Optical line terminal and optical communication system

Abstract

This OLT (110) comprises: first transmission / reception units (122, 123) that perform optical communication with one or more first ONUs; second transmission / reception units (124, 126) that perform optical communication with one or more second ONUs; a power supply unit (142); first transmission / reception control units (127, 128) that control the first transmission / reception units (122, 123); second transmission / reception control units (129, 130) that control the second transmission / reception units (124, 126); and an OLT processing unit (141) that causes the first transmission / reception control units (127, 128) to turn off the power supply to the first transmission / reception units (122, 123) during a first period when the number of the one or more first ONUs is equal to or less than a predetermined number, and causes the second transmission / reception control units (129, 130) to turn off the power supply to the second transmission / reception units (124, 126) during a second period when the number of the one or more second ONUs is equal to or less than a predetermined number.

Description

[Technical field]

[0001] The present disclosure relates to an optical line terminal and an optical communication system. [Background technology]

[0002] A PON (Passive Optical Network) system, which is an optical communication system, includes an optical communication device (also called a parent station device) installed in a telecommunications carrier's office and multiple optical communication devices (also called child station devices) on the subscriber side (also called child station side). The parent station side optical line termination device is also called an OLT (Optical Line Termination), and the child station side optical line termination device is also called an ONU (Optical Network Unit). In a PON system, control is performed based on time division multiplexing of upstream signals. The ONU transmits an upstream signal at a timing instructed by the OLT to the ONU. The upstream signal is an optical signal transmitted by the ONU to the OLT.

[0003] In PON systems, 1G (Giga) class systems, such as G-PON systems defined in the ITU-T G.984 series, are in widespread use, so systems that achieve transmission speeds of higher than this are required to coexist with 1G class systems on the same optical fiber network. As a result, there is a need for OLTs that can simultaneously accommodate ONUs of multiple rates (e.g., three or more types) including 1G class systems.

[0004] In order to accommodate ONUs with different rates, the optical transceiver implemented in the OLT must support multiple rates simultaneously. This is called an MPM (Multi-PON Module). However, in a PON system in which an MPM is introduced, the multiple supported transmission rates are not always in operation throughout the entire period of commercial use. Usually, immediately after the introduction of an MPM, only low-speed transmission rates (e.g., 1G) are used, and as the service period progresses, the number of ONUs that transmit and receive at low-speed transmission rates gradually decreases, while the number of ONUs that transmit and receive at high-speed transmission rates increases. Eventually, only ONUs that transmit and receive at high-speed transmission rates remain.

[0005] Patent Document 1 discloses a method for reducing power consumption of an MPM by shutting down the transmission and reception functions that support low-speed transmission rates within the MPM in a PON system that ultimately consists only of ONUs that transmit and receive at high-speed transmission rates. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-226693 A Summary of the Invention [Problem to be solved by the invention]

[0007] In conventional PON systems, when even one ONU of a specific rate is connected to an MPM, even if that rate is used infrequently, the transmission and reception functions for that rate within the MPM continue to operate in the same way as under normal circumstances, and therefore low power consumption cannot be achieved.

[0008] Therefore, one or more aspects of the present disclosure aim to save power by turning off the power of the part that performs a transmission / reception function when the transmission / reception function of a specific rate is not being used. [Means for solving the problem]

[0009] An optical line terminal according to an embodiment of the present disclosure includes a first transceiver connected to one or more first ONUs corresponding to a first transmission rate via optical fiber and performing optical communication with the one or more first ONUs, a second transceiver connected to one or more second ONUs corresponding to a second transmission rate different from the first transmission rate via optical fiber and performing optical communication with the one or more second ONUs, a power supply unit that supplies power, a first transceiver control unit that supplies power supplied from the power supply unit to the first transceiver and controls the first transceiver, and a second transmission / reception control unit that supplies the power received from the first transmission / reception unit to the second transmission / reception unit and controls the second transmission / reception unit; and a device control unit that, when the number of the one or more first ONUs becomes a predetermined number or less, causes the first transmission / reception control unit to stop supplying power to the first transmission / reception unit for a first period, thereby turning off the power of the first transmission / reception unit, and, when the number of the one or more second ONUs becomes a predetermined number or less, causes the second transmission / reception control unit to stop supplying power to the second transmission / reception unit for a second period, thereby turning off the power of the second transmission / reception unit. the first period is a period starting from the completion of data transmission by the one or more first ONUs to the first transceiver unit, and the second period is a period starting from the completion of data transmission by the one or more second ONUs to the second transceiver unit. It is characterized by: Effect of the Invention

[0011] According to one or more aspects of the present disclosure, when a transmission / reception function of a specific rate is not used, power saving can be achieved by turning off the power supply of the part that performs that transmission / reception function. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram illustrating a schematic configuration of an optical communication system according to first and second embodiments. [Diagram 2] FIG. 2 is a block diagram illustrating a schematic configuration of an OLT according to the first and second embodiments. [Diagram 3] 1A and 1B are block diagrams illustrating an example of a hardware configuration. [Figure 4]FIG. 4 is a sequence diagram illustrating an operation of the optical communication system in the first embodiment. [Diagram 5] FIG. 11 is a block diagram showing an example of the arrangement of an optical communication system according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Embodiment 1 FIG. 1 is a block diagram illustrating a schematic configuration of an optical communication system 100 according to the first embodiment. The optical communication system 100 includes an OLT 110 as an optical line terminal, and a G-PON ONU 150, an XG-PON ONU 160, and an XGS-PON ONU 170 which are multiple types of ONUs. Here, the OLT 110 is connected to the G-PON ONU 150 , the XG-PON ONU 160 , and the XGS-PON ONU 170 via a splitter 101 . In the first embodiment, three types of ONUs corresponding to different transmission rates are included in the optical communication system 100, but the types of ONUs are not limited to three.

