW control unit 17 of the line concentrator 12 receives the control signal output from the OLT control unit 13. The SW control unit 17 puts the first port of the multiplexing unit 16 into a sleep state or releases the sleep state of the first port in accordance with the instruction included in the received control signal. When the SW control unit 17 completes the processing according to the instruction, it notifies the OLT control unit 13 that the processing has been completed (step S134).

[0074] The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transmits the received control signal to the upper device 61 of the target upper NW 60 (step S135). The upper device 61 receives the control signal transmitted from the upper NW operation unit 30. The upper device 61 puts the port into a sleep state or releases the port from sleep mode in accordance with the instruction contained in the received control signal.

[0075] When the upper level device 61 completes the processing in accordance with the instruction, it transmits a control signal indicating the completion of the processing to the upper level NW operation unit 30 (step S136). The upper level NW operation unit 30 receives the control signal transmitted from the upper level device 61. The upper level NW operation unit 30 transfers the received control signal to the OLT operation unit 20 (step S137). The OLT operation unit 20 transmits the control signal transferred from the upper level NW operation unit 30 to the OLT 10 (step S138).

[0076] The OLT control unit 13 receives the notification output from the SW control unit 17 and the control signal transmitted from the OLT operation unit 20. This completes the change of the accommodation allocation of the upper NW 60.

[0077] Conventionally, when a new ONU 50 is connected to the OLT 10, the OLT 10 sets the upstream NW 60 that will accommodate the new ONU 50. This upstream NW 60 remains unchanged unless the location of the upstream NW 60 is actively changed. Therefore, once the OLT 10 has set and activated the port of the line concentrator switch 12 for the upstream NW 60, it always operates even when traffic volume is low. Even during low-traffic times, such as at night, the port operates in the same way as it does during the daytime when traffic volume is high, resulting in poor power efficiency.

[0078] In contrast, according to the optical communication system 100 of the first embodiment, the allocation of the upper NWs 60 is changed according to the amount of traffic flowing through the concentrator switch 12. Specifically, the allocation of the upper NWs 60 is changed so as to reduce the number of upper NWs 60. By aggregating the upper NWs 60 in this way, the ports of the upper devices 61 and the ports of the concentrator switch 12 arranged in the upper NWs 60 that are not used for communication can be put into a sleep state without affecting communication. As a result, it is possible to reduce power consumption.

[0079] Second Embodiment In the first embodiment, the OLT aggregates the upstream NWs 60 by changing the allocation of multiple upstream NWs according to the amount of traffic flowing through each concentrator switch. The OLT then puts the ports of the upstream devices 61 and the concentrator switches located in the upstream NWs that are not used for communication into a sleep state. In contrast, in the second embodiment, a configuration for reducing power consumption when there is only one upstream NW will be described.

[0080] 4 is a diagram showing an example of the configuration of an optical communication system 100a according to the second embodiment. The optical communication system 100 includes an OLT 10, an OLT operation unit 20, and a host NW operation unit 30. The OLT 10 is connected to the host NW operation unit 30 via the OLT operation unit 20.

[0081] 4, the upper NW operation unit 30 manages one upper NW 60. The upper NW operation unit 30 transfers a control signal transmitted from, for example, the OLT operation unit 20 to an upper device 61 arranged in the upper NW 60. The upper NW operation unit 30 transfers a control signal transmitted from, for example, the upper device 61 arranged in the upper NW 60 to the OLT operation unit 20. The upper NW operation unit 30 is, for example, an EMS.

[0082] Even when there is only one upper NW 60, there are connections between the upper NW 60 and each concentrator switch 12 via multiple link aggregations. The OLT 10 in the second embodiment measures the traffic volume for each LAG port of the concentrator switch 12 and rearranges the link aggregations based on the measured traffic volume for each LAG port. For example, the OLT 10 reallocates the link aggregations to minimize the number of ports in use. A LAG port is a port in which multiple first ports are logically considered as a single path through link aggregation. This allows ports that constitute unnecessary link aggregations to go to sleep. As a result, power consumption can be reduced.

[0083] 5 is a flowchart showing the processing flow of the OLT 10 in the second embodiment. When an ONU 50 is newly connected to the OLT 10 (step S201), the OLT control unit 13 detects the newly connected ONU 50. For example, the OLT control unit 13 detects which PON interface unit 11 the new ONU is connected to based on a notification from the PON interface unit 11 to which the new ONU is connected. The OLT control unit 13 then determines the upstream NW 60 that will accommodate the detected new ONU (step S202). Here, it is assumed that the OLT control unit 13 assigns one upstream NW 60 to the new ONU.

[0084] Thereafter, the OLT control unit 13 determines the LAG port that will accommodate the new ONU (step S203). The OLT control unit 13 measures the traffic volume for each LAG port of each concentrator switch 12 (step S204). Specifically, the SW control unit 17 of each concentrator switch 12 measures the traffic volume flowing through each first port of the multiplexer 16 (a port connected to a port of the upper device 61 arranged in each of the multiple upper NWs 60).

[0085] The SW control unit 17 of each concentrator switch 12 outputs information on the measured traffic volume of each first port to the OLT control unit 13. The OLT control unit 13 acquires the information on the traffic volume of each first port output from the SW control unit 17 of each concentrator switch 12. The OLT control unit 13 calculates the traffic volume for each LAG port using the acquired information on the traffic volume of each first port. For example, the OLT control unit 13 calculates the traffic volume for each LAG port of each concentrator switch 12 by adding up the traffic volumes of multiple first ports that are considered to be in the same group by link aggregation. This allows the OLT control unit 13 to grasp the information on the traffic volume for each LAG port of each concentrator switch 12.

[0086] The OLT control unit 13 determines whether there is a LAG port whose traffic volume exceeds the threshold X1 by referring to the acquired traffic volume information for each LAG port of each concentrator switch 12 (step S205). The OLT control unit 13 determines whether there is a LAG port whose traffic volume exceeds the threshold X1 by comparing each traffic volume for each LAG port of each concentrator switch 12 with the threshold X1. If there is even one LAG port whose traffic volume exceeds the threshold X1, the OLT control unit 13 determines that there is a LAG port whose traffic volume exceeds the threshold X1. On the other hand, if there is no LAG port whose traffic volume exceeds the threshold X1, the OLT control unit 13 determines that there is no LAG port whose traffic volume exceeds the threshold X1.

[0087] If the OLT control unit 13 determines that there is no LAG port whose traffic volume exceeds the threshold value X1 (step S205-NO), the OLT control unit 13 determines whether there is a LAG port whose traffic volume is below the threshold value Y1 (step S206) by referring to the acquired traffic volume information for each LAG port of each concentrator switch 12. The OLT control unit 13 determines whether there is a LAG port whose traffic volume is below the threshold value Y1 by comparing each traffic volume for each LAG port of each concentrator switch 12 with the threshold value Y1.

[0088] If there is even one LAG port whose traffic volume is below the threshold Y1, the OLT control unit 13 determines that there is a LAG port whose traffic volume is below the threshold Y1. On the other hand, if there is no LAG port whose traffic volume is below the threshold Y1, the OLT control unit 13 determines that there is no LAG port whose traffic volume is below the threshold Y1.

[0089] If the OLT control unit 13 determines that there is no LAG port whose traffic volume is below the threshold Y1 (step S206-NO), the OLT control unit 13 puts unused ports of the line concentrator 12 into a sleep state (step S207). After putting unused ports of the line concentrator into a sleep state, the OLT control unit 13 waits for a predetermined time (step S208). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S204.

[0090] In the process of step S205, if the OLT control unit 13 determines that there is a LAG port whose traffic volume exceeds the threshold X1 (step S205-YES), the OLT control unit 13 determines whether the number of LAG ports in use is less than the total number N2 of LAGs for the upper network (step S209). That is, the OLT control unit 13 determines whether the number of LAG ports currently in use is less than the number of all LAGs for the upper network. Here, the total number of LAGs for the upper network represents the total number of link aggregations applied between the OLT 10 and one upper network 60.

[0091] If the OLT control unit 13 determines that the number of LAG ports in use is not less than the total number N2 of LAGs for the upper network (step S209-NO), the OLT control unit 13 waits for a predetermined time (step S208). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S204.

[0092] On the other hand, if the OLT control unit 13 determines that the number of LAG ports in use is less than the total number N2 of LAGs for the upper network (step S209—YES), the OLT control unit 13 determines whether or not the traffic volume of each LAG port can be reduced to a threshold value X1 or less by using an unused port (step S210). For example, the OLT control unit 13 determines whether or not the traffic volume of each LAG port can be reduced to a threshold value X1 or less by averaging the traffic using the unused first port.

[0093] If the OLT control unit 13 determines that the traffic volume of each LAG port can be reduced to or below the threshold X1 using the unused first port (step S210—YES), the OLT control unit 13 reallocates the LAGs so as to minimize the number of ports in use (step S211). For example, assuming that the sleeping port will be released from sleep, the OLT control unit 13 apportions the traffic volume among the ports and allocates the LAGs so that the traffic volume at each port is reduced to or below a threshold (e.g., threshold X1 in FIG. 5 ) and the number of upper NWs (the number of ports connected to the upper NWs) is minimized. Note that the method of LAG reallocation is not limited to the method described here. LAG reallocation may be performed in any manner as long as it minimizes the number of upper NWs. While FIG. 5 has been used as an example, the following description of LAG reallocation applies similarly. Note that, for the purposes of understanding the invention, the LAG reallocation is assumed to be performed using the method described above. Thereafter, the OLT control unit 13 releases the sleeping port (step S212).

