Optical waveform control device, optical transmission system, and optical waveform control method

Abstract

As control becomes complicated when the terminal point of an optical signal propagating through an optical submarine cable is extended in an optical transmission system, this optical waveform control device is provided with: a communication means for communicating with each of a plurality of optical devices including at least a first optical device and a second optical device located at a post-stage of the first optical device; an optical signal noise ratio acquisition means for receiving, via the communication means, an individual optical signal noise ratio that is an optical signal noise ratio per wavelength channel of a wavelength multiplexed optical signal propagating through the plurality of optical devices and an average optical signal noise ratio that is the average of the individual optical signal noise ratios; a first control means for controlling the optical output power of the first optical device via the communication means so that the optical input power of an optical amplifier that the second optical device includes becomes a prescribed value; and a second control means for controlling at least one of the plurality of optical devices via the communication means so that the individual optical signal noise ratio becomes equal to the average optical signal noise ratio.

Description

Optical waveform control device, optical transmission system, and optical waveform control method

[0001] The present invention relates to an optical waveform control device, an optical transmission system, and an optical waveform control method, and more particularly to an optical waveform control device, an optical transmission system, and an optical waveform control method used together with an optical submarine cable system.

[0002] Optical submarine cable systems that connect continents with optical fibers play an important role as infrastructure supporting international communication networks. An optical submarine cable system is composed of submarine cables that accommodate optical fibers, submarine repeaters equipped with optical amplifiers, submarine branching devices that branch optical signals, and terminal equipment installed at landing stations. An example of such an optical submarine cable system is described in Patent Document 1.

[0003] Special table 2019-517169 publication

[0004] In optical submarine cable systems, an increase in communication traffic between data centers, etc., has led to problems of increased delay and power consumption due to the termination of optical signals (optical paths) at cable landing stations (CLSs). To avoid these problems, there is a demand to extend the termination point of optical signals propagating through optical submarine cables from the landing stations (CLSs) to connection points (Points of Presence: POPs) with customer data centers or backbone networks installed inland.

[0005] In this case, the distance from the landing station (CLS) to the data center or POP can be several hundred kilometers, which requires long-distance terrestrial optical transmission with an in-line amplifier (ILA). Meanwhile, wavelength-multiplexed optical signals propagating through optical submarine cables are required to have a constant optical signal-to-noise ratio (OSNR) for each wavelength channel.

[0006] However, the characteristics of optical fibers laid on land vary greatly depending on the type of optical fiber used and the degree of aging degradation. Therefore, in order to maintain a constant optical signal-to-noise ratio (OSNR) for each wavelength channel, it is necessary to adjust the settings of optical amplifiers and wavelength selective switches (WSSs) provided in landing stations (CLSs), in-line amplifiers (ILAs), and POP devices. In this case, adjustments must be made at all landing stations (CLSs), in-line amplifiers (ILAs), and POP devices, requiring complex control.

[0007] As described above, in an optical transmission system, when the termination point of an optical signal propagating through an optical submarine cable is extended, there is a problem in that control becomes complicated.

[0008] An object of the present invention is to provide an optical waveform control device, an optical transmission system, and an optical waveform control method that solve the above-mentioned problem that, in an optical transmission system, control becomes complicated when the termination point of an optical signal propagating through an optical submarine cable is extended.

[0009] The optical waveform control device of the present invention comprises a communication means for communicating with each of a plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device, an optical signal to noise ratio acquisition means for receiving, via the communication means, an individual optical signal to noise ratio, which is the optical signal to noise ratio for each wavelength channel of a wavelength-multiplexed optical signal propagating through the plurality of optical devices, and an average optical signal to noise ratio, which is the average of the individual optical signal to noise ratios, a first control means for controlling the optical output power of the first optical device via the communication means so that the optical input power of an optical amplifier provided in the second optical device becomes a predetermined value, and a second control means for controlling at least one of the plurality of optical devices via the communication means so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio.

[0010] The optical transmission system of the present invention comprises a plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device, and an optical waveform control device, wherein the second optical device comprises an optical amplifier, and the optical waveform control device comprises communication means for communicating with each of the plurality of optical devices, optical signal-to-noise ratio acquisition means for receiving, via the communication means, an individual optical signal-to-noise ratio which is the optical signal-to-noise ratio for each wavelength channel of a wavelength-multiplexed optical signal propagating through the plurality of optical devices, and an average optical signal-to-noise ratio which is the average of the individual optical signal-to-noise ratios, first control means for controlling the optical output power of the first optical device via the communication means so that the optical input power of the optical amplifier becomes a predetermined value, and second control means for controlling at least one of the plurality of optical devices via the communication means so that the individual optical signal-to-noise ratio becomes equal to the average optical signal-to-noise ratio.

[0011] The optical waveform control method of the present invention receives an individual optical signal to noise ratio, which is the optical signal to noise ratio for each wavelength channel, and an average optical signal to noise ratio, which is the average of the individual optical signal to noise ratios, of a wavelength-multiplexed optical signal propagating through a plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device, controls the optical output power of the first optical device so that the optical input power of an optical amplifier provided in the second optical device becomes a predetermined value, and controls at least one of the plurality of optical devices so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio.

