Optical communication system and optical communication method

Abstract

This optical communication system includes, in an optical communication network for transmitting an optical signal in which a plurality of main signals are wavelength-division multiplexed, a first branching device and a second branching device that wavelength-demultiplex the optical signal into the plurality of main signals and multiplex the plurality of main signals, a first optical transceiver and a second optical transceiver that are connected to the first branching device, a third optical transceiver and a fourth optical transceiver that are connected to the second branching device, and an optical wavelength multiplexing switch that is connected to the first branching device via a first optical transmission path and is connected to the second branching device via a second optical transmission path, wherein the plurality of main signals have wavelengths selected from a specific wavelength grid.

Description

Optical Communication System and Optical Communication Method

[0001] The present disclosure relates to an optical communication system and an optical communication method. This application claims priority based on Japanese Patent Application No. 2024-191183 filed on October 30, 2024, and incorporates all of the disclosure thereof herein.

[0002] Patent Document 1 discloses a technique for allocating the wavelength of a wavelength-variable optical transceiver in an ONU (Optical Network Unit) of a PON (Passive Optical Network) using control signals such as an AMCC (Auxiliary Management and Control Channel) and an OAM (Operations, Administration, and Maintenance).

[0003] In recent years, an APN (All-Photonics Network) that performs optical communication within a network end-to-end has been developed. In the APN, a wavelength is allocated for each user device and application, and the communication path is controlled by the wavelength.

[0004] International Publication No. 2020 / 091396

[0005] An optical communication system according to one aspect of the present disclosure is an optical communication network that transmits an optical signal in which a plurality of main signals are wavelength-division multiplexed, comprising: a first branching device and a second branching device that wavelength-separate the optical signal into the plurality of main signals and multiplex the plurality of main signals; a first optical transceiver and a second optical transceiver connected to the first branching device; a third optical transceiver and a fourth optical transceiver connected to the second branching device; and an optical wavelength division multiplexing switch connected to the first branching device by a first optical transmission path and connected to the second branching device by a second optical transmission path, wherein the plurality of main signals are The first branching device has wavelengths selected from a specific wavelength grid and includes a first branch port connected to the first optical transceiver, a second branch port connected to the second optical transceiver, and a first trunk port connected to the optical wavelength division multiplexer switch. The second branching device includes a third branch port connected to the third optical transceiver, a fourth branch port connected to the fourth optical transceiver, and a second trunk port connected to the optical wavelength division multiplexer switch. The optical wavelength division multiplexer switch outputs the first main signal and the third main signal to the first optical transmission path. The first branching device outputs a second main signal and a fourth main signal to the second optical transmission line, wherein the first main signal is an optical signal of a first wavelength included in the first wavelength band, the second main signal is an optical signal of a second wavelength included in the first wavelength band but different from the first wavelength, the third main signal is an optical signal of a third wavelength included in the second wavelength band, the second wavelength band is different from the first wavelength band, and the fourth main signal is an optical signal of a fourth wavelength included in the second wavelength band but different from the third wavelength, and the first branching device receives an optical signal from the first trunk side port that is included in the first wavelength band. The first branch line port outputs an optical signal that is input from the first trunk line port and included in the second wavelength band to the second branch line port, the second branching device outputs an optical signal that is input from the second trunk line port and included in the first wavelength band to the third branch line port, and outputs an optical signal that is input from the second trunk line port and included in the second wavelength band to the fourth branch line port, the first optical transceiver receives the first main signal, the second optical transceiver receives the third main signal, and the third optical transceiver receives the second main signal.The fourth optical transceiver receives the fourth main signal.

[0006] Figure 1 is a diagram showing an example of the configuration of an optical communication system according to the embodiment. Figure 2 is a diagram showing an example of the configuration of an optical remote control system according to the embodiment. Figure 3 is a diagram showing an example of the hardware configuration of an optical branching device according to the embodiment. Figure 4 is a diagram showing an example of the hardware configuration of an optical transceiver. Figure 5A is a diagram showing an example of the relationship between the receiving wavelength assigned to the optical transceiver and the passband of the port for the downlink main signal in the optical branching device. Figure 5B is a diagram showing an example of the relationship between the transmitting wavelength assigned to the optical transceiver and the passband of the port for the uplink main signal in the optical branching device. Figure 6 is a sequence diagram showing an example of remote control of an optical transceiver in an optical remote system according to the embodiment. Figure 7 is a schematic diagram showing an example of downlink communication in an optical remote system according to the embodiment. Figure 8 is a schematic diagram showing an example of uplink communication in an optical remote system according to the embodiment. Figure 9A is a diagram showing a first example of setting the wavelength and transmission path of the main signal in an optical communication system according to the embodiment. Figure 9B is a diagram showing a second example of setting the wavelength and transmission path of the main signal in an optical communication system according to the embodiment. Figure 10 is a diagram showing a modified example of the configuration of the optical remote control system according to the embodiment. Figure 11 is a diagram showing a modified example of the hardware configuration of an optical branching device according to the embodiment.

[0007] In APNs, optical signals are combined and demultiplexed by optical branching devices, which are concentrators located within the optical communication network. From a power saving perspective, it is desirable that optical multiplexing couplers be passive devices that do not use power. However, in passive optical branching devices, a fixed wavelength band is assigned to each port, so the transmission wavelength at the optical transceiver (optical terminal) connected to the port cannot be changed. Furthermore, when multiple optical branching devices are arranged in parallel by branching from a single wavelength multiplexing / demultiplexing unit (Add / Drop), the wavelengths that are multiplexed and demultiplexed differ for each optical branching device, so the wavelength characteristics of each optical branching device must be different. For this reason, many types of optical branching devices are required.

[0008] According to this disclosure, it is possible to change the transmission wavelength in an optical transceiver within a certain range while reducing power consumption. Furthermore, the number of types of optical branching devices required can be reduced.

[0009] The embodiments of this disclosure are outlined below.

[0010] (1) The optical communication system according to this embodiment is an optical communication network that transmits an optical signal in which a plurality of main signals are wavelength-division multiplexed, and comprises a first branching device and a second branching device that wavelength-separate the optical signal into the plurality of main signals and multiplex the plurality of main signals, a first optical transceiver and a second optical transceiver connected to the first branching device, a third optical transceiver and a fourth optical transceiver connected to the second branching device, and an optical wavelength division multiplexing switch connected to the first branching device by a first optical transmission path and connected to the second branching device by a second optical transmission path, wherein the plurality of main signals are specific The wavelengths are selected from the wavelength grid, and the first branching device includes a first branch port connected to the first optical transceiver, a second branch port connected to the second optical transceiver, and a first trunk port connected to the optical wavelength division multiplexer switch, the second branching device includes a third branch port connected to the third optical transceiver, a fourth branch port connected to the fourth optical transceiver, and a second trunk port connected to the optical wavelength division multiplexer switch, and the optical wavelength division multiplexer switch outputs the first main signal and the third main signal to the first optical transmission path. The first branching device outputs the second main signal and the fourth main signal to the second optical transmission line, wherein the first main signal is an optical signal of the first wavelength included in the first wavelength band, the second main signal is an optical signal of the second wavelength included in the first wavelength band but different from the first wavelength, the third main signal is an optical signal of the third wavelength included in the second wavelength band, the second wavelength band is different from the first wavelength band, and the fourth main signal is an optical signal of the fourth wavelength included in the second wavelength band but different from the third wavelength, and the first branching device receives the optical signal input from the first trunk side port and included in the first wavelength band as The first branch line port outputs an optical signal that is input from the first trunk line port and included in the second wavelength band to the second branch line port, the second branching device outputs an optical signal that is input from the second trunk line port and included in the first wavelength band to the third branch line port, and outputs an optical signal that is input from the second trunk line port and included in the second wavelength band to the fourth branch line port, the first optical transceiver receives the first main signal, the second optical transceiver receives the third main signal, and the third optical transceiver receives the second main signal.The fourth optical transceiver receives the fourth main signal. This allows the first and second branching devices to be passive devices, with the first wavelength band assigned to the first branch port and the second wavelength band assigned to the second branch port, thereby reducing power consumption. Furthermore, the configurations of the first and second branching devices can be identical, reducing the number of branching device types.

[0011] (2) In (1) above, the first optical transceiver transmits a fifth main signal, the second optical transceiver transmits a sixth main signal, the fifth main signal is an optical signal of a fifth wavelength included in the third wavelength band, and the sixth main signal is an optical signal of a sixth wavelength included in a fourth wavelength band different from the third wavelength band, the first branching device outputs an optical signal input from the first branch port and included in the third wavelength band to the first optical transmission line from the first trunk port, and outputs an optical signal input from the second branch port and included in the fourth wavelength band to the first optical transmission line from the first trunk port, and the third The optical transceiver transmits a seventh main signal, the fourth optical transceiver transmits an eighth main signal, the seventh main signal is an optical signal of a seventh wavelength that is included in the third wavelength band and is different from the fifth wavelength, and the eighth main signal is an optical signal of an eighth wavelength that is included in the fourth wavelength band and is different from the sixth wavelength. The second branching device may output an optical signal input from the third branch port and included in the third wavelength band to the second optical transmission line from the second trunk port, and an optical signal input from the fourth branch port and included in the fourth wavelength band to the second optical transmission line from the second trunk port. This allows the first branching device and the second branching device to be passive devices, with the third wavelength band assigned to the first branch port and the fourth wavelength band assigned to the second branch port, thereby reducing power consumption. Furthermore, the configurations of the first branching device and the second branching device can be the same, reducing the number of branching device types. It becomes possible to change the transmission wavelengths of the first and third optical transceivers within the range of the third wavelength band, and to change the transmission wavelengths of the second and fourth optical transceivers within the range of the fourth wavelength band. Compared to the case where uplink multiplexing (the direction from the first, second, third, and fourth optical transceivers to the optical wavelength division multiplexing switch) is performed using optical couplers, it becomes possible to reduce the loss of optical signals.

[0012] (3) In (2) above, each of the first optical transmission path and the second optical transmission path is a single-core bidirectional optical transmission path, and each of the first wavelength band, the second wavelength band, the third wavelength band, and the fourth wavelength band may be different from each other. This makes it possible to make the first branching device and the second branching device passive devices of the same configuration even if each of the first optical transmission path and the second optical transmission path is a single-core bidirectional optical transmission path, thereby reducing the number of branching devices. Furthermore, it is possible to change the transmission wavelength in each of the first optical transceiver and the third optical transceiver within the range of the third wavelength band, and to change the transmission wavelength in each of the second optical transceiver and the fourth optical transceiver within the range of the fourth wavelength band, thereby reducing the loss of the uplink optical signal.