[0094] The OLT control unit 13 cancels the sleep mode of a port that has become the target of use through reallocation, for example, among each first port of the multiplexing unit 16 of each line concentrator 12. At this time, the OLT control unit 13 outputs a control signal including information for identifying the first port that is the target of use and a sleep cancellation instruction to the target line concentrator 12.

[0095] The SW control unit 17 of the target line concentrator 12 acquires the control signal output from the OLT control unit 13. The SW control unit 17 releases the sleep state of the first port of the multiplexing unit 16, which is indicated by the information for identifying the first port included in the acquired control signal. As a result, the released first port becomes available for use.

[0096] Furthermore, the OLT control unit 13 releases the sleep mode of the port that has become the target of use through reallocation, for example, among the ports of the higher-level devices 61 arranged in each higher-level NW 60. At this time, the OLT control unit 13 transmits to the OLT operation unit 20 a control signal including information for identifying the port that is the target of use, information for identifying the higher-level device 61, and a sleep release instruction.

[0097] The OLT operation unit 20 receives a control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30. The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transfers the control signal to the upper device 61 identified based on information for identifying the upper device 61 included in the received control signal.

[0098] The upper device 61 receives the control signal transferred from the upper NW operation unit 30. The upper device 61 releases the sleep mode of the port indicated by the information for identifying the port included in the received control signal. This makes the released port available for use. Thereafter, the OLT control unit 13 waits for a predetermined time (step S208). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S204.

[0099] If the OLT control unit 13 determines that the traffic volume of each LAG port cannot be reduced to or below the threshold X1 using unused first ports (step S210-NO), the OLT control unit 13 uses all first ports to proportionally allocate the traffic volume (step S213). Thereafter, the OLT control unit 13 waits for a predetermined time (step S208). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S204.

[0100] In the process of step S206, if the OLT control unit 13 determines that there is a LAG port whose traffic volume is below the threshold Y1 (step S206—YES), the OLT control unit 13 determines whether there are multiple LAG ports in use (step S214). If the OLT control unit 13 determines that there are not multiple LAG ports in use (step S214—NO), the OLT control unit 13 puts the unused ports of the line concentrator 12 into a sleep state (step S215). After putting the unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S208). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S204.

[0101] On the other hand, if the OLT control unit 13 determines that there are multiple LAG ports in use (step S214—YES), the OLT control unit 13 determines whether the sum of the traffic volumes of the port with the smallest traffic volume and the port with the second smallest traffic volume exceeds threshold X1 (step S216). If the OLT control unit 13 determines that the sum of the traffic volumes exceeds threshold X1 (step S216—YES), the OLT control unit 13 puts unused ports of the line concentrator 12 into a sleep state (step S207). After putting unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S208).

[0102] If the OLT control unit 13 determines that the sum of the traffic volumes does not exceed the threshold X1 (step S216—NO), the OLT control unit 13 aggregates the LAG ports (step S217). For example, the OLT control unit 13 aggregates the LAG ports by shifting the ONUs 50 accommodated in the port with the smallest traffic volume to the port with the second smallest traffic volume. Note that the method for aggregating the LAG ports is not limited to the method described here. Any method may be used to aggregate the LAG ports so as to reduce the number of LAG ports. While the example shown in FIG. 5 is used here, the same applies to the following description. Note that, for the sake of understanding the invention, the LAG ports are aggregated using the method described above. After aggregating the LAG ports, the OLT control unit 13 again determines whether there are multiple LAG ports in use (step S214).

[0103] 5 shows a configuration in which a threshold is used to determine whether a port should be opened or closed (for example, port sleep control and port wake-up control), but the criteria for determining whether a port should be opened or closed are not limited to this. Even with the same traffic, there may be an upward or downward trend. If the traffic is showing an upward trend, it is likely that the traffic will increase in the future, and if the traffic is showing a downward trend, it is likely that the traffic will decrease in the future. Therefore, the OLT control unit 13 may use not only a threshold as a factor for determining whether a port should be opened or closed, but also predict a future trend based on past trends, and take the prediction result into account when determining whether to open or close a port.

[0104] As an example, even if the OLT control unit 13 determines in the processing of step S206 in Fig. 5 that there is a LAG port whose traffic volume is below the threshold Y1, if the predicted future trend shows an upward trend, it is possible that traffic will increase in the future. Therefore, even if the OLT control unit 13 determines that there is a LAG port whose traffic volume is below the threshold Y1, if the predicted future trend shows an upward trend, it may determine that there is no port whose traffic volume is below the threshold Y1. Note that this determination criterion may be set appropriately depending on the system.

[0105] As an example, even if the OLT control unit 13 determines in the processing of step S210 of FIG. 5 that the traffic volume of each LAG port cannot be reduced to or below the threshold X1 using an unused first port, if the predicted future trend shows a downward trend, it is possible that traffic will decrease in the future. In this case, it may be possible to reduce the traffic volume of each LAG port to or below the threshold X1 using an unused first port. Therefore, even if the OLT control unit 13 determines that the traffic volume of each LAG port cannot be reduced to or below the threshold X1 using an unused first port, it may also determine that the traffic volume of each LAG port can be reduced to or below the threshold X1 using an unused first port if the predicted future trend shows a downward trend. Note that this determination criterion may be set appropriately depending on the system.

[0106] According to the optical communication system 100a of the second embodiment configured as described above, even when there is only one upper NW 60, it is possible to obtain the same effects as in the first embodiment. Specifically, in the optical communication system 100a, the link aggregation allocation is changed according to the amount of traffic flowing through the concentrator switch 12. For example, in the optical communication system 100a, the link aggregation allocation is changed so as to reduce the number of ports used. This makes it possible to put the ports of the upper device 61 and the ports of the concentrator switch 12 that configure unnecessary link aggregations into a sleep state. As a result, it is possible to reduce power consumption.

[0107] In the first embodiment, the OLT changes the allocation of the upper NW by comparing the traffic volume of each port of each concentrator switch with a threshold. In contrast, in the third embodiment, a configuration will be described in which the OLT changes the allocation of the upper NW based on the total traffic volume, which is the sum of the traffic volumes of all ports of each concentrator switch.

[0108] Since the system configuration in the third embodiment is the same as that in the first embodiment, a description of each device will be omitted. In the third embodiment, the processing performed by the OLT 10 differs from that in the first embodiment. Specifically, the OLT 10 calculates a total traffic volume Z, which is the sum of the traffic volumes of all ports of each concentrator switch 12. The OLT 10 compares the result of dividing the calculated total traffic volume Z by the maximum number N1 of upper-level networks with a threshold value X2. The threshold value X2 is a value for determining the traffic volume flowing per port. An arbitrary value is set for the threshold value X2.

[0109] If the division result is equal to or less than the threshold X2 as a result of the comparison, the OLT 10 allocates the upper NW 60 so that the traffic volume per port becomes equal to the threshold X2. The fact that the division result is equal to or less than the threshold X2 means that the traffic volume per port can be increased. Therefore, if the division result is equal to or less than the threshold X2, the OLT 10 reallocates the upper NW 60 to each port so that the traffic volume per port approaches the threshold X2. This reduces the number of ports used.

[0110] On the other hand, if the result of the comparison shows that the division result is not equal to or less than the threshold value X2, the OLT 10 releases the sleep state of the unused ports. If the division result is not equal to or less than the threshold value X2, this means that the traffic volume per port is high and that the traffic volume per port needs to be reduced. Therefore, if the division result is not equal to or less than the threshold value X2, the OLT 10 releases the sleep state of the unused ports, making them usable, and controls the traffic volume per port to be reduced.

[0111] Fig. 6 is a flowchart showing the flow of processing in the OLT 10 in the third embodiment. In Fig. 6, the same processes as those in Fig. 2 are denoted by the same reference numerals as those in Fig. 2, and the description thereof will be omitted.

[0112] When the processes from step S101 to step S103 are completed, the OLT control unit 13 calculates the total traffic volume Z of all ports by adding up the acquired traffic volumes of each first port of the multiplexing unit 16 of each line concentrator 12 (step S301). Based on the calculated total traffic volume Z, the maximum number N1 of upper NWs, and the threshold X2, the OLT control unit 13 determines whether the result of dividing the total traffic volume Z by the maximum number N1 of upper NWs is equal to or less than the threshold X2 (step S302).

[0113] If the OLT control unit 13 determines that the division result is equal to or less than the threshold value X2 (step S302-YES), the OLT control unit 13 allocates the upper NWs 60 so that the traffic volume per port becomes the threshold value X2 (step S303). At this time, the OLT control unit 13 allocates the upper NWs 60 so that the traffic volume per port becomes as close to the threshold value X2 as possible, and reduces the number of first ports to be used.

[0114] Thereafter, the OLT control unit 13 puts the unused ports of the line concentrator 12 into a sleep state (step S304). After putting the unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S305). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S103.

[0115] In the process of step S302, if the OLT control unit 13 determines that the division result is not equal to or less than the threshold value X2 (step S302-NO), the OLT control unit 13 cancels the sleep of the unused ports (step S306). The OLT control unit 13 cancels the sleep of the unused ports, for example, among the first ports of the multiplexing units 16 of each concentrator switch 12. At this time, the OLT control unit 13 outputs a control signal including information for identifying the unused port and a sleep cancellation instruction to the target concentrator switch 12.

