Optical communication system, optical transmission device, optical communication method, and program

Abstract

An optical communication system according to the present invention comprises an optical transmission device and a transponder 2 that is provided at a user location. The transponder 2 communicates with the optical transmission device via an optical fiber 3. The optical transmission device comprises an optical amplification unit 11 that amplifies an optical signal, a routing function unit 12 that comprises a port that accommodates the transponder 2 and outputs the amplified optical signal to the port, and a first branching unit 51 that outputs the optical signal as outputted from the port to the optical fiber 3.

Description

Optical Communication System, Optical Transmission Device, Optical Communication Method, and Program

[0001] The present disclosure relates to an optical communication system, an optical transmission device, an optical communication method, and a program.

[0002] In IOWN (Innovative Optical and Wireless Network) APN (All-Photonics Network), communication from the network to the device is all optical-based, aiming to achieve low-power consumption, high-quality, high-capacity, and low-latency communication. In signal communication, the optical-to-electrical conversion performed in conventional networks is eliminated, and a low-latency communication is realized by constructing an end-to-end optical path. IOWN APN is described in Non-Patent Documents 1 and 2.

[0003] NTT Research and Development, "What is an All-Photonics Network?", [online], Internet <https: / / www.rd.ntt / iown / 0002.html> NTT Research and Development (Hideki Nishizawa et al.), "Examination of an Open All-Photonics Network in the IOWN Global Forum", 2022.03.09 [online], Internet <https: / / www.rd.ntt / research / JN202203_17536.html>

[0004] There is a WDM (Wavelength Division Multiplexing) system capable of transmitting optical signals over long distances and with large capacities. Conventional WDM systems are configured based on the premise that the ROADM unit and the transponder are deployed in the same building. Therefore, the system is configured assuming a short distance between the ROADM unit and the transponder.

[0005] On the other hand, in order to achieve end-to-end optical connectivity with IOWN APN, a configuration is being considered in which the distance between the ROADM unit and the transponder is extended, and the transponders are spaced apart at the user site. In this case, the following challenges arise. In a typical WDM system, the ROADM unit houses each transponder and separates the passing optical signal according to wavelength. Therefore, when multiple transponders are spaced apart at the user site, it is necessary to prepare an extended optical fiber for each transponder, which presents a cost challenge.

[0006] This disclosure is made in view of the above circumstances, and the purpose of this disclosure is to provide a technology that can realize a spaced-out configuration of transponders at low cost.

[0007] To achieve the above objective, one aspect of the present disclosure is an optical communication system comprising an optical transmission device and a transponder located at a user site, wherein the transponder communicates with the optical transmission device via an optical fiber, and the optical transmission device comprises an optical amplification unit for amplifying an optical signal, a port for housing the transponder and a path function unit for outputting the amplified optical signal to the port, and an optical coupler for outputting the optical signal output from the port to the optical fiber.

[0008] One aspect of the present disclosure is an optical transmission device that communicates with a transponder located at a user site via an optical fiber, comprising: an optical amplification unit for amplifying an optical signal; a path function unit having a port for housing the transponder and outputting the amplified optical signal to the port; and an optical coupler for outputting the optical signal output from the port to the optical fiber.

[0009] One aspect of the present disclosure is an optical transmission device that communicates with a plurality of transponders located at a user site via an optical fiber, comprising: an optical amplification unit that amplifies an optical signal obtained by combining a plurality of wavelengths; a path function unit that outputs the amplified optical signal to a multiplexing / demultiplexing function unit; a multiplexing / demultiplexing function unit that demultiplexes the optical signal output from the path function unit into a plurality of optical signals for each wavelength; and an optical coupler that combines the demultiplexed plurality of optical signals and outputs them to the optical fiber.

[0010] One aspect of the present disclosure is an optical communication method for communicating with a transponder located at a user site via an optical fiber, wherein an optical amplification unit amplifies an optical signal, a path function unit outputs the amplified optical signal to a port housing the transponder, and an optical coupler outputs the optical signal output from the port to the optical fiber.

[0011] One aspect of this disclosure is a program that causes a computer to function as the optical transmission device described above.

