Multi-core pumping system for optical amplifier

Abstract

The invention relates to a multi-core pumping system for an optical amplifier. In some implementations, an optical amplifier system includes a pump system comprising: a pump laser source configured to output multimode pump light at a first wavelength; and a multi-core fiber laser having an input and an output, the input optically coupled to the pump laser source. The multi-core fiber laser may include a multi-core active fiber having a plurality of cores to convert the multi-mode pump light to a plurality of single-mode pump light outputs at one or more second wavelengths, where the plurality of cores have respective laser cavities defined by a fiber grating on each of the plurality of cores. The optical amplifier system may include an optical fiber amplifier optically coupled to a pumping system, the optical fiber amplifier including a plurality of amplifier components in one or more active optical fibers to be pumped by respective ones of a plurality of cores of a multi-core active optical fiber.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to U.S. Provisional Patent Application No. 63 / 553,729, filed on February 15, 2024, and entitled “MULTI-CORE O-BANDAMPLIFIER.” The disclosure of that prior application is considered a part of and incorporated by reference into this patent application. Technical Field

[0003] The present disclosure generally relates to optical amplifiers and multi-core pumping systems for optical amplifiers. Background Art

[0004] An optical amplifier is a device that receives signal light and generates amplified signal light (i.e., signal light with relatively high optical power). Typically, an optical amplifier provides optical amplification using a so-called gain medium that is "pumped" (i.e., supplied with energy) by a source such as a pump laser. In some cases, an optical amplifier can utilize an optical fiber as the gain medium (such a device may be referred to as a fiber amplifier). In this case, the gain medium may be a glass fiber doped with rare earth ions such as erbium, neodymium, ytterbium, praseodymium, or thulium. Such an optical fiber may be referred to as an active fiber. In operation, the signal light propagates through the active fiber along with the pump light, and the active fiber outputs the amplified signal light generated by the signal light and the pump light. Summary of the Invention

[0005] In some implementations, an optical system includes a pump system comprising: a pump laser source configured to output multimode pump light at a first wavelength; and a multi-core fiber laser having an input end and an output end, the input end optically coupled to the pump laser source. The multi-core fiber laser may include a multi-core active fiber having multiple cores to convert the multimode pump light into multiple single-mode pump light outputs at one or more second wavelengths, wherein the multiple cores have corresponding laser cavities defined by fiber gratings on each of the multiple cores. The optical system may include a signal combiner optically coupled to the output end of the multi-core fiber laser, the signal combiner configured to combine the single-mode pump light output with the signal light. The optical system may include a fiber amplifier optically coupled to the output of the signal combiner, the fiber amplifier including multiple amplifier components in one or more active fibers, the multiple amplifier components to be pumped by corresponding cores in the multiple cores of the multi-core active fiber.

[0006] In some implementations, a pump system includes: a pump laser source configured to output multimode pump light at a first wavelength; and a multi-core fiber laser having an input end and an output end, the input end optically coupled to the pump laser source. The multi-core fiber laser may include a multi-core active fiber having multiple cores to convert the multimode pump light into multiple single-mode pump light outputs at one or more second wavelengths, wherein the multiple cores have corresponding laser cavities defined by fiber gratings on each of the multiple cores.

[0007] In some implementations, an optical amplifier system includes a pump system comprising: a pump laser source configured to output multimode pump light at a first wavelength; and a multi-core fiber laser having an input and an output, the input optically coupled to the pump laser source. The multi-core fiber laser may include a multi-core active fiber having multiple cores to convert the multimode pump light into multiple single-mode pump light outputs at one or more second wavelengths, wherein the multiple cores have respective laser cavities defined by fiber gratings on each of the multiple cores. The optical amplifier system may include a fiber amplifier optically coupled to the pump system, including multiple amplifier components in one or more active fibers, the multiple amplifier components to be pumped by respective cores in the multiple cores of the multi-core active fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagram of an example optical system.