[0116] The SW control unit 17 of the target line concentrator 12 receives a control signal output from the OLT control unit 13. The SW control unit 17 releases the sleep mode of the first port of the multiplexing unit 16, which is indicated by the information for identifying the first port included in the received control signal. This makes the released first port available for use. Furthermore, the OLT control unit 13 releases the sleep mode of unused ports, for example, among the ports of the higher-level devices 61 arranged in each higher-level NW 60. At this time, the OLT control unit 13 transmits a control signal to the OLT operation unit 20, which includes information for identifying the port to be used, information for identifying the higher-level device 61, and a sleep release instruction.

[0117] The OLT operation unit 20 receives a control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30. The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transfers the control signal to the upper device 61 identified based on information for identifying the upper device 61 included in the received control signal.

[0118] The host device 61 receives the control signal transferred from the host NW operation unit 30. The host device 61 releases the sleep state of the port indicated by the information for identifying the port included in the received control signal. This makes the released port available for use.

[0119] Thereafter, the OLT control unit 13 distributes the traffic volume proportionally among all the upper NWs 60 (step S307). The OLT control unit 13 waits for a predetermined time (step S305). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S103.

[0120] 6 shows a configuration in which a threshold is used to determine whether a port should be opened or closed (for example, port sleep control and port wake-up control), but the criteria for determining whether a port should be opened or closed are not limited to this. Even with the same traffic, there may be an upward or downward trend. If the traffic is showing an upward trend, it is likely that the traffic will increase in the future, and if the traffic is showing a downward trend, it is likely that the traffic will decrease in the future. Therefore, the OLT control unit 13 may use not only a threshold as a factor for determining whether a port should be opened or closed, but also predict a future trend based on past trends, and take the prediction result into account when determining whether to open or close a port.

[0121] As an example, in the processing of step S302 in Fig. 6, even if the OLT control unit 13 determines that the result of dividing the total traffic volume Z by the maximum number N1 of top networks is equal to or less than the threshold value X2, if the predicted future trend shows an upward trend, it is possible that traffic will increase in the future. Therefore, even if the OLT control unit 13 determines that the result of dividing the total traffic volume Z by the maximum number N1 of top networks is equal to or less than the threshold value X2, if the predicted future trend shows an upward trend, it may determine that the result of dividing the total traffic volume Z by the maximum number N1 of top networks is not equal to or less than the threshold value X2. Note that this determination criterion may be set appropriately depending on the system.

[0122] As an example, even if the OLT control unit 13 determines in the processing of step S302 in FIG. 6 that the result of dividing the total traffic volume Z by the maximum number N1 of top networks is not equal to or less than the threshold value X2, if the predicted result of the future trend is a downward trend, it is possible that the traffic will decrease in the future. Therefore, even if the OLT control unit 13 determines that the result of dividing the total traffic volume Z by the maximum number N1 of top networks is not equal to or less than the threshold value X2, if the predicted result of the future trend is a downward trend, it may determine that the result of dividing the total traffic volume Z by the maximum number N1 of top networks is equal to or less than the threshold value X2. Note that this determination criterion may be set appropriately depending on the system.

[0123] The optical communication system 100 of the third embodiment configured as described above can achieve the same effects as those of the first embodiment. In the first embodiment, the traffic volume of each first port (port connected to the upper device 61 of the upper network 60) of the multiplexing unit 16 of each concentrator switch 12 is compared with the threshold X1. In contrast, the optical communication system 100 of the third embodiment compares the total traffic volume Z, which is the sum of the traffic volumes of each first port of the multiplexing unit 16 of each concentrator switch 12, divided by the maximum number N1 of upper network networks, with the threshold X2. The optical communication system 100 of the third embodiment then allocates the upper network 60 based on the total traffic volume Z so as to enable operation with the minimum number of ports. By aggregating the upper network 60 in this manner, ports of the upper network devices 61 and ports of the concentrator switch 12 that are not used for communication can be put into a sleep state without affecting communication. As a result, power consumption can be reduced.

[0124] In the second embodiment, the OLT changes the link aggregation allocation by comparing the traffic volume of each LAG port with a threshold. In contrast, in the fourth embodiment, a configuration will be described in which the OLT changes the link aggregation allocation based on the total traffic volume, which is the sum of the traffic volumes of each LAG port.

[0125] Since the system configuration in the fourth embodiment is the same as that in the second embodiment, a description of each device will be omitted. In the fourth embodiment, the processing performed by the OLT 10 differs from that in the second embodiment. Specifically, the OLT 10 calculates a total traffic volume Z, which is the sum of the traffic volumes of each LAG port. The OLT 10 divides the calculated total traffic volume Z by the total number N2 of LAGs for the upper network, and compares the result with a threshold X2.

[0126] If the division result is equal to or less than the threshold value X2 as a result of the comparison, the OLT 10 allocates link aggregations so that the traffic volume per port becomes equal to the threshold value X2. The fact that the division result is equal to or less than the threshold value X2 means that the traffic volume per port can be increased. Therefore, if the division result is equal to or less than the threshold value X2, the OLT 10 reallocates link aggregations so that the traffic volume per port approaches the threshold value X2. This reduces the number of ports used.

[0127] On the other hand, if the result of the comparison shows that the division result is not equal to or less than the threshold value X2, the OLT 10 releases the sleep state of the unused ports. If the division result is not equal to or less than the threshold value X2, this means that the traffic volume per port is high and that the traffic volume per port needs to be reduced. Therefore, if the division result is not equal to or less than the threshold value X2, the OLT 10 releases the sleep state of the unused ports, making them usable, and controls the traffic volume per port to be reduced.

[0128] 7 is a flowchart showing the flow of processing by the OLT 10 in the fourth embodiment. In FIG. 7, the same processes as those in FIG. 5 are denoted by the same reference numerals as those in FIG. 5, and the description thereof will be omitted.

[0129] When the processes from step S201 to step S204 are completed, the OLT control unit 13 calculates the total traffic volume Z of all LAG ports by adding up the calculated traffic volumes for each LAG port of each concentrator switch 12 (step S401). Then, based on the total traffic volume Z, the total number N2 of LAGs for the upper network, and the threshold X2, the OLT control unit 13 determines whether the result of dividing the total traffic volume Z by the total number N2 of LAGs for the upper network is equal to or less than the threshold X2 (step S402).

[0130] If the OLT control unit 13 determines that the division result is equal to or less than the threshold value X2 (step S402-YES), the OLT control unit 13 allocates the upper NWs 60 so that the traffic volume per port becomes the threshold value X2 (step S403). At this time, the OLT control unit 13 allocates the upper NWs 60 so that the traffic volume per port becomes as close to the threshold value X2 as possible, and reduces the number of first ports to be used.

[0131] Thereafter, the OLT control unit 13 puts the unused ports of the line concentrator 12 into a sleep state (step S404). After putting the unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S404). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S204.

[0132] In the process of step S402, if the OLT control unit 13 determines that the division result is not equal to or less than the threshold value X2 (step S402-NO), the OLT control unit 13 cancels the sleep of the unused ports (step S406). The OLT control unit 13 cancels the sleep of the unused ports, for example, among the first ports of the multiplexing units 16 of each concentrator switch 12. At this time, the OLT control unit 13 outputs a control signal including information for identifying the unused port and a sleep cancellation instruction to the target concentrator switch 12.

[0133] The SW control unit 17 of the target line concentrator 12 receives a control signal output from the OLT control unit 13. The SW control unit 17 releases the sleep mode of the first port of the multiplexing unit 16, which is indicated by the information for identifying the first port included in the received control signal. This makes the released first port available for use. Furthermore, the OLT control unit 13 releases the sleep mode of unused ports, for example, among the ports of the higher-level devices 61 arranged in each higher-level NW 60. At this time, the OLT control unit 13 transmits a control signal to the OLT operation unit 20, which includes information for identifying the port to be used, information for identifying the higher-level device 61, and a sleep release instruction.

[0134] The OLT operation unit 20 receives a control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30. The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transfers the control signal to the upper device 61 identified based on information for identifying the upper device 61 included in the received control signal.

[0135] The host device 61 receives the control signal transferred from the host NW operation unit 30. The host device 61 releases the sleep state of the port indicated by the information for identifying the port included in the received control signal. This makes the released port available for use.

[0136] Thereafter, the OLT control unit 13 distributes the traffic volume proportionally among all the first ports (step S407). The OLT control unit 13 waits for a predetermined time (step S405). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S204.

[0137] 7 shows a configuration in which a threshold is used to determine whether a port should be opened or closed (for example, port sleep control and port wake-up control), but the criteria for determining whether a port should be opened or closed are not limited to this. Even with the same traffic, there may be an upward or downward trend. If traffic is showing an upward trend, it is likely that traffic will increase in the future, and if traffic is showing a downward trend, it is likely that traffic will decrease in the future. Therefore, the OLT control unit 13 may use not only a threshold as a factor for determining whether a port should be opened or closed, but also predict future trends based on past trends, and take the prediction results into account when determining whether to open or close a port.

[0138] As an example, in the processing of step S402 in FIG. 7 , even if the OLT control unit 13 determines that the result of dividing the total traffic volume Z by the total number N2 of LAGs for the upper network is equal to or less than the threshold X2, if the predicted future trend shows an upward trend, it is possible that traffic will increase in the future. Therefore, even if the OLT control unit 13 determines that the result of dividing the total traffic volume Z by the total number N2 of LAGs for the upper network is equal to or less than the threshold X2, if the predicted future trend shows an upward trend, it may determine that the result of dividing the total traffic volume Z by the total number N2 of LAGs for the upper network is not equal to or less than the threshold X2. Note that this determination criterion may be set appropriately depending on the system.