[0013] (4) In (2) above, the first optical transmission path and the second optical transmission path are each one-core bidirectional optical transmission paths, the first wavelength band and the third wavelength band are the same, the first wavelength, the second wavelength, the fifth wavelength and the seventh wavelength are different from each other, the second wavelength band and the fourth wavelength band are the same, and the third wavelength, the fourth wavelength, the sixth wavelength and the eighth wavelength may be different from each other. This simplifies the configuration of the optical branching devices by having the first optical branching device separate the first and third main signals in the downstream direction and combine the fifth and sixth main signals in the upstream direction using a common optical element, and the second optical branching device separate the second and fourth main signals in the downstream direction and combine the seventh and eighth main signals in the upstream direction using a common optical element.

[0014] (5) In any one of (1) to (4) above, at least one of the first branching device and the second branching device includes a plurality of optical filters that wavelength-multiplex the optical signal based on a reference wavelength, each of the plurality of optical filters includes a first terminal, a second terminal and a third terminal, wavelength-multiplex the optical signal input from the first terminal with a wavelength component lower than the reference wavelength and the optical signal input from the third terminal with a wavelength component higher than the reference wavelength, output the wavelength-multiplexed optical signal from the second terminal, separate the optical signal input from the second terminal with the reference wavelength, output the wavelength component lower than the reference wavelength from the first terminal and the wavelength component higher than the reference wavelength from the third terminal, and the reference wavelengths in each of the plurality of optical filters may be different from each other. The configuration of the optical branching device can be simplified by combining a plurality of optical filters with simple configurations.

[0015] (6) The optical communication method according to this embodiment is an optical communication network that transmits an optical signal obtained by wavelength division multiplexing of a plurality of main signals, comprising the steps of: an optical wavelength division multiplexing switch outputting a first main signal, which is an optical signal of a first wavelength included in a first wavelength band, to a first optical transmission path; the optical wavelength division multiplexing switch outputting a second main signal, which is an optical signal of a second wavelength included in the first wavelength band and different from the first wavelength, to a second optical transmission path; the optical wavelength division multiplexing switch outputting a third main signal, which is an optical signal of a third wavelength included in a second wavelength band different from the first wavelength band, to the first optical transmission path; the optical wavelength division multiplexing switch outputting a fourth main signal, which is an optical signal of a fourth wavelength included in the second wavelength band and different from the third wavelength, to the second optical transmission path; and a first branching device connected to the first optical transmission path outputting an optical signal input from a first trunk-side port connected to the first optical transmission path and included in the first wavelength band, to a first branch-side port; and the first branching device The process includes the steps of: outputting an optical signal input from a first trunk port and included in the second wavelength band to a second branch port; outputting an optical signal input from a second trunk port connected to the second optical transmission path and included in the first wavelength band to a third branch port; outputting an optical signal input from a second trunk port connected to the second optical transmission path and included in the first wavelength band to a fourth branch port; receiving a first main signal from a first optical transceiver connected to the first branch port; receiving a third main signal from a second optical transceiver connected to the second branch port; receiving a second main signal from a third optical transceiver connected to the third branch port; and receiving a fourth main signal from a fourth optical transceiver connected to the fourth branch port, wherein the plurality of main signals have wavelengths selected from a specific wavelength grid. As a result, the first branching device and the second branching device can each be made into passive devices in which the first branch line port is assigned the first wavelength band and the second branch line port is assigned the second wavelength band, thereby reducing power consumption.Furthermore, the configurations of the first and second branching devices can be the same, reducing the number of branching device types.

[0016] This disclosure can be achieved not only as an optical communication system having the characteristic configuration described above and as an optical communication method including characteristic steps, but also as an optical transceiver having the characteristic configuration or as an optical branching device having the characteristic configuration.

[0017] <Details of Embodiments of the Disclosure> Details of embodiments of the disclosure will be described below with reference to the drawings. At least some of the embodiments described below may be arbitrarily combined with at least some of the other embodiments.

[0018] [1. Optical Communication System] Figure 1 is a diagram showing an example of the configuration of an optical communication system according to the embodiment. The optical communication system 1 shown in Figure 1 connects each of a plurality of user devices 40 with an optical communication network 3 and transmits optical signals between the plurality of user devices 40 by wavelength division multiplexing. The optical communication system 1 includes optical wavelength division multiplexing switches 10A, 10B, 10C, and 10D, and a plurality of optical transceivers 30. Hereinafter, the optical wavelength division multiplexing switch will also be called "optical wavelength division multiplexing SW", and the optical wavelength division multiplexing switches 10A, 10B, 10C, and 10D will be collectively referred to as "optical wavelength division multiplexing SW 10".

[0019] The optical transceiver 30 is installed in the user device 40. The optical transceiver 30 is, for example, a pluggable module that can be attached to and detached from the user device 40. In Figure 1, one optical transceiver 30 is shown installed in one user device 40, but this is not the case. Multiple optical transceivers 30 may be installed in one user device 40.

[0020] The optical transceiver 30 includes an optical transceiver unit with a tunable transmission wavelength. The transmission wavelength of the optical transceiver unit is remotely controllable. The configuration of the optical transceiver 30 will be described later.

[0021] Each optical transceiver 30 is assigned a transmission wavelength. The optical transceiver 30 transmits an optical signal (main signal) of the assigned wavelength. For example, multiple optical transceivers 30 may each be assigned a different wavelength. Optical transceivers 30 whose transmission signals are not multiplexed may be assigned the same wavelength. For example, at least two or more optical transceivers 30 whose main signal transmission paths do not overlap may be assigned the same wavelength. The wavelength of the main signal is selected from a wavelength range excluding the wavelength used for control signals, which will be described later.

[0022] The user device 40 is located within the user's home or facility. The user device 40 may be, for example, a relay device such as a router for connecting the user's LAN (Local Area Network) to the optical communication network 3. As another example, the first user device 40 may be a Radio Unit (RU) in a mobile fronthaul (MFH), and the second user device 40, which is the counterpart device to the first user device, may be a Distributed Unit (DU).

[0023] Optical communication network 3 is an APN that transmits optical signals end-to-end. Optical communication network 3 includes, for example, a metro network 3A connected to a telecommunications carrier's base in a city, and an access network 3B connected to a user base (user's home or user's facility).

[0024] The optical wavelength division multiplexer (WDM) SW 10 is an optical gateway that connects the metro network 3A and the access network 3B and relays optical signals between the metro network 3A and the access network 3B. In the metro network 3A, the WDM SWs 10A, 10B, 10C, and 10D are interconnected by multiple optical transmission lines 60A, 60B, 60C, and 60D. The metro network 3A is a two-core transmission network, and the optical transmission lines 60A, 60B, 60C, and 60D are two-core optical transmission lines (the transmission directions of the two cores are opposite to each other). Hereafter, two-core optical transmission lines will also be referred to as "two-core transmission lines". For example, the metro network 3A is a ring topology network, and a specific example is a ROADM (Reconfigurable Optical Add / Drop Multiplexer). The configuration of the metro network 3A is not limited to this, and it may also be a mesh topology network. The optical transmission lines 61A, 61B, and 61C of the access network 3B are two-core transmission lines. Optical transmission lines 62AA, 62BA, 62CA, 62AB, 62BB, 62CB, 62AC, 62BC, and 62CC are two-core transmission lines. The entire access network 3B may be a network of single-core transmission lines, or a part of the access network 3B may be a network of single-core transmission lines, or a network of two-core transmission lines.

[0025] The following explanation will use the optical wavelength division multiplexer (WDM) SW10A as a representative example, but the WDM SW10B, 10C, and 10D are the same. The WDM SW10A is equipped with multiple ports on the metro network side (hereinafter also referred to as "metro-side ports") MP1 and MP2, and multiple ports on the access network side (hereinafter also referred to as "access-side ports") AP1, AP2, and AP3.

[0026] Each of the metro-side ports MP1 and MP2 includes an output interface and an input interface. The output interface of metro-side port MP1 is connected to the first transmission line of the two-core transmission line 60A (the transmission line from optical wavelength division multiplexing SW10A to optical wavelength division multiplexing SW10B). The input interface of metro-side port MP1 is connected to the second transmission line of the two-core transmission line 60A (the transmission line from optical wavelength division multiplexing SW10B to optical wavelength division multiplexing SW10A). The output interface of metro-side port MP2 is connected to the second transmission line of the two-core transmission line 60D (the transmission line from optical wavelength division multiplexing SW10A to optical wavelength division multiplexing SW10D). The input interface of metro-side port MP2 is connected to the first transmission line of the two-core transmission line 60D (the transmission line from optical wavelength division multiplexing SW10D to optical wavelength division multiplexing SW10A).

[0027] Each of the access-side ports AP1, AP2, and AP3 is connected to the optical branching device 20 (or optical transceiver 30) by optical transmission lines 61A, 61B, and 61C, respectively. As shown in Figure 1, one access-side port AP1 of the optical wavelength division multiplexer SW 10A is connected to the optical branching device (first branching device) 20AA via the optical transmission line 61A. In the example in Figure 1, the multiple optical branching devices 20 are assigned individual reference numerals 20AA, 20AB (second branching device), 20AC, 20B, 20C, and 20D depending on their location. Each of the optical branching devices 20AA, 20AB, and 20AC has the same configuration.

[0028] The optical transceivers 30 are connected to the optical branching device 20. In the example shown in Figure 1, multiple optical transceivers 30 are assigned individual codes 30XY (X = A, B, C, Y = A, B, C). X is the number of the optical transceiver 30 under one optical branching device 20, and Y is an index indicating the optical branching device 20 to which the optical transceiver 30 is connected. Optical branching device 20AA is connected to optical transceivers 30AA (second optical transceiver), 30BA (first optical transceiver), and 30CA respectively via two-core transmission lines 62AA, 62BA, and 62CA. Similarly, optical branching device 20AB is connected to optical transceivers 30AB (third optical transceiver), 30BB (fourth optical transceiver), and 30CB respectively via two-core transmission lines 62AB, 62BB, and 62CB. Optical branching device 20AC is connected to optical transceivers 30AC, 30BC, and 30CC via two-core transmission lines 62AC, 62BC, and 62CC. Furthermore, optical branching device 20B is connected to optical transceivers 30D, 30E, and 30F via two-core transmission lines. Optical branching device 20C is connected to optical transceivers 30G, 30H, and 30I via two-core transmission lines. Optical branching device 20D is connected to optical transceivers 30J, 30K, and 30L via two-core transmission lines.

[0029] Figure 2 shows an example of the configuration of an optical remote control system according to an embodiment. In Figure 2, an example of the configuration of optical remote control system 2A is shown as a representative example, but optical remote control systems 2B, 2C, and 2D are the same.

[0030] The optical wavelength division multiplexing switch (SW10A) includes an OLT function unit 11, a wavelength selection switch (hereinafter also referred to as "WSS") 14, a wavelength division multiplexing separation unit (hereinafter also referred to as "Add / Drop") 15, a SW control unit 12, a remote optical transceiver control unit 13 (hereinafter, "transceiver" is also referred to as "TRx"), and a control signal multiplexing unit 16.