[0009] Figure 2 is a diagram of an example optical system.

[0010] Figure 3 is a diagram showing an example graph of the relationship between laser power and the number of amplifier rails. DETAILED DESCRIPTION

[0011] The following detailed description of example implementations refers to the accompanying drawings, in which the same reference numbers in different drawings may identify the same or similar elements.

[0012] Fiber amplifiers are used in optical communication systems to increase the intensity of optical signals, enabling long-distance transmission. Some fiber amplifiers provide original-band (O-band) amplification. O-band amplifiers are desirable due to their ability to amplify across a wide spectrum and their application in data center transmission.

[0013] Fiber amplifiers can be optically pumped using one or more optical pump sources, such as one or more laser diodes. Typically, a single pump laser source is used to pump a single fiber amplifier. Consequently, multi-rail amplifiers (e.g., those supporting high-capacity optical communication networks) may use a separate pump laser source for each rail (e.g., for each fiber amplifier) and therefore have high power requirements. Furthermore, fiber amplifiers, such as O-band amplifiers, may use extensive lengths of active fiber and are therefore associated with low power efficiency and high cost per fiber.

[0014] Some implementations described herein relate to a pumping system for an optical amplifier, the pumping system comprising a pump laser source and a multi-core fiber laser. The pump laser source can be configured to output multimode pump light at a first wavelength (e.g., 915 nanometers (nm)) to the multi-core fiber laser. The multi-core fiber laser can include an active fiber having multiple active cores. Each of the active cores can include a laser cavity defined by a fiber grating. Thus, the multi-core fiber laser can convert the multimode pump light of the pump laser source into multiple single-mode pump lasers at one or more second wavelengths (e.g., 1150 nm). The multiple pump lasers can in turn pump multiple fiber amplifiers (e.g., multiple cores of a multi-core active fiber or multiple single-core active fibers) or multiple stages of a fiber amplifier.

[0015] By generating multiple pump lasers from a single pump laser source, the pump system reduces the laser power required to pump multiple fiber amplifiers or multiple stages of a fiber amplifier. Consequently, the pump system offers higher power efficiency per fiber and lower cost. Furthermore, an optical amplifier system including the pump system can have reduced complexity by eliminating multiple pump laser sources. For example, an optical amplifier system can include multiple amplifier components using only a single set of pump components.

[0016] Figure 1 is a diagram of an example optical system 100. Figure 1 As shown in FIG, the optical system 100 may include an optical amplifier 102 and a pump system 104. For example, the optical system 100 may be an optical amplifier system.

[0017] The optical amplifier 102 can provide optical amplification in an optical communication band, such as the O-band. The optical amplifier 102 can include a gain medium to be optically pumped to provide optical amplification. The optical amplifier 102 can be a fiber amplifier. In some implementations, the optical amplifier 102 can be another type of optical amplifier that is optically pumped, such as an optical parametric amplifier or a Raman amplifier, among other examples.

[0018] The optical amplifier 102 may include one or more active fibers 106. For example, the optical amplifier 102 may include a plurality of amplifier components 108 in the one or more active fibers 106. As an example, the optical amplifier 102 may include one or more multi-core active fibers 106, and / or may include a plurality of single-core active fibers 106. The active fiber(s) 106 of the optical amplifier 102 may include one or more rare earth doped fibers (RDFs). For example, the active fiber(s) 106 of the optical amplifier 102 may include one or more bismuth doped fibers (BDFs), which may be suitable for amplification in the O-band.

[0019] As shown, the plurality of amplifier components 108 may include multiple cores of a multi-core active optical fiber 106 (e.g., each core is an amplifier component 108). For example, the plurality of amplifier components 108 may be in a single multi-core active optical fiber 106. In some implementations, the plurality of amplifier components 108 may include multiple single-core active optical fibers 106 (e.g., each active optical fiber 106 is an amplifier component 108). For example, the plurality of amplifier components 108 may be in multiple single-core active optical fibers 106 arranged in parallel. Figure 2 As further described, in some implementations, the plurality of amplifier components 108 may include a plurality of amplifier stages (eg, each amplifier stage is an amplifier component 108 ). For example, each amplifier stage may include a single-core active fiber 106 or a multi-core active fiber 106 .

