Optical amplifier

Abstract

To reduce a power consumption of an optical amplifier.SOLUTION: An optical amplifier comprises: an excitation light source that generates M (M is an integer of 1 or larger) multi-mode excitation lights; an optical processing part that outputs at least N (N is an integer of 1 or larger) single mode excitation light on the basis of the M multi-mode excitation lights; and N amplification parts. Each of the N amplification parts is made by core excitation by one single mode excitation light in the at least N single mode excitation lights.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Non-Patent Document 1 discloses a configuration in which a single mode laser diode (SM-LD) is used as a pumping light source that supplies pumping light to an optical amplifier. In Non-Patent Document 1, a core pumping method is used in which pumping light from the SM-LD is incident on the core of a rare-earth doped optical fiber, which is the amplifying medium of the optical amplifier. Here, since the electrical-optical conversion efficiency of the SM-LD is low, the power consumption of an optical amplifier that uses an SM-LD as a pumping light source increases.

[0003] Non-Patent Document 2 discloses the use of a multimode laser diode (MM-LD) with higher electrical-optical conversion efficiency than an SM-LD as a pumping light source. Since it is difficult to make the pumping light from the MM-LD enter the core of a rare-earth doped optical fiber, Non-Patent Document 2 adopts a clad pumping method with a rare-earth doped optical fiber having a double clad structure. Note that the double clad structure is a structure having two clads, an inner clad and an outer clad surrounding the inner clad, and the refractive index of the outer clad is lower than that of the inner clad. Also, the clad pumping method is a method in which a pumping light source is made to enter the inner clad to pump a core arranged inside the inner clad. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] X.Liang,et.al.,"Repeater Power Conversion Efficiency in Submarine Optical Communication Systems", IEEE Photonics Journal,vol.13,no.1,pp.1-10,February 2021 [Non-Patent Document 2] H. Takeshita,et.al.,"Past,Current and Future Technologies for Optical Submarine Cables",2019 IEEE / ACM Workshop on Photonics-Optics Technology Oriented Networking, Information and Computing Systems (PHOTONICS),Denver,CO,USA,pp.36-42,2019 Summary of the Invention [Problem to be solved by the invention]

[0005] In the cladding pumping method, most of the pumping light passes through the rare-earth doped optical fiber without pumping the core of the rare-earth doped optical fiber. In other words, the pumping efficiency of the cladding pumping method is low. In this way, even in the configuration of Non-Patent Document 2, the power consumption of the optical amplifier increases due to the low pumping efficiency.

[0006] The present disclosure provides a technique for reducing the power consumption of an optical amplifier. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a laser diode includes an excitation light source that generates M (M is an integer equal to or greater than 1) multi-mode excitation light beams, an optical processing unit that outputs at least N (N is an integer equal to or greater than 1) single-mode excitation light beams based on the M multi-mode excitation light beams, and N amplification units, each of which is core-excited by one single-mode excitation light beam among the at least N single-mode excitation light beams. Effect of the Invention

[0008] According to the present disclosure, the power consumption of an optical amplifier can be reduced. [Brief description of the drawings]

[0009] [Figure 1]FIG. 2 is a configuration diagram of an optical amplifier according to an embodiment. [Diagram 2] FIG. 2 is a configuration diagram of an optical amplifier according to an embodiment. [Diagram 3] FIG. 2 is a configuration diagram of an optical amplifier according to an embodiment. [Figure 4] FIG. 2 is a configuration diagram of an optical amplifier according to an embodiment. [Diagram 5] FIG. 2 is a configuration diagram of an optical amplifier according to an embodiment. [Figure 6] FIG. 2 is a configuration diagram of an optical amplifier according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more features among the multiple features described in the embodiments may be arbitrarily combined. In addition, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0011] In each of the following embodiments, M (M is an integer equal to or greater than 1) pumping light sources 1 generate multimode (MM) pumping light (hereinafter, MM pumping light), and supply the pumping light to N (N is an integer equal to or greater than 1) amplifiers 4. The amplifiers 4 have a pumping combiner and an amplification medium. The amplification medium is, for example, a single-mode rare-earth doped optical fiber, and optically amplifies the signal light propagating through the core by the pumping light. The pumping combiner is configured to make the pumping light input to the amplifiers 4 enter the core of the amplification medium. That is, the optical amplifiers in each of the following embodiments use a core pumping method.