[0012] According to the optical waveform control device, optical transmission system, and optical waveform control method of the present invention, it is possible to simplify control in an optical transmission system even when the termination point of an optical signal propagating through an optical submarine cable is extended.

[0013] FIG. 1 is a block diagram showing the configuration of an optical waveform controller according to a first embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of an optical transmission system including the optical waveform controller according to the first embodiment of the present invention. FIG. 3 is a flowchart illustrating an optical waveform control method according to the first embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of an optical transmission system including the optical waveform controller according to a second embodiment of the present invention. FIG. 5 is a diagram showing the optical spectrum of a wavelength-multiplexed optical signal transmitted by a first optical device constituting the optical transmission system according to the second embodiment of the present invention. FIG. 6 is a diagram showing the optical spectrum of a wavelength-multiplexed optical signal in a third optical device constituting the optical transmission system according to the second embodiment of the present invention. FIG. 7 is a flowchart illustrating an optical waveform control method according to the second embodiment of the present invention. FIG. 8 is a block diagram showing the configuration of an optical transmission system including the optical waveform controller according to a third embodiment of the present invention. FIG. 9 is a diagram showing the optical spectrum of a wavelength-multiplexed optical signal transmitted by a first optical device constituting the optical transmission system according to the third embodiment of the present invention. FIG. 10 is a diagram showing the optical spectrum of a wavelength-multiplexed optical signal in a third optical device constituting the optical transmission system according to the third embodiment of the present invention. FIG. 11 is a block diagram showing another configuration of an optical transmission system including the optical waveform controller according to the third embodiment of the present invention. FIG. 12 is a flowchart illustrating an optical waveform control method according to the third embodiment of the present invention.

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] 1 is a block diagram showing the configuration of an optical waveform controller 100 according to a first embodiment of the present invention. Optical waveform controller 100 has a communication unit (communication means) 110, an optical signal-to-noise ratio acquisition unit (optical signal-to-noise ratio acquisition means) 120, a first control unit (first control means) 130, and a second control unit (second control means) 140. Optical waveform controller 100 is preferably used together with an optical submarine cable system.

[0016] The communication unit 110 communicates with a plurality of optical devices, each of which includes at least a first optical device and a second optical device located downstream of the first optical device. The optical signal-to-noise ratio acquisition unit 120 receives an individual optical signal-to-noise ratio and an average optical signal-to-noise ratio via the communication unit 110. Here, the individual optical signal-to-noise ratio is the optical signal-to-noise ratio (OSNR) for each wavelength channel of a wavelength-multiplexed optical signal propagating through the plurality of optical devices. The average optical signal-to-noise ratio is the average of the individual optical signal-to-noise ratios.

[0017] The first control unit 130 controls the optical output power of the first optical device via the communication unit 110 so that the optical input power of the optical amplifier included in the second optical device becomes a predetermined value. The second control unit 140 then controls at least one of the plurality of optical devices via the communication unit 110 so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio. This makes it possible to optimize and maintain a constant optical signal to noise ratio (OSNR) for each wavelength channel in the wavelength-multiplexed optical signal.

[0018] As described above, in the optical waveform controller 100 of this embodiment, the optical signal-to-noise ratio acquiring unit 120 receives the individual optical signal-to-noise ratio and the average optical signal-to-noise ratio, and the first control unit 130 and the second control unit 140 control multiple optical devices. Therefore, it is not necessary to individually adjust the equipment included in multiple optical devices, such as a landing station (CLS), an in-line amplifier (ILA), and a POP device. As a result, control can be simplified in the optical transmission system.

[0019] 2 shows the configuration of an optical transmission system 1000 equipped with an optical waveform controller according to this embodiment. The optical transmission system 1000 has a plurality of optical devices including at least a first optical device 1100 and a second optical device 1200 located after the first optical device 1100, and an optical waveform controller 1400. The configuration of the optical waveform controller 1400 is similar to the configuration of the optical waveform controller 100 described above. FIG. 2 also shows a third optical device 1300 located at the last stage of the plurality of optical devices.

[0020] Here, a plurality of optical devices including a first optical device 1100, a second optical device 1200, and a third optical device 1300 are connected to each other via optical fibers installed on land.

[0021] The first optical device 1100 is typically installed at a point of presence (POP) at a data center or a connection point with a backbone network. The second optical device 1200 may be configured to include an optical amplifier 1210 such as an in-line amplifier (ILA). The third optical device 1300 may typically be installed at a cable landing station (CLS) of an optical submarine cable system and connected to an optical submarine cable laid on the seabed. With this configuration, the termination point of an optical signal propagating through the optical submarine cable can be extended to a data center or POP.

