Optical amplifier

Abstract

To eliminate the need for a filter for removing idler light.SOLUTION: An optical amplifier includes: means for multiplexing wavelength multiplexed signal light and first pump light to generate first multiplexed light; means for multiplexing the wavelength multiplexed signal light and second pump light to generate second multiplexed light; means for performing optical parametric amplification on the wavelength multiplexed signal light included in the first multiplexed light by the first pump light to output third multiplexed light, and performing optical parametric amplification on the wavelength multiplexed signal light included in the second multiplexed light by the second pump light to output fourth multiplexed light; and means for performing processing of outputting the wavelength multiplexed signal light on the basis of the third multiplexed light and the fourth multiplexed light. Frequencies of the first pump light and the second pump light are the same, and a phase of the first pump light is different from a phase of the second pump light by π / 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to optical amplifiers. [Background technology]

[0002] An optical amplifier that uses a second-order, third-order, or other nonlinear optical effect is called an optical parametric amplifier. Compared to an optical amplifier that uses an ion-doped optical fiber, such as an EDFA, an optical parametric amplifier is capable of amplifying signals over an extremely wide bandwidth. Non-Patent Document 1 discloses a configuration in which an optical parametric amplifier amplifies wavelength-multiplexed signal light containing multiple wavelength-multiplexed signal light.

[0003] An optical parametric amplifier has a nonlinear medium, such as a waveguide on a semiconductor device or an optical fiber, in which signal light is amplified by pump light. The pump light is usually unmodulated continuous light. During the amplification process using the pump light, the pump light is attenuated and idler light is generated. The idler light is generated on the opposite side of the frequency axis from the signal light, with the pump light at the center, and its bandwidth corresponds to the bandwidth of the signal light. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] T. Kobayashi,et al.,"103-ch.132-Gbaud PS-QAM Signal Inline-amplified Transmission with 14.1-THz Bandwidth Lumped PPLN-based OPAs over 400-km G.652.D SMF".,2023 Optical Fiber Communications Conference and Exhibition (OFC),San Diego,CA,USA,2023,pp.1-3 Summary of the Invention [Problem to be solved by the invention]

[0005] For example, when a wavelength-multiplexed signal light containing multiple signal lights is amplified by an optical parametric amplifier, it is necessary to prevent the idler light from interfering with the signal light. In other words, it is necessary to determine the frequency allocation of multiple signal lights and pump light so that the interfering light does not overlap with the signal light. Furthermore, since the idler light is an unwanted signal, the optical amplifier must remove the idler light. In Non-Patent Document 1, the unwanted idler light is removed by a filter.

[0006] The present disclosure provides a technique that enables the use of a frequency arrangement in which the idler light overlaps with the signal light, or a technique that eliminates the need for a filter that removes the idler light. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, an optical amplifier includes a first multiplexing means that multiplexes wavelength-multiplexed signal light including a plurality of signal lights with first pump light to generate first multiplexed light; a second multiplexing means that multiplexes the wavelength-multiplexed signal light with second pump light to generate second multiplexed light; an amplifying means that optically parametrically amplifies the wavelength-multiplexed signal light included in the first multiplexed light using the first pump light included in the first multiplexed light to output third multiplexed light including idler light generated by the optical parametric amplification, and optically parametrically amplifies the wavelength-multiplexed signal light included in the second multiplexed light using the second pump light included in the second multiplexed light to output fourth multiplexed light including idler light generated by the optical parametric amplification; and a processing means that performs processing to output the wavelength-multiplexed signal light based on the third multiplexed light and the fourth multiplexed light, wherein the first pump light and the second pump light have the same frequency and the phase of the first pump light differs from the phase of the second pump light by π / 2. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to use a frequency arrangement in which the idler light overlaps with the signal light, or to eliminate the need for a filter to remove the idler light. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of an optical amplifier. [Figure 2] 1A and 1B are diagrams showing examples of wavelength-multiplexed signal light, multiplexed light, and multiplexed light that has passed through a nonlinear medium. [Figure 3] FIG. 2 is a diagram showing an example of the configuration of a multiplexer. [Figure 4] FIG. 1 is a diagram showing an example of the configuration of an optical amplifier. [Figure 5] FIG. 1 is a diagram showing an example of the configuration of an optical amplifier. [Figure 6] FIG. 1 is a diagram showing an example of the configuration of an optical amplifier. [Figure 7] FIG. 1 is a diagram showing an example of the configuration of an optical amplifier. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. Furthermore, the same reference numerals are used for the same or similar components, and redundant explanations will be omitted.