[0012] Note that the magnitude relationship between the number M of excitation light sources 1 and the number N of amplification units 4 is arbitrary, and M > N, M < N, or M = N is acceptable. By setting the number M of excitation light sources 1 to 2 or more, the excitation light sources 1 can be configured redundantly. That is, even if a failure occurs in a predetermined number or less of the M excitation light sources 1, the supply of excitation light to the N amplification units 4 can be continued. For example, the number N of amplification units 4 can be determined according to the specifications of the optical amplifier. And the number M of excitation light sources 1 can be determined based on being able to supply the excitation light required for the N optical amplifiers 4 and the required redundancy number for the excitation light sources 1.

[0013] Also, in the description of each of the following embodiments, reference numerals in the format of "X-Y" are used to distinguish a plurality of identical components. Here, "X" indicates the component, and "Y" indicates the number for distinguishing individuals. When collectively referring to a plurality of identical components, a reference numeral of "X" is used, and the number "Y" for distinguishing individuals is omitted.

[0014] <First Embodiment> FIG. 1 is a configuration diagram of an optical amplifier according to this embodiment. The excitation light sources 1-1 to 1-M are, for example, MM-LDs and generate MM excitation light. The mode separation unit 2-k (k is an integer from 1 to M) separates the MM excitation light from the excitation light source 1-k and outputs single-mode (SM) excitation light (hereinafter referred to as SM excitation light) to the first port of the SM coupler 31. If the number of modes separated by each mode separation unit 2 is L (L is an integer of 2 or more), the number S of SM excitation lights output by the entire mode separation unit 2 is more than M. In this embodiment, S = L × M. Therefore, the number of the first ports of the coupler 31 is set to S = L × M or more. The coupler 31 has N or more second ports.

[0015] The coupler 31 branches the SM pumping light input to one first port by the number of second ports, and outputs it from all second ports with the same power. Therefore, from one second port of the coupler 31, SM pumping light obtained by combining the SM pumping light input to all first ports is output. The N second ports out of all second ports of the coupler 31 correspond one-to-one to the N amplifiers 4, and the SM pumping light output from one second port out of the N second ports is input to the corresponding amplifier 4. As described above, the pumping combiners of the amplifiers 4-1 to 4-N input the input SM pumping light to the core of the amplification medium.

[0016] As described above, in this embodiment, an MM pumping light source 1 with high electrical-optical conversion efficiency and a core pumping method with high pumping efficiency are used. Therefore, the power consumption of the optical amplifier can be reduced. The power of L SM pumping light beams output from each mode separation unit 2 may differ depending on the mode before separation. Furthermore, when M is 2 or more, the power of MM pumping light beams output from each pumping light source 1 may differ for each pumping light source 1. However, in this embodiment, it is possible to prevent the difference in power of pumping light beams supplied to each amplification medium 4 by the coupler 31 from becoming large. In this embodiment, the mode separation unit 2 and the coupler 31 constitute an optical processing unit that outputs at least N SM pumping light beams based on M MM pumping light beams.

[0017] Second Embodiment FIG. 2 is a configuration diagram of an optical amplifier according to this embodiment. The pumping light sources 1-1 to 1-M are, for example, MM-LDs, and generate MM pumping light. The MM coupler 32 has at least N first ports and at least P second ports (P is an integer equal to or greater than 1). P can be smaller than N. If both N and P are 1, the MM coupler 32 is omitted. In other words, the MM coupler 32 is provided when M=1 and P≧2, and when P=1 and M≧2. The coupler 32 branches the MM pumping light input to one first port into the number of second ports, and outputs the same power from all second ports. Therefore, the MM pumping light obtained by combining the MM pumping light input to all first ports is output from one second port of the coupler 32. Each of the mode separation units 2-1 to 2-P performs mode separation of the MM pumping light output from one second port of the coupler 32, and outputs SM pumping light. If the number of modes separated by each mode separation section 2 is L (L is an integer equal to or greater than 2), then the number of SM pumping lights output by the entire mode separation section 2 is S, which is greater than P. In this embodiment, S=L×P. In this embodiment, S=L×P is set to be equal to or greater than N. Of the L×P SM pumping lights, N SM pumping lights are input to amplification sections 4-1 to 4-N. As described above, the pumping combiners of amplification sections 4-1 to 4-N input the input pumping lights to the cores of the amplification media.