[0012] This disclosure provides a technology that enables the implementation of a spaced-out configuration of transponders at low cost.

[0013] Figure 1 is a schematic diagram illustrating the spatial arrangement of transponders. Figure 2 is a diagram showing an example configuration of an optical communication system according to the first embodiment. Figure 3 is a diagram showing the transmission of optical signals from the transponder to the ROADM unit in the optical communication system of Figure 2. Figure 4 is a diagram showing an example of a protection configuration. Figure 5 is a diagram showing a modified example of the protection configuration. Figure 6 is a diagram showing an example configuration of an optical communication system according to the second embodiment. Figure 7 is a diagram showing the transmission of optical signals from the transponder to the ROADM unit in the optical communication system of Figure 6. Figure 8 is a diagram showing the configuration of an optical communication system in comparison. Figure 9 is an example of a hardware configuration.

[0014] Figure 1 is a schematic diagram illustrating the spaced-out arrangement of transponders in a WDM system. The spaced-out arrangement configuration extends the distance between the ROADM unit 1 and the transponder 2 to achieve end-to-end optical connectivity in IOWN APN, and positions the transponder 2 at the user site (remote site). In other words, the transponder 2 is placed at the user site, and the optical fiber 3 between the ROADM unit 1 and the transponder 2 is extended.

[0015] <First Embodiment> Figure 2 is a diagram showing an example configuration of an optical communication system according to the first embodiment. Figure 2 shows the transmission of an optical signal from the ROADM unit 1 to the transponder 2.

[0016] The optical communication system of this embodiment comprises an optical transmission device and a transponder 2 located at the user site. Although three transponders 2 are shown in the illustrated example, the system is not limited to these, and at least one transponder 2 is required. The optical transmission device is located on the network and comprises a ROADM unit 1 (optical amplification unit 11, path function unit 12) and a first branching unit 51. The first branching unit 51 is connected to the ROADM unit 1. The optical communication system may also include a second branching unit 52 located at the user site and connected to the transponder 2.

[0017] The optical communication system may include a first control unit 41 and a second control unit 42. The first control unit 41 is connected to the ROADM unit 1 and monitors and controls the ROADM unit 1. The second control unit 42 is located at the user site and is connected to each transponder 2 and monitors and controls the transponders 2.

[0018] The ROADM unit 1 included in the transmission device of this embodiment comprises an optical amplification unit 11 (AMP) and a path function unit 12 (WSS: Wavelength Selective Switches). In this embodiment, the multiplexing and demultiplexing function unit, which is an essential component in a typical ROADM unit 1, is omitted. Therefore, in this embodiment, the multiplexing and demultiplexing function unit, which may be excessive in specifications in small areas, for example, can be reduced, making it possible to construct an economically efficient optical communication system.

[0019] The optical amplification unit 11 amplifies the optical signal. Specifically, the optical amplification unit 11 is an optical device that amplifies the optical signal to an intensity that can be received by the transponder 2 or the opposing optical transmission device. The path function unit 12 outputs the optical signal (WDM signal) input from the optical amplification unit 11 to any path (port). In other words, the path function unit 12 switches the optical signal to any path.

[0020] In this embodiment, the routing function unit 12 utilizes available ports for connecting to other routing function units (not shown) or available ports for the multiplexing / demultiplexing function unit, and allocates these ports as ports for directly accommodating the transponder 2 at the user site. That is, the routing function unit 12 has a port for accommodating the transponder 2 and outputs the optical signal amplified by the optical amplification unit 11 to the port. The signal output from the port may be an optical signal containing multiple wavelengths (an optical signal in which multiple wavelengths have been combined).

[0021] Thus, the path function unit 12 of this embodiment utilizes an available path as a path to accommodate the transponder 2, thereby reducing the number of multiplexing and demultiplexing functions. The first branching unit 51 is connected to the port to accommodate the transponder 2.

[0022] The first branching unit 51 (optical coupler) outputs the optical signal output from the port of the path function unit 12 to the optical fiber 3. The first branching unit 51 may also output an optical signal to the optical fiber 3 in which the optical signal output from the port and the control signal output from the first control unit 41 connected to the optical transmission device are superimposed. The first branching unit 51 is an optical device capable of superimposing (wavelength division multiplexing, multiplexing) and branching multiple optical signals. An optical coupler can be used for the first branching unit 51.