[0011] First Embodiment 1 is a schematic diagram of an optical amplifier according to this embodiment. A light source 10 generates pump light and outputs it to a coupler 20. The coupler 20 splits the pump light into at least two beams, outputs one of the split pump light beams to a phase shifter 11, and outputs the other of the split pump light beams to a multiplexer 31. The phase shifter 11 shifts the phase of the input pump light by π / 2 and outputs the shifted pump light to a multiplexer 30. That is, pump light beams with a phase difference of π / 2 are input to the multiplexers 30 and 31.

[0012] Wavelength-multiplexed signal light is input to the coupler 21. FIG. 2A shows wavelength-multiplexed signal light used to explain this embodiment. In the example of FIG. 2A, the wavelength-multiplexed signal light includes six signal lights S1 to S6 whose center frequencies are equally spaced on the frequency axis. In this example, the signal lights S1 to S6 have the same bandwidth. The coupler 21 branches the wavelength-multiplexed signal light into at least two, outputs one branched wavelength-multiplexed signal light to the multiplexer 30, and outputs the other branched wavelength-multiplexed signal light to the multiplexer 31. The multiplexers 30 and 31 output multiplexed light obtained by multiplexing the input pump light and wavelength-multiplexed signal light to the nonlinear media 40 and 41, respectively. FIG. 2B shows multiplexed light output from the multiplexers 30 and 31. The arrow between the signal light S3 and the signal light S4 in FIG. 2B indicates the pump light. As described above, the pump light included in the multiplexed light output from the multiplexer 30 and the pump light included in the multiplexed light output from the multiplexer 31 have a phase difference of π / 2.

[0013] In this embodiment, the frequency (wavelength) of the pump light is set to satisfy the following condition. Condition 1: The frequency must be outside the band of each signal light. Condition 2: At least one signal light must exist on both the lower and higher frequency sides of the pump light. In FIG. 2B, three signal lights exist on the lower and higher frequency sides of the pump light, respectively, so condition 2 is satisfied.

[0014] 2B, the frequency distance between signal light S3 and signal light S4 and the pump light is equal, the frequency distance between signal light S2 and signal light S5 and the pump light is equal, and the frequency distance between signal light S1 and signal light S6 and the pump light is equal. In the following description, two signal lights having the same frequency distance from the pump light are referred to as a "signal light pair." According to FIG. 2B, signal light S1 and signal light S6 form one signal light pair, signal light S2 and signal light S5 form one signal light pair, and signal light S3 and signal light S4 form one signal light pair.

[0015] 2×2 couplers can be used as the multiplexers 30 and 31. Note that using 2×2 couplers as the multiplexers 30 and 31 reduces the power of the wavelength-multiplexed signal light and pump light contained in the multiplexed light by 3 dB. To suppress this power reduction, the multiplexers 30 and 31 can also be configured as shown in FIG. 3. The fiber Bragg grating (FBG) 302 in FIG. 3 is configured to reflect the pump light but not the wavelength-multiplexed signal light. The pump light input to port #1 of the circulator 301 is output from port #2 of the circulator 301, but is reflected by the FBG 302 and re-input to port #2 of the circulator 301. Meanwhile, the wavelength-multiplexed signal light is input to port #2 of the circulator 301 via the FBG 302. Therefore, multiplexed light obtained by multiplexing the wavelength-multiplexed signal light and the pump light is output from port #3 of the circulator 301.

[0016] The wavelength-multiplexed signal light included in the multiplexed light output from the multiplexer 30 is amplified by the pump light included in the multiplexed light as it propagates through the nonlinear medium 40. At this time, idler light is generated and the pump light is attenuated. Similarly, the wavelength-multiplexed signal light included in the multiplexed light output from the multiplexer 31 is amplified by the pump light included in the multiplexed light as it propagates through the nonlinear medium 41. At this time, idler light is generated and the pump light is attenuated. In this way, the nonlinear medium 40 and the nonlinear medium 41 function as amplification media that amplify the wavelength-multiplexed signal light with pump light.

