WO2023109805A1 - 一种光纤放大器和放大光信号的方法 - Google Patents

一种光纤放大器和放大光信号的方法 Download PDF

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WO2023109805A1
WO2023109805A1 PCT/CN2022/138667 CN2022138667W WO2023109805A1 WO 2023109805 A1 WO2023109805 A1 WO 2023109805A1 CN 2022138667 W CN2022138667 W CN 2022138667W WO 2023109805 A1 WO2023109805 A1 WO 2023109805A1
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fiber
pump laser
optical
mode
optical signal
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French (fr)
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刘沛
张楷
吴波
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06754—Fibre amplifiers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094042—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a fibre laser
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1601—Solid materials characterised by an active (lasing) ion
    • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
    • H01S3/1608—Solid materials characterised by an active (lasing) ion rare earth erbium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/1601—Solid materials characterised by an active (lasing) ion
    • H01S3/1603—Solid materials characterised by an active (lasing) ion rare earth
    • H01S3/1618—Solid materials characterised by an active (lasing) ion rare earth ytterbium
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/29—Repeaters
    • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
    • H04B10/2912—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/0675—Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
    • H01S3/094007—Cladding pumping, i.e. pump light propagating in a clad surrounding the active core
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094069—Multi-mode pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
    • H01S3/09415—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping

Definitions

  • the present application relates to the technical field of optical transmission, and more particularly, relates to an optical fiber amplifier and a method for amplifying an optical signal.
  • the optical fiber amplifier's performance and bandwidth have an important impact on the overall performance of the optical fiber communication system, and its cost is the key factor that determines whether the overall system can adapt to more application scenarios. Therefore, , low-cost optical fiber amplifiers have become a research hotspot in the industry. Among them, reducing the cost of pump lasers in fiber amplifiers is the key to realizing low-cost fiber amplifiers.
  • the pump lasers of telecom-grade optical fiber amplifiers are mainly single-mode pumps (single-mode pumps, SMPs), which can directly output single-transverse-mode laser beams.
  • SMPs single-mode pumps
  • the laser beams have a small spot size and can be coupled efficiently
  • EDF Er-doped fiber
  • the output laser power of SMP is limited, and its cost rises sharply with the increase of power.
  • the present application provides an optical fiber amplifier and a method for amplifying an optical signal, which can reduce the pumping cost and increase the saturated output optical power of the optical amplifier.
  • an optical fiber amplifier including: a multimode pumping unit for generating multimode pumping laser light; an input unit for inputting an input optical signal and multimode pumping laser light into the first optical path, the first An optical path belongs to the resonant amplifying unit; the resonant amplifying unit is used to generate a single-mode pumping laser in the first wavelength range according to the multi-mode pumping laser, and repeatedly oscillates the single-mode pumping laser in the first wavelength range in the first optical path, The single-mode pump laser in the first wavelength range amplifies the input optical signal; the output unit is used to output the amplified input optical signal.
  • the optical fiber amplifier of the present application by converting the multimode pump laser generated by the multimode pump into a single-mode pump laser, a multimode pump with higher output power and lower cost can be used instead of a multimode pump with lower output power and lower cost.
  • the high single-mode pump helps to reduce the pumping cost and increase the saturation output power of the optical amplifier.
  • the wavelength range of the multimode pump laser is 880 to 980 nm, and the first wavelength range is 970 to 1030 nm.
  • the optical fiber amplifier provided in this application, it can generate single-mode pump laser light with a wavelength range of 970 to 1030nm, which is used to amplify the input optical signal.
  • the above-mentioned first optical path includes: a double-clad ytterbium-doped optical fiber, used to absorb multimode pump laser light, and generate and amplify single-mode pump light in the first wavelength range Laser; erbium-doped optical fiber, used to absorb single-mode pump laser light in the first wavelength range, and amplify the input optical signal.
  • the single-mode erbium-doped optical fiber in the existing telecommunication-grade optical fiber amplifier can be directly multiplexed, and its workable spectral bandwidth is guaranteed to be consistent with that of existing products, which helps to reduce pumping costs.
  • the above-mentioned resonant amplifying unit further includes a cladding pump stripper, configured to strip the unabsorbed multimode pump laser light from the double-clad ytterbium-doped fiber.
  • the cladding pump stripper is located between the erbium-doped fiber and the double-clad ytterbium-doped fiber.
  • the resonant amplifying unit includes a resonant cavity, and the resonant amplifying unit repeatedly oscillates the single-mode pump laser in the first wavelength range in the first optical path through the resonant cavity.
  • the single-mode pump laser can oscillate in the resonant cavity and repeatedly pass through the erbium-doped fiber, which can greatly improve the absorption of the erbium-doped fiber to the single-mode pump laser, Thereby improving the pump absorption coefficient.
  • the resonant cavity includes a first fiber Bragg grating and a second fiber Bragg grating, and the first fiber Bragg grating and the second fiber Bragg grating have a single-mode pump laser in the first wavelength range
  • the reflectivity is greater than the first threshold
  • the transmittance of the first fiber grating and the second fiber grating to the amplified input optical signal is greater than the second threshold.
  • the first threshold may be 90%
  • the second threshold may be 90%.
  • the first fiber grating and the second fiber grating have relatively high reflectivity (for example, reflectivity ⁇ 90%) to the single-mode pump laser in the first wavelength range, so that the single-mode pump laser in the first wavelength range can be Repeatedly oscillating in the resonant cavity and repeatedly passing through the erbium-doped fiber can greatly improve the absorption of the single-mode pump laser by the erbium-doped fiber, thereby improving the pump absorption coefficient.
  • the amplified input optical signal has a high transmittance (for example, transmittance ⁇ 90%), so that the input optical signal can be smoothly output after being amplified in the resonant cavity, and the NF performance of the amplified optical signal is guaranteed.
  • the wavelength difference between the first fiber Bragg grating and the second fiber Bragg grating is smaller than the reflection bandwidth of the first fiber Bragg grating and the second fiber Bragg grating.
  • the input unit further includes a first wavelength division multiplexer, configured to couple the input optical signal and the multimode pump laser light into the first optical path.
  • the output unit further includes a second wavelength division multiplexer, configured to separate and output the amplified input optical signal from the first optical path.
  • the output unit further includes a gain flattening filter and/or an adjustable optical attenuator.
  • the erbium-doped fiber is any of the following: single-mode erbium-doped fiber, large-mode-field erbium-doped fiber, and double-clad erbium-doped fiber.
  • a method for amplifying an optical signal including: receiving an input optical signal and inputting the input optical signal into a first optical path; generating a multi-mode pump laser; generating a first wavelength according to the multi-mode pump laser
  • the single-mode pump laser in the first wavelength range repeatedly oscillates the single-mode pump laser in the first wavelength range in the first optical path, so that the single-mode pump laser in the first wavelength range amplifies the input optical signal; the amplified input light is output Signal.
  • using a multi-mode pump instead of a single-mode pump can reduce the pumping cost and increase the saturation output power of the optical amplifier.
  • the wavelength range of the multimode pump laser is 880 to 980 nm, and the first wavelength range is 970 to 1030 nm.
  • the optical fiber amplifier provided in this application, it can generate single-mode pump laser light with a wavelength range of 970 to 1030nm for amplifying input optical signals. It has good NF performance and can meet the requirements of telecom-grade optical fiber amplifiers.
  • the above-mentioned first optical path includes a double-clad ytterbium-doped optical fiber, which is used to absorb multimode pump laser light, and generate and amplify single-mode pump laser light in the first wavelength range ;
  • the erbium-doped fiber is used to absorb the single-mode pump laser in the first wavelength range and amplify the input optical signal.
  • the erbium-doped fiber is any of the following: single-mode erbium-doped fiber, large-mode-field erbium-doped fiber, and double-clad erbium-doped fiber.
  • an optical fiber communication system in a third aspect, includes: an optical amplifier site, where the optical amplifier site includes the optical fiber amplifier as provided in the first aspect.
  • a device for amplifying an optical signal is provided, and the device is used to implement the method of the second aspect above.
  • the apparatus may include a unit and/or module for executing the method provided by the second aspect, such as a processing module and/or a transceiver module.
  • the device is an amplifier.
  • the transceiver module may be a transceiver, or an input/output interface;
  • the processing module may be a processor.
  • the device is a chip, a chip system or a circuit for amplifying an optical signal.
  • the transceiver module unit may be an input/output interface, an interface circuit, an output circuit, an input circuit, a pin or a Related circuits, etc.;
  • the processing module may be a processor, a processing circuit, or a logic circuit, etc.