[0022] The communication unit 1410 (110 in FIG. 1) included in the optical waveform controller 1400 communicates with multiple optical devices using an in-band communication signal 20 via an optical transmission path along which the wavelength-multiplexed optical signal 10 propagates. This allows the optical waveform controller 1400 to acquire optical signal information of the wavelength-multiplexed optical signal 10 from the multiple optical devices and, based on this information, configure equipment such as optical amplifiers and wavelength selective switches (WSSs) included in each optical device. Specifically, for example, a configuration may be adopted in which optical transceivers are installed in ports of switching hubs (Layer 2 switches) connected to the first optical device 1100, the second optical device 1200, and the third optical device 1300. Using these optical transceivers, optical signal information can be acquired via the optical transmission path using the in-band communication signal 20, and the equipment can be configured.

[0023] The third optical device 1300 can be configured to include an optical channel monitor (OCM) or an optical spectrum analyzer (OSA). The optical signal to noise ratio acquiring unit 120 (see FIG. 1 ) included in the optical waveform controller 1400 can acquire the individual optical signal to noise ratio and the average optical signal to noise ratio from the optical channel monitor (OCM) or the optical spectrum analyzer (OSA) via the communication unit 110.

[0024] As described above, the first control unit 130 (see FIG. 1 ) included in the optical waveform controller 1400 controls the optical output power of the first optical device 1100 via the communication unit 1410 so that the optical input power of the optical amplifier 1210 included in the second optical device 1200 becomes a predetermined value. The optical amplifier 1210 is typically an amplifier using an erbium-doped fiber (Erbium Doped Fiber Amplifier: EDFA).

[0025] The predetermined value of the optical input power of the optical amplifier 1210 can be an optical input power value optimized to maximize the average optical signal-to-noise ratio. Here, the average optical signal-to-noise ratio is the average of the individual optical signal-to-noise ratios in the wavelength band of the wavelength-multiplexed optical signal 10, as described above. When the optical input power of the optical amplifier 1210 changes, the wavelength dependence of the gain profile of the optical amplifier 1210 also changes. Therefore, there exists an optical input power value optimized to maximize the average optical signal-to-noise ratio depending on the gain characteristics of the optical amplifier 1210.

[0026] As described above, the second control unit 140 included in the optical waveform controller 1400 controls at least one of the plurality of optical devices via the communication unit 110 so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio. This makes it possible to make the optical signal to noise ratio (OSNR) of each wavelength channel in the wavelength-multiplexed optical signal 10 optimal and constant.

[0027] Next, the optical waveform control method according to this embodiment will be described with reference to the flowchart shown in FIG.

[0028] In the optical waveform control method according to this embodiment, first, an individual optical signal to noise ratio (OSNR) and an average optical signal to noise ratio (ASNNR) of a wavelength-multiplexed optical signal propagating through a plurality of optical devices are received (step S110). Here, the plurality of optical devices include at least a first optical device and a second optical device located downstream of the first optical device. The individual OSNR is the OSNR for each wavelength channel of the wavelength-multiplexed optical signal. The average OSNR is the average of the individual OSNRs.

[0029] The optical output power of the first optical device (the optical device at the preceding stage) is controlled so that the optical input power of the optical amplifier included in the second optical device becomes a predetermined value (step S120), and at least one of the plurality of optical devices is controlled so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio (step S130).

[0030] In step S110, for example, the optical signal to noise ratio acquisition unit performs the operation. In step S120, for example, the first control unit performs the operation. In step S130, for example, the second control unit performs the operation.

[0031] As described above, the optical waveform control method of this embodiment is configured to receive individual optical signal-to-noise ratios and average optical signal-to-noise ratios and control multiple optical devices. Therefore, it is not necessary to individually adjust the equipment included in multiple optical devices, such as landing stations (CLSs), in-line amplifiers (ILAs), and POP devices. As a result, control can be simplified in optical transmission systems.

[0032] The predetermined value of the optical input power of the optical amplifier mentioned above is an optical input power value optimized to maximize the average optical signal-to-noise ratio.

[0033] The optical communication device may further communicate with a plurality of optical devices by an in-band method via an optical transmission line through which a wavelength-multiplexed optical signal propagates.

[0034] As described above, according to the optical waveform controller 100, optical transmission system 1000, and optical waveform control method of this embodiment, it is possible to simplify control in an optical transmission system even when the termination point of an optical signal propagating through an optical submarine cable is extended.

[0035] Second Embodiment Next, a second embodiment of the present invention will be described. The configuration of an optical waveform controller according to this embodiment is similar to the configuration of optical waveform controller 100 according to the first embodiment shown in Fig. 1. That is, optical waveform controller 100 has a communication unit (communication means) 110, an optical signal-to-noise ratio acquisition unit (optical signal-to-noise ratio acquisition means) 120, a first control unit (first control means) 130, and a second control unit (second control means) 140. Optical waveform controller 100 is preferably used together with an optical submarine cable system.

[0036] The communication unit 110 communicates with a plurality of optical devices, each of which includes at least a first optical device and a second optical device located downstream of the first optical device. The optical signal-to-noise ratio acquisition unit 120 receives an individual optical signal-to-noise ratio and an average optical signal-to-noise ratio via the communication unit 110. Here, the individual optical signal-to-noise ratio is the optical signal-to-noise ratio (OSNR) for each wavelength channel of a wavelength-multiplexed optical signal propagating through the plurality of optical devices. The average optical signal-to-noise ratio is the average of the individual optical signal-to-noise ratios.

