Optical amplification relay device, optical amplification relay system, and optical amplification relay method

Abstract

This optical amplification relay device is provided with: a demultiplexing unit that demultiplexes an optical signal including a signal in a first band and a signal in a second band into the signal in the first band and the signal in the second band; a power spectral density adjustment unit that increases the power spectral density of the signal in the second band resulting from the demultiplication by the demultiplexing unit; and a multiplexing unit that multiplexes the signal in the second band having the power spectral density increased by the power spectral density adjustment unit with the signal in the first band.

Description

Optical amplification relay device, optical amplification relay system, and optical amplification relay method

[0001] The present invention relates to an optical amplification relay device, an optical amplification relay system, and an optical amplification relay method.

[0002] To realize social transformation through innovations in information and communication technology, the optical network that forms its foundation requires continuous capacity increases. One of the key technologies for increasing the capacity of optical networks is wavelength resource expansion. Wavelength resource expansion achieves increased capacity in optical networks by expanding the bandwidth of wavelength division multiplexing (WDM) signals. If transmitting and receiving equipment and optical amplification and relay equipment can be implemented in the new bandwidth, it is possible to increase the capacity of the optical network without laying new fibers, which would incur high installation costs.

[0003] Non-patent documents 1 to 4 describe optical communication systems that transmit optical signals from a transmitting device to a receiving device using one or more bandwidths.

[0004] Figure 18 illustrates the bandwidths that have been used in conventional optical communication systems, or that are being considered for use in optical communication systems. As shown in Figure 18, conventional optical communication systems use the C-band W2, which has a wavelength of 1530 nm to 1565 nm, and the L-band W3, which has a wavelength of 1565 nm to 1625 nm. In addition, the S-band W1, which has a wavelength of 1460 nm to 1530 nm, and the S-band W4, which has a wavelength of 1625 nm to 1675 nm, are being considered for use as new bandwidths.

[0005] Non-Patent Document 1 describes an optical communication system that transmits optical signals from a transmitting device to a receiving device using C-band wavelengths. Non-Patent Document 2 describes an optical communication system that transmits optical signals from a transmitting device to a receiving device using C-band and L-band wavelengths. Non-Patent Document 3 describes an optical communication system that transmits optical signals from a transmitting device to a receiving device using S-band, C-band, and L-band wavelengths. Non-Patent Document 4 describes an optical communication system that uses a ROADM (Reconfigurable Optical Add-Drop Multiplexer), a multiplexer that can add and delete optical signals transmitted from the transmitting device to the receiving device.

[0006] T. Kobayashi et al., "35-Tb / s C-Band Transmission Over 800 km Employing 1-Tb / s PS-64QAM Signals Enhanced by Complex 8 × 2 MIMO Equalizer," 2019 Optical Fiber Communications Conference and Exhibition (OFC), San Diego, CA, USA, 2019, pp. 1-3.K. Kimura, S. Shimizu, T. Kobayashi, M. Nakamura and Y. Miyamoto, "Accurate SNR Estimation in C+L-band 10-THz Hybrid Raman-EDFA Amplified Transmission Using Two-Stage Power Profile Calculation Accounting for Pump Depletion," 2024 Optical Fiber Communications Conference and Exhibition (OFC), San Diego, CA, USA, 2024, pp. 1-3.X. Zhao, S. Escobar-Landero, D. Le Gac, A. Lorences-Riesgo, T. Viret-Denaix, Q. Guo, L. Gan, S. Li, S. Cao, X. Xiao, N. E. Dahdah, A. Gallet, S. Yu, H. Hafermann, L. Godard, R. Brenot, Y. Frignac, and G. Charlet, "2005 Tb / s Transmission with S+C+L Amplification Covering 150 nm Bandwidth over 2×100 km PSCF Spans," in European Conference on Optical Communication (ECOC) 2022, J. Leuthold, C. Harder, B. Offrein, and H. Limberger, eds., Technical Digest Series (Optica Publishing Group, 2022), paper Th3C.4.B. Collings, "New devices enabling software-defined optical networks," in IEEE Communications Magazine, vol. 51, no. 3, pp. 66-71, March 2013, doi: 10.1109 / MCOM.2013.6476867.

[0007] In Non-Patent Document 3, in addition to the conventionally used C-band and L-band, the S-band is newly used. However, it is difficult to satisfy the desired transmission power (input power to the optical fiber transmission line) for the newly added S-band. The desired transmission power is not simply the total power, but the transmission power spectral density (that is, the power per unit bandwidth), that is, how much power can be realized as the power per channel of the WDM signal is important. It is difficult to satisfy the desired transmission power because for the newly added short wavelength band S-band, the desired transmission power becomes larger compared to the conventionally used C-band and L-band, and the maximum transmission power spectral density achievable in the newly added S-band is lower than that in the conventionally used C-bands such as the C-band and L-band.

[0008] However, due to the limitation of the saturation output power of the optical amplifier (in the case of erbium-doped fiber optical amplifiers and optical parametric optical amplifiers) or the output power limitation due to signal distortion caused by non-linear optical effects (in the case of concentrated Raman optical amplifiers), it may not be possible to satisfy the desired transmission power spectral density. Such problems also occur for long wavelength bands above the U-band that also require the development of new optical amplifiers. In addition, the short wavelength bands defined as the S-band and the E-band with wavelengths of 1360 nm to 1460 nm are wider than the conventionally used C-band and L-band, and a higher total output power is required to realize the desired transmission power.

[0009] The desired transmission power is generally determined by the balance between spontaneous emission optical noise generated in an optical amplifier and signal distortion due to the nonlinear optical effect of an optical fiber. If the transmission power is too low, the influence of spontaneous emission optical noise increases. On the other hand, if the transmission power is too high, the influence of signal distortion due to the nonlinear optical effect increases. That is, in either case, the signal quality deteriorates and the amount of information that can be transmitted is limited. Therefore, the desired transmission power is set so that the balance between spontaneous emission optical noise and signal distortion due to the nonlinear optical effect is good and the best signal quality can be obtained. The cause of increasing the desired transmission power during wavelength resource expansion is stimulated Raman scattering that occurs in an optical fiber transmission line. Stimulated Raman scattering occurs more efficiently as the signal band widens, causing a transition of signal power from a short wavelength to a long wavelength. Therefore, for the newly added short wavelength band, a greater power attenuation occurs than in the case of only simple optical fiber loss, and the influence of spontaneous emission optical noise increases. As a result, the desired transmission power at which the balance between spontaneous emission optical noise and signal distortion due to the nonlinear optical effect is good increases compared to the band conventionally used.

[0010] The limitation on the transmission power spectral density in the new short wavelength band is caused by the bandwidth and the maximum output power of the optical amplifier. For example, the entire S band has the same bandwidth as the total of the C band and the L band. Also, although the optical amplifier in the C band or the L band can have a saturation output power of 23 dBm, the saturation output power of a commercially available thulium-doped fiber optical amplifier applicable to the S band is 19 to 20 dBm.

[0011] An object of the present invention is to provide a technique capable of preventing the power spectral density of a new band from decreasing even when optical communication is performed using a new band in addition to a predetermined band.