[0031] WSS14 is connected to each metro-side port MP1 and MP2 by optical transmission lines, and is also connected to Add / Drop15 by optical transmission lines. Add / Drop15 is connected to each access-side port AP1, AP2, and AP3 by multiple optical transmission lines.

[0032] WSS14 determines whether to pass or drop the optical signal input to the input interface of metro-side port MP1 for each wavelength, and outputs the optical signals of the wavelengths to be passed to the output interface of metro-side port MP2. WSS14 outputs the optical signals of the wavelengths to be dropped to Add / Drop15. WSS14 determines whether to pass or drop the optical signal input to the input interface of metro-side port MP2 for each wavelength, and outputs the optical signals of the wavelengths to be passed to the output interface of metro-side port MP1. WSS14 outputs the optical signals of the wavelengths to be dropped to Add / Drop15.

[0033] WSS14 outputs the optical signals input from Add / Drop15 to either the output interface of metro-side port MP1 or the output interface of metro-side port MP2, wavelength by wavelength.

[0034] Add / Drop 15 separates the optical signal input from WSS 14 by wavelength and outputs the optical signal of each wavelength to access ports AP1, AP2, or AP3. Furthermore, Add / Drop 15 wavelength-multiplexes the optical signals input from access ports AP1, AP2, and AP3 and outputs the wavelength-division multiplexed signal (hereinafter also referred to as the "WDM signal") to WSS 14.

[0035] The control signal multiplexing unit 16 is located between the Add / Drop 15 and the access ports AP1, AP2, and AP3. The control signal multiplexing unit 16 wavelength-multiplexes the optical signal output from the Add / Drop 15 with control signals for controlling the optical transceiver 30. The control signal multiplexing unit 16 will be described later.

[0036] The optical branching device 20 separates the WDM signals transferred by the optical wavelength division multiplexer (WDM) switch 10 into wavelength-specific signals and transfers the separated optical signals to the corresponding optical transceivers 30 for each wavelength. The optical branching device 20 wavelength-multiplexes the optical signals transmitted from each optical transceiver 30 and transfers the resulting WDM signals to the optical wavelength division multiplexer (WDM) switch 10. The optical branching device 20 multiplexes or separates the optical signals within the device without converting them into electrical signals and transfers them to the desired path. Details of the optical branching device 20 will be described later.

[0037] The optical transceiver 30 and the optical wavelength division multiplexing switch 10 may be connected without an optical splitter 20. The optical transceiver 30 and the optical wavelength division multiplexing switch 10 may be connected via multiple optical splitters 20. In this case, one wavelength width multiplexed by the upper optical splitter 20 (closer to the optical wavelength division multiplexing switch 10) includes the wavelength range of the lower optical splitter 20 (closer to the optical transceiver 30). The optical splitter 20 may be an optical multiplexing coupler or a power coupler. In this case, since the optical transceiver 30 receives main signals of multiple wavelengths, the optical transceiver 30 further includes a wavelength selective filter for selecting and receiving only the corresponding wavelengths.

[0038] [2. Optical Remote Control System] Optical communication system 1 includes optical remote control systems 2A, 2B, 2C, and 2D. Optical remote control system 2A is a system for remotely controlling optical transceivers 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, and 30CC, and includes an optical wavelength division multiplexer SW 10A, optical branching devices 20AA, 20AB, and 20AC, and optical transceivers 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, and 30CC. Optical remote control systems 2B, 2C, and 2D have the same configuration as optical remote control system 2A. Hereinafter, optical remote control systems 2A, 2B, 2C, and 2D will be collectively referred to as "optical remote control system 2". Optical remote control system 2 may include a management device 50.

[0039] In the optical remote control system 2, the optical transceiver 30 is remotely controlled using TDM-PON (TDM: Time Division Multiplexing). Each of the optical wavelength division multiplexing switches 10 includes an OLT function unit (labeled "OLT" in Figure 1) 11.

[0040] Each of the optical transceivers 30 includes an ONU function unit (labeled "ONU" in Figure 1) 31.

[0041] The management device 50 centrally manages optical transceivers 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, 30CC, 30D, 30E, 30F, 30G, 30H, 30I, 30J, 30K, 30L. The management device 50 is communicably connected to each of the optical wavelength multiplexers SW10A, 10B, 10C, 10D via transmission paths 70A, 70B, 70C, 70D (shown by broken lines in the figure) using known technologies such as electrical signal lines, optical signal lines, and wireless networks. For example, the management device 50 and the optical wavelength multiplexers SW10A, 10B, 10C, 10D can communicate with each other using a communication protocol such as the Ethernet protocol (where "Ethernet" is a registered trademark). The management device is an example of a "remote control device".

[0042] The SW control unit 12 is connected to the management device 50 via the transmission path 70A. The SW control unit 12 is further connected to the remote optical TRx control unit 13. The SW control unit 12 can communicate with the management device 50 using a communication protocol such as the Ethernet protocol. The management device 50 transmits control information including the transmission path and wavelength of the optical signal, and the SW control unit 12 receives the control information from the management device 50. The control information includes information for setting the transmission wavelength of the optical transceiver 30.

[0043] The SW control unit 12 is composed of a processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), etc. The SW control unit 12 analyzes the received control information and sets the WSS14 and Add / Drop15 according to the transmission path and wavelength included in the control information.

[0044] The remote optical TRx control unit 13 is connected to the OLT function unit 11A. In FIG. 2, the optical connections between multiple elements are shown by solid lines, the electrical connections between multiple elements are shown by broken lines, and the connections regardless of the connection form (optical connection, electrical connection, etc.) between multiple elements are shown by dashed-dotted lines.

[0045] The remote optical transceiver control unit 13 is composed of a processor, an ASIC, an FPGA, etc. The remote optical transceiver control unit 13 can analyze the received control information and convert it into a control command for the optical transceiver 30.

[0046] The OLT function unit 11 is composed of a processor, an ASIC, an FPGA, etc., and includes an optical transceiver unit 111. Two or three of the SW control unit 12, the remote optical transceiver control unit 13, and the OLT function unit 11 may be composed of one processor, an ASIC, an FPGA, etc.

[0047] The OLT function unit 11 performs PON communication with a plurality of subordinate ONU function units 31 by using an optical signal of a predetermined control wavelength (hereinafter, also referred to as a "control signal"). Hereinafter, the direction from the optical wavelength division multiplexer SW10A (OLT function unit 11) to the optical transceivers 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, 30CC is referred to as the "downward direction", and the direction from the optical transceivers 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, 30CC to the optical wavelength division multiplexer SW10A (OLT function unit 11) is referred to as the "upward direction". The control wavelength is a wavelength different from the wavelength of the main signal. The control wavelength is, for example, 1490 nm as the transmission wavelength of the OLT function unit 11 (hereinafter, also referred to as the "downward control wavelength"), and 1310 nm as the reception wavelength of the OLT function unit 11 (hereinafter, also referred to as the "upward control wavelength").

[0048] The OLT function unit 11 communicates with each ONU function unit 31 individually and controls the subordinate optical transceivers 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, 30CC individually. Between the OLT function unit 11 and each ONU function unit 31, a multiplexed control signal, which is an optical signal in which control signals individually corresponding to each ONU function unit 31 are time-division multiplexed, is transmitted.

[0049] A control signal multiplexing unit 16 is located in the middle of the optical transmission path between Add / Drop 15 and access ports AP1, AP2, and AP3. In the example shown in Figure 2, the optical transmission paths 61A, 61B, and 61C are 2-core transmission paths, and the optical signals are handled as 2-core transmissions in WSS 14, Add / Drop 15, and the control signal multiplexing unit 16. Three sets of 2-core transmission paths 61A, 61B, and 61C extend from Add / Drop 15. Each of the 2-core transmission paths 61A, 61B, and 61C includes a downstream optical transmission path 61AA (first optical transmission path), 61BA (second optical transmission path), and 61CA (hereinafter also referred to as "downstream transmission path") and an upstream optical transmission path 61AB (first optical transmission path), 61BB (second optical transmission path), and 61CB (hereinafter also referred to as "upstream transmission path"). The control signal multiplexing unit 16 includes WDM couplers 16AA, 16BA, and 16CA positioned in the middle of each of the downlink transmission lines 61AA, 61BA, and 61CA, and WDM couplers 16AB, 16BB, and 16CB positioned in the middle of each of the uplink transmission lines 61AB, 61BB, and 61CB. Downlink multiplexed control signals output from the OLT function unit 11A are distributed to each branch line by optical couplers (power couplers) (not shown) positioned on the transmission lines extending from the optical transceiver unit 111. The WDM couplers 16AA, 16BA, and 16CA multiplex each of the distributed downlink multiplexed control signals with the downlink main signal transmitted through each of the downlink transmission lines 61AA, 61BA, and 61CA. Each of the two-core transmission lines 61A, 61B, and 61C extending from the control signal multiplexing unit 16 extends to the outside from the access side ports AP1, AP2, and AP3.

[0050] Wavelength division multiplexed signals (hereinafter also referred to as "downstream optical multiplexed signals") consisting of the downlink main signal and the downlink multiplexed control signal are output from the access-side ports AP1, AP2, and AP3 of the optical wavelength division multiplexing switch SW10A.

[0051] The configuration of optical branching device 20AA will be described below as representative, but the configurations of optical branching devices 20AB, 20AC, 20B, 20C, and 20D are the same. Optical branching device 20AA includes WDM couplers 21A, 21B, 22A, 22B, 24A1, 24A2, 24A3, 24B1, 24B2, and 24B3, and optical couplers 23A and 23B.

[0052] The optical branching device 20AA receives the downlink transmission line 61AA and the uplink transmission line 61AB of the two-core transmission line 61A. A WDM coupler 22A is placed in the middle of the downlink transmission line 61AA, and a WDM coupler 22B is placed in the middle of the uplink transmission line 61AB. The WDM coupler 22A separates the downlink main signal (WDM signals of three downlink main signals) and the downlink multiplexing control signal from the downlink optical multiplexed signal transmitted through the downlink transmission line 61AA. The downlink main signal is input to the WDM coupler 21A. The WDM coupler 21A separates the input downlink main signal by wavelength and distributes the separated main signals of each system to each branch line.

[0053] Each of the two-core transmission lines 62AA, 62BA, and 62CA includes downlink transmission lines 62AAA, 62BAA, and 62CAA, and uplink transmission lines 62ABA, 62BBA, and 62CBA. The downlink multiplexed control signals separated by the WDM coupler 22A are distributed to multiple systems by the optical coupler 23A. Each of the downlink transmission lines 62AAA, 62BAA, and 62CAA is equipped with a WDM coupler 24A1, 24A2, and 24A3. Each of the WDM couplers 24A1, 24A2, and 24A3 receives the downlink main signal output from the WDM coupler 21 and the downlink multiplexed control signals output from the optical coupler 23A. Each of the WDM couplers 24A1, 24A2, and 24A3 combines the input downlink main signal and downlink multiplex control signal and outputs it as a WDM signal (optical multiplex signal).

