Multi-core fiber amplifier and optical amplification method

Abstract

To improve an efficiency of a multi-core optical amplifier that amplifies light in a plurality of wavelength bands using an excitation light source of a single wavelength.SOLUTION: A multi-core fiber amplifier includes: a first optical multiplexer that couples an excitation light of a single wavelength used for amplification of signal light with first signal light that is signal light in a first wavelength band and a second signal light that is signal light in a second wavelength band, and outputs the combined light; a first amplifier that includes a multi-core fiber to which a rare earth element is added, receives output light from the first optical multiplexer, amplifies at least the first signal light, and outputs the amplified light; a first optical demultiplexer that demultiplexes the output light from a first amplifier into the first signal light and the second signal light and the excitation light, and outputs the demultiplexed light; a second amplifier that includes the multi-core fiber to which the rare earth element is added, receives the second signal light and the excitation light output from the first optical demultiplexer, amplifies the input second signal light, and outputs them; and a second optical multiplexer that multiplexes the first signal light output from the first optical demultiplexer and the second signal light output from the second amplifier.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a multi-core fiber amplifier and an optical amplification method. [Background technology]

[0002] The practical application of spatial optical multiplexing transmission systems using multicore fiber (MCF) is progressing. MCF has multiple cores in a single optical fiber. Therefore, by using MCF instead of single-core fiber (SCF), it is possible to expand the transmission capacity of optical transmission systems. MCF amplifiers (multicore fiber amplifiers) that use MCF as the pumping fiber are also known. MCFs with erbium (Er) doped in the core are also called MC-EDF (multicore erbium-doped fiber).

[0003] Wavelength division multiplexed signal light is usually used for the signal light transmitted by MCF. The bands of wavelength division multiplexed signal light are known as S-band, C-band, and L-band. The S-band is approximately 1460-1530 nm, the C-band is approximately 1530-1565 nm, and the L-band is approximately 1565-1625 nm. Wavelength division multiplexed signal light is also called WDM (wavelength division multiplexing) light.

[0004] In relation to the present disclosure, Patent Document 1 discloses a multi-core EDFA (MC-EDFA) in which MC-EDFs are arranged in parallel. EDFA stands for Er-doped fiber amplifier. FIG. 10 is a diagram showing the configuration of a multi-core fiber amplifier 900 described in Patent Document 1. The multi-core fiber amplifier 900 includes multi-core EDFs 901 and 902, and amplifies C-band signal light and L-band signal light output from a signal source 910 for each wavelength band. An optical demultiplexer 911 demultiplexes the signal light (C+L) input from the MCF transmission line into C-band signal light (C) and L-band signal light (L). The C-band signal light is multiplexed with pump light (p) output from a pump light source 950 by an optical multiplexer 921, and is amplified in the multi-core EDF 901. An optical demultiplexer 912 demultiplexes the C-band signal light and pump light (residual pump light) output from the multi-core EDF 901. The demultiplexed residual pump light is multiplexed with the L-band signal light in the optical multiplexer 923 and input to the multi-core EDF 902. The multi-core EDF 902 amplifies the L-band signal light using the residual pump light. The residual pump light is absorbed in the multi-core EDF 902. The optical multiplexer 922 multiplexes the amplified C-band signal light and L-band signal light, and outputs the multiplexed signal to the MCF transmission line 932. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2022 / 181294 Summary of the Invention [Problem to be solved by the invention]

[0006] 10 pumps a multi-core EDF 902 using residual pump light output from a multi-core EDF 901. Therefore, the multi-core fiber amplifier 900 can pump two MC-EDFs 901 and 902 arranged in parallel using one pump light source.

[0007] However, the multi-core fiber amplifier 900 requires an optical demultiplexer 912 and an optical multiplexer 923 for demultiplexing and multiplexing the residual pump light on the output side of the multi-core EDF 901 and the input side of the multi-core EDF 902 in order to supply the residual pump light to the multi-core EDF 902. As a result, there is an increase in loss of the pump light and signal light passing through these, which causes a problem of a decrease in the efficiency (amplification efficiency or power efficiency) of the multi-core fiber amplifier 900.

[0008] (Object of the invention) The present disclosure provides a technique for improving the efficiency of a multi-core optical amplifier that amplifies light in multiple wavelength bands using a pump light source with a single wavelength. [Means for solving the problem]

[0009] A multi-core fiber amplifier according to the present disclosure includes: a first optical multiplexing means for combining pump light of a single wavelength used for amplifying signal light with first signal light, which is the signal light in a first wavelength band, and second signal light, which is the signal light in a second wavelength band, and outputting the combined signal; a first amplifying means including a multi-core fiber doped with a rare earth element, receiving the output light from the first optical multiplexing means and amplifying and outputting at least the first signal light; a first optical demultiplexing means for demultiplexing output light from the first amplifying means into the first signal light, the second signal light, and the pump light, and outputting the demultiplexed light; a second amplifying means including a multi-core fiber doped with a rare earth element, receiving the second signal light and the pumping light output from the first optical demultiplexing means, amplifying the input second signal light, and outputting the amplified second signal light; a second optical multiplexing means for multiplexing the first signal light output from the first optical demultiplexing means and the second signal light output from the second amplifying means; Equipped with.