[0018] As described above, in this embodiment, the MM pumping light source 1 with high electrical-optical conversion efficiency and the core pumping method with high pumping efficiency are used. Therefore, the power consumption of the optical amplifier can be reduced. Furthermore, when M is 2 or more, the number P of the mode separation units 2 can be made smaller than M. That is, the number of the mode separation units 2 with a complex configuration can be made smaller than the configuration of the first embodiment. Furthermore, when M is 2 or more, the difference in power of the MM pumping light output from each pumping light source 1 can be reduced by the coupler 32. On the other hand, in this embodiment, the difference in power of each SM pumping light output from the mode separation unit 2 may cause a difference in power of the SM pumping light supplied to each amplifier unit 4. However, when the difference in power of each SM pumping light output from the mode separation unit 2 is small, the configuration of this embodiment can be used. In this embodiment, the coupler 32 and the mode separation unit 2 constitute an optical processing unit that outputs at least N SM pumping lights based on M MM pumping lights.

[0019] <Third embodiment> FIG. 3 is a configuration diagram of an optical amplifier according to this embodiment. In this embodiment, the difference in power between the SM pumping lights output by the mode separation unit 2 is suppressed in comparison with the configuration of the second embodiment shown in FIG. 2. Therefore, only the differences from the second embodiment will be described below. S=L×P SM pumping lights output by the P mode separation units 2 are input to the first port of the SM coupler 33. The SM coupler 33 has first ports whose number is equal to or greater than L×P and second ports whose number is equal to or greater than N. As with the coupler 31 of the first embodiment, the coupler 33 outputs the SM pumping light input to one first port from all second ports with equal power. Therefore, the SM pumping light obtained by combining the SM pumping lights input to all first ports is output from one second port of the coupler 33. The N second ports out of all the second ports of the coupler 33 correspond one-to-one to the N amplifying units 4, and the SM pumping light output from one of the N second ports is input to the corresponding amplifying unit 4. As described above, the pumping combiners of the amplifying units 4-1 to 4-N input the input SM pumping light to the cores of the amplifying media.

[0020] As described above, in this embodiment, it is possible to suppress an increase in the difference in power of the SM pumping lights input to each amplifier 4, which may occur in the second embodiment. Note that in this embodiment, the coupler 32, the mode separation unit 2, and the coupler 33 configure an optical processing unit that outputs at least N pieces of SM pumping light based on M pieces of MM pumping light.

[0021] <Fourth embodiment> FIG. 4 is a configuration diagram of an optical amplifier according to this embodiment. The pumping light sources 1-1 to 1-M are, for example, MM-LDs, and generate MM pumping light. The frequency separators 5-k (k is an integer from 1 to M) frequency-separate the MM pumping light from the pumping light source 1-k, and output the MM pumping light to the mode separators 2. For example, if the number of frequencies separated by each frequency separator 5 is Q (Q is an integer of 2 or more), the number of MM pumping light output by the M frequency separators 5 as a whole is S, which is more than M. In this embodiment, S=Q×M. Therefore, in this embodiment, the number of mode separators 2 is S=Q×M. Each mode separator 2 separates the input MM pumping light into modes, and outputs the SM pumping light to the first port of the SM coupler 34. If the number of modes separated by each mode separator 2 is L (L is an integer of 2 or more), the number of SM pumping light output by the S mode separators 2 as a whole is T, which is more than S. In this embodiment, T = L x S = L x Q x M. Therefore, the number of first ports of the coupler 34 is equal to or greater than T = L x Q x M. The coupler 34 has second ports whose number is N or greater.

[0022] The coupler 34 outputs the SM pumping light input to one first port from all second ports with equal power. Therefore, the SM pumping light obtained by combining the SM pumping light input to all the first ports is output from one second port of the coupler 34. The N second ports out of all the second ports of the coupler 34 correspond one-to-one to the N amplifiers 4, and the SM pumping light output from one second port out of the N second ports is input to the corresponding amplifier 4. As described above, the pumping combiners of the amplifiers 4-1 to 4-N input the input SM pumping light to the core of the amplification medium.

[0023] As described above, in this embodiment, the frequency separation section 5 is provided between the pump light source 1 and the mode separation section 2 in the configuration of the first embodiment. Since the mode separation section 2 performs mode separation after frequency separation in the frequency separation section 5, the number of modes L separated in the mode separation section 2 can be reduced, and therefore the configuration of the mode separation section 2 can be simplified and costs can be reduced. Other advantages are the same as those of the first embodiment. In this embodiment, the frequency separation section 5, the mode separation section 2 and the coupler 34 configure an optical processing section that outputs at least N pieces of SM pump light based on M pieces of MM pump light.