[0012] One aspect of the present invention is an optical amplification relay device comprising: a demultiplexing unit that demultiplexes an optical signal including a signal of a first band and a signal of a second band into the signal of the first band and the signal of the second band; a power spectral density adjustment unit that increases the power spectral density of the signal of the second band demultiplexed by the demultiplexing unit; and a multiplier unit that combines the signal of the second band, whose power spectral density has been increased by the power spectral density adjustment unit, with the signal of the first band.

[0013] Another aspect of the present invention is an optical amplification relay method which involves demultiplexing an optical signal including a signal in a first band and a signal in a second band into the signal in the first band and the signal in the second band, increasing the power spectral density of the demultiplexed signal in the second band, and combining the signal in the second band with the signal in the first band.

[0014] The present invention makes it possible to prevent a decrease in the power spectral density of the new bandwidth, even when optical communication is performed using a new bandwidth in addition to a predetermined bandwidth.

[0015] This is a first schematic diagram illustrating the outline of the present invention. This is a modified version of the first schematic diagram illustrating the outline of the present invention. This is a second schematic diagram illustrating the outline of the present invention. This is a modified version of the second schematic diagram illustrating the outline of the present invention. This is a third schematic diagram illustrating the outline of the present invention. This is a schematic configuration diagram of an optical amplification relay device according to the first embodiment of the present invention. This is a first modified version of the optical amplification relay device according to the first embodiment of the present invention. This is a second modified version of the optical amplification relay device according to the first embodiment of the present invention. This is a schematic configuration diagram of an optical amplification relay device according to the second embodiment of the present invention. This is a modified version of the optical amplification relay device according to the second embodiment of the present invention. This is a schematic configuration diagram of an optical amplification relay device according to the third embodiment of the present invention. This is a first modified version of the optical amplification relay device according to the third embodiment of the present invention. This is a second modified version of the optical amplification relay device according to the third embodiment of the present invention. This is a schematic configuration diagram of an optical amplification relay device according to the fourth embodiment of the present invention. This is a modified version of the optical amplification relay device according to the fourth embodiment of the present invention. This is a diagram illustrating an optical amplification relay system according to the fifth embodiment of the present invention. This is a diagram illustrating an optical amplification relay system according to the sixth embodiment of the present invention. This is a diagram illustrating bandwidths that have been conventionally used in optical communication systems, or bandwidths that are being considered for use in optical communication systems.

[0016] Hereinafter, several aspects of the present invention will be described with reference to the drawings.

[0017] Figure 1 is a first schematic diagram illustrating the outline of the present invention. Figure 1 shows the configuration of an optical amplification unit according to an example of the present invention. The optical amplification unit shown in Figure 1 comprises an optical demultiplexer 50A, optical amplifiers 60A and 61A, and an optical multiplexer 70A. The optical demultiplexer 50A receives an S-band optical signal as shown in Figure 1(a), with a wavelength of 1460 nm to 1530 nm and a power spectral density of P ｉｎAn optical signal of dBm / Hz is input. The optical demultiplexer 50A divides the input optical signal at the center wavelength of the S band. That is, the optical demultiplexer 50A demultiplexes the input optical signal into a signal with a wavelength of 1460 nm to 1495 nm and a signal with a wavelength of 1495 nm to 1530 nm, outputs the signal with a wavelength of 1460 nm to 1495 nm to the optical amplifier 60A, and outputs the signal with a wavelength of 1495 nm to 1530 nm to the optical amplifier 61A.

[0018] The optical amplifier 60A amplifies the power spectral density P of the signal with a wavelength of 1460 nm to 1495 nm input from the optical demultiplexer 50A by 3 dB, and outputs the signal with the power spectral density P ｉｎ dBm / Hz as the signal shown in Fig. 1(b) to the optical multiplexer 70A. Also, the optical amplifier 61A amplifies the power spectral density P of the signal with a wavelength of 1495 nm to 1530 nm input from the optical demultiplexer 50A by 3 dB, and the power spectral density P ｏｕｔ dBm / Hz as the signal shown in Fig. 1(c) to the optical multiplexer 70A. The optical multiplexer 70A combines the signal with a wavelength of 1460 nm to 1495 nm and a power spectral density P ｉｎ dBm / Hz input from the optical amplifier 60A and the signal with a wavelength of 1495 nm to 1530 nm and a power spectral density P ｏｕｔ dBm / Hz input from the optical amplifier 61A, and generates and outputs a signal with a wavelength of 1460 nm to 1530 nm and a power spectral density P ｏｕｔ dBm / Hz as shown in Fig. 1(d). ｏｕｔ According to the optical amplification unit shown in Fig. 1, since the signal band is halved for the same saturation output power, the outputs of the optical amplifiers 60A and 61A are P ｏｕｔ dBm / Hz.

[0019] ｏｕｔA power spectral density of dBm / Hz + 3dB is obtained. After optical amplification, the entire bandwidth is combined using the optical multiplexer 70A, resulting in a transmission power 3dB stronger than conventional methods. However, in reality, the increase in power spectral density will be less than 3dB due to the insertion losses of the optical demultiplexer 50A and the optical multiplexer 70A. Also, the noise figure of the optical amplifier will degrade by the amount of the insertion loss of the optical demultiplexer 50A placed before it.

[0020] Note that the configuration of the optical amplification unit shown in Figure 1 may be changed to the configuration shown in Figure 2. For parts of the optical amplification unit shown in Figure 2 that have the same configuration as the optical amplification unit shown in Figure 1, the explanation of those configurations will be omitted. The optical amplification unit shown in Figure 2 differs from the optical amplification unit shown in Figure 1 in that it further includes an optical amplifier 20A. The optical amplifier 20A has a wavelength of 1460 nm to 1530 nm as shown in Figure 2(a), and a power spectral density of P ｉｎ The dBm / Hz optical signal is amplified by a predetermined amount and output to the optical demultiplexer 50A. The processing from the optical amplifier 20A onward is the same as that of the optical amplification section shown in Figure 1, so the explanation of that processing is omitted.

[0021] The optical amplification unit shown in Figure 2 reduces the effect of the noise figure degradation due to the insertion loss of the optical demultiplexer 50A in the optical amplification unit shown in Figure 1 by optically amplifying the entire bandwidth once before dividing the bandwidth. The optical amplification unit shown in Figure 2 is P ｉｎ This is effective when the dBm / Hz is low and the degradation of the noise figure has a significant impact on system performance.

[0022] Figure 3 is a second schematic diagram illustrating the outline of the present invention. Figure 3 shows the configuration of an optical amplification unit according to another example of the present invention. The optical amplification unit shown in Figure 3 comprises an optical demultiplexer 50B, optical amplifiers 60B and 61B, and an optical multiplexer 70B. The optical demultiplexer 50B receives an S-band optical signal as shown in Figure 3(a), with a wavelength of 1460 nm to 1530 nm and a power spectral density of P ｉｎAn optical signal in dBm / Hz is input. The optical demultiplexer 50B splits the input optical signal at wavelengths other than the center of the S-band. For example, the optical demultiplexer 50B splits the input optical signal into a signal with wavelengths of 1460 nm to 1485 nm and a signal with wavelengths of 1485 nm to 1530 nm, outputs the signal with wavelengths of 1460 nm to 1485 nm to the optical amplifier 60B, and outputs the signal with wavelengths of 1485 nm to 1530 nm to the optical amplifier 61B.

