阅读说明：本技术 传输装置以及传输方法 (Transmission device and transmission method ) 是由 加藤智行 星田刚司 竹山智明 于 2018-02-08 设计创作，主要内容包括：提供减轻部件成本,同时实现传输容量的扩大的传输装置等。传输装置在传输路径传输波长复用光。传输装置具有第一复用部、第二复用部、波长转换部以及第三复用部。第一复用部将第一波长波段的波长的光进行复用而输出第一复用光。第二复用部将所述第一波长波段的波长的光进行复用而输出第二复用光。波长转换部将所述第二复用光转换为与所述第一波长波段不同的第二波长波段的波长。第三复用部将转换为所述第二波长波段的波长的第二复用光和所述第一复用光进行复用而输出所述波长复用光。(Provided is a transmission device and the like which can reduce the component cost and realize the enlargement of the transmission capacity. The transmission device transmits the wavelength-multiplexed light on the transmission path. The transmission device includes a first multiplexing unit, a second multiplexing unit, a wavelength conversion unit, and a third multiplexing unit. The first multiplexing unit multiplexes the light having the wavelength of the first wavelength band and outputs first multiplexed light. The second multiplexing unit multiplexes the light having the wavelength of the first wavelength band and outputs second multiplexed light. The wavelength conversion unit converts the second multiplexed light into a wavelength of a second wavelength band different from the first wavelength band. The third multiplexing unit multiplexes the first multiplexed light and the second multiplexed light converted into the wavelength of the second wavelength band and outputs the wavelength-multiplexed light.)

1. A transmission device that transmits wavelength-multiplexed light on a transmission path, the transmission device comprising:

A first multiplexing unit that multiplexes light having a wavelength in a first wavelength band and outputs first multiplexed light;

A second multiplexing unit that multiplexes the light having the wavelength in the first wavelength band and outputs second multiplexed light;

A wavelength conversion unit that converts the second multiplexed light into a wavelength of a second wavelength band different from the first wavelength band; and

And a third multiplexing unit that multiplexes the first multiplexed light and the second multiplexed light converted into the wavelength of the second wavelength band and outputs the wavelength-multiplexed light.

2. Transmission device according to claim 1,

The wavelength conversion unit converts the second multiplexed light into light having a wavelength in the second wavelength band by propagating the second multiplexed light and the excitation light through a nonlinear medium.

3. The transmission device according to claim 1 or 2, further comprising an optical amplification unit that amplifies the second multiplexed light converted into the wavelength of the second wavelength band.

4. the transmission device according to claim 2, further comprising an optical amplification unit that amplifies the second multiplexed light converted into the wavelength of the second wavelength band,

Wherein the optical amplification section amplifies the second multiplexed light converted into the wavelength of the second wavelength band with the excitation light as an excitation light source.

5. Transmission device according to claim 3 or 4,

The wavelength conversion section causes the modulated excitation light to propagate in the nonlinear medium.

6. The transmission device according to any one of claims 2 to 5, further comprising an adjustment unit that monitors the optical level of the second multiplexed light output from the wavelength conversion unit and adjusts the power level of the excitation light based on the monitoring result.

7. The transmission device according to any one of claims 2 to 5, further comprising an adjustment unit that monitors the optical level of the second multiplexed light output from the wavelength conversion unit and adjusts the optical level of the second multiplexed light output from the wavelength conversion unit based on the monitoring result.

8. transmission device according to any one of claims 1 to 7,

A dispersion compensation unit is provided between the wavelength conversion unit and the third multiplexing unit or at a stage before the wavelength conversion unit.

9. The transmission apparatus according to any one of claims 1 to 8, characterized by having:

A first separation unit that separates the wavelength-multiplexed light received from the transmission path into light having a wavelength of the first wavelength band and light having a wavelength of the 2 nd wavelength band;

a second separation unit that wavelength-separates light having a wavelength in the first wavelength band;

A second wavelength converter that converts the light having the wavelength of the second wavelength band separated by the first separator into the wavelength of the first wavelength band; and

And a third separation section that wavelength-separates the light converted into the wavelength of the first wavelength band.

10. Transmission device according to claim 8,

The second wavelength conversion section converts the light having the wavelength in the second wavelength band into the light having the wavelength in the first wavelength band by propagating the light having the wavelength in the second wavelength band separated by the first separation section and the excitation light in a nonlinear medium.