[0017] Here, the electric field component of the pump light is E p and the electric field component of the signal light is E s Then, the electric field component of the idler light, E i is expressed by the following formula: E i ∝E p E p E s * In addition, E s * is E sIn other words, the difference between the center frequency of the idler light and the frequency of the pump light corresponds to the difference between the center frequency of the signal light and the frequency of the pump light, and the electric field component of the idler light is the complex conjugate of the electric field component E s It should be noted that, when the pump light included in the multiplexed light output from the multiplexer 31 is used as a reference, the phase of the pump light included in the multiplexed light output from the multiplexer 30 is shifted by π / 2. As is clear from the above equation, the electric field component E of the idler light i is proportional to the square of the pump light, the phase difference between the electric field component of the idler light output from the nonlinear medium 41 and the electric field component of the idler light output from the nonlinear medium 40 is π. In other words, the electric field component of the idler light output from the nonlinear medium 41 is expressed as E i Then, the electric field component of the idler light output from the nonlinear medium 40 is (-E i ) becomes.

[0018] Therefore, the combined light including wavelength-multiplexed signal light and idler light output from the nonlinear medium 40 is as shown in Figure 2(C), and the combined light including wavelength-multiplexed signal light and idler light output from the linear medium 41 is as shown in Figure 2(D). In Figures 2(C) and 2(D), the upper side of the frequency axis represents the wavelength-multiplexed signal light, and the lower side of the frequency axis represents the wavelength-multiplexed idler light (wavelength-multiplexed idler light). Although Figures 2(C) and 2(D) show the wavelength-multiplexed signal light and the wavelength-multiplexed idler light individually, in reality, combined light obtained by combining the wavelength-multiplexed signal light and the wavelength-multiplexed idler light is output from the nonlinear mediums 40 and 41. In reality, the pump light attenuated by optical parametric amplification is also output from the nonlinear mediums 40 and 41, but since there is no problem if the pump light remains, the pump light is omitted from Figures 2(C) and 2(D).

[0019] As shown in Figures 2(C) and 2(D), each of the signal lights S1 to S6 is combined with an idler light based on the other signal light of the signal light pair. For example, signal light S1 and signal light S6 are a signal light pair, but signal light S1 is combined with the idler light of signal light S6, and signal light S6 is combined with the idler light of signal light S1. As mentioned above, the idler light corresponds to the complex conjugate of the original signal light, so in Figures 2(C) and 2(D), the idler light of signal light Sn (n is an integer from 1 to 6) is referred to as Sn * As described above, the phase difference between the electric field component of the idler light output from the nonlinear medium 41 and the electric field component of the idler light output from the nonlinear medium 40 is π, so the idler light of the signal light Sn output from the nonlinear medium 40 is expressed as (-Sn * ), and the idler light of the signal light Sn output from the nonlinear medium 41 is (+Sn * )

[0020] The multiplexed light beams output from the nonlinear media 40 and 41 are output to the processing unit 12. The processing unit 12 multiplexes the multiplexed light beams output from the nonlinear media 40 and 41. As is clear from Figures 2(C) and 2(D), by multiplexing the multiplexed light beams output from the nonlinear media 40 and the nonlinear media 41, the idler light beams are cancelled out, and wavelength-multiplexed signal light beams including signal light beams S1 to S6 are output.

[0021] If the nonlinear medium 40 and the nonlinear medium 41 have different characteristics, the idler light may not be canceled out even when the multiplexed light output from the nonlinear medium 40 and the multiplexed light output from the nonlinear medium 41 are multiplexed, and the idler light may remain. However, if the nonlinear medium 40 and the nonlinear medium 41 are configured as waveguides on a semiconductor device, the characteristics of the nonlinear medium 40 and the nonlinear medium 41 can be made similar, and the level of the remaining idler light can be suppressed. Furthermore, in the processing unit 12, instead of simply multiplexing the multiplexed light output from the nonlinear medium 40 and the multiplexed light output from the nonlinear medium 41, optical MIMO processing can be applied to the two multiplexed lights. Optical MIMO processing can be realized, for example, by a two-stage Mach-Zehnder interferometer. Optical MIMO processing makes it possible to output wavelength-multiplexed signal light with suppressed remaining idler light.