[0054] The optical transceiver 30BA includes an optical transmitting / receiving unit for the main signal (hereinafter also referred to as "U-TRx") 301 and an optical transmitting / receiving unit for the control signal (hereinafter also referred to as "C-TRx") 311. The U-TRx 301 is a tunable optical transmitting / receiving unit. More specifically, the U-TRx 301 includes a tunable optical transmitter and an optical receiver capable of receiving optical signals of a specific range of wavelengths. The C-TRx 311 includes an optical transmitter capable of transmitting an uplink optical signal for control and an optical receiver capable of receiving an downlink optical signal for control.

[0055] The optical transceiver 30BA includes a port (first branch line port) PA for receiving optical signals and a port (first branch line port) PB for transmitting optical signals. WDM couplers 304A and 304B are positioned along the optical transmission paths extending from ports PA and PB, respectively.

[0056] The downlink WDM signal output from the optical branching device 20AA and transmitted through the downlink transmission path 62BAA is input to the WDM coupler 304A from port PA of the optical transceiver 30BA. The WDM coupler 304A separates the downlink WDM signal into a downlink main signal and a downlink multiplexed control signal. The downlink main signal output from the WDM coupler 304B is received by U-TRx301, and the downlink multiplexed control signal output from the WDM coupler 304B is received by C-TRx311.

[0057] Optical transceiver 30BA acquires a control signal (frame) addressed to its own device from the downlink multiplexed control signal and executes the command contained in the control signal. C-TRx311 transmits an uplink control signal carrying the frame containing the execution result. Optical transceivers 30AA, 30BA, and 30CA each transmit frames at different timings. The uplink main signal transmitted from U-TRx301 and the uplink control signal transmitted from C-TRx311 are input to WDM coupler 304B. WDM coupler 304B combines the uplink main signal and the uplink control signal and outputs an uplink WDM signal. The uplink WDM signal is output from port PB to the uplink transmission line 62BBA.

[0058] Within the optical branching device 20AA, WDM couplers 24B1, 24B2, and 24B3 are arranged on each of the uplink transmission lines 62ABA, 62BBA, and 62CBA, respectively. Uplink WDM signals transmitted on each of the uplink transmission lines 62ABA, 62BBA, and 62CBA are input to each of the WDM couplers 24B1, 24B2, and 24B3. Each of the WDM couplers 24B1, 24B2, and 24B3 separates the uplink main signal and the uplink control signal from the uplink WDM signal. Each of the three uplink main signals is input to the WDM coupler 21B. The WDM coupler 21B combines the three input uplink main signals and outputs the WDM signal to the single-core transmission line 61A.

[0059] The three uplink control signals output from WDM couplers 24B1, 24B2, and 24B3 are input to optical coupler 23B. Optical coupler 23B multiplexes the three input uplink control signals. As described above, since frames are transmitted at different timings from optical transceivers 30AA, 30BA, and 30CA, the three uplink control signals are time-division multiplexed in optical coupler 23B.

[0060] The WDM coupler 22B combines the uplink WDM signal output from the WDM coupler 21 with the uplink multiplexing control signal (TDM signals of three control signals) output from the optical coupler 23B, and outputs a wavelength division multiplexed signal (hereinafter also referred to as the "uplink optical multiplexed signal") which is a combination of the three main WDM signals and the uplink multiplexing control signal. The uplink optical multiplexed signal is transmitted through the uplink transmission path 61AB of the two-core transmission path 61A and input to the access-side port AP1 of the optical wavelength division multiplexing switch 10A. Similarly, the uplink optical multiplexed signal transmitted through the uplink transmission path 61BB is input to the access-side port AP2, and the uplink optical multiplexed signal transmitted through the uplink transmission path 61CB is input to the access-side port AP3.

[0061] The control signal multiplexing unit 16 separates the uplink optical multiplexed signals transmitted through the uplink transmission lines 61AB, 61BB, and 61CB into an uplink main signal and an uplink multiplexed control signal using WDM couplers 16AB, 16BB, and 16CB, respectively. The uplink multiplexed control signals output from the WDM couplers 16AB, 16BB, and 16CB are multiplexed by an optical coupler (not shown) and input to the OLT function unit 11. The OLT function unit 11 extracts the command execution result from the uplink multiplexed control signal and outputs the extracted command execution result to the remote optical TRx control unit 13. The remote optical TRx control unit 13 generates response information including the command execution result. The remote optical TRx control unit 13 outputs the response information to the SW control unit 12. The SW control unit 12 transmits the input response information to the management device 50 either as is or together with the response to the setting commands for WSS 14 and Add / Drop 15.

[0062] [3. Optical Branching Device] Figure 3 shows an example of the hardware configuration of an optical branching device according to an embodiment.

[0063] The optical branching device 20AA includes a trunk-side down port (first trunk-side port) P21A, a trunk-side up port (first trunk-side port) P21B, branch-side down ports P22AA, P22BA, P22CA, and branch-side up ports P22AB, P22BB, P22CB. A trunk-side port is a port in the optical branching device 20 for transmitting and receiving optical signals from or to the metro network 3A. A branch-side port is a port for transmitting and receiving optical signals from or to the optical transceiver 30 without going through the metro network 3A. Downbound port P21A and upbound port P21B are examples of "main line side ports," while downbound ports P22AA, P22BA, P22CA and upbound ports P22AB, P22BB, P22CB are examples of "branch line side ports."

[0064] Downlink port P21A is a port for connecting downlink transmission lines, and uplink port P21B is a port for connecting uplink transmission lines. Downlink port P21A is connected to downlink transmission line 61AA extending from optical wavelength division multiplexing switch SW10A, and uplink port P21B is connected to uplink transmission line 61AB.

[0065] The following explanation will use ports P22AA and P22AB as representative examples, but ports P22BA and 3A are the same as port P22AA, and ports P22BB and P22CB are the same as port P22AB. Ports P22AA and P22AB are a pair of ports for connecting a two-core transmission line. Downlink port P22AA is an optical signal output port, and uplink port P22AB is an optical signal input port. Downlink transmission line 62AAA is connected to downlink port P22AA, and uplink transmission line 62ABA is connected to uplink port P22AB.

[0066] The WDM coupler 21A is used to separate the WDM signal into three downstream main signals. The WDM coupler 21B is used to wavelength multiplex the three upstream main signals. The WDM coupler 21A includes multilayer filters 21AA, 21BA, and 21CA. The WDM coupler 21B includes multilayer filters 21AB, 21BB, and 21CB.

[0067] Each of the multilayer filters 21AA, 21BA, 21CA, 21AB, 21BB, and 21CB is a filter for wavelength division multiplexing and separation based on a specific wavelength (hereinafter also referred to as the "reference wavelength"). The multilayer filter has three terminals. In Figure 3, the first terminal is represented as "1", the second terminal as "2", and the third terminal as "3". The multilayer filter can wavelength-multiplex the optical signal input from the first terminal with wavelength components lower than the reference wavelength fc and the optical signal input from the third terminal with wavelength components higher than the reference wavelength fc, and output the wavelength-multiplexed optical signal from the second terminal. The multilayer filter can also separate the optical signal input from the second terminal at the reference wavelength fc, outputting the wavelength components lower than the reference wavelength fc from the first terminal and the wavelength components higher than the reference wavelength fc from the third terminal. The WDM couplers 21A and 21B may be equipped with any optical filter having the same wavelength division multiplexing and separation function as described above, instead of the multilayer filter.

[0068] The WDM coupler 22A and the second terminal of the multilayer filter 21AA are connected via an optical transmission path. The third terminal of the multilayer filter 21AA and the second terminal of the multilayer filter 21BA are connected via an optical transmission path. The third terminal of the multilayer filter 21BA and the second terminal of the multilayer filter 21CA are connected via an optical transmission path.

[0069] The first terminal of the multilayer filter 21AA is connected to the WDM coupler 24A1 via an optical transmission path. The WDM coupler 24A1 is connected to the downlink port P22AA via an optical transmission path. The connection relationships from the multilayer filter 21BA to the downlink port 22BA, and from the multilayer filter 21CA to the downlink port P22CA are the same, so their explanation is omitted.

[0070] The second terminal of the multilayer filter 21CB and the third terminal of the multilayer filter 21BB are connected via an optical transmission path. The second terminal of the multilayer filter 21BB and the third terminal of the multilayer filter 21AB are connected via an optical transmission path. The second terminal of the multilayer filter 21AB and the WDM coupler 22B are connected via an optical transmission path.

[0071] The first terminal of the multilayer film filter 21AB is connected to the WDM coupler 24B1 via an optical transmission path. The WDM coupler 24B1 is connected to the uplink port P22AB via an optical transmission path. The uplink transmission path 62ABA is connected to the uplink port P22AB. The connection relationships from the multilayer film filter 21BB to the uplink port P22BB and from the multilayer film filter 21CB to the uplink port P22CB are the same, so their explanation is omitted.

[0072] Each of the multilayer filters 21AA, 21BA, and 21CA has its own reference wavelengths fcA1, fcA2, and fcA3, respectively, where fcA1 < fcA2 < fcA3. The WDM signal of the downstream main signal output from the WDM coupler 22A is input to the second terminal of the multilayer filter 21AA. The multilayer filter 21AA separates the WDM signal at the reference wavelength fcA1 and outputs the wavelength component lower than the reference wavelength fcA1 (the first downstream main signal) from the first terminal.

[0073] The third terminal of the multilayer filter 21AA outputs an optical signal with a wavelength higher than the reference wavelength fcA1. The optical signal output from the third terminal of the multilayer filter 21AA is input to the second terminal of the multilayer filter 21BA. The multilayer filter 21BA separates the optical signal input from the second terminal at the reference wavelength fcA2 and outputs the wavelength component lower than the reference wavelength fcA2 (the second downstream main signal) from the first terminal.

[0074] An optical signal with a wavelength higher than the reference wavelength fcA2 is output from the third terminal of the multilayer filter 21BA. The optical signal output from the third terminal of the multilayer filter 21BA is input to the second terminal of the multilayer filter 21CA. The multilayer filter 21CA separates the optical signal input from the second terminal at the reference wavelength fcA3 and outputs the wavelength component lower than the reference wavelength fcA3 (the first downstream main signal) from the first terminal. Alternatively, the third terminal of the multilayer filter 21BA and the WDM coupler 24A3 may be connected via an optical transmission path without providing the multilayer filter 21CA.

[0075] Each of the multilayer film filters 21AB, 21BB, and 21CB has its own individual reference wavelengths fcB1, fcB2, and fcB3, where fcB1 < fcB2 < fcB3.

[0076] The uplink main signal (having a wavelength lower than the reference wavelength fcB1) transmitted from the optical transceiver 30AA is input to the first terminal of the multilayer film filter 21AB via the WDM coupler 24B1.