[0020] As shown, the input end of the optical amplifier 102 can be optically coupled to one or more input fibers 110, which are configured to carry signal light (e.g., signal light in the O-band). The output end of the optical amplifier 102 can be optically coupled to one or more output fibers 112, which are configured to carry amplified signal light from the optical amplifier 102. The number of input fibers 110 and the number of output fibers 112 can match the number of amplifier rails (e.g., parallel amplification paths) of the optical amplifier 102. For example, Figure 1 As shown in FIG, the optical amplifier 102 has three amplifier rails, and the optical system 100 includes three input fibers 110 and three output fibers 112.

[0021] The pump system 104 is configured to provide optical pumping for the optical amplifier 102. The pump system 104 may include a pump laser source 114 and a multi-core fiber laser 116. The pump laser source 114 may be configured to output multimode pump light. The pump laser source 114 may include a laser diode. The laser diode may be edge-emitting, vertically emitting, or the like. The laser diode may have a wavelength of 915 nanometers (nm) or another wavelength.

[0022] The multi-core fiber laser 116 has an input end optically coupled to the pump laser source 114 and an output end optically coupled to the optical amplifier 102. The multi-core fiber laser 116 includes a multi-core active fiber 118 having a plurality of fiber cores 120. The multi-core active fiber 118 may include an RDF. For example, the multi-core active fiber 118 may include an ytterbium-doped fiber (YDF), which may provide the multi-core fiber laser 116 with a wavelength(s) suitable for amplification in the O-band. Thus, the multi-core active fiber 118 may have a first doping (e.g., having a first dopant ion, such as ytterbium ions), and the active fiber(s) 106 of the optical amplifier 102 may have a second doping different from the first doping (e.g., having a second dopant ion, such as bismuth ions). In some implementations, the dopants or codopants used in the multi-core active fiber 118 can be manipulated to change the wavelength(s) of the multi-core fiber laser 116 to support amplification in optical communication bands other than the O-band.

[0023] The pump laser source 114 can be configured to cladding pump the multi-core active fiber 118, thereby pumping all of the fiber cores 120 (e.g., the cladding of the multi-core active fiber 118 has a geometry that couples pump light into each of the fiber cores 120). In some implementations, the multi-core fiber laser 116 can employ multiple single-core active fibers instead of the multi-core active fiber 118, and each of the multiple single-core active fibers can be pumped by a corresponding single-mode pump laser source. The fiber cores 120 can have respective laser cavities defined by fiber gratings 122 (e.g., fiber Bragg gratings (FBGs)) on each of the fiber cores 120. For example, the fiber gratings 122 can be written on the individual fiber cores 120. Thus, the multi-core active fiber 118 can generate multiple lasers (e.g., where the number of lasers corresponds to the number of fiber cores 120). In some implementations, the fiber gratings 122 of two or more optical fiber cores 120 may have different configurations to generate laser light with different wavelengths, such as by combining Figure 2 Further described.

[0024] The multimode pump light of the pump laser source 114 can have a first wavelength (e.g., 915 nm), and the plurality of optical fiber cores 120 can be configured to convert the multimode pump light into a plurality of single-mode pump light outputs at one or more second wavelengths (e.g., 1150 nm). In this way, the multi-core fiber laser 116 enables customization of the output wavelength of the pump system 104 (e.g., when the pump laser source 114 itself cannot generate the output wavelength). In addition, the multi-core fiber laser 116 generates multiple pump lasers from a single active fiber and from a single pump laser input, thereby improving the efficiency of the optical system 100.