[0022] The above configuration makes it possible to use a frequency arrangement in which the idler light overlaps with the signal light.

[0023] In FIG. 2B, the number of signal lights on the lower frequency side of the pump light and the number of signal lights on the higher frequency side are the same, three. However, the number of signal lights on the lower frequency side of the pump light and the number of signal lights on the higher frequency side may be different. For example, if the pump light is placed between signal light S1 and signal light S2, there will be one signal light pair consisting of S1 and S2. In this case, in the multiplexed light that has passed through the nonlinear medium, only signal light S1 and signal light S2 overlap with the idler light, while signal lights S3 to S6 do not overlap with idler light based on other signal lights, and idler light based on signal lights S3 to S6 does not overlap with other signal lights. Even in this case, the idler light can be canceled out by multiplexing the multiplexed light output from nonlinear medium 40 with the multiplexed light output from nonlinear medium 41.

[0024] 2A, the bandwidths of the signal lights are the same and the center frequencies of the signal lights are equally spaced on the frequency axis. However, as long as the above conditions 1 and 2 are satisfied, the bandwidths of the signal lights may be different and the center frequencies of the signal lights do not need to be equally spaced on the frequency axis. This is because, due to condition 2, the idler light may overlap with the signal light. Therefore, in the above explanation, two signal lights that are equidistant from the pump light on the frequency axis are considered to be a signal light pair. However, more generally, two signal lights whose idler lights overlap each other are considered to be a signal light pair.

[0025] Furthermore, for example, when all signal lights are arranged to be on the high-frequency side or the low-frequency side of the pump light, that is, when condition 2 is not applied, none of the idler lights overlap with the signal lights. However, even in this case, the idler lights can be canceled out by multiplexing the multiplexed light output from the nonlinear medium 40 and the multiplexed light output from the nonlinear medium 41. In other words, there is no need to provide a filter for removing the idler light in the optical amplifier. Therefore, this embodiment has the advantage that a filter for removing the idler light is not required even when only condition 1 is applied.

[0026] Second Embodiment Next, the second embodiment will be described, focusing on the differences from the first embodiment. Fig. 4 is a configuration diagram of an optical amplifier according to this embodiment. The optical amplifier of this embodiment is provided with wavelength demultiplexers 50 and 51, receivers 70 and 71, and a MIMO processor 80 instead of the processor 12 of the first embodiment. The multiplexed light output by the nonlinear media 40 and 41 is the same as in the first embodiment, so a repeated description will be omitted.

[0027] The multiplexed light beams output from the nonlinear media 40 and 41 are output to wavelength demultiplexers 50 and 51, respectively. The wavelength demultiplexers 50 and 51 demultiplex each signal light pair into wavelengths, and output multiplexed light beams obtained by multiplexing one of the two signal lights in the signal light pair with the idler light beam of the other signal light. Using the examples of FIGS. 2C and 2D, the wavelength demultiplexers 50 and 51 output, for example, multiplexed light beams obtained by multiplexing the idler light beams of signal light S1 and S6, multiplexed light beams obtained by multiplexing the idler light beams of signal light S2 and S5, and multiplexed light beams obtained by multiplexing the idler light beams of signal light S3 and S4. It should be noted that the wavelength demultiplexers 50 and 51 may be configured to output multiplexed light beams obtained by multiplexing the idler light beams of signal light S6 and S1, instead of the multiplexed light beams obtained by multiplexing the idler light beams of signal light S1 and S6. The same applies to the other signal light pairs.

[0028] 2(C) and 2(D), three multiplexed lights corresponding to the three signal light pairs are output from the wavelength demultiplexers 50 and 51. Since the processing for each of the three multiplexed lights corresponding to the three signal light pairs is similar, the following describes the processing for the multiplexed light output from the wavelength demultiplexers 50 and 51, in which the idler light of signal light S1 and signal light S6 are multiplexed.