[0010] An optical amplification method according to the present disclosure includes: combining pump light of a single wavelength used for amplifying signal light with first signal light, which is the signal light in a first wavelength band, and second signal light, which is the signal light in a second wavelength band, by a first optical combining means, and outputting the combined signal; inputting the output light from the first optical multiplexing means into a first amplifying means including a multi-core fiber doped with a rare earth element, and amplifying and outputting at least the first signal light; outputting the output light from the first amplifying means by a first optical demultiplexing means into the first signal light, the second signal light, and the pumping light; inputting the second signal light and the pumping light output from the first optical demultiplexing means to a second amplifying means including a multi-core fiber doped with a rare earth element, and amplifying and outputting the input second signal light; the first signal light output from the first optical demultiplexing means and the second signal light output from the second amplifying means are multiplexed by a second optical multiplexing means; Includes instructions. [Effects of the Invention]

[0011] The multi-core fiber amplifier etc. according to the present disclosure makes it possible to improve the efficiency of a multi-core optical amplifier that amplifies light in multiple wavelength bands using a pump light source with a single wavelength. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a multi-core fiber amplifier. [Figure 2] FIG. 1 is a diagram illustrating an example of the configuration of a multi-core fiber amplifier. [Figure 3] 1 is a diagram illustrating an example of the configuration of an optical demultiplexer and an excitation light regulator; [Figure 4] 1 is a diagram illustrating an example of the configuration of an optical demultiplexer and an excitation light regulator; [Figure 5] FIG. 1 is a diagram illustrating an example of the configuration of a multi-core fiber amplifier. [Figure 6] FIG. 1 is a diagram illustrating an example of the configuration of a multi-core fiber amplifier. [Figure 7] FIG. 1 is a diagram illustrating an example of the configuration of a multi-core fiber amplifier. [Figure 8] FIG. 1 is a diagram illustrating an example of the configuration of a multi-core fiber amplifier. [Figure 9] 1 is a flowchart illustrating an example of an optical amplification method. [Figure 10] FIG. 1 is a diagram showing the configuration of a multi-core fiber amplifier described in Patent Document 1. DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments of the present disclosure will be described below with reference to the drawings. Arrows shown in the drawings are intended to illustrate the direction of signals, etc., and are not intended to limit the nature of the signals, such as their direction and magnitude. Furthermore, intersections of paths indicated by solid lines do not represent the connection of paths unless otherwise specified. In the embodiments and drawings, elements already mentioned are given the same reference numerals, and duplicate explanations may be omitted.

[0014] (First embodiment) 1 is a diagram showing an example of the configuration of a multi-core fiber amplifier 100. The multi-core fiber amplifier 100 includes multi-core EDFs 101 and 102, optical multiplexers 111 and 112, an optical demultiplexer 121, and a pumping light source 150. MCF transmission lines 161 and 162 are connected to the multi-core fiber amplifier 100. The MCF transmission lines 161 and 162 are optical transmission lines made of MCF. The multi-core fiber amplifier 100 amplifies signal light input from each core of the MCF transmission line 161 and outputs the amplified signal light to the MCF transmission line 162.

[0015] Multi-core EDFs (multi-core Er-doped fiber, MC-EDF) 101 and 102 are both amplification media that amplify input light using pump light. The multi-core EDFs 101 and 102 are multi-core erbium-doped fibers (MC-EDF) in which each core of the multi-core fiber is doped with erbium, a rare earth element. The multi-core EDFs 101 and 102 can be called a first amplifying means and a second amplifying means, respectively.

[0016] Pump light and signal light are input to the optical multiplexer 111. The pump light can be a single-wavelength light in the 0.98 μm band generated by a pump light source 150. The signal light is generated by a signal source 160, such as an optical transmitter, and propagates through an MCF transmission line 161. The signal light is wavelength-multiplexed light obtained by multiplexing a first signal light, which is light in a first wavelength band, with a second signal light, which is light in a second wavelength band that does not overlap with the first wavelength band. The optical multiplexer 111 combines the pump light and the signal light and inputs the combined light to the multi-core EDF 101. The multi-core EDF 101 is mainly used to amplify the first signal light. The multi-core EDF 102 is mainly used to amplify the second signal light. In this and subsequent embodiments, the first wavelength band can be the C band, and the second wavelength band can be the L band. As a pumping method for the multi-core EDFs 101 and 102, cladding pumping can be used.

