Optical communication system, optical communication control method, and optical communication device

Abstract

To enable span loss adjustment of an optical signal of each wavelength of a wavelength-multiplexed optical signal and adjustment of an intensity difference between the optical signals to be carried out automatically and efficiently.SOLUTION: A control device performs: span loss adjustment processing for controlling optical signal adjustment means on the basis of a first intensity and a third intensity so as to adjust the span loss of a first optical signal, and controlling the optical signal adjustment means on the basis of a second intensity and a fourth intensity so as to adjust the span loss of a second optical signal; and intensity difference adjustment processing for controlling first and second intensity adjustment means so as to adjust an intensity difference between the first optical signal and the second optical signal after span loss adjustment in a second optical communication device. The control device carries out the span loss adjustment processing and the intensity difference adjustment processing as initially set operations after outputting of a third optical signal from the first optical communication device starts, and performs a monitoring operation to repeat the span loss adjustment processing and the intensity difference adjustment processing in a prescribed cycle after the initially set operations are finished.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an optical communication system, an optical signal control method, and an optical communication apparatus.

Background Art

[0002] In an optical communication system, a wavelength division multiplexing (WDM) optical signal obtained by multiplexing optical signals having different wavelengths may be used. At this time, in order to obtain a desired signal quality at the time of reception, suppression of the intensity difference at the time of reception of signals having different wavelengths and compensation for losses in the transmission line may be performed.

[0003] For example, Patent Document 1 proposes a wavelength division multiplexing communication method in which the difference in the optical signal-to-noise ratio of each wavelength of a WDM optical signal at the receiving end is reduced by controlling the pre-emphasis amount of the optical signal at the transmitting end.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the transmission of a WDM optical signal, so-called span loss and optical signals occur. In addition, variations due to wavelength differences occur in the losses of the optical signals of each wavelength of the WDM optical signal after being transmitted through the optical transmission line. Therefore, control is required to keep the intensity of the optical signal of each wavelength after being transmitted through the optical transmission line within a certain range. However, the adjustment of the intensity of the optical signal of each wavelength after being transmitted through the optical transmission line generally requires complicated adjustment work such as manually adjusting the intensity of the optical signal at the time of transmission and the gain of the amplifier provided on the transmission line while checking the signal quality at the time of reception.

Means for Solving the Problems

[0006] An optical communication system according to one aspect of the present disclosure includes a first optical communication device that outputs a third optical signal obtained by wavelength multiplexing a first optical signal having a first wavelength and a second optical signal having a second wavelength different from the first wavelength, a second optical communication device capable of amplifying the third optical signal input from the first optical communication device through an optical transmission line, an optical signal adjustment means capable of adjusting the intensity of each of the first and second optical signals wavelength multiplexed on the third optical signal in the second optical communication device, and a control device that controls the first optical communication device and the optical signal adjustment means. The first optical communication device includes a first intensity adjustment means for adjusting the intensity of the first optical signal, a second intensity adjustment means for adjusting the intensity of the second optical signal, a multiplexing means for outputting the third optical signal obtained by wavelength multiplexing the first optical signal and the second optical signal to the optical transmission line, and a first intensity monitoring means for monitoring a first intensity that is the intensity of the first optical signal input to the multiplexing means and a second intensity that is the intensity of the second optical signal input to the multiplexing means. The second optical communication device includes a second intensity monitoring means for monitoring a third intensity that is the intensity of the first optical signal wavelength multiplexed on the third optical signal in the second optical communication device and a fourth intensity that is the intensity of the second optical signal. The control device can perform a span loss adjustment process of adjusting the span loss of the first optical signal by controlling the optical signal adjustment means based on the first intensity and the third intensity, and adjusting the span loss of the second optical signal by controlling the optical signal adjustment means based on the second intensity and the fourth intensity, and an intensity difference adjustment process of adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical communication device by controlling at least one of the first and second intensity adjustment means. After the output of the third optical signal from the first optical communication device starts, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation, and after the end of the initial setting operation, a monitoring operation of repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed.

[0007] An optical signal control method according to one aspect of the present disclosure includes a first optical communication device that outputs a third optical signal obtained by wavelength multiplexing a first optical signal having a first wavelength and a second optical signal having a second wavelength different from the first wavelength, a second optical communication device that can amplify the third optical signal input from the first optical communication device through an optical transmission line, and an optical signal adjustment means capable of adjusting the intensity of each of the first and second optical signals wavelength multiplexed on the third optical signal in the second optical communication device. The first optical communication device includes a first intensity adjustment means for adjusting the intensity of the first optical signal, a second intensity adjustment means for adjusting the intensity of the second optical signal, a multiplexing means for outputting the third optical signal obtained by wavelength multiplexing the first optical signal and the second optical signal to the optical transmission line, and a first intensity monitoring means for monitoring a first intensity that is the intensity of the first optical signal input to the multiplexing means and a second intensity that is the intensity of the second optical signal input to the multiplexing means. The second optical communication device includes a second intensity monitoring means for monitoring a third intensity that is the intensity of the first optical signal wavelength multiplexed on the third optical signal in the second optical communication device and a fourth intensity that is the intensity of the second optical signal. In an optical communication system, by controlling the optical signal adjustment means based on the first intensity and the third intensity, the span loss of the first optical signal is adjusted, and by controlling the optical signal adjustment means based on the second intensity and the fourth intensity, a span loss adjustment process for adjusting the span loss of the second optical signal is performed. By controlling at least one of the first and second intensity adjustment means, an intensity difference adjustment process for adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical communication device is performed. After the output of the third optical signal from the first optical communication device starts, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation, and after the end of the initial setting operation, a monitoring operation for repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed.