[0029] The receiving unit 70 coherently receives combined light obtained by combining signal light S1 and idler light of signal light S6 of the signal light shown in FIG. 2(C). That is, the receiving unit 70 has a light source that generates local light, combines the local light and combined light, and performs photoelectric conversion to output an electrical signal corresponding to the combined light obtained by combining signal light S1 and idler light of signal light S6. The receiving unit 71 also coherently receives combined light obtained by combining signal light S1 and idler light of signal light S6 of the signal light shown in FIG. 2(D), and outputs an electrical signal corresponding to the combined light obtained by combining signal light S1 and idler light of signal light S6. Note that the light source that generates the local light used by the receiving unit 70 for coherent reception and the light source that generates the local light used by the receiving unit 71 for coherent reception can be the same.

[0030] The electrical signals output by the receiving units 70 and 71 correspond to the sum of the complex conjugates of the electric field component of the signal light S1 and the electric field component of the signal light S6, respectively. However, the signs of the complex conjugates of the electric field component of the signal light S6 included in the electrical signal output by the receiving units 70 and the electrical signal output by the receiving units 71 are different from each other. The MIMO processing unit 80 performs MIMO processing in the electrical domain on the electrical signals from the receiving units 70 and 71, thereby outputting an electrical signal corresponding to the electric field component of the signal light S1 and an electrical signal corresponding to the electric field component of the signal light S6. Note that what is determined in the MIMO processing is the electrical signal corresponding to the complex conjugate of the electric field component of the signal light S6, and the MIMO processing unit 80 is configured to output an electrical signal corresponding to the complex conjugate of this electrical signal.

[0031] Similar processing is performed for the other two frequency pairs, resulting in six electrical signals corresponding to the signal lights S1 to S6 being obtained inside the optical amplifier. The optical amplifier then converts the six electrical signals into the signal lights S1 to S6 and outputs a wavelength-multiplexed signal light including the signal lights S1 to S6.

[0032] The above configuration makes it possible to use a frequency arrangement in which the idler light overlaps with the signal light, and also makes it possible to eliminate the need for a filter to remove the idler light.

[0033] As in the first embodiment, the number of signal lights on the lower frequency side of the pump light does not need to be the same as the number of signal lights on the higher frequency side. For example, if the pump light is placed between the signal light S1 and the signal light S2, there will be one signal light pair consisting of S1 and S2. In this case, the wavelength demultiplexers 50 and 51 extract and coherently receive the combined light of the signal light S1 and the idler light of the signal light S2, or the combined light of the signal light S2 and the idler light of the signal light S1, and then perform MIMO processing to generate electrical signals corresponding to the signal light S1 and the signal light S2. Furthermore, since the signal lights S3 to S6 do not overlap with the idler light, electrical signals corresponding to the signal lights S3 to S6 can be generated without performing MIMO processing. In this case, the wavelength demultiplexer 50 performs wavelength demultiplexing on a signal light basis for signal lights that are not part of a signal light pair.

[0034] In this embodiment, the two signal lights of the signal light pair do not need to have the same band. In addition, in this embodiment, the frequency distance between the center frequency of one signal light of the signal light pair and the pump light is equal to the frequency distance between the center frequency of the other signal light of the signal light pair and the pump light, but as long as one signal light of the signal light pair and the idler light of the other signal light of the signal light pair overlap, the frequency distance between the center frequencies of the two signal lights of the signal light pair and the pump light does not need to be equal.

[0035] Third Embodiment Next, the third embodiment will be described, focusing on the differences from the first embodiment. This embodiment is applied when wavelength-multiplexed signal light is further polarization-multiplexed. Figure 5 is a diagram showing the configuration of an optical amplifier according to this embodiment. The pump light output from light source 1 is adjusted by polarization rotator 13 so that its polarization plane is at 45 degrees with respect to both the X-polarized wave direction and the Y-polarized wave direction. After that, the configuration up to nonlinear media 40 and 41 is the same as in the first embodiment.

[0036] The multiplexed light beams output from the nonlinear media 40 and 41 are output to polarization beam splitters (PBSs) 60 and 61, respectively. The PBSs 60 and 61 each separate the X-polarized multiplexed light beam and the Y-polarized multiplexed light beam contained in the input multiplexed light beam, and output the separated light beams. The two X-polarized multiplexed light beams output from the PBSs 60 and 61 and the two Y-polarized multiplexed light beams output from the PBSs 60 and 61 are output to the processing unit 14. The processing unit 14 multiplexes the two X-polarized multiplexed light beams to generate X-polarized wavelength-multiplexed signal light in which the X-polarized idler light is offset, and multiplexes the two Y-polarized multiplexed light beams to generate Y-polarized wavelength-multiplexed signal light in which the Y-polarized idler light is offset. Furthermore, the processing unit 14 polarization-multiplexes the X-polarized wavelength-multiplexed signal light and the Y-polarized wavelength-multiplexed signal light, and outputs the polarization-multiplexed wavelength-multiplexed signal light.