[0017] 1 and the following figures, graphs are provided where appropriate to clearly show the wavelength and intensity of signal light, with the first wavelength band designated "1" and the second wavelength band designated "2," with the wavelength designated on the horizontal axis and the optical intensity designated on the vertical axis. However, in each graph, the optical intensity on the vertical axis exemplifies the relative intensity difference between wavelength bands (e.g., C-band and L-band) within the same graph, and does not strictly represent the difference in optical intensity between different graphs.

[0018] The optical demultiplexer 121 is disposed between the multi-core EDF 101 and the multi-core EDF 102. The optical demultiplexer 121 demultiplexes the light output from the multi-core EDF 101 according to wavelength bands. One of the demultiplexed lights contains pump light and second signal light. The other demultiplexed light contains first signal light. One of the demultiplexed lights is output to the multi-core EDF 102. The other demultiplexed light is output to the optical multiplexer 112. The optical demultiplexer 121 can be an optical filter that transmits the pump light and second signal light and reflects the first signal light. The optical filter may be an optical bandpass filter. In this case, the wavelength band that the optical filter transmits and the wavelength band that it reflects may be reversed.

[0019] The optical multiplexer 112 multiplexes the other light (first signal light) demultiplexed by the optical demultiplexer 121 with the second signal light output from the multi-core EDF 102, and outputs the multiplexed light.

[0020] The multi-core fiber amplifier 100 having such a configuration can improve the efficiency of a multi-core optical amplifier that amplifies light in multiple wavelength bands (i.e., multiple frequency bands) using a single-wavelength pumping light source 150. The reason for this is as follows.

[0021] In the multi-core fiber amplifier 100, the multi-core EDF 101 and the multi-core EDF 102 are connected in series via an optical demultiplexer 121. Therefore, the multi-core EDFs 101 and 102 can be pumped using only pump light of a single wavelength output from a single pump light source. This configuration eliminates the need for optical components (e.g., the optical demultiplexer 912 and the optical multiplexer 923 shown in FIG. 10 ) for injecting pump light into the multi-core EDF 102, thereby improving the amplification efficiency of the multi-core EDF 102. Furthermore, the first signal light amplified in the multi-core EDF 101 is demultiplexed in the optical demultiplexer 121, and is output from the multi-core fiber amplifier 100 without suffering unnecessary loss in the multi-core EDF 102. Therefore, the multi-core fiber amplifier 100 can improve the power conversion efficiency (PCE) of the entire optical amplifier when amplifying the first signal light and the second signal light.

[0022] The pump light absorption rate in the multi-core EDF 101 may be equal to or lower than that in the multi-core EDF 102. By placing an MC-EDF with a relatively low pump light absorption rate in the upstream stage, the pump light power input to the downstream MC-EDF can be increased, thereby expanding the operating conditions of the downstream MC-EDF.

[0023] (Other Configurations of the Multicore Fiber Amplifier 100) The effect of the multi-core fiber amplifier 100 described using Fig. 1 can also be obtained by the following configuration. The numbers in parentheses are reference symbols of Fig. 1. The multi-core fiber amplifier 100 includes a first amplifying means (101), a second amplifying means (102), a first optical multiplexing means (111), a first optical demultiplexing means (121), and a second optical multiplexing means (112).

[0024] Both the first amplifying means and the second amplifying means include a multicore fiber doped with a rare earth element. The first optical combining means combines the pump light with the first signal light and the second signal light and outputs the combined light. The output light from the first optical combining means is input to the first amplifying means. The first optical amplifying means inputs the output light from the first optical combining means and amplifies and outputs at least the first signal light. The first optical demultiplexing means demultiplexes the light output from the first amplifying means into "first signal light" and "second signal light and pump light." The second signal light and pump light demultiplexed by the first optical demultiplexing means are input to the second amplifying means. The second optical amplifying means inputs the second signal light and pump light output from the first optical demultiplexing means and amplifies and outputs the input second signal light. The second optical multiplexing means multiplexes the first signal light demultiplexed by the first optical demultiplexing means and the second signal light output from the second amplifying means. Note that in this configuration, the signal source 160 and the pumping light source (pumping light generating means) 150 are not essential.

[0025] Fig. 9 is a flowchart showing an example of an optical amplification method in the above-described configuration. That is, Fig. 9 is an example of an optical amplification method used in a multi-core fiber amplifier including a first amplifying means including a multi-core fiber and a second amplifying means including a multi-core fiber. The optical amplification method includes the following steps: Pumping light, which is light of a single wavelength, is combined with first signal light and second signal light (step S01 in Fig. 9), and the combined light is amplified in the first amplifying means (step S02). Then, the light output from the first amplifying means is demultiplexed into "first signal light" and "second signal light and pumping light" (step S03). Furthermore, the demultiplexed second signal light is amplified by the second amplifying means (step S04), and the first signal light demultiplexed in step S03 is combined with the second signal light output from the second amplifying means (step S05).