  • the above-mentioned transceiver may be a transceiver circuit.
  • the above input/output interface may be an input/output circuit.
  • Fig. 1 is a structural schematic diagram of a carrier-grade optical fiber amplifier.
  • Fig. 2 is a schematic diagram of a single-mode laser signal amplified by a multi-mode laser.
  • Fig. 3 is a schematic structural diagram of a single-mode fiber amplifier.
  • Fig. 4 is a schematic structural diagram of an example of the optical fiber amplifier provided by the present application.
  • Fig. 5 is a schematic structural diagram of a specific example of the fiber amplifier provided in the present application.
  • Fig. 6 is a schematic structural diagram of another specific example of the fiber amplifier provided in the present application.
  • Fig. 7 is a structural schematic diagram of an example of the multi-stage structure of the optical fiber amplifier provided by the present application.
  • Fig. 8 is a structural schematic diagram of an example of the multi-group array structure of the optical fiber amplifier provided by the present application.
  • Fig. 9 is a schematic flowchart of an example of a method for amplifying an optical signal provided by the present application.
  • the technical solutions of the embodiments of the present application can be applied to optical fiber communication networks.
  • the technical solutions of the embodiments of the present application can be used in optical fiber amplifiers in optical fiber communication networks.
  • the optical fiber amplifiers are mainly located at optical amplifier sites and optical amplifiers in optical fiber communication networks. network element.
  • the technical solutions of the embodiments of the present application can be used to realize an optical fiber amplifier composed of multi-core optical fibers.
  • FIG. 1 shows a schematic structural diagram of a carrier-grade optical fiber amplifier 100 .
  • the optical fiber amplifier 100 includes an isolator (isolator, ISO) 101, a wavelength division multiplexer (wavelength division multiplexer, WDM) 102, an erbium-doped fiber (Er-doped fiber, EDF), an isolator 104 and a single-mode pump 107.
  • the fiber amplifier 100 may further include a gain flattening filter 105 and an adjustable optical attenuator 106 .
  • the single-mode pump SMP107 as the pump laser of the fiber amplifier 100, can directly output a single transverse mode laser beam, has a small spot size, and can be efficiently coupled into a single-mode fiber, and then through wavelength division multiplexing technology, so as to realize Pumping of single-mode EDF.
  • the optical fiber amplifier's performance and bandwidth have an important impact on the overall performance of the optical fiber communication system, and its cost is the key factor that determines whether the overall system can adapt to more application scenarios. Therefore, , low-cost optical fiber amplifiers have become a research hotspot in the industry. Among them, reducing the cost of pump lasers in fiber amplifiers is the key to realizing low-cost fiber amplifiers.
  • MMP does not have the limitation of single-mode conditions, and its output power is much higher than that of SMP. It can also achieve an output power of up to kilowatts through external beam combining means, and the production process of MMP is simple and low in cost. However, the MMP output spot size and divergence angle are relatively large, so it is difficult to directly couple into the single-mode fiber, and it is impossible to pump the EDF through the wavelength division multiplexing technology.
  • a known technology can reduce the cost of pumping by using cladding pumping in combination with double-clad doped fibers.
  • the multi-mode pump (multi-mode pump, MMP) propagates in the inner cladding of the double-clad fiber by coupling, while the single-mode signal laser to be amplified propagates in the core of the double-clad fiber. Since the inner cladding and the core of the double-clad fiber are coaxial, the multimode laser in the inner cladding will pass through the core with a certain probability during axial propagation, pumping the rare earth ions in the core to the upper energy level, thereby Realize the amplification of single-mode signal laser by multi-mode pumping.
  • the probability of MMP passing through the core is very low, approximately equal to the ratio of the cross-sectional area of the core to the inner cladding (less than 1%), so this technology will greatly reduce the equivalent absorption coefficient of the pump .
  • the equivalent coefficient of EDF is less than 0.05dB/m, that is, the required fiber length is increased by more than 100 times, and the cost is greatly increased.
  • the upper energy level inversion rate of EDF is lower, and the noise figure (noise figure, NF) performance is greatly reduced.
  • this technology can only be applied to doped fibers such as erbium-ytterbium co-doped fibers that have a higher pump absorption coefficient.
  • This technology is often used in community antenna television (CATV) at present, but cannot be applied to carrier-grade optical fiber amplifiers.
  • CATV community antenna television
  • Fig. 3 shows a schematic diagram of the mechanism of a single-mode fiber amplifier.
  • MMP constructs a single-mode fiber amplifier through the cladding pumping technology to realize the generation or amplification of the single-mode pump laser, and the amplified single-mode pump laser is regenerated
  • the rare earth ions are pumped through the WDM coupling to the fiber amplifier, so as to realize the amplification of the single-mode laser signal.
  • the commonly used method of this technology is to generate single-mode 101xnm or 153xnm fiber laser through cladding pumping as the pumping source of the subsequent fiber amplifier.
  • the absorption coefficient of EDF at 1018nm is about 0.3dB/m.
  • Multi-mode pumps do not have single-mode conditions, and their output power is much higher than that of single-mode pumps. They can also achieve kilowatt-level output power through external beam combining methods.
  • the production process of multi-mode pumps is simple and low-cost. However, the output spot size and divergence angle of the multimode pump are relatively large, and it is difficult to directly couple into the single-mode fiber, so it is impossible to pump the EDF through the wavelength division multiplexing technology.
  • the present application proposes a fiber amplifier, hoping to use a multi-mode pump instead of a single-mode pump, thereby reducing the pumping cost and increasing the saturated output power of the optical radiation.
  • Fig. 4 is a schematic structural diagram of an example of the optical fiber amplifier provided by the present application.
  • the fiber amplifier 400 includes a multimode pump unit 410 , an input unit 420 , a resonant amplifier unit 430 and an output unit 450 .
  • the multimode pumping unit 410 is used to generate multimode pump laser light;
  • the input unit 420 is used to input the input optical signal and multimode pump laser light into the first optical path 440, and the first optical path 440 belongs to the resonant amplifier unit 430
  • the resonant amplifying unit 430 is used to generate the single-mode pump laser in the first wavelength range according to the multi-mode pump laser, and repeatedly oscillates the single-mode pump laser in the first wavelength range in the first optical path, so that the first wavelength
  • the single-mode pump laser in the range amplifies the input optical signal;
  • the output unit 450 is used to output the amplified input optical signal.
  • the input optical signal can be the transmission optical signal in the previous optical fiber link, or the optical signal directly output by the laser; the output optical signal has higher power, and can be directly input to the next optical fiber link to continue transmission, or Can be output directly for control or detection.
  • the wavelength range of the multimode pump laser is 880 to 980 nm, and the first wavelength range is 970 to 1030 nm.
  • the optical fiber amplifier provided in this application, it can generate single-mode pump laser light with a wavelength range of 970 to 1030nm for amplifying input optical signals. It has good NF performance and can meet the requirements of telecom-grade optical fiber amplifiers.
  • the above-mentioned first optical path includes: a double-clad ytterbium-doped optical fiber, used to absorb multimode pump laser light, and generate and amplify single-mode pump laser light in the first wavelength range; erbium-doped optical fiber, used to absorb the first wavelength range of single-mode pump lasers to amplify the input optical signal.
  • the single-mode erbium-doped optical fiber in the existing telecommunication-grade optical fiber amplifier can be directly multiplexed, and its workable spectral bandwidth is guaranteed to be consistent with that of existing products, which helps to reduce pumping costs.
  • the above resonance amplifying unit further includes a cladding pump stripper, which is used to strip the unabsorbed multimode pump laser light from the double-clad ytterbium-doped fiber.
  • a cladding pump stripper is located between the erbium-doped fiber and the double-clad ytterbium-doped fiber.
  • the resonant amplifying unit includes a resonant cavity, and the resonant amplifying unit repeatedly oscillates the single-mode pump laser in the first wavelength range in the first optical path through the resonant cavity.
  • the single-mode pump laser can oscillate in the resonant cavity and repeatedly pass through the erbium-doped fiber, which can greatly improve the absorption of the erbium-doped fiber to the single-mode pump laser, Thereby improving the pump absorption coefficient.
  • the resonant cavity includes a first fiber Bragg grating and a second fiber Bragg grating, the reflectivity of the first fiber Bragg grating and the second fiber Bragg grating to the single-mode pump laser light in the first wavelength range is greater than a first threshold, and the first fiber Bragg grating and The transmittance of the second fiber grating to the amplified input optical signal is greater than the second threshold.
  • the first threshold may be 90%
  • the second threshold may be 90%.