[0037] The first control unit 130 controls the optical output power of the first optical device via the communication unit 110 so that the optical input power of the optical amplifier included in the second optical device becomes a predetermined value. The second control unit 140 controls at least one of the plurality of optical devices via the communication unit 110 so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio.

[0038] In the optical waveform control device of this embodiment, the first control unit (first control means) 130 controls the optical output power of the first optical device by controlling the optical attenuator provided in the first optical device.

[0039] 4 shows the configuration of an optical transmission system 2000 equipped with an optical waveform controller according to this embodiment. The optical transmission system 2000 includes a plurality of optical devices including at least a first optical device 1100 and a second optical device 1200 located after the first optical device 1100, and an optical waveform controller 1400. The configuration of the optical waveform controller 1400 is similar to that of the optical waveform controller 100 described above. FIG. 4 also shows a second optical device 2200 included in the plurality of optical devices and a third optical device 1300 located at the final stage of the plurality of optical devices. Because the second optical device 2200 is located after the second optical device 1200, the second optical device 1200 functions as the first optical device 2100 in relation to the second optical device 2200.

[0040] Here, the first optical device 1100 is typically installed at a data center or a point of presence (POP) with a backbone network. The third optical device 1300 is typically installed at a landing station (CLS) of an optical submarine cable system and can be configured to connect to an optical submarine cable installed on the seabed. With this configuration, the termination point of the optical signal propagating through the optical submarine cable can be extended to the data center or POP.

[0041] In the optical transmission system 2000, the first optical devices 1100 and 2100 are equipped with optical attenuators 1110 and 2110, and the second optical devices 1200 and 2200 are equipped with optical amplifiers 1210 and 2210. The second optical device 2200 is located before the third optical device 1300, which is the last stage. Therefore, the second optical device 2200 functions as the first optical device with respect to the third optical device 1300, and therefore a configuration including an optical attenuator 2111 is shown.

[0042] The optical attenuators 1110, 2110, and 2111 are typically variable optical attenuators (VOA). Alternatively, wavelength selective switches (WSS) may be used as the optical attenuators 1110, 2110, and 2111.

[0043] As described above, the first control unit 130 (see FIG. 1 ) included in the optical waveform controller 1400 controls the optical output power of the first optical devices 1100 and 2100 so that the optical input power of the optical amplifiers 1210 and 2210 included in the second optical devices 1200 and 2200 becomes a predetermined value. At this time, the first control unit 130 controls the optical output power of the first optical devices 1100 and 2100 by controlling the optical attenuators 1110 and 2110 included in the first optical devices 1100 and 2100. Here, the predetermined value of the optical input power of the optical amplifiers 1210 and 2210 is an optical input power value optimized to maximize the average optical signal-to-noise ratio.

[0044] The optical input power of the optical amplifiers 1210 and 2210 is adjusted by the first control unit 130 starting with the optical device on the sending side of the wavelength-multiplexed optical signal 10 and sequentially controlling the optical devices at the subsequent stages, thereby optimizing all of the optical amplifiers 1210 and 2210 and maximizing the average optical signal-to-noise ratio.

[0045] Figure 5A shows an example of the optical spectrum of wavelength-multiplexed optical signal 10 transmitted by first optical device 1100, which is located at the first stage among multiple optical devices. As shown in Figure 5A, dummy light can be used as wavelength-multiplexed optical signal 10, which is shaped into a comb-shaped waveform by controlling the band of amplified spontaneous emission (ASE) to either odd or even channels. Figure 5B shows an example of the optical spectrum of wavelength-multiplexed optical signal 10 transmitted by third optical device 1300, which is located at the last stage. Here, wavelength-multiplexed optical signal 10 has the maximum average optical signal-to-noise ratio.

[0046] As described above, the second control unit 140 included in the optical waveform controller 1400 controls at least one of the plurality of optical devices via the communication unit 110 so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio. This makes it possible to make the optical signal to noise ratio (OSNR) of each wavelength channel in the wavelength-multiplexed optical signal 10 optimal and constant.

[0047] Next, the optical waveform control method according to this embodiment will be described with reference to the flowchart shown in FIG.

[0048] In the optical waveform control method according to this embodiment, first, an individual optical signal to noise ratio (OSNR) and an average optical signal to noise ratio (ASNNR) of a wavelength-multiplexed optical signal propagating through a plurality of optical devices are received (step S110). Here, the plurality of optical devices include at least a first optical device and a second optical device located downstream of the first optical device. The individual OSNR is the OSNR for each wavelength channel of the wavelength-multiplexed optical signal. The average OSNR is the average of the individual OSNRs.

[0049] Furthermore, the optical output power of the first optical device is controlled so that the optical input power of the optical amplifier included in the second optical device becomes a predetermined value. At this time, in the optical waveform control method according to this embodiment, the optical attenuator included in the first optical device (the optical device at the preceding stage) is controlled (step S220).