[0023] The first control unit 41 controls and monitors the ROADM unit 1. Specifically, the first control unit 41 transmits control signals to the optical amplification unit 11 and the path function unit 12, respectively. The first control unit 41 also transmits a control signal (an optical signal of a predetermined wavelength) to the second control unit 42, causing the second control unit 42 to control and monitor each transponder 2. The second control unit 42 controls and monitors each transponder 2 according to the control signal.

[0024] At the user site, a second branching unit 52, at least one transponder 2, and a second control unit 42 are arranged.

[0025] The second branching unit 52 (another optical coupler) outputs the optical signal transmitted via the optical fiber 3 to each transponder 2. The second branching unit 52 may also output an optical signal in which the optical signal output from the path function unit 12 and the control signal are superimposed to each transponder 2 and to the second control unit 42 connected to each transponder 2. Specifically, the second branching unit 52 may branch the optical signal transmitted via the optical fiber 3 into multiple signals (in the illustrated example, into four signals) and output them to each transponder 2 and the second control unit 42. In this case, all of the branched optical signals are the same signal (an optical signal containing multiple wavelengths).

[0026] Transponder 2 communicates with the optical transmission device via optical fiber 3. Transponder 2 is an optical device that houses user equipment and converts electrical signals from the user equipment with signals output from the optical transmission device. As shown in the figure, multiple transponders 2 may be placed at the user site.

[0027] The transponder 2 extracts the optical signal of the required wavelength from the optical signal output from the second branching unit 52 and receives the optical signal of that wavelength. The second branching unit 52 may have wavelength-specific transmission and blocking functions, and may separate the optical signal containing multiple wavelengths output from the optical fiber 3 into wavelength-specific signals and output each separated optical signal to the corresponding transponder. Specifically, the second branching unit 52 may have wavelength-specific transmission and blocking functions by being equipped with an optical filter or the like, and may separate the optical signal output from the optical fiber 3 into each wavelength, and output each separated optical signal to the corresponding transponder 2 and second control unit 42, respectively. In this case, each transponder 2 receives the optical signal of the corresponding wavelength output from the second branching unit 52.

[0028] The second control unit 42 extracts the control signal (optical signal) of the required wavelength from the optical signal output from the second branching unit 52 and receives the control signal of that wavelength. The second control unit 42 uses the received control signal to control and monitor each transponder 2. If the second branching unit 52 separates the optical signal for each wavelength and outputs only the control signal to the second control unit 42, the second control unit 42 receives the control signal output from the second branching unit 52.

[0029] In this embodiment, the control signal for the transponder 2 installed at the user site is superimposed with the optical signal output from the route function unit 12 using the first branching unit 51 and transmitted to the second control unit 42 at the user site. This makes it possible to monitor and control multiple transponders 2 installed at the user site in this embodiment.

[0030] Figure 3 shows the transmission of an optical signal from the transponder 2 to the ROADM unit 1 in the optical communication system shown in Figure 2.

[0031] The second control unit 42 outputs a control signal (an optical signal of a predetermined wavelength) to the second branching unit 52. Each transponder 2 outputs an optical signal of a predetermined wavelength to the second branching unit 52. The second branching unit 52 superimposes (wavelength multiplexing, multiplexing) the control signal and the optical signals output from each transponder 2, and transmits the superimposed optical signal over the optical fiber 3.

[0032] The first branching unit 51 branches the optical signal input via the optical fiber 3 into multiple signals and outputs each branched optical signal to the first control unit 41 and the path function unit 12. All of the branched optical signals are the same signal (an optical signal containing multiple wavelengths).

[0033] The first control unit 41 extracts and receives only the control signal from the signal output from the first branching unit 51. The path function unit 12 extracts and receives only the optical signals other than the control signal from the signal output from the second branching unit 52. The optical signal extracted by the path function unit 12 may be an optical signal obtained by combining optical signals of multiple wavelengths.