  • the first fiber grating and the second fiber grating have relatively high reflectivity (for example, reflectivity ⁇ 90%) to the single-mode pump laser in the first wavelength range, so that the single-mode pump laser in the first wavelength range can be Repeatedly oscillating in the resonant cavity and repeatedly passing through the erbium-doped fiber can greatly improve the absorption of the single-mode pump laser by the erbium-doped fiber, thereby improving the pump absorption coefficient.
  • the amplified input optical signal has a high transmittance (for example, transmittance ⁇ 90%), so that the input optical signal can be smoothly output after being amplified in the resonant cavity, and the NF performance of the amplified optical signal is guaranteed.
  • the foregoing first threshold and second threshold may also be adjusted according to conditions such as fiber length and parameter requirements for the amplified input optical signal. For example, when the ytterbium-doped fiber is long, the first threshold can be lowered; when the erbium-doped fiber is long, the first threshold can be raised. For another example, when the NF performance of the amplified input optical signal is required to be high, the second threshold may be increased; otherwise, the second threshold may be decreased.
  • the wavelength difference between the first fiber Bragg grating and the second fiber Bragg grating is smaller than the reflection bandwidth of the first fiber Bragg grating and the second fiber Bragg grating.
  • the input unit further includes a first wavelength division multiplexer, configured to couple the input optical signal and the multimode pump laser light into the first optical path.
  • a first wavelength division multiplexer configured to couple the input optical signal and the multimode pump laser light into the first optical path.
  • the output unit further includes a second wavelength division multiplexer, configured to separate and output the amplified input optical signal from the first optical path.
  • the first wavelength division multiplexer and the second wavelength division multiplexer may also constitute the resonant cavity structure described above.
  • the output unit further includes a gain flattening filter and/or an adjustable optical attenuator.
  • the erbium-doped fiber is any one of the following: single-mode erbium-doped fiber, large-mode-field erbium-doped fiber, and double-clad erbium-doped fiber.
  • Multi-mode pumps do not have single-mode conditions, and their output power is much higher than that of single-mode pumps. They can also achieve kilowatt-level output power through external beam combining methods.
  • the production process of multi-mode pumps is simple and low-cost. However, the output spot size and divergence angle of the multimode pump are relatively large, and it is difficult to directly couple into the single-mode fiber, so it is impossible to pump the EDF through the wavelength division multiplexing technology.
  • the optical fiber amplifier of the present application by converting the multimode pump laser generated by the multimode pump into a single-mode pump laser, a multimode pump with higher output power and lower cost can be used instead of a multimode pump with lower output power and lower cost.
  • the high single-mode pump helps to reduce the pumping cost and increase the saturation output power of the optical amplifier.
  • Fig. 5 is a schematic structural diagram of a specific example of the fiber amplifier provided in the present application.
  • Fig. 5(a) and Fig. 5(b) show forward-pumped and backward-pumped fiber amplifiers, respectively.
  • its multimode pumping unit includes a multimode pump 509, which is used to generate multimode pumping laser light, and the wavelength range of the multimode pumping laser light can be is 880 to 980nm.
  • the input unit includes an isolator 501, and in this embodiment, the input unit also includes a beam combiner 502 for inputting an input optical signal (such as a C or L-band telecommunication signal) and a multimode pump laser into a double-clad optical fiber
  • the core and inner cladding that is, the input resonant amplifier unit.
  • the resonance amplifying unit includes a fiber grating 503 , a double-clad ytterbium-doped fiber 504 , a cladding pump stripper 505 , an erbium-doped fiber 506 and a fiber grating 507 .
  • the double-clad ytterbium-doped fiber 504 is used to absorb the multimode pump laser, generate and amplify the single-mode pump laser in the first wavelength range, and the first wavelength range can be 970 to 1030nm; the cladding pump stripper 505 is used For stripping the unabsorbed multimode pump laser light of the double-clad ytterbium-doped fiber 504; the reflectivity of the fiber grating 503 and the fiber grating 507 to the single-mode pump laser light of the first wavelength range is greater than the first threshold (for example, 90%) , the transmittance of the amplified input optical signal is greater than a second threshold (for example, 90%), and the wavelength difference between the fiber grating 503 and the fiber grating 507 is smaller than the maximum reflection bandwidth of the two.
  • the output unit includes an optical isolator 508 for outputting the amplified input optical signal.
  • the fiber grating 503 and the fiber grating 507 can form a resonant cavity structure. Due to the high reflection characteristics of the fiber grating 503 and the fiber grating 507 to the single-mode pump laser in the first wavelength range, the single-mode pump laser in the first wavelength range It can repeatedly oscillate in the first optical path formed by the double-clad ytterbium-doped fiber 504 and the erbium-doped fiber 506, continuously passing through the erbium-doped fiber 506, which equivalently increases the pump absorption coefficient.
  • FIG. 5(b) The basic structure and principle of the backward-pumped optical fiber amplifier shown in FIG. 5(b) are basically the same as the above-mentioned forward-pumped optical fiber amplifier. For the sake of brevity, details will not be repeated here.
  • the optical fiber amplifier of the present application by converting the multimode pump laser generated by the multimode pump into a single-mode pump laser, a multimode pump with higher output power and lower cost can be used instead of a multimode pump with lower output power and lower cost.
  • the high single-mode pump helps to reduce the pumping cost and increase the saturation output power of the optical amplifier.
  • Fig. 6 is a schematic structural diagram of another specific example of the fiber amplifier provided in the present application.
  • the input optical signal passes through a series of new devices that may cause insertion loss, such as double-layer ytterbium-doped fiber and cladding pump stripper, which may lead to energy consumption and poor NF performance.
  • insertion loss such as double-layer ytterbium-doped fiber and cladding pump stripper
  • FIG. 6 proposes a schematic structural diagram as shown in FIG. 6 .
  • the multimode pump unit includes a multimode pump 610 for generating multimode pump laser light, and the wavelength range of the multimode pump laser light may be 880 to 980 nm.
  • the input unit includes an isolator 601, and in this embodiment, the input unit also includes a wavelength division multiplexer 602 for inputting an input optical signal (such as a 1.5 ⁇ m telecommunication signal) and a multimode pump laser into a double-clad fiber (also It can be the core and inner cladding (that is, the input resonant amplifying unit) in the double-clad erbium-doped fiber.
  • the resonant amplifying unit includes a double-clad ytterbium-doped fiber 608 , a cladding pump stripper 607 and an erbium-doped fiber 603 , and its functions can be referred to above, and will not be repeated here.
  • the output unit includes an optical isolator 605, and in this embodiment, the output unit further includes a wavelength division multiplexer 604, which is used to separate and output the amplified input optical signal from the first optical path, and separate the amplified input optical signal from the first optical path
  • the mode-pumped laser light is input into the beam combiner 609.
  • the wavelength division multiplexer 602 of the input unit and the wavelength division multiplexer 604 of the output unit can also form a ring resonator structure, so that the single-mode pump laser in the first wavelength range can pass through the double-clad ytterbium-doped fiber 608 and the doped
  • the first optical path formed by the erbium fiber 603 oscillates repeatedly and continuously passes through the erbium-doped fiber 603, which equivalently increases the pump absorption coefficient.
  • the input unit includes an isolator 621.
  • the input unit also includes a wavelength division multiplexer 622.
  • the resonant amplifying unit comprises a fiber grating 624, a double-clad ytterbium-doped fiber 627, a cladding pump stripper 626, an erbium-doped fiber 623, and a fiber grating 628.
  • the functions of its components can refer to the description in FIG. Let me repeat.
  • the fiber grating 624 and the fiber grating 628 can form a resonant cavity structure. Due to the high reflection characteristics of the fiber grating 624 and the fiber grating 628 to the single-mode pump laser in the first wavelength range, the single-mode pump laser in the first wavelength range It can repeatedly oscillate in the first optical path formed by the double-clad ytterbium-doped fiber 627 and the erbium-doped fiber 623, continuously passing through the erbium-doped fiber 623, and equivalently improving the pump absorption coefficient.
  • the optical fiber amplifier of the present application by converting the multimode pump laser generated by the multimode pump into a single-mode pump laser, a multimode pump with higher output power and lower cost can be used instead of a multimode pump with lower output power and lower cost.
  • the high single-mode pump helps to reduce the pumping cost and increase the saturation output power of the optical amplifier.
  • the input optical signal does not pass through a series of newly added devices that may cause insertion loss, such as double-clad ytterbium-doped optical fibers and cladding pump strippers, and the upper limit of NF performance is better.