11. A transmission method of transmitting wavelength multiplexed light on a transmission path, the transmission method characterized by performing:

Multiplexing light having a wavelength of a first wavelength band to output first multiplexed light;

Multiplexing the light having the wavelength of the first wavelength band to output a second multiplexed light;

Converting the second multiplexed light to wavelengths in a second wavelength band different from the first wavelength band; and

Multiplexing the first multiplexed light and the second multiplexed light converted into the wavelength of the second wavelength band.

12. A transmission device that transmits wavelength-multiplexed light on a transmission path, the transmission device comprising:

A wavelength conversion unit that converts first multiplexed light obtained by multiplexing light having a wavelength in a first wavelength band into a wavelength in a second wavelength band different from the first wavelength band;

An optical amplification unit that amplifies the first multiplexed light converted into the wavelength of the second wavelength band; and

And a multiplexing unit that multiplexes a second multiplexed light obtained by multiplexing light having a wavelength in the first wavelength band and the amplified first multiplexed light, and outputs wavelength-multiplexed light.

13. A transmission apparatus, comprising:

A first wavelength conversion unit that converts first multiplexed light, which is obtained by multiplexing light having a wavelength in a first wavelength band, into a wavelength in a second wavelength band, which is a wavelength band different from the first wavelength band, by propagating the first multiplexed light and excitation light in a nonlinear medium;

A multiplexing unit that multiplexes the first multiplexed light converted into the wavelength of the second wavelength band and a second multiplexed light obtained by multiplexing the light of the wavelength of the first wavelength band and outputs the multiplexed light to a transmission path;

A separation unit that separates the wavelength-multiplexed light from the transmission path into light having a wavelength in the first wavelength band and light having a wavelength in the second wavelength band; and

And a second wavelength converter that converts the light having the wavelength in the second wavelength band into the light having the wavelength in the first wavelength band by propagating the light having the wavelength in the second wavelength band separated by the separator and the excitation light in a nonlinear medium.

14. The transmission apparatus according to claim 13,

The second wavelength conversion unit converts the light having the wavelength in the second wavelength band into the light having the wavelength in the first wavelength band by propagating the residual excitation light of the excitation light used by the first wavelength conversion unit and the light having the second wavelength band through the nonlinear medium.

Technical Field

The present invention relates to a transmission device and a transmission method.

Background

In recent years, as the demand for communication has expanded, for example, as the number of optical fiber cores has increased, it has been required to increase the transmission capacity by increasing the capacity of optical signals per Wavelength or increasing the number of Wavelength Division Multiplexing (WDM) channels.

However, since the laying cost of the optical fiber is high, it is required to increase the transmission capacity by increasing the optical signal capacity or the number of WDM channels without increasing the number of optical fiber cores. In a transmission device, for example, communication using a C-Band (Conventional Band) optical wavelength of 1530 to 1565nm is realized, but there is a limitation in expanding the transmission capacity only by the C-Band.

Therefore, the transmission device further expands the transmission capacity by using a communication Band such as an L Band (Long-Band) in a Long wavelength region of 1565nm to 1625nm and an S Band (Short-Band) in a Short wavelength region of 1460nm to 1530nm in addition to the C Band.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2003-188830

Patent document 2: japanese laid-open patent publication No. 1-149593

Disclosure of Invention

Problems to be solved

However, since the optical components such as the optical transmitting/receiving unit, the wavelength combining/splitting unit, and the optical amplifying unit corresponding to the C-band, the S-band, and the L-band are individually developed, the cost increases compared to the case where only the optical components corresponding to one wavelength band are developed. Therefore, when a plurality of wavelength bands are used in the transmission device, optical components corresponding to each wavelength band are required, and therefore, not only the component cost but also the operation cost is high.

According to one aspect, it is an object to provide a transmission device or the like that reduces component costs while achieving an increase in transmission capacity.

Means for solving the problems

the transmission device of one aspect transmits wavelength-multiplexed light on a transmission path. The transmission device includes a first multiplexing unit, a second multiplexing unit, a wavelength conversion unit, and a third multiplexing unit. The first multiplexing unit multiplexes the light having the wavelength of the first wavelength band and outputs first multiplexed light. The second multiplexing unit multiplexes the light having the wavelength of the first wavelength band and outputs second multiplexed light. The wavelength conversion unit converts the second multiplexed light into a wavelength of a second wavelength band different from the first wavelength band. The third multiplexing unit multiplexes the first multiplexed light and the second multiplexed light converted into the wavelength of the second wavelength band and outputs the wavelength-multiplexed light.