[0026] (Modification of the first embodiment) 2 is a block diagram showing a configuration example of a multi-core fiber amplifier 100A. The multi-core fiber amplifier 100A differs from the multi-core fiber amplifier 100 in that it includes a pumping light adjuster 130. The pumping light adjuster 130 is disposed between the optical demultiplexer 121 and the multi-core EDF 102. The pumping light adjuster 130 is an example of a pumping light adjusting means that adjusts the power of the pumping light input to the multi-core EDF 102. The pumping light adjuster 130 and the optical demultiplexer 121 may be configured as an integrated unit.

[0027] The multi-core fiber amplifier 100A can adjust the pump light intensity for each wavelength band of the signal light by including the pump light adjuster 130. For example, the multi-core fiber amplifier 100A can amplify the second signal light in the multi-core EDF 102 under more suitable conditions by adjusting the intensity of the pump light input to the multi-core EDF 102 using the pump light adjuster 130.

[0028] 3 is a diagram showing a configuration example of the optical demultiplexer 121 and the pumping light adjuster 130. The optical demultiplexer 121 includes an optical filter 171. The optical filter 171 demultiplexes the light input from the multi-core EDF 101 into pumping light (0.98 μm band), light in the second wavelength band (L band), and light in the first wavelength band (C band). The pumping light and second signal light are output to the multi-core EDF 102 via the pumping light adjuster 130.

[0029] The pump light adjuster 130 includes optical filters 131 and 132, and a variable optical attenuator (VOA) 133. The optical filter 131 demultiplexes the light input from the optical demultiplexer 121 into pump light and second signal light. The second signal light passes through the optical filters 131 and 132 and is output to the multi-core EDF 102. The pump light is output from the optical filter 131 to the variable optical attenuator 133. The variable optical attenuator 133 attenuates the power of the input pump light. The pump light output from the variable optical attenuator 133 is multiplexed with the second signal light in the optical filter 132 and input to the multi-core EDF 102. The attenuation amount of the pump light in the variable optical attenuator 133 may be controlled by an electrical signal from outside the multi-core fiber amplifier 100A.

[0030] FIG. 4 illustrates an example of the configuration of the optical demultiplexer 121 and the pumping light conditioner 130A. The pumping light conditioner 130A can be used instead of the pumping light conditioner 130. The pumping light conditioner 130A includes optical filters 131 and 132, a variable optical attenuator 133, and an optical coupler 134. The optical coupler 134 couples the light input from the optical demultiplexer 121 with the pumping light. By including the optical coupler 134, the pumping light conditioner 130A can increase the power of the pumping light input to the multi-core EDF 102. For example, when the power of the pumping light that pumps the multi-core EDF 102 is insufficient, the pumping light conditioner 130A can increase the power of the pumping light input to the multi-core EDF 102 by adding pumping light from an external source. The optical coupler 134 is, for example, an optical directional coupler or a polarization combining coupler, and can be called a third optical multiplexing means.

[0031] In this way, the pump light conditioners 130 and 130A can be used to adjust the power of the pump light output to the multi-core EDF connected in the subsequent stage. Also in the following embodiments, by disposing the pump light conditioner 130 between the MC-EDFs, it is possible to adjust the power of the pump light input to the MC-EDF connected in the subsequent stage of the pump light conditioner 130.

[0032] (Second embodiment) 5 is a diagram showing an example of the configuration of a multi-core fiber amplifier 200. The multi-core fiber amplifier 200 differs from the multi-core fiber amplifier 100 in that it includes an optical demultiplexer 122 and an excitation light coupler 211.

[0033] The pump light and the second signal light output from the multi-core EDF 102 are input to the optical demultiplexer 122. The optical demultiplexer 122 demultiplexes the input light into the pump light and the second signal light. The optical demultiplexer 122 is, for example, an optical filter. The second signal light demultiplexed in the optical demultiplexer 122 is output to the optical multiplexer 112. The optical multiplexer 112 multiplexes the first signal light output from the optical demultiplexer 121 and the second signal light output from the optical demultiplexer 122, and outputs the combined light to the MCF transmission line 162. On the other hand, the pump light demultiplexed in the optical demultiplexer 122 is output to the pump light coupler 211. The optical demultiplexer 122 can be called a second optical demultiplexing means, which demultiplexes the second signal light and pump light output from the multi-core EDF 102 and inputs the demultiplexed second signal light to the second optical multiplexing means.