[0050] Then, at least one of the plurality of optical devices is controlled so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio (step S130).

[0051] In step S110, for example, the optical signal to noise ratio acquisition unit performs the operation. In step S220, for example, the first control unit performs the operation. In step S130, for example, the second control unit performs the operation.

[0052] As described above, the optical waveform control method of this embodiment is configured to receive individual optical signal-to-noise ratios and average optical signal-to-noise ratios and control multiple optical devices. Therefore, it is not necessary to individually adjust the equipment included in multiple optical devices, such as landing stations (CLSs), in-line amplifiers (ILAs), and POP devices. As a result, control can be simplified in optical transmission systems.

[0053] As described above, according to the optical waveform control device, optical transmission system 2000, and optical waveform control method of this embodiment, it is possible to simplify control in an optical transmission system even when the termination point of an optical signal propagating through an optical submarine cable is extended.

[0054] [Third Embodiment] Next, a third embodiment of the present invention will be described. The configuration of an optical waveform controller according to this embodiment is similar to the configuration of optical waveform controller 100 according to the first embodiment shown in Fig. 1. That is, optical waveform controller 100 has a communication unit (communication means) 110, an optical signal-to-noise ratio acquisition unit (optical signal-to-noise ratio acquisition means) 120, a first control unit (first control means) 130, and a second control unit (second control means) 140. Optical waveform controller 100 is preferably used together with an optical submarine cable system.

[0055] The communication unit 110 communicates with a plurality of optical devices, each of which includes at least a first optical device and a second optical device located downstream of the first optical device. The optical signal to noise ratio acquisition unit 120 receives the individual optical signal to noise ratio (OSNR) and the average optical signal to noise ratio (AMNR) via the communication unit 110. Here, the individual optical signal to noise ratio (ASNR) is the optical signal to noise ratio (OSNR) for each wavelength channel of a wavelength-multiplexed optical signal propagating through the plurality of optical devices. The average optical signal to noise ratio (AMNR) is the average of the individual optical signal to noise ratios.

[0056] The first control unit 130 controls the optical output power of the first optical device via the communication unit 110 so that the optical input power of the optical amplifier included in the second optical device becomes a predetermined value. The second control unit 140 controls at least one of the plurality of optical devices via the communication unit 110 so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio.

[0057] In the optical waveform control device of this embodiment, the second control unit (second control means) 140 controls the dummy light generator provided in at least one of the multiple optical devices, and adjusts the optical intensity of the dummy light emitted by this dummy light generator.

[0058] Fig. 7 shows the configuration of an optical transmission system 3000 equipped with an optical waveform controller according to this embodiment. The optical transmission system 3000 has a plurality of optical devices including at least a first optical device 1100 and a second optical device 1200 located after the first optical device 1100, and an optical waveform controller 1400. At least one of the plurality of optical devices is configured to include a dummy light generator. Fig. 7 shows a configuration in which the first optical device 1100 located at the first stage of the plurality of optical devices is configured to include a dummy light generator 3110. The rest of the configuration is similar to that of the optical transmission system 2000 according to the second embodiment.

[0059] Here, the first optical device 1100 is typically installed at a data center or a point of presence (POP) with a backbone network. The third optical device 1300 is typically installed at a landing station (CLS) of an optical submarine cable system and can be configured to connect to an optical submarine cable installed on the seabed. With this configuration, the termination point of the optical signal propagating through the optical submarine cable can be extended to the data center or POP.

[0060] The dummy light generator 3110 generates dummy light. As the dummy light generator 3110, for example, an ASE (Amplified Spontaneous Emission) light source in which an amplifier using an erbium-doped fiber (Erbium Doped Fiber Amplifier: EDFA) is in a state where no input signal is input can be used.

[0061] As described above, the second control unit 140 (see FIG. 1 ) included in the optical waveform controller 1400 controls at least one of the plurality of optical devices via the communication unit 1410 so that the individual optical signal-to-noise ratio becomes equal to the average optical signal-to-noise ratio. At this time, the second control unit 140 controls the dummy light generator 3110 to adjust the optical intensity of the dummy light output by the dummy light generator 3110.

[0062] That is, the second control unit 140 controls the dummy light generator 3110 to adjust each peak level of the wavelength-multiplexed optical signal 10 so that the value of the individual optical signal to noise ratio is equal across the wavelength band of the wavelength-multiplexed optical signal 10. Here, the optical signal to noise ratio acquiring unit 120 included in the optical waveform controller 1400 receives the individual optical signal to noise ratio and the average optical signal to noise ratio via the communication unit 110.

[0063] The second control unit 140 adjusts the peak levels of the wavelength-multiplexed optical signal 10, for example, as follows: That is, if the individual optical signal to noise ratio of the target optical signal peak is higher than the average optical signal to noise ratio, the second control unit 140 controls the dummy light generator 3110 to reduce the peak level by the difference amount. On the other hand, if the individual optical signal to noise ratio of the target optical signal peak is lower than the average optical signal to noise ratio, the second control unit 140 controls the dummy light generator 3110 to increase the peak level by the difference amount.