According to an aspect, the component cost is reduced while the enlargement of the transmission amount can be achieved.

drawings

Fig. 1 is an explanatory diagram showing an example of a transmission system according to embodiment 1.

Fig. 2 is an explanatory view showing an example of the wavelength converting region for single polarization and the excitation light source.

Fig. 3A is an explanatory diagram illustrating an example of the wavelength conversion operation of the first wavelength converter.

Fig. 3B is an explanatory diagram illustrating an example of the wavelength conversion operation of the third wavelength converter.

Fig. 4A is an explanatory diagram illustrating an example of the wavelength conversion operation of the second wavelength conversion section.

Fig. 4B is an explanatory diagram illustrating an example of the wavelength conversion operation of the fourth wavelength converter.

Fig. 5 is an explanatory diagram showing an example of the transmission system of embodiment 2.

Fig. 6A is an explanatory diagram illustrating an example of input light for non-dispersion compensation of the light-receiving section.

fig. 6B is an explanatory diagram illustrating an example of input light having dispersion compensation in the light receiving section.

Fig. 7 is an explanatory diagram showing an example of the transmission system of embodiment 3.

Fig. 8 is an explanatory diagram showing an example of the transmission system of embodiment 4.

Fig. 9 is an explanatory diagram illustrating an example of a connection structure of the first excitation light source, the first wavelength conversion section, and the seventh wavelength conversion section.

Fig. 10 is an explanatory diagram showing an example of the transmission system of embodiment 5.

Fig. 11 is an explanatory diagram illustrating an example of a connection structure of the seventh excitation light source, the seventh wavelength converting section, and the first wavelength converting section.

Fig. 12 is an explanatory diagram showing an example of the transmission system of embodiment 6.

Fig. 13 is an explanatory diagram showing an example of the transmission system of embodiment 7.

fig. 14 is an explanatory diagram showing an example of the transmission system of embodiment 8.

Fig. 15 is an explanatory diagram showing an example of the transmission system of embodiment 9.

Fig. 16 is an explanatory diagram showing an example of a connection structure of the second excitation light source for single polarization, the first wavelength conversion section, the second wavelength conversion section, the seventh wavelength conversion section, and the eighth wavelength conversion section of example 9.

Fig. 17 is an explanatory view showing an example of the wavelength converting region for polarization multiplexing and the excitation light source in example 10.

Fig. 18A is an explanatory diagram illustrating an example of the wavelength conversion operation of the first wavelength conversion section in example 10.

Fig. 18B is an explanatory diagram illustrating an example of the wavelength conversion operation of the third wavelength converter in example 10.

Fig. 19A is an explanatory diagram illustrating an example of the wavelength conversion operation of the second wavelength converting region in example 10.

fig. 19B is an explanatory diagram illustrating an example of the wavelength conversion operation of the fourth wavelength converter in example 10.

Fig. 20 is an explanatory diagram showing an example of a connection structure of the first excitation light source for polarization-multiplexed light, the first wavelength converting region, and the seventh wavelength converting region of example 11.

Fig. 21 is an explanatory view showing an example of a connection structure of the seventh excitation light source for polarization multiplexing light, the first wavelength conversion unit, and the seventh wavelength conversion unit according to example 12.

Fig. 22 is an explanatory diagram showing an example of a connection structure of the second excitation light source for polarization-multiplexed light, the first wavelength converting region, the second wavelength converting region, the seventh wavelength converting region, and the eighth wavelength converting region in example 13.

Fig. 23 is an explanatory view showing an example of the wavelength converting region for polarization multiplexing light and the excitation light source of example 14.

Fig. 24 is an explanatory diagram showing an example of the transmission system of embodiment 15.

Fig. 25 is an explanatory diagram showing an example of a connection structure of the first excitation light source, the first wavelength conversion unit, and the fifth optical amplification unit.

Fig. 26 is an explanatory diagram showing an example of a connection structure of the third excitation light source, the third wavelength conversion unit, and the sixth optical amplification unit.

Fig. 27 is an explanatory diagram showing an example of the transmission system of embodiment 16.

Fig. 28 is an explanatory diagram showing an example of a connection structure of the first excitation light source, the first wavelength conversion unit, and the seventh optical amplification unit.