[0034] The pumping light coupler 211 couples the pumping light demultiplexed in the optical demultiplexer 122 with the pumping light output from the pumping light source 150. The pumping light combined in the pumping light coupler 211 is output to the optical multiplexer 111. The pumping light coupler 211 is, for example, an optical directional coupler or a polarization multiplexing coupler, but is not limited to these. The optical multiplexer 111 combines the pumping light and signal light combined in the pumping light coupler 211 and outputs the combined light to the multi-core EDF 101. The pumping light coupler 211 can be called pumping light combining means, which combines the pumping light demultiplexed in the optical demultiplexer 122 with the pumping light output from the pumping light source 150.

[0035] The optical demultiplexer 122 and the pump light combiner 211 are not essential for the operation of the multi-core fiber amplifier 200. However, by providing these components, the multi-core fiber amplifier 200 can efficiently utilize the pump light. This is because the pump light (residual pump light) output from the multi-core EDF 102 can be reused (recycled) by inputting it back into the multi-core EDF 101.

[0036] (Third embodiment) 6 is a diagram showing a configuration example of a multi-core fiber amplifier 300. The multi-core fiber amplifier 300 differs from the multi-core fiber amplifier 100 in that it includes a configuration for amplifying third signal light, which is signal light in a third wavelength band. The third wavelength band is, for example, the S-band. Specifically, the multi-core fiber amplifier 300 includes a multi-core EDF 103 and an optical demultiplexer 123.

[0037] The multi-core EDF 103 and the optical demultiplexer 123 are arranged in series between the optical multiplexer 111 and the multi-core EDF 101. The multi-core EDF 103 is arranged between the optical multiplexer 111 and the optical demultiplexer 123, and the optical demultiplexer 123 is arranged between the multi-core EDF 103 and the multi-core EDF 101.

[0038] Pump light and signal light are input to the optical multiplexer 111. The pump light is light with a single wavelength, for example, in the 0.98 μm band. In this embodiment, the signal light is light obtained by wavelength-multiplexing first signal light, second signal light, and third signal light. The optical multiplexer 111 combines the pump light and the signal light and inputs the combined light to the multi-core EDF 103. The pump light may be generated in a pump light source 150.

[0039] The multi-core EDF 103 is an amplification medium and amplifies input light using pump light. The multi-core EDF 103 shown in FIG. 6 is an MC-EDF in which each core of a multi-core fiber is doped with erbium, and is arranged in front of the multi-core EDF 101. The multi-core EDF 103 can be called a third amplification means having the function of amplifying signal light using pump light. The multi-core EDF 103 mainly amplifies the third signal light. The pump light absorption rate in the multi-core EDF 103 may be equal to or lower than that in the multi-core EDF 101. By not increasing the pump light absorption rate of the front-stage MC-EDF (multi-core EDF 103) (for example, by making it equal to or lower than the pump light absorption rate of the rear-stage MC-EDF), the pump light power input to the rear-stage multi-core EDFs 101 and 102 can be increased.

[0040] The optical demultiplexer 123 is disposed between the multi-core EDF 103 and the multi-core EDF 101. The optical demultiplexer 123 receives the light output from the multi-core EDF 103. The optical demultiplexer 123 demultiplexes the input light into two. One of the demultiplexed lights includes a first signal light, a second signal light, and a pump light. The other demultiplexed light includes a third signal light. One of the demultiplexed lights is output to the multi-core EDF 101. The other demultiplexed light is output to the optical multiplexer 112. The optical demultiplexer 123 can be an optical filter that transmits the pump light, the first and second signal lights, and reflects the third signal light. The optical filter may be an optical bandpass filter. The wavelength band that the optical filter transmits and the wavelength band that it reflects may be reversed. The optical demultiplexer 123 can be called a third optical demultiplexing means that demultiplexes the light output from the multi-core EDF 103 into "light including the first signal light, the second signal light, and the pump light" and "third signal light included in the signal light." Note that the configuration and function of the stages subsequent to the multi-core EDF 101 are the same as those in the first embodiment, and therefore will not be described here.

[0041] In this embodiment, the optical multiplexer 112 multiplexes the first signal light output from the optical demultiplexer 121, the second signal light output from the multi-core EDF 102, and the third signal light output from the optical demultiplexer 123. Then, the optical multiplexer 112 outputs the multiplexed light to the MCF transmission line 162.

[0042] The multi-core fiber amplifier 300 having such a configuration can improve the efficiency of a multi-core optical amplifier that amplifies multiple signal lights using a single-wavelength pump light source 150. The multi-core fiber amplifier 300 includes three MC-EDFs, and therefore can amplify signal lights in three different wavelength bands using amplification media with lengths suitable for each. Furthermore, by setting the parameters (e.g., lengths) of the multi-core EDFs 101 to 103 to be suitable for amplifying the C-band, L-band, and S-band, respectively, the multi-core fiber amplifier 300 can efficiently amplify signal lights in three wavelength bands using one pump light with a single wavelength.