[0077] Similarly, the uplink main signal transmitted from the optical transceiver 30BA (having a wavelength higher than the reference wavelength fcB1 and lower than the reference wavelength fcB2) is input to the first terminal of the multilayer film filter 21BB via the WDM coupler 24B2.

[0078] The uplink main signal transmitted from the optical transceiver 30CA (having a wavelength higher than the reference wavelength fcB2 and lower than the reference wavelength fcB3) is input to the first terminal of the multilayer film filter 21CB via the WDM coupler 24B3.

[0079] No optical signal is input to the third terminal of the multilayer filter 21CB. The multilayer filter 21CB outputs wavelength components of the optical signal input from the first terminal that are lower than the reference wavelength fcB3 from the second terminal.

[0080] The optical signal output from the second terminal of the multilayer filter 21CB is input to the third terminal of the multilayer filter 21BB. The multilayer filter 21BB wavelength-multiplexes the optical signal input from the first terminal with the wavelength component lower than the reference wavelength fcB2 and the optical signal input from the third terminal with the wavelength component higher than the reference wavelength fcB2, and outputs the wavelength-multiplexed optical signal from the second terminal.

[0081] The optical signal output from the second terminal of the multilayer filter 21BB is input to the third terminal of the multilayer filter 21AB. The multilayer filter 21AB wavelength-multiplexes the wavelength component of the optical signal input from the first terminal that is lower than the reference wavelength fcB1 and the wavelength component of the optical signal input from the third terminal that is higher than the reference wavelength fcB1, and outputs the wavelength-multiplexed optical signal (WDM signal of the three upstream main signals) from the second terminal. Alternatively, the WDM coupler 24B3 and the third terminal of the multilayer filter 21BB may be connected via an optical transmission path without providing the multilayer filter 21CB.

[0082] [4. Optical Transceiver] Figure 4 shows an example of the hardware configuration of an optical transceiver.

[0083] In addition to the ONU function unit 31, U-TRx 301, and C-TRx 311 described above, the optical transceiver 30 includes a microcontroller unit (MCU) 32, a drive circuit 302 for the U-TRx 301, and a digital signal processor (DSP) 303.

[0084] The DSP 303 is connected to the input / output terminals of the main signal (electrical signal) of the user device 40. The DSP 303 performs signal processing such as frame processing on the upstream main signal output from the output terminal of the user device 40.

[0085] The output terminal of the DSP 303 is connected to the input terminal of the drive circuit 302. The drive circuit 302 is connected to the U-TRx 301 and drives and controls the optical transmitter of the U-TRx 301 according to the electrical signal output from the DSP 303. As a result, the U-TRx 301 outputs an optical signal corresponding to the electrical signal output by the DSP 303.

[0086] The U-TRx301 optical receiver converts optical signals into electrical signals.

[0087] The DSP's input terminal is connected to the U-TRx301's optical receiver, and the electrical signal (downlink main signal) output from the U-TRx301 is input to the DSP303. The DSP303 performs signal processing, such as frame processing, on the downlink main signal output from the U-TRx301. The downlink main signal processed by the DSP303 is output from the DSP303 to the input terminal of the user device.

[0088] The C-TRx311 is connected to an LDD (Laser Diode Driver) / LA (Limiting Amplifier), which is not shown in the diagram. More specifically, the optical transmitter of the C-TRx311 is connected to the LDD, and the optical receiver is connected to the LA.

[0089] The C-TRx311 optical receiver converts optical signals (downlink multiplexed control signals) into electrical signals.

[0090] The electrical signal output from the optical receiver is input to the ONU function unit 31.

[0091] The ONU function unit 31 is configured, for example, by an FPGA. The FPGA constituting the ONU function unit 31 includes a circuit that functions as a frame processing unit 313, a processor 314, and a memory 315.

[0092] The frame processing unit 313 performs frame processing on the downlink multiplex control signal represented by the electrical signal input from the C-TRx 311. The frame processing unit 313 is a MAC (Media Access Control) circuit for PON and can generate PON frames as defined in IEEE 802.3ah, and can acquire information from PON frames. More specifically, the frame processing unit 313 can generate and process OAM frames for PON. In a concrete example, the frame processing unit 313 can handle OAM frames for PON.

[0093] The frame processing unit 313 extracts (acquires) the downlink control signal addressed to its own device from the downlink multiplex control signal, and more specifically, the frame addressed to its own device.

[0094] The frame processing unit 313 acquires control information from the extracted frames. The frame processing unit 313 is connected to the processor 314, which is connected to the memory 315. The frame processing unit 313 outputs the acquired control information to the processor 314.

[0095] The MCU 32 includes a processor 321, a memory 322, a digital-to-analog converter (DAC) 323, and an analog-to-digital converter (ADC) 324. The processor 321 functions as a control unit 330. The processor 314 of the ONU function unit 31 outputs control information input from the frame processing unit 313 to the processor 321 (control unit 330). The control unit 330 converts the control information into instructions. The control unit 330 executes the obtained instructions and obtains the execution results.

[0096] The control unit 330 can read the value of a specified register. The registers that the control unit 330 can read and write to are mapped centrally, but this mapping may be to a single memory (for example, memory 322) or to multiple memories. For example, the first area of ​​the register may be composed of memory 322, and the second area may be composed of memory within U-TRx301. When the control unit 330 receives a command to read the value of a specified register, it reads the value from the specified register. As a result of executing the command, the control unit 330 outputs the read value to the processor 314.

[0097] The control unit 330 is capable of writing a specified value to a specified register. When a write command for a specified register is given to the control unit 330, it writes the specified value to the specified register. As a result of executing the command, the control unit 330 outputs the written value to the processor 314 (echo back).

[0098] For example, when the control unit 330 writes a value to a register for controlling the wavelength of the U-TRx301, it outputs the written value (digital value) to the DAC 323 and DSP 303. The DAC 323 is connected to the U-TRx301 and the drive circuit 302. The DAC 323 and DSP 303 are used to configure the U-TRx301. The DSP 303 sets the modulation scheme of the U-TRx301 according to the input digital value. The DAC 323 converts the input digital value into an analog value and outputs the analog value to the U-TRx301. The U-TRx301 sets the output wavelength (transmission wavelength), cross point, and electrical signal amplitude of the optical transmitter according to the input analog value. The cross point is the point where the waveform of the optical signal changes between 0 and 1. The electrical signal amplitude is the amplitude of the electrical signal that is converted into an optical signal in the U-TRx301.

[0099] The ADC 324 is connected to the U-TRx 301 and the drive circuit 302. For example, when the control unit 330 writes a value to a register for monitoring the temperature of the U-TRx 301, the voltage (analog value) of the thermistor circuit for temperature measurement of the U-TRx 301 is read by the ADC 324 and output as a digital value. The control unit 330 calculates the temperature from the read voltage and outputs the calculation result to the frame processing unit 313. This allows the management device 50 to monitor the temperature of the U-TRx 301.

[0100] The processor 314 receives the instruction execution result output from the control unit 330 and outputs the received instruction execution result to the frame processing unit 313.

[0101] The frame processing unit 313 generates a frame containing the instruction execution result. The frame processing unit 313 outputs the generated frame to the LDD as a downlink control signal (voltage signal).

[0102] The LDD converts the voltage signal into a current signal and outputs the resulting current signal to the C-TRx311 optical transmitter. This drives the laser of the optical transmitter, and a burst optical signal corresponding to the current signal is output (transmitted).

[0103] [5. Wavelength Setting for Optical Transceivers] Figure 5A shows an example of the relationship between the receiving wavelength assigned to the optical transceiver and the passband of the port for the downlink main signal in the optical splitter.

[0104] In Figure 5A, the horizontal axis represents wavelength. In Figure 5A, Rλ1AA represents the wavelength band of the optical signal output from the first terminal of the multilayer filter 21AA, Rλ2AA represents the wavelength band of the optical signal output from the first terminal of the multilayer filter 21BA, and Rλ3AA represents the wavelength band of the optical signal output from the first terminal of the multilayer filter 21CA. As shown in Figure 5A, the wavelength bands Rλ1AA, Rλ2AA, and Rλ3AA are all different from each other. More specifically, the wavelength band of Rλ2AA is higher than that of Rλ1AA, and the wavelength band of Rλ3AA is higher than that of Rλ2AA. The boundary between the wavelength bands Rλ1AA and Rλ2AA is the reference wavelength fcA1, the boundary between the wavelength bands Rλ2AA and Rλ3AA is the reference wavelength fcA2, and the upper limit of the wavelength band Rλ3AA is the reference wavelength fcA3. The frequency bands Rλ1AA, Rλ2AA, and Rλ3AA are, for example, included in the C-band (Conventional-band, wavelength band from 1530 nm to 1565 nm).

[0105] The bandwidth Rλ1AA includes wavelengths λ11AA, λ12AA, and λ13AA. Wavelengths λ11AA, λ12AA, and λ13AA are distinct from each other. More specifically, wavelength λ12AA is higher than wavelength λ11AA, and wavelength λ13AA is higher than wavelength λ12AA. Wavelengths λ11AA and λ12AA are separated by a constant wavelength interval, and wavelengths λ12AA and λ13AA are separated by the same wavelength interval. Specifically, each of wavelengths λ11AA, λ12AA, and λ13AA is a wavelength channel of a 100 GHz grid (wavelength interval of 0.8 nm). It is not limited to a 100 GHz grid; for example, each of wavelengths λ11AA, λ12AA, and λ13AA may be a wavelength channel of a 50 Hz grid. The 100 GHz grid and the 50 Hz grid are examples of wavelength grids. A wavelength grid in WDM technology refers to a range of wavelengths divided at regular intervals, with each wavelength range being used as a single wavelength channel.

[0106] The bandwidth R1AA is a wavelength band capable of accommodating three wavelength channels of a 100 GHz grid. In a specific example, bandwidth R1AA is the wavelength band of a 300 GHz grid and has a wavelength width of 2.4 nm. The number of wavelength channels accommodated in bandwidth R1AA is not limited to three; it may be two or four or more.

[0107] The bandwidth Rλ2AA includes wavelengths λ21AA, λ22AA, and λ23AA, and the bandwidth Rλ3AA includes wavelengths λ31AA, λ32AA, and λ33AA. The relationship between bandwidth Rλ2AA and wavelengths λ21AA, λ22AA, and λ23AA, and the relationship between bandwidth Rλ3AA and wavelengths λ31AA, λ32AA, and λ33AA are the same as the relationship between bandwidth Rλ1AA and wavelengths λ11AA, λ12AA, and λ13AA described above, so the explanation is omitted.

[0108] Optical transceiver 30AA can receive optical signals of any of the wavelengths λ11AA, λ12AA, and λ13AA. Similarly, optical transceiver 30BA can receive optical signals of any of the wavelengths λ21AA, λ22AA, and λ23AA, and optical transceiver 30CA can receive optical signals of any of the wavelengths λ31AA, λ32AA, and λ33AA. Each of the wavelengths λ11AA, λ12AA, λ13AA, λ21AA, λ22AA, λ23AA, λ31AA, λ32AA, and λ33AA is a wavelength defined as an optical path in the optical communication network 3 (a wavelength associated with an optical path).