Fig. 29 is an explanatory diagram showing an example of a connection structure of the third excitation light source, the third wavelength conversion unit, and the eighth optical amplification unit.

Fig. 30 is an explanatory diagram showing an example of the transmission system of embodiment 17.

Fig. 31 is an explanatory diagram showing an example of a connection structure of the first excitation light source, the first wavelength conversion unit, and the ninth optical amplification unit.

Fig. 32 is an explanatory diagram showing an example of a connection structure of the third excitation light source, the third wavelength conversion unit, and the tenth optical amplification unit.

Fig. 33 is an explanatory diagram showing an example of the transmission system of embodiment 18.

Fig. 34 is an explanatory diagram showing an example of the transmission system of embodiment 19.

Fig. 35 is an explanatory diagram showing an example of the transmission system according to embodiment 20.

Fig. 36 is an explanatory diagram showing an example of the transmission system of embodiment 21.

Fig. 37 is an explanatory diagram showing an example of the transmission system of embodiment 22.

Fig. 38 is an explanatory diagram showing an example of the transmission system of embodiment 23.

Fig. 39 is an explanatory diagram showing an example of the transmission system of embodiment 24.

fig. 40 is an explanatory diagram showing an example of the output of the excitation light.

Detailed Description

Hereinafter, embodiments of the transmission device and the transmission method disclosed in the present application will be described in detail with reference to the drawings. The disclosed technology is not limited to the embodiments. Further, the embodiments shown below may be combined as appropriate within a range not conflicting.

Fig. 1 is an explanatory diagram showing an example of a transmission system 1 according to embodiment 1. The transmission system 1 shown in fig. 1 includes a first transmission device 2A, a second transmission device 2B, and a transmission path 3 such as an optical fiber for transmitting wavelength-multiplexed light between the first transmission device 2A and the second transmission device 2B. The first transmission device 2A includes a plurality of light transmission units 11, a plurality of multiplexer units 12, a plurality of light amplification units 13, a plurality of wavelength conversion units 14, a plurality of excitation light sources 15, and a wavelength multiplexer unit 16.

The plurality of light transmission units 11 include a plurality of light transmission units 11A corresponding to a first group, a plurality of light transmission units 11B corresponding to a second group, and a plurality of light transmission units 11C corresponding to a third group. The light transmission unit 11A of the first group includes, for example, N units, and transmits first light beams having different wavelengths in a wavelength range of C band (for example, 1530nm to 1565 nm). The light transmission unit 11B of the second group includes, for example, an X-station, and transmits second light beams having different wavelengths in the C-band wavelength range. Further, the light transmission unit 11C corresponding to the third group includes, for example, Y stations, and transmits third light beams having different wavelengths in the C band wavelength range. The light transmitting unit 11A, the light transmitting unit 11B, and the light transmitting unit 11C are light transmitting units 11 corresponding to the C band.

The plurality of wave combining units 12 include, for example, a first wave combining unit 12A corresponding to the first group, a second wave combining unit 12B corresponding to the second group, and a third wave combining unit 12C corresponding to the third group. The plurality of light amplification sections 13 include first light amplification sections 13A corresponding to the first group, second light amplification sections 13B corresponding to the second group, and third light amplification sections 13C corresponding to the third group. The wavelength conversion section 14 converts the multiplexed light into multiplexed light of an arbitrary wavelength band by propagating the multiplexed light and the excitation light through the nonlinear optical medium. The plurality of wavelength converting regions 14 include first wavelength converting regions 14A corresponding to the second group and second wavelength converting regions 14B corresponding to the third group. The plurality of excitation light sources 15 include a first excitation light source 15A that supplies excitation light to the first wavelength converting regions 14A corresponding to the second group and a second excitation light source 15B that supplies excitation light to the second wavelength converting regions 14B corresponding to the third group.

the first multiplexer 12A is a first multiplexer that multiplexes the first light from the respective light transmitters 11A in the first group and outputs the multiplexed first light to the first optical amplifier 13A. The transmission wavelength of each port of the first multiplexer 11A is designed according to the wavelength band of the first light output from each light transmitter 11A. In the present embodiment, the transmission band of each port is designed according to the band of the C band. The first optical amplifier 13A optically amplifies the first multiplexed light from the first multiplexer 12A, and outputs the optically amplified first multiplexed light to the wavelength multiplexer 16. The first multiplexed light is a C-band multiplexed light in the first wavelength band.