[0014] The G-PON ONU 150 is an ONU that supports a transmission rate of 1 Gbps upstream and 2.5 Gbps downstream. The XG-PON ONU 160 is an ONU that supports a transmission rate of 2.5 Gbps upstream and 10 Gbps downstream. The XGS-PON ONU 170 is an ONU that supports a transmission rate of 10 Gbps upstream and 10 Gbps downstream.

[0015] The OLT 110 transmits an optical signal to the G-PON ONU 150, the XG-PON ONU 160, or the XGS-PON ONU 170. The optical signal transmitted from the OLT 110 to the G-PON ONU 150, the XG-PON ONU 160, or the XGS-PON ONU 170 is also called a downstream signal. Moreover, the optical signal transmitted from the G-PON ONU 150, the XG-PON ONU 160, or the XGS-PON ONU 170 to the OLT 110 is also called an upstream signal.

[0016] In the first embodiment, when there is an available timing for the G-PON ONU 150, XG-PON ONU 160, or XGS-PON ONU 170 to transmit an upstream signal to the OLT 110 due to the actual installation and commercial status of the optical fiber 102, the OLT 110 turns off the power of the part that performs the transmission and reception function of the transmission rate other than the ONU transmission rate that will be received from now on, and when the reception timing comes, turns on the power of the part that performs the transmission and reception function of that transmission rate again. In other words, in the first embodiment, the OLT 110 saves power by turning on the power of the part that performs the transmission and reception function corresponding to a specific transmission rate only at the timing when there is transmission and reception at that transmission rate. This will be described below.

[0017] FIG. 2 is a block diagram showing a schematic configuration of the OLT 110. As shown in FIG. The OLT 110 includes a transceiver 120 as an optical transmitting / receiving section, and an OLT function section 140 .

[0018] The transceiver 120 receives power from the OLT function unit 140 and transmits and receives optical signals in response to control from the OLT function unit 140 . The transceiver 120 includes a quadplexer 121 as a transmission / reception execution unit, a G-PON transmission control unit 127, a G-PON reception control unit 128, an XGS-PON transmission control unit 129, an XGS-PON reception control unit 130, an MCU (Main Control Unit) 131, and a TEC (ThermoElectric Cooler) circuit 132. The quadplexer 121 includes a G-PON transmitter 122, a G-PON receiver 123, an XGS-PON transmitter 124, and an XGS-PON receiver 126.

[0019] The G-PON transmitter 122 receives a drive current from the G-PON transmission control unit 127, converts an electrical signal indicating data from the G-PON transmission control unit 127 into an optical signal, and transmits the optical signal. The transmitted optical signal is received by the G-PON ONU 150 via the optical fiber 102.

[0020] The G-PON receiver 123 receives a voltage supply from the G-PON reception controller 128 , converts the optical signal received from the G-PON ONU 150 into an electrical signal, and transmits the electrical signal to the G-PON reception controller 128 .

[0021] The XGS-PON transmitter 124 receives a drive current from the XGS-PON transmission control unit 129, converts an electrical signal, which is data from the XGS-PON transmission control unit 129, into an optical signal, and transmits the optical signal. The transmitted optical signal is transmitted to the XG-PON ONU 160 and the XGS-PON ONU 170 via the optical fiber 102. The XGS-PON transmission unit 124 includes a TEC (ThermoElectric Cooler) 125, which is a thermoelectric cooler using a Peltier element.

[0022] The XGS-PON receiver 126 receives a voltage supply from the XGS-PON reception control unit 130 , converts the optical signals received from the XG-PON ONU 160 and the XGS-PON ONU 170 into electrical signals, and transmits the electrical signals to the XGS-PON reception control unit 130 .

[0023] Here, the G-PON transmitter 122 and the G-PON receiver 123 are connected to one or more GPON ONUs 150, which are first ONUs corresponding to the first transmission rate, via an optical fiber 102, and function as a first transceiver that performs optical communication with the one or more first ONUs. The first transmission rate here is 1 Gbps upstream and 2.5 Gbps downstream. Moreover, the XGS-PON transmitter 124 and the XGS-PON receiver 126 are connected to one or more second ONUs, the XG-PON ONU 160 or the XGS-PON ONU 170, which are compatible with a second transmission rate different from the first transmission rate, via the optical fiber 102, and function as a second transceiver that performs optical communication with the one or more second ONUs. The second transmission rate here is 2.5 Gbps upstream and 10 Gbps downstream, or 10 Gbps upstream and 10 Gbps downstream.

[0024] The G-PON transmission control unit 127 supplies a drive current to the G-PON transmission unit 122 and stops the supply of the drive current in accordance with instructions from the MCU 131 . In addition, the G-PON transmission control unit 127 provides the electrical signal Tx_Data from the OLT function unit 140 to the G-PON transmission unit 122 .

[0025] The G-PON reception control unit 128 supplies the voltage Vapd to the G-PON reception unit 123 and stops the supply of the voltage Vapd in accordance with instructions from the MCU 131 . Furthermore, the G-PON reception control unit 128 controls the amplitude of the electrical signal Rx_Data from the G-PON reception unit 123 so that it becomes a constant value, and transfers the controlled electrical signal to the OLT function unit 140 .