  • Fig. 7 is a structural schematic diagram of an example of the multi-stage structure of the optical fiber amplifier provided by the present application.
  • the structure of the fiber amplifier has changed from a single-stage structure to a multi-stage structure, wherein, after the input optical signal is amplified by the single-stage fiber amplifier shown in Figure 5 or Figure 6 above, it can be filtered by gain flattening Gain flattening filter (GFF) 702 implements gain shaping, and variable optical attenuator (variable optical attenuator, VOA) 703 adjusts optical power, and then enters the second-stage single-stage amplifier for amplification.
  • GFF gain flattening
  • VOA variable optical attenuator
  • multi-stage structures can be superimposed, GFF and VOA can be set between amplifiers, and amplifiers with different stages can use single-stage fiber amplifiers as shown in Figure 5 or Figure 6 respectively.
  • the GFF and the VOA may belong to the output unit of the pre-stage optical fiber amplifier. At this time, the output unit also has the function of performing gain shaping on the output amplified input optical signal and adjusting the optical power.
  • the optical fiber amplifier of the present application by converting the multimode pump laser generated by the multimode pump into a single-mode pump laser, a multimode pump with higher output power and lower cost can be used instead of a multimode pump with lower output power and lower cost.
  • the high single-mode pump helps to reduce the pumping cost and increase the saturation output power of the optical amplifier.
  • the input optical signal can be amplified by multiple optical fiber amplifiers, which helps to reduce the pumping cost and increase the saturated output optical power.
  • different levels of fiber amplifiers can also use wavelength division multiplexers to connect single-mode pump lasers into a single-mode pump laser loop 715 to achieve double-clad Multiplexing of ytterbium-doped optical fiber, cladding pump stripper and other devices.
  • Fig. 8 is a structural schematic diagram of an example of the multi-group array structure of the optical fiber amplifier provided by the present application.
  • the optical fiber amplifier is changed from a single group to an array form of multiple groups, and the input optical signals of multiple groups are amplified by the fiber amplifier shown in FIG. 5 or FIG. 6 in parallel.
  • the multimode pump 801 since the multimode pump 801 has a high power output capability (up to hundreds of watts), the multimode pump generated by the multimode pump 801 can be generated by the multimode pump 802 through a beam splitter 802.
  • the laser light is distributed to different fiber amplifiers according to a certain energy ratio as pump input, for example, fiber amplifier 803 , fiber amplifier 804 and fiber amplifier 805 .
  • the optical fiber amplifier of the present application by converting the multimode pump laser generated by the multimode pump into a single-mode pump laser, a multimode pump with higher output power and lower cost can be used instead of a multimode pump with lower output power and lower cost.
  • the high single-mode pump helps to reduce the pumping cost and increase the saturation output power of the optical amplifier.
  • the multimode pump laser generated by a single multimode pump is distributed to different fiber amplifiers according to a certain energy ratio through the beam splitter as the pump input, which can greatly improve the integration of the system. Reduce pumping costs.
  • multiple groups of fiber amplifiers can also share the conversion part of the multimode pump, reducing the amount of double-clad ytterbium-doped fibers and passive components.
  • Fig. 9 is a schematic flowchart of an example of a method for amplifying an optical signal provided by the present application.
  • S910 Receive an input optical signal, and input the input optical signal to the first optical path.
  • the input optical signal may be a transmitted optical signal in the last optical fiber link, or an optical signal directly output by the laser.
  • multimode pumping laser light can be generated by a multimode pump.
  • the wavelength range of the multimode pump laser may be 880 to 980 nm.
  • the first wavelength range may be 970 to 1030 nm.
  • the single-mode pump laser with a wavelength range of 970 to 1030nm can be generated according to the multi-mode pump laser, which is used to amplify the input optical signal, and the NF performance is good, which can meet the requirements of the carrier-grade optical fiber amplifier .
  • the first optical path may include a double-clad ytterbium-doped fiber and an erbium-doped fiber.
  • the double-clad ytterbium-doped fiber is used to absorb multi-mode pump laser, generate and amplify the single-mode pump laser in the first wavelength range; the erbium-doped fiber is used to absorb the single-mode pump laser in the first wavelength range, and amplify the input optical signal .
  • the single-mode erbium-doped optical fiber in the existing telecommunication-grade optical fiber amplifier can be directly reused, ensuring that its workable spectral bandwidth is consistent with that of existing products.
  • the single-mode pump laser light can be oscillated in the first optical path through the resonant cavity structure.
  • the resonant cavity may include a first fiber Bragg grating and a second fiber Bragg grating, the reflectivity of the first fiber Bragg grating and the second fiber Bragg grating to the single-mode pump laser light in the first wavelength range is greater than the first threshold, The transmittance of the first fiber grating and the second fiber grating to the amplified input optical signal is greater than a second threshold.
  • the first threshold may be 90%
  • the second threshold may be 90%.
  • the first fiber grating and the second fiber grating have relatively high reflectivity (for example, reflectivity ⁇ 90%) to the single-mode pump laser in the first wavelength range, so that the single-mode pump laser in the first wavelength range can be Repeatedly oscillating in the resonant cavity and repeatedly passing through the erbium-doped fiber can greatly improve the absorption of the single-mode pump laser by the erbium-doped fiber, thereby improving the pump absorption coefficient.
  • the amplified input optical signal has a high transmittance (for example, transmittance ⁇ 90%), so that the input optical signal can be smoothly output after being amplified in the resonant cavity, and the NF performance of the amplified optical signal is guaranteed.
  • the foregoing first threshold and second threshold may also be adjusted according to conditions such as fiber length and parameter requirements for the amplified input optical signal. For example, when the ytterbium-doped fiber is long, the first threshold can be lowered; when the erbium-doped fiber is long, the first threshold can be raised. For another example, when the NF performance of the amplified input optical signal is required to be high, the second threshold may be increased; otherwise, the second threshold may be decreased.
  • the wavelength difference between the first fiber Bragg grating and the second fiber Bragg grating is smaller than the reflection bandwidth of the first fiber Bragg grating and the second fiber Bragg grating.
  • the resonant cavity may include a first wavelength division multiplexer and a second wavelength division multiplexer, the first wavelength division multiplexer is used to combine the input optical signal and the multimode pump laser ( and/or a single-mode pump laser in the first wavelength range) is coupled into the first optical path; the second wavelength division multiplexer is used to separate and output the amplified input optical signal from the first optical path, and the first The single-mode pump laser light in the wavelength range is delivered to the first wavelength division multiplexer.
  • the erbium-doped fiber is any one of the following: single-mode erbium-doped fiber, large-mode-field erbium-doped fiber, and double-clad erbium-doped fiber.
  • the amplified input optical signal can be directly input to the next optical fiber link for further transmission, or can be directly output for control or detection.
  • the optical fiber amplifier of the present application by converting the multimode pump laser generated by the multimode pump into a single-mode pump laser, a multimode pump with higher output power and lower cost can be used instead of a multimode pump with lower output power and lower cost.
  • the high single-mode pump helps to reduce the pumping cost and increase the saturation output power of the optical amplifier.
  • the embodiment of the present application also provides a device, including a processor and an interface.
  • the processor may be used to execute the methods in the foregoing method embodiments.
  • the above processing device may be a chip.
  • the processing device may be a field programmable gate array (field programmable gate array, FPGA), an application specific integrated circuit (ASIC), or a system chip (system on chip, SoC). It can be a central processor unit (CPU), a network processor (network processor, NP), a digital signal processing circuit (digital signal processor, DSP), or a microcontroller (micro controller unit) , MCU), can also be a programmable controller (programmable logic device, PLD) or other integrated chips.
  • CPU central processor unit
  • NP network processor
  • DSP digital signal processor
  • microcontroller micro controller unit
  • PLD programmable logic device
  • each step of the above method can be completed by an integrated logic circuit of hardware in a processor or an instruction in the form of software.
  • the steps of the methods disclosed in connection with the embodiments of the present application may be directly implemented by a hardware processor, or implemented by a combination of hardware and software modules in the processor.
  • the software module can be located in a mature storage medium in the field such as random access memory, flash memory, read-only memory, programmable read-only memory or electrically erasable programmable memory, register.
  • the storage medium is located in the memory, and the processor reads the information in the memory, and completes the steps of the above method in combination with its hardware. To avoid repetition, no detailed description is given here.
  • the processor in the embodiment of the present application may be an integrated circuit chip, which has a signal processing capability.
  • each step of the above-mentioned method embodiments may be completed by an integrated logic circuit of hardware in a processor or instructions in the form of software.