[0043] (First modified example of the third embodiment) Fig. 7 is a diagram showing a configuration example of a multi-core fiber amplifier 300A. The multi-core fiber amplifier 300A differs from the multi-core fiber amplifier 300 shown in Fig. 6 in that it includes pumping light adjusters 130 and 135. The configuration of the pumping light adjuster 135 is basically the same as that of the pumping light adjuster 130, and it has a function of adjusting only the power of the pumping light. However, in the pumping light adjuster 135, the transmission bands of the optical filters 131 and 132 are set so that the light of the first wavelength band and the light of the second wavelength band propagate through an optical path that does not pass through the variable optical attenuator 133. Furthermore, in the multi-core fiber amplifier 300A, the pumping light adjusters 130 and 135 may have the configuration of the pumping light adjuster 130A that can add pumping light.

[0044] The multi-core fiber amplifier 300A having such a configuration can adjust the pump light power at each input of the multi-core EDF 101 and the multi-core EDF 102. As a result, the multi-core fiber amplifier 300A can independently control the amplification characteristics of the multi-core EDFs 102 and 103.

[0045] (Second modified example of the third embodiment) Fig. 8 is a diagram showing a configuration example of a multi-core fiber amplifier 300B. The multi-core fiber amplifier 300B differs from the multi-core fiber amplifier 300 shown in Fig. 6 in that it includes an optical demultiplexer 122 and an excitation light coupler 211. The configurations of the optical demultiplexer 122 and the excitation light coupler 211 are similar to those of the multi-core fiber amplifier 200 described in Fig. 5. In other words, the multi-core fiber amplifier 300B is obtained by applying the configuration of the multi-core fiber amplifier 200 to the multi-core fiber amplifier 300.

[0046] In the multi-core fiber amplifier 300B, the pump light and second signal light output from the multi-core EDF 102 are input to the optical demultiplexer 122. The optical demultiplexer 122 demultiplexes the input light into the pump light and the second signal light, and outputs the second signal light to the optical multiplexer 112. The optical demultiplexer 122 also outputs the pump light to the pump light coupler 211.

[0047] The pumping light coupler 211 combines the pumping light separated in the optical demultiplexer 122 with the pumping light output from the pumping light source 150. The pumping light combined in the pumping light coupler 211 is output to the optical multiplexer 111. The optical multiplexer 111 combines the pumping light and signal light combined in the pumping light coupler 211, and outputs the combined light to the multi-core EDF 103.

[0048] The multi-core fiber amplifier 300B having such a configuration can efficiently utilize the pump light, similar to the multi-core fiber amplifier 200. The reason is that the pump light output from the multi-core EDF 102 can be reused (recycled) by inputting the pump light again into the multi-core EDF 103.

[0049] Note that the configurations of the multi-core fiber amplifier 300A and the multi-core fiber amplifier 300B are not exclusive. That is, the multi-core fiber amplifier 300 may be configured to include the optical demultiplexer 122 and the pumping light combiner 211 in Fig. 8 in addition to the pumping light conditioners 130 and 135 in Fig. 7. With such a configuration, the effects of both the multi-core fiber amplifiers 300A and 300B can be obtained.

[0050] The embodiments of the present disclosure can also be described as follows, but are not limited to the following:

[0051] (Appendix 1) a first optical multiplexing means for combining pump light of a single wavelength used for amplifying signal light with first signal light, which is the signal light in a first wavelength band, and second signal light, which is the signal light in a second wavelength band, and outputting the combined signal; a first amplifying means including a multi-core fiber doped with a rare earth element, receiving the output light from the first optical multiplexing means and amplifying and outputting at least the first signal light; a first optical demultiplexing means for demultiplexing output light from the first amplifying means into the first signal light, the second signal light, and the pump light, and outputting the demultiplexed light; a second amplifying means including a multi-core fiber doped with a rare earth element, receiving the second signal light and the pumping light output from the first optical demultiplexing means, amplifying the input second signal light, and outputting the amplified second signal light; a second optical multiplexing means for multiplexing the first signal light output from the first optical demultiplexing means and the second signal light output from the second amplifying means; A multicore fiber amplifier comprising:

[0052] (Appendix 2) 2. The multi-core fiber amplifier according to claim 1, wherein an absorption rate of the pumping light in the first amplifying means is equal to or lower than an absorption rate of the pumping light in the second amplifying means.

[0053] (Appendix 3) 3. The multi-core fiber amplifier according to claim 1, wherein the first wavelength band is a C-band and the second wavelength band is an L-band.

[0054] (Appendix 4) 4. The multi-core fiber amplifier according to claim 1, further comprising: a pumping light adjusting unit that adjusts the intensity of the pumping light input to the second amplifying unit.

[0055] (Appendix 5) 5. The multi-core fiber amplifier according to claim 4, wherein the pumping light adjusting means comprises an optical attenuator that attenuates the power of the pumping light.