[0024] <Fifth embodiment> FIG. 5 is a configuration diagram of an optical amplifier according to this embodiment. The pumping light sources 1-1 to 1-M are, for example, MM-LDs, and generate MM pumping light. The MM coupler 32 has at least M first ports and at least P (P is an integer equal to or greater than 2) second ports. P can be smaller than M. If both M and P are 1, the MM coupler 32 is omitted. In other words, the MM coupler 32 is provided when M=1 and P≧2, and when P=1 and M≧2. The coupler 32 outputs the MM pumping light input to one first port from all second ports with equal power. Therefore, the MM pumping light obtained by combining the MM pumping light input to all first ports is output from one second port of the coupler 32. Each frequency separator 5 frequency-separates the MM pumping light output from one second port of the coupler 32, and outputs the MM pumping light. If the number of frequencies separated by the frequency separator 5 is Q (Q is an integer equal to or greater than 2), then the total number of MM pump lights output by the P frequency separators 5 is S, which is greater than P. In this embodiment, S=Q×P.

[0025] Therefore, in this embodiment, the number of mode separation sections 2 is S=Q×P. Each mode separation section 2 performs mode separation of the input MM pump light, and outputs the SM pump light to the first port of the SM coupler 35. If the number of modes separated by each mode separation section 2 is L (L is an integer equal to or greater than 2), the total number of SM pump light output by the S mode separation sections 2 is T, which is greater than S. In this embodiment, T=L×S=L×Q×P. Therefore, the number of first ports of the coupler 35 is equal to or greater than T=L×Q×P. The coupler 35 has second ports, the number of which is N or greater.

[0026] The coupler 35 outputs the SM pumping light input to one first port from all second ports with equal power. Therefore, the SM pumping light obtained by combining the SM pumping light input to all the first ports is output from one second port of the coupler 35. The N second ports out of all the second ports of the coupler 35 correspond one-to-one to the N amplifiers 4, and the SM pumping light output from one second port out of the N second ports is input to the corresponding amplifier 4. As described above, the pumping combiners of the amplifiers 4-1 to 4-N input the input SM pumping light to the core of the amplification medium.

[0027] As described above, in this embodiment, the frequency separation section 5 is provided between the coupler 32 and the mode separation section 2 of the configuration of the third embodiment. Since the mode separation section 2 performs mode separation after frequency separation in the frequency separation section 5, the number of modes L separated in the mode separation section 2 can be reduced. Therefore, the configuration of the mode separation section 2 can be simplified and costs can be reduced. Other advantages are the same as those of the third embodiment. In this embodiment, the coupler 32, the frequency separation section 5, the mode separation section 2 and the coupler 35 configure an optical processing section that outputs at least N pieces of SM pump light based on M pieces of MM pump light.

[0028] Sixth Embodiment Fig. 6 is a configuration diagram of an optical amplifier according to this embodiment. In this embodiment, the mode separator 2 and coupler 35 are omitted from the configuration of the fifth embodiment shown in Fig. 5, and the output of the frequency separator 5 is input to the amplifier 4. Therefore, only the differences from the fifth embodiment will be described below. In this embodiment, the number S=Q×P of MM pump light output by all P frequency separators 5 is set to N or more.

[0029] In this embodiment, a fused-draw fiber coupler or a side-polished fiber coupler in which the core of an MM optical fiber that propagates MM pumping light and the core of an amplification medium that is an SM optical fiber are placed close to each other is used as the pumping combiner in the amplification unit 4. By using such a pumping combiner, the MM pumping light with a narrow frequency band output by the frequency separation unit 5 can be made to enter the core of the amplification medium as SM pumping light.

[0030] As described above, according to this embodiment, the number of parts can be reduced compared to the configuration of the fifth embodiment. In particular, in this embodiment, the frequency band of the MM pump light is narrowed by the frequency separator 5, so that the pump combiner has the role of converting the MM pump light into SM pump light. This makes it possible to omit the dedicated mode separator 2, unlike the first to fifth embodiments. In this embodiment, the coupler 32, the frequency separator 5, and the pump combiner of the amplifier 4 constitute an optical processing section that outputs at least N SM pump lights based on M MM pump lights. In this embodiment, the amplifier 4 can be considered to include an amplification medium but not to include a pump combiner, in correspondence with the fact that the pump combiner is considered to be a component of the optical processing section.

[0031] In the embodiment using the mode separation section 2, the number of modes separated by each mode separation section 2 is the same, but the number of modes separated may differ depending on the individual mode separation section 2. Similarly, in the embodiment using the frequency separation section 5, the number of frequencies separated by each frequency separation section 5 is the same, but the number of frequencies separated may differ depending on the individual frequency separation section 5. Also, in the fourth and fifth embodiments, the number of mode separation numbers 2 is set to be the same as the number of MM excitation light beams output by the entire frequency separation section 5, but a configuration in which the number of mode separation numbers 2 is set to be less than the number of MM excitation light beams output by the entire frequency separation section 5 may be used.