[0037] The above configuration makes it possible to use a frequency allocation in which the idler light overlaps with the signal light. It also makes it possible to eliminate the need for a filter to remove the idler light. Note that in this embodiment, the processing unit 14 can also perform MIMO processing in the optical domain.

[0038] <Fourth embodiment> Next, the fourth embodiment will be described, focusing on the differences from the third embodiment. In the second embodiment, MIMO processing is performed in the electrical domain instead of the processing unit 12 of the first embodiment. In this embodiment, MIMO processing is also performed in the electrical domain instead of the processing unit 14 of the third embodiment. Figure 6 is a configuration diagram of an optical amplifier according to this embodiment. The multiplexed light output by the nonlinear media 40 and 41 is the same as in the third embodiment.

[0039] As in the second embodiment, the wavelength demultiplexers 50 and 51 perform wavelength demultiplexing on a signal light pair basis. The PBSs 60 and 61 perform polarization demultiplexing of the multiplexed light corresponding to one signal light pair from the wavelength demultiplexers 50 and 51. The receiver 70 coherently receives the X-polarized multiplexed light from the PBS 60, and the receiver 71 coherently receives the X-polarized multiplexed light from the PBS 61. The receiver 72 coherently receives the Y-polarized multiplexed light from the PBS 60, and the receiver 73 coherently receives the Y-polarized multiplexed light from the PBS 61.

[0040] The MIMO processing unit 80 performs MIMO processing based on the electrical signal corresponding to the X-polarized multiplexed light output by the receiving unit 70 and the electrical signal corresponding to the X-polarized multiplexed light output by the receiving unit 71. The MIMO processing unit 80 also performs MIMO processing based on the electrical signal corresponding to the Y-polarized multiplexed light output by the receiving unit 72 and the electrical signal corresponding to the Y-polarized multiplexed light output by the receiving unit 73. Thereafter, signal light is generated based on the electrical signals of each polarization, and wavelength multiplexing and polarization multiplexing are performed, thereby outputting polarization-multiplexed wavelength-multiplexed signal light.

[0041] The above configuration makes it possible to use a frequency arrangement in which the idler light overlaps with the signal light, and also makes it possible to eliminate the need for a filter to remove the idler light.

[0042] Fifth Embodiment Next, the fifth embodiment will be described, focusing on the differences from the first embodiment. In the first embodiment, two nonlinear media 40 and 41 were used. In this embodiment, the number of nonlinear media used is one. Figure 7 is a configuration diagram of an optical amplifier according to this embodiment. The multiplexed light output from the multiplexer 30 and the multiplexer 31 is the same as in the first embodiment.

[0043] The multiplexed light output from the multiplexer 30 is input to the nonlinear medium 40 via the circulator 90, and then output to the processing unit 12 via the circulator 91. On the other hand, the multiplexed light output from the multiplexer 31 is input to the nonlinear medium 40 via the circulator 91, and then output to the processing unit 12 via the circulator 90. Therefore, the multiplexed light output from the multiplexer 30 and the multiplexer 31 is input to the processing unit 12 via the same nonlinear medium 40. The processing in the processing unit 12 is the same as in the first embodiment.

[0044] In this embodiment, the same configuration as in the second embodiment can be applied in place of the processing unit 12. Furthermore, this embodiment can also be applied to the third and fourth embodiments.

[0045] As described above, in this embodiment, the optical parametric amplification of the combined light output from the combiner 30 and the combiner 31 is performed in the same nonlinear medium 40. Therefore, it is possible to suppress the idler light component that remains when the two combined lights after optical parametric amplification are combined. This embodiment also makes it possible to use a frequency arrangement in which the idler light overlaps with the signal light. Furthermore, it is possible to eliminate the need for a filter to remove the idler light.

