Optical amplification device and optical amplification method

Abstract

To provide an optical amplification device using a multi-core optical fiber, which solves the problem of low utilization efficiency of pumping light in a cladding pumping method, and an optical amplification method.SOLUTION: In an optical amplification device using a multi-core optical fiber, utilization efficiency of pumping light is low in a cladding pumping method, and the optical amplification device according to the present invention includes first optical waveguide means including a first optical amplification medium, second optical waveguide means including a second optical amplification medium, first pumping light introduction means that introduces the first pumping light that excites the first optical amplification medium into the first optical waveguide means, and first residual pumping light introduction means that introduces first residual pumping light having a wavelength component of the first pumping light output from the first optical waveguide means into the second optical waveguide means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical amplifier and an optical amplification method, and more particularly to an optical amplifier and an optical amplification method using a multi-core optical fiber. [Background technology]

[0002] The rapid expansion of mobile traffic and video services has led to a demand for increased communication capacity in core networks. This demand for increased capacity is likely to continue in the future. Up until now, this expansion has been achieved by using time-division multiplexing and wavelength-division multiplexing technologies. These time-division multiplexing and wavelength-division multiplexing technologies have been applied to optical communication systems using single-core optical fibers.

[0003] When using a single-core optical fiber, there is a limit to the number of multiplexed optical signals that can be transmitted through a single core, i.e., a single optical fiber core, and in recent years, this limit has been reached. This limit is determined by the wavelength bandwidth available in optical fiber communications and the input optical power tolerance of the single-core optical fiber.

[0004] In this situation, spatial multiplexing technology, which is a multiplexing technology of a different dimension from previous multiplexing technologies, is being developed to further expand communication capacity. Spatial multiplexing technologies include multi-core technology, which increases the number of cores per optical fiber, and multi-mode technology, which increases the number of propagation modes. Conventional optical fiber communications use one core and one mode each. Therefore, it is possible to dramatically expand communication capacity by increasing the number of cores and modes.

[0005] However, if the number of cores or modes of an optical fiber is increased, it is not possible to use currently widely used optical transceivers and optical amplifiers as they are. This is because currently popular optical transceivers and optical amplifiers were developed for single-core optical fibers and are not compatible with multi-core optical fibers or multi-mode optical fibers. Therefore, technologies have been proposed to realize optical transceivers and optical amplifiers suitable for multi-core optical fibers and multi-mode optical fibers.

[0006] There are two optical amplification methods suitable for multi-core optical fibers: core pumping and cladding pumping. In the core pumping method, the intensity of the optical signal transmitted through each core is amplified individually using an individual pumping light source for each core. In the cladding pumping method, the intensity of the optical signal transmitted through each core is amplified collectively using a common pumping light source.

[0007] In order to efficiently amplify the optical intensity of an optical signal transmitted through a multi-core optical fiber, a cladding pumping scheme is desirable, in which the intensity of the optical signals transmitted through each core is collectively amplified using a common pumping light source. In addition, in the cladding pumping scheme, the configuration of a conventional optical amplifier using a single-core pumping scheme can, in principle, be used as is for the cladding pumping optical amplifier.

[0008] An example of such an optical amplifier using a cladding pumping method is described in Patent Document 1. A related optical amplifier 10 described in Patent Document 1 includes seven optical isolators 1, an optical fiber fan-in (FAN IN) 2, a semiconductor laser 3, a first optical coupler 4, a multi-core EDF 5, a second optical coupler 6, a pump stripper 7, an optical fiber fan-out (FAN OUT) 8, and seven optical isolators 9.

[0009] Here, the first optical coupler 4 includes a main optical fiber 4a, an optical fiber 4b for inputting and outputting pumping light, an optical fiber 4c for supplying pumping light, and a protector 4d, while the second optical coupler 6 includes a main optical fiber 6a, an optical fiber 6b for inputting and outputting pumping light, and a protector 6d.

[0010] According to the related optical amplifier 10, at least a part of the pumping light output from the semiconductor laser 3 and supplied to the multi-core EDF 5 via the first optical coupler 4, which does not contribute to optical pumping in the multi-core EDF 5, is recovered by the second optical coupler 6. The recovered pumping light passes through the pumping light input / output optical fiber 6b and the pumping light input / output optical fiber 4b, is input to the first optical coupler 4, is regenerated as pumping light, and is supplied again to the multi-core EDF 5. This is said to improve the pumping efficiency in the related optical amplifier 10. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2019 / 117314 Summary of the Invention [Problem to be solved by the invention]

[0012] In cladding pumping optical amplifiers such as the related optical amplifiers described above, the absorption efficiency of the pumping light component in the optical amplifying medium is about 1 / 10 of the absorption efficiency in core pumping. Therefore, compared to core pumping, cladding pumping optical amplifiers have an extremely low utilization efficiency of pumping light.

[0013] As described above, an optical amplifier using a multi-core optical fiber has a problem in that the utilization efficiency of pumping light is low when using the cladding pumping method.

[0014] An object of the present invention is to provide an optical amplifier and an optical amplification method that solve the above-mentioned problem that an optical amplifier using a multi-core optical fiber has low utilization efficiency of pumping light when using a cladding pumping method. [Means for solving the problem]

[0015] The optical amplification device of the present invention comprises a first optical waveguide means including a first optical amplification medium, a second optical waveguide means including a second optical amplification medium, a first pumping light introducing means for introducing first pumping light that excites the first optical amplification medium into the first optical waveguide means, and a first residual pumping light introducing means for introducing first residual pumping light that is output from the first optical waveguide means and has a wavelength component of the first pumping light into the second optical waveguide means.