[0025] The multi-core fiber laser 116 is configured to pump each of the plurality of amplifier components 108 of the optical amplifier 102 using a corresponding pump laser light generated by the multi-core fiber laser 116. For example, the plurality of amplifier components 108 can be pumped by a corresponding fiber core 120 of the multi-core active fiber 118 of the multi-core fiber laser 116 (e.g., the number of amplifier components 108 corresponds to the number of fiber cores 120). As an example, the fiber core 120 can be configured to pump a corresponding active core of the multi-core active fiber 106 of the optical amplifier 102, to pump a corresponding single-core active fiber 106 of the optical amplifier 102, or to pump a corresponding amplifier stage of the optical amplifier 102 (e.g., to pump the active fiber 106 of the corresponding amplifier stage).

[0026] The optical system 100 may include a signal combiner 124 optically coupled to an output end of the multi-core fiber laser 116 (e.g., directly or indirectly via an optical device 126 such as a mirror), an input fiber 110, and an optical amplifier 102 (e.g., the optical amplifier 102 is optically coupled to the output of the signal combiner 124). The signal combiner 124 may be configured to combine single-mode pump light output by each of the fiber cores 120 of the multi-core fiber laser 116 with signal light in the input fiber 110, and input the combined light into the optical amplifier 102. In some implementations, the signal combiner 124 is a wavelength division multiplexer (WDM).

[0027] While the above description is in terms of optically pumped optical amplifiers, in some implementations, the techniques and apparatus described herein can be applied in conjunction with optically pumping any optical fiber (eg, an optical oscillator fiber), optically pumping optical couplers, and the like.

[0028] As indicated above, provide Figure 1 As an example. Other examples can be related to Figure 1 What is described is different.

[0029] Figure 2is a diagram of an example optical system 200. Figure 2 As shown in FIG, an optical system 200 may include an optical amplifier 102, a pump system 104, and a plurality of signal combiners 124. For example, the optical system 200 may be an optical amplifier system. In the optical system 200, the optical amplifier 102 is shown as having a plurality of amplifier stages 202 (shown as a first amplifier stage 202a and a second amplifier stage 202b) connected in series, and each amplifier stage 202 includes an active optical fiber 106.

[0030] As shown, the first fiber core 120a of the multi-core active fiber 118 of the multi-core fiber laser 116 can be optically coupled to the first amplifier stage 202a, and the second fiber core 120b can be optically coupled to the second amplifier stage 202b. For example, the first signal combiner 124a can be optically coupled to the first fiber core 120a, the input fiber 110 ( Figure 2 1 ), and a first amplifier stage 202a (e.g., the first amplifier stage 202a is optically coupled to the output of the first signal combiner 124a). The first signal combiner 124a can be configured to combine the pump light output by the first optical fiber core 120a with the signal light in the input optical fiber 110, and input the combined light into the first amplifier stage 202a. The second signal combiner 124b can be optically coupled to the second optical fiber core 120b, the output of the first amplifier stage 202a, and the second amplifier stage 202b (e.g., the second amplifier stage 202b is optically coupled to the output of the second signal combiner 124b). The second signal combiner 124b can be configured to combine the pump light output by the second optical fiber core 120b with the amplified signal light output by the first amplifier stage 202a, and input the combined light into the second amplifier stage 202b.

[0031] In some implementations, the fiber gratings 122 on each of the fiber cores 120 can be configured with the corresponding wavelength of the fiber core 120. For example, the fiber gratings 122 for different fiber cores 120 can have different configurations (e.g., different periodicities) from each other. As shown, the fiber grating 122a of the first fiber core 120a can have a different configuration than the fiber grating 122b of the second fiber core 120b. Therefore, due to the different configurations of the fiber gratings 122, the pump laser of the first fiber core 120a can have a first wavelength, and the pump laser of the second fiber core 120b can have a second wavelength.