[0008] An optical communication device according to one aspect of the present disclosure includes: a first optical input means capable of amplifying a first wavelength-division multiplexed optical signal obtained by wavelength-division multiplexing a first optical signal having a first wavelength and a second optical signal having a second wavelength different from the first wavelength, the first optical signal and the second optical signal being input from a second optical output means through a first optical transmission path; a wavelength separation means for wavelength-separating the first wavelength-division multiplexed optical signal into the first optical signal and the second optical signal; and a first optical output means for outputting a second wavelength-division multiplexed optical signal obtained by wavelength-division multiplexing the first optical signal and the second optical signal wavelength-separated by the wavelength separation means to a second optical input means through a second optical transmission path. A first optical signal adjustment means is capable of adjusting the intensity of each of the first and second optical signals wavelength-multiplexed in the first wavelength-division multiplexed optical signal within the first optical input means. A second optical signal adjustment means is capable of adjusting the intensity of each of the first and second optical signals wavelength-multiplexed in the second wavelength-division multiplexed optical signal within the second optical input means. A control device controls the first and second optical output means and the first and second optical signal adjustment means. The first and second optical output means include: a first intensity adjustment means for adjusting the intensity of the first optical signal; a second intensity adjustment means for adjusting the intensity of the second optical signal; a multiplexing means for outputting a wavelength-division multiplexed optical signal obtained by wavelength-division multiplexing the first optical signal and the second optical signal; and a first intensity monitoring means for monitoring a first intensity which is the intensity of the first optical signal input to the multiplexing means and a second intensity which is the intensity of the second optical signal input to the multiplexing means. The first and second optical input means each include a second intensity monitoring means for monitoring a third intensity which is the intensity of the first optical signal wavelength-multiplexed in the input wavelength-division multiplexed optical signal and a fourth intensity which is the intensity of the second optical signal within the respective means. The control device controls the first optical signal adjustment means based on the first intensity and the third intensity to adjust the span loss of the first optical signal and controls the first optical signal adjustment means based on the second intensity and the fourth intensity to adjust the span loss of the second optical signal in a span loss adjustment process, and controls at least one of the first and second intensity adjustment means to,It is possible to perform an intensity difference adjustment process for adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the first optical input means. After the output of the first wavelength-division multiplexed optical signal starts from the first optical output means, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation. After the end of the initial setting operation, a monitoring operation of repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed. Further, the control device controls the second optical signal adjustment means based on the first intensity and the third intensity between the second optical output means and the second optical input means, thereby adjusting the span loss of the first optical signal, and controls the second optical signal adjustment means based on the second intensity and the fourth intensity to adjust the span loss of the second optical signal. A span loss adjustment process is performed, and an intensity difference adjustment process for adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical input means is performed by controlling at least one of the first and second intensity adjustment means. It is possible to perform the above. After the output of the second wavelength-division multiplexed optical signal starts from the second optical output means, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation. After the end of the initial setting operation, a monitoring operation of repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed.

Advantages of the Invention

[0009] According to the present disclosure, it is possible to automatically and efficiently adjust the span loss of the optical signals of each wavelength of the wavelength-division multiplexed optical signal and the intensity difference between the optical signals.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same reference numerals are assigned to the same elements, and redundant explanations are omitted as necessary.

[0012] When referring to an embodiment hereinafter, it is applicable to any one of the embodiments described hereinafter, or a combination of two or more embodiments, and it also means that the application is not limited to a specific embodiment.

[0013] Embodiment 1 An optical communication system according to Embodiment 1 will be described. FIG. 1 is a block diagram schematically showing the basic configuration of an optical communication system according to an embodiment. The optical communication system 100 in FIG. 1 includes an optical communication device 10 and 20, and a control device 30. Hereinafter, the optical communication devices 10 and 20 are also referred to as the first and second optical communication devices, respectively.

[0014] The optical communication device 10 is an upstream optical communication device and adjusts the intensity of the input optical signal. Then, the optical communication device 10 outputs the intensity-adjusted optical signal to the optical transmission line 110. The optical communication device 10 is arranged, for example, on the optical output side of an optical transmitter and an optical repeater.

[0015] The optical communication device 10 includes optical intensity adjusters 11 and 12, an intensity monitor 13, and an optical signal output unit 14. The optical intensity adjuster 11 adjusts the intensity of the optical signal S1 with wavelength λ1 input to the optical intensity adjuster 11 according to the control signal C11 given from the control device 30. Then, the optical intensity adjuster 11 outputs the optical signal S1 after the intensity adjustment. The optical intensity adjuster 12 adjusts the intensity of the optical signal S2 with wavelength λ2 input to the optical intensity adjuster 12 according to the control signal C12 given from the control device 30. Then, the optical intensity adjuster 12 outputs the optical signal S2 after the intensity adjustment. Hereinafter, the wavelengths λ1 and λ2 are also referred to as the first and second wavelengths, respectively. The optical signals S1 and S2 are also referred to as the first and second optical signals, respectively. The optical intensity adjusters 11 and 12 are also referred to as the first and second optical intensity adjusters, respectively.

[0016] Hereinafter, the wavelength λ1 and the wavelength λ2 are different wavelengths. Note that the wavelength here indicates the band of the optical signal. Therefore, in optical communication applying the WDM technology, the channels of the optical signals S1 and S2 are different channels. In the present embodiment, it is assumed that the wavelength λ1 is a wavelength in the L band and the wavelength λ2 is a wavelength in the C band.

[0017] The intensity monitor 13 monitors the intensity P1 of the optical signal S1 output from the optical intensity adjuster 11. The intensity monitor 13 monitors the intensity P2 of the optical signal S2 output from the optical intensity adjuster 12. The intensity monitor 13 notifies the control device 30 of the respective intensities P1 and P2 of the optical signals S1 and S2. Hereinafter, the intensity monitor 13 is also referred to as the first intensity monitor. The intensities P1 and P2 are also referred to as the first and second intensities, respectively.

[0018] The optical signal output unit 14 outputs a wavelength-division multiplexed optical signal S obtained by wavelength-division multiplexing the optical signal S1 and the optical signal S2 to the optical transmission line 110. Hereinafter, for simplicity, the wavelength-division multiplexed optical signal is denoted as a WDM optical signal. Further, the optical signal output unit 14 can adjust the intensity of the wavelength-division multiplexed optical signal S by adjusting the attenuation amount of the wavelength-division multiplexed optical signal S. Hereinafter, the wavelength-division multiplexed optical signal S is also referred to as the third optical signal.

[0019] FIG. 2 is a diagram showing a configuration example of an optical signal output unit according to an embodiment. In this example, the optical signal output unit 14 includes a WDM coupler 14A and an optical attenuator 14B. The WDM coupler 14A outputs a WDM optical signal S obtained by wavelength-division multiplexing the optical signal S1 from the optical intensity adjustment unit 11 and the optical signal S2 from the optical intensity adjustment unit 12 to the optical attenuator 14B. The optical attenuator 14B adjusts the WDM optical signal S according to a control signal C14 given from the control device 30. Then, the optical attenuator 14B outputs the attenuated WDM optical signal S to the optical transmission line 110.

[0020] The optical communication device 20 is a downstream optical communication device that amplifies the optical signal from the optical transmission line 110 as necessary. Then, the optical communication device 20 outputs the amplified optical signal. The optical communication device 10 is arranged, for example, on the optical input side of an optical receiver and an optical repeater. Further, the optical communication device 20 outputs the monitoring result of the intensity of the received optical signal to the control device 30.