  • the above-mentioned processor may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components .
  • DSP digital signal processor
  • ASIC application-specific integrated circuit
  • FPGA field-programmable gate array
  • a general-purpose processor may be a microprocessor, or the processor may be any conventional processor, and the like.
  • the steps of the method disclosed in the embodiments of the present application may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor.
  • the software module may be located in a mature storage medium in the field such as random access memory, flash memory, read-only memory, programmable read-only memory or electrically erasable programmable memory, register.
  • the storage medium is located in the memory, and the processor reads the information in the memory, and completes the steps of the above method in combination with its hardware.
  • the memory in the embodiments of the present application may be a volatile memory or a nonvolatile memory, or may include both volatile and nonvolatile memories.
  • the non-volatile memory can be read-only memory (read-only memory, ROM), programmable read-only memory (programmable ROM, PROM), erasable programmable read-only memory (erasable PROM, EPROM), electrically programmable Erases programmable read-only memory (electrically EPROM, EEPROM) or flash memory.
  • Volatile memory can be random access memory (RAM), which acts as external cache memory.
  • RAM random access memory
  • SRAM static random access memory
  • DRAM dynamic random access memory
  • DRAM synchronous dynamic random access memory
  • SDRAM double data rate synchronous dynamic random access memory
  • ESDRAM enhanced synchronous dynamic random access memory
  • SLDRAM direct memory bus random access memory
  • direct rambus RAM direct rambus RAM
  • the present application also provides a computer program product, the computer program product including: computer program code, when the computer program code is run on the computer, the computer is made to execute the embodiment shown in FIG. 9 Methods.
  • the present application also provides a computer-readable medium, the computer-readable medium stores program code, and when the program code is run on the computer, the computer is made to execute the embodiment shown in FIG. 9 Methods.
  • all or part of them may be implemented by software, hardware, firmware or any combination thereof.
  • software When implemented using software, it may be implemented in whole or in part in the form of a computer program product.
  • the computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on the computer, the processes or functions according to the embodiments of the present application will be generated in whole or in part.
  • the computer can be a general purpose computer, a special purpose computer, a computer network, or other programmable devices.
  • the computer instructions may be stored in or transmitted from one computer-readable storage medium to another computer-readable storage medium, for example, the computer instructions may be transmitted from a website, computer, server or data center Transmission to another website site, computer, server or data center by wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.).
  • the computer-readable storage medium may be any available medium that can be accessed by a computer, or a data storage device including a server, a data center, and the like integrated with one or more available media.
  • the available medium may be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a high-density digital video disc (digital video disc, DVD)), or a semiconductor medium (for example, a solid state disk (solid state disc, SSD)) etc.
  • a magnetic medium for example, a floppy disk, a hard disk, a magnetic tape
  • an optical medium for example, a high-density digital video disc (digital video disc, DVD)
  • a semiconductor medium for example, a solid state disk (solid state disc, SSD)
  • a component may be, but is not limited to being, a process running on a processor, a processor, an object, an executable, a thread of execution, a program, and/or a computer.
  • an application running on a computing device and the computing device can be components.
  • One or more components can reside within a process and/or thread of execution and a component can be localized on one computer and/or distributed between two or more computers.