The second multiplexer 12B is a second multiplexer that multiplexes the second light from the respective light transmitters 11B in the second group and outputs the multiplexed second light to the second optical amplifier 13B. The transmission wavelength of each port of the second multiplexer 12B is designed according to the wavelength band of the second light output from each light transmitter 11B. In the present embodiment, the transmission band of each port is designed according to the band of the C band. The second optical amplification unit 13B optically amplifies the second multiplexed light from the second multiplexer unit 12B, and outputs the optically amplified second multiplexed light to the first wavelength conversion unit 14A. The second multiplexed light is multiplexed light in the C band. The first wavelength converter 14A wavelength-converts the second multiplexed light in the C band from the second optical amplifier 13B into the second multiplexed light in the L band, and outputs the wavelength-converted second multiplexed light to the wavelength multiplexer 16. The wavelength range of the L band as the second wavelength band is, for example, a long wavelength region of 1565nm to 1625 nm.

The third multiplexer 12C is a second multiplexer that multiplexes the third light from the light transmitters 11C in the third group and outputs the multiplexed third light to the third optical amplifier 13C. The transmission wavelength of each port of the third multiplexing unit 12C is designed according to the wavelength band of the third light output from each light transmission unit 11C. In the present embodiment, the transmission band of each port is designed according to the band of the C band. The third optical amplification unit 13C optically amplifies the third multiplexed light from the third multiplexing unit 12C and outputs the optically amplified third multiplexed light to the second wavelength conversion unit 14B. The third multiplexed light is multiplexed light in the C band. The second wavelength converter 14B wavelength-converts the third multiplexed light in the C band from the third optical amplifier 13C into the third multiplexed light in the S band, and outputs the wavelength-converted third multiplexed light to the wavelength multiplexer 16. The wavelength range of the S band as the second wavelength band is, for example, a short wavelength region of 1460nm to 1530 nm. The wavelength multiplexing unit 16 is a third multiplexing unit that outputs the multiplexed light of the first multiplexed light in the C band, the second multiplexed light in the L band, and the third multiplexed light in the S band to the transmission path 3.

As described above, since the transmission wavelength band of each port of the multiplexer 12 can be designed to match the C band, a common component can be used as the multiplexer 12.

The second transmission device 2B has a wavelength demultiplexing section 17, a plurality of wavelength conversion sections 14, a plurality of excitation light sources 15, a plurality of optical amplification sections 13, a plurality of demultiplexing sections 18, and a plurality of light receiving sections 19. The plurality of wavelength converting regions 14 have a second group of corresponding third wavelength converting regions 14C and a third group of corresponding fourth wavelength converting regions 14D. The plurality of excitation light sources 15 include a third excitation light source 15C that supplies excitation light to the third wavelength converting section 14C corresponding to the second group and a fourth excitation light source 15D that supplies excitation light to the fourth wavelength converting section 14D corresponding to the third group.

The plurality of light amplification sections 13 include first light amplification sections 13A corresponding to the first group, second light amplification sections 13B corresponding to the second group, and third light amplification sections 13C corresponding to the third group. The optical amplification units 13 receive the first multiplexed light, the second multiplexed light, and the third multiplexed light in the C-band. Therefore, an EDFA (erbium doped Fiber Amplifier) capable of efficiently extracting light having a wavelength in the C-band can be used. The plurality of demultiplexing sections 18 include a first demultiplexing section 18A corresponding to the first group, a second demultiplexing section 18B corresponding to the second group, and a third demultiplexing section 18C corresponding to the third group. The plurality of light receiving sections 19 have a first group corresponding plurality of light receiving sections 19A, a second group corresponding plurality of light receiving sections 19B, and a third group corresponding plurality of light receiving sections 19C. The light-receiving sections 19A, 19B, and 19C are light-receiving sections corresponding to the C-band.

The wavelength demultiplexing unit 17 is a first splitter for demultiplexing the multiplexed light from the transmission path 3 into a first multiplexed light in the C band, a second multiplexed light in the L band, and a third multiplexed light in the S band. The wavelength demultiplexing unit 17 outputs the demultiplexed C-band first multiplexed light to the first optical amplification unit 13A. The first optical amplification section 13A optically amplifies the first multiplexed light of the C band from the wavelength demultiplexing section 17, and outputs the optically amplified first multiplexed light of the C band to the first demultiplexing section 18A. The first demultiplexing unit 18A is a second demultiplexing unit that demultiplexes the C-band first multiplexed light from the first optical amplification unit 13A into first light and outputs each of the first light to each of the light receiving units 19A. The transmission wavelength band of each output port of the first demultiplexing unit 18A is designed according to the wavelength band of the wavelength received by the connected light receiving unit 19A. Since the wavelength band of the wavelength received by the light-receiving unit 19A is the C band, the transmission wavelength band is designed according to the wavelength of the C band.