[0023] The optical amplifier 60B measures the power spectral density P of the signal with a wavelength of 1460 nm to 1485 nm input from the optical demultiplexer 50B. ｉｎ The dBm / Hz signal is amplified by 3 dB, and the power spectral density is P ｏｕｔ As a signal larger than dBm / Hz, the signal shown in Figure 3(b) is output to the optical multiplexer 70B. The optical amplifier 61B also outputs the power spectral density P of the signal with wavelengths from 1485 nm to 1530 nm input from the optical demultiplexer 50B. ｉｎ The dBm / Hz signal is amplified by 3 dB, and the power spectral density is P ｏｕｔ As a signal smaller than dBm / Hz, the signal shown in Figure 3(c) is output to the optical multiplexer 70B. The optical multiplexer 70B receives input from the optical amplifier 60B with a wavelength of 1460 nm to 1485 nm and a power spectral density of P ｏｕｔ A signal larger than dBm / Hz, with a wavelength of 1485 nm to 1530 nm input from optical amplifier 61B, and a power spectral density of P ｏｕｔ By combining it with a signal smaller than dBm / Hz, a signal with a wavelength of 1460 nm to 1530 nm, as shown in Figure 3(d), is generated and output.

[0024] The optical amplification unit shown in Figure 3 differs from the optical amplification unit shown in Figure 1 in that the center of the band division is shifted to the shorter wavelength side. According to the optical amplification unit shown in Figure 3, the power spectral density on the short wavelength side, where the signal bandwidth input to the optical amplifier 60B is narrow, is P ｏｕｔ It becomes larger than dBm / Hz, and the long wavelength band is P ｏｕｔThe value becomes smaller than dBm / Hz. By shifting the center wavelength of the division in this way, it is possible to set wavelength bands with strong and weak power spectral density. The optical amplification section shown in Figure 3 is suitable for use when the wavelength dependence of the desired transmission power is large within the bandwidth. For example, since the desired transmission power increases with shorter wavelengths due to stimulated Raman scattering, it is suitable for use when the effect of stimulated Raman scattering is large.

[0025] Note that the configuration of the optical amplification unit shown in Figure 3 may be changed to the configuration shown in Figure 4. For parts of the optical amplification unit shown in Figure 4 that have the same configuration as the optical amplification unit shown in Figure 3, the explanation of those configurations will be omitted. The optical amplification unit shown in Figure 4 differs from the optical amplification unit shown in Figure 3 in that it further includes an optical amplifier 20B. The optical amplifier 20B has a wavelength of 1460 nm to 1530 nm as shown in Figure 4(a), and a power spectral density of P ｉｎ The dBm / Hz optical signal is optically amplified by a predetermined amount and output to the optical demultiplexer 50B. The processing from the optical amplifier 20B onward is the same as that of the optical amplification section shown in Figure 3, so the explanation of that processing is omitted.

[0026] The optical amplification unit shown in Figure 4 reduces the effect of the noise figure degradation due to the insertion loss of the optical demultiplexer 50B of the optical amplification unit shown in Figure 3 by optically amplifying the entire bandwidth once before dividing the bandwidth. The optical amplification unit shown in Figure 4 is P ｉｎ This is effective when the dBm / Hz is low and the degradation of the noise figure has a significant impact on system performance.

[0027] Figure 5 is a third schematic diagram illustrating the outline of the present invention. In the explanation of Figures 1 to 4, the case in which the S band from 1460 nm to 1530 nm is divided into two was described, but the power spectral density of the S band signal may be increased by a method as described in Figure 5. For example, an optical amplifier may be used that converts an optical signal with a wavelength of 1460 nm to 1530 nm and a predetermined power spectral density, as shown in Figure 5(a), into an optical signal with a wavelength of 1470 nm to 1520 nm and a power spectral density greater than the predetermined value, as shown in Figure 5(b). In Figure 5, the usable bandwidth of the S band is reduced from 1460 nm to 1530 nm to 1470 nm to 1520 nm, but the power used in the S band remains the same. Thus, the area of ​​the portion showing the signal in the graph of Figure 5(a) and the area of ​​the portion showing the signal in the graph of Figure 5(b) are the same.

[0028] Since the new short-wavelength band (e.g., the S-band) has a wide bandwidth, the configuration shown in Figure 5 is effective when it is not necessary to use the entire bandwidth. The configurations described in Figure 1 or 2, Figure 3 or 4, and Figure 5 may be used individually, or they may be used in combination.

[0029] [First Embodiment] Next, an optical amplification relay device according to the first embodiment of the present invention will be described. Figure 6 is a schematic configuration diagram of the optical amplification relay device 100C according to the first embodiment of the present invention. The optical amplification relay device 100C includes an optical demultiplexer 10C, an optical demultiplexer 50C, optical amplifiers 60C, 61C, 62C, 63C, an optical multiplexer 70C, and an optical multiplexer 80C.

[0030] The optical demultiplexer 10C demultiplexes the optical signal input to the optical amplifier relay device 100C, which includes S-band, C-band, and L-band signals, into S-band, C-band, and L-band signals. It then outputs the demultiplexed S-band signal to the optical demultiplexer 50C, the demultiplexed C-band signal to the optical amplifier 62C, and the demultiplexed L-band signal to the optical amplifier 63C.

[0031] The optical demultiplexer 50C demultiplexes the S-band signal from 1460 nm to 1530 nm input from the optical demultiplexer 10C into a signal from 1460 nm to 1495 nm and a signal from 1495 nm to 1530 nm. The demultiplexed 1460 nm to 1495 nm signal is output to the optical amplifier 60C, and the demultiplexed 1495 nm to 1530 nm signal is output to the optical amplifier 61C.

[0032] The optical amplifier 60C amplifies the 1460 nm to 1495 nm signal input from the optical demultiplexer 50C by a predetermined amount (for example, 3 dB) and outputs it to the optical multiplexer 70C. The optical amplifier 61C also amplifies the 1495 nm to 1530 nm signal input from the optical demultiplexer 50C by a predetermined amount (for example, 3 dB) and outputs it to the optical multiplexer 70C.

[0033] The optical multiplexer 70C combines the 1460nm to 1495nm signal input from the optical amplifier 60C with the 1495nm to 1530nm signal input from the optical amplifier 61C and outputs it to the optical multiplexer 80C.

[0034] The optical amplifier 62C amplifies the C-band signal input from the optical demultiplexer 10C by a predetermined amount (for example, 3 dB) and outputs it to the optical multiplexer 80C. The optical amplifier 63C amplifies the L-band signal input from the optical demultiplexer 10C by a predetermined amount (for example, 3 dB) and outputs it to the optical multiplexer 80C.

[0035] The optical multiplexer 80C combines the S-band signal input from the optical multiplexer 70C, the C-band signal input from the optical amplifier 62C, and the L-band signal input from the optical amplifier 63C, and outputs the combined signal to the outside of the optical amplification relay device 100C.