[0034] The first branching unit 51 may split the optical signal input via the optical fiber 3 into an optical signal for the path function unit 12 and a control signal for the first control unit 41, output the split optical signal to the path function unit 12, and output the split control signal to the first control unit 41.

[0035] Figure 4 shows an example of a protection configuration (redundancy configuration) of this embodiment. The illustrated protection configuration includes a first control unit 41, redundant optical amplification units 11A and 11B, path function units 12A and 12B, and first branching units 51A and 51B. Specifically, two path function units 12 are constructed, and the active optical fiber 3A (active path) and the backup optical fiber 3B (protection path) passing through each path are constructed in advance.

[0036] In the illustrated configuration, optical signals and control signals are transmitted to the user site through the active system's optical amplification unit 11A, path function unit 12A, first branching unit 51A, and optical fiber 3A. Additionally, optical signals and control signals are transmitted to the user site through the backup system's optical amplification unit 11B, path function unit 12B, first branching unit 51B, and optical fiber 3B. The first control unit 41 outputs control signals to the first branching units 51A and 51B.

[0037] The user site includes redundant second branching units 52A and 52B and transponders 2A and 2B, a second control unit 42, and an optical switch (optical SW) 6. Figure 4 shows one redundant set of transponders 2A and 2B, but there may be multiple sets of redundant transponders 2A and 2B. The optical switch 6 is installed under the transponders 2A and 2B.

[0038] Optical signals and control signals are input to the second branch 52A of the active system via the optical fiber 3A of the active system. The transponder 2A of the active system processes the optical signals and outputs the processed signals to the optical switch 6. The second control unit 42 monitors and controls the transponder 2A using the control signals.

[0039] Optical signals and control signals are input to the second branch 52B of the backup system via the backup optical fiber 3B. The backup system transponder 2B processes the optical signals and outputs the processed signals to the optical switch 6. The second control unit 42 monitors and controls the transponder 2B using the control signals.

[0040] Under normal conditions, the optical switch 6 outputs the signal from the transponder 2A to a user device (not shown) accommodated by the transponders 2A and 2B. On the other hand, in case of a failure, the optical switch 6 outputs the signal from the transponder 2B to the user device.

[0041] By adopting such a protection configuration, when a failure occurs in the active optical fiber 3A, the optical switch 6 is switched to output the optical signal of the standby optical fiber 3B, thereby enabling immediate recovery of the section where the failure has occurred.

[0042] FIG. 5 is a modified example of the protection configuration shown in FIG. 4. The illustrated configuration is different from that of FIG. 4 in that the optical switch 6 is arranged in the front stage of the transponder 2 (that is, between the second branching units 52A and 52B and the transponder 2). In this case, the transponder 2 does not need to be redundant. In this modified example, the second branching unit 52A extracts only the optical signal for the transponder 2 from the optical signal output from the optical fiber 3A and outputs it to the optical switch 6. Similarly, the second branching unit 52B extracts only the optical signal for the transponder 2 from the optical signal output from the optical fiber 3B and outputs it to the optical switch 6.

[0043] Under normal conditions, the optical switch 6 outputs the optical signal output from the second branching unit 52A to the transponder 2. On the other hand, in case of a failure, the optical switch 6 outputs the optical signal output from the second branching unit 52B to the transponder 2.

[0044] The optical communication system of the present embodiment described above includes an optical transmission device and a transponder 2 arranged at a user base. The transponder 2 communicates with the optical transmission device via an optical fiber 3. The optical transmission device includes an optical amplification unit 11 that amplifies an optical signal, a path function unit 12 that includes a port for accommodating the transponder 2 and outputs the amplified optical signal to the port, and a first branching unit 51 (optical coupler) that outputs the optical signal output from the port to the optical fiber 3.

[0045] The optical transmission device of the present embodiment is an optical transmission device that communicates with a transponder 2 disposed at a user site via an optical fiber 3, and includes an optical amplification unit 11 that amplifies an optical signal, a path function unit 12 that includes a port for accommodating the transponder 2 and outputs the amplified optical signal to the port, and a first branching unit 51 (optical coupler) that outputs the optical signal output from the port to the optical fiber 3.