[0139] As an example, even if the OLT control unit 13 determines in the processing of step S402 in FIG. 7 that the result of dividing the total traffic volume Z by the total number N2 of LAGs for the upper network is not equal to or less than the threshold X2, if the predicted result of the future trend is a downward trend, it is possible that the traffic will decrease in the future. Therefore, even if the OLT control unit 13 determines that the result of dividing the total traffic volume Z by the total number N2 of LAGs for the upper network is not equal to or less than the threshold X2, if the predicted result of the future trend is a downward trend, it may determine that the result of dividing the total traffic volume Z by the total number N2 of LAGs for the upper network is equal to or less than the threshold X2. Note that this determination criterion may be set appropriately depending on the system.

[0140] The optical communication system 100a of the fourth embodiment configured as described above can achieve the same effects as those of the second embodiment. In the second embodiment, the traffic volume for each LAG port of each concentrator switch 12 was compared with the threshold value X1. In contrast, the optical communication system 100a of the fourth embodiment compares the total traffic volume Z, which is the sum of the traffic volumes for each LAG port of each concentrator switch 12, divided by the total number of LAGs N2 for the upstream network, and compares the result with the threshold value X2. Then, the optical communication system 100a of the fourth embodiment allocates link aggregations based on the total traffic volume Z so as to enable operation with the minimum number of ports. This allows ports of the upstream device 61 and ports of the concentrator switch 12 that configure unnecessary link aggregations to be put into a sleep state. As a result, power consumption can be reduced.

[0141] Fifth Embodiment In the first embodiment, the OLT aggregates the upper network 60 by changing the allocation of the upper network according to the amount of traffic flowing through each concentrator switch. The OLT then puts the ports of the upper devices and the concentrator switch ports located in the upper network that are not used for communication into a sleep state. In contrast, in the fifth embodiment, a configuration will be described in which the allocation of the upper network is changed according to the number of ONUs accommodated.

[0142] Since the system configuration in the fifth embodiment is the same as that in the first embodiment, a description of each device will be omitted. In the fifth embodiment, the processing performed by the OLT 10 is different from that in the first embodiment. The OLT 10 changes the allocation of the upper NWs 60 according to the number of ONUs accommodated. Specifically, the allocation of the upper NWs 60 is changed so as to reduce the number of upper NWs 60.

[0143] 8 is a flowchart showing the processing flow of the OLT 10 in the fifth embodiment. When an ONU 50 is newly connected to the OLT 10 (step S501), the OLT control unit 13 detects the newly connected ONU 50. For example, the OLT control unit 13 detects which PON interface unit 11 the new ONU is connected to based on a notification from the PON interface unit 11 to which the new ONU is connected. The OLT control unit 13 then determines the upstream NW 60 that will accommodate the detected new ONU (step S502). Here, it is assumed that the OLT control unit 13 has assigned multiple upstream NWs 60 (e.g., upstream NWs 60-1 and 60-2) to the new ONU.

[0144] The OLT 10 grasps the accommodation status of the ONUs 50 (step S503). Specifically, the PON control unit 15 of each PON interface unit 11 counts the number of ONUs 50 connected to the PON signal processing unit 14 via the optical splitter 40. At this time, the PON control unit 15 of each PON interface unit 11 counts the number of ONUs 50 excluding inactive ONUs.

[0145] The PON interface unit 11-1 counts the number of ONUs 50 excluding inactive ONUs among one or more ONUs 50 connected to the PON signal processing unit 14-1 via, for example, an optical splitter 40-1. The PON interface unit 11-2 counts the number of ONUs 50 excluding inactive ONUs among one or more ONUs 50 connected to the PON signal processing unit 14-2 via, for example, an optical splitter 40-2. The PON interface unit 11-K counts the number of ONUs 50 excluding inactive ONUs among one or more ONUs 50 connected to the PON signal processing unit 14-K via, for example, an optical splitter 40-K.

[0146] The PON control unit 15 of each PON interface unit 11 outputs information about the number of measured ONUs 50 to the OLT control unit 13. Inactive ONUs also include ONUs 50 whose UNI (User Network Interface) is Energy-Efficient Ethernet (EEE) (Ethernet is a registered trademark) and is in Low Power Idle (LPI). Inactive ONUs do not generate traffic between the OLT 10 and the upper NW 60, so they are excluded from the measurement targets.

[0147] The OLT control unit 13 acquires information on the number of ONUs 50 output from the PON control unit 15 of each PON interface unit 11. This allows the OLT control unit 13 to grasp the number of ONUs 50 that need to communicate in the OLT 10. The number of ONUs 50 that can be accommodated in the OLT 10 is the number of all ONUs 50 connected to the OLT 10 minus the number of inactive ONUs.

[0148] The OLT control unit 13 determines whether there is an upper network 60 whose number of ONUs accommodated exceeds a threshold value X3 by referring to the information on the number of ONUs 50 that has been grasped (step S504). The threshold value X3 is a value that serves as a reference when the number of ONUs 50 accommodated in one upper network 60 is large. The threshold value X3 is set to a value that indicates that the number of ONUs 50 accommodated in one upper network 60 is large, for example.

[0149] The value indicating that the number of ONUs 50 accommodated in one upper NW 60 is large may be a value that can be determined as a generally large number of ONUs accommodated in one upper NW, for example, through experience or experimentation. The value indicating that the number of ONUs 50 accommodated in one upper NW 60 is large is set in advance.

[0150] The OLT control unit 13 compares the number of ONUs accommodated in each of the identified upper NWs 60 with a threshold X3 to determine whether or not there is an upper NW 60 whose number of ONUs accommodated exceeds the threshold X3. If there is even one upper NW 60 whose number of ONUs accommodated exceeds the threshold X3, the OLT control unit 13 determines that there is an upper NW 60 whose number of ONUs accommodated exceeds the threshold X3. On the other hand, if there is no upper NW 60 whose number of ONUs accommodated exceeds the threshold X3, the OLT control unit 13 determines that there is no upper NW 60 whose number of ONUs accommodated exceeds the threshold X3.

[0151] If the OLT control unit 13 determines that there is no upper network 60 whose ONU accommodation number exceeds the threshold value X3 (step S504-NO), the OLT control unit 13 determines whether there is an upper network 60 whose ONU accommodation number is below the threshold value Y3 by referring to the information on the number of ONUs 50 that has been grasped (step S505). The threshold value Y3 is a value that serves as a reference when the number of ONUs 50 accommodated in one upper network 60 is small. The threshold value Y3 is set to, for example, a value that indicates that the number of ONUs 50 accommodated in one upper network 60 is small.

[0152] The value indicating that the number of ONUs 50 accommodated in one upper NW 60 is small may be a value that can be determined, for example, through experience or experimentation, as a generally small number of ONUs 50 accommodated in one upper NW 60. The value indicating that the number of ONUs 50 accommodated in one upper NW 60 is small is set in advance.

[0153] The OLT control unit 13 compares the number of ONUs accommodated in each identified upper network 60 with a threshold Y3 to determine whether or not there is an upper network 60 whose number of ONUs accommodated is below the threshold Y3. If there is even one upper network 60 whose number of ONUs accommodated is below the threshold Y3, the OLT control unit 13 determines that there is an upper network 60 whose number of ONUs accommodated is below the threshold Y3. On the other hand, if there is no upper network 60 whose number of ONUs accommodated is below the threshold Y3, the OLT control unit 13 determines that there is no upper network 60 whose number of ONUs accommodated is below the threshold Y3.

[0154] If the OLT control unit 13 determines that there is no upper network 60 in which the number of ONUs accommodated is below the threshold Y3 (step S505-NO), the OLT control unit 13 puts unused ports of the line concentrator 12 into a sleep state (step S506). After putting unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S507). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S503.

[0155] The process of step S507 may be performed when at least one inactive ONU has started up, instead of waiting for a predetermined time. In this case, the process of step S503 is not performed until at least one inactive ONU has started up. The start-up of an inactive ONU may be recognized when traffic from the inactive ONU occurs.

[0156] In the process of step S504, if the OLT control unit 13 determines that there is a port whose ONU accommodation number exceeds the threshold value X3 (step S504-YES), the OLT control unit 13 determines whether or not the number of upper NWs 60 in use is less than the maximum number N1 of upper NWs (step S508). That is, the OLT control unit 13 determines whether or not the number of upper NWs 60 currently in use is less than the number of all upper NWs 60 assigned to the ONUs 50.

[0157] If the OLT control unit 13 determines that the number of used upper NWs 60 is not less than the maximum number N1 of upper NWs (step S508—NO), the OLT control unit 13 waits for a predetermined time (step S509). The OLT control unit 13 executes the process of step S503 after the predetermined time has elapsed. On the other hand, if the OLT control unit 13 determines that the number of used upper NWs 60 is less than the maximum number N1 of upper NWs (step S508—YES), the OLT control unit 13 uses unused upper NWs 60 to determine whether the number of ONUs accommodated in each upper NW 60 can be set to a threshold value X3 or less (step S509). For example, the OLT control unit 13 uses unused upper NWs 60 to average the number of ONUs accommodated, thereby determining whether the number of ONUs accommodated in each upper NW 60 can be set to a threshold value X3 or less.