[0036] As described above, in the optical amplification relay device 100C according to the first embodiment, the optical demultiplexer 10C (also referred to as the demultiplexer) demultiplexes an optical signal including signals in the C-band and L-band (also referred to as the first band) and the S-band (also referred to as the second band) into signals in the C-band and L-band and signals in the S-band. Furthermore, the optical demultiplexer 50C, optical amplifiers 60C and 61C, and optical multiplexer 70C (also referred to as the power spectral density adjustment unit) increase the power spectral density of the S-band signal demultiplexed by the optical demultiplexer 10C. Furthermore, the optical multiplexer 80C (also referred to as the multiplexer) combines the S-band signal, whose power spectral density has been increased by the optical demultiplexer 50C, optical amplifiers 60C and 61C, and optical multiplexer 70C, with the signals in the C-band and L-band.

[0037] In the optical amplification relay device 100C according to the first embodiment, the optical amplifier 60C optically amplifies the short-wavelength signal of the S-band, which has been split into two signals by the optical demultiplexer 50C, and the optical amplifier 61C optically amplifies the long-wavelength signal of the S-band, thereby increasing the power spectral density of the S-band. In other words, even when optical communication is performed using a new band (e.g., the S-band) in addition to predetermined bands (e.g., the C-band and L-band), it is possible to prevent the power spectral density of the new band from decreasing. Therefore, by increasing the maximum value of the transmission power spectral density for the S-band, a new band where it is difficult to satisfy the desired transmission power, in addition to the conventionally used C-band and L-band, it is possible to contribute to increased capacity through the expansion of wavelength resources.

[0038] Note that the configuration of the optical amplification relay device 100C shown in Figure 6 may be changed to the configuration shown in Figure 7. For parts of the optical amplification relay device 100C shown in Figure 7 that have the same configuration as the optical amplification relay device 100C shown in Figure 6, the explanation of those configurations will be omitted. The optical amplification relay device 100C shown in Figure 7 differs from the optical amplification relay device 100C shown in Figure 6 in that it further includes an optical amplifier 20C. The optical amplifier 20C performs optical amplification by a predetermined amount for S-band optical signals with wavelengths of 1460 nm to 1530 nm and outputs it to the optical demultiplexer 50C. Since the processing after the optical amplifier 20C is the same as the processing of the optical amplification relay device 100C shown in Figure 6, the explanation of that processing will be omitted.

[0039] The optical amplification relay device 100C shown in Figure 7 can reduce the effect of the noise figure degradation due to the insertion loss of the optical demultiplexer 50C of the optical amplification relay device 100C shown in Figure 6 by optically amplifying the S-band signal once before dividing the S-band signal.

[0040] Note that the configuration of the optical amplification relay device 100C shown in Figure 6 may be changed to the configuration shown in Figure 8. For parts of the optical amplification relay device 100C shown in Figure 8 that have the same configuration as the optical amplification relay device 100C shown in Figure 6, the explanation of those configurations will be omitted. The optical amplification relay device 100C shown in Figure 8 differs from the optical amplification relay device 100C shown in Figure 6 in that it does not include an optical demultiplexer 50C and an optical multiplexer 70C. In the optical amplification relay device 100C shown in Figure 8, the optical demultiplexer 10C processes the optical signal input to the optical amplification relay device 100C, which includes signals in the S band, C band, and L band, into S Ｓ Belt, S Ｌ The signal is separated into the S band, C band, and L band, and the separated S band Ｓ The band signal is output to the optical amplifier 60C, and the desequenced S Ｌ The signal in the band is output to optical amplifier 61C, the decoupled C-band signal is output to optical amplifier 62C, and the decoupled L-band signal is output to optical amplifier 63C. Ｓ The band is, for example, the bandwidth from 1460 nm to 1495 nm. Also, S Ｌ The band is, for example, the range from 1495 nm to 1530 nm.

[0041] Furthermore, in the optical amplification relay device 100C shown in Figure 8, the optical multiplexer 80C receives S amplified by the optical amplifier 60C. Ｓ The signal in the band and the S amplified by the optical amplifier 61C Ｌ The band signal, the C-band signal amplified by optical amplifier 62C, and the L-band signal amplified by optical amplifier 63C are combined and output to the outside of the optical amplification relay device 100C.

[0042] In the optical amplification relay device 100C shown in Figure 8, the optical demultiplexer 50C and the optical multiplexer 70C can be omitted compared to the optical amplification relay device 100C shown in Figure 6, thus simplifying the configuration of the device.

[0043] [Second Embodiment] Next, an optical amplification relay device according to a second embodiment of the present invention will be described. Figure 9 is a schematic configuration diagram of an optical amplification relay device 100D according to a second embodiment of the present invention. The optical amplification relay device 100D includes an optical demultiplexer 10D, optical amplifiers 20D, 21D, 22D, wavelength selective switches (WSS) 30D, 31D, 32D, 40D, 41D, 42D, an optical demultiplexer 50D, optical amplifiers 60D, 61D, 62D, 63D, an optical multiplexer 70D, and an optical multiplexer 80D.

[0044] The optical demultiplexer 10D demultiplexes the optical signal input to the optical amplification relay device 100D, which includes S-band, C-band, and L-band signals, into S-band, C-band, and L-band signals. The demultiplexed S-band signal is output to the optical amplifier 20D, the demultiplexed C-band signal is output to the optical amplifier 21D, and the demultiplexed L-band signal is output to the optical amplifier 22D.

[0045] Optical amplifier 20D amplifies the S-band signal input from optical demultiplexer 10D by a predetermined amount (for example, 3 dB) and outputs it to wavelength-selective switch 30D. Optical amplifier 21D amplifies the C-band signal input from optical demultiplexer 10D by a predetermined amount (for example, 3 dB) and outputs it to wavelength-selective switch 31D. Optical amplifier 22D amplifies the L-band signal input from optical demultiplexer 10D by a predetermined amount (for example, 3 dB) and outputs it to wavelength-selective switch 32D.

[0046] Wavelength-selective switch 30D inserts an S-band signal into the S-band signal input from optical amplifier 20D as needed and outputs it to wavelength-selective switch 40D. Wavelength-selective switch 31D inserts a C-band signal into the C-band signal input from optical amplifier 21D as needed and outputs it to wavelength-selective switch 41D. Wavelength-selective switch 32D inserts an L-band signal into the L-band signal input from optical amplifier 22D as needed and outputs it to wavelength-selective switch 42D.

[0047] Wavelength-selective switch 40D outputs the remaining S-band signal to optical demultiplexer 50D after branching the S-band signal from the S-band signal input from wavelength-selective switch 30D as needed. Wavelength-selective switch 41D outputs the remaining C-band signal to optical amplifier 62D after branching the C-band signal from the C-band signal input from wavelength-selective switch 31D as needed. Wavelength-selective switch 42D outputs the remaining L-band signal to optical amplifier 63D after branching the L-band signal from the L-band signal input from wavelength-selective switch 32D as needed.