[0021] The optical communication device 20 includes an optical amplification unit 21 and an intensity monitoring unit 22. The optical amplification unit 21 may be configured as amplification means for amplifying the optical signals S1 and S2 by Raman scattered light in the optical transmission line 110, for example, according to a control signal C21 given from the control device 30. FIG. 3 is a diagram showing a configuration example of the optical amplification unit according to an embodiment. In this example, the optical amplification unit 21 includes light sources 21A and 21B, and optical couplers 21C and 21D. The light sources 21A and 21B output lights E1 and E2 having intensities according to the control signal C21, respectively. The lights E1 and E2 are respectively coupled to the optical transmission line 110 by the optical couplers 21C and 21D and transmitted in a direction opposite to that of the WDM optical signal S. Thereby, the optical signal S1 wavelength-division multiplexed with the WDM optical signal S is amplified by the Raman scattered light of the light E1 in the optical transmission line 110. The optical signal S2 wavelength-division multiplexed with the WDM optical signal S is amplified by the Raman scattered light of the light E2 in the optical transmission line 110. The control device 30 can adjust the respective gains of the optical signals S1 and S2 by forward Raman amplification in the optical transmission line 110 by controlling the light sources 21A and 21B to adjust the output intensities of the lights E1 and E2.

[0022] The intensity monitoring unit 22 is configured to be able to monitor the respective intensities P3 and P4 of the optical signals S1 and S2 wavelength-division multiplexed in the WDM optical signal S output from the optical amplification unit 21. The intensity monitoring unit 22 notifies the control device 30 of the respective intensities P3 and P4 of the optical signals S1 and S2. Hereinafter, the intensity monitoring unit 22 is also referred to as the second intensity monitoring unit. The intensities P3 and P4 are also referred to as the third and fourth intensities, respectively.

[0023] The control device 30 controls the optical communication devices 10 and 20 by the control signals C11, C12, C14, and C21 according to the monitoring results of the intensities of the optical signals output from the optical communication devices 10 and 20. In this configuration, the optical signal output unit 14 and the optical amplification unit 21 constitute an optical signal adjustment unit 80 that adjusts the respective intensities of the optical signals S1 and S2. The control device 30 controls the optical signal adjustment unit 80 by the control signals C14 and C21.

[0024] In FIG. 1, the control device 30 is provided outside the optical communication devices 10 and 20, but the control device 30 may be provided inside the optical communication device 10 or the optical communication device 20. Further, the optical communication devices 10 and 20 may be integrated to form the control device 30.

[0025] In the optical communication system 100, the span loss of the optical signals S1 and S2 is adjusted by using the adjustment of the attenuation amount of the WDM optical signal S in the optical signal output unit 14 and the adjustment of the gain during the amplification of the optical signals S1 and S2 in the optical amplification unit 21. Hereinafter, the operation of adjusting the attenuation amount of the WDM optical signal S in the optical signal output unit 14 is referred to as attenuation amount adjustment. The operation of adjusting the gain during the amplification of the optical signals S1 and S2 in the optical amplification unit 21 is referred to as gain adjustment.

[0026] Next, the optical signal adjustment operation in the optical communication system 100 will be described. FIG. 4 is a flowchart of the optical signal adjustment operation in the optical communication system according to an embodiment. FIG. 5 is a state transition diagram in the optical signal adjustment operation in the optical communication system according to an embodiment.

[0027] As shown in FIG. 4, the optical communication system 100 adjusts the intensities of the optical signals S1 and S2 multiplexed on the WDM optical signal S received by the optical communication device 20 by repeating span loss adjustment and intensity difference adjustment.

[0028] After the start of the optical signal adjustment operation, the optical communication system 100 first performs the following initial operations in steps ST11 and ST12.

[0029] Step ST11 The control device 30 sets a reference time T1 for initial setting as a reference time T indicating the repetition period of span loss adjustment. Thereby, span loss adjustment and intensity difference adjustment as initial setting operations are performed. REF

[0030] Step ST12 The control device 30 instructs the optical signal output unit 14 to start outputting the WDM optical signal S. The control device 30 may control the optical signal output unit 14 so that, for example, the attenuation amount of the WDM optical signal S at the optical signal output unit 14 is maximized before the start of the optical signal adjustment operation, and the attenuation amount of the WDM optical signal S at the optical signal output unit 14 becomes a predetermined value after the start of the optical signal adjustment operation.

[0031] Also, for example, in addition to the control of the optical signal output unit 14, the output intensities of the optical signals S1 and S2 from the optical intensity adjustment units 11 and 12 are minimized before the start of the optical signal adjustment operation, and after the start of the optical signal adjustment operation, the optical communication devices 10 and 20 may be controlled so that the attenuation amount of the WDM optical signal S at the optical signal output unit 14 becomes a predetermined value.

[0032] Furthermore, for example, in addition to the control of the optical signal output unit 14, the start and stop of the output of the WDM optical signal S may be controlled by controlling a light shielding means for the WDM optical signal S provided separately or transmission means for the optical signals S1 and S2.

[0033] Next, in steps ST21 to ST28, the control device 30 adjusts the span loss of the optical signal between the optical communication device 10 and the optical communication device 20.

[0034] Step ST21 The intensity monitoring unit 13 measures the intensity P1 of the optical signal S1 and the intensity P2 of the optical signal S2 in the optical communication device 10. The intensity monitoring unit 13 notifies the control device 30 of the measured intensity P1 of the optical signal S1 and the intensity P2 of the optical signal S2. The intensity monitoring unit 22 measures the intensity P3 of the optical signal S1 and the intensity P4 of the optical signal S2 in the optical communication device 20. The intensity monitoring unit 22 notifies the control device 30 of the measured intensity P3 of the optical signal S1 and the intensity P4 of the optical signal S2.

[0035] Step ST22 The control device 30 determines whether the span loss L1 indicated by the difference P1 - P3 between the intensity P1 of the optical signal S1 on the upstream side and the intensity P3 of the optical signal S1 on the downstream side is greater than the reference value L TH1 If the span loss L1 is smaller than the reference value L TH1 the process proceeds to step ST26. Hereinafter, the span loss L1 is also referred to as the first span loss.

[0036] Step ST23 When the span loss L1 is greater than the reference value L TH1 the control device 30 determines whether the difference ΔL1 between the span loss L1 and the reference value L TH1 is a value that can be canceled when the attenuation amount at the optical signal output unit 14 is changed from the already set attenuation amount to the minimum attenuation amount or the maximum attenuation amount. Hereinafter, the determination process in step ST23 is also referred to as the first determination.

[0037] Step ST24 When the difference ΔL1 can be canceled by adjusting the attenuation amount of the optical signal output unit 14, the control device 30 adjusts the attenuation amount of the optical signal output unit 14 so that the difference ΔL1 becomes smaller. Here, the adjustment width ΔA of the attenuation amount when step ST24 is executed once is limited to the adjustment width upper limit value A MAX The adjustment width upper limit value A MAXBy setting it to an appropriate value, the coarseness and fineness of the attenuation amount adjustment can be controlled. Hereinafter, the span loss adjustment in step ST24 is also referred to as the first span loss adjustment. The adjustment width upper limit value A MAX is also referred to as the first attenuation amount adjustment width.