[0158] If the OLT control unit 13 determines that the number of ONUs accommodated in each upstream NW 60 can be reduced to or below the threshold X3 using unused upstream NWs 60 (step S509—YES), the OLT control unit 13 reassigns the upstream NWs 60 so as to minimize the number of upstream NWs (step S510). The OLT control unit 13 then cancels the sleep mode of the ports (step S511). For example, the OLT control unit 13 cancels the sleep mode of the first ports of the multiplexing units 16 of each concentrator switch 12 that are to be used through the reassignment. At this time, the OLT control unit 13 outputs a control signal to the target concentrator switch 12, including information for identifying the first port to be used and a sleep mode cancel command.

[0159] The SW control unit 17 of the target line concentrator 12 receives a control signal output from the OLT control unit 13. The SW control unit 17 releases the sleep state of the first port of the multiplexing unit 16, which is indicated by the information for identifying the first port included in the received control signal. This makes the released first port available for use. Furthermore, the OLT control unit 13 releases the sleep state of a port that has become the target of use through reallocation, for example, among the ports of the higher-level devices 61 arranged in each higher-level NW 60. At this time, the OLT control unit 13 transmits a control signal to the OLT operation unit 20, which includes information for identifying the port to be used, information for identifying the higher-level device 61, and a sleep release instruction.

[0160] The OLT operation unit 20 receives a control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30. The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transfers the control signal to the upper device 61 identified based on information for identifying the upper device 61 included in the received control signal.

[0161] The upper device 61 receives the control signal transferred from the upper NW operation unit 30. The upper device 61 releases the sleep mode of the port indicated by the information for identifying the port included in the received control signal. This makes the released port available for use. The OLT control unit 13 then waits for a predetermined time (step S507). The OLT control unit 13 executes the process of step S503 after the predetermined time has elapsed.

[0162] If the OLT control unit 13 determines that the number of ONUs accommodated in each upper network cannot be set to the threshold value X3 or less using unused upper networks 60 (step S509-NO), the OLT control unit 13 uses all upper networks 60 to proportionally divide the number of ONUs accommodated (step S512). Then, the OLT control unit 13 waits for a predetermined time (step S507). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S503.

[0163] In the process of step S505, if the OLT control unit 13 determines that there is an upstream network whose ONU accommodation number is below the threshold Y3 (step S505-YES), the OLT control unit 13 determines whether there are multiple upstream networks 60 in use (step S513). If the OLT control unit 13 determines that there are not multiple upstream networks 60 in use (step S513-NO), the OLT control unit 13 puts unused ports of the concentrator switch 12 into a sleep state (step S514). After putting unused ports of the concentrator switch into a sleep state, the OLT control unit 13 waits for a predetermined time (step S507). The OLT control unit 13 executes the process of step S503 after the predetermined time has elapsed.

[0164] On the other hand, if the OLT control unit 13 determines that there are multiple upstream NWs 60 in use (step S513—YES), the OLT control unit 13 determines whether the sum of the ONU capacity of the upstream NW 60 with the smallest ONU capacity and the ONU capacity of the upstream NW 60 with the second-smallest ONU capacity exceeds threshold X3 (step S515). If the OLT control unit 13 determines that the sum of the ONU capacity exceeds threshold X3 (step S515—YES), the OLT control unit 13 puts unused ports of the line concentrator 12 into a sleep state (step S516). After putting unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S507).

[0165] On the other hand, if the OLT control unit 13 determines that the sum of the number of ONUs accommodated does not exceed the threshold value X3 (step S515-NO), the OLT control unit 13 aggregates the upper NWs 60 (step S516). After aggregating the upper NWs 60, the OLT control unit 13 again determines whether there are multiple upper NWs 60 in use (step S513).

[0166] 9 is a sequence diagram showing the processing flow of the optical communication system 100 in the fifth embodiment. The OLT control unit 13 inquires of each PON interface unit 11 about the number of ONUs 50 accommodated therein (step S521). In response to the inquiry from the OLT control unit 13, the PON control unit 15 of each PON interface unit 11 replies with the number of ONUs 50 accommodated therein (step S522). At this time, the PON control unit 15 of each PON interface unit 11 replies with the number of ONUs 50 excluding inactive ONUs.

[0167] The OLT control unit 13 acquires information on the number of ONUs 50 output from the PON control unit 15 of each PON interface unit 11. The OLT control unit 13 considers changing the accommodation allocation of the upper network 60 based on the acquired information on the number of ONUs 50 (step S523). Specific processing is as shown in FIG. 8 . If, as a result of the consideration, it becomes necessary to change the accommodation allocation of the upper network 60, the OLT control unit 13 checks with the upper network operation unit 30 whether it is possible to change the allocation of the upper network 60.

[0168] For example, the OLT control unit 13 generates a control signal including an inquiry for confirming whether or not it is possible to change the allocation of the upper NW 60. The OLT control unit 13 transmits the generated control signal to the OLT operation unit 20 (step S524). The OLT operation unit 20 receives the control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30 (step S525).

[0169] The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 determines whether the allocation of the upper NW 60 can be changed based on the inquiry content included in the received control signal. Here, it is assumed that the upper NW operation unit 30 determines that the allocation of the upper NW 60 can be changed. In this case, the upper NW operation unit 30 generates a control signal including a response indicating that the allocation of the upper NW 60 can be changed. The upper NW operation unit 30 transmits the generated control signal to the OLT operation unit 20 (step S526).

[0170] The OLT operation unit 20 receives the control signal transmitted from the upper NW operation unit 30. The OLT operation unit 20 transfers the received control signal to the OLT 10 (step S527). The OLT control unit 13 receives the control signal transferred from the OLT operation unit 20. Based on the response included in the received control signal, the OLT control unit 13 determines that the allocation of the upper NW 60 can be changed. The OLT control unit 13 controls the allocation of the upper NW 60 in accordance with the result of the review of the processing in step S523 (step S528).

[0171] Thereafter, in accordance with the allocation control of the upper NW 60, the OLT control unit 13 puts the port of the upper device 61 of the upper NW 60 into a sleep state, or releases the sleep state of the port of the upper device 61. Furthermore, in accordance with the allocation control of the upper NW 60, the OLT control unit 13 puts the first port of the multiplexing unit 16 of the line concentrator 12 into a sleep state, or releases the sleep state of the first port of the multiplexing unit 16 of the line concentrator 12.

[0172] For example, when it is determined in the processing of step S513 that there are no multiple upstream NWs 60 in use, or when it is determined in the processing of step S515 that the sum of the traffic volumes exceeds the threshold X1, the OLT control unit 13 puts the port of the upstream device 61 of the upstream NW 60 and the first port of the multiplexing unit 16 of the line concentrator 12 into a sleep state. For example, after the processing of step S510, the OLT control unit 13 releases the sleep state of the port of the upstream device 61 of the upstream NW 60 and the first port of the multiplexing unit 16 of the line concentrator 12.

[0173] The OLT control unit 13 generates a control signal including a sleep instruction when putting a port of the upper device 61 of the upper NW 60 into a sleep state. On the other hand, the OLT control unit 13 generates a control signal including a sleep release instruction when releasing the sleep state of the port of the upper device 61 of the upper NW 60. The OLT control unit 13 transmits the generated control signal to the OLT operation unit 20 (step S529). The OLT operation unit 20 receives the control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30 (step S530).

[0174] The OLT control unit 13 generates a control signal including a sleep instruction when putting the first port of the multiplexing unit 16 of the line concentrator 12 into a sleep state. On the other hand, the OLT control unit 13 generates a control signal including a sleep cancellation instruction when releasing the sleep state of the first port of the multiplexing unit 16 of the line concentrator 12. The OLT control unit 13 outputs the generated control signal to the target line concentrator 12 (step S531).

[0175] The SW control unit 17 of the line concentrator 12 acquires the control signal output from the OLT control unit 13. The SW control unit 17 puts the first port of the multiplexing unit 16 into a sleep state or releases the sleep state of the first port in accordance with the instruction included in the acquired control signal. When the SW control unit 17 completes the processing according to the instruction, it notifies the OLT control unit 13 that the processing has been completed (step S532).

[0176] The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transmits the received control signal to the upper device 61 of the target upper NW 60 (step S533). The upper device 61 receives the control signal transmitted from the upper NW operation unit 30. The upper device 61 puts the port into a sleep state or releases the port from sleep mode in accordance with the instruction contained in the received control signal.

[0177] When the upper level device 61 completes the processing in accordance with the instruction, it transmits a control signal indicating the completion of the processing to the upper level NW operation unit 30 (step S534). The upper level NW operation unit 30 receives the control signal transmitted from the upper level device 61. The upper level NW operation unit 30 transfers the received control signal to the OLT operation unit 20 (step S535). The OLT operation unit 20 transmits the control signal transferred from the upper level NW operation unit 30 to the OLT 10 (step S536).

[0178] The OLT control unit 13 receives the notification output from the SW control unit 17 and the control signal transmitted from the OLT operation unit 20. This completes the change of the accommodation allocation of the upper NW 60.

[0179] Conventionally, when a new ONU 50 is connected to the OLT 10, the OLT 10 sets the upstream NW 60 that will accommodate the new ONU 50. This upstream NW 60 remains unchanged unless the location of the upstream NW 60 is actively changed. Therefore, once the OLT 10 has set and activated the port of the line concentrator switch 12 for the upstream NW 60, it always operates even when traffic volume is low. Even during low-traffic times, such as at night, the port operates in the same way as it does during the daytime when traffic volume is high, resulting in poor power efficiency.