[0032] In some implementations, a first wavelength associated with the first optical fiber core 120a can produce a first gain peak (shown as example Gain Peak 1) in the first amplifier stage 202a. A second wavelength associated with the second optical fiber core 120b can produce a second gain peak (shown as example Gain Peak 2) in the second amplifier stage 202b that is different from the first gain peak. For example, the first wavelength and the second wavelength can be configured such that the first gain peak and the second gain peak, when combined, produce an overall gain spectrum (shown as Overall Gain Spectrum) that is flatter than the first wavelength or the second wavelength alone.

[0033] As indicated above, provide Figure 2 As an example. Other examples can be related to Figure 2 What is described is different.

[0034] Figure 3 is a graph illustrating an example graph 300 showing the relationship between laser power and the number of amplifier rails. As shown, as the number of amplifier rails increases, the laser power required to produce amplification also increases.

[0035] The dashed line shows the relationship between laser power and the number of amplifier tracks for a system that uses an individual pump laser source for each amplifier track. For example, ten pump laser sources would be used to pump ten amplifier tracks. The solid line shows the relationship between laser power and the number of amplifier tracks for an optical system that uses a multi-core fiber laser, as described herein. As shown, at higher track counts, the laser power required to generate amplification is lower for the system that uses a multi-core fiber laser than for the system that uses an individual pump laser source for each amplifier track.

[0036] As indicated above, provide Figure 3 As an example. Other examples can be related to Figure 3 What is described is different.

[0037] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit the implementations to the precise forms disclosed. Modifications and variations may be made in light of the foregoing disclosure or may be acquired from practice of the implementations. Furthermore, any implementations described herein may be combined, unless the foregoing disclosure explicitly provides reasons why one or more implementations may not be combined.

[0038] Even though particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of the various implementations. In fact, many of these features may be combined in ways not specifically recited in the claims and / or disclosed in the specification. Although each dependent claim listed below may be directly dependent on only one claim, the disclosure of the various implementations includes each dependent claim in combination with every other claim in the claim group. As used herein, a phrase referring to "at least one" of a list of items refers to any combination of those items, including single members. As an example, "at least one of: a, b, or c" is intended to cover a, b, c, ab, ac, bc, and abc, as well as any combination with multiple identical items.

[0039] As used herein, the elements, actions or instructions should not be interpreted as being critical or necessary unless explicitly described as such. Moreover, as used herein, the words "one" and "an" are intended to include one or more items and can be used interchangeably with "one or more". Furthermore, as used herein, the word "the" is intended to include one or more items mentioned in conjunction with the word "the", and can be used interchangeably with "the one or more". Furthermore, as used herein, the term "set" is intended to include one or more items (e.g., related items, unrelated items, or a combination of related items and unrelated items), and can be used interchangeably with "one or more". In the case of being intended to only one item, the phrase "only one" or similar language is used. Furthermore, as used herein, the terms "having", "containing", "having" etc. are intended to be open terms. Furthermore, the phrase "based on" is intended to mean "at least partially based on", unless otherwise explicitly stated. Furthermore, as used herein, the term "or" is intended to be inclusive when used in a series, and can be used interchangeably with "and / or", unless otherwise explicitly stated (e.g., if used in combination with "either" or "only one of").

Claims

1. An optical system comprising: A pumping system comprising: a pump laser source configured to output multimode pump light at a first wavelength; and A multi-core fiber laser having an input end and an output end, wherein the input end is optically coupled to the pump laser source, and the multi-core fiber laser comprises: a multi-core active optical fiber having multiple cores to convert the multi-mode pump light into multiple single-mode pump light outputs at one or more second wavelengths, wherein the plurality of cores have respective laser cavities defined by fiber gratings on each of the plurality of cores; a signal combiner optically coupled to the output end of the multi-core fiber laser and configured to combine the single-mode pump light output with a signal light; and A fiber amplifier, optically coupled to the output of the signal combiner, comprises a plurality of amplifier components in one or more active optical fibers, the plurality of amplifier components to be pumped by respective ones of the plurality of cores of the multi-core active optical fiber. 2 . The optical system of claim 1 , wherein the fiber grating on each of the plurality of cores configures the corresponding wavelength of the plurality of cores.