[0016] The optical amplification method of the present invention includes introducing a first signal light into a first optical waveguide including a first optical amplification medium, introducing a second signal light into a second optical waveguide including a second optical amplification medium, introducing a first pumping light that pumps the first optical amplification medium into the first optical waveguide, and introducing a first residual pumping light that is output from the first optical waveguide and has a wavelength component of the first pumping light into the second optical waveguide. [Effects of the Invention]

[0017] According to the optical amplifier and the optical amplification method of the present invention, even when an optical amplifier having a multi-core optical fiber is used in a cladding pumping system, it is possible to increase the utilization efficiency of pumping light. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram showing a configuration of an optical amplifying device according to a first embodiment of the present invention. [Figure 2] FIG. 3 is a block diagram showing another configuration of the optical amplifying device according to the first embodiment of the present invention. [Figure 3] FIG. 10 is a block diagram showing the configuration of an optical amplifying device according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a block diagram showing another configuration of an optical amplifying device according to the second embodiment of the present invention. [Figure 5] FIG. 10 is a block diagram showing the configuration of an optical amplifying device according to a third embodiment of the present invention. [Figure 6] FIG. 10 is a block diagram showing the configuration of an optical amplifying device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] [First embodiment] 1 is a block diagram showing the configuration of an optical amplifier 100 according to a first embodiment of the present invention. The optical amplifier 100 has a first optical waveguide (first optical waveguide means) 111, a second optical waveguide (second optical waveguide means) 112, a first pumping light introducing section (first pumping light introducing section) 120, and a first residual pumping light introducing section (first residual pumping light introducing section) 131.

[0021] The first optical waveguide 111 includes a first optical amplification medium, and the second optical waveguide 112 includes a second optical amplification medium.

[0022] The first pumping light introducing section 120 introduces the first pumping light 11 that excites the first optical amplification medium into the first optical waveguide 111. Then, the first residual pumping light introducing section 131 introduces the first residual pumping light 21 that is output from the first optical waveguide 111 and has a wavelength component of the first pumping light into the second optical waveguide 112.

[0023] With this configuration, in the optical amplifier 100 according to this embodiment, the pump light output without being absorbed in the first optical amplification medium can be introduced into the second optical waveguide 112 as the first residual pump light 21 and used to pump the second optical amplification medium. Therefore, the optical amplifier 100 according to this embodiment can increase the utilization efficiency of the pump light.

[0024] Fig. 2 shows another configuration of the optical amplifier according to the first embodiment of the present invention. The optical amplifier 101 shown in Fig. 2 is configured to further include a second residual pumping light introducing section (second residual pumping light introducing means) 132 in addition to the configuration of the optical amplifier 100 shown in Fig. 1. Here, the second residual pumping light introducing section 132 introduces the first residual pumping light 21 into the first optical waveguide 111.

[0025] With this configuration, in the optical amplifier 101, the pumping light output without being absorbed in the first optical amplifying medium can be used to pump the second optical amplifying medium and can also be reused to pump the first optical amplifying medium, thereby further increasing the utilization efficiency of the pumping light.

[0026] Here, both the first optical amplifying medium and the second optical amplifying medium can be composed of multiple cores doped with rare-earth ions. Erbium ions can typically be used as the rare-earth ions. The first optical waveguide 111 and the second optical waveguide 112 can both be configured to include a multi-core optical fiber equipped with multiple optical transmission paths each having the above-described multiple cores and a double-clad structure. In this case, the first pumping light introducing section 120 can be configured to introduce the first pumping light 11 into the first optical waveguide 111 by a cladding pumping method.

[0027] Next, the optical amplification method according to this embodiment will be described.

[0028] In the optical amplification method according to this embodiment, first, a first signal light is introduced into a first optical waveguide including a first optical amplification medium, and a second signal light is introduced into a second optical waveguide including a second optical amplification medium. Then, a first pumping light for pumping the first optical amplification medium is introduced into the first optical waveguide, and a first residual pumping light having a wavelength component of the first pumping light output from the first optical waveguide is introduced into the second optical waveguide. Furthermore, the first residual pumping light may also be introduced into the first optical waveguide.

[0029] In this way, in the optical amplification method of this embodiment, the pump light output without being absorbed in the first optical amplification medium can be introduced into the second optical waveguide as the first residual pump light and used to pump the second optical amplification medium. Therefore, the optical amplification method of this embodiment can increase the utilization efficiency of the pump light.

[0030] As described above, according to the optical amplifiers 100 and 101 and the optical amplification method of the present embodiment, even when an optical amplifier having a multi-core optical fiber is used in a cladding pumping system, it is possible to increase the utilization efficiency of pumping light.

[0031] Second Embodiment Next, a second embodiment of the present invention will be described. Fig. 3 shows the configuration of an optical amplifier 200 according to this embodiment.

[0032] The optical amplifier 200 has a configuration including a first multicore erbium-doped fiber (MC-EDF) 211 as a first optical waveguide means, and a second multicore erbium-doped fiber 212 as a second optical waveguide means. Here, the first multicore erbium-doped fiber 211 and the second multicore erbium-doped fiber 212 are both multicore optical fibers having a double clad structure and multiple cores doped with erbium ions, which are rare earth ions.

[0033] The optical amplifier 200 has a first pumping light generating section (first pumping light generating means) 221 and a first optical coupling section (first optical coupling means) 222. The first pumping light generating section 221 is typically a semiconductor laser, and generates first pumping light 11. The first optical coupling section 222 couples the first pumping light 11 to a first multi-core erbium-doped fiber 211, which serves as first optical waveguide means. Here, the first pumping light generating section 221 and the first optical coupling section 222 constitute first pumping light introducing means.

[0034] The optical amplifying device 200 also has a first residual pumping light coupling section (first residual pumping light coupling means) 231 and a first residual pumping light separation section (first residual pumping light separation means) 232. The first residual pumping light coupling section 231 couples the first residual pumping light 21 to the second multi-core erbium-doped fiber 212. Here, the first residual pumping light 21 is output from the first multi-core erbium-doped fiber 211 and has the wavelength component of the first pumping light. The first residual pumping light separation section 232 separates the first signal light 31 output from the first multi-core erbium-doped fiber 211 from the first residual pumping light 21. The first residual pumping light coupling section 231 and the first residual pumping light separation section 232 constitute first residual pumping light introducing means.