[0046] The ROADM unit 1 of the optical transmission device of the present embodiment can realize the spaced-apart arrangement of the transponders 2 without including a wavelength multiplexing / demultiplexing unit. Since a general ROADM unit essentially includes an optical amplification unit, a path function unit, and a multiplexing / demultiplexing function unit, for a medium- or small-scale area, the installation of redundant functional units occurs, thereby posing a problem in terms of economy. In contrast, in the present embodiment, the spaced-apart arrangement of the transponders 2 can be realized at low cost without including a wavelength multiplexing / demultiplexing unit. Although the optical transmission device of the present embodiment includes a first branching unit 51, the first branching unit 51 (optical coupler) is a module with lower specifications and lower cost compared to the multiplexing / demultiplexing function unit.

[0047] In addition, a general ROADM unit is configured such that the multiplexing / demultiplexing function unit accommodates transponders. When the passing optical signal includes a plurality of wavelengths, the multiplexing / demultiplexing function unit demultiplexes the optical signal into each wavelength and transmits each demultiplexed optical signal to each transponder via a different optical fiber. Therefore, when transmitting an optical signal including a plurality of wavelengths to a plurality of transponders spaced apart at the same user site (for example, a user building), it is necessary to prepare optical fibers for inter-building transmission for each wavelength. In contrast, in the present embodiment, an optical signal including a plurality of wavelengths can be transmitted to a user site via one optical fiber without demultiplexing the optical signal including a plurality of wavelengths by the multiplexing / demultiplexing function unit. Thereby, the cost required for system construction can be reduced.

[0048] <Second Embodiment> Fig. 6 is a diagram showing a configuration example of an optical communication system according to the second embodiment. Fig. 6 shows the transmission of an optical signal from the ROADM unit 1 to the transponder 2.

[0049] In this embodiment, a first branching unit 51 (optical coupler) for transponders 2 located at a distance from the user site is placed under the multiplexing / demultiplexing function unit 13 of the ROADM unit 1, and the optical signal to be transmitted to transponders 2 is wavelength multiplexed again. As a result, in this embodiment, the number of optical fibers (number of optical fiber cores) required for the user site can be reduced.

[0050] The optical communication system of this embodiment comprises an optical transmission device and a transponder 2 located at a user site. The optical transmission device is located on a network and comprises a ROADM unit 1 and a first branching unit 51 (optical coupler). The first branching unit 51 is connected to the ROADM unit 1. The optical communication system may also include a second branching unit 52 located at a user site and connected to the transponder 2. The optical communication system may also include a first control unit 41 and a second control unit 42. The first control unit 41 is connected to the ROADM unit 1 and monitors and controls the ROADM unit 1. The second control unit 42 is located at a user site and monitors and controls the transponder 2.

[0051] The configuration of the user site in Figure 6 (transponder 2, second control unit 42, second branching unit 52) ​​is the same as the configuration of the user site shown in Figure 2, so its explanation is omitted here.

[0052] The optical transmission device of this embodiment communicates with a plurality of transponders 2 located at the user site via optical fibers 3.

[0053] The ROADM unit 1 of this embodiment comprises an optical amplification unit 11 (AMP), a path function unit 12 (WSS), and a multiplexing / demultiplexing function unit 13. The optical amplification unit 11 amplifies the optical signal (WDM signal). The optical amplification unit 11 of this embodiment amplifies the optical signal, which is a combination of multiple wavelengths. The path function unit 12 outputs the optical signal amplified by the optical amplification unit 11 to the multiplexing / demultiplexing function unit 13. The multiplexing / demultiplexing function unit 13 demultiplexes the optical signal output from the path function unit 12 into multiple optical signals for each wavelength.

[0054] The first branching unit 51 is connected to the multiplexing / demultiplexing unit 13. An optical coupler can be used in the first branching unit 51. The first branching unit 51 combines the multiple optical signals separated by the multiplexing / demultiplexing unit 13 and outputs them to the optical fiber 3. The first branching unit 51 may also superimpose each of the separated optical signals with the control signal output from the first control unit 41 and output the superimposed optical signal to the optical fiber 3. The control signal for the transponder 2 at the user site can also be superimposed with the optical signal using the first branching unit 51 and transmitted to the second control unit 42 at the user site, thereby enabling monitoring and control of multiple spaced transponders 2.