[0056] (Appendix 6) 6. The multi-core fiber amplifier according to claim 4, wherein the pumping light adjusting means comprises third optical multiplexing means for inputting the pumping light to the second amplifying means.

[0057] (Appendix 7) 7. The multi-core fiber amplifier according to claim 1, further comprising: a pumping light generating means for generating the pumping light and inputting the pumping light to the first optical multiplexing means.

[0058] (Appendix 8) a second optical demultiplexing means for demultiplexing the second signal light and the pumping light output from the second amplifying means and inputting the demultiplexed second signal light to the second optical multiplexing means; an excitation light combining means for combining the excitation light demultiplexed by the second optical demultiplexing means with the excitation light output from the excitation light generating means; 8. The multi-core fiber amplifier according to claim 7, comprising:

[0059] (Appendix 9) a third amplifying means including a multi-core fiber doped with a rare earth element, for amplifying a third signal light, which is the signal light in a third wavelength band; a third optical demultiplexing means for demultiplexing the light output from the third amplifying means into light including the first signal light, the second signal light, and the pumping light, and the third signal light; Equipped with the third amplifying means and the third optical demultiplexing means are disposed between the first optical multiplexing means and the first amplifying means, the first optical multiplexing means combines the pumping light with the first signal light, the second signal light, and the third signal light and outputs the combined light; 10. A multi-core fiber amplifier according to any one of appendices 1 to 8.

[0060] (Appendix 10) 10. The multi-core fiber amplifier according to claim 9, wherein an absorption rate of the pumping light in the third amplifying means is equal to or lower than an absorption rate of the pumping light in the first amplifying means.

[0061] (Appendix 11) 11. The multi-core fiber amplifier according to claim 9 or 10, wherein the third wavelength band is the S-band.

[0062] (Appendix 12) a first optical multiplexing means for combining pump light of a single wavelength used for amplifying signal light with a first signal light, which is the signal light in a first wavelength band, and a second signal light, which is the signal light in a second wavelength band, and outputting the combined signal; inputting the output light from the first optical multiplexing means into a first amplifying means including a multi-core fiber doped with a rare earth element, and amplifying and outputting at least the first signal light; outputting the output light from the first amplifying means by a first optical demultiplexing means into the first signal light, the second signal light, and the pumping light; inputting the second signal light and the pumping light output from the first optical demultiplexing means to a second amplifying means including a multi-core fiber doped with a rare earth element, and amplifying and outputting the input second signal light; the first signal light output from the first optical demultiplexing means and the second signal light output from the second amplifying means are multiplexed by a second optical multiplexing means; Optical amplification method.

[0063] (Appendix 13) 13. The optical amplification method according to claim 12, wherein the absorptance of the pumping light in the first amplifying means is equal to or less than the absorptance of the pumping light in the second amplifying means.

[0064] (Appendix 14) 14. The optical amplification method according to claim 12, wherein the first wavelength band is a C-band and the second wavelength band is an L-band.

[0065] (Appendix 15) 15. The optical amplification method according to any one of claims 12 to 14, further comprising adjusting the intensity of the pump light input to the second amplification means.

[0066] (Appendix 16) 16. The optical amplification method according to claim 15, wherein the power of the pump light is attenuated by an optical attenuator.

[0067] (Appendix 17) 17. The optical amplification method according to claim 15, wherein the pumping light is input to the second amplifying means.

[0068] (Appendix 18) 18. The optical amplification method according to any one of claims 12 to 17, further comprising generating the pumping light and inputting the pumping light to the first optical multiplexing means.

[0069] (Appendix 19) the second signal light and the pumping light output from the second amplifying means are demultiplexed by a second optical demultiplexing means; inputting the demultiplexed second signal light into the second optical multiplexing means; combining the demultiplexed pumping light with the pumping light; 19. The optical amplification method according to claim 18.

[0070] (Appendix 20) a third amplifying means including a multi-core fiber doped with a rare earth element and a third optical demultiplexing means are disposed between the first optical multiplexing means and the first amplifying means; combining the pumping light with the first signal light, the second signal light, and a third signal light that is the signal light in a third wavelength band by the first optical combining means, and inputting the combined light into the third amplifying means; amplifying at least third signal light, which is the signal light in a third wavelength band, by the third amplification means; the light output from the third amplifying means is demultiplexed by the third optical demultiplexing means into light including the first signal light, the second signal light, and the pumping light, and the third signal light; 20. An optical amplification method according to any one of claims 12 to 19.

[0071] (Appendix 21) 21. The optical amplification method according to claim 20, wherein the absorption rate of the pumping light in the third amplifying means is equal to or lower than the absorption rate of the pumping light in the first amplifying means.

[0072] (Appendix 22) 22. The optical amplification method according to claim 20, wherein the third wavelength band is the S band.