[0035] As described above, in the optical amplifier 200 according to this embodiment, the pump light output without being absorbed in the cores of the first multi-core erbium-doped fiber 211 is introduced into the second multi-core erbium-doped fiber 212 as the first residual pump light 21. This allows the first residual pump light 21 to be used to pump the erbium ion-doped cores of the second multi-core erbium-doped fiber 212. Therefore, the optical amplifier 200 according to this embodiment can increase the utilization efficiency of the pump light.

[0036] The optical amplifying device 200 further includes a signal light separating unit (signal light separating means) 241 and a signal light combining unit (signal light combining means) 242. The signal light separating unit 241 separates the signal light 30 into a first signal light 31 that is introduced into the first multi-core erbium-doped fiber 211 and a second signal light 32 that is introduced into the second multi-core erbium-doped fiber 212. The signal light 30 is supplied from, for example, a signal light source LS. The signal light combining unit 242 combines the first signal light output from the first multi-core erbium-doped fiber 211 and the second signal light output from the second multi-core erbium-doped fiber 212.

[0037] Here, the first signal light 31 may belong to the C-band (Conventional-band: 1530 nm to 1565 nm) among wavelength bands used in optical fiber communications, and the second signal light 32 may belong to the L-band (Long-wavelength-band: 1565 nm to 1625 nm). In this case, the first multi-core erbium-doped fiber (first optical waveguide means) 211 may be configured to have a gain in the C-band (first wavelength band). The second multi-core erbium-doped fiber (second optical waveguide means) 212 may be configured to have a gain in the L-band (second wavelength band) different from the C-band (first wavelength band). Specifically, for example, by setting the length of the first multi-core erbium-doped fiber 211 to about 8 meters (m) and the length of the second multi-core erbium-doped fiber 212 to about 55 meters (m), the above gain bands can be realized.

[0038] In such a configuration, a pumping laser is generally required for each wavelength band. However, according to the optical amplifying device 200 of this embodiment, multi-band optical amplification using a multi-core optical fiber is possible by using only one pumping laser (first pumping light generating unit 221). As a result, the optical amplifying device can be made smaller.

[0039] As described above, the optical amplifier 200 of this embodiment can increase the utilization efficiency of pumping light (hereinafter referred to as "pumping light utilization efficiency"). This effect will be specifically described. Here, an example will be described in which a single pumping laser is used to pump the first multi-core erbium-doped fiber 211 and the second multi-core erbium-doped fiber 212.

[0040] The power of the pumping light output by the pumping laser is assumed to be 100 (arbitrary unit). In a typical system, the pumping light is split into two, and one pumping light with an optical power of 50 is introduced into the first multi-core erbium-doped fiber 211 and the second multi-core erbium-doped fiber 212, respectively. Since the pumping light utilization efficiency in a cladding-pumped multi-core erbium-doped fiber is about 20%, in this case, 20% of the pumping light with an optical power of 50, i.e., pumping light with an optical power of 10, is used to pump each core. Therefore, the total pumping light utilization efficiency is 20 (= 10 + 10) / 100.

[0041] In contrast, in the optical amplifying device 200 of this embodiment, pumping light with an optical power of 100 is introduced into the first multi-core erbium-doped fiber 211. Then, pumping light with an optical power of 20, which is 20% of the pumping light, is used to pump the cores, and the remaining 80% is output from the first multi-core erbium-doped fiber 211 as first residual pumping light 21 and introduced into the second multi-core erbium-doped fiber 212. In the second multi-core erbium-doped fiber 212, residual pumping light with an optical power of 16, which is 20% of the first residual pumping light 21 with an optical power of 80, is used to pump the cores of the second multi-core erbium-doped fiber 212. Therefore, of the pumping light with an optical power of 100, pumping light with a total optical power of 36 (=20+16) is used to pump the cores, and the pumping light utilization efficiency is 36 / 100. That is, according to the optical amplifier 200 of this embodiment, it is possible to obtain an efficiency of utilization of pumping light that is 1.8 times higher than the efficiency of utilization of pumping light (20 / 100) in a conventional system.

[0042] Furthermore, the optical amplifying device 200 of this embodiment can also achieve power saving. Specifically, for example, suppose that 75 watts (W) of pumping light is required to pump the first multi-core erbium-doped fiber 211, and 25 watts (W) of pumping light is required to pump the second multi-core erbium-doped fiber 212. This is because the pumping light utilization efficiency of a multi-core erbium-doped fiber used in the L band is generally higher than that of a multi-core erbium-doped fiber used in the C band.

[0043] In this case, in a normal system, a pumping laser is used for each wavelength band, so a total pumping light power of 100 watts (75W+25W) is required.

[0044] In contrast, in the optical amplifying device 200 of this embodiment, the first pumping light generating unit 221 generates 75 watts (W) of first pumping light 11 to pump the core of the first multi-core erbium-doped fiber 211. Approximately 80% of the first pumping light 11 is not absorbed in the core of the first multi-core erbium-doped fiber 211 and is output as residual pumping light. Of this residual pumping light (e.g., 60 watts), 25 watts (W) of first residual pumping light 21 can be used to pump the core of the second multi-core erbium-doped fiber 212.

[0045] Therefore, while a conventional method requires 100 watts (W) of pumping light power, the optical amplifier device 200 of this embodiment can achieve multi-band optical amplification with 75 watts (W) of pumping light power, thereby reducing power consumption by 25%.

[0046] In the above-described embodiment, the signal light 30 is separated into the signal light 31 and the signal light 32, and the signal light 31 is introduced into the first multi-core erbium-doped fiber 211, and the signal light 32 is introduced into the second multi-core erbium-doped fiber 212. However, the present invention is not limited to this. The first multi-core erbium-doped fiber 211 and the second multi-core erbium-doped fiber 212 may be connected in tandem in series with respect to the signal light. Then, the signal light is introduced into the first multi-core erbium-doped fiber 211, and the signal light amplified by the first multi-core erbium-doped fiber 211 is introduced into the second multi-core erbium-doped fiber 212. In this case, the first multi-core erbium-doped fiber 211 and the second multi-core erbium-doped fiber 212 can be configured to have gain in the same wavelength band. In this configuration, it is desirable to insert a wavelength filter between the first multi-core erbium-doped fiber 211 and the second multi-core erbium-doped fiber 212 to remove amplified spontaneous emission (ASE).