[0048] The optical demultiplexer 50D converts the S-band signal from 1460 nm to 1530 nm input from the wavelength-selective switch 40D into an S-band signal from 1460 nm to 1495 nm. Ｓ The band signal and S from 1495 nm to 1530 nm Ｌ The signal is split into two, and the split S Ｓ The band signal is output to the optical amplifier 60D, and the S band is desequently converted. Ｌ The signal from the band is output to the optical amplifier 61D.

[0049] The optical amplifier 60D receives S from the optical demultiplexer 50D. Ｓ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 70D. The optical amplifier 61D receives the S from the optical demultiplexer 50D. Ｌ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 70D. The optical multiplexer 70D receives the S from the optical amplifier 60D. Ｓ The signal in the band and the S input from the optical amplifier 61D Ｌ The signal from the band is combined with the signal and output to the optical multiplexer 80D.

[0050] The optical amplifier 62D amplifies the C-band signal input from the wavelength-selective switch 41D by a predetermined amount (for example, 3 dB) and outputs it to the optical multiplexer 80D. The optical amplifier 63D amplifies the L-band signal input from the wavelength-selective switch 42D by a predetermined amount (for example, 3 dB) and outputs it to the optical multiplexer 80C. The optical multiplexer 80D combines the S-band signal input from the optical multiplexer 70D, the C-band signal input from the optical amplifier 62D, and the L-band signal input from the optical amplifier 63D, and outputs it to the outside of the optical amplification relay device 100D.

[0051] In the optical amplification relay device 10D of the second embodiment, the wavelength-selective switches 30D, 31D, 32D, 40D, 41D, and 42D constitute a ROADM (Reconfigurable Optical Add-Drop Multiplexer). By providing the wavelength-selective switches 30D, 31D, 32D, 40D, 41D, and 42D, it becomes possible to insert, split, or equalize optical signals in any bandwidth. Therefore, the insertion loss of the wavelength-selective switches 30D, 31D, and 32D is compensated by the optical amplifiers 60D, 61D, 62D, and 63D provided downstream of the wavelength-selective switches 30D, 31D, and 32D, and a WDM signal is output.

[0052] The optical amplification relay device 10D of the second embodiment provides the same effects as the optical amplification relay device 10C of the first embodiment. Furthermore, compared to the optical amplification relay device 10C of the first embodiment, the optical amplification relay device 10D of the second embodiment further includes wavelength-selective switches 30D, 31D, 32D, 40D, 41D, and 42D (also referred to as optical insertion branching multiplexers) that add or delete optical signals for signals in the C-band and L-band, and signals in the S-band.

[0053] In the optical amplification relay device 10D of the second embodiment, after processing by wavelength-selective switches 30D and 40D, S is performed by the optical demultiplexer 50D. Ｓ Obi and S Ｌ By splitting the signal into different frequency bands and amplifying it optically using optical amplifiers 60D and 61D, the power spectral density of the S-band can be increased.

[0054] Note that the configuration of the optical amplification relay device 100D shown in Figure 9 may be changed to the configuration shown in Figure 10. For parts of the optical amplification relay device 100D shown in Figure 10 that have the same configuration as the optical amplification relay device 100D shown in Figure 9, the explanation of those configurations will be omitted. The optical amplification relay device 100D shown in Figure 10 differs from the optical amplification relay device 100D shown in Figure 9 in that it does not include an optical multiplexer 70D.

[0055] In the optical amplification relay device 100D shown in Figure 10, the optical amplifier 60D receives S from the optical demultiplexer 50D. Ｓ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 80D. The optical amplifier 61D receives the S from the optical demultiplexer 50D. Ｌ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 80D.

[0056] The optical multiplexer 80D receives S from the optical amplifier 60D. Ｓ The signal in the band and the S input from the optical amplifier 61D Ｌ The band signal, the C-band signal input from optical amplifier 62D, and the L-band signal input from optical amplifier 63D are combined and output to the outside of the optical amplification relay device 100D.

[0057] In the optical amplification relay device 100D shown in Figure 10, the optical multiplexer 70D can be omitted compared to the optical amplification relay device 100D shown in Figure 9, thus simplifying the configuration of the device.

[0058] [Third Embodiment] Next, an optical amplification relay device according to a third embodiment of the present invention will be described. Figure 11 is a schematic configuration diagram of the optical amplification relay device 100E according to the third embodiment of the present invention. The optical amplification relay device 100E includes an optical demultiplexer 10E, an optical demultiplexer 50E, optical amplifiers 60E, 61E, 62E, 63E, 64E, an optical multiplexer 70E, and an optical multiplexer 80E.

[0059] The optical demultiplexer 10E demultiplexes the optical signal input to the optical amplifier relay device 100E, which includes signals in the S band, C band, L band, and U band, into S band, C band, and L band signals. It then outputs the demultiplexed S band signal to the optical demultiplexer 50E, the demultiplexed C band signal to the optical amplifier 62E, the demultiplexed L band signal to the optical amplifier 63E, and the demultiplexed U band signal to the optical amplifier 64E.

[0060] The optical demultiplexer 50E receives the S-band signal from optical demultiplexer 10C in the range of 1460 nm to 1530 nm and converts it to the S-band signal in the range of 1460 nm to 1495 nm. Ｓ The band signal and S from 1495 nm to 1530 nm Ｌ The signal is split into two, and the split S Ｓ The band signal is output to the optical amplifier 60E, and the S band is desequently converted. Ｌ The signal from the band is output to the optical amplifier 61E.

[0061] The optical amplifier 60E receives S from the optical demultiplexer 50E. Ｓ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 70E. The optical amplifier 61E receives the S from the optical demultiplexer 50C. Ｌ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 70E. The optical multiplexer 70E receives the S from the optical amplifier 60E. Ｓ The signal in the band and the S input from the optical amplifier 61E Ｌ The signal from the band is combined with the signal and output to the optical multiplexer 80E.

[0062] Optical amplifier 62E amplifies the C-band signal input from optical demultiplexer 10E by a predetermined amount (for example, 3 dB) and outputs it to optical multiplexer 80E. Optical amplifier 63E amplifies the L-band signal input from optical demultiplexer 10E by a predetermined amount (for example, 3 dB) and outputs it to optical multiplexer 80E. Optical amplifier 64E amplifies the U-band signal input from optical demultiplexer 10E by a predetermined amount (for example, 3 dB) and outputs it to optical multiplexer 80E.

[0063] The optical multiplexer 80E combines the S-band signal input from the optical multiplexer 70E, the C-band signal input from the optical amplifier 62E, the L-band signal input from the optical amplifier 63E, and the U-band signal input from the optical amplifier 64E, and outputs the combined signal to the outside of the optical amplification relay device 100E.

[0064] As described above, in the optical amplification relay device 100E according to the third embodiment, the optical demultiplexer 10E (also referred to as the demultiplexer) demultiplexes an optical signal including signals in the C-band, L-band, and U-band (also referred to as the first band) and the S-band (also referred to as the second band) into signals in the C-band, L-band, and U-band and signals in the S-band. Furthermore, the optical demultiplexer 50E, optical amplifiers 60E, 61E, and optical multiplexer 70E (also referred to as the power spectral density adjustment unit) increase the power spectral density of the S-band signal demultiplexed by the optical demultiplexer 10E. Furthermore, the optical multiplexer 80E (also referred to as the multiplexer) combines the S-band signal, whose power spectral density has been increased by the optical demultiplexer 50E, optical amplifiers 60E, 61E, and optical multiplexer 70E, with the signals in the C-band, L-band, and U-band.