[0046] This configuration eliminates the need for a filter to remove idler light, making it possible to contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0047] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention. [Explanation of symbols]

[0048] 30, 31: multiplexer, 40, 41: nonlinear medium, 12: processing unit

Claims

1. a first multiplexing means for multiplexing a wavelength-multiplexed signal light including a plurality of signal lights with a first pump light to generate a first multiplexed light; a second multiplexing means for multiplexing the wavelength-multiplexed signal light and the second pump light to generate a second multiplexed light; an amplifying means for optically parametrically amplifying the wavelength-multiplexed signal light included in the first multiplexed light using the first pump light included in the first multiplexed light, thereby outputting a third multiplexed light including idler light generated by the optical parametric amplification, and for optically parametrically amplifying the wavelength-multiplexed signal light included in the second multiplexed light using the second pump light included in the second multiplexed light, thereby outputting a fourth multiplexed light including idler light generated by the optical parametric amplification; a processing unit for performing processing to output the wavelength-multiplexed signal light based on the third multiplexed light and the fourth multiplexed light; Equipped with An optical amplifier, wherein the first pump light and the second pump light have the same frequency, and the phase of the first pump light differs from the phase of the second pump light by π / 2.

2. 2. The optical amplifier according to claim 1, wherein at least one of the plurality of signal lights is at a lower frequency side than the first pump light, and at least one of the plurality of signal lights is at a higher frequency side than the first pump light.

3. 2. The optical amplifier according to claim 1, wherein said processing means generates said wavelength-multiplexed signal light by multiplexing said third multiplexed light and said fourth multiplexed light.

4. 2. The optical amplifier according to claim 1, wherein said processing means generates said wavelength-multiplexed signal light by performing MIMO processing on said third multiplexed light and said fourth multiplexed light in the optical domain.

5. The processing means a first wavelength separating means for separating the third multiplexed light into wavelengths and outputting a first band of light including a first signal light among the plurality of signal lights and a first idler light generated based on a second signal light among the plurality of signal lights; a second wavelength separating means for separating the wavelength of the fourth multiplexed light and outputting light of the first band; a first receiving means for coherently receiving the light output from the first wavelength separating means and outputting a first electrical signal; a second receiving means for coherently receiving the light output from the second wavelength separating means and outputting a second electrical signal; a MIMO processing means for performing MIMO processing on the first electrical signal and the second electrical signal in an electrical domain, thereby outputting an electrical signal corresponding to the first signal light and an electrical signal corresponding to the second signal light; 3. The optical amplifier of claim 2, comprising:

6. the first pump light and the second pump light are polarized waves that are different in polarization by 45 degrees from a first polarization and a second polarization that is orthogonal to the first polarization, respectively; 2. The optical amplifier according to claim 1, wherein the processing means polarization-separates the third multiplexed light into a fifth multiplexed light of the first polarization and a sixth multiplexed light of the second polarization, polarization-separates the fourth multiplexed light into a seventh multiplexed light of the first polarization and an eighth multiplexed light of the second polarization, and outputs the wavelength-multiplexed signal light based on the fifth multiplexed light, the sixth multiplexed light, the seventh multiplexed light, and the eighth multiplexed light.

7. The amplification means a first medium for optically parametrically amplifying the wavelength-multiplexed signal light included in the first multiplexed light by the first pump light included in the first multiplexed light; a second medium for optically parametrically amplifying the wavelength-multiplexed signal light included in the second multiplexed light by the second pump light included in the second multiplexed light; 7. An optical amplifier according to claim 1, comprising:

8. the amplifying means has a medium that optically parametrically amplifies the wavelength-multiplexed signal light included in the first multiplexed light by using the first pump light included in the first multiplexed light, and optically parametrically amplifies the wavelength-multiplexed signal light included in the second multiplexed light by using the second pump light included in the second multiplexed light, 7. The optical amplifier according to claim 1, wherein the propagation direction of the first multiplexed light and the propagation direction of the second multiplexed light are different from each other in the medium.

9. The first multiplexing means an optical circulator; a fiber Bragg grating configured to reflect the first pump light; 7. An optical amplifier according to claim 1, comprising:

10. 10. The optical amplifier according to claim 9, wherein the first pump light input to the optical circulator is output from a port of the optical circulator to which the fiber Bragg grating is connected, and the wavelength-multiplexed signal light is input to the optical circulator via the fiber Bragg grating.

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