[0032] The above configuration can reduce the power consumption of optical amplifiers, which will contribute to Goal 9 of the United Nations Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0033] 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]

[0034] 1-1 to 1-M: pumping light source, 2-1 to 2-M: mode separation section, 31: coupler, 4-1 to 4-N: amplifier section

Claims

1. A pump light source that generates M multimode pump light beams (M is an integer equal to or greater than 1); an optical processor that outputs at least N (N is an integer equal to or greater than 1) single-mode pump light beams based on the M multi-mode pump light beams; N amplifier units; Equipped with An optical amplifier, wherein each of the N amplifying sections is core-pumped by one single-mode pump light among the at least N single-mode pump light.

2. 2. The optical amplifier according to claim 1, wherein each of the N amplifying sections includes an amplifying medium and a pump combiner that inputs the single mode pump light to a core of the amplifying medium.

3. The light processing section includes: a mode separation unit that separates the M number of multi-mode pump lights into a single mode, and outputs S number of single mode pump lights, the S being greater than the M number of single mode pump lights; a coupler that outputs the at least N single-mode pump light beams based on the S single-mode pump light beams from the mode separation unit; 2. The optical amplifier of claim 1, comprising:

4. The light processing section includes: a coupler for outputting P multi-mode pump light beams (P is an integer equal to or greater than 1) based on the M multi-mode pump light beams; a mode separation unit that outputs the at least N single-mode pump lights by mode-separating the output of the coupler; Equipped with 2. The optical amplifier according to claim 1, wherein when said M is 1, said P is 2 or more, and when said P is 1, said M is 2 or more.

5. The light processing section includes: a first coupler that outputs P multi-mode pump light beams (P is an integer equal to or greater than 1) based on the M multi-mode pump light beams; a mode separation unit that outputs S single-mode pump light beams, the S being greater than the P single-mode pump light beams, by mode-separating the output of the first coupler; a second coupler that outputs the at least N single-mode pump light beams based on the S single-mode pump light beams from the mode separation unit; Equipped with 2. The optical amplifier according to claim 1, wherein when said M is 1, said P is 2 or more, and when said P is 1, said M is 2 or more.

6. The light processing section includes: a frequency separation unit that separates the M number of multi-mode pump lights into S number of multi-mode pump lights, the S being greater than the M number of multi-mode pump lights; a mode separation unit that separates modes of the output of the frequency separation unit to output T single-mode pump light beams, the T being greater than the S single-mode pump light beams; a coupler that outputs the at least N single-mode pump light beams based on the T single-mode pump light beams from the mode separation unit; 2. The optical amplifier of claim 1, comprising:

7. The light processing section includes: a first coupler that outputs P multi-mode pump light beams (P is an integer equal to or greater than 1) based on the M multi-mode pump light beams; a frequency separation unit that separates the output of the first coupler by frequency separation to output S multi-mode pump light beams, the S being greater than P; a mode separation unit that outputs T single-mode pump light beams, the T being greater than the S single-mode pump light beams, by mode-separating the output of the frequency separation unit; a second coupler that outputs the at least N single-mode pump light beams based on the T single-mode pump light beams from the mode separation unit; Equipped with 2. The optical amplifier according to claim 1, wherein when said M is 1, said P is 2 or more, and when said P is 1, said M is 2 or more.

8. The light processing section includes: a coupler for outputting P multimode pump light beams (P is an integer equal to or greater than 1) based on the M multimode pump light beams; a frequency separation unit that outputs at least N multimode pump lights by frequency separation of the output of the coupler; N excitation combiners; and Equipped with Each of the N pump combiners converts one multi-mode pump light of the at least N multi-mode pump lights into the one single-mode pump light to core-pump one amplifier unit of the N amplifier units; 2. The optical amplifier according to claim 1, wherein when said M is 1, said P is 2 or more, and when said P is 1, said M is 2 or more.

9. 9. The optical amplifier according to claim 8, wherein each of the N pumping combiners has a structure in which a core of a multimode optical fiber through which the one multimode pumping light propagates and a core of an amplifying medium of the amplifying section are brought into close proximity.

10. 10. The optical amplifier according to claim 2, wherein the amplification medium is a rare-earth doped optical fiber.

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