[0065] In the optical amplification relay device 100E according to the third embodiment, the optical amplifier 60E optically amplifies the short-wavelength signal of the S-band, which has been split into two signals by the optical demultiplexer 50E, while the optical amplifier 61E optically amplifies the long-wavelength signal of the S-band, thereby increasing the power spectral density of the S-band. In other words, even when optical communication is performed using a new band (e.g., the S-band) in addition to predetermined bands (e.g., the C-band, L-band, and U-band), it is possible to prevent the power spectral density of the new band from decreasing. Therefore, by increasing the maximum value of the transmission power spectral density for the S-band, a new band where it is difficult to satisfy the desired transmission power, in addition to the conventionally used C-band and L-band, it is possible to contribute to increased capacity through the expansion of wavelength resources.

[0066] Note that the configuration of the optical amplification relay device 100E shown in Figure 11 may be changed to the configuration shown in Figure 12. For parts of the optical amplification relay device 100E shown in Figure 12 that have the same configuration as the optical amplification relay device 100E shown in Figure 11, the explanation of those configurations will be omitted. The optical amplification relay device 100E shown in Figure 12 differs from the optical amplification relay device 100E shown in Figure 11 in that it further includes an optical amplifier 20E. The optical amplifier 20E performs optical amplification by a predetermined amount for S-band optical signals with wavelengths of 1460 nm to 1530 nm and outputs it to the optical demultiplexer 50E. Since the processing after the optical amplifier 20E is the same as the processing of the optical amplification relay device 100E shown in Figure 11, the explanation of that processing will be omitted.

[0067] The optical amplification relay device 100E shown in Figure 12 can reduce the effect of the noise figure degradation due to the insertion loss of the optical demultiplexer 50E of the optical amplification relay device 100E shown in Figure 11 by optically amplifying the S-band signal once before dividing the S-band signal.

[0068] Note that the configuration of the optical amplification relay device 100E shown in Figure 11 may be changed to the configuration shown in Figure 13. For parts of the optical amplification relay device 100E shown in Figure 13 that have the same configuration as the optical amplification relay device 100E shown in Figure 11, the explanation of those configurations will be omitted. The optical amplification relay device 100E shown in Figure 13 differs from the optical amplification relay device 100E shown in Figure 11 in that it does not include an optical demultiplexer 50E and an optical multiplexer 70E. In the optical amplification relay device 100E shown in Figure 13, the optical demultiplexer 10E processes the optical signal input to the optical amplification relay device 100E, which includes signals in the S band, C band, L band, and U band, into S Ｓ Belt, S Ｌ The signal is split into the 5, C, L, and U bands, and the split S Ｓ The signal in the band is output to the optical amplifier 60E, and the S band is deselected. Ｌ The band signal is output to optical amplifier 61E, the decoupled C-band signal is output to optical amplifier 62E, the decoupled L-band signal is output to optical amplifier 63E, and the decoupled U-band signal is output to optical amplifier 64E.

[0069] Furthermore, in the optical amplification relay device 100E shown in Figure 13, the optical multiplexer 80E receives S amplified by the optical amplifier 60E. ＳThe signal in the band and the S amplified by the optical amplifier 61E Ｌ The band signal, the C-band signal amplified by optical amplifier 62E, the L-band signal amplified by optical amplifier 63E, and the U-band signal amplified by optical amplifier 63E are combined and output to the outside of the optical amplification relay device 100E.

[0070] In the optical amplification relay device 100E shown in Figure 13, the optical demultiplexer 50E and the optical multiplexer 70E can be omitted compared to the optical amplification relay device 100E shown in Figure 11, thus simplifying the configuration of the device.

[0071] [Fourth Embodiment] Next, an optical amplification relay device according to the fourth embodiment of the present invention will be described. Figure 14 is a schematic configuration diagram of the optical amplification relay device 100F according to the fourth embodiment of the present invention. The optical amplification relay device 100F includes an optical demultiplexer 10F, optical amplifiers 20F, 21F, 22F, wavelength selective switches (WSS) 30F, 31F, 32F, 33F, 40F, 41F, 42F, 43F, an optical demultiplexer 50F, optical amplifiers 60F, 61F, 62F, 63F, an optical multiplexer 70F, and an optical multiplexer 80F.

[0072] The optical demultiplexer 10F demultiplexes the optical signal input to the optical amplification relay device 100D, which includes signals in the S band, C band, L band, and U band, into S band, C band, L band, and U band signals. It then outputs the demultiplexed S band signal to the optical amplifier 20F, the demultiplexed C band signal to the optical amplifier 21F, the demultiplexed L band signal to the optical amplifier 22F, and the demultiplexed U band signal to the optical amplifier 23F.

[0073] Optical amplifier 20F amplifies the S-band signal input from optical demultiplexer 10F by a predetermined amount (e.g., 3 dB) and outputs it to wavelength-selective switch 30F. Optical amplifier 21F amplifies the C-band signal input from optical demultiplexer 10F by a predetermined amount (e.g., 3 dB) and outputs it to wavelength-selective switch 31F. Optical amplifier 22F amplifies the L-band signal input from optical demultiplexer 10F by a predetermined amount (e.g., 3 dB) and outputs it to wavelength-selective switch 32F. Optical amplifier 23F amplifies the U-band signal input from optical demultiplexer 10F by a predetermined amount (e.g., 3 dB) and outputs it to wavelength-selective switch 33F.

[0074] Wavelength-selective switch 30F inserts an S-band signal into the S-band signal input from optical amplifier 20F as needed and outputs it to wavelength-selective switch 40F. Wavelength-selective switch 31F inserts a C-band signal into the C-band signal input from optical amplifier 21F as needed and outputs it to wavelength-selective switch 41F. Wavelength-selective switch 32F inserts an L-band signal into the L-band signal input from optical amplifier 22F as needed and outputs it to wavelength-selective switch 42F. Wavelength-selective switch 33F inserts a U-band signal into the U-band signal input from optical amplifier 23F as needed and outputs it to wavelength-selective switch 43F.

[0075] Wavelength-selective switch 40F outputs the remaining S-band signal to optical demultiplexer 50F after branching the S-band signal from the S-band signal input from wavelength-selective switch 30F as needed. Wavelength-selective switch 41F outputs the remaining C-band signal to optical amplifier 62F after branching the C-band signal from the C-band signal input from wavelength-selective switch 31F as needed. Wavelength-selective switch 42F outputs the remaining L-band signal to optical amplifier 63F after branching the L-band signal from the L-band signal input from wavelength-selective switch 32F as needed. Wavelength-selective switch 43F outputs the remaining U-band signal to optical amplifier 64F after branching the U-band signal from the U-band signal input from wavelength-selective switch 33F as needed.