[0026] The XGS-PON transmission control unit 129 supplies a drive current to the XGS-PON transmission unit 124 and stops the supply of the drive current in accordance with an instruction from the MCU 131 . In addition, the XGS-PON transmission control unit 129 provides the electrical signal Tx_Data from the OLT function unit 140 to the XGS-PON transmission unit 124 .

[0027] The XGS-PON reception control unit 130 supplies the voltage Vapd to the XGS-PON reception unit 126 and stops the supply of the voltage Vapd in accordance with an instruction from the MCU 131 . Furthermore, the XGS-PON reception control unit 130 controls the amplitude of the electrical signal Rx_Data from the XGS-PON reception unit 126 so that it becomes a constant value, and transfers the controlled electrical signal to the OLT function unit 140 .

[0028] Here, the G-PON transmission control unit 127 and the G-PON reception control unit 128 supply power from the power supply unit 142 described later to the first transceiver unit, and function as a first transceiver control unit that controls the first transceiver unit. In addition, the XGS-PON transmission control unit 129 and the XGS-PON reception control unit 130 supply power from the power supply unit 142 to the second transceiver unit, and function as a second transceiver control unit that controls the second transceiver unit.

[0029] The MCU 131 communicates with the OLT function unit 140, the G-PON transmission control unit 127, the G-PON reception control unit 128, the XGS-PON transmission control unit 129, and the XGS-PON reception control unit 130 according to the I2C interface.

[0030] Then, in accordance with instructions from the OLT function unit 140, the MCU 131 causes the G-PON transmission control unit 127, the G-PON reception control unit 128, the XGS-PON transmission control unit 129, and the XGS-PON reception control unit 130 to turn the power of the G-PON transmission unit 122, the G-PON reception unit 123, the XGS-PON transmission unit 124, and the XGS-PON reception unit 126 on or off.

[0031] Furthermore, the MCU 131 turns on or off the power supply of the TEC circuit 132 by supplying or stopping the power supply to the TEC circuit 132 in accordance with an instruction from the OLT function unit 140. As a result, the operation of the TEC 125 controlled by the TEC circuit 132 is also stopped, and the power supply of the TEC 125 is turned off.

[0032] The TEC circuit 132 supplies current to the TEC 125 of the XGS-PON transmission unit 124, and controls the XGS-PON transmission unit 124 to maintain a constant temperature.

[0033] The OLT function unit 140 is a part that executes the overall operation of the OLT 110 . The OLT function unit 140 includes an OLT processing unit 141 and a power supply unit 142 .

[0034] The OLT processing unit 141 functions as a device control unit that controls the processing in the OLT 110 . For example, the OLT processing unit 141 provides data to be transmitted to the G-PON ONU 150 to the G-PON transmission control unit 127 , and causes the G-PON transmission control unit 127 to transmit the data to the G-PON ONU 150 via the G-PON transmission unit 122 . In addition, the OLT processing unit 141 receives data from the G-PON ONU 150 via the G-PON reception control unit 128 and processes the data.

[0035] Furthermore, the OLT processing unit 141 provides data to be transmitted to the XG-PON ONU 160 or the XGS-PON ONU 170 to the XGS-PON transmission control unit 129, and causes the XGS-PON transmission control unit 129 to transmit the data to the XG-PON ONU 160 or the XGS-PON ONU 170 via the XGS-PON transmission unit 124. In addition, the OLT processing unit 141 receives data from the XG-PON ONU 160 or the XGS-PON ONU 170 from the XGS-PON reception control unit 130, and processes the data.

[0036] The OLT function unit 140 also includes a power supply unit 142 that supplies power to each unit of the OLT 110 , and the OLT processing unit 141 controls the power supplied to each unit of the OLT 110 via the MCU 131 .

[0037] For example, when the number of G-PON ONUs 150 connected to the OLT 110 is equal to or less than a predetermined number, the OLT processing unit 141 determines that the frequency of communication with the G-PON ONUs 150 is low, and turns off the power to the G-PON transmitting unit 122 and the G-PON receiving unit 123, which are functional units that communicate with the G-PON ONUs 150, except for the period during which communication with the G-PON ONUs 150 is being performed and the period of preparation for communication with the G-PON ONUs 150.

[0038] Furthermore, when the number of XG-PON ONU160 and XGS-PON ONU170 connected to the OLT110 is equal to or less than a predetermined number, the OLT processing unit 141 determines that the frequency of communication between the XG-PON ONU160 and the XGS-PON ONU170 has decreased, and turns off the power of the XGS-PON transmitting unit 124 and the XGS-PON receiving unit 126, which are functional units that communicate with the XG-PON ONU160 or the XGS-PON ONU170, except for the period during which communication is being performed with the XG-PON ONU160 or the XGS-PON ONU170 and the preparation period for communication with the XG-PON ONU160 or the XGS-PON ONU170. In this case, the OLT processing unit 141 also turns off the power of the TEC circuit 132.

[0039] The power supply unit 142 supplies power to each component of the OLT 110 . For example, the power supply unit 142 supplies power to the G-PON transmission control unit 127, the G-PON reception control unit 128, the XGS-PON transmission control unit 129, the XGS-PON reception control unit 130, and the MCU 131.

[0040] The OLT processing unit 141 described above can be configured, for example, as shown in Fig. 3(A), by a memory 10 and a processor 11 such as a CPU (Central Processing Unit) that executes a program stored in the memory 10. Such a program may be provided through a network, or may be provided by being recorded on a recording medium. That is, such a program may be provided, for example, as a program product.

[0041] In addition, the OLT processing unit 141 can also be configured with a processing circuit 12 such as a single circuit, a composite circuit, a processor operated by a program, a parallel processor operated by a program, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), for example, as shown in FIG. 3(B).