[0180] In contrast, according to the optical communication system 100 of the fifth embodiment, the allocation of the upper NWs 60 is changed according to the number of ONUs 50 accommodated. Specifically, the allocation of the upper NWs 60 is changed so as to reduce the number of upper NWs 60 accommodating ONUs 50. By aggregating the upper NWs 60 in this way, the ports of the upper devices 61 and the ports of the line concentrator switch 12 arranged in the upper NWs 60 not used for communication can be put into a sleep state without affecting communication. As a result, it is possible to reduce power consumption.

[0181] (Sixth embodiment) In the fifth embodiment, the OLT aggregates the upper network 60 by changing the allocation of the upper network according to the number of ONUs accommodated. Then, the OLT puts the ports of the upper devices and the concentrator switch located in the upper network that are not used for communication into a sleep state. In contrast, in the sixth embodiment, a configuration for reducing power consumption when there is one upper network will be described.

[0182] The system configuration of the sixth embodiment is the same as that of the second embodiment, and therefore a description of each device will be omitted. In the sixth embodiment, the processing performed by the OLT 10 differs from that of the second embodiment. Specifically, the OLT 10 rearranges the accommodation within the link aggregation based on the number of ONUs accommodated in each LAG port of the line concentrator switch 12. For example, the OLT 10 reallocates the link aggregation so as to minimize the number of ports in use. This allows ports constituting unnecessary link aggregations to go to sleep. As a result, power consumption can be reduced.

[0183] 10 is a flowchart showing the processing flow of the OLT 10 in the sixth embodiment. When an ONU 50 is newly connected to the OLT 10 (step S601), the OLT control unit 13 detects the newly connected ONU 50. For example, the OLT control unit 13 detects which PON interface unit 11 the new ONU is connected to based on a notification from the PON interface unit 11 to which the new ONU is connected. The OLT control unit 13 then determines the upstream NW 60 that will accommodate the detected new ONU (step S602). Here, it is assumed that the OLT control unit 13 assigns one upstream NW 60 to the new ONU.

[0184] Thereafter, the OLT control unit 13 determines the LAG port that will accommodate the new ONU (step S603). The OLT 10 grasps the accommodation status of the ONUs 50 (step S604). Specifically, the PON control unit 15 of each PON interface unit 11 counts the number of ONUs 50 connected to the PON signal processing unit 14 via the optical splitter 40. At this time, the PON control unit 15 of each PON interface unit 11 counts the number of ONUs 50 excluding inactive ONUs. The PON control unit 15 of each PON interface unit 11 outputs information on the counted number of ONUs 50 to the OLT control unit 13. The OLT control unit 13 acquires the information on the number of ONUs 50 output from the PON control unit 15 of each PON interface unit 11.

[0185] The OLT control unit 13 calculates the number of ONUs that can be accommodated for each LAG port using the acquired information on the number of ONUs 50. For example, the OLT control unit 13 calculates the number of ONUs that can be accommodated for each LAG port by adding up the numbers of ONUs 50 that are accommodated in multiple first ports that are considered to be in the same group by link aggregation. This allows the OLT control unit 13 to grasp the information on the number of ONUs that can be accommodated for each LAG port.

[0186] The OLT control unit 13 determines whether there is a LAG port whose ONU capacity exceeds threshold X3 by referring to the acquired information on the number of ONUs accommodated for each LAG port (step S605). The OLT control unit 13 determines whether there is a LAG port whose ONU capacity exceeds threshold X3 by comparing the ONU capacity for each LAG port with threshold X3. If there is even one LAG port whose ONU capacity exceeds threshold X3, the OLT control unit 13 determines that there is a LAG port whose ONU capacity exceeds threshold X3. On the other hand, if there is no LAG port whose ONU capacity exceeds threshold X3, the OLT control unit 13 determines that there is no LAG port whose ONU capacity exceeds threshold X3.

[0187] If the OLT control unit 13 determines that there is no LAG port whose ONU accommodation number exceeds the threshold X3 (step S605-NO), the OLT control unit 13 determines whether there is a LAG port whose ONU accommodation number is below the threshold Y3 by referring to the acquired information on the ONU accommodation number for each LAG port (step S606). The OLT control unit 13 compares the ONU accommodation number for each LAG port with the threshold Y3 to determine whether there is a LAG port whose ONU accommodation number is below the threshold Y3.

[0188] If there is even one LAG port whose ONU accommodation number is below the threshold Y3, the OLT control unit 13 determines that there is a LAG port whose ONU accommodation number is below the threshold Y3. On the other hand, if there is not a single LAG port whose ONU accommodation number is below the threshold Y3, the OLT control unit 13 determines that there is no LAG port whose ONU accommodation number is below the threshold Y3.

[0189] If the OLT control unit 13 determines that there is no LAG port whose ONU accommodation number is below the threshold Y3 (step S606-NO), the OLT control unit 13 puts unused ports of the line concentrator 12 into a sleep state (step S607). After putting unused ports of the line concentrator into a sleep state, the OLT control unit 13 waits for a predetermined time (step S608). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S604.

[0190] The process of step S6087 may wait until at least one inactive ONU has started up instead of waiting for a predetermined time. In this case, the process of step S604 is not executed until at least one inactive ONU has started up.

[0191] In the process of step S605, if the OLT control unit 13 determines that there is a LAG port whose ONU accommodation number exceeds the threshold value X3 (step S605-YES), the OLT control unit 13 determines whether or not the number of LAG ports in use is less than the total number N2 of LAGs for the upper network (step S609). That is, the OLT control unit 13 determines whether or not the number of LAG ports currently in use is less than the number of all LAGs for the upper network.

[0192] If the OLT control unit 13 determines that the number of LAG ports in use is not less than the total number N2 of LAGs for the upstream network (step S609—NO), it waits for a predetermined time (step S608). The OLT control unit 13 executes the process of step S604 after the predetermined time has elapsed. On the other hand, if the OLT control unit 13 determines that the number of LAG ports in use is less than the total number N2 of LAGs for the upstream network (step S609—YES), the OLT control unit 13 uses unused ports to determine whether the number of ONUs accommodated in each LAG port can be set to a threshold X3 or less (step S610). For example, the OLT control unit 13 uses the unused first port to average the number of ONUs accommodated and determine whether the number of ONUs accommodated in each LAG port can be set to a threshold X3 or less.

[0193] If the OLT control unit 13 determines that the number of ONUs accommodated in each LAG port can be reduced to or below the threshold X3 using unused first ports (step S610—YES), the OLT control unit 13 reassigns the LAGs so as to minimize the number of ports in use (step S611). The OLT control unit 13 then releases the sleeping ports (step S612). For example, the OLT control unit 13 releases the sleeping ports of the first ports of the multiplexing unit 16 of each concentrator switch 12 that have become the target ports for use through the reassignment. At this time, the OLT control unit 13 outputs a control signal to the target concentrator switch 12, including information for identifying the target first port and a sleep release instruction.

[0194] The SW control unit 17 of the target line concentrator 12 receives a control signal output from the OLT control unit 13. The SW control unit 17 releases the sleep state of the first port of the multiplexing unit 16, which is indicated by the information for identifying the first port included in the received control signal. This makes the released first port available for use. Furthermore, the OLT control unit 13 releases the sleep state of a port that has become the target of use through reallocation, for example, among the ports of the higher-level devices 61 arranged in each higher-level NW 60. At this time, the OLT control unit 13 transmits a control signal to the OLT operation unit 20, which includes information for identifying the port to be used, information for identifying the higher-level device 61, and a sleep release instruction.

[0195] The OLT operation unit 20 receives a control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30. The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transfers the control signal to the upper device 61 identified based on information for identifying the upper device 61 included in the received control signal.

[0196] The upper device 61 receives the control signal transferred from the upper NW operation unit 30. The upper device 61 releases the sleep mode of the port indicated by the information for identifying the port included in the received control signal. This makes the released port available for use. Thereafter, the OLT control unit 13 waits for a predetermined time (step S608). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S604.

[0197] If the OLT control unit 13 determines that the number of ONUs accommodated in each LAG port cannot be set to the threshold X3 or less using unused first ports (step S610-NO), the OLT control unit 13 uses all first ports to apportion the number of ONUs accommodated (step S613).The OLT control unit 13 then waits for a predetermined time (step S608).After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S604.

[0198] In the process of step S606, if the OLT control unit 13 determines that there is a LAG port whose ONU accommodation number is below the threshold Y3 (step S606-YES), the OLT control unit 13 determines whether there are multiple LAG ports in use (step S614). If the OLT control unit 13 determines that there are not multiple LAG ports in use (step S614-NO), the OLT control unit 13 puts the unused ports of the line concentrator 12 into a sleep state (step S615). After putting the unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S608). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S604.

[0199] On the other hand, if the OLT control unit 13 determines that there are multiple LAG ports in use (step S614—YES), the OLT control unit 13 determines whether the sum of the number of ONUs accommodated in the port with the fewest ONU capacity and the number of ONUs accommodated in the port with the second fewest ONU capacity exceeds threshold X3 (step S616). If the OLT control unit 13 determines that the sum of the ONU capacity numbers exceeds threshold X3 (step S616—YES), the OLT control unit 13 puts unused ports of the line concentrator 12 into a sleep state (step S607). After putting unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S608).

[0200] If the OLT control unit 13 determines that the sum of the number of accommodated ONUs does not exceed the threshold value X3 (step S616-NO), the OLT control unit 13 aggregates the LAG ports (step S617). After aggregating the LAG ports, the OLT control unit 13 again determines whether there are multiple LAG ports in use (step S614).