  • these components can execute from various computer readable media having various data structures stored thereon.
  • a component may, for example, be based on a signal having one or more packets of data (e.g., data from two components interacting with another component between a local system, a distributed system, and/or a network, such as the Internet via a signal interacting with other systems). Communicate through local and/or remote processes.
  • packets of data e.g., data from two components interacting with another component between a local system, a distributed system, and/or a network, such as the Internet via a signal interacting with other systems.
  • the disclosed systems, devices and methods may be implemented in other ways.
  • the device embodiments described above are only illustrative.
  • the division of the units is only a logical function division. In actual implementation, there may be other division methods.
  • multiple units or components can be combined or May be integrated into another system, or some features may be ignored, or not implemented.
  • the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection of devices or units may be in electrical, mechanical or other forms.
  • the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.
  • each functional unit in each embodiment of the present application may be integrated into one processing unit, each unit may exist separately physically, or two or more units may be integrated into one unit.

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Abstract

一种光纤放大器（400,500,600,701,704,711,714,803,804,805,816,817,818）和放大光信号的方法，光纤放大器（400,500,600,701,704,711,714,803,804,805,816,817,818）包括：多模泵浦单元（410），用于产生多模泵浦激光；输入单元（420），用于将输入光信号和多模泵浦激光输入到第一光路（440），第一光路（440）属于谐振放大单元（430）；谐振放大单元（430），用于根据多模泵浦激光生成第一波长范围的单模泵浦激光，将第一波长范围的单模泵浦激光在第一光路（440）中反复振荡，以使得第一波长范围的单模泵浦激光放大输入光信号；输出单元（450），用于输出放大后的输入光信号。光纤放大器（400,500,600,701,704,711,714,803,804,805,816,817,818）通过将多模泵（509,519,610,630,801,811）产生的多模泵浦激光转化为单模泵浦激光，从而可以使用输出功率更大、成本更低的多模泵（509,519,610,630,801,811）代替输出功率较低且成本较高的单模泵(107)，有助于降低泵浦成本，提高光放饱和出光功率。

Description

一种光纤放大器和放大光信号的方法
本申请要求于2021年12月13日提交中国国家知识产权局、申请号202111517617.7、申请名称为“一种光纤放大器和放大光信号的方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及光传输技术领域，并且更具体地，涉及一种光纤放大器和放大光信号的方法。
背景技术
光纤放大器作为光纤通信系统中的补偿光信号损耗的主要手段，其性能和带宽对光纤通信系统整体性能有重要影响，而其成本更是决定整体系统能否适应更多应用场景的关键因素，因此，低成本的光纤放大器成为了业界的研究热点。其中，降低光纤放大器中的泵浦激光器的成本是实现低成本光纤放大器的关键。
目前，电信级的光纤放大器的泵浦激光器主要是单模泵(single-mode pump，SMP)，其能够直接输出单横模的激光束，该激光束具有较小的光斑尺寸，可以高效地耦合进单模光纤中，通过波分复用技术，能够实现对单模掺铒光纤(Er-doped fiber，EDF)的泵浦。但是由于单模条件的限制，SMP的输出激光功率有限，并且随着功率的增加，其成本急剧上升。
因此，亟需一种能够降低泵浦成本光纤放大器。
发明内容
本申请提供一种光纤放大器和放大光信号的方法，能够降低泵浦成本，提高光放饱和出光功率。
第一方面，提供了一种光纤放大器，包括：多模泵浦单元，用于产生多模泵浦激光；输入单元，用于将输入光信号和多模泵浦激光输入到第一光路，第一光路属于谐振放大单元；谐振放大单元，用于根据多模泵浦激光生成第一波长范围的单模泵浦激光，将第一波长范围的单模泵浦激光在第一光路中反复振荡，以使得第一波长范围的单模泵浦激光放大输入光信号；输出单元，用于输出放大后的输入光信号。
根据本申请的光纤放大器，通过将多模泵产生的多模泵浦激光转化为单模泵浦激光，从而可以使用输出功率更大、成本更低的多模泵代替输出功率较低且成本较高的单模泵，有助于降低泵浦成本，提高光放饱和出光功率。
结合第一方面，在第一方面的某些实现方式中，上述多模泵浦激光的波长范围为880至980nm，第一波长范围为970至1030nm。
根据本申请所提供的光纤放大器，能够产生波长范围为970至1030nm的单模泵浦激光，用于放大输入光信号，信噪比性能较好，能够满足电信级光纤放大器的要求。
结合第一方面，在第一方面的某些实现方式中，上述第一光路包括：双包层掺镱光纤， 用于吸收多模泵浦激光，产生和放大第一波长范围的单模泵浦激光；掺铒光纤，用于吸收第一波长范围的单模泵浦激光，放大输入光信号。
根据本申请所提供的光纤放大器，能够直接复用现有电信级光纤放大器中的单模掺铒光纤，保障其可工作光谱带宽与现有产品一致，有助于降低泵浦成本。
结合第一方面，在第一方面的某些实现方式中，上述谐振放大单元还包括包层泵浦剥离器，用于剥除双包层掺镱光纤未吸收的多模泵浦激光。
结合第一方面，在第一方面的某些实现方式中，包层泵浦剥离器位于掺铒光纤和双包层掺镱光纤之间。
结合第一方面，在第一方面的某些实现方式中，谐振放大单元包括谐振腔，谐振放大单元通过谐振腔将第一波长范围的单模泵浦激光在第一光路中反复振荡。
根据本申请所提供的光纤放大器，通过设置谐振腔，使得单模泵浦激光能够在谐振腔中震荡，反复穿过掺铒光纤，能够大幅度提高掺铒光纤对单模泵浦激光的吸收，从而提高了泵浦吸收系数。
结合第一方面，在第一方面的某些实现方式中，谐振腔包括第一光纤光栅和第二光纤光栅，第一光纤光栅和第二光纤光栅对第一波长范围的单模泵浦激光的反射率大于第一阈值，第一光纤光栅和第二光纤光栅对放大后的输入光信号的透射率大于第二阈值。
作为示例而非限定，第一阈值可以为90％，第二阈值可以为90％。这样，第一光纤光栅和第二光纤光栅对第一波长范围的单模泵浦激光具有较高的反射率(例如，反射率≥90％)，使得第一波长范围的单模泵浦激光可以在谐振腔中反复震荡，反复穿过掺铒光纤，能够大幅度提高掺铒光纤对单模泵浦激光的吸收，从而提高了泵浦吸收系数，同时由于第一光纤光栅和第二光纤光栅对放大后的输入光信号具有较高的透射率(例如，透射率≥90％)，使得输入光信号在谐振腔中被放大后，可以顺利的输出，并保证放大后的光信号的NF性能。
结合第一方面，在第一方面的某些实现方式中，第一光纤光栅和第二光纤光栅的波长差值小于第一光纤光栅和第二光纤光栅的反射带宽。
结合第一方面，在第一方面的某些实现方式中，输入单元还包括第一波分复用器，用于将输入光信号和多模泵浦激光耦合进第一光路。
结合第一方面，在第一方面的某些实现方式中，输出单元还包括第二波分复用器，用于将放大后的输入光信号从第一光路中分离并输出。
结合第一方面，在第一方面的某些实现方式中，输出单元还包括增益平坦滤波器和/或可调光衰减器。
结合第一方面，在第一方面的某些实现方式中，掺铒光纤为以下任一项：单模掺饵光纤、大模场掺铒光纤、双包层掺铒光纤。
第二方面，提供了一种放大光信号的方法，包括：接收输入光信号，并将输入光信号输入到第一光路中；产生多模泵浦激光；根据多模泵浦激光生成第一波长范围的单模泵浦激光，将第一波长范围的单模泵浦激光在第一光路中反复振荡，以使得第一波长范围的单模泵浦激光放大输入光信号；输出放大后的输入光信号。