[0042] As described above, the OLT processing unit 141 can be realized by a processing circuit network. Although not shown, the power supply unit 142 can be realized by a power supply circuit.

[0043] The G-PON transmitter 122, G-PON receiver 123, XGS-PON transmitter 124, XGS-PON receiver 126, G-PON transmission control unit 127, G-PON reception control unit 128, XGS-PON transmission control unit 129, XGS-PON reception control unit 130, MCU 131 and TEC circuit 132 can be configured, for example, by the processing circuit 12 shown in Figure 3 (B).

[0044] FIG. 4 is a sequence diagram for explaining the operation of the optical communication system 100 in the first embodiment. FIG. 4 shows an example in which a low-speed ONU, G-PON ONU 150, is gradually replaced with a high-speed ONU, XG-PON ONU 160 or XGS-PON ONU 170, and the number of G-PON ONUs 150 connected to the optical communication system 100 becomes less than a predetermined number (here, 2).

[0045] In other words, Figure 4 explains the operation of turning off the power to the part of the transceiver 120 that performs the low-speed optical transmission and reception function during times when communication is not taking place when the communication frequency of the low-speed ONU is low, and turning on the power only during times when communication is taking place and during the preparation time required to turn on the power.

[0046] First, the OLT processing unit 141 makes the transceiver 120 transmit a Discovery Gate frame in order to logically establish a link between the OLT 110 and the ONU (S10).

[0047] Specifically, the XGS-PON transmission control unit 129 or the G-PON transmission control unit 127 amplifies an electrical signal as a Discovery Gate frame, and then transmits the electrical signal to the XGS-PON transmission unit 124 or the G-PON transmission unit 122. The XGS-PON transmission unit 124 or the G-PON transmission unit 122 converts the received electrical signal into an optical signal, and transmits it to the ONU through the optical fiber 102. When an ONU with an unestablished link responds to this Discovery Gate frame within a certain period of time, a link is established. This certain period of time is called a Discovery window.

[0048] In this way, the OLT processing unit 141 periodically transmits a Discovery Gate frame to discover ONUs with which a link has not been established, and repeats the operation of establishing a link. This allows the OLT processing unit 141 to grasp the number of each type of ONUs that are connected.

[0049] When the G-PON ONU 150 receives the Discovery Gate frame, it transmits a Register Request frame within the Discovery window time (S11). The G-PON receiver 123 converts the optical signal, which is a Register Request frame, into an electrical signal, and the G-PON reception controller 128 receives the electrical signal from the G-PON receiver 123 and provides the electrical signal to the OLT processor 141. Thereafter, the processing in the OLT 110 when receiving a frame from the G-PON ONU 150 is similar.

[0050] By successfully receiving the Register Request frame, the OLT processing unit 141 discovers the G-PON ONU 150 and causes the G-PON transmission control unit 127 and the G-PON transmission unit 122 to transmit a Register frame (S12). The Register frame is a frame for assigning a Logical Link IDentifier (LLID) to the G-PON ONU 150.

[0051] Specifically, the G-PON transmission control unit 127 amplifies the electrical signal which is the Register frame, and then provides the electrical signal to the G-PON transmission unit 122, which converts the electrical signal into an optical signal and transmits it to the G-PON ONU 150 through the optical fiber 102. Thereafter, the processing in the OLT 110 when transmitting a frame to the G-PON ONU 150 is similar.

[0052] When the G-PON ONU 150 receives a Register frame, it checks this LLID, and thereafter becomes able to determine whether the data was sent to the ONU itself.

[0053] Next, the OLT processing unit 141 causes the G-PON transmission control unit 127 and the G-PON transmission unit 122 to transmit a Normal Gate frame (S13). The Normal Gate frame is a frame for notifying the G-PON ONU 150 of the transmission start time. This transmission start time is the time at which the G-PON ONU 150 is caused to start transmission.

[0054] Upon receiving the Normal Gate frame, the G-PON ONU 150 transmits a Register ACK frame at the transmission start time included in the Normal Gate frame (S14).

[0055] By receiving the Register ACK frame, the OLT processing unit 141 completes the registration of the LLID assigned to the G-PON ONU 150. As a result, a logical link is established between the OLT 110 and the G-PON ONU 150.

[0056] Then, the OLT processing unit 141 causes the G-PON transmission control unit 127 and the G-PON transmitting unit 122 to transmit a Normal Gate frame in order to notify the G-PON ONU 150 of the transmission start time (S15).

[0057] When the G-PON ONU 150 receives the Normal Gate frame, it transmits the amount of data stored in the device as a Report frame at the transmission start time included in the Normal Gate frame (S16). Here, the amount of data is also called the transmission request data amount.

[0058] The OLT processing unit 141 causes the G-PON transmission control unit 127 and the G-PON transmission unit 122 to transmit a Normal Gate frame in order to notify the transmission start time and band of the upstream signal (S17). The OLT processing unit 141 also stores the transmission suspension period RT of the G-PON ONU 150 in this Normal Gate frame. Furthermore, the OLT processing unit 141 instructs the MCU 131 to turn off the power supply of the G-PON transmission unit 122 and the G-PON reception unit 123 of the transceiver 120 during this transmission suspension period RT. The MCU 131, which has received such an instruction, instructs the G-PON transmission control unit 127 and the G-PON reception control unit 128 to stop the supply of power to the G-PON transmission unit 122 and the G-PON reception unit 123, thereby turning off the power supply thereof.