[0047] Fig. 4 shows another configuration of an optical amplifier according to this embodiment. The optical amplifier 201 shown in Fig. 4 has a configuration that further includes a residual pumping light branching unit 233 in addition to the configuration of the optical amplifier 200 shown in Fig. 3. The residual pumping light branching unit 233 branches the first residual pumping light 21 and supplies the first residual pumping light 21 to the first optical coupling unit 222 and the first residual pumping light coupling unit 231, respectively. An optical coupler can typically be used as the residual pumping light branching unit 233. Here, the first optical coupling unit 222, the first residual pumping light separating unit 232, and the residual pumping light branching unit 233 constitute second residual pumping light introducing means.

[0048] With this configuration, in the optical amplifier 201, it becomes possible to reuse the pumping light that is not absorbed in the first multi-core erbium-doped fiber 211 and is output, for pumping the first multi-core erbium-doped fiber 211. Therefore, it is possible to further increase the pumping light utilization efficiency.

[0049] Furthermore, the optical amplifier 201 of this embodiment can achieve further power saving. This effect will be specifically explained using the example explained with reference to FIG.

[0050] Of the 75 watts (W) of first pump light 11 for pumping the first multi-core erbium-doped fiber 211, 20% (15 watts) is absorbed in the core of the first multi-core erbium-doped fiber 211. The remaining 60 watts (W) is output as first residual pump light 21. Of this residual pump light, 25 watts (W) of first residual pump light 21 is used to pump the second multi-core erbium-doped fiber 212. The remaining 35 watts (W) of residual pump light can be reused as the first residual pump light 21 for pumping the first multi-core erbium-doped fiber 211. Therefore, the power of the first pump light 11 generated by the first pump light generating unit 221 can be reduced from the initial 75 watts (W). As a result, power consumption can be further reduced.

[0051] As described above, according to the optical amplifiers 200 and 201 of the present embodiment, even when an optical amplifier equipped with a multi-core optical fiber is used in a cladding pumping system, it is possible to increase the utilization efficiency of pumping light. Furthermore, according to the optical amplifiers 200 and 201 of the present embodiment, it is possible to reduce the size and power consumption of the optical amplifier.

[0052] Third Embodiment Next, a third embodiment of the present invention will be described. Fig. 5 shows the configuration of an optical amplifier 1000 according to this embodiment. The optical amplifier 1000 according to this embodiment has a first amplifier section 1100, a second amplifier section 1200, a signal light separation section 1310, and a signal light multiplexer section 1320. Here, the first amplifier section 1100 can be used to amplify signal light in the C-band, for example, among the wavelength bands used in optical fiber communications, and the second amplifier section 1200 can be used to amplify signal light in the L-band.

[0053] The signal light separating unit 1310 separates the signal light supplied from the signal light source LS into a first signal light 31 that is introduced into the first amplifying unit 1100 and a second signal light 32 that is introduced into the second amplifying unit 1200. The signal light combining unit 1320 combines the first signal light output from the first amplifying unit 1100 with the second signal light output from the second amplifying unit 1200. Here, the first signal light 31 may belong to the C band, and the second signal light 32 may belong to the L band.

[0054] The first amplifying section 1100 has a first multi-core erbium-doped fiber 1110 as a first optical waveguide means, a first pumping light generating section (first pumping light generating means) 1121, a first optical coupling section (first optical coupling means) 1122, and a first residual pumping light separating section (first residual pumping light separating means) 1130. The first pumping light generating section 1121 is typically a semiconductor laser and generates first pumping light 11. The first optical coupling section 1122 couples the first pumping light 11 to the first multi-core erbium-doped fiber 1110. The first residual pumping light separating section 1130 separates the first signal light 31 and the first residual pumping light 21 output from the first multi-core erbium-doped fiber 1110. Here, the first residual pump light 21 is output from the first multi-core erbium-doped fiber 1110 and has the wavelength component of the first pump light.

[0055] The second amplifying section 1200 has a second multi-core erbium-doped fiber 1210 as a second optical waveguide means and a first residual pumping light coupling section (first residual pumping light coupling means) 1231. The first residual pumping light coupling section 1231 couples the first residual pumping light 21 to the second multi-core erbium-doped fiber 1210.

[0056] The first pumping light generating section 1121 and the first optical coupling section 1122 constitute a first pumping light introducing means, and the first residual pumping light separating section 1130 and the first residual pumping light coupling section 1231 constitute a first residual pumping light introducing means.

[0057] The configuration up to this point is the same as that of the optical amplifier 200 according to the second embodiment. The optical amplifier 1000 according to this embodiment further includes a second pumping light introducing section (second pumping light introducing means) and a third residual pumping light introducing section (third residual pumping light introducing means).

[0058] The second pumping light introducing section introduces the second pumping light 12, which excites a plurality of cores (second optical amplification medium) doped with erbium ions contained in the second multi-core erbium-doped fiber 1210, into the second multi-core erbium-doped fiber 1210 (second optical waveguide means). Here, the second pumping light introducing section can be configured to introduce the second pumping light 12 into the second multi-core erbium-doped fiber 1210 by a cladding pumping method.

[0059] 5, the second pumping light introducing section can be configured to include a second pumping light generating section (second pumping light generating means) 1221 and a second optical coupling section (second optical coupling means) 1222. Here, the second pumping light generating section 1221 is typically a semiconductor laser and generates the second pumping light 12. The second optical coupling section 1222 couples the second pumping light 12 to the second multi-core erbium-doped fiber 1210.

[0060] The third residual pump light introducing section introduces the second residual pump light 22, which has a wavelength component of the second pump light and is output from the second multi-core erbium-doped fiber 1210, into the first multi-core erbium-doped fiber 1110. Specifically, as shown in Fig. 5 , the third residual pump light introducing section can be configured to include a second residual pump light coupling section (second residual pump light coupling means) 1131 and a second residual pump light separating section (second residual pump light separating means) 1232. Here, the second residual pump light coupling section 1131 couples the second residual pump light 22 to the first multi-core erbium-doped fiber 1110. The second residual pump light separating section 1232 separates the second signal light 32 and the second residual pump light 22 output from the second multi-core erbium-doped fiber 1210.