根据本申请所提供的技术方案，使用多模泵代替单模泵，能够降低泵浦成本，提高光放饱和出光功率。
结合第二方面，在第二方面的某些实现方式中，上述多模泵浦激光的波长范围为880至 980nm，第一波长范围为970至1030nm。
根据本申请所提供的光纤放大器，能够产生波长范围为970至1030nm的单模泵浦激光，用于放大输入光信号，NF性能较好，能够满足电信级光纤放大器的要求。
结合第二方面，在第二方面的某些实现方式中，上述第一光路包括双包层掺镱光纤，用于吸收多模泵浦激光，产生和放大第一波长范围的单模泵浦激光；掺铒光纤，用于吸收第一波长范围的单模泵浦激光，放大输入光信号。
结合第二方面，在第二方面的某些实现方式中，掺铒光纤为以下任一项：单模掺饵光纤、大模场掺铒光纤、双包层掺铒光纤。
第三方面，提供了一种光纤通信系统，该系统包括：光放站点，该光放站点包括如第一方面提供的光纤放大器。
第四方面，提供了一种放大光信号的装置，该装置用于执行上述第二方面的方法。具体地，该装置可以包括用于执行第二方面提供的方法的单元和/或模块，如处理模块和/或收发模块。
在一种实现方式中，该装置为放大器。当该装置为放大器时，该收发模块可以是收发器，或，输入/输出接口；该处理模块可以是处理器。
在另一种实现方式中，该装置为用于放大光信号的芯片、芯片系统或电路。当该装置为放大光信号设备中的芯片、芯片系统或电路时，该收发模块单元可以是该芯片、芯片系统或电路上的输入/输出接口、接口电路、输出电路、输入电路、管脚或相关电路等；该处理模块可以是处理器、处理电路或逻辑电路等。
基于上述方案的有益效果，可以参考第一方面的相应描述，为了简洁，本申请在此不再赘述。
可选地，上述收发器可以为收发电路。可选地，上述输入/输出接口可以为输入/输出电路。
附图说明
图1是一种电信级光纤放大器的结构示意图。
图2是一种多模激光放大单模激光信号的示意图。
图3是一种单模光纤放大器的结构示意图。
图4是本申请提供的光纤放大器的一例结构示意图。
图5是本申请提供的光纤放大器的具体示例的一例结构示意图。
图6是本申请提供的光纤放大器的具体示例的另一例结构示意图。
图7是本申请提供的光纤放大器的多级结构的一例结构示意图。
图8是本申请提供的光纤放大器的多组阵列结构的一例结构示意图。
图9是本申请提供的放大光信号的方法的一例示意性流程图。
具体实施方式
下面将结合附图，对本申请中的技术方案进行描述。
本申请实施例的技术方案可以应用于光纤通信网络中，如本申请实施例的技术方案可以用于光纤通信网络中的光纤放大器中，光纤放大器主要位于光纤通信网络中的光放站点及光 放网元。本申请实施例的技术方案可以用于实现由多芯光纤构成的光纤放大器。
图1示出了一种电信级光纤放大器100的结构示意图。其中，光纤放大器100包括隔离器(isolator，ISO)101、波分复用器(wavelength division multiplexer，WDM)102、掺铒光纤(Er-doped fiber，EDF)、隔离器104以及单模泵107。可选的，光纤放大器100还可以包括增益平坦滤波器105和可调光衰减器106。单模泵SMP107作为光纤放大器100的泵浦激光器，能够直接输出单横模的激光束，具备较小的光斑尺寸，能够高效地耦合进单模光纤中，再通过波分复用技术，从而实现对单模EDF的泵浦。
光纤放大器作为光纤通信系统中的补偿光信号损耗的主要手段，其性能和带宽对光纤通信系统整体性能有重要影响，而其成本更是决定整体系统能否适应更多应用场景的关键因素，因此，低成本的光纤放大器成为了业界的研究热点。其中，降低光纤放大器中的泵浦激光器的成本是实现低成本光纤放大器的关键。
但是，上述介绍的SMP由于单模条件的限制，其输出激光功率有限，并且随着功率的增加，其成本急剧上升。
MMP不存在单模条件限制，其输出功率远高于SMP，还可以通过外部的合束手段实现高达千瓦级别的输出功率，且MMP的生产工艺简单、成本低廉。但是MMP输出光斑尺寸和发散角较大，难以直接耦合进单模光纤，也就无法通过波分复用技术实现对EDF的泵浦。
因此，亟需一种能够降低泵浦成本光纤放大器。
目前，已知的一种技术可以通过包层泵浦配合双包层掺杂光纤来实现降低泵浦成本的目的。如图2所示，多模泵(multi-mode pump，MMP)通过耦合在双包层光纤的内包层中传播，而待放大的单模信号激光则在双包层光纤的纤芯中传播，由于双包层光纤的内包层和纤芯共轴，内包层中的多模激光在轴向传播过程中，会有一定概率穿过纤芯，泵浦纤芯中的稀土离子至上能级，从而实现多模泵浦对单模信号激光的放大。
但是，在上述方法中，用于MMP穿过纤芯的概率非常低，约等于纤芯与内包层截面积之比(小于1％)，所以该技术会大幅度降低泵浦的等效吸收系数。以普通单模EDF泵浦吸收系数5dB/m为例，采用该技术时，EDF的等效系数小于0.05dB/m，即所需的光纤长度增加超过100倍，成本大幅增加。此外，在在相同泵浦功率下，由于较低的泵浦吸收，导致EDF的上能级反转率较低，噪声指数(noise figure，NF)性能大幅度下降。因此，该技术只能应用于铒镱共掺光纤这类对泵浦吸收系数更高的掺杂光纤，然而铒镱共掺光纤的可放大带宽以及NF性能相对于EDF仍有较大差距，所以该技术目前常应用于社区天线电视(community antenna television，CATV)中，无法应用到电信级的光纤放大器中。
图3示出了一种单模光纤放大器的机构示意图。如图3所示，在上述方法的基础上，MMP通过包层泵浦技术构建一个单模的光纤放大器，来实现对单模泵浦激光的产生或放大，放大后的单模泵浦激光再通过WDM耦合到光纤放大器中，泵浦稀土离子，从而实现对单模激光信号的放大。
但是，该技术无法有效地产生或放大电信级光纤放大器所需的最佳泵浦波段(例如，980nm)。其中，该技术常用的手段是通过包层泵浦产生单模的101xnm或153xnm的光纤激光作为后续光纤放大器的泵浦源。以本领域较为常用的1018nm激光为例，EDF在1018nm处的吸收系数约为0.3dB/m，尽管相对于图2所示的技术有所提升，但仍然无法避免光纤长度增加，NF性能大幅度下降的缺点。而对于153xnm泵浦的技术方案，一方面，带内泵浦会 导致NF性能大幅度劣化，另一方面，153xnm泵浦无法覆盖152xnm的信号放大，也就无法支撑整个C波段的放大。
多模泵不存在单模条件限制，其输出功率远高于单模泵，还可以通过外部的合束手段实现高达千瓦级别的输出功率，且多模泵的生产工艺简单、成本低廉。但是多模泵输出光斑尺寸和发散角较大，难以直接耦合进单模光纤，也就无法通过波分复用技术实现对EDF的泵浦。
基于此，本申请提出了一种光纤放大器，以期望能够使用多模泵代替单模泵，从而降低泵浦成本，提高光放饱和出光功率。
图4是本申请提供的光纤放大器的一例结构示意图。
如图4所示，该光纤放大器400包括多模泵浦单元410、输入单元420、谐振放大单元430以及输出单元450。其中，多模泵浦单元410，用于产生多模泵浦激光；输入单元420，用于将输入光信号和多模泵浦激光输入到第一光路440，第一光路440属于谐振放大单元430；谐振放大单元430，用于根据多模泵浦激光生成第一波长范围的单模泵浦激光，将第一波长范围的单模泵浦激光在第一光路中反复振荡，以使得第一波长范围的单模泵浦激光放大输入光信号；输出单元450，用于输出放大后的输入光信号。
其中，输入光信号可以是上一段光纤链路中的传输光信号，也可以是激光器直接输出的光信号；输出光信号具有更高的功率，可以直接输入到下一段光纤链路继续传输，也可以直接输出，用于控制或者探测。
可选地，上述多模泵浦激光的波长范围为880至980nm，第一波长范围为970至1030nm。
根据本申请所提供的光纤放大器，能够产生波长范围为970至1030nm的单模泵浦激光，用于放大输入光信号，NF性能较好，能够满足电信级光纤放大器的要求。
可选地，上述第一光路包括：双包层掺镱光纤，用于吸收多模泵浦激光，产生和放大第一波长范围的单模泵浦激光；掺铒光纤，用于吸收第一波长范围的单模泵浦激光，放大输入光信号。
根据本申请所提供的光纤放大器，能够直接复用现有电信级光纤放大器中的单模掺铒光纤，保障其可工作光谱带宽与现有产品一致，有助于降低泵浦成本。
可选地，上述谐振放大单元还包括包层泵浦剥离器，用于剥除双包层掺镱光纤未吸收的多模泵浦激光。
可选地，包层泵浦剥离器位于掺铒光纤和双包层掺镱光纤之间。
可选地，谐振放大单元包括谐振腔，谐振放大单元通过谐振腔将第一波长范围的单模泵浦激光在第一光路中反复振荡。
根据本申请所提供的光纤放大器，通过设置谐振腔，使得单模泵浦激光能够在谐振腔中震荡，反复穿过掺铒光纤，能够大幅度提高掺铒光纤对单模泵浦激光的吸收，从而提高了泵浦吸收系数。
可选地，谐振腔包括第一光纤光栅和第二光纤光栅，第一光纤光栅和第二光纤光栅对第一波长范围的单模泵浦激光的反射率大于第一阈值，第一光纤光栅和第二光纤光栅对放大后的输入光信号的透射率大于第二阈值。
作为示例而非限定，第一阈值可以为90％，第二阈值可以为90％。这样，第一光纤光栅和第二光纤光栅对第一波长范围的单模泵浦激光具有较高的反射率(例如，反射率≥90％)，使得第一波长范围的单模泵浦激光可以在谐振腔中反复震荡，反复穿过掺铒光纤，能够大幅 度提高掺铒光纤对单模泵浦激光的吸收，从而提高了泵浦吸收系数，同时由于第一光纤光栅和第二光纤光栅对放大后的输入光信号具有较高的透射率(例如，透射率≥90％)，使得输入光信号在谐振腔中被放大后，可以顺利的输出，并保证放大后的光信号的NF性能。
应理解，在本申请实施例中，还可以根据光纤长度以及对放大后的输入光信号的参数要求等条件，调整上述第一阈值和第二阈值。例如，当掺镱光纤较长时，可以降低第一阈值；当掺饵光纤较长，可以升高第一阈值。又例如，当要求放大后的输入光信号的NF性能较高时，可以升高第二阈值，反之，可以降低第二阈值。
可选地，第一光纤光栅和第二光纤光栅的波长差值小于第一光纤光栅和第二光纤光栅的反射带宽。
可选地，输入单元还包括第一波分复用器，用于将输入光信号和多模泵浦激光耦合进第一光路。
可选地，输出单元还包括第二波分复用器，用于将放大后的输入光信号从第一光路中分离并输出。
其中，作为一种可能的实现方式，上述第一波分复用器和第二波分复用器也可以构成上文介绍的谐振腔结构。
可选地，输出单元还包括增益平坦滤波器和/或可调光衰减器。