[0059] Here, the smaller the number of ONUs of a particular type connected, the longer the transmission suspension period RT. In the example of FIG. Specifically, if the transmission suspension period when one G-PON ONU150 is connected to the OLT110 is RT1 and the transmission suspension period when two G-PON ONU150 are connected to the OLT110 is RT2, then RT1 > RT2.

[0060] The G-PON ONU 150 transmits data at the transmission start time included in the Normal Gate frame (S18). Then, upon completion of transmission of the requested amount of data, the G-PON ONU 150 stops transmission and waits for the next assigned transmission start time. Here, after completing transmission at the transmission start time notified in the Normal Gate frame, the G-PON ONU 150 stops transmission for a transmission stop period RT until the next transmission start time is specified.

[0061] In addition, in the OLT 110, when reception of the amount of data requested to be transmitted in step S16 is completed, the MCU 131 turns off the power of the G-PON transmission control unit 127 and the G-PON reception control unit 128 during the transmission suspension period RT.

[0062] Next, the OLT processing unit 141 causes the G-PON transmission control unit 127 and the G-PON transmission unit 122 to transmit a Normal Gate frame to inform the G-PON ONU 150 of the transmission start time after the transmission suspension period RT has elapsed (S19). In this case, the OLT processing unit 141 instructs the MCU 131 to turn on the power of the G-PON transmission unit 122 and the G-PON reception unit 123 of the transceiver 120 after the transmission suspension period RT has elapsed. The MCU 131 that has received such an instruction instructs the G-PON transmission control unit 127 and the G-PON reception control unit 128 to resume the supply of power to the G-PON transmission unit 122 and the G-PON reception unit 123, thereby turning on the power.

[0063] Upon receiving the Normal Gate frame, the G-PON ONU 150 transmits the amount of data stored within the device itself as a Report frame at the transmission start time included in the Normal Gate frame (S20).

[0064] The OLT processing unit 141 causes the G-PON transmission control unit 127 and the G-PON transmitting unit 122 to transmit a Normal Gate frame to notify the upstream signal transmission start time and band (S21). The OLT processing unit 141 also stores the transmission suspension period RT of the G-PON ONU 150 in this Normal Gate frame. Furthermore, the OLT processing unit 141 instructs the MCU 131 to turn off the power of the G-PON transmitting unit 122 and the G-PON receiving unit 123 of the transceiver 120 during this transmission suspension period RT.

[0065] The G-PON ONU 150 transmits data at the transmission start time included in the Normal Gate frame (S22). Then, when the G-PON ONU 150 completes transmission of the requested amount of data, it stops transmission and waits for the next assigned transmission start time. Here, after completing transmission at the transmission start time notified in the Normal Gate frame, the G-PON ONU 150 stops transmission for a transmission stop period RT until the next transmission start time is specified.

[0066] In addition, in OLT 110, when reception of the amount of data requested to be transmitted in step S20 is completed, MCU 131 instructs G-PON transmission control unit 127 and G-PON reception control unit 128 to turn off the power to G-PON transmission unit 122 and G-PON reception unit 123 during the transmission suspension period RT.

[0067] Next, the OLT processing unit 141 causes the G-PON transmission control unit 127 and the G-PON transmission unit 122 to transmit a Normal Gate frame to inform the G-PON ONU 150 of the transmission start time after the transmission suspension period RT has elapsed (S23). In this case, the OLT processing unit 141 instructs the MCU 131 to turn on the power of the G-PON transmission unit 122 and the G-PON reception unit 123 of the transceiver 120 after the transmission suspension period RT has elapsed. The MCU 131, which has received such an instruction, causes the G-PON transmission control unit 127 and the G-PON reception control unit 128 to resume the supply of power to the G-PON transmission unit 122 and the G-PON reception unit 123, thereby turning on the power.

[0068] 4, the operation when the number of G-PON ONUs 150 connected to the OLT 110 becomes equal to or less than a predetermined number has been described, but the first embodiment is not limited to such an example. For example, when the number of XG-PON ONUs 160 and XGS-PON ONUs 170 connected to the OLT 110 becomes equal to or less than a predetermined number, the OLT processing unit 141 may turn off the power supply of the XGS-PON transmitting unit 124 and the XGS-PON receiving unit 126 by the same operation as in FIG.

[0069] As described above, when the number of one or more first ONUs falls below a predetermined number, the OLT processing unit 141 turns off the power supply to the first transceiver unit by causing the first transceiver control unit to stop supplying power to the first transceiver unit for a first period. In addition, when the number of one or more second ONUs becomes equal to or less than a predetermined number, the OLT processing unit 141 turns off the power supply to the second transceiver unit by causing the second transceiver control unit to stop supplying power to the second transceiver unit for a second period.

[0070] Here, the OLT processing unit 141 identifies the number of one or more first ONUs based on responses from one or more first ONUs to the Discovery Gate frame, and identifies the number of one or more second ONUs based on responses from one or more second ONUs to the Discovery Gate frame.

[0071] In addition, the first period is a period starting from the completion of data transmission by one or more first ONUs to the first transceiver unit, and the second period is a period starting from the completion of data transmission by one or more second ONUs to the second transceiver unit.

[0072] Then, the OLT processing unit 141 notifies one or more first ONUs of the first period by a Normal Gate frame so as not to perform communication during the first period. Also, the OLT processing unit 141 notifies one or more second ONUs of the second period by a Normal Gate frame so as not to perform communication during the second period.

[0073] Moreover, the smaller the number of one or more first ONUs, the longer the first period, and the smaller the number of one or more second ONUs, the longer the second period.