[0064] 8A shows an example of the optical spectrum of wavelength-multiplexed optical signal 10 transmitted by dummy light generator 3110 after second control unit 140 has adjusted each peak level. Fig. 8B shows an example of the optical spectrum of wavelength-multiplexed optical signal 10 transmitted through an optical fiber connecting multiple optical devices to third optical device 1300 at the final stage. As can be seen from the figure, the optical waveform controller and optical transmission system 3000 of this embodiment can maintain a constant optical signal-to-noise ratio (OSNR) for each wavelength channel of wavelength-multiplexed optical signal 10.

[0065] In the above description, the optical waveform controller 1400 is configured such that the second control unit 140 controls a dummy light generator included in at least one of the plurality of optical devices and adjusts the optical intensity of the dummy light output from the dummy light generator. However, the present invention is not limited to this, and the second control unit 140 may be configured such that the second control unit 140 controls a wavelength selective switch (WSS) included in at least one of the plurality of optical devices and adjusts the optical intensity of the wavelength-multiplexed optical signal 10 output from the wavelength selective switch.

[0066] Fig. 9 shows the configuration of an optical transmission system 3001 equipped with an optical waveform control device having such a configuration. In the optical transmission system 3001, at least one of a plurality of optical devices is equipped with a wavelength selective switch (WSS). Fig. 9 shows a configuration in which a second optical device 3200 is equipped with a wavelength selective switch 3210. Even in a configuration using the wavelength selective switch 3210, the optical signal to noise ratio (OSNR) of each wavelength channel of the wavelength-multiplexed optical signal 10 can be kept constant.

[0067] Next, the optical waveform control method according to this embodiment will be described with reference to the flowchart shown in FIG.

[0068] In the optical waveform control method according to this embodiment, first, an individual optical signal to noise ratio (OSNR) and an average optical signal to noise ratio (ASNNR) of a wavelength-multiplexed optical signal propagating through a plurality of optical devices are received (step S110). Here, the plurality of optical devices include at least a first optical device and a second optical device located downstream of the first optical device. The individual OSNR is the OSNR for each wavelength channel of the wavelength-multiplexed optical signal. The average OSNR is the average of the individual OSNRs.

[0069] Also, the optical output power of the first optical device (the optical device at the preceding stage) is controlled so that the optical input power of the optical amplifier included in the second optical device becomes a predetermined value (step S120).

[0070] At least one of the plurality of optical devices is controlled so that the individual optical signal to noise ratio is equal to the average optical signal to noise ratio. In this case, in the optical waveform control method according to the present embodiment, the optical intensity of the dummy light outputted by the dummy light generator included in at least one of the plurality of optical devices is adjusted (step S331). However, it is not limited to this, and the optical intensity of the wavelength-multiplexed optical signal outputted by the wavelength selective switch included in at least one of the plurality of optical devices may also be adjusted (step S332).

[0071] For example, the optical signal to noise ratio acquiring unit performs the operation in step S110, the first control unit performs the operation in step S120, and the second control unit performs the operation in steps S331 and S332.

[0072] As described above, the optical waveform control method of this embodiment is configured to receive individual optical signal-to-noise ratios and average optical signal-to-noise ratios and control multiple optical devices. Therefore, it is not necessary to individually adjust the equipment included in multiple optical devices, such as landing stations (CLSs), in-line amplifiers (ILAs), and POP devices. As a result, control can be simplified in optical transmission systems.

[0073] Furthermore, in the optical waveform control method of this embodiment, controlling the optical output power can include controlling the optical output power before and after the step of controlling at least one of the plurality of optical devices. Figure 11 shows a flowchart of the optical waveform control method in such a configuration. The step of controlling the optical output power (S120) may also be configured to control the optical output power before and after the step of controlling an optical device such as a dummy light generator or a wavelength selective switch (S330).

[0074] Specifically, after the step of controlling optical devices such as a dummy light generator or a wavelength selective switch (S330), it is determined whether a predetermined condition is met (S340). Here, the predetermined condition may be, for example, that the difference between the individual optical signal to noise ratio and the average optical signal to noise ratio is equal to or less than a predetermined amount over the entire wavelength band of the wavelength-multiplexed optical signal. Alternatively, the predetermined condition may be that steps S120 and S330 have been performed a predetermined number of times. If the predetermined condition is met (YES in step S340), the process ends. If the predetermined condition is not met (NO in step S340), the process returns to the step of controlling the optical output power (S120).

[0075] The step (S330) of controlling the optical devices so that the individual optical signal-to-noise ratio is equal to the average optical signal-to-noise ratio may cause the optical input power of the optical amplifier to deviate from a predetermined value. However, even in such a case, the optical waveform control method shown in Figure 11 can optimize the optical input power by again performing the step (S120) of controlling the optical output power of the upstream optical device.

[0076] As described above, according to the optical waveform control device, optical transmission system 3000, and optical waveform control method of this embodiment, it is possible to simplify control in an optical transmission system even when the termination point of an optical signal propagating through an optical submarine cable is extended.