[0038] Step ST25 When the difference ΔL1 cannot be canceled by the attenuation amount adjustment of the optical signal output unit 14, the control device 30 adjusts the gain of the optical signal S1 of the optical amplifier unit 21 so that the difference ΔL1 becomes smaller. In this process, it is preferable that the attenuation amount in the optical signal output unit 14 is minimized. Here, the adjustment width ΔG1 of the gain adjusted when step ST23 is executed once is limited to the adjustment width upper limit value G1 MAX . The adjustment width upper limit value G1 MAX By setting it to an appropriate value, the coarseness and fineness of the gain adjustment can be controlled. Hereinafter, the span loss adjustment in step ST25 is also referred to as the second span loss adjustment. The gain of the optical signal S1 of the optical amplifier unit 21 is also referred to as the first gain. The adjustment width upper limit value G1 MAX is also referred to as the first gain adjustment width.

[0039] Step ST26 The control device 30 determines whether the span loss L2 indicated by the difference P2 - P4 between the intensity P2 of the optical signal S2 on the upstream side and the intensity P4 of the optical signal S1 on the downstream side is smaller than the reference value L TH2 . If the span loss L2 is smaller than the reference value L TH2 , the process proceeds to step ST31. Hereinafter, the span loss L2 is also referred to as the second span loss.

[0040] Step ST27 When the span loss L2 is the reference value L TH2If it is larger, the control device 30 performs span loss adjustment on the optical signal S2. At this time, attenuation amount adjustment may have been performed during the span loss adjustment of the optical signal S1. In this case, if the attenuation amount adjustment is performed again for the span loss adjustment of the optical signal S2, the span loss adjustment of the optical signal S1 will be reset. Therefore, for the optical signal S2, the span loss is adjusted only by gain adjustment. Accordingly, the control device 30 adjusts the gain of the optical signal S2 of the optical amplification unit 21 so that the difference ΔL2 between the span loss L2 and the reference value L TH2 becomes smaller. Here, the adjustment width ΔG2 of the gain to be adjusted when step ST27 is executed once is limited to the adjustment width upper limit value G2 MAX . By setting the adjustment width upper limit value G2 MAX to an appropriate value, the coarseness and fineness of the gain adjustment can be controlled. Hereinafter, the span loss adjustment in step ST27 is also referred to as the third span loss adjustment. The gain of the optical signal S2 of the optical amplification unit 21 is also referred to as the second gain. The adjustment width upper limit value G2 MAX is also referred to as the second gain adjustment width.

[0041] Step ST28 The control device 30 measures the elapsed time T after adjusting the gain of the optical signal S2 of the optical amplification unit 21. Then, the control device 30 monitors whether the elapsed time T has reached the reference time T REF . If the elapsed time T has reached the reference time T REF , the control device 30 returns the process to step ST21.

[0042] The span loss L2 is the reference value L TH2If it is smaller, the optical communication system 100 once completes span loss adjustment and shifts to intensity difference adjustment in steps ST31 to ST35. In steps ST21 to ST28, the span losses of the optical signals S1 and S2 are each converged to a value smaller than a predetermined value. However, in this state, it is assumed that losses become unbalanced due to the influence of SRS (Stimulated Raman Scattering) tilt or the like, and the intensity P3 of the optical signal S1 and the intensity P4 of the optical signal S2 on the downstream side are unbalanced. Therefore, the control device 30 performs intensity difference adjustment in the following steps ST31 to ST35 so that the difference between the intensity P3 of the optical signal S1 and the intensity P4 of the optical signal S2 becomes smaller than a predetermined value.

[0043] Step ST31 The intensity monitoring unit 22 measures the intensity P3 of the optical signal S1 and the intensity P4 of the optical signal S2 in the optical communication device 20. The intensity monitoring unit 22 notifies the control device 30 of the measured intensity P3 of the optical signal S1 and the intensity P4 of the optical signal S2.

[0044] Step ST32 The control device 30 determines whether the intensity difference ΔP between the intensity P3 of the optical signal S1 on the downstream side and the intensity P4 of the optical signal S2 is greater than the reference value ΔP TH or not. If the intensity difference ΔP is smaller than the reference value ΔP TH the process proceeds to step ST34.

[0045] Step ST33 If the intensity difference ΔP is greater than the reference value ΔP TH the control device 30 adjusts at least one of the intensity P1 of the optical signal S1 and the intensity P2 of the optical signal S2 in order to reduce the intensity difference ΔP.

[0046] Here, the case where the control device 30 controls both the optical intensity adjustment units 11 and 12 will be described. The control device 30 sets the intensity difference between the intensity P1 of the optical signal S1 on the upstream side and the intensity P2 of the optical signal S2 as the reference value ΔP THIn order to make it smaller, based on the intensity P3 of the downstream optical signal S1 and the intensity P4 of the optical signal S2, the intensity P1 of the upstream optical signal S1 and the intensity P2 of the optical signal S2 are determined. Then, the control device 30 instructs the determined intensities P1 and P2 to the optical intensity adjustment units 11 and 12.

[0047] The optical intensity adjustment unit 11 performs intensity adjustment so that the intensity P1 of the optical signal S1 becomes the indicated value. The optical intensity adjustment unit 12 performs intensity adjustment so that the intensity P2 of the optical signal S2 becomes the indicated value. Then, the process returns to step ST31.

[0048] Step ST34 When the intensity difference ΔP is smaller than the reference value ΔP TH the control device 30 determines whether the reference time T indicating the repetition period of the span loss adjustment is set as the initial setting reference time T1. When the reference time T2 for constant setting is set as the reference time T REF after a predetermined time has elapsed, the control device 30 returns the process to step ST21. Thereby, the constant monitoring of the optical signal is continued. REF When the initial setting reference time T1 is set as the reference time T

[0049] Step ST35 the reference time T REF the control device 30 changes the reference time T REF to the reference time T2 for constant monitoring. After a predetermined time has elapsed, the control device 30 returns the process to step ST21. Thereby, the state of the optical communication system 100 shifts from the initial setting to the constant monitoring. Thereafter, span loss adjustment and intensity difference adjustment as constant monitoring operations are performed.

[0050] As described above, according to the optical communication system 100, the initial setting operations of span loss adjustment and intensity difference adjustment of the optical signals S1 and S2 wavelength-division multiplexed on the WDM optical signal S can be automatically and efficiently performed without manual operation.

[0051] Also, according to the optical communication system 100, after the initial setting operation is completed, by intermittently performing span loss adjustment and intensity difference adjustment of the optical signals S1 and S2 in the constant monitoring operation, the intensity adjustment of the optical signals S1 and S2 can also be continuously performed. Thereby, the optical signals S1 and S2 during the operation of the optical communication system 100 can be automatically and efficiently maintained at a desired quality.