[0074] As described above, according to the first embodiment, the transceiver 120 only powers on the parts that execute the transmission and reception functions for the transmission rate in operation, thereby enabling power saving.

[0075] Embodiment 2 The optical transceivers installed in the OLT and ONU are classified into several classes according to the loss budget determined by the transmission loss and branching loss between the OLT and ONU. Specifically, ITU-T G.984.2 specifies that when the loss budget is 28 dB or less, the class is B+, and when the loss budget is 32 dB or less, the class is C+.

[0076] As the loss budget increases, the optical transmission power of both the OLT and ONU must be increased, and the optical receiving sensitivity of both the OLT and ONU must be increased, which increases the power consumption of the optical transceiver. On the other hand, even in an optical fiber network where C+ is required, not all ONUs are located in positions that require a C+ loss budget, and it is common for multiple ONUs to be located in positions that are below the 28 dB loss budget specified by B+.

[0077] In addition, immediately after the introduction of a high-speed ONU, if there is no high-speed ONU in the C+ area and there is only a high-speed ONU in the B+ area, the high-speed transmission and reception function in the transceiver will be set to a drive current setting value to achieve optical output power and receiving sensitivity equivalent to B+. On the other hand, when the introduction of high-speed ONUs has progressed sufficiently and there are no longer any low-speed ONUs in the C+ area, the low-speed transmission and reception function within the transceiver will have a drive current setting value to achieve optical output power and receiving sensitivity equivalent to B+.

[0078] In addition to the functions described in the first embodiment, the second embodiment achieves power saving by class adjustment according to the loss budget when the ONU is installed near the OLT or when the transmission loss and branch loss are small due to the MPMPON installation environment or commercial conditions. Furthermore, power saving is achieved by controlling the power supply of the TEC circuit.

[0079] As shown in FIG. 1, an optical communication system 200 according to the second embodiment includes an OLT 210, and a G-PON ONU 150, an XG-PON ONU 160, and an XGS-PON ONU 170 which are multiple types of ONUs. The G-PON ONU 150, the XG-PON ONU 160, and the XGS-PON ONU 170 in the second embodiment are similar to the G-PON ONU 150, the XG-PON ONU 160, and the XGS-PON ONU 170 in the first embodiment.

[0080] As shown in FIG. 2, the OLT 210 in the second embodiment includes a transceiver 220 as an optical transceiver unit, and an OLT function unit 240.

[0081] The transceiver 220 receives power from the OLT function unit 240 and transmits and receives optical signals under the control of the OLT function unit 240 . The transceiver 220 includes a quadplexer 121 , a G-PON transmission control unit 227 , a G-PON reception control unit 228 , an XGS-PON transmission control unit 229 , an XGS-PON reception control unit 230 , an MCU 231 , and a TEC circuit 132 .

[0082] The quadplexer 121 and the TEC circuit 132 of the transceiver 220 in the second embodiment are similar to the quadplexer 121 and the TEC circuit 132 of the transceiver 120 in the first embodiment.

[0083] The G-PON transmission control unit 227 performs the same processing as the G-PON transmission control unit 127 in the first embodiment, and also adjusts the drive current supplied to the G-PON transmission unit 122 according to instructions from the MCU 231 .

[0084] The G-PON reception control unit 228 performs the same processing as the G-PON reception control unit 128 in the first embodiment, and also adjusts the voltage Vapd supplied to the G-PON reception unit 123 according to instructions from the MCU 231.

[0085] The XGS-PON transmission control unit 229 performs the same processing as the XGS-PON transmission control unit 129 in the first embodiment, and also adjusts the drive current supplied to the XGS-PON transmission unit 124 according to instructions from the MCU 231 .

[0086] The XGS-PON reception control unit 230 performs the same processing as the XGS-PON reception control unit 130 in the first embodiment, and also adjusts the voltage Vapd supplied to the XGS-PON reception unit 126 according to instructions from the MCU 231 .

[0087] As in the first embodiment, the MCU 231 communicates with the OLT function unit 240, the G-PON transmission control unit 227, the G-PON reception control unit 228, the XGS-PON transmission control unit 229, and the XGS-PON reception control unit 230 according to the I2C interface.

[0088] Here, in embodiment 2, the MCU 231, in accordance with instructions from the OLT function unit 240, causes the G-PON transmission control unit 127 or the XGS-PON transmission control unit 129 to adjust the driving current supplied, and causes the G-PON reception control unit 128 or the XGS-PON reception control unit 130 to adjust the voltage supplied. Furthermore, the MCU 231 turns on or off the power supply of the TEC circuit 132 by supplying or stopping the supply of power to the TEC circuit 132 in accordance with an instruction from the OLT function unit 240 .

[0089] The OLT function unit 240 is a part that executes the overall operation of the OLT 110 . The OLT function unit 240 includes an OLT processing unit 241 and a power supply unit 142 . The power supply unit 142 of the OLT function unit 240 in the second embodiment is similar to the power supply unit 142 of the OLT function unit 140 in the first embodiment.

[0090] The OLT processing unit 241 controls the processing in the OLT 210 . The OLT processing unit 241 in the second embodiment performs the same processing as the OLT processing unit 141 in the first embodiment, and also adjusts the class of the ONU depending on the location where the ONU is installed, or the transmission loss and branch loss.

[0091] Specifically, in the optical communication system 200# shown in FIG. 5, when G-PON ONU150#1, XG-PON ONU160#1, and XGS-PON ONU170#1 are installed in a C+ area R1, and G-PON ONU150#2, XG-PON ONU160#2, and XGS-PON ONU170#2 are installed in a B+ area R2, the transceiver 220 of the OLT 210 is on standby with optical transmission power and optical receiving sensitivity corresponding to the requested C+ class.