[0076] The optical demultiplexer 50F converts the S-band signal from 1460 nm to 1530 nm input from the wavelength-selective switch 40F into an S-band signal from 1460 nm to 1495 nm. Ｓ The band signal and S from 1495 nm to 1530 nm Ｌ The signal is split into two, and the split S Ｓ The band signal is output to the optical amplifier 60F, and the S band is desequently converted. Ｌ The band signal is output to the optical amplifier 61F.

[0077] The optical amplifier 60F receives S from the optical demultiplexer 50F. ＳThe signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 70F. The optical amplifier 61F receives the S from the optical demultiplexer 50F. Ｌ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 70F. The optical multiplexer 70F receives the S from the optical amplifier 60F. Ｓ The signal in the band and the S input from the optical amplifier 61F Ｌ The signal from the band is combined with the signal and output to the optical multiplexer 80F.

[0078] Optical amplifier 62F amplifies the C-band signal input from the wavelength-selective switch 41F by a predetermined amount (e.g., 3 dB) and outputs it to the optical multiplexer 80F. Optical amplifier 63F amplifies the L-band signal input from the wavelength-selective switch 42F by a predetermined amount (e.g., 3 dB) and outputs it to the optical multiplexer 80F. Optical amplifier 64F amplifies the U-band signal input from the wavelength-selective switch 43F by a predetermined amount (e.g., 3 dB) and outputs it to the optical multiplexer 80F.

[0079] The optical multiplexer 80F combines the S-band signal input from the optical multiplexer 70F, the C-band signal input from the optical amplifier 62F, the L-band signal input from the optical amplifier 63F, and the U-band signal input from the optical amplifier 64F, and outputs the combined signal to the outside of the optical amplification relay device 100F.

[0080] In the optical amplifier relay device 10F of the fourth embodiment, the wavelength-selective switches 30F, 31F, 32F, 33F, 40F, 41F, 42F, and 43F constitute a ROADM (Reconfigurable Optical Add-Drop Multiplexer). By providing the wavelength-selective switches 30F, 31F, 32F, 33F, 40F, 41F, 42F, and 43F, it becomes possible to insert, split, or equalize optical signals in any bandwidth. Therefore, the insertion loss of the wavelength-selective switches 30F, 31F, 32F, 33F is compensated by the optical amplifiers 60F, 61F, 62F, 63F, and 64F provided downstream of the wavelength-selective switches 30F, 31F, 32F, and 43F, and a WDM signal is output.

[0081] The optical amplification relay device 10F of the fourth embodiment can achieve the same effects as the optical amplification relay device 10E of the third embodiment. Furthermore, compared to the optical amplification relay device 10E of the third embodiment, the optical amplification relay device 10F of the fourth embodiment further includes wavelength-selective switches 30F, 31F, 32F, 33F, 40F, 41F, 42F, and 43F (also referred to as optical insertion branching multiplexers) that add or delete optical signals for signals in the C-band, L-band, U-band, and S-band.

[0082] In the optical amplification relay device 10F of the fourth embodiment, after processing by wavelength-selective switches 30F and 40F, S is performed by the optical demultiplexer 50F. Ｓ Obi and S Ｌ By splitting the signal into different frequency bands and amplifying it optically using optical amplifiers 60F and 61F, the power spectral density of the S-band can be increased.

[0083] Note that the configuration of the optical amplification relay device 100F shown in Figure 14 may be changed to the configuration shown in Figure 15. For parts of the optical amplification relay device 100F shown in Figure 15 that have the same configuration as the optical amplification relay device 100F shown in Figure 14, the explanation of those configurations will be omitted. The optical amplification relay device 100F shown in Figure 15 differs from the optical amplification relay device 100F shown in Figure 14 in that it does not include an optical multiplexer 70F.

[0084] In the optical amplification relay device 100F shown in Figure 15, the optical amplifier 60F receives S from the optical demultiplexer 50F. Ｓ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 80F. The optical amplifier 61F receives the S from the optical demultiplexer 50F. Ｌ The signal in the band is amplified by a predetermined amount (for example, 3 dB) and output to the optical multiplexer 80F.

[0085] The optical multiplexer 80F receives S from the optical amplifier 60F. Ｓ The signal in the band and the S input from the optical amplifier 61F Ｌ The band signal, the C-band signal input from optical amplifier 62F, and the L-band signal input from optical amplifier 63F are combined and output to the outside of the optical amplification relay device 100F.

[0086] In the optical amplification relay device 100F shown in Figure 15, the optical multiplexer 70F can be omitted compared to the optical amplification relay device 100F shown in Figure 14, thus simplifying the configuration of the device.

[0087] [Fifth Embodiment] Next, an optical amplification relay system according to the fifth embodiment of the present invention (Figure 16) will be described. The optical amplification relay system 1000 according to the fifth embodiment includes an optical amplification relay device 100G, a transmitting device 200G, and a receiving device 300G. The optical amplification relay device 100G, the transmitting device 200G, and the receiving device 300G are connected by an optical fiber transmission line 400G.

[0088] The optical amplification relay device 100G is composed of any of the optical amplification relay devices 100C to 100F according to the first to fourth embodiments described above. The transmitting device 200G transmits an optical signal including the S-band, C-band, and L-band, or an optical signal including the S-band, C-band, L-band, and U-band, to the optical amplification relay device 100G via the optical fiber transmission line 400G. The receiving device 300G receives the optical signal transmitted by the optical amplification relay device 100G, which has an increased power spectral density in the S-band.

[0089] According to the fifth embodiment, an optical amplification relay system 1000 can be constructed that can obtain the same effects as the first embodiment.

[0090] [Sixth Embodiment] Next, an optical amplification relay system according to the sixth embodiment of the present invention (Figure 17) will be described. The optical amplification relay system 2000 according to the sixth embodiment comprises an optical amplification relay device 100H, a transmitting device 200H, and a receiving device 300H. The optical amplification relay device 100H, the transmitting device 200H, and the receiving device 300H are connected by an optical fiber transmission line 400H.

[0091] The optical amplification relay device 100H is composed of any of the optical amplification relay devices 100C to 100F according to the first to fourth embodiments described above. The transmitting device 200H transmits an optical signal including the S-band, C-band, and L-band, or an optical signal including the S-band, C-band, L-band, and U-band, to the optical amplification relay device 100H via the optical fiber transmission line 400H. The receiving device 300H receives the optical signal transmitted by the optical amplification relay device 100H, which has an increased power spectral density in the S-band.