3. The optical system of claim 1, wherein the plurality of amplifier components comprises a plurality of cores of a multi-core active optical fiber of the fiber amplifier.

4. The optical system of claim 1, wherein the plurality of amplifier components comprises a plurality of single-core active optical fibers of the fiber amplifier.

5. The optical system of claim 1, wherein the plurality of amplifier components comprises a plurality of amplifier stages of the fiber amplifier.

6. The optical system of claim 5, wherein the signal combiner is a first signal combiner and the optical system comprises a second signal combiner, wherein the first signal combiner is optically coupled to a first core of the plurality of cores and to an input of a first amplifier stage of the plurality of amplifier stages, and The second signal combiner is optically coupled to a second core of the plurality of cores and to an input of a second amplifier stage of the plurality of amplifier stages connected in series with the first amplifier stage.

7. The optical system of claim 6, wherein a first wavelength associated with the first core produces a first gain peak in the first amplifier stage, and Wherein a second wavelength associated with the second core produces a second gain peak in the second amplifier stage that is different from the first gain peak.

8. The optical system of claim 1 , wherein the multi-core active optical fiber has a first doping, and wherein the one or more active optical fibers have a second doping different from the first doping.

9. The optical system of claim 1, wherein the multi-core active optical fiber is an ytterbium-doped optical fiber.

10. The optical system of claim 1, wherein the one or more active optical fibers are one or more bismuth-doped optical fibers.

11. The optical system of claim 1 , wherein the signal combiner is a wavelength division multiplexer.

12. A pumping system comprising: a pump laser source configured to output multimode pump light at a first wavelength; as well as A multi-core fiber laser having an input end and an output end, wherein the input end is optically coupled to the pump laser source, and the multi-core fiber laser comprises: a multi-core active optical fiber having multiple cores to convert the multi-mode pump light into multiple single-mode pump light outputs at one or more second wavelengths, wherein the plurality of cores have respective laser cavities defined by fiber gratings on each of the plurality of cores.

13. The pumping system of claim 12, wherein the first wavelength is 950 nanometers and the one or more second wavelengths include a wavelength of 1150 nanometers.

14. The pumping system of claim 12, wherein the multi-core active optical fiber is an ytterbium-doped optical fiber.

15. The pump system of claim 12, wherein the one or more active optical fibers are one or more bismuth-doped optical fibers.

16. The pumping system of claim 12, wherein the fiber grating on each of the plurality of cores is configured to a corresponding wavelength of the plurality of cores.

17. An optical amplifier system comprising: A pumping system comprising: a pump laser source configured to output multimode pump light at a first wavelength; and A multi-core fiber laser having an input end and an output end, wherein the input end is optically coupled to the pump laser source, and the multi-core fiber laser comprises: a multi-core active optical fiber having multiple cores to convert the multi-mode pump light into multiple single-mode pump light outputs at one or more second wavelengths, wherein the plurality of cores have respective laser cavities defined by fiber gratings on each of the plurality of cores; and A fiber amplifier, optically coupled to the pumping system, comprises a plurality of amplifier components in one or more active optical fibers, the plurality of amplifier components to be pumped by respective ones of the plurality of cores of the multi-core active optical fiber.

18. The optical amplifier system of claim 17, wherein the plurality of amplifier components comprises a plurality of cores of a multi-core active optical fiber of the fiber amplifier.

19. The optical amplifier system of claim 17, wherein the plurality of amplifier components comprises a plurality of single-core active optical fibers of the fiber amplifier.

20. The optical amplifier system of claim 17, wherein the plurality of amplifier components comprises a plurality of amplifier stages of the fiber amplifier.

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