The wavelength demultiplexing section 17 outputs the demultiplexed L-band second multiplexed light to the third wavelength converting section 14C. The third wavelength conversion unit 14C wavelength-converts the L-band second multiplexed light into the C-band second multiplexed light by propagating the excitation light from the third excitation light source 15C and the L-band second multiplexed light through the nonlinear optical medium 33, and outputs the wavelength-converted C-band second multiplexed light to the second optical amplification unit 13B. The second optical amplifier 13B optically amplifies the C-band second multiplexed light from the third wavelength converter 14C, and outputs the optically amplified C-band second multiplexed light to the second demultiplexer 18B. The second demultiplexing unit 18B is a third demultiplexing unit that demultiplexes the C-band second multiplexed light from the second optical amplification unit 13B into second light and outputs the second light to the light receiving units 19B. The transmission wavelength band of each output port of the second demultiplexing unit 18B is designed according to the wavelength band of the wavelength received by the connected light receiving unit 19B. Since the wavelength band of the wavelength received by the light-receiving unit 19B is the C band, the transmission wavelength band is designed according to the wavelength of the C band.

The wavelength demultiplexing section 17 outputs the demultiplexed S-band third multiplexed light to the fourth wavelength conversion section 14D. The fourth wavelength converter 14D wavelength-converts the third multiplexed light of the S band into the third multiplexed light of the C band by propagating the excitation light from the fourth excitation light source 15D and the fourth multiplexed light of the S band in the nonlinear optical medium 33, and outputs the wavelength-converted third multiplexed light of the C band to the third optical amplifier 13C. The third optical amplification section 13C optically amplifies the C-band third multiplexed light from the fourth wavelength conversion section 14D, and outputs the optically amplified C-band third multiplexed light to the third demultiplexing section 18C. The third demultiplexing unit 18C is a third demultiplexing unit that demultiplexes the C-band third multiplexed light from the third optical amplification unit 13C into third light and outputs each of the third light demultiplexed into each of the light receiving units 19C. The transmission wavelength band of each output port of the third demultiplexing unit 18C is designed according to the wavelength band of the wavelength received by the connected light receiving unit 19C. Since the wavelength band of the wavelength received by the light-receiving section 19C is the C band, the transmission wavelength band is designed according to the wavelength of the C band.

Fig. 2 is an explanatory diagram showing an example of the wavelength converting region 14 for single polarization and the excitation light source 15. The excitation light source 15 shown in fig. 2 includes a light source 21, a phase modulation unit 22, a signal source 23, an optical amplification unit 24, and an adjustment unit 25. The light source 21 is an LD (Laser Diode) that outputs excitation light. The signal source 23 outputs an electric signal of a predetermined frequency. The phase modulation unit 22 phase-modulates the excitation light from the light source 21 by an electric signal from the signal source 23, and outputs the phase-modulated excitation light to the optical amplification unit 24. The optical amplifier 24 optically amplifies the phase-modulated excitation light and outputs the optically amplified excitation light to the adjuster 25. The adjusting section 25 adjusts the light intensity of the optically amplified excitation light and outputs the adjusted excitation light to the wavelength converting section 14.

The wavelength converting region 14 is a single polarization wavelength converting region 141. The wavelength converter 141 includes an adjuster 31, an optical multiplexer 32, a nonlinear optical medium 33, an optical demultiplexer 34, and an optical amplifier 35. The adjusting section 31 adjusts the light intensity of the light and outputs the adjusted light to the optical multiplexer 32. The optical multiplexer 32 multiplexes the excitation light from the excitation light source 15 and the adjusted light, and outputs the multiplexed excitation light and light to the nonlinear optical medium 33. The nonlinear optical medium 33 transmits the excitation light and the light from the optical multiplexer 32, thereby converting the light into a desired wavelength band. The optical demultiplexing unit 34 demultiplexes the light wavelength-converted by the nonlinear optical medium 33 to output residual excitation light, which is transmitted light of the excitation light used for wavelength conversion, and light. The residual excitation light includes the excitation light of the excitation light source 15. Further, the optical amplification section 35 optically amplifies the light demultiplexed by the optical demultiplexing section 34 in wavelength units, and outputs the amplified light. The optical amplification unit 35 amplifies the multiplexed light whose optical power has become small after the wavelength conversion. In the case of this embodiment, since the L-band multiplexed light is amplified, an EDFA for the L-band or a centralized raman amplifier in which the wavelength of the excitation light is 1465nm to 1525nm is used instead of an EDFA for the C-band.