[0055] Figure 7 shows the transmission of an optical signal from the transponder 2 to the ROADM unit 1 in the optical communication system shown in Figure 6.

[0056] The second control unit 42 outputs a control signal to the second branching unit 52. Each transponder 2 outputs an optical signal of a predetermined wavelength to the second branching unit 52. The second branching unit 52 wavelength-multiplexes the control signal and the optical signals output from each transponder 2, combines them, and outputs the combined optical signal to the optical fiber 3.

[0057] The first branching unit 51 branches the optical signal input via the optical fiber 3 into multiple signals and outputs each branched optical signal to the first control unit 41 and the path function unit 12. All of the branched optical signals are the same signal (an optical signal containing multiple wavelengths).

[0058] The first branching unit 51 may output the signal output from the optical fiber 3 to all ports (three ports in the illustrated example) destined for the multiplexing / demultiplexing unit 13. In this case, the multiplexing / demultiplexing unit 13 extracts only the optical signal of the wavelength corresponding to that port at each port, wavelength multiplexes the optical signals extracted at each port, and outputs them to the path function unit 12. The first control unit 41 extracts and receives only the control signal from the signal output from the first branching unit 51.

[0059] As a modification, the first branching unit 51 may output the signal output from the optical fiber 3 to one port for the multiplexing / demultiplexing unit 13. In this case, the multiplexing / demultiplexing unit 13 separates the optical signal output from one port, extracts only the optical signal excluding the control signal, combines the extracted optical signal, and outputs it to the path function unit 12.

[0060] Alternatively, the first branching unit 51 may decouple the optical signal output from the optical fiber 3, output a control signal to the first control unit 41, and output optical signals of each wavelength other than the control signal to the corresponding ports of the multiplexing / demultiplexing unit 13.

[0061] Figure 8 shows the configuration of an optical communication system in a comparative example of this embodiment. The ROADM section of the comparative example's optical communication system includes an optical amplification section, a path function section, and a multiplexing / demultiplexing function section. The multiplexing / demultiplexing function section separates the wavelength-multiplexed optical signal and outputs it to an optical fiber (optical fiber core). Therefore, in the comparative example, the number of optical fibers required between the ROADM section and the transponder is equal to the number of transponders. In the illustrated example, three transponders are arranged, so the number of optical fibers required is three. In contrast, in the embodiment shown in Figures 6 and 7, the first branching section 51 recombines the optical signal separated by the multiplexing / demultiplexing function section 13, so the number of optical fibers required is one, and the number of optical fibers can be reduced. This reduces the cost of system construction.

[0062] The optical transmission device of the second embodiment described above is an optical transmission device that communicates with a plurality of transponders 2 located at a user site via an optical fiber 3, and comprises an optical amplification unit 11 that amplifies an optical signal obtained by combining a plurality of wavelengths, a path function unit 12 that outputs the amplified optical signal to a multiplexing / demultiplexing function unit 13, the multiplexing / demultiplexing function unit 13 that demultiplexes the optical signal output from the path function unit 12 into a plurality of optical signals for each wavelength, and a first branching unit 51 that combines the multiple demultiplexed optical signals and outputs them to the optical fiber 3.

[0063] In this embodiment, the first branching unit 51 combines multiple optical signals separated by the signal-combining / demultiplexing unit 13 and outputs them to the optical fiber 3. This makes it possible to reduce the number of optical fibers 3 between the optical transmission device and the spaced-apart transponders 2 in this embodiment.

[0064] Specifically, a typical ROADM unit has a configuration in which the multiplexing / demultiplexing unit houses the transponders. When the optical signal passing through the multiplexing / demultiplexing unit contains multiple wavelengths, it separates the optical signal into individual wavelengths and transmits each separated optical signal to each transponder via a different optical fiber. Therefore, when transmitting an optical signal containing multiple wavelengths to multiple transponders spaced apart at the same user site (e.g., a user building), it is necessary to prepare an optical fiber for inter-building transmission for each wavelength (for each transponder). In contrast, in this embodiment, the first branching unit 51 recombines the multiple optical signals separated by the multiplexing / demultiplexing unit 13, thereby reducing the number of optical fibers required and lowering the cost of system construction.