[0077] A part or all of the above-described embodiments can be described as, but not limited to, the following supplementary notes.

[0078] (Supplementary Note 1) An optical waveform control device comprising: communication means for communicating with each of a plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device; optical signal to noise ratio acquisition means for receiving, via the communication means, an individual optical signal to noise ratio which is the optical signal to noise ratio for each wavelength channel of a wavelength-multiplexed optical signal propagating through the plurality of optical devices, and an average optical signal to noise ratio which is the average of the individual optical signal to noise ratios; first control means for controlling, via the communication means, the optical output power of the first optical device so that the optical input power of an optical amplifier provided in the second optical device becomes a predetermined value; and second control means for controlling, via the communication means, at least one of the plurality of optical devices so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio.

[0079] (Supplementary Note 2) The optical waveform control device according to Supplementary Note 1, wherein the first control means controls the optical output power of the first optical device by controlling an optical attenuator provided in the first optical device.

[0080] (Appendix 3) An optical waveform control device as described in Appendix 1 or 2, wherein the second control means controls a dummy light generator provided in at least one of the plurality of optical devices, and adjusts the optical intensity of the dummy light emitted by the dummy light generator.

[0081] (Appendix 4) An optical waveform control device as described in appendix 1 or 2, wherein the second control means controls a wavelength selective switch provided in at least one of the plurality of optical devices, and adjusts the optical intensity of the wavelength-multiplexed optical signal output by the wavelength selective switch.

[0082] (Appendix 5) An optical waveform control device according to any one of appendices 1 to 4, wherein the communication means communicates with the plurality of optical devices by an in-band method via an optical transmission path through which the wavelength-multiplexed optical signal propagates.

[0083] (Supplementary Note 6) The optical waveform control device according to any one of Supplementary Notes 1 to 5, wherein the predetermined value is an optical input power value optimized to maximize the average optical signal-to-noise ratio.

[0084] (Supplementary Note 7) An optical transmission system comprising: a plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device; and an optical waveform control device, wherein the second optical device comprises an optical amplifier, and the optical waveform control device comprises: communication means for communicating with each of the plurality of optical devices; optical signal-to-noise ratio acquisition means for receiving, via the communication means, an individual optical signal-to-noise ratio which is the optical signal-to-noise ratio for each wavelength channel of a wavelength-multiplexed optical signal propagating through the plurality of optical devices, and an average optical signal-to-noise ratio which is the average of the individual optical signal-to-noise ratios; first control means for controlling the optical output power of the first optical device via the communication means so that the optical input power of the optical amplifier becomes a predetermined value; and second control means for controlling at least one of the plurality of optical devices via the communication means so that the individual optical signal-to-noise ratio becomes equal to the average optical signal-to-noise ratio.

[0085] (Appendix 8) An optical transmission system as described in Appendix 7, wherein the first optical device comprises an optical attenuator, and the first control means controls the optical attenuator to control the optical output power of the first optical device.

[0086] (Appendix 9) An optical transmission system as described in Appendix 7 or 8, wherein at least one of the plurality of optical devices is equipped with a dummy light generator, and the second control means controls the dummy light generator and adjusts the optical intensity of the dummy light emitted by the dummy light generator.

[0087] (Appendix 10) An optical transmission system as described in appendix 7 or 8, wherein at least one of the plurality of optical devices is provided with a wavelength selective switch, and the second control means controls the wavelength selective switch to adjust the optical intensity of the wavelength-multiplexed optical signal output by the wavelength selective switch.

[0088] (Supplementary Note 11) The optical transmission system according to any one of Supplementary Notes 7 to 10, wherein the communication means communicates with the plurality of optical devices by an in-band method via an optical transmission path through which the wavelength-multiplexed optical signal propagates.

[0089] (Supplementary Note 12) The optical transmission system according to any one of Supplementary Notes 7 to 11, wherein the predetermined value is an optical input power value optimized to maximize the average optical signal-to-noise ratio.

[0090] (Appendix 13) An optical transmission system according to any one of Appendices 7 to 12, wherein the plurality of optical devices are connected to one another via optical fibers installed on land, and a third optical device located at the last stage of the plurality of optical devices is connected to an optical submarine cable installed on the seabed.

[0091] (Supplementary Note 14) An optical waveform control method that receives an individual optical signal to noise ratio, which is an optical signal to noise ratio for each wavelength channel, of a wavelength-multiplexed optical signal propagating through a plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device, and an average optical signal to noise ratio, which is an average of the individual optical signal to noise ratios, controls the optical output power of the first optical device so that the optical input power of an optical amplifier provided in the second optical device becomes a predetermined value, and controls at least one of the plurality of optical devices so that the individual optical signal to noise ratio becomes equal to the average optical signal to noise ratio.

[0092] (Supplementary Note 15) The optical waveform control method according to Supplementary Note 14, wherein controlling the optical output power includes controlling an optical attenuator provided in the first optical device.