among the wavelengths of the L band, the S band, and the C band, the power loss of the C band is the smallest, and the power loss of the L band and the S band is larger than the C band. Therefore, the light converted into the wavelengths of the L band and the S band by the method can reduce the influence of the power loss larger than the power loss of the C band.

In the present embodiment, the wavelength conversion unit 14 converts the multiplexed light in the C-band into the multiplexed light in the L-band, but when converting the multiplexed light in the C-band into the multiplexed light in the S-band, a centralized raman amplifier having an excitation light wavelength of 1360nm to 1430nm is used as the optical amplification unit 35.

Further, as a problem of the S band, there is a phenomenon called Stimulated Raman Scattering (SRS). In SRS, since the power of light having a short wavelength is shifted to light having a long wavelength, light having an S-band is shifted to the L-band side. As a result, when the S band, the C band, and the L band are simultaneously transmitted, the loss of the S band increases. Therefore, when the light converted to the wavelength of the S band is amplified by the optical amplification unit 35, the light needs to be amplified at a higher amplification factor than the amplification factors of the wavelengths of the L band and the C band, and therefore, the influence of the power loss due to the SRS can be reduced by increasing the excitation light power.

The optical amplifier 35 need not be located inside the wavelength converter 14, but may be provided between the wavelength converter 14 and the wavelength combiner 16.

For convenience of explanation, the wavelength converting region 14 has the same configuration as the first wavelength converting region 14A, the second wavelength converting region 14B, the third wavelength converting region 14C, and the fourth wavelength converting region 14D, and therefore the same reference numerals are given thereto, and redundant configurations and operations will not be described. The excitation light source 15 has the same configuration as the first excitation light source 15A, the second excitation light source 15B, the third excitation light source 15C, and the fourth excitation light source 15D, and therefore the same reference numerals are given thereto, and redundant configurations and operations will not be described.

Fig. 3A is an explanatory diagram illustrating an example of the operation of the first wavelength conversion section 14A. The first wavelength conversion unit 14A converts the wavelength of the C-band second multiplexed light into the L-band second multiplexed light by propagating the C-band second multiplexed light from the second optical amplification unit 13B and the excitation light from the first excitation light source 15A through the nonlinear optical medium 33. As a result, the first wavelength converter 14A has a degenerate four-wave mixing relationship of the second multiplexed light in which the second multiplexed light in the C band is wavelength-converted symmetrically into the L band around the optical wavelength of the excitation light.

Fig. 3B is an explanatory diagram illustrating an example of the operation of the third wavelength conversion unit 14C. The third wavelength converter 14C wavelength-converts the L-band second multiplexed light into C-band second multiplexed light by propagating the L-band second multiplexed light from the wavelength demultiplexing unit 17 and the excitation light from the third excitation light source 15C through the nonlinear optical medium 33. As a result, the third wavelength converter 14C has a degenerate four-wave mixing relationship of the second multiplexed light that is wavelength-converted symmetrically from the second multiplexed light of the L band to the C band, centered on the wavelength of the excitation light.

Fig. 4A is an explanatory diagram illustrating an example of the operation of the second wavelength conversion section 14B. The second wavelength conversion unit 14B wavelength-converts the third multiplexed light in the C band into the third multiplexed light in the S band by propagating the third multiplexed light in the C band from the third optical amplification unit 13C and the excitation light from the third excitation light source 15C through the nonlinear optical medium 33. As a result, the second wavelength conversion section 14B has a relationship of degenerate four-wave mixing of the third multiplexed light that is wavelength-symmetrically converted into the S band from the third multiplexed light of the C band centered on the wavelength of the excitation light.