[0109] Figure 5B shows an example of the relationship between the transmission wavelength assigned to the optical transceiver and the passband of the port for the uplink main signal in the optical splitter.

[0110] In Figure 5B, the horizontal axis represents wavelength. In Figure 5B, Rλ1BA represents the wavelength band of the optical signal input to the first terminal of the multilayer filter 21AB, Rλ2BA (first wavelength band) represents the wavelength band of the optical signal input to the first terminal of the multilayer filter 21BB, and Rλ23BA represents the wavelength band of the optical signal input to the first terminal of the multilayer filter 21CB. As shown in Figure 5B, the bands Rλ1BA, Rλ2BA, and Rλ3BA are all different from each other. More specifically, the wavelength band of Rλ2BA is higher than that of Rλ1BA, and the wavelength band of Rλ3BA is higher than that of Rλ2BA. Furthermore, the bands R1BA, R2BA, and R3BA are different (do not overlap) from the bands R1AA, R2AA, and R3AA mentioned above. The boundary between band Rλ1BA and band Rλ2BA is the reference wavelength fcB1, the boundary between band Rλ2BA and band Rλ3BA is the reference wavelength fcB2, and the upper limit of band Rλ3BA is the reference wavelength fcB3. Bands Rλ1BA, Rλ2BA, and Rλ3BA are included, for example, in the C-band.

[0111] The bandwidth Rλ1BA includes wavelengths λ11BA, λ12BA, and λ13BA. Wavelengths λ11BA, λ12BA, and λ13BA are distinct from each other. More specifically, wavelength λ12BA is higher than wavelength λ11BA, and wavelength λ13BA is higher than wavelength λ12BA. For example, each of wavelengths λ11BA, λ12BA, and λ13BA is a wavelength channel with a 100 GHz grid (wavelength spacing of 0.8 nm). However, it is not limited to a 100 GHz grid; for example, each of wavelengths λ11BA, λ12BA, and λ13BA may be a wavelength channel with a 50 Hz grid.

[0112] The bandwidth R1BA is a wavelength band capable of accommodating three wavelength channels of a 100 GHz grid. In a specific example, bandwidth R1BA is the wavelength band of a 300 GHz grid and has a wavelength width of 2.4 nm. The number of wavelength channels accommodated in bandwidth R1BA is not limited to three; it may be two or four or more.

[0113] The bandwidth Rλ2BA includes wavelengths λ21BA, λ22BA, and λ23BA, and the bandwidth Rλ3BA includes wavelengths λ31BA, λ32BA, and λ33BA. The relationship between bandwidth Rλ2BA and wavelengths λ21BA, λ22BA, and λ23BA, and the relationship between bandwidth Rλ3BA and wavelengths λ31BA, λ32BA, and λ33BA are the same as the relationship between bandwidth Rλ1BA and wavelengths λ11BA, λ12BA, and λ13BA described above, so no explanation is provided.

[0114] The transmission wavelength of optical transceiver 30AA is selected from wavelengths λ11BA, λ12BA, and λ13BA. For optical transceiver 30AA, one of the wavelengths λ11BA, λ12BA, and λ13BA, which are included in the wavelength band Rλ21BA assigned to the uplink port P22AB to which optical transceiver 30AA is connected, is set as the transmission wavelength. Similarly, the transmission wavelength of optical transceiver 30BA is exclusively selected from wavelengths λ21BA, λ22BA, and λ23BA, and the transmission wavelength of optical transceiver 30CA is exclusively selected from wavelengths λ31BA, λ32BA, and λ33BA.

[0115] As described above, the optical branching device 20AA can be configured as a passive device that assigns a certain range of wavelength bands to the downlink ports P22AA, P22BA, P22CA and the uplink ports P22AB, P22BB, P22CB on the branch line side. Furthermore, the transmission and reception wavelengths of the main signals of each optical transceiver 30AA, 30BA, and 30CA can be selected (changed) within a certain range (the range of wavelength bands assigned to the corresponding ports of the optical branching device 20AA). In addition, the configuration (wavelength characteristics) of other optical branching devices 20AB, 20AC connected to the optical wavelength division multiplexing switch 10A to which the optical branching device 20AA is connected can be the same as the configuration of the optical branching device 20AA. Therefore, a common type of optical branching device 20 can be used in the optical communication network 3, and the number of types of optical branching devices 20 to be used can be reduced.

[0116] In the example shown in Figure 5B, the bandwidths R21BA, R22BA, and R23BA do not overlap, and there is no overlap in the transmission wavelengths that can be set between the optical transceivers 30AA, 30BA, and 30CA. However, some of the transmission wavelengths that can be set between the optical transceivers 30AA, 30BA, and 30CA may overlap. For example, some of the bandwidths R21BA and R22BA may overlap, and wavelengths λ13AB and λ21AB may be the same wavelength. If the first wavelength and the second wavelength can be set as transmission wavelengths in optical transceiver 30AA, and the first wavelength is different from the transmission wavelengths that can be set in optical transceivers 30BA and 30CA, then some of the transmission wavelengths that can be set in optical transceiver 30AA may be the same as the second wavelength.

[0117] In communication between the OLT function unit 11 and the ONU function unit 31, a PON frame is used. Specifically, the PON OAM frame defined in IEEE 802.3ah is used. In a concrete example, an extended OAM frame is used.

[0118] [6. Operation of the Optical Remote Control System] The operation of the optical remote control system 2A will be described below as representative. The operation of the optical remote control systems 2B and 2C is the same as that of the optical remote control system 2A.

[0119] Figure 6 is a sequence diagram showing an example of remote control of an optical transceiver in an optical remote system according to the embodiment. Figure 7 is a schematic diagram showing an example of downlink communication in an optical remote system according to the embodiment. Figure 8 is a schematic diagram showing an example of uplink communication in an optical remote system according to the embodiment. Figure 6 shows a representative remote control sequence for optical transceiver 30AA, but the remote control sequences for optical transceivers 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, and 30CC are the same.

[0120] The management device 50 stores the wavelength band of the downlink port in each of the optical branching devices 20AA, 20AB, 20AC, 20B, 20C, and 20D, and stores the configurable transmission wavelengths in each of the optical transceivers 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, 30CC, 30D, 30E, 30F, 30G, 30H, 30I, 30J, 30K, and 30L. The management device 50 determines the main signal path and transmission wavelength for each of the optical transceivers 30. For the transmission wavelength of the main signal, the management device 50 selects one of several configurable wavelengths in the optical transceiver as the transmission wavelength.

[0121] The management device 50 generates a control frame 1 for remotely controlling the optical transceiver 30AA. The control frame is, for example, an Ethernet frame, and in a more specific example, an Ethernet OAM frame. The control frame 1 stores control information for the optical wavelength division multiplexer SW 10A and the optical transceiver 30AA.

[0122] As shown in Figure 6, the management device 50 transmits control frame 1 using the Ethernet protocol (step S1). In Figure 7, the circled figure "1" represents control frame 1. In Figure 7, control frames 2 and 3 for controlling optical transceivers 30B and 30C are also shown. The circled figure "2" represents control frame 2 for remotely controlling optical transceiver 30B, and the circled figure "3" represents control frame 3 for remotely controlling optical transceiver 30B. As shown in Figure 7, each of control frames 1, 2, and 3 is transmitted along the transmission path 70A toward the optical wavelength division multiplexing switch 10A.

[0123] The SW control unit 12 of the optical wavelength division multiplexer SW 10A receives the control frame 1. The SW control unit 12 extracts control information from the control frame 1 and analyzes the extracted control information. The SW control unit 12 sets the WSS 14 and Add / Drop 15 according to the transmission path and wavelength included in the control information (step S2).

[0124] The SW control unit 12 outputs control information to the remote optical TRx control unit 13 (step S3). The remote optical TRx control unit 13 converts the input control information into commands for the optical transceiver 30 (step S4). The control information may be converted into multiple commands. In this example, the control information is assumed to have been converted into N commands (commands 1, 2, ..., N), where N is a natural number.

[0125] The remote optical TRx control unit 13 of the optical wavelength division multiplexing switch 10A outputs command 1 to the OLT function unit 11 (step S5). The OLT function unit 11 generates an OAM frame containing command 1 (GetRequest or SetRequest) (step S6). Specifically, the OLT function unit 11 generates an OAM frame 1 with the ONU function unit 31 of the optical transceiver 30AA as the destination.

[0126] The OLT function unit 11 transmits a downlink multiplexed control signal, which is an optical signal containing a downlink control signal 1 carrying the OAM frame 1 (step S7). The optical transceiver unit 111 transmits the downlink multiplexed control signal as an optical signal of the control downlink wavelength described above. The downlink multiplexed control signal output from the optical transceiver unit 111 is transmitted to the optical transceiver 30AA via the control signal multiplexing unit 16 and the optical branching device 20AA.

[0127] The C-TRx311 of the optical transceiver 30AA receives the downlink multiplexed control signal. The ONU function unit 31 extracts the OAM frame addressed to its own device from the downlink multiplexed control signal. The frame processing unit 313 extracts command 1 from the OAM frame (step S8) and outputs command 1 to the control unit 330, for example, as an electrical signal (step S9). The control unit 330 executes command 1 (step S10).

[0128] One of the instructions 1 through N is an instruction to set the transmission wavelength of the U-TRx301 optical transmitter. The SetRequest instruction includes the address of the control register for setting the transmission wavelength of the U-TRx301 and the wavelength value (data). When the control unit 330 receives an instruction to set the transmission wavelength of the U-TRx301 optical transmitter, it writes the specified value to the specified address in the control register. This sets (controls) the transmission wavelength of the U-TRx301 optical transmitter.

[0129] The control unit 330 of the optical transceiver 30AA acquires the execution result 1 of the command 1 and outputs the execution result 1 to the ONU function unit 31, for example, as an electrical signal (step S11). The ONU function unit 31 generates an OAM frame 1' containing the execution result 1 of the command 1 (step S12). The optical transceiver 30AA burst-transmits an uplink control signal 1 (response signal) carrying the uplink OAM frame 1' (step S13). Burst transmission is a method of repeatedly alternating between a transmission period in which a signal is transmitted and a non-transmission period in which no signal is transmitted, and not outputting (not emitting) an optical signal of the transmission wavelength during the non-transmission period. In this example, the downlink control signal is not burst-transmitted, but the optical transceiver 111 may burst-transmit the downlink control signal.

[0130] The uplink multiplexed control signal carrying the OAM frame 1' reaches the OLT function unit 11 via the optical branching device 20AA and the control signal multiplexing unit 16 of the optical wavelength multiplexing switch 10A.