[0201] According to the optical communication system 100a of the sixth embodiment configured as described above, even when there is only one upper NW 60, the same effects as those of the fifth embodiment can be obtained. Specifically, in the optical communication system 100a, the link aggregation allocation is changed depending on the number of ONUs 50 accommodated. For example, in the optical communication system 100a of the sixth embodiment, the link aggregation allocation is changed so as to reduce the number of ports used. This allows the ports of the upper device 61 and the port of the line concentrator 12 that configure unnecessary link aggregations to be put into a sleep state. As a result, it is possible to reduce power consumption.

[0202] In the fifth embodiment, the OLT changes the allocation of the upper network by comparing the number of ONUs that are communicating with a threshold value. In contrast, in the seventh embodiment, a configuration will be described in which the OLT changes the allocation of the upper network based on the total number of ONUs (total number of devices that are accommodated), which is the total number of ONUs that are communicating.

[0203] Since the system configuration in the seventh embodiment is the same as that in the fifth embodiment, a description of each device will be omitted. In the seventh embodiment, the processing performed by the OLT 10 differs from that in the first embodiment. Specifically, the OLT 10 calculates a total number of ONUs Z1, which is the total number of ONUs 50 communicating. The OLT 10 compares the result of dividing the calculated total number of ONUs Z1 by the maximum number of upper NWs N1 with a threshold value X4. The threshold value X4 is a value used to determine the number of ONUs per port. The number of ONUs per port represents the number of ONUs accommodated in one port. The threshold value X4 is set to an arbitrary value.

[0204] If the division result is equal to or less than the threshold value X4 as a result of the comparison, the OLT 10 allocates the upper NW 60 so that the number of ONUs 50 accommodated per port becomes equal to the threshold value X4. The division result being equal to or less than the threshold value X4 means that the number of ONUs 50 accommodated per port can be increased. Therefore, if the division result is equal to or less than the threshold value X4, the OLT 10 reallocates the upper NW 60 to each port so that the number of ONUs 50 accommodated per port approaches the threshold value X4. This reduces the number of ports used.

[0205] On the other hand, if the division result is not equal to or less than the threshold value X4 as a result of the comparison, the OLT 10 releases the sleep state of the unused ports. If the division result is not equal to or less than the threshold value X4, this means that the number of ONUs 50 accommodated per port is high, and therefore it is necessary to reduce the number of ONUs 50 accommodated per port. Therefore, if the division result is not equal to or less than the threshold value X4, the OLT 10 releases the sleep state of the unused ports, making them usable, and performs control to reduce the number of ONUs 50 accommodated per port.

[0206] Fig. 11 is a flowchart showing the flow of processing by the OLT 10 in the seventh embodiment. In Fig. 11, the same processes as those in Fig. 8 are denoted by the same reference numerals as those in Fig. 8, and the description thereof will be omitted.

[0207] When the processes from step S501 to step S503 are completed, the OLT control unit 13 calculates the total number of ONUs Z1 of all ports by adding up the acquired numbers of ONUs 50 (step S701). Based on the calculated total number of ONUs Z1, the maximum number of upper NWs N1, and the threshold value X4, the OLT control unit 13 determines whether the result of dividing the total number of ONUs Z1 by the maximum number of upper NWs N1 is equal to or less than the threshold value X4 (step S702).

[0208] If the OLT control unit 13 determines that the division result is equal to or less than the threshold value X4 (step S702-YES), the OLT control unit 13 allocates the upper NW 60 so that the number of ONUs accommodated per port becomes the threshold value X4 (step S703). At this time, the OLT control unit 13 allocates the upper NW 60 so that the number of ONUs accommodated per port becomes as close to the threshold value X4 as possible, and reduces the number of first ports used.

[0209] Thereafter, the OLT control unit 13 puts the unused ports of the line concentrator 12 into a sleep state (step S704). After putting the unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S705). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S503.

[0210] The process of step S705 may be performed when at least one inactive ONU has started up, instead of waiting for a predetermined time. In this case, the process of step S503 is not performed until at least one inactive ONU has started up. The start-up of an inactive ONU may be recognized when traffic from the inactive ONU occurs.

[0211] In the process of step S702, if the OLT control unit 13 determines that the division result is not equal to or less than the threshold value X4 (step S702-NO), the OLT control unit 13 cancels the sleep of the unused ports (step S706). The OLT control unit 13 cancels the sleep of the unused ports, for example, among the first ports of the multiplexing units 16 of each concentrator switch 12. At this time, the OLT control unit 13 outputs a control signal including information for identifying the unused port and a sleep cancellation instruction to the target concentrator switch 12.

[0212] The SW control unit 17 of the target line concentrator 12 receives a control signal output from the OLT control unit 13. The SW control unit 17 releases the sleep mode of the first port of the multiplexing unit 16, which is indicated by the information for identifying the first port included in the received control signal. This makes the released first port available for use. Furthermore, the OLT control unit 13 releases the sleep mode of unused ports, for example, among the ports of the higher-level devices 61 arranged in each higher-level NW 60. At this time, the OLT control unit 13 transmits a control signal to the OLT operation unit 20, which includes information for identifying the port to be used, information for identifying the higher-level device 61, and a sleep release instruction.

[0213] The OLT operation unit 20 receives a control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30. The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transfers the control signal to the upper device 61 identified based on information for identifying the upper device 61 included in the received control signal.

[0214] The host device 61 receives the control signal transferred from the host NW operation unit 30. The host device 61 releases the sleep state of the port indicated by the information for identifying the port included in the received control signal. This makes the released port available for use.

[0215] Thereafter, the OLT control unit 13 distributes the accommodated number of ONUs 50 among all the upper NWs 60 (step S707). The OLT control unit 13 waits for a predetermined time (step S705). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S703.

[0216] The optical communication system 100 of the seventh embodiment configured as described above can achieve the same effects as the fifth embodiment. In the fifth embodiment, the number of ONUs accommodated in each upper network 60 was compared with the threshold X3. In contrast, the optical communication system 100 of the seventh embodiment compares the total number of ONUs Z1, which is the sum of the number of ONUs accommodated in each upper network 60, divided by the maximum number of upper networks N1, with the threshold X4. The optical communication system 100 of the seventh embodiment then allocates upper networks 60 based on the total number of ONUs Z1 so as to enable operation with the minimum number of ports. By aggregating upper networks 60 in this manner, the ports of the upper network devices 61 and the ports of the line concentrator switch 12 located in upper networks 60 that are not used for communication can be put into a sleep state without affecting communication. As a result, power consumption can be reduced.

[0217] In the sixth embodiment, the OLT changes the link aggregation allocation by comparing the number of ONUs that are communicating at each LAG port with a threshold value. In contrast, in the eighth embodiment, a configuration will be described in which the link aggregation allocation is changed based on the total number of ONUs, which is the total number of ONUs that are communicating at each LAG port.

[0218] Since the system configuration of the eighth embodiment is the same as that of the sixth embodiment, a description of each device will be omitted. In the eighth embodiment, the processing performed by the OLT 10 differs from that of the sixth embodiment. Specifically, the OLT 10 calculates a total number of ONUs Z1, which is the total number of ONUs 50 communicating at each LAG port. The OLT 10 divides the calculated total number of ONUs Z1 by the total number of LAGs N2 for the upper network, and compares the result with a threshold value X4.

[0219] If the division result is equal to or less than the threshold value X4 as a result of the comparison, the OLT 10 allocates link aggregation so that the number of ONUs per port is equal to the threshold value X4. The division result being equal to or less than the threshold value X4 means that the number of ONUs 50 accommodated per port can be increased. Therefore, if the division result is equal to or less than the threshold value X4, the OLT 10 reallocates link aggregation so that the number of ONUs 50 accommodated per port approaches the threshold value X4. This reduces the number of ports used.

[0220] On the other hand, if the division result is not equal to or less than the threshold value X4 as a result of the comparison, the OLT 10 releases the sleep state of the unused ports. If the division result is not equal to or less than the threshold value X4, this means that the number of ONUs 50 accommodated per port is high, and therefore it is necessary to reduce the number of ONUs 50 accommodated per port. Therefore, if the division result is not equal to or less than the threshold value X4, the OLT 10 releases the sleep state of the unused ports, making them usable, and performs control to reduce the number of ONUs 50 accommodated per port.

[0221] Fig. 12 is a flowchart showing the flow of processing by the OLT 10 in the eighth embodiment. In Fig. 12, the same processes as those in Fig. 10 are denoted by the same reference numerals as those in Fig. 10, and the description thereof will be omitted.

[0222] After the processes from step S601 to step S604 are completed, the OLT control unit 13 calculates the total number of ONUs Z1 for all LAG ports by adding up the acquired number of ONUs 50 for each LAG port (step S801). Then, based on the total number of ONUs Z1, the total number of LAGs N2 for the upstream network, and the threshold value X4, the OLT control unit 13 determines whether the result of dividing the total number of ONUs Z1 by the total number of LAGs N2 for the upstream network is equal to or less than the threshold value X4 (step S802).

[0223] If the OLT control unit 13 determines that the division result is equal to or less than the threshold value X4 (step S802-YES), the OLT control unit 13 allocates the upper NW 60 so that the number of ONUs accommodated per port becomes the threshold value X4 (step S803). At this time, the OLT control unit 13 allocates the upper NW 60 so that the number of ONUs accommodated per port becomes as close to the threshold value X4 as possible, and reduces the number of first ports used.