[0052] In the optical communication system 100, the reference time T indicating the repetition period of the span loss adjustment REF It is desirable that the reference time T1 for initial setting used as be shorter than the reference time T2 for constant monitoring. Thereby, by repeatedly performing the span loss adjustment at a short period during the initial setting, the value of the span loss can be quickly converged to a value smaller than the reference value. On the other hand, by performing the span loss adjustment at a long period corresponding to the change over time during the constant monitoring, the intensity fluctuation of the optical signal due to the change over time can be corrected.

[0053] In the optical communication system 100, the adjustment width upper limit value A of the adjustment width ΔA of the attenuation amount MAX The adjustment width upper limit value A for the initial setting operation used as MAX1 should be a value larger than the adjustment width upper limit value A MAX2 for the constant monitoring operation. Thereby, during the initial setting operation, rough adjustment can be performed to change the attenuation amount of the optical signal by a large width. Therefore, the number of repetitions of the span loss adjustment can be suppressed, and the initial setting of the span loss can be quickly completed. On the other hand, during the constant monitoring operation, fine adjustment can be performed to change the attenuation amount of the optical signal by a smaller width. Therefore, precise span loss adjustment can be performed for the change over time of the span loss, which is predicted to have a small fluctuation width.

[0054] Also, in the optical communication system 100, the adjustment width upper limit value G1 of the adjustment width ΔG1 of the gain of the optical signal S1 MAX The adjustment width upper limit value G1 for the initial setting operation used as MAX1 should be the adjustment width upper limit value G1 MAX2It is desirable to set it to a value larger than [value]. As a result, during the initial setting operation, coarse adjustment can be performed to change the gain of the optical signal S1 over a large range. Therefore, the number of repetitions of span loss adjustment can be suppressed, and the initial setting of span loss can be completed quickly. On the other hand, during the constant monitoring operation, fine adjustment can be performed to change the attenuation amount of the optical signal over a smaller range. Therefore, precise span loss adjustment can be performed for the change in span loss over time, which is predicted to have a small variation width.

[0055] Furthermore, in the optical communication system 100, the upper limit value G2 of the adjustment width ΔG2 of the gain of the optical signal S2 MAX used as the upper limit value G2 of the adjustment width for the initial setting operation MAX1 is desirably set to a value larger than the upper limit value G2 of the adjustment width for the constant monitoring operation MAX2 . As a result, during the initial setting operation, coarse adjustment can be performed to change the gain of the optical signal S2 over a large range. Therefore, the number of repetitions of span loss adjustment can be suppressed, and the initial setting of span loss can be completed quickly. On the other hand, during the constant monitoring operation, fine adjustment can be performed to change the attenuation amount of the optical signal over a smaller range. Therefore, precise span loss adjustment can be performed for the change in span loss over time, which is predicted to have a small variation width.

[0056] Embodiment 2 In this embodiment, a case will be described in which, in an optical communication system, the optical communication device 10 and the optical communication device 20 according to Embodiment 1 function as one relay device.

[0057] FIG. 6 is a block diagram schematically showing the configuration of an optical communication system according to an embodiment. The optical communication system 200 includes an upstream node device 40, a downstream node device 50, an optical communication device 60, and a control device 70.

[0058] The upstream node device 40 may be various optical communication devices such as an optical repeater, an optical transmitter, and an optical transceiver that are inserted into an optical communication network and function as node devices. The upstream node device 40 has at least an output device 41 having the same configuration as the optical communication device 10 according to Embodiment 1. The output device 41 transmits the WDM optical signal S to the optical communication device 60 through the optical transmission path 210.

[0059] The optical communication device 60 is configured as a repeater that relays the WDM optical signal S transmitted from the upstream node device 40. The optical communication device 60 has at least an input device having the same configuration as the optical communication device 20 according to Embodiment 1 and an output device having the same configuration as the optical communication device 10. After performing predetermined processing on the input WDM optical signal S, the optical communication device 60 transmits it to the downstream node device 50 through the optical transmission path 220.

[0060] FIG. 7 is a block diagram schematically showing the configuration of an optical communication device according to an embodiment. The optical communication device 60 has an input device 61, an output device 62, and a wavelength separation unit 63. The input device 61 has the same configuration as the optical communication device 20. The input device 61 performs the same processing as the optical communication device 20 on the input WDM optical signal S. Then, the processed WDM optical signal S is output to the wavelength separation unit 63 through the optical transmission path 64.

[0061] The wavelength separation unit 63 wavelength-separates the WDM optical signal S into an optical signal S1 with wavelength λ1 and an optical signal S2 with wavelength λ2. Then, the wavelength separation unit 63 outputs the optical signals S1 and S2 to the output device 62.

[0062] The output device 62 has the same configuration as the optical communication device 10. The input device 61 performs the same processing as the optical communication device 20 on the input optical signals S1 and S2. Then, the output device 62 transmits the WDM optical signal S to the downstream node device 50 through the optical transmission path 220.

[0063] The downstream node device 50 may be various optical communication devices such as an optical repeater, an optical receiver, and an optical transceiver that are inserted into an optical communication network and function as node devices. The downstream node device 50 has at least an input device 51 having the same configuration as the optical communication device 20 according to the first embodiment. The input device 51 receives the WDM optical signal S from the optical communication device 60 through the optical transmission line 220.

[0064] In the optical communication system 200, the output device 41 of the upstream node device 40 and the input device 61 of the optical communication device 60 are paired, and similar to the optical communication devices 10 and 20, they can perform an optical signal adjustment operation. Also, the output device 62 of the optical communication device 60 and the input device 51 of the downstream node device 50 are paired, and similar to the optical communication devices 10 and 20, they can perform an optical signal adjustment operation. Needless to say, these optical signal adjustment operations can be realized by the control device 70 giving control signals to the upstream node device 40, the downstream node device 50, and the optical communication device 60 in the same manner as the control device 30.

[0065] In FIG. 6, the control device 70 is provided outside the upstream node device 40 and the downstream node device 50, but the control device 70 may be provided inside the upstream node device 40 or the downstream node device 50. Also, the upstream node device 40 and the downstream node device 50 may be integrated to form the control device 70.

[0066] As described above, it can be understood that according to the optical communication device 60, even in the relay of optical signals, it can cooperate with the upstream node device 40 and the downstream node device 50 to perform an optical signal adjustment operation similar to that in the first embodiment.

[0067] Other Embodiments Although the present disclosure has been described with reference to the embodiments above, the present disclosure is not limited to the above-described embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. And each embodiment can be combined with other embodiments as appropriate.