[0061] As described above, in the optical amplifier 1000 according to this embodiment, the pump light output without being absorbed in the core of the first multi-core erbium-doped fiber 1110 is introduced as first residual pump light 21 into the second multi-core erbium-doped fiber 1210. Furthermore, the pump light output without being absorbed in the core of the second multi-core erbium-doped fiber 2210 is introduced as second residual pump light 22 into the first multi-core erbium-doped fiber 1110. Therefore, according to the optical amplifier 1000 according to this embodiment, it is possible to reuse each of the first pump light 11 and the second pump light 12, thereby increasing the utilization efficiency of the pump light.

[0062] In the optical amplifying device 1000 according to this embodiment, the wavelength of the first pumping light 11 generated by the first pumping light generating unit 1121 can be different from the wavelength of the second pumping light 12 generated by the second pumping light generating unit 1221. Specifically, for example, the wavelength of the first pumping light 11 is set to 976 nanometers (nm), and the wavelength of the second pumping light 12 is set to 980 nanometers (nm). In this case, it is possible to pump a multi-core erbium-doped fiber having gain in the C band or L band with either the first pumping light 11 or the second pumping light 12.

[0063] 5, the optical amplifier 1000 can be configured to include a first pumping light multiplexing section (first pumping light multiplexing means) 1140 and a second pumping light multiplexing section (second pumping light multiplexing means) 1240. Here, the first pumping light multiplexing section 1140 multiplexes the first pumping light 11 and the second residual pumping light 22. The second pumping light multiplexing section 1240 multiplexes the second pumping light 12 and the first residual pumping light 21. That is, the first pumping light introducing means and the third residual pumping light introducing means can be configured to include the first pumping light multiplexing means, and the second pumping light introducing means and the first residual pumping light introducing means can be configured to include the second pumping light multiplexing means.

[0064] Specifically, for example, the first pumping light multiplexing unit 1140 wavelength-multiplexes the first pumping light 11 having a wavelength of 976 nanometers (nm) and the second residual pumping light 22 having a wavelength of 980 nanometers (nm). The second pumping light multiplexing unit 1240 wavelength-multiplexes the second pumping light 12 having a wavelength of 980 nanometers (nm) and the first residual pumping light 21 having a wavelength of 976 nanometers (nm).

[0065] As described above, the first pumping light multiplexing unit 1140 can be configured to wavelength-multiplex the first pumping light 11 and the second residual pumping light 22 before coupling them to the first multi-core erbium-doped fiber 1110. Therefore, the first optical coupling unit 1122 and the second residual pumping light coupling unit 1131 can be made common, and a single input port can be used. Similarly, the second pumping light multiplexing unit 1240 can be configured to wavelength-multiplex the second pumping light 12 and the first residual pumping light 21 before coupling them to the second multi-core erbium-doped fiber 1210. Therefore, the first residual pumping light coupling unit 1231 and the second optical coupling unit 1222 can be made common, and a single input port can be used.

[0066] Here, at least one of the first pumping light multiplexing section (first pumping light multiplexing means) 1140 and the second pumping light multiplexing section (second pumping light multiplexing means) 1240 can be a spatially coupled multiplexing section (spatially coupled multiplexing means) equipped with a spatial optical system. By using the first pumping light multiplexing section 1140 as a spatially coupled multiplexing section, most of the components can be common to the first optical combiner 1122, the second residual pumping light combiner 1131, and the first residual pumping light separator 1130. Similarly, by using the second pumping light multiplexing section 1240 as a spatially coupled multiplexing section, most of the components can be common to the first residual pumping light combiner 1231, the second optical combiner 1222, and the second residual pumping light separator 1232. As a result, the cost of the optical amplifier 1000 can be reduced. It should be noted that the first pumping light multiplexing section 1140 and the second pumping light multiplexing section 1240 may be implemented by using a WDM (Wavelength Division Multiplexing) coupler or an arrayed waveguide grating (AWG).

[0067] 5, the optical amplifying device 1000 may be configured to include an optical isolator 1241 and an optical attenuator 1242 in the optical path of the first residual pumping light 21 from the first residual pumping light separating section 1130 to the second pumping light combining section 1240. Similarly, the optical amplifying device 1000 may be configured to include an optical isolator 1141 and an optical attenuator 1142 in the optical path of the second residual pumping light 22 from the second residual pumping light separating section 1232 to the first pumping light combining section 1140.

[0068] 5, the optical amplifying device 1000 can be configured to further include a first monitor unit (first monitor means) 1151 and a first control unit (first control means) 1152. Here, the first monitor unit 1151 monitors the optical intensity of at least one of the first signal light 31 and the first residual pump light 21 output from the first multi-core erbium-doped fiber (first optical waveguide means) 1110. Then, the first control unit 1152 controls at least one of the optical attenuator (first optical attenuation means) 1142, which controls the optical intensity of the second residual pump light 22, and the first pump light generating unit 1121, based on the monitoring result of the first monitor unit 1151. With this configuration, the optical intensity of the first signal light 31 output from the first multi-core erbium-doped fiber 1110 can be controlled.

[0069] Similarly, the optical amplifying device 1000 can be configured to further include a second monitor unit (second monitor means) 1251 and a second control unit (second control means) 1252. Here, the second monitor unit 1251 monitors the optical intensity of at least one of the second signal light 32 and the second residual pump light 22 output from the second multi-core erbium-doped fiber (second optical waveguide means) 1210. Then, the second control unit 1252 controls at least one of the optical attenuator (second optical attenuation means) 1242 that controls the optical intensity of the first residual pump light 21 and the second pump light generating unit 1221, based on the monitoring result of the second monitor unit 1251. With this configuration, the optical intensity of the second signal light 32 output from the second multi-core erbium-doped fiber 1210 can be controlled.