[0224] Thereafter, the OLT control unit 13 puts the unused ports of the line concentrator 12 into a sleep state (step S804). After putting the unused ports of the line concentrator 12 into a sleep state, the OLT control unit 13 waits for a predetermined time (step S805). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S604.

[0225] The process of step S805 may be performed when at least one inactive ONU has started up, instead of waiting for a predetermined time. In this case, the process of step S604 is not performed until at least one inactive ONU has started up. The start-up of an inactive ONU may be recognized when traffic from the inactive ONU occurs.

[0226] In the process of step S802, if the OLT control unit 13 determines that the division result is not equal to or less than the threshold value X4 (step S802-NO), the OLT control unit 13 cancels the sleep of the unused ports (step S806). The OLT control unit 13 cancels the sleep of the unused ports, for example, among the first ports of the multiplexing unit 16 of each concentrator switch 12. At this time, the OLT control unit 13 outputs a control signal including information for identifying the unused port and a sleep cancellation instruction to the target concentrator switch 12.

[0227] The SW control unit 17 of the target line concentrator 12 receives a control signal output from the OLT control unit 13. The SW control unit 17 releases the sleep mode of the first port of the multiplexing unit 16, which is indicated by the information for identifying the first port included in the received control signal. This makes the released first port available for use. Furthermore, the OLT control unit 13 releases the sleep mode of unused ports, for example, among the ports of the higher-level devices 61 arranged in each higher-level NW 60. At this time, the OLT control unit 13 transmits a control signal to the OLT operation unit 20, which includes information for identifying the port to be used, information for identifying the higher-level device 61, and a sleep release instruction.

[0228] The OLT operation unit 20 receives a control signal transmitted from the OLT control unit 13. The OLT operation unit 20 transfers the received control signal to the upper NW operation unit 30. The upper NW operation unit 30 receives the control signal transferred from the OLT operation unit 20. The upper NW operation unit 30 transfers the control signal to the upper device 61 identified based on information for identifying the upper device 61 included in the received control signal.

[0229] The host device 61 receives the control signal transferred from the host NW operation unit 30. The host device 61 releases the sleep state of the port indicated by the information for identifying the port included in the received control signal. This makes the released port available for use.

[0230] Thereafter, the OLT control unit 13 distributes the number of accommodated ONUs among all the first ports (step S807). The OLT control unit 13 waits for a predetermined time (step S805). After the predetermined time has elapsed, the OLT control unit 13 executes the process of step S604.

[0231] The optical communication system 100a of the eighth embodiment configured as described above can achieve the same effects as the sixth embodiment. In the sixth embodiment, the number of ONUs accommodated per LAG port of each concentrator switch 12 was compared with the threshold X3. In contrast, the optical communication system 100a of the eighth embodiment compares the total number of ONUs Z1, which is the sum of the number of ONUs accommodated per LAG port of each concentrator switch 12, divided by the total number of LAGs N2 for the upper network, with the threshold X4. The optical communication system 100a of the eighth embodiment then allocates link aggregations based on the total number of ONUs Z1 so as to enable operation with the minimum number of ports. This allows ports of the higher-level device 61 and ports of the concentrator switch 12 that configure unnecessary link aggregations to be put into a sleep state. As a result, power consumption can be reduced.

[0232] Some of the functions of the OLT 10 in the above-described embodiment may be implemented by a computer. In this case, a program for implementing these functions may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" here includes hardware such as an operating system (OS) and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, read-only memories (ROMs), and CD-ROMs, as well as storage devices such as hard disks built into computer systems.

[0233] Furthermore, the term "computer-readable recording medium" may include a medium that dynamically stores a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, or a medium that stores a program for a certain period of time, such as a volatile memory within a computer system that serves as a server or client in such a case. The program may also be one that realizes part of the above-mentioned functions, or one that can realize the above-mentioned functions in combination with a program already stored in the computer system, or one that can be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0234] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0235] The present invention can be applied to a communication system that includes a plurality of line concentrator switches and that applies link aggregation to an upper network.

[0236] 10...OLT, 11, 11-1 to 11-K...PON interface unit, 12, 12-1 to 12-O...line concentrator switch, 13, 13a...OLT control unit, 14, 14-1 to 14-K...PON signal processing unit, 15, 15-1 to 15-K...PON control unit, 16, 16-1 to 16-O...multiplexing unit, 17, 17-1 to 17-O...SW control unit, 20...OLT operation unit, 30...host NW operation unit, 40, 40-1 to 40-K...optical splitter, 50, 50-1 to 50-M...ONU, 60, 60-1 to 60-L...host NW, 61, 61-1 to 61-L...host device, 100, 100a...optical communication system

Claims

1. A communications device comprising: a plurality of concentrators having a plurality of ports connected to one or more upstream networks; and a control unit that changes a connection state between the one or more upstream networks and the plurality of concentrators based on information that affects the amount of communication between the one or more upstream networks and the plurality of concentrators, and blocks any unused ports among the plurality of ports owned by the plurality of concentrators as a result of the change in connection state.

2. The communication device according to claim 1, wherein the information affecting the communication volume between the one or more upstream networks and the multiple concentrators is the traffic volume of each of the multiple ports, and the control unit controls the opening and closing of the multiple ports of the multiple concentrators based on a comparison result between the traffic volume and a threshold value, or a comparison result between the traffic volume and a future traffic trend predicted based on traffic trends over a certain period of time.

3. The communications device according to claim 1 or 2, wherein the one or more upper networks are multiple upper networks, and the information affecting the communication volume between the one or more upper networks and the multiple concentrators is the traffic volume of each of the multiple ports, and the control unit changes a connection state between the one or more upper networks and the multiple concentrators so that the traffic volume per port is the threshold value or less when it determines that there is a port whose traffic volume will be less than a threshold value, when it determines that there is a port whose traffic volume will be less than a threshold value based on a future traffic trend predicted based on traffic trends over a certain period of time and a comparison result between the traffic volume and a threshold value, when it determines that a division result obtained by dividing a total traffic volume, which is a sum of the traffic volumes of each of the multiple ports, by a maximum number of upper networks is less than a threshold value, or when it determines that the division result is less than a threshold value based on a comparison result between the future traffic trend and the division result and a threshold value.

4. The communication device described in claim 3, wherein the control unit aggregates upper networks when there is a port whose traffic volume is less than a threshold and the sum of the traffic volumes of the port with the smallest traffic volume and the port with the second smallest traffic volume does not exceed a first threshold value that is greater than the threshold value.

5. The one or more upper networks are one upper network, and the information affecting the communication volume between the one or more upper networks and the multiple concentrators is the traffic volume of each of the multiple ports, and the control unit acquires information on the traffic volume of each link aggregation port which is a plurality of ports grouped together by link aggregation, and when it is determined that there is a link aggregation port whose traffic volume is less than a threshold, when it is determined that there is a link aggregation port whose traffic volume is less than a threshold based on a future traffic trend predicted based on traffic trends over a certain period of time and a comparison result between the traffic volume and a threshold, when it is determined that there is a link aggregation port whose traffic volume is less than a threshold, when it is determined that a division result obtained by dividing a total traffic volume which is a sum of the traffic volumes of each of the multiple link aggregation ports by a total number of link aggregations between the one upper network and the multiple concentrators is less than a threshold, or when it is determined that the division result is equal to or less than the threshold based on a comparison result between the future traffic trend and the division result and a threshold, The communication device according to claim 1 , further comprising: a communication unit configured to change a connection state between the one or more upper networks and the plurality of concentrators so that a traffic volume per port is equal to or less than the threshold value.

6. The communication device according to claim 1, wherein the one or more upper networks are multiple upper networks, and information affecting the communication volume between the one or more upper networks and the multiple concentrators is the number of accommodating devices accommodated in the one or more upper networks and communicating, and when there is an upper network in which the number of accommodating devices is less than a threshold, or when a result of dividing the total number of accommodating devices, which is the total number of accommodating devices, by the maximum number of upper networks is less than a threshold, the control unit changes the connection state between the one or more upper networks and the multiple concentrators so that the number of accommodating devices per port is less than the threshold.

7. The communication device described in claim 6, wherein the control unit consolidates the upper network if there is an upper network in which the number of accommodated devices is less than a threshold value, and if the sum of the numbers of accommodated devices of the upper network with the smallest number of accommodated devices and the upper network with the second smallest number of accommodated devices does not exceed a first threshold value that is greater than the threshold value.

8. The communications device according to claim 1, wherein the one or more upper networks are a single upper network, and information affecting the traffic volume between the one or more upper networks and the multiple concentrators is the number of accommodating devices accommodated in the one or more upper networks and communicating, and the control unit acquires information on the number of accommodating devices for each link aggregation port, which is a plurality of ports grouped together by link aggregation, and when there is a link aggregation port for which the number of accommodating devices is less than a threshold, or when a result of dividing the total number of accommodating devices, which is the total number of the accommodating devices for each of the multiple link aggregation ports, by the total number of link aggregations between the one upper network and the multiple concentrators is less than a threshold, changes a connection state between the one or more upper networks and the multiple concentrators so that the number of accommodating devices per port is equal to or less than the threshold.

9. A control method for changing a connection state between one or more upstream networks and a plurality of concentrators having a plurality of ports connected to the one or more upstream networks based on information affecting the amount of communication between the one or more upstream networks and the plurality of concentrators, and blocking unused ports among the plurality of ports of the plurality of concentrators as a result of the change in the connection state.

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