[0068] The configuration of the optical signal output unit is merely an example. As long as it is possible to output the wavelength-division multiplexed optical signal S obtained by wavelength-division multiplexing the optical signals S1 and S2, and to adjust the attenuation amount of the wavelength-division multiplexed optical signal S, various configurations may be used.

[0069] The configuration of the intensity monitoring unit 22 is merely an example. As long as each of the optical signals S1 and S2 can be amplified, various configurations may be used.

[0070] In the above-described embodiment, the wavelength λ1 is a wavelength in the C band and the wavelength λ2 is a wavelength in the L band, but this is merely an example. As long as the wavelength λ1 is shorter than the wavelength λ2, the wavelengths λ1 and λ2 may be arbitrary wavelengths.

[0071] In the above-described embodiment, regarding the case where the value of interest is equal to the reference value in the comparison between the value of interest and the reference value, it may be included in the case where the value of interest is greater than the reference value, or it may be included in the case where the value of interest is smaller than the reference value.

[0072] Each drawing is merely an illustration for explaining one or more embodiments. Each drawing is not associated with only one specific embodiment, but may be associated with one or more other embodiments. As those skilled in the art can understand, various features or steps described with reference to any one drawing can be combined with the features or steps shown in one or more other drawings to create, for example, embodiments that are not explicitly illustrated or described. Not all of the features or steps shown in any one drawing for explaining exemplary embodiments are necessarily essential, and some features or steps may be omitted. The order of the steps described in any drawing may be changed as appropriate.

[0073] Some or all of the above-described embodiments may be described as follows in the following supplementary notes, but are not limited thereto.

[0074] (Appendix 1) A first optical communication device that outputs a third optical signal obtained by wavelength-division multiplexing a first optical signal of a first wavelength and a second optical signal of a second wavelength different from the first wavelength; a second optical communication device that can amplify the third optical signal input from the first optical communication device through an optical transmission line; an optical signal adjustment means capable of adjusting the intensity of each of the first and second optical signals wavelength-division multiplexed on the third optical signal in the second optical communication device; and a control device that controls the first optical communication device and the optical signal adjustment means. The first optical communication device includes a first intensity adjustment means for adjusting the intensity of the first optical signal, a second intensity adjustment means for adjusting the intensity of the second optical signal, a multiplexing means for outputting the third optical signal obtained by wavelength-division multiplexing the first optical signal and the second optical signal to the optical transmission line, and a first intensity monitoring means for monitoring a first intensity that is the intensity of the first optical signal input to the multiplexing means and a second intensity that is the intensity of the second optical signal input to the multiplexing means. The second optical communication device includes a second intensity monitoring means for monitoring a third intensity that is the intensity of the first optical signal wavelength-division multiplexed on the third optical signal in the second optical communication device and a fourth intensity that is the intensity of the second optical signal. The control device can perform a span loss adjustment process of adjusting the span loss of the first optical signal by controlling the optical signal adjustment means based on the first intensity and the third intensity, and adjusting the span loss of the second optical signal by controlling the optical signal adjustment means based on the second intensity and the fourth intensity, and an intensity difference adjustment process of adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical communication device by controlling at least one of the first and second intensity adjustment means. After the output of the third optical signal from the first optical communication device is started, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation, and after the end of the initial setting operation, a monitoring operation of repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed. An optical communication system.

[0075] (Appendix 2) The multiplexing means attenuates the input third optical signal and outputs the attenuated third optical signal. The second optical communication device further includes an optical amplification means capable of amplifying each of the first and second optical signals wavelength-division multiplexed with the third optical signal. The second intensity monitoring means monitors the intensities of the first and second optical signals wavelength-division multiplexed with the third optical signal output from the optical amplification means as the third and fourth intensities, respectively. The optical signal adjustment means is composed of the multiplexing means and the optical amplification means. The control device performs the span loss adjustment process by adjusting the attenuation amount of the third optical signal in the multiplexing means and the first gain of the first optical signal and the second gain of the second optical signal by the optical amplification means. The optical communication system according to Appendix 1.

[0076] (Appendix 3) The control device performs a first determination to determine whether the first span loss of the first optical signal can be adjusted by the attenuation amount of the multiplexing means. When the first span loss of the first optical signal can be adjusted by the attenuation amount of the multiplexing means, a first span loss adjustment for adjusting the first span loss by adjusting the attenuation amount of the multiplexing means. When the first span loss cannot be adjusted by the attenuation amount of the multiplexing means, a second span loss adjustment for adjusting the first span loss by adjusting the first gain in the optical amplification means. The optical communication system according to Appendix 2.

[0077] (Appendix 4) The adjustment range of the attenuation amount of the multiplexing means is limited to a first attenuation amount adjustment range, and the adjustment range of the first gain is limited to a first gain adjustment range. The control device repeats the first determination and either one of the first and second span loss adjustments until the first span loss becomes smaller than a predetermined value. The optical communication system according to Appendix 3.

[0078] (Appendix 5) The control device performs a third span loss adjustment for adjusting the second span loss of the second optical signal by adjusting the second gain in the optical amplification means. The optical communication system according to Appendix 4.

[0079] (Supplementary Note 6) The adjustment range of the second gain is limited to the second gain adjustment range, and the control device repeats the third span loss adjustment until the second span loss becomes smaller than a predetermined value. The optical communication system according to Supplementary Note 5.

[0080] (Supplementary Note 7) The repetition period of the first to third span loss adjustments in the initial setting operation is shorter than the repetition period of the first to third span loss adjustments in the monitoring operation. The optical communication system according to Supplementary Note 6.

[0081] (Supplementary Note 8) The adjustment range of the first attenuation amount in the initial setting operation is larger than the adjustment range of the first attenuation amount in the monitoring operation, the adjustment range of the first gain in the initial setting operation is larger than the adjustment range of the first gain in the monitoring operation, and the adjustment range of the second gain in the initial setting operation is larger than the adjustment range of the second gain in the monitoring operation. The optical communication system according to Supplementary Note 6 or 7.

[0082] (Supplementary Note 9) A first optical communication device that outputs a third optical signal obtained by wavelength-division multiplexing a first optical signal of a first wavelength and a second optical signal of a second wavelength different from the first wavelength; a second optical communication device capable of amplifying the third optical signal input from the first optical communication device through an optical transmission line; and optical signal adjustment means capable of adjusting the intensity of each of the first and second optical signals wavelength-division multiplexed on the third optical signal in the second optical communication device. The first optical communication device includes first intensity adjustment means for adjusting the intensity of the first optical signal, second intensity adjustment means for adjusting the intensity of the second optical signal, multiplexing means for outputting the third optical signal obtained by wavelength-division multiplexing the first optical signal and the second optical signal to the optical transmission line, and first intensity monitoring means for monitoring a first intensity that is the intensity of the first optical signal input to the multiplexing means and a second intensity that is the intensity of the second optical signal input to the multiplexing means. The second optical communication device includes second intensity monitoring means for monitoring a third intensity that is the intensity of the first optical signal wavelength-division multiplexed on the third optical signal in the second optical communication device and a fourth intensity that is the intensity of the second optical signal. In an optical communication system, by controlling the optical signal adjustment means based on the first intensity and the third intensity, the span loss of the first optical signal is adjusted, and by controlling the optical signal adjustment means based on the second intensity and the fourth intensity, a span loss adjustment process for adjusting the span loss of the second optical signal is performed, and by controlling at least one of the first and second intensity adjustment means, an intensity difference adjustment process for adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical communication device is performed. After the output of the third optical signal from the first optical communication device starts, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation, and after the end of the initial setting operation, a monitoring operation for repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed. An optical signal control method.