[0070] Next, the optical amplification method according to this embodiment will be described.

[0071] In the optical amplification method according to this embodiment, first, a first signal light is introduced into a first optical waveguide including a first optical amplification medium, and a second signal light is introduced into a second optical waveguide including a second optical amplification medium. Then, a first pumping light for pumping the first optical amplification medium is introduced into the first optical waveguide, and a first residual pumping light having a wavelength component of the first pumping light output from the first optical waveguide is introduced into the second optical waveguide. Furthermore, the first residual pumping light may also be introduced into the first optical waveguide.

[0072] The configuration up to this point is the same as that of the optical amplification method according to Embodiment 1. The optical amplification method according to this embodiment further comprises introducing second pumping light for pumping a second optical amplification medium into the second optical waveguide, and introducing second residual pumping light having a wavelength component of the second pumping light output from the second optical waveguide into the first optical waveguide.

[0073] As described above, according to the optical amplifier 1000 and the optical amplification method of this embodiment, even when an optical amplifier having a multi-core optical fiber is used in a cladding pumping system, it is possible to increase the utilization efficiency of pumping light.

[0074] [Fourth embodiment] Next, a fourth embodiment of the present invention will be described. Fig. 6 shows the configuration of an optical amplifier 2000 according to this embodiment. The optical amplifier 2000 according to this embodiment has a first amplifier section 2100, a second amplifier section 2200, a signal light demultiplexer section 2310, and a signal light multiplexer section 2320. Here, the first amplifier section 2100 can be used to amplify signal light in the C band, and the second amplifier section 2200 can be used to amplify signal light in the L band.

[0075] The signal light separating unit 2310 separates the signal light supplied from the signal light source LS into a first signal light 31 that is introduced into the first amplifying unit 2100 and a second signal light 32 that is introduced into the second amplifying unit 2200. The signal light combining unit 2320 combines the first signal light output from the first amplifying unit 2100 with the second signal light output from the second amplifying unit 2200. Here, the first signal light 31 may belong to the C-band of wavelength bands used in optical fiber communications, for example, and the second signal light 32 may belong to the L-band.

[0076] The first amplifying section 2100 has a first multi-core erbium-doped fiber 2110 as a first optical waveguide means, a first pump light generating section (first pump light generating section) 2121, a first optical coupling section (first optical coupling section) 2122, and a first residual pump light separating section (first residual pump light separating section) 2130. The second amplifying section 2200 has a second multi-core erbium-doped fiber 2210 as a second optical waveguide means, and a first residual pump light coupling section (first residual pump light coupling section) 2231.

[0077] The configuration up to this point is the same as that of the optical amplifier 200 according to the second embodiment. The optical amplifier 1000 according to this embodiment further includes a fourth residual pumping light introducing section (fourth residual pumping light introducing means) and a fifth residual pumping light introducing section (fifth residual pumping light introducing means).

[0078] The fourth residual pump light introducing section introduces the third residual pump light 23, which is output from the second multi-core erbium-doped fiber (second optical waveguide means) 2210 and has the wavelength component of the first residual pump light 21, into the first multi-core erbium-doped fiber (first optical waveguide means) 2110. Specifically, for example, as shown in Fig. 6, the fourth residual pump light introducing section may be configured to include a residual pump light separating section 2232 that separates the third residual pump light 23 from the second signal light 32, and an optical coupler 2240 that branches the third residual pump light 23 and supplies one of the branches to the first amplifying section 2100.

[0079] In this case, the first amplifying section 2100 may be configured to include a pumping light multiplexing section 2141 that multiplexes the third residual pumping light 23 with the first pumping light 11 output from the first pumping light generating section 2121, and to supply the multiplexed pumping light to the first optical coupling section 2122. Note that, as shown in Fig. 6, an optical isolator 2142 and an optical attenuator 2143 may be provided in the optical path of the third residual pumping light 23 from the optical coupler 2240 to the pumping light multiplexing section 2141.

[0080] The fifth residual pump light introducing section introduces the third residual pump light 23 into the second multi-core erbium-doped fiber (second optical waveguide means) 2210. Specifically, for example, as shown in FIG. 6, a configuration can be provided that includes a residual pump light multiplexing section 2241 that multiplexes the other third residual pump light 23 branched by the optical coupler 2240 with the first residual pump light 21 separated by the first residual pump light separating section 2130. The multiplexed residual pump light can then be supplied to the first residual pump light combining section 2231. Note that, as shown in FIG. 6, an optical isolator 2242 and an optical attenuator 2243 may be provided in the optical path of the first residual pump light 21 from the first residual pump light separating section 2130 to the residual pump light multiplexing section 2241.

[0081] As the pumping light multiplexing section 2141 and the residual pumping light multiplexing section 2241, for example, a multimode combiner or a polarized beam combiner can be used.

[0082] As described above, in the optical amplifier 2000 according to this embodiment, the pump light output without being absorbed in the core of the first multi-core erbium-doped fiber 2110 is introduced as the first residual pump light 21 into the second multi-core erbium-doped fiber 2210. Then, the third residual pump light 23 output without being absorbed in the core of the second multi-core erbium-doped fiber 2210 is introduced into the first multi-core erbium-doped fiber 2110 and is also introduced again into the second multi-core erbium-doped fiber 2210. Therefore, according to the optical amplifier 2000 according to this embodiment, the utilization efficiency of the pump light can be further increased.

[0083] 6, the optical amplifying device 2000 can be configured to further include a first monitor unit 2151 and a first control unit 2152. Here, the first monitor unit 2151 monitors the optical intensity of at least one of the first signal light 31 and the first residual pump light 21 output from the first multi-core erbium-doped fiber 2110. Then, the first control unit 2152 controls the first pump light generating unit 2121 based on the monitoring result of the first monitor unit 2151. With this configuration, it is possible to control the optical intensity of the first signal light 31 output from the first multi-core erbium-doped fiber 2110.