fig. 4B is an explanatory diagram illustrating an example of the operation of the fourth wavelength conversion section 14D. The fourth wavelength converter 14D wavelength-converts the third multiplexed light of the S band into the third multiplexed light of the C band by propagating the third multiplexed light of the S band from the wavelength demultiplexing unit 17 and the excitation light from the fourth excitation light source 15D in the nonlinear optical medium 33. As a result, the fourth wavelength converter 14D has a degenerate four-wave mixing relationship of the third multiplexed light that is wavelength-symmetrically converted from the third multiplexed light of the S band to the third multiplexed light of the C band, centered on the optical wavelength of the excitation light.

the first multiplexer 12A in the first transmission device 2A multiplexes the first light from the first group-associated light transmitter 11A and outputs the first multiplexed light in the C band to the wavelength multiplexer 16. Further, the second multiplexer 12B multiplexes the second light from the second group-associated light transmitter 11B and outputs the second multiplexed light of the C band to the first wavelength converter 14A. The first wavelength converter 14A converts the wavelength of the second multiplexed light in the C band into the second multiplexed light in the L band, and outputs the wavelength-converted second multiplexed light in the L band to the wavelength multiplexer 16. Further, the third multiplexer 12C multiplexes the third light from the third group-corresponding light transmitter 11C and outputs the third multiplexed light of the C band to the second wavelength converter 14B. The second wavelength converter 14A wavelength-converts the third multiplexed light in the C band into the third multiplexed light in the S band, and outputs the wavelength-converted third multiplexed light in the S band to the wavelength multiplexer 16.

The wavelength multiplexing unit 16 outputs the multiplexed light of the first multiplexed light of the C band, the second multiplexed light of the L band, and the third multiplexed light of the S band to the transmission path 3. As a result, the first transmission device 2A converts the multiplexed light of the C band from the light transmission units 11 of the second and third groups into multiplexed light of the L band and the S band, and outputs the converted multiplexed light to the transmission path 3. As a result, since a band such as an L band and an S band different from the C band is used for transmission, the transmission capacity can be greatly increased as compared with a single C band. Further, since the light transmitting units 11 of the first to third groups can be configured with the same C-band light transmitting unit 11 and optical components, the product cost and the running cost can be reduced.

Further, the wavelength demultiplexing unit 17 in the second transmission device 2B demultiplexes the multiplexed light from the transmission path 3 into the first multiplexed light in the C band, the second multiplexed light in the L band, and the third multiplexed light in the S band. The wavelength demultiplexing unit 17 demultiplexes the first multiplexed light in the C band to the first demultiplexing unit 18A, demultiplexes the second multiplexed light in the L band to the third wavelength conversion unit 14C, and demultiplexes the third multiplexed light in the S band to the fourth wavelength conversion unit 14D. The third wavelength converter 14C wavelength-converts the second multiplexed light of the L band into the second multiplexed light of the C band, and outputs the wavelength-converted second multiplexed light of the C band to the second wavelength splitter 18B. The fourth wavelength converter 14D wavelength-converts the third multiplexed light of the S band into the third multiplexed light of the C band, and outputs the wavelength-converted third multiplexed light of the C band to the third demultiplexer 18C. The first demultiplexing unit 18A demultiplexes the first multiplexed light of the C band and outputs the demultiplexed light to the light receiving units 19A. The second demultiplexing unit 18B demultiplexes the second multiplexed light of the C band and outputs the demultiplexed light to the light receiving units 19B. The third demultiplexing unit 18C demultiplexes the third multiplexed light in the C band and outputs the demultiplexed light to the light receiving units 19C. As a result, the second transmission device 2B can configure the light-receiving sections 19 and the optical components of the first to third groups with optical components of the C-band, and can reduce the product cost and the running cost.

in other words, in the transmission system 1 according to embodiment 1, in order to realize wavelength division multiplexing communication in different wavelength bands from the first transmission device 2A to the second transmission device 2B, optical components in individual wavelength bands are not used, using optical components such as the common optical transmission unit 11, optical reception unit 19, and optical amplification unit 13. As a result, the transmission device 2 can be formed of a lower-cost optical component.

In the transmission system 1 of example 1, for example, the amount of chromatic dispersion in the transmission path 3 of the second multiplexed light in the L band is larger than that of the second multiplexed light in the C band, and when a standard light-receiving unit in the C band is used as the light-receiving unit 19B, there is a possibility that the chromatic dispersion tolerance is insufficient. Therefore, an embodiment of the transmission system 1 that can cope with such a situation will be described below as example 2.