[0083] (Supplementary Note 10) A first optical input means capable of amplifying a first wavelength-division multiplexed optical signal obtained by wavelength-division multiplexing a first optical signal having a first wavelength and a second optical signal having a second wavelength different from the first wavelength, which are input from the second optical output means through the first optical transmission path; a wavelength separation means for wavelength-separating the first wavelength-division multiplexed optical signal into the first optical signal and the second optical signal; and a first optical output means for outputting a second wavelength-division multiplexed optical signal obtained by wavelength-division multiplexing the first optical signal and the second optical signal, which are wavelength-separated by the wavelength separation means, to the second optical input means through the second optical transmission path. The first optical signal adjustment means can adjust the intensity of each of the first and second optical signals wavelength-multiplexed in the first wavelength-division multiplexed optical signal within the first optical input means. The second optical signal adjustment means can adjust the intensity of each of the first and second optical signals wavelength-multiplexed in the second wavelength-division multiplexed optical signal within the second optical input means. The control device controls the first and second optical output means and the first and second optical signal adjustment means. The first and second optical output means include a first intensity adjustment means for adjusting the intensity of the first optical signal, a second intensity adjustment means for adjusting the intensity of the second optical signal, a multiplexing means for outputting a wavelength-division multiplexed optical signal obtained by wavelength-division multiplexing the first optical signal and the second optical signal, and a first intensity monitoring means for monitoring a first intensity which is the intensity of the first optical signal input to the multiplexing means and a second intensity which is the intensity of the second optical signal input to the multiplexing means. The first and second optical input means each include a second intensity monitoring means for monitoring a third intensity which is the intensity of the first optical signal wavelength-multiplexed in the input wavelength-division multiplexed optical signal and a fourth intensity which is the intensity of the second optical signal within the respective internal parts. The control device controls the first optical signal adjustment means based on the first intensity and the third intensity between the first optical output means and the first optical input means to adjust the span loss of the first optical signal, and controls the first optical signal adjustment means based on the second intensity and the fourth intensity to adjust the span loss of the second optical signal, which is a span loss adjustment process, and controls at least one of the first and second intensity adjustment means to adjust the intensity difference between the first optical signal and the second optical signal after span loss adjustment within the first optical input means, which is an intensity difference adjustment process.It is possible to perform the following operations. After the output of the first wavelength-division multiplexed optical signal starts from the first optical output means, the span loss adjustment process and the intensity difference adjustment process are performed as initial setting operations. After the completion of the initial setting operations, a monitoring operation is performed in which the span loss adjustment process and the intensity difference adjustment process are repeated at a predetermined cycle. Further, the control device controls the second optical signal adjustment means between the second optical output means and the second optical input means based on the first intensity and the third intensity to adjust the span loss of the first optical signal, and controls the second optical signal adjustment means based on the second intensity and the fourth intensity to adjust the span loss of the second optical signal. This is a span loss adjustment process. By controlling at least one of the first and second intensity adjustment means, an intensity difference adjustment process is performed to adjust the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical input means. It is possible to perform these operations. After the output of the second wavelength-division multiplexed optical signal starts from the second optical output means, the span loss adjustment process and the intensity difference adjustment process are performed as initial setting operations. After the completion of the initial setting operations, a monitoring operation is performed in which the span loss adjustment process and the intensity difference adjustment process are repeated at a predetermined cycle. An optical communication device.

Explanation of Reference Numerals

[0084] 10, 20, 60 Optical communication device 11, 12 Optical intensity adjustment unit 12 Optical intensity adjustment unit 13, 21 Intensity monitoring unit 14 Optical signal output unit 22 Optical amplifier 21A, 21B Light source 21C, 21D Optical coupler 30, 70 Control device 40 Upstream node device 41, 62 Output device 50 Downstream node device 51, 61 Input device 63 Wavelength separation unit 80 Optical signal adjustment unit 100, 200 Optical communication system 110, 210, and 220 optical transmission paths E1 and E2 light S1 and S2 optical signals SWDM optical signal

Claims

1. A first optical communication device that outputs a third optical signal obtained by wavelength-division multiplexing a first optical signal having a first wavelength and a second optical signal having a second wavelength different from the first wavelength; A second optical communication device capable of amplifying the third optical signal input from the first optical communication device through an optical transmission line; Optical signal adjustment means capable of adjusting the intensity of each of the first and second optical signals wavelength-division multiplexed on the third optical signal in the second optical communication device; A control device for controlling the first optical communication device and the optical signal adjustment means, comprising: The first optical communication device includes: First intensity adjustment means for adjusting the intensity of the first optical signal; Second intensity adjustment means for adjusting the intensity of the second optical signal; Multiplexing means for outputting the third optical signal obtained by wavelength-division multiplexing the first optical signal and the second optical signal to the optical transmission line; First intensity monitoring means for monitoring a first intensity that is the intensity of the first optical signal input to the multiplexing means and a second intensity that is the intensity of the second optical signal input to the multiplexing means; The second optical communication device includes second intensity monitoring means for monitoring a third intensity that is the intensity of the first optical signal wavelength-division multiplexed on the third optical signal in the second optical communication device and a fourth intensity that is the intensity of the second optical signal; The control device is configured to: Adjust the span loss of the first optical signal by controlling the optical signal adjustment means based on the first intensity and the third intensity, and adjust the span loss of the second optical signal by controlling the optical signal adjustment means based on the second intensity and the fourth intensity. A span loss adjustment process; By controlling at least one of the first and second intensity adjustment means, an intensity difference adjustment process for adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical communication device can be performed. It is possible to perform, After the output of the third optical signal from the first optical communication device is started, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation, After the end of the initial setting operation, a monitoring operation for repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed. An optical communication system.