[0073] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. For example, the description of the multi-core fiber amplifier in each embodiment also discloses the configuration of an optical transmission system including the multi-core fiber amplifier and a signal source, optical transmitter, optical receiver, and optical transceiver connected thereto, as well as an optical amplification method in the multi-core fiber amplifier.

[0074] Furthermore, the configurations described in the respective embodiments are not necessarily mutually exclusive, and the functions and effects of the present disclosure may be achieved by a configuration that combines all or part of the above-described embodiments. [Explanation of symbols]

[0075] 100, 100A, 200 Multicore Fiber Amplifier 111, 112 Optical multiplexer 121, 122, 123 Optical demultiplexer 130, 130A Pump Light Conditioner 131, 132, 171 Optical filters 133 Variable Optical Attenuator 134 Optical Coupler 135 Excitation light regulator 150 Excitation Light Source 160 signal source 161, 162 MCF transmission line 171 Optical Filter 211 Pumping Optical Coupler 300, 300A, 300B Multicore Fiber Amplifier 900 Multicore Fiber Amplifier 901, 902 MC-EDF 910 signal source 911, 912 Optical demultiplexer 921, 922, 923 Optical multiplexer 932 MCF transmission line 950 excitation light source

Claims

1. a first optical multiplexing means for combining pump light of a single wavelength used for amplifying signal light with first signal light, which is the signal light in a first wavelength band, and second signal light, which is the signal light in a second wavelength band, and outputting the combined signal; a first amplifying means including a multi-core fiber doped with a rare earth element, receiving the output light from the first optical multiplexing means and amplifying and outputting at least the first signal light; a first optical demultiplexing means for demultiplexing output light from the first amplifying means into the first signal light, the second signal light, and the pump light, and outputting the demultiplexed light; a second amplifying means including a multi-core fiber doped with a rare earth element, receiving the second signal light and the pumping light output from the first optical demultiplexing means, amplifying the input second signal light, and outputting the amplified second signal light; a second optical multiplexing means for multiplexing the first signal light output from the first optical demultiplexing means and the second signal light output from the second amplifying means; A multicore fiber amplifier comprising:

2. The multi-core fiber amplifier according to claim 1 , wherein an absorptance of the pumping light in the first amplifying means is equal to or less than an absorptance of the pumping light in the second amplifying means.

3. 3. The multi-core fiber amplifier according to claim 1, wherein the first wavelength band is a C-band and the second wavelength band is an L-band.

4. The multi-core fiber amplifier according to claim 1 , further comprising: a pumping light adjusting unit that adjusts the intensity of the pumping light input to the second amplifying unit.

5. The multi-core fiber amplifier according to claim 4 , wherein the pumping light adjusting means comprises an optical attenuator that attenuates the power of the pumping light.

6. 5. The multi-core fiber amplifier according to claim 4, wherein the pumping light adjusting means comprises third optical multiplexing means for inputting the pumping light to the second amplifying means.

7. 3. The multi-core fiber amplifier according to claim 1, further comprising: a pumping light generating means for generating the pumping light and inputting the pumping light to the first optical multiplexing means.

8. a second optical demultiplexing means for demultiplexing the second signal light and the pumping light output from the second amplifying means and inputting the demultiplexed second signal light to the second optical multiplexing means; an excitation light combining means for combining the excitation light demultiplexed by the second optical demultiplexing means with the excitation light output from the excitation light generating means; The multi-core fiber amplifier according to claim 7 , comprising:

9. a third amplifying means including a multi-core fiber doped with a rare earth element, and amplifying a third signal light, the third signal light being the signal light in a third wavelength band; a third optical demultiplexing means for demultiplexing the light output from the third amplifying means into light including the first signal light, the second signal light, and the pumping light, and the third signal light; Equipped with the third amplifying means and the third optical demultiplexing means are disposed between the first optical multiplexing means and the first amplifying means, the first optical multiplexing means combines the pumping light with the first signal light, the second signal light, and the third signal light and outputs the combined light; 3. A multi-core fiber amplifier according to claim 1 or 2.

10. a first optical multiplexing means for multiplexing a pump light having a single wavelength used for amplifying the signal light with a first signal light which is the signal light in a first wavelength band and a second signal light which is the signal light in a second wavelength band, and outputting the multiplexed pump light; inputting the output light from the first optical multiplexing means into a first amplifying means including a multi-core fiber doped with a rare earth element, and amplifying and outputting at least the first signal light; outputting the output light from the first amplifying means by a first optical demultiplexing means into the first signal light, the second signal light, and the pumping light; inputting the second signal light and the pumping light output from the first optical demultiplexing means to a second amplifying means including a multi-core fiber doped with a rare earth element, amplifying and outputting the input second signal light; the first signal light output from the first optical demultiplexing means and the second signal light output from the second amplifying means are multiplexed by a second optical multiplexing means; Optical amplification method.

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