[0084] Similarly, the optical amplifying device 2000 can be configured to further include a second monitor unit 2251 and a second control unit 2252. Here, the second monitor unit 2251 monitors the optical intensity of at least one of the second signal light 32 and the third residual pump light 23 output from the second multi-core erbium-doped fiber 2210. Then, the second control unit 2252 controls the optical attenuator 2243, which controls the optical intensity of the first residual pump light 21, based on the monitoring result of the second monitor unit 2251. With this configuration, the optical intensity of the second signal light 32 output from the second multi-core erbium-doped fiber 2210 can be controlled.

[0085] Next, the optical amplification method according to this embodiment will be described.

[0086] In the optical amplification method according to this embodiment, first, a first signal light is introduced into a first optical waveguide including a first optical amplification medium, and a second signal light is introduced into a second optical waveguide including a second optical amplification medium. Then, a first pumping light for pumping the first optical amplification medium is introduced into the first optical waveguide, and a first residual pumping light having a wavelength component of the first pumping light output from the first optical waveguide is introduced into the second optical waveguide. Furthermore, the first residual pumping light may also be introduced into the first optical waveguide.

[0087] The configuration up to this point is the same as that of the optical amplification method according to the first embodiment. In the optical amplification method according to this embodiment, the third residual pumping light output from the second optical waveguide and having a wavelength component of the first residual pumping light is introduced into the first optical waveguide. In this case, the third residual pumping light may also be introduced into the second optical waveguide.

[0088] As described above, according to the optical amplifier 2000 and the optical amplification method of this embodiment, even when an optical amplifier equipped with a multi-core optical fiber is used in a cladding pumping system, it is possible to increase the utilization efficiency of pumping light.

[0089] A part or all of the above-described embodiments can be described as, but not limited to, the following supplementary notes.

[0090] (Supplementary Note 1) An optical amplifier comprising: a first optical waveguide means including a first optical amplification medium; a second optical waveguide means including a second optical amplification medium; a first pumping light introducing means for introducing first pumping light for exciting the first optical amplification medium into the first optical waveguide means; and a first residual pumping light introducing means for introducing first residual pumping light having a wavelength component of the first pumping light output from the first optical waveguide means into the second optical waveguide means.

[0091] (Supplementary Note 2) The optical amplifying device according to Supplementary Note 1, further comprising second residual pumping light introducing means for introducing the first residual pumping light into the first optical waveguide means.

[0092] (Appendix 3) The optical amplifier according to appendix 1 or 2, further comprising: a second pumping light introducing means for introducing second pumping light for exciting the second optical amplification medium into the second optical waveguide means; and a third residual pumping light introducing means for introducing second residual pumping light having a wavelength component of the second pumping light output from the second optical waveguide means into the first optical waveguide means.

[0093] (Appendix 4) The optical amplification device according to appendix 3, wherein the first pumping light introducing means and the third residual pumping light introducing means each include a first pumping light multiplexing means for multiplexing the first pumping light and the second residual pumping light, and the second pumping light introducing means and the first residual pumping light introducing means each include a second pumping light multiplexing means for multiplexing the second pumping light and the first residual pumping light.

[0094] (Appendix 5) The optical amplifier according to appendix 1 or 2, further comprising a fourth residual pumping light introducing means for introducing third residual pumping light, which is output from the second optical waveguide means and has a wavelength component of the first residual pumping light, into the first optical waveguide means.

[0095] (Appendix 6) The optical amplifying device according to appendix 5, further comprising a fifth residual pumping light introducing means for introducing the third residual pumping light into the second optical waveguide means.

[0096] (Supplementary Note 7) The optical amplifying device according to any one of Supplementary Notes 1 to 6, further comprising: a signal light separating means for separating a signal light into a first signal light introduced into the first optical waveguide means and a second signal light introduced into the second optical waveguide means; and a signal light combining means for combining the first signal light output from the first optical waveguide means and the second signal light output from the second optical waveguide means.

[0097] (Appendix 8) An optical amplification method including: introducing a first signal light into a first optical waveguide including a first optical amplification medium; introducing a second signal light into a second optical waveguide including a second optical amplification medium; introducing a first pumping light for pumping the first optical amplification medium into the first optical waveguide; and introducing a first residual pumping light having a wavelength component of the first pumping light output from the first optical waveguide into the second optical waveguide.

[0098] (Appendix 9) The optical amplification method according to appendix 8, wherein the first residual pump light is introduced into the first optical waveguide.

[0099] (Appendix 10) An optical amplification method according to appendix 8 or 9, wherein second pumping light for pumping the second optical amplification medium is introduced into the second optical waveguide, and second residual pumping light having a wavelength component of the second pumping light output from the second optical waveguide is introduced into the first optical waveguide.

[0100] (Appendix 11) The optical amplifying device according to appendix 4, wherein at least one of the first pumping light multiplexing means and the second pumping light multiplexing means is a spatial coupling type multiplexing means equipped with a spatial optical system.

[0101] (Appendix 12) The optical amplifier according to any one of Appendices 3, 4, and 11, wherein the wavelength of the first pumping light is different from the wavelength of the second pumping light.

[0102] (Appendix 13) The optical amplifier according to any one of Appendices 3, 4, 11, and 12, wherein the first pumping light introducing means comprises first pumping light generating means for generating the first pumping light and first optical coupling means for coupling the first pumping light to the first optical waveguide means, and the first residual pumping light introducing means comprises first residual pumping light coupling means for coupling the first residual pumping light to the second optical waveguide means, and first residual pumping light separating means for separating the first signal light output from the first optical waveguide means from the first residual pumping light.

[0103] (Appendix 14) The optical amplifier according to any one of Appendices 3, 4, 11, and 12, wherein the second pumping light introducing means comprises second pumping light generating means for generating the second pumping light and second optical coupling means for coupling the second pumping light to the second optical waveguide means, and the third residual pumping light introducing means comprises second residual pumping light coupling means for coupling the second residual pumping light to the first optical waveguide means, and second residual pumping light separating means for separating the second signal light output from the second optical waveguide means from the second residual pumping light.