[0065] The optical transmission devices of the first and second embodiments described above can use, for example, a general-purpose computer system like the one shown in Figure 9. The illustrated computer system includes a CPU (Central Processing Unit, processor) 901, a memory 902, a storage device 903 (HDD: Hard Disk Drive, SSD: Solid State Drive), a communication device 904, an input device 905, and an output device 906. The memory 902 and the storage device 903 are storage devices. In this computer system, the functions of the optical transmission device are realized by the CPU 901 executing a predetermined program loaded onto the memory 902.

[0066] Furthermore, the optical transmission device may be implemented on one computer or on multiple computers. The optical transmission device may also be a virtual machine implemented on a computer. The program for the optical transmission device can be stored on computer-readable recording media such as HDDs, SSDs, USB (Universal Serial Bus) memory, CDs (Compact Discs), and DVDs (Digital Versatile Discs), or distributed over a network. Computer-readable recording media are, for example, non-transitory recording media.

[0067] This disclosure is not limited to the embodiments described above, and numerous modifications are possible within the scope of its essence. For example, although the above embodiment describes a case where the transponder 2 is placed at a distance from the user site, a pluggable module (coherent pluggable module) may be placed at a distance instead of the transponder 2. The pluggable module is mounted on user equipment at the user site and is a module that converts optical signals and electrical signals to each other, similar to the transponder 2.

[0068] 1: ROADM section 11: Optical amplification section 12: Directional function section 13: Multiplexing / demultiplexing function section 2: Transponder 3: Optical fiber 41: First control section 42: Second control section 51: First branching section (optical coupler) 52: Second branching section (optical coupler) 6: Optical switch

Claims

1. An optical communication system comprising an optical transmission device and a transponder located at a user site, wherein the transponder communicates with the optical transmission device via an optical fiber, and the optical transmission device comprises an optical amplification unit for amplifying an optical signal, a port for housing the transponder and a path function unit for outputting the amplified optical signal to the port, and an optical coupler for outputting the optical signal output from the port to the optical fiber.

2. The optical communication system according to claim 1, comprising a plurality of transponders and another optical coupler located at the user site, which outputs optical signals transmitted via the optical fiber to the plurality of transponders.

3. The optical communication system according to claim 2, wherein the optical coupler outputs an optical signal to the optical fiber obtained by superimposing an optical signal output from the port and a control signal output from a control device connected to the optical transmission device, and the other optical coupler outputs the superimposed optical signal to each transponder and other control devices connected to each transponder.

4. The optical communication system according to claim 2, wherein the other optical coupler having wavelength-specific transmission and blocking functions separates the optical signal, which includes multiple wavelengths and is output from the optical fiber, by wavelength, and outputs each of the separated optical signals to a corresponding transponder.

5. An optical transmission device that communicates with a transponder located at a user site via an optical fiber, comprising: an optical amplification unit for amplifying an optical signal; a path function unit having a port for housing the transponder and outputting the amplified optical signal to the port; and an optical coupler for outputting the optical signal output from the port to the optical fiber.

6. An optical transmission device for communicating with multiple transponders located at a user site via an optical fiber, comprising: an optical amplification unit for amplifying an optical signal obtained by combining multiple wavelengths; a path function unit for outputting the amplified optical signal to a multiplexing / demultiplexing function unit; a multiplexing / demultiplexing function unit for demultiplexing the optical signal output from the path function unit into multiple optical signals for each wavelength; and an optical coupler for combining the multiple demultiplexed optical signals and outputting them to the optical fiber.

7. An optical communication method for communicating with a transponder located at a user site via an optical fiber, wherein an optical amplification unit amplifies an optical signal, a path function unit outputs the amplified optical signal to a port housing the transponder, and an optical coupler outputs the optical signal output from the port to the optical fiber.

8. A program for causing a computer to function as an optical transmission device according to claim 5 or claim 6.

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