[0092] In the sixth embodiment, when the optical amplifier relay device 100H transmits an optical signal to the receiving device 300H, pre-emphasis is applied by adjusting the optical signal so that the power spectral density decreases as the wavelength increases. When pre-emphasis is applied, the WDM signal is transmitted to the optical fiber transmission line with a non-flat spectral shape, for example, by setting the short wavelength band to a higher value in advance, taking into account the wavelength dependence of losses associated with optical fiber transmission, including stimulated Raman scattering. As a result, the characteristics of the WDM channel, which has poor signal quality, are improved compared to when a flat spectrum is transmitted. Generally, pre-emphasis is performed by the excitation current of the optical amplifier or by a wavelength-selective switch, but by applying the embodiments described in Figure 1 or 2, Figure 3 or 4, and Figure 5, the degree of freedom of pre-emphasis is increased, and it is expected that the overall signal quality of the WDM signal will be kept high and the system performance will be improved by applying more appropriate pre-emphasis. In other words, it is expected that the total capacity will be increased, or the wavelength dependence of the signal quality between WDM channels will be reduced, eliminating the need for adaptive processing. Specifically, the amount of pre-emphasis required for various paths and the corresponding number of band divisions are determined through simulations and experiments beforehand, and then the optical amplifiers and ROADMs are constructed. During operation, the excitation current of the optical amplifiers assigned to each band divided within a single band is optimized, taking into account the necessary pre-emphasis corresponding to the path, and the desired pre-emphasis is achieved with higher precision by combining this with wavelength-selective switches.

[0093] In the first to fourth embodiments described above, the optical amplifier can be a thulium-doped optical fiber optical amplifier, a bismuth-doped optical fiber optical amplifier, an optical parametric optical amplifier, a semiconductor optical fiber optical amplifier, a concentrated Raman optical amplifier, or the like.

[0094] Furthermore, while the first to fourth embodiments described above describe the case where the S-band signal is divided into two and optically amplified, the invention is not limited to this. For example, in order to increase the power spectral density, the S-band signal may be divided into three or more parts, and each of the divided signals may be optically amplified.

[0095] Furthermore, in the first to fourth embodiments described above, by splitting at the center of the S-band wavelength, Ｓ Obi and S Ｌ We have explained the case of dividing the band into two, but as explained in Figure 3, the S band can also be divided at a wavelength that is not the center of the S band.

[0096] In the third and fourth embodiments, the case of increasing the power spectral density of the S-band among the optical signals including the S-band, C-band, L-band, and U-band has been described, but the invention is not limited to these embodiments. For example, the power spectral density of the U-band may be increased using a method similar to the method for increasing the power spectral density of the S-band, or the power spectral density of both the S-band and U-band may be increased.

[0097] In the second and fourth embodiments, a ROADM may be constructed by combining N×N optical multiplexers. If the degradation of the noise figure due to insertion loss of the optical demultiplexer after processing by the wavelength-selective switch is a problem, an optical amplifier may be inserted after processing by the wavelength-selective switch but before processing by the optical demultiplexer to amplify the S-band signal once before performing band-division amplification. If it is desired to increase the output power of the optical amplifier before processing by the wavelength-selective switch (for example, if the optical spectral equalization loss at the wavelength-selective switch is large), the configuration described in the embodiment of Figure 1 or Figure 2, or Figure 3 or Figure 4 may be applied between the optical amplifier before processing by the wavelength-selective switch and the wavelength-selective switch, or the optical amplifier before processing by the wavelength-selective switch may be replaced with the configuration described in the embodiment of Figure 1 or Figure 2, or Figure 3 or Figure 4.

[0098] Furthermore, at least some of the functions of each part of the optical amplification relay devices 100C to 100F in the first to fourth embodiments described above may be implemented by a computer. In that case, the functions may be implemented by recording a program for implementing these functions on a computer-readable recording medium, loading the program recorded on this recording medium into a computer system, and executing it. Here, "computer system" includes hardware such as an OS (Operating System) and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), CD-ROMs, and storage devices such as hard disks built into a computer system. Moreover, "computer-readable recording medium" may also include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, and those that hold programs for a certain period of time, such as volatile memory inside a computer system that acts as a server or client in such cases. Furthermore, the above program may be for implementing some of the functions described above, or it may be a program that can implement the above functions in combination with a program already recorded in the computer system, or it may be implemented using a programmable logic device such as an FPGA.

[0099] Although the first to fourth embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of the invention.

[0100] The present invention can be applied to optical amplification relay devices, optical amplification relay systems, and optical amplification relay methods, etc., which require preventing a decrease in the power spectral density of a new bandwidth even when optical communication is performed using a new bandwidth in addition to a predetermined bandwidth.

[0101] 10C, 10D, 10E, 10F... Optical demultiplexers, 20A, 20B, 20C, 20D, 20E, 20F, 21D, 21F, 22D, 22F, 23F... Optical amplifiers, 30D, 30F, 31D, 31F, 32D, 32F, 33F... Wavelength-selective switches, 40D, 40F, 41D, 41F, 42D, 42F, 43F... Wavelength-selective switches, 50A, 50B, 50C, 50D, 50E, 50F... Optical demultiplexers, 60A, 60B, 60C, 60D, 60E, 60F, 61A, 61B, 61C, 61D, 61E, 61F, 62C, 62D, 62E, 62F, 63C, 63D, 63E, 63F, 64E, 64F... Optical amplifiers, 70A, 70B, 70C, 70D, 70E, 70F... Optical multiplexers, 80C, 80D, 80E, 80F... Optical multiplexers, 100C, 100D, 100E, 100F... Optical amplification relay devices, 200G, 200H... Transmitting devices, 300G, 300H... Receiving devices, 400G, 400H... Optical fiber transmission lines, 1000, 2000... Optical amplification relay systems

Claims

1. An optical amplification relay device comprising: a demultiplexing unit that demultiplexes an optical signal including a signal of a first band and a signal of a second band into the signal of the first band and the signal of the second band; a power spectral density adjustment unit that increases the power spectral density of the signal of the second band demultiplexed by the demultiplexing unit; and a multiplier unit that combines the signal of the second band, whose power spectral density has been increased by the power spectral density adjustment unit, with the signal of the first band.

2. The optical amplification relay device according to claim 1, wherein the power spectral density adjustment unit increases the power spectral density of the signal in the second band by optically amplifying the signal in the second band delimited by the demultiplexing unit, or by reducing the bandwidth used for the signal in the second band delimited by the demultiplexing unit.

3. The optical amplification relay device according to claim 1, further comprising an optical insertion branch multiplexing unit for adding or deleting optical signals to the signals of the first bandwidth and the signals of the second bandwidth.

4. The optical amplification relay device according to claim 1, wherein the first band includes a C band with wavelengths of 1530 nm to 1565 nm and an L band with wavelengths of 1565 nm to 1625 nm, and the second wavelength includes an S band with wavelengths of 1460 nm to 1530 nm.

5. The optical amplification relay device according to claim 4, wherein the first band further includes a U band with a wavelength of 1625 nm to 1675 nm, in addition to the C band and the L band.

6. An optical amplification relay system comprising: a transmitting device for transmitting the optical signal to the optical amplification relay device described in claim 1; the optical amplification relay device; and a receiving device for receiving the signal combined by the multiplexing unit from the optical amplification relay device.

7. The optical amplification relay system according to claim 6, wherein the optical amplification relay device transmits to the receiving device a signal in which the power spectral density of the signal of the second wavelength is greater than the power spectral density of the signal of the first wavelength.

8. An optical amplification relay method that decouples an optical signal including a signal in a first band and a signal in a second band into the signal in the first band and the signal in the second band, increases the power spectral density of the decoupled signal in the second band, and combines the signal in the second band with the increased power spectral density and the signal in the first band.

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