[0131] The OLT function unit 11 of the optical wavelength division multiplexing switch SW 10A receives the uplink multiplexing control signal. The OLT function unit 11 extracts the OAM frame 1' from the uplink multiplexing control signal and obtains the execution result 1 from the OAM frame 1' (step S14). The OLT function unit 11 outputs the execution result from the optical transceiver 30AA to the remote optical TRx control unit 13 (step S15).

[0132] The remote optical TRx control unit 13 outputs command 2 to the OLT function unit 11 (step S16), just as in step S5 described above. The OLT function unit 11 transmits a downlink multiplex control signal carrying the OAM frame containing command 2, just as in step S7 described above. Command 2 is executed in the ONU function unit 31, and an uplink control signal 1, superimposed with the execution result 2 of command 2, is transmitted in burst from the optical transceiver 30AA. The operations from steps S4 to S14 are then repeatedly executed for commands 3...N. The OLT function unit 11 outputs the final execution result N to the remote optical TRx control unit 13 (step S17), and the remote optical TRx control unit 13 obtains the execution results 1, 2, ..., N.

[0133] The remote optical TRx control unit 13 generates response information to the control information sent to the optical transceiver 30AA based on the execution results 1, 2, ..., N received from the optical transceiver 30AA. The remote optical TRx control unit 13 outputs the generated response information to the SW control unit 12 (step S18). The SW control unit 12 generates a response frame 1, which is an Ethernet OAM frame containing the input response information (step S19), and transmits the generated response frame 1 to the management device 50 (step S20).

[0134] Optical transceivers 30B and 30C can also be remotely controlled, just like optical transceiver 30AA. In Figures 7 and 8, the figure "1" enclosed in a square frame represents the downlink control signal 1 and the uplink control signal 1, the figure "2" enclosed in a square frame represents the downlink control signal 2 and the uplink control signal 2, and the figure "3" enclosed in a square frame represents the downlink control signal 3 and the uplink control signal 3. The downlink multiplexed control signals are combined with the downlink main signal and transmitted as downlink optical multiplexed signals through the single-core transmission line 61A.

[0135] Optical transceivers 30BA and 30CA, like optical transceiver 30AA, generate OAM frames 2' and 3' containing the execution results of the instructions. Optical transceivers 30BA and 30CA burst-transmit uplink control signals 2 and 3 carrying the OAM frames 2' and 3'.

[0136] For example, downlink control signals 1, 2, and 3 for optical transceivers 30AA, 30BA, and 30CA can be transmitted at different times, and uplink control signals 1, 2, and 3 output from optical transceivers 30AA, 30BA, and 30CA can be transmitted at different times. In another example, downlink control signals 1, 2, and 3 for two or three of the optical transceivers 30AA, 30BA, and 30CA can be transmitted continuously by time-division multiplexing (Figure 7), and uplink control signals output from two or three of the optical transceivers 30AA, 30BA, and 30CA can be transmitted continuously by time-division multiplexing (Figure 8).

[0137] The sequence described above sets the transmission and reception wavelengths of the main signals for each of the optical transceivers 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, 30CC, 30D, 30E, 30F, 30G, 30H, 30I, 30J, 30K, and 30L, as well as the transmission paths for each main signal.

[0138] Figure 9A shows a first example of setting the wavelength and transmission path of the main signal in an optical communication system according to an embodiment.

[0139] Hereinafter, it is assumed that the optical transceiver 30AA can be set to transmit at one of wavelengths λA and λC, and the optical transceiver 30G can be set to transmit at one of wavelengths λA and λB (λB is different from λC).

[0140] In the first example, the transmission wavelength of the main signal of optical transceiver 30AA is set to λA, and the transmission wavelength of the main signal of optical transceiver 30G is set to λA. The counterpart device for optical transceiver 30AA is optical transceiver 30D, and the main signal is transmitted between optical transceiver 30AA and optical transceiver 30D. The counterpart device for optical transceiver 30G is optical transceiver 30J, and the main signal is transmitted between optical transceiver 30G and optical transceiver 30J.

[0141] In the first example, the transmission path for the main signal (wavelength λA) transmitted from optical transceiver 30AA is in the order of optical transceiver 30AA, optical branching device 20AA, optical wavelength division multiplexer SW 10A, optical wavelength division multiplexer SW 10B, optical branching device 20B, and optical transceiver 30D (clockwise path in the figure). The transmission path for the main signal (wavelength λA) transmitted from optical transceiver 30G is in the order of optical transceiver 30G, optical branching device 20C, optical wavelength division multiplexer SW 10C, optical wavelength division multiplexer SW 10D, optical branching device 20D, and optical transceiver 30J (counterclockwise path in the figure). The transmission path (first optical path) for the main signal (first main signal) transmitted from optical transceiver 30AA and the transmission path (second optical path) for the main signal (second main signal) transmitted from optical transceiver 30G do not overlap (they do not contain the same subpath). The control device 50 allows setting the transmission wavelength of optical transceiver 30AA to λA and the transmission wavelength of optical transceiver 30G to λA if the transmission path of the main signal transmitted from optical transceiver 30AA and the transmission path of the main signal transmitted from optical transceiver 30G do not include the same subpath. Therefore, even if the same wavelength λA is set as the transmission wavelength for optical transceivers 30AA and 30G, their respective main signals can be transmitted.

[0142] Figure 9B shows a second example of setting the wavelength and transmission path of the main signal in an optical communication system according to the embodiment.

[0143] In the second example, the transmission wavelength of the main signal of optical transceiver 30AA is set to λA, and the transmission wavelength of the main signal of optical transceiver 30G is set to λB. The second example is not mutually exclusive with the first example. In the second example, in addition to the two transmission paths for the main signal of wavelength λA (first optical path and second optical path) set in the first example, a transmission path for the main signal of wavelength λB can be set.

[0144] In the second example, the transmission path for the main signal (wavelength λA) transmitted from optical transceiver 30AA is in the following order: optical transceiver 30AA, optical splitter 20AA, optical wavelength division multiplexer SW10A, optical wavelength division multiplexer SW10B, optical splitter 20B, and optical transceiver 30D (clockwise path in the figure). The transmission path for the main signal (wavelength λB) transmitted from optical transceiver 30G is in the following order: optical transceiver 30G, optical splitter 20C, optical wavelength division multiplexer SW10C, optical wavelength division multiplexer SW10A, optical wavelength division multiplexer SW10B, optical wavelength division multiplexer SW10D, optical splitter 20D, and optical transceiver 30J (clockwise path in the figure). The transmission path (first optical path) of the main signal (first main signal) transmitted from optical transceiver 30AA and the transmission path (second optical path) of the main signal (second main signal) transmitted from optical transceiver 30G overlap (including the same subpath). However, since the wavelength λA of the main signal transmitted from optical transceiver 30AA and the wavelength λB of the main signal transmitted from optical transceiver 30G are different, each main signal can be transmitted. The control device 50 can set a clockwise transmission path in the figure by selecting λA as the wavelength of the main signal transmitted from optical transceiver 30G, and can set a counterclockwise transmission path in the figure by selecting λB as the wavelength of the main signal transmitted from optical transceiver 30G. For example, if the transmission wavelength of the main signal of the optical transceiver 30G is set to λA (a counterclockwise transmission path is set in the figure), and a failure occurs in the optical transmission path between the optical wavelength division multiplexing switches 10C and 10D, the transmission of the main signal can be continued by switching the transmission wavelength of the main signal of the optical transceiver 30G to λB (switching to a clockwise transmission path in the figure).

[0145] [7. Modified Examples] Figure 10 shows a modified example of the configuration of the optical remote control system according to the embodiment. In the example in Figure 10, each of the optical transmission lines 61A, 61B, and 61C is a single-core transmission line.

[0146] In this modified configuration, the optical signal is handled as a two-core transmission in WSS14 and Add / Drop15, while the optical signal is handled as a single-core transmission in the control signal multiplexing unit 16. Add / Drop15 converts between single-core and two-core transmission. Three single-core optical transmission lines 61A, 61B, and 61C extend from Add / Drop15, and the control signal multiplexing unit 16 includes WDM couplers 16A, 16B, and 16C, respectively, positioned in the middle of the optical transmission lines 61A, 61B, and 61C. Downlink multiplexed control signals output from the OLT function unit 11A are distributed to each branch line by optical couplers (power couplers) (not shown) positioned on the transmission line extending from the optical transceiver unit 111. The WDM couplers 16A, 16B, and 16C multiplex the respective distributed downlink multiplexed control signals into the downlink main signal transmitted through each transmission line 61A, 61B, and 61C.

[0147] The control signal multiplexing unit 16 separates the uplink optical multiplexed signals transmitted through the single-core transmission lines 61A, 61B, and 61C into an uplink main signal and an uplink multiplexed control signal using WDM couplers 16A, 16B, and 16C, respectively.

[0148] Figure 11 shows a modified example of the hardware configuration of the optical branching device according to the embodiment.

[0149] The optical branching device 20AA according to this modified example corresponds to a single-core transmission line on the trunk line side. The optical branching device 20AA includes a trunk line port P21 (P21A, P21B). Port P21 is connected to the single-core transmission line 61A.

[0150] The optical branching device 20AA according to this modified example includes a WDM coupler 21 which combines the WDM couplers 21A and 21B shown in Figure 3. The WDM coupler 21 includes multilayer film filters 21AA, 21BA, 21CA, 21AB, 21BB, and 21CB.

[0151] Port P21 is connected to WDM coupler 22A via a single-core transmission line. WDM coupler 22A is connected to WDM coupler 22B via a single-core transmission line. WDM coupler 22B is connected to the second terminal of multilayer film filter 21AB via a single-core transmission line.

[0152] The third terminal of the multilayer filter 21CB and the second terminal of the multilayer filter 21AA are connected via an optical transmission path.

[0153] The other configurations of the optical remote control system according to this modified example are the same as those of the optical remote control system according to the embodiment described above.

[0154] In the optical branching device 20AA according to this modified example, fcA1 > fcB3. The WDM signals of the three downstream main signals (with a lower limit wavelength of fcA1) pass through the multilayer filters 21AB, 21BB, and 21CB respectively and are input to the second terminal of the multilayer filter 21AA. Since no upstream optical signal is input to the first terminals of the multilayer filters 21AA, 21BA, and 21CA, no optical signal is input to the third terminal of the multilayer filter 21CB.

[0155] In the optical branching device 20AA according to this modified example, the wavelength of the downstream main signal and the wavelength of the upstream main signal may overlap. For example, if fcA1 = fcB1, fcA2 = fcB2, and fcA3 = fcB3, the bandwidth Rλ1AA may include the downstream wavelengths λ11AA, λ12AA, λ13AA and the upstream wavelengths λ11BA, λ12BA, λ13BA without overlapping. Similarly, the bandwidths Rλ2AA and Rλ3AA also include the downstream and upstream wavelengths. In this case, the WDM coupler 21 can have the same configuration as the WDM coupler 21B (a configuration including three multilayer film filters), and the branch line port can be a single-core bidirectional port. In this configuration, WDM coupler 24A1 and WDM coupler 24B1 are arranged in series, WDM coupler 24A2 and WDM coupler 24B2 are arranged in series, and WDM coupler 24A3 and WDM coupler 24B3 are arranged in series.