2. The multiplexing means attenuates the input third optical signal and outputs the attenuated third optical signal. The second optical communication device further includes an optical amplification means capable of amplifying each of the first and second optical signals wavelength-division multiplexed with the third optical signal. The second intensity monitoring means monitors the intensities of the first and second optical signals wavelength-division multiplexed with the third optical signal output from the optical amplification means as the third and fourth intensities, respectively. The optical signal adjustment means is composed of the multiplexing means and the optical amplification means. The control device performs the span loss adjustment process by adjusting the attenuation amount of the third optical signal in the multiplexing means, the first gain of the first optical signal, and the second gain of the second optical signal by the optical amplification means. The optical communication system according to claim 1.

3. The control device performs a first determination to determine whether the first span loss of the first optical signal can be adjusted by the attenuation amount of the multiplexing means, when the first span loss of the first optical signal can be adjusted by the attenuation amount of the multiplexing means, performs a first span loss adjustment to adjust the first span loss by adjusting the attenuation amount of the multiplexing means, when the first span loss cannot be adjusted by the attenuation amount of the multiplexing means, performs a second span loss adjustment to adjust the first span loss by adjusting the first gain in the optical amplification means. The optical communication system according to claim 2.

4. The adjustment range of the attenuation amount of the multiplexing means is limited to a first attenuation amount adjustment range. The adjustment range of the first gain is limited to a first gain adjustment range. The control device repeats the first determination and either one of the first and second span loss adjustments until the first span loss becomes smaller than a predetermined value. The optical communication system according to claim 3.

5. The control device performs a third span loss adjustment to adjust the second span loss of the second optical signal by adjusting the second gain in the optical amplification means. The optical communication system according to claim 4.

6. The adjustment range of the second gain is limited to a second gain adjustment range. The control device repeats the third span loss adjustment until the second span loss becomes smaller than a predetermined value. The optical communication system according to claim 5.

7. The repetition period of the first to third span loss adjustments in the initial setting operation is shorter than the repetition period of the first to third span loss adjustments in the monitoring operation. The optical communication system according to claim 6.

8. The first attenuation amount adjustment range in the initial setting operation is larger than the first attenuation amount adjustment range in the monitoring operation. The first gain adjustment range in the initial setting operation is larger than the first gain adjustment range in the monitoring operation. The second gain adjustment range in the initial setting operation is larger than the second gain adjustment range in the monitoring operation. The optical communication system according to claim 6 or 7.

9. A first optical communication device that outputs a third optical signal obtained by wavelength multiplexing a first optical signal of a first wavelength and a second optical signal of a second wavelength different from the first wavelength. A second optical communication device capable of amplifying the third optical signal input from the first optical communication device through an optical transmission line. Optical signal adjustment means capable of adjusting the intensity of each of the first and second optical signals wavelength-multiplexed on the third optical signal in the second optical communication device. The first optical communication device First intensity adjustment means for adjusting the intensity of the first optical signal. Second intensity adjustment means for adjusting the intensity of the second optical signal. Multiplexing means for outputting the third optical signal obtained by wavelength multiplexing the first optical signal and the second optical signal to the optical transmission line. First intensity monitoring means for monitoring a first intensity that is the intensity of the first optical signal input to the multiplexing means and a second intensity that is the intensity of the second optical signal input to the multiplexing means. In the optical communication system, the second optical communication device includes second intensity monitoring means for monitoring a third intensity that is the intensity of the first optical signal wavelength-multiplexed on the third optical signal in the second optical communication device and a fourth intensity that is the intensity of the second optical signal. A span loss adjustment process of adjusting the span loss of the first optical signal by controlling the optical signal adjustment means based on the first intensity and the third intensity, and adjusting the span loss of the second optical signal by controlling the optical signal adjustment means based on the second intensity and the fourth intensity. An intensity difference adjustment process of adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical communication device by controlling at least one of the first and second intensity adjustment means. After the output of the third optical signal from the first optical communication device is started, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation. After the completion of the initial setting operation, a monitoring operation is performed to repeat the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle. Optical signal control method.

10. A first optical input means capable of amplifying a first wavelength multiplexed optical signal obtained by wavelength multiplexing a first optical signal of a first wavelength input from a second optical output means through a first optical transmission path and a second optical signal of a second wavelength different from the first wavelength; Wavelength separation means for wavelength-separating the first wavelength multiplexed optical signal into the first optical signal and the second optical signal; A first optical output means for outputting a second wavelength multiplexed optical signal obtained by wavelength multiplexing the first optical signal and the second optical signal wavelength-separated by the wavelength separation means to a second optical input means through a second optical transmission path; The first optical signal adjusting means is capable of adjusting the intensity of each of the first and second optical signals wavelength-multiplexed in the first wavelength multiplexed optical signal within the first optical input means; The second optical signal adjusting means is capable of adjusting the intensity of each of the first and second optical signals wavelength-multiplexed in the second wavelength multiplexed optical signal within the second optical input means; The control device controls the first and second optical output means and the first and second optical signal adjusting means; The first and second optical output means are: A first intensity adjusting means for adjusting the intensity of the first optical signal; A second intensity adjusting means for adjusting the intensity of the second optical signal; Combining means for outputting a wavelength multiplexed optical signal obtained by wavelength multiplexing the first optical signal and the second optical signal; First intensity monitoring means for monitoring a first intensity which is the intensity of the first optical signal input to the combining means and a second intensity which is the intensity of the second optical signal input to the combining means; The first and second optical input means are: Second intensity monitoring means for monitoring, inside each of them, a third intensity which is the intensity of the first optical signal wavelength-multiplexed in the input wavelength multiplexed optical signal and a fourth intensity which is the intensity of the second optical signal; The control device is: Between the first optical output means and the first optical input means, A span loss adjustment process for adjusting the span loss of the first optical signal by controlling the first optical signal adjusting means based on the first intensity and the third intensity, and adjusting the span loss of the second optical signal by controlling the first optical signal adjusting means based on the second intensity and the fourth intensity; By controlling at least one of the first and second intensity adjustment means, an intensity difference adjustment process for adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the first optical input means can be performed. After the output of the first wavelength multiplexed optical signal starts from the first optical output means, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation. After the end of the initial setting operation, a monitoring operation for repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed. Furthermore, the control device between the second optical output means and the second optical input means By controlling the second optical signal adjustment means based on the first intensity and the third intensity, the span loss of the first optical signal is adjusted, and by controlling the second optical signal adjustment means based on the second intensity and the fourth intensity, a span loss adjustment process for adjusting the span loss of the second optical signal. By controlling at least one of the first and second intensity adjustment means, an intensity difference adjustment process for adjusting the intensity difference between the first optical signal and the second optical signal after span loss adjustment in the second optical input means can be performed. After the output of the second wavelength multiplexed optical signal starts from the second optical output means, the span loss adjustment process and the intensity difference adjustment process are performed as an initial setting operation. After the end of the initial setting operation, a monitoring operation for repeating the span loss adjustment process and the intensity difference adjustment process at a predetermined cycle is performed. Optical communication device.

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