[0104] (Appendix 15) An optical amplifier according to appendix 13, comprising: a first monitor means for monitoring the optical intensity of at least one of the first signal light and the first residual pump light output from the first optical waveguide means; and a first control means for controlling at least one of a first optical attenuator means for controlling the optical intensity of the second residual pump light and the first pump light generator means based on the monitoring result of the first monitor means.

[0105] (Appendix 16) An optical amplifying device according to appendix 14, comprising: second monitoring means for monitoring the optical intensity of at least one of the second signal light and the second residual pump light output from the second optical waveguide means; and second control means for controlling at least one of second optical attenuation means for controlling the optical intensity of the first residual pump light and the second pump light generation means based on the monitoring result of the second monitoring means.

[0106] (Supplementary Note 17) The optical amplifier according to any one of Supplementary Notes 1 to 7 and 11 to 16, wherein the first optical waveguide means has a gain in a first wavelength band, and the second optical waveguide means has a gain in a second wavelength band different from the first wavelength band.

[0107] (Appendix 18) An optical amplifier according to any one of Appendices 1 to 7 and 11 to 17, wherein the first optical amplification medium and the second optical amplification medium each comprise a plurality of cores doped with rare earth ions, the first optical waveguide means and the second optical waveguide means each comprise a multi-core optical fiber provided with a plurality of optical transmission paths each having a double clad structure and the plurality of cores, and the first pumping light introducing means introduces the first pumping light into the first optical waveguide means by a clad pumping method.

[0108] (Appendix 19) The optical amplification method according to appendix 8 or 9, wherein third residual pumping light output from the second optical waveguide and having a wavelength component of the first residual pumping light is introduced into the first optical waveguide.

[0109] (Appendix 20) The optical amplification method according to appendix 19, wherein the third residual pump light is introduced into the second optical waveguide.

[0110] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0111] This application claims priority based on Japanese Patent Application No. 2021-030665, filed on February 26, 2021, the disclosure of which is incorporated herein in its entirety. [Explanation of symbols]

[0112] 100, 101, 200, 201, 1000, 2000 Optical amplifier 111 First optical waveguide 112 Second optical waveguide 120 First excitation light introduction section 131 First residual excitation light introduction section 132 Second residual excitation light introduction section 211, 1110, 2110 First multi-core erbium-doped fiber 212, 1210, 2210 Second multi-core erbium-doped fiber 221, 1121, 2121 First pump light generating unit 222, 1122, 2122 First optical coupling section 231, 1231, 2231 First residual pump light coupling section 232, 1130, 2130 First residual pump light separating unit 233 Residual pumping light branching section 241, 1310, 2310 Signal light separation section 242, 1320, 2320 signal optical multiplexer 1100, 2100 First amplifier 1131 Second residual pump light coupling section 1140 First pumping light multiplexer 1141, 1241, 2142, 2242 Optical Isolators 1142, 1242, 2143, 2243 Optical Attenuators 1151, 2151 First monitor section 1152, 2152 First control section 1200, 2200 Second amplifier 1221 Second excitation light generation unit 1222 Second optical coupling section 1232 Second residual pump light separator 1240 Second pumping light multiplexer 1251, 2251 Second monitor section 1252, 2252 Second control section 2141 Pumping light multiplexer 2232 Residual pump light separator 2240 Optical Coupler 2241 Residual pumping light multiplexer 11 First excitation light 12 Second excitation light 21 First residual excitation light 22 Second residual excitation light 23 Third residual excitation light 30 Signal Light 31 First signal light 32 Second signal light

Claims

1. a first optical waveguide means including a first optical amplifying medium; a second optical waveguide means including a second optical amplifying medium; a first pumping light introducing means for introducing first pumping light for exciting the first optical amplifying medium into the first optical waveguide means; a first residual pumping light introducing means for introducing output light from the first optical waveguide means, in which a wavelength component of the first pumping light remains, into the second optical waveguide means; Including, The first optical waveguide means and the second optical waveguide means are Can be connected to a common signal light source, An optical amplifier device comprising a multi-core optical fiber including a plurality of cores and a double clad structure having a plurality of clads on the inside and outside.

2. The excitation method used by the first excitation light introducing means is 2. The optical amplifier according to claim 1, further comprising a clad pumping system in which pumping light is incident on the outer clad of the double clad structure.

3. The second optical amplifying medium is pumped by the wavelength component of the first pumping light.

3. The optical amplifier according to claim 1.

4. the plurality of cores included in the multi-core optical fiber are doped with ionized rare earth elements; 4. The optical amplifier according to claim 1, wherein the rare earth element includes at least one of erbium, thulium, and ytterbium.

5. 4. The optical amplifying device according to claim 1, wherein the first optical waveguide means and the second optical waveguide means each include an erbium-doped multi-core optical fiber.

6. a signal light separating means for separating a signal light into a first signal light introduced into the first optical waveguide means and a second signal light introduced into the second optical waveguide means; a signal light multiplexing means for multiplexing a signal light component output from the first optical waveguide means and a signal light component output from the second optical waveguide means, The signal light separating means is connected to the common signal light source.

6. An optical amplifier according to claim 1.

7. the first signal light and the second signal light have different wavelength bands, 7. The optical amplifier according to claim 6, wherein the optical amplifier is applicable to multi-band wavelength division multiplexing transmission.

8. the first signal light belongs to a C band (conventional band), 8. The optical amplifying device according to claim 6, wherein the second signal light belongs to an L band (Long wavelength band).

9. 9. The optical amplifying device according to claim 8, wherein the multi-core optical fiber included in the second optical waveguide means is longer than the multi-core optical fiber included in the first optical waveguide means.

10. introducing first pumping light into a multi-core optical fiber including a first optical amplification medium, the first pumping light exciting the first optical amplification medium; output light from the first optical amplification medium, in which the wavelength component of the first pump light remains, is introduced into a multi-core optical fiber including a second optical amplification medium; Each of the multi-core optical fibers comprises: Can be connected to a common signal light source, An optical amplification method including a plurality of cores and a double clad structure having a plurality of clads on the inside and outside.

Images