[0156] In the embodiment described above, the management device 50 remotely controlled the transmission wavelength of the optical transceiver 30 using the PON function, but is not limited to this. For example, the management device 50, the optical transceiver, and the optical wavelength division multiplexing switch 10 may be connected via an electrical signal network, and the transmission wavelength of the optical transceiver 30 and the transmission path of the main signal may be set by electrical signals (for example, using EtherOAM).

[0157] The above-described embodiment describes a configuration in which the optical transceiver 30 is remotely controlled using EPON (Ethernet PON) as defined in IEEE 802.3ah, but is not limited thereto. For example, GPON (Gigabit PON) as defined in ITU-T G. 984 may be used. In this case, an OMCI (ONU Management and Control Interface) frame is used instead of an OAM frame. Furthermore, the optical transceiver 30 may be remotely controlled using a frame defined by the user.

[0158] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described above, and includes the meaning of equivalents of the claims and all modifications within that scope.

[0159] Each process (each function) of the above-described embodiment is achieved by a processing circuit including one or more processors. The processing circuit may consist of an integrated circuit, etc., which combines one or more memories, various analog circuits, and various digital circuits in addition to the one or more processors. The one or more memories store programs (instructions) that cause the one or more processors to execute each of the above processes. The one or more processors may execute each of the above processes according to the programs read from the one or more memories, or they may execute each of the above processes according to logic circuits that have been designed in advance to execute each of the above processes. The above-mentioned processor may be various processors suitable for computer control, such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), and ASIC (Application Specific Integrated Circuit). Multiple physically separated processors may cooperate with each other to perform the above-mentioned processes. For example, the above-mentioned processors installed in each of multiple physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), WAN (Wide Area Network), and the Internet to perform the above-mentioned processes. The above program may be installed on the above memory via the above network from an external server device, or it may be distributed on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), or semiconductor memory, and then installed on the above memory from the above recording medium.

[0160] 1 Optical communication system 2, 2A, 2B, 2C, 2D Optical remote control system 3 Optical communication network 3A Metro network 3B Access network 10, 10A, 10B, 10C, 10D Optical wavelength division multiplexing switch (optical wavelength division multiplexing SW) 11 (11A) OLT function unit 111 Optical transceiver unit 12 SW control unit 13 Remote optical transceiver control unit (remote optical TRx control unit) 14 Wavelength selection switch (WSS) 15 Wavelength division multiplexing separation unit (Add / Drop) 16 Control signal multiplexing unit 16A, 16B, 16C, 16AA, 16BA, 16CA, 16AB, 16BB, 16CB WDM coupler 20, 20AA, 20AB, 20AC, 20B, 20C, 20D Optical branching device 21, 21A, 21B, 22A, 22B, 24A1, 24A2, 24A3, 24B1, 24B2, 24B3, 304A, 304B WDM coupler 23A, 23B Optical coupler 21AA, 21BA, 21CA, 21AB, 21BB, 21CB Multilayer film filter (optical filter) 30, 30AA, 30BA, 30CA, 30AB, 30BB, 30CB, 30AC, 30BC, 30CC, 30D, 30E, 30F, 30G, 30H, 30I, 30J, 30K, 30L Optical transceiver 301 Optical transceiver (U-TRx) 302 Drive circuit 303 Digital signal processor (DSP) 311 Optical Transceiver Unit (C-TRx) 31 ONU Function Unit 313 Frame Processing Unit 314 Processor 315 Memory 32 Microcontroller Unit (MCU) 321 Processor 322 Memory 323 D / A Converter (DAC) 324 A / D Converter (ADC) 330 Control Unit 40 User Device 50 Management Device 60A, 60B, 60C, 60D Optical Transmission Line (2-core transmission line) 61A, 61B, 61C, 62AA, 62BA, 62CA, 62AB, 62BB, 62CB, 62AC, 62BC, 62CC Optical Transmission Line (2-core transmission line) 61AA, 61BA, 61CA, 62AAA, 62BAA, 62CAA Optical Transmission Line (Downstream transmission line) 61AB, 61BB, 61CB, 62ABA, 62BBA, 62CBA Optical transmission lines (upstream transmission lines) 70A, 70B, 70C, 70D Transmission lines MP1, MP2 Metro side port AP1,AP2, AP3 access-side ports PA, PB, P21 (P21A, P21B), P22AA, P22BA, P22CA, P22AB, P22BB, P22CB ports,

Claims

1. In an optical communication network that transmits an optical signal in which multiple main signals are wavelength-division multiplexed, the network comprises: a first branching device and a second branching device that wavelength-separate the optical signal into the multiple main signals and multiplex the multiple main signals; a first optical transceiver and a second optical transceiver connected to the first branching device; a third optical transceiver and a fourth optical transceiver connected to the second branching device; and an optical wavelength division multiplexing switch connected to the first branching device by a first optical transmission path and to the second branching device by a second optical transmission path, wherein the multiple main signals have wavelengths selected from a specific wavelength grid, and the first branching device includes: a first branch-side port connected to the first optical transceiver; a second branch-side port connected to the second optical transceiver; and a first trunk-side port connected to the optical wavelength division multiplexing switch, and the second branching device includes: a third branch-side port connected to the third optical transceiver; and a fourth branch-side port connected to the fourth optical transceiver. The optical wavelength division multiplexer includes a second trunk port connected to the optical wavelength division multiplexer switch, the optical wavelength division multiplexer switch outputs a first main signal and a third main signal to the first optical transmission line, the second main signal and a fourth main signal to the second optical transmission line, the first main signal is an optical signal of a first wavelength included in the first wavelength band, the second main signal is an optical signal of a second wavelength included in the first wavelength band but different from the first wavelength, the third main signal is an optical signal of a third wavelength included in the second wavelength band, the second wavelength band is different from the first wavelength band, the fourth main signal is an optical signal of a fourth wavelength included in the second wavelength band but different from the third wavelength, the first branching device outputs an optical signal input from the first trunk port and included in the first wavelength band to the first branching device, the optical signal input from the first trunk port and included in the second wavelength band to the second branching device, The optical transceiver receives an optical signal from the second trunk port that is included in the first wavelength band and outputs it to the third branch port, and the optical signal received from the second trunk port that is included in the second wavelength band and outputs it to the fourth branch port, and the first optical transceiver receives the first main signal,An optical communication system in which the second optical transceiver receives the third main signal, the third optical transceiver receives the second main signal, and the fourth optical transceiver receives the fourth main signal.

2. The first optical transceiver transmits a fifth main signal, the second optical transceiver transmits a sixth main signal, the fifth main signal is an optical signal of a fifth wavelength included in the third wavelength band, the sixth main signal is an optical signal of a sixth wavelength included in the fourth wavelength band which is different from the third wavelength band, the first branching device outputs an optical signal input from the first branch port and included in the third wavelength band to the first optical transmission line from the first trunk port, an optical signal input from the second branch port and included in the fourth wavelength band to the first optical transmission line from the first trunk port, the third optical transceiver transmits a seventh main signal, the fourth optical transceiver transmits an eighth main signal, the seventh main signal is an optical signal of a seventh wavelength included in the third wavelength band which is different from the fifth wavelength, the eighth main signal is an optical signal of an eighth wavelength included in the fourth wavelength band which is different from the sixth wavelength, the second branching device, The optical communication system according to claim 1, wherein an optical signal input from the third branch port and included in the third wavelength band is output from the second trunk port to the second optical transmission path, and an optical signal input from the fourth branch port and included in the fourth wavelength band is output from the second trunk port to the second optical transmission path.

3. The optical communication system according to claim 2, wherein each of the first optical transmission path and the second optical transmission path is a single-core bidirectional optical transmission path, and each of the first wavelength band, the second wavelength band, the third wavelength band, and the fourth wavelength band are different from each other.

4. The optical communication system according to claim 2, wherein each of the first optical transmission path and the second optical transmission path is a single-core bidirectional optical transmission path, the first wavelength band and the third wavelength band are the same, the first wavelength, the second wavelength, the fifth wavelength, and the seventh wavelength are different from each other, the second wavelength band and the fourth wavelength band are the same, and the third wavelength, the fourth wavelength, the sixth wavelength, and the eighth wavelength are different from each other.

5. The optical communication system according to any one of claims 1 to 4, wherein at least one of the first branching device and the second branching device includes a plurality of optical filters that wavelength-multiplex an optical signal based on a reference wavelength, each of the plurality of optical filters includes a first terminal, a second terminal, and a third terminal, wavelength-multiplex an optical signal input from the first terminal with a wavelength component lower than the reference wavelength and an optical signal input from the third terminal with a wavelength component higher than the reference wavelength, outputs the wavelength-multiplexed optical signal from the second terminal, separates an optical signal input from the second terminal with the reference wavelength, outputs the wavelength component lower than the reference wavelength from the first terminal and outputs the wavelength component higher than the reference wavelength from the third terminal, and the reference wavelengths in each of the plurality of optical filters are different from each other.

6. In an optical communication network that transmits an optical signal obtained by wavelength division multiplexing of multiple main signals, the optical wavelength division multiplexing switch outputs a first main signal, which is an optical signal of a first wavelength included in a first wavelength band, to a first optical transmission path; the optical wavelength division multiplexing switch outputs a second main signal, which is an optical signal of a second wavelength included in the first wavelength band and different from the first wavelength, to a second optical transmission path; the optical wavelength division multiplexing switch outputs a third main signal, which is an optical signal of a third wavelength included in a second wavelength band different from the first wavelength band, to the first optical transmission path; the optical wavelength division multiplexing switch outputs a fourth main signal, which is an optical signal of a fourth wavelength included in the second wavelength band and different from the third wavelength, to the second optical transmission path; and a first branching device connected to the first optical transmission path outputs an optical signal input from a first trunk-side port connected to the first optical transmission path and included in the first wavelength band, to a first branch-side port. An optical communication method comprising: the first branching device outputs an optical signal input from the first trunk port and included in the second wavelength band to the second branch port; the second branching device connected to the second optical transmission line outputs an optical signal input from the second trunk port connected to the second optical transmission line and included in the first wavelength band to the third branch port; the second branching device outputs an optical signal input from the second trunk port and included in the second wavelength band to the fourth branch port; the first optical transceiver connected to the first branch port receives the first main signal; the second optical transceiver connected to the second branch port receives the third main signal; the third optical transceiver connected to the third branch port receives the second main signal; and the fourth optical transceiver connected to the fourth branch port receives the fourth main signal, wherein the plurality of main signals have wavelengths selected from a specific wavelength grid.

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