[0093] (Appendix 16) An optical waveform control method described in Appendix 14 or 15, wherein controlling at least one of the plurality of optical devices includes adjusting the optical intensity of dummy light emitted by a dummy light generator provided in at least one of the plurality of optical devices.

[0094] (Appendix 17) An optical waveform control method as described in Appendix 14 or 15, wherein controlling at least one of the plurality of optical devices includes adjusting the optical intensity of the wavelength-multiplexed optical signal output by a wavelength selective switch provided in at least one of the plurality of optical devices.

[0095] (Appendix 18) An optical waveform control method according to any one of Appendices 14 to 17, further comprising communicating with the plurality of optical devices by an in-band method via an optical transmission path through which the wavelength-multiplexed optical signal propagates.

[0096] (Supplementary Note 19) An optical waveform control method according to any one of Supplementary Notes 14 to 18, wherein the predetermined value is an optical input power value optimized to maximize the average optical signal-to-noise ratio.

[0097] (Supplementary Note 20) An optical waveform control method described in any one of Supplementary Notes 14 to 19, wherein controlling the optical output power includes controlling the optical output power before and after a step of controlling at least one of the plurality of optical devices.

[0098] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0099] 100, 1400 Optical waveform control device 110, 1410 Communication unit 120 Optical signal to noise ratio acquisition unit 130 First control unit 140 Second control unit 1000, 2000, 3000, 3001 Optical transmission system 1100, 2100 First optical device 1110, 2110, 2111 Optical attenuator 1200, 2200 Second optical device 1210, 2210 Optical amplifier 1300 Third optical device 3110 Dummy light generator 3210 Wavelength selective switch 10 Wavelength multiplexed optical signal 20 In-band communication signal

Claims

1. a communication means for communicating with each of a plurality of optical devices, the plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device; an optical signal to noise ratio acquiring means for receiving, via the communication means, an individual optical signal to noise ratio, which is an optical signal to noise ratio for each wavelength channel of the wavelength multiplexed optical signal propagating through the plurality of optical devices, and an average optical signal to noise ratio, which is an average of the individual optical signal to noise ratios; a first control means for controlling the optical output power of the first optical device via the communication means so that the optical input power of an optical amplifier included in the second optical device becomes a predetermined value; a second control means for controlling at least one of the plurality of optical devices via the communication means so that the individual optical signal to noise ratio is equal to the average optical signal to noise ratio. Optical waveform control device.

2. The first control means controls the optical output power of the first optical device by controlling an optical attenuator included in the first optical device.

2. An optical waveform control device according to claim 1.

3. The second control means controls a dummy light generator included in at least one of the plurality of optical devices, and adjusts the optical intensity of the dummy light emitted by the dummy light generator.

3. An optical waveform control device according to claim 1 or 2.

4. The second control means controls a wavelength selective switch included in at least one of the plurality of optical devices, and adjusts the optical intensity of the wavelength-multiplexed optical signal transmitted by the wavelength selective switch.

3. An optical waveform control device according to claim 1 or 2.

5. The communication means communicates with the plurality of optical devices by an in-band method via an optical transmission path through which the wavelength-multiplexed optical signal propagates.

3. An optical waveform control device according to claim 1 or 2.

6. The predetermined value is an optical input power value optimized to maximize the average optical signal-to-noise ratio.

3. An optical waveform control device according to claim 1 or 2.

7. a plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device; an optical waveform control device; the second optical device comprises an optical amplifier; The optical waveform control device comprises: communication means for communicating with each of the plurality of optical devices; an optical signal to noise ratio acquiring means for receiving, via the communication means, an individual optical signal to noise ratio, which is an optical signal to noise ratio for each wavelength channel of the wavelength multiplexed optical signal propagating through the plurality of optical devices, and an average optical signal to noise ratio, which is an average of the individual optical signal to noise ratios; a first control means for controlling the optical output power of the first optical device via the communication means so that the optical input power of the optical amplifier becomes a predetermined value; a second control means for controlling at least one of the plurality of optical devices via the communication means so that the individual optical signal to noise ratio is equal to the average optical signal to noise ratio. Optical transmission system.

8. the first optical device comprises an optical attenuator; The first control means controls the optical attenuator to control the optical output power of the first optical device.

8. An optical transmission system according to claim 7.

9. At least one of the plurality of optical devices comprises a dummy light generator; The second control means controls the dummy light generator and adjusts the light intensity of the dummy light emitted by the dummy light generator.

9. An optical transmission system according to claim 7 or 8.

10. receiving an individual optical signal to noise ratio (OSNR) for each wavelength channel of a wavelength-multiplexed optical signal propagating through a plurality of optical devices including at least a first optical device and a second optical device located downstream of the first optical device, and an average optical signal to noise ratio (OSNR) that is an average of the individual optical signal to noise ratios; controlling the optical output power of the first optical device so that the optical input power of the optical amplifier included in the second optical device becomes a predetermined value; controlling at least one of the plurality of optical devices so that the individual optical signal to noise ratio is equal to the average optical signal to noise ratio; Optical waveform control method.