[0092] Then, if the G-PON ONU150#1, XG-PON ONU160#1, and XGS-PON ONU170#1 installed in C+ area R1 are all removed due to a change in commercial conditions, or if the G-PON ONU150#1, XG-PON ONU160#1, and XGS-PON ONU170#1 are re-installed in B+ area R2, the distance between the OLT210 and the G-PON ONU150#1, XG-PON ONU160#1, and XGS-PON ONU170#1 will be shortened.

[0093] In such a case, the OLT processing unit 241 detects the distance to the connected ONU by executing a measurement sequence according to, for example, MPCP (Multi-Point Control Protocol) or the like. Then, when the OLT processing unit 241 determines that the connected ONU is not C+ class but B+ class, it instructs the MCU 231 to adjust the drive current applied to the XGS-PON transmitting unit 124 and the G-PON transmitting unit 122, and set the transmission power to the optimum B+ class. Also, the OLT processing unit 241 instructs the MCU 231 to adjust the voltage provided to the XGS-PON receiving unit 126 and the G-PON receiving unit 123, and change the receiving sensitivity to the optimum B+ class.

[0094] Furthermore, if the OLT processing unit 241 determines based on the response to the above-mentioned DISCOVERY GATE frame that the XGS-PON ONU 170 and the XG-PON ONU 160 are not installed, it instructs the MCU 231 to turn off the power to the XGS-PON transmitting unit 124 and also turn off the power to the TEC circuit 132.

[0095] As described above, in the second embodiment, the OLT processing unit 241 detects the distance to one or more first ONUs, performs a first classification process to classify each of the one or more first ONUs into one of a plurality of classes according to the loss budget, and adjusts the optical transmission power and optical receiving sensitivity of the first transceiver unit according to the result of the first classification process. In addition, the OLT processing unit 241 detects the distance to one or more second ONUs, performs a second classification process to classify each of the one or more second ONUs into one of a plurality of classes, and adjusts the optical transmission power and optical receiving sensitivity of the second transceiver unit according to the result of the second classification process.

[0096] Here, the second transmission rate is a rate faster than the first transmission rate. When one or more second ONUs are not connected to the second transceiver unit via optical fiber, the OLT processing unit 241 causes the second transceiver control unit to stop supplying power to the second transceiver unit, thereby turning off the power supply to the second transceiver unit.

[0097] In addition, the second transceiver unit is equipped with a temperature adjustment unit, TEC125, for adjusting the temperature of the second transceiver unit, and the OLT processing unit 241 also stops the operation of the temperature adjustment unit when turning off the power to the second transceiver unit.

[0098] As described above, the second embodiment is configured to control the class according to the loss budget, so it is possible to save power while adapting to the installation area. Also, the second embodiment can save power before upgrading to the 10G rate by turning off the power supply of the TEC circuit 132 depending on the type of ONU connected.

[0099] In the above-described first and second embodiments, the G-PON transmitter 122 and the G-PON receiver 123 that communicate with the G-PON ONU 150, and the XGS-PON transmitter 124 and the XGS-PON receiver 126 that communicate with the XG-PON 160 and the XGS-PON 170 are provided, but the first and second embodiments are not limited to such examples. For example, an XG-PON transmitter and an XG-PON receiver that communicate with the XG-PON 160 may be provided. In such a case, the XGS-PON transmitter 124 and the XGS-PON receiver 126 communicate with the XGS-PON 170 without communicating with the XG-PON 160. Then, when the number of connected XG-PON 160s is less than or equal to a predetermined number, the OLT processing unit 141, 241 turns off the power to the XG-PON transmitter unit and the XG-PON receiver unit, as described above, and when the number of connected XGS-PON 170s is less than or equal to a predetermined number, the OLT processing unit 141, 241 turns off the power to the XGS-PON transmitter unit 124 and the XGS-PON receiver unit 126, as described above. [Explanation of symbols]

[0100] 100,200 Optical communication system, 101 Splitter, 102 Optical fiber, 110,210 OLT, 120,220 Transmitter / receiver, 121 Quadplexer, 127,227 G-PON transmission control unit, 128,228 G-PON reception control unit, 129,229 XGS-PON transmission control unit, 130,230 XGS-PON reception control unit, 131,231 MCU, 132 TEC circuit, 140,240 OLT function unit, 141,241 OLT processing unit, 142 Power supply unit.

Claims

1. a first transceiver connected to one or more first ONUs corresponding to a first transmission rate via an optical fiber and performing optical communication with the one or more first ONUs; a second transceiver connected to one or more second ONUs corresponding to a second transmission rate different from the first transmission rate by an optical fiber and performing optical communication with the one or more second ONUs; a power supply unit that supplies power; a first transmission / reception control unit that supplies the power supplied from the power supply unit to the first transmission / reception unit and controls the first transmission / reception unit; a second transmission / reception control unit that supplies the power supplied from the power supply unit to the second transmission / reception unit and controls the second transmission / reception unit; a device control unit that, when the number of the one or more first ONUs becomes equal to or less than a predetermined number, causes the first transmission / reception control unit to stop supplying power to the first transmission / reception unit for a first period, thereby turning off the power of the first transmission / reception unit, and, when the number of the one or more second ONUs becomes equal to or less than a predetermined number, causes the second transmission / reception control unit to stop supplying power to the second transmission / reception unit for a second period, thereby turning off the power of the second transmission / reception unit; the first period is a period starting from completion of data transmission by the one or more first ONUs to the first transceiver unit, The second period is a period that starts from the completion of data transmission from the one or more second ONUs to the second transceiver. An optical line terminal comprising:

2. a first transceiver connected to one or more first ONUs corresponding to a first transmission rate via an optical fiber and performing optical communication with the one or more first ONUs; a second transceiver connected to one or more second ONUs corresponding to a second transmission rate different from the first transmission rate by an optical fiber and performing optical communication with the one or more second ONUs; a power supply unit that supplies power; a first transmission / reception control unit that supplies the power supplied from the power supply unit to the first transmission / reception unit and controls the first transmission / reception unit; a second transmission / reception control unit that supplies the power supplied from the power supply unit to the second transmission / reception unit and controls the second transmission / reception unit; a device control unit that, when the number of the one or more first ONUs becomes equal to or less than a predetermined number, causes the first transmission / reception control unit to stop supplying power to the first transmission / reception unit for a first period, thereby turning off the power of the first transmission / reception unit, and, when the number of the one or more second ONUs becomes equal to or less than a predetermined number, causes the second transmission / reception control unit to stop supplying power to the second transmission / reception unit for a second period, thereby turning off the power of the second transmission / reception unit; the device control unit notifies the one or more first ONUs of the first period by a Normal Gate frame so as not to perform communication during the first period, and notifies the one or more second ONUs of the second period by a Normal Gate frame so as not to perform communication during the second period. An optical line terminal comprising:

3. the first period is longer as the number of the one or more first ONUs is smaller; The second period is longer as the number of the one or more second ONUs is smaller.

3. The optical line terminal according to claim 1, wherein:

4. a first transceiver connected to one or more first ONUs corresponding to a first transmission rate via an optical fiber and performing optical communication with the one or more first ONUs; a second transceiver connected to one or more second ONUs corresponding to a second transmission rate different from the first transmission rate by an optical fiber and performing optical communication with the one or more second ONUs; a power supply unit that supplies power; a first transmission / reception control unit that supplies the power supplied from the power supply unit to the first transmission / reception unit and controls the first transmission / reception unit; a second transmission / reception control unit that supplies the power supplied from the power supply unit to the second transmission / reception unit and controls the second transmission / reception unit; a device control unit that, when the number of the one or more first ONUs becomes equal to or less than a predetermined number, causes the first transmission / reception control unit to stop supplying power to the first transmission / reception unit for a first period, thereby turning off the power of the first transmission / reception unit, and, when the number of the one or more second ONUs becomes equal to or less than a predetermined number, causes the second transmission / reception control unit to stop supplying power to the second transmission / reception unit for a second period, thereby turning off the power of the second transmission / reception unit; the device control unit performs a first classification process of classifying each of the one or more first ONUs into one of a plurality of classes according to a loss budget by detecting a distance from the one or more first ONUs, and adjusts an optical transmission power and an optical receiving sensitivity of the first transceiver unit according to a result of the first classification process; performs a second classification process of classifying each of the one or more second ONUs into one of the plurality of classes by detecting a distance from the one or more second ONUs, and adjusts an optical transmission power and an optical receiving sensitivity of the second transceiver unit according to a result of the second classification process. An optical line terminal comprising:

5. one or more first ONUs corresponding to a first transmission rate; one or more second ONUs corresponding to a second transmission rate different from the first transmission rate; The optical line terminal according to any one of claims 1, 2 and 4 is provided. An optical communication system comprising:

6. A first transceiver unit connected to one or more first ONUs corresponding to a first transmission rate via optical fiber and performing optical communication with the one or more first ONUs; a first transmission / reception control unit that supplies power supplied from a power supply unit that supplies power to the first transmission / reception unit and controls the first transmission / reception unit; and a device control unit that, when the number of the one or more first ONUs becomes equal to or less than a predetermined number, causes the first transmission / reception control unit to stop supplying power to the first transmission / reception unit for a first period, thereby turning off the power supply of the first transmission / reception unit; The first period is a period that starts from the completion of data transmission from the one or more first ONUs to the first transceiver. An optical line terminal comprising:

7. A first transceiver unit connected to one or more first ONUs corresponding to a first transmission rate via an optical fiber and performing optical communication with the one or more first ONUs; a first transmission / reception control unit that supplies power supplied from a power supply unit to the first transmission / reception unit and controls the first transmission / reception unit; and a device control unit that, when the number of the one or more first ONUs becomes equal to or less than a predetermined number, causes the first transmission / reception control unit to stop supplying power to the first transmission / reception unit for a first period, thereby turning off the power supply of the first transmission / reception unit; The device control unit notifies the one or more first ONUs of the first period by a Normal Gate frame so as not to perform communication during the first period. An optical line terminal comprising:

8. The first period is longer as the number of the one or more first ONUs is smaller.

8. The optical line terminal according to claim 6 or 7,

9. A first transceiver unit connected to one or more first ONUs corresponding to a first transmission rate via optical fiber and performing optical communication with the one or more first ONUs; a first transmission / reception control unit that supplies power supplied from a power supply unit to the first transmission / reception unit and controls the first transmission / reception unit; and a device control unit that, when the number of the one or more first ONUs becomes equal to or less than a predetermined number, causes the first transmission / reception control unit to stop supplying power to the first transmission / reception unit for a first period, thereby turning off the power supply of the first transmission / reception unit; the device control unit detects a distance from the one or more first ONUs, performs a first classification process for classifying each of the one or more first ONUs into one of a plurality of classes according to a loss budget, and adjusts an optical transmission power and an optical reception sensitivity of the first transceiver unit according to a result of the first classification process. An optical line terminal comprising:

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