可选地，掺铒光纤为以下任一项：单模掺饵光纤、大模场掺铒光纤、双包层掺铒光纤。
多模泵不存在单模条件限制，其输出功率远高于单模泵，还可以通过外部的合束手段实现高达千瓦级别的输出功率，且多模泵的生产工艺简单、成本低廉。但是多模泵输出光斑尺寸和发散角较大，难以直接耦合进单模光纤，也就无法通过波分复用技术实现对EDF的泵浦。
根据本申请的光纤放大器，通过将多模泵产生的多模泵浦激光转化为单模泵浦激光，从而可以使用输出功率更大、成本更低的多模泵代替输出功率较低且成本较高的单模泵，有助于降低泵浦成本，提高光放饱和出光功率。
图5是本申请提供的光纤放大器的具体示例的一例结构示意图。
如图5所示，图5(a)和图5(b)分别示出了前向泵浦和后向泵浦的光纤放大器。以图5(a)所示的前向泵浦的光纤放大器为例，其多模泵浦单元包括多模泵509，用于产生多模泵浦激光，该多模泵浦激光的波长范围可以是880至980nm。输入单元包括隔离器501，在该实施例中，输入单元还包括合束器502，用于将输入光信号(例如C或L波段的电信信号)和多模泵浦激光输入双包层光纤中的纤芯和内包层(即输入谐振放大单元)。谐振放大单元包括光纤光栅503、双包层掺镱光纤504、包层泵浦剥除器505、掺铒光纤506以及光纤光栅507。双包层掺镱光纤504用于吸收多模泵浦激光，产生和放大第一波长范围的单模泵浦激光，该第一波长范围可以是970至1030nm；包层泵浦剥除器505用于剥除双包层掺镱光纤504未吸收的多模泵浦激光；光纤光栅503和光纤光栅507对第一波长范围的单模泵浦激光的反射率大于第一阈值(例如，90％)，对放大后的输入光信号的透射率大于第二阈值(例如，90％)，光纤光栅503和光纤光栅507的波长差值小于二者中最大的反射带宽。输出单元包括光隔离器508，用于输出放大后的输入光信号。
其中，光纤光栅503和光纤光栅507可以构成谐振腔结构，由于光纤光栅503和光纤光栅507对第一波长范围的单模泵浦激光的高反特性，使得第一波长范围的单模泵浦激光可以在双包层掺镱光纤504和掺铒光纤506构成的第一光路中反复震荡，不断穿过掺铒光纤506， 等效地提高了泵浦吸收系数。
图5(b)所示的后向泵浦的光纤放大器的基本结构与原理基本与上述的前向泵浦的光纤放大器相同，为了简洁，在此不再赘述。
根据本申请的光纤放大器，通过将多模泵产生的多模泵浦激光转化为单模泵浦激光，从而可以使用输出功率更大、成本更低的多模泵代替输出功率较低且成本较高的单模泵，有助于降低泵浦成本，提高光放饱和出光功率。
图6是本申请提供的光纤放大器的具体示例的另一例结构示意图。
在图5所示的结构中，输入光信号经过双层掺镱光纤、包层泵浦剥除器等一系列新增的、可能带来插损的器件，可能导致能量消耗，NF性能较差。为避免上述情况，本申请提出了如图6所示结构示意图。
如图6(a)所示，多模泵浦单元包括多模泵610，用于产生多模泵浦激光，该多模泵浦激光的波长范围可以是880至980nm。输入单元包括隔离器601，在该实施例中，输入单元还包括波分复用器602，用于将输入光信号(例如1.5μm电信信号)和多模泵浦激光输入双包层光纤(也可以是双包层掺饵光纤)中的纤芯和内包层(即输入谐振放大单元)。谐振放大单元包括双包层掺镱光纤608、包层泵浦剥除器607以及掺铒光纤603，其作用请参照上文的描述，在此不再赘述。输出单元包括光隔离器605，在该实施例中，输出单元还包括波分复用器604，用于将放大后的输入光信号从第一光路中分离输出，并将第一波长范围的单模泵浦激光输入合束器609。
其中，输入单元的波分复用器602和输出单元波分复用器604还可以构成环形谐振腔结构，使得第一波长范围的单模泵浦激光能够在双包层掺镱光纤608和掺铒光纤603构成的第一光路中反复震荡，不断穿过掺铒光纤603，等效地提高了泵浦吸收系数。
如图6(b)所示，输入单元包括隔离器621，在该实施例中，输入单元还包括波分复用器622，其作用请参照图6(a)中的描述，在此不再赘述。谐振放大单元包括光纤光栅624、双包层掺镱光纤627、包层泵浦剥除器626、掺铒光纤623以及光纤光栅628，其各部件的功能可参照图5中的描述，在此不再赘述。
其中，光纤光栅624和光纤光栅628可以构成谐振腔结构，由于光纤光栅624和光纤光栅628对第一波长范围的单模泵浦激光的高反特性，使得第一波长范围的单模泵浦激光可以在双包层掺镱光纤627和掺铒光纤623构成的第一光路中反复震荡，不断穿过掺铒光纤623，等效地提高了泵浦吸收系数。
根据本申请的光纤放大器，通过将多模泵产生的多模泵浦激光转化为单模泵浦激光，从而可以使用输出功率更大、成本更低的多模泵代替输出功率较低且成本较高的单模泵，有助于降低泵浦成本，提高光放饱和出光功率。进一步地，在该实施例中，输入光信号不再经过双包层掺镱光纤、包层泵浦剥除器等一系列新增的、可能带来插损的器件，NF性能上限更优。
图7是本申请提供的光纤放大器的多级结构的一例结构示意图。
如图7(a)所示，光纤放大器的结构由单级结构变为多级结构，其中，输入光信号经过上述图5或图6所示的单级光纤放大器放大后，可以经由增益平坦滤波器(gain flattening filter，GFF)702实现增益整形，以及可调光衰减器(variable optical attenuator，VOA)703调节光功率，再进入第二级的单级放大器进行放大。以此类推，可叠加多级结构，各放大器之间可设置GFF和VOA，不同级数的放大器可分别采用图5或图6所示的单级光纤放大器。其中， GFF和VOA可以属于前级光纤放大器的输出单元，此时输出单元还具有对输出的放大后的输入光信号进行增益整形以及调节光功率的功能。
根据本申请的光纤放大器，通过将多模泵产生的多模泵浦激光转化为单模泵浦激光，从而可以使用输出功率更大、成本更低的多模泵代替输出功率较低且成本较高的单模泵，有助于降低泵浦成本，提高光放饱和出光功率。进一步地，在该实施例中，输入光信号可以经过多个光纤放大器进行放大，有助于降低泵浦成本，提高光放饱和出光功率。
此外，如图7(b)所示，为进一步降低成本，不同级光纤放大器还可以利用波分复用器将单模泵浦激光连接成一个单模泵浦激光环路715，实现双包层掺镱光纤、包层泵浦剥离器等器件的复用。
图8是本申请提供的光纤放大器的多组阵列结构的一例结构示意图。
如图8所示，光纤放大器由单组变为多组的阵列形式，多组输入光信号并行地经图5或图6所示的光纤放大器放大。例如，如图8(a)所示，由于多模泵801具备高功率的输出能力(可达上百瓦)，因此，可以通过分束器802，将多模泵801产生的多模泵浦激光按照一定的能量比分配至不同的光纤放大器作为泵浦输入，例如，光纤放大器803、光纤放大器804以及光纤放大器805。
根据本申请的光纤放大器，通过将多模泵产生的多模泵浦激光转化为单模泵浦激光，从而可以使用输出功率更大、成本更低的多模泵代替输出功率较低且成本较高的单模泵，有助于降低泵浦成本，提高光放饱和出光功率。进一步地，在该实施例中，通过分束器将单个多模泵产生的多模泵浦激光按照一定的能量比分配至不同的光纤放大器作为泵浦输入，可以大幅度提升系统的集成度，降低泵浦成本。
此外，如图8(b)所示，为进一步降低成本，多组光纤放大器还可以共用多模泵的转换部分，减少双包层掺镱光纤及无源器件的用量。
图9是本申请提供的放大光信号的方法的一例示意性流程图。
S910，接收输入光信号，并将该输入光信号输入到第一光路。
具体地，该输入光信号可以是上一段光纤链路中的传输光信号，也可以是激光器直接输出的光信号。
S920，产生多模泵浦激光。
其中，在本申请实施例中，可以通过多模泵产生多模泵浦激光。
可选地，该多模泵浦激光的波长范围可以是880至980nm。
S930，根据多模泵浦激光生成第一波长范围的单模泵浦激光，将第一波长范围的单模泵浦激光在第一光路中反复振荡，以使得第一波长范围的单模泵浦激光放大输入光信号。
可选地，第一波长范围可以是970至1030nm。
根据本申请所提供的技术方案，能够根据多模泵浦激光产生波长范围为970至1030nm的单模泵浦激光，用于放大输入光信号，NF性能较好，能够满足电信级光纤放大器的要求。
其中，该第一光路可以包括双包层掺镱光纤和掺铒光纤。双包层掺镱光纤用于吸收多模泵浦激光，产生和放大第一波长范围的单模泵浦激光；掺铒光纤用于吸收第一波长范围的单模泵浦激光，放大输入光信号。
根据本申请所提供的技术方案，能够直接复用现有电信级光纤放大器中的单模掺铒光纤，保障其可工作光谱带宽与现有产品一致。
其中，在上述方法中可以通过谐振腔结构使得单模泵浦激光能够在第一光路中振荡。
作为一种可能的实现方式，谐振腔可以包括第一光纤光栅和第二光纤光栅，第一光纤光栅和第二光纤光栅对第一波长范围的单模泵浦激光的反射率大于第一阈值，第一光纤光栅和第二光纤光栅对放大后的输入光信号的透射率大于第二阈值。
作为示例而非限定，第一阈值可以为90％，第二阈值可以为90％。这样，第一光纤光栅和第二光纤光栅对第一波长范围的单模泵浦激光具有较高的反射率(例如，反射率≥90％)，使得第一波长范围的单模泵浦激光可以在谐振腔中反复震荡，反复穿过掺铒光纤，能够大幅度提高掺铒光纤对单模泵浦激光的吸收，从而提高了泵浦吸收系数，同时由于第一光纤光栅和第二光纤光栅对放大后的输入光信号具有较高的透射率(例如，透射率≥90％)，使得输入光信号在谐振腔中被放大后，可以顺利的输出，并保证放大后的光信号的NF性能。
应理解，在本申请实施例中，还可以根据光纤长度以及对放大后的输入光信号的参数要求等条件，调整上述第一阈值和第二阈值。例如，当掺镱光纤较长时，可以降低第一阈值；当掺饵光纤较长，可以升高第一阈值。又例如，当要求放大后的输入光信号的NF性能较高时，可以升高第二阈值，反之，可以降低第二阈值。
可选的，第一光纤光栅和第二光纤光栅的波长差值小于第一光纤光栅和第二光纤光栅的反射带宽。
作为另一种可能的实现方式，谐振腔可以包括第一波分复用器和第二波分复用器，第一波分复用器，用于将输入光信号和多模泵浦激光(和/或第一波长范围的单模泵浦激光)耦合进第一光路；第二波分复用器，用于将放大后的输入光信号从第一光路中分离并输出，并将第一波长范围的单模泵浦激光输送给第一波分复用器。
可选地，掺铒光纤为以下任一项：单模掺饵光纤、大模场掺铒光纤、双包层掺铒光纤。
S940，输出放大后的输入光信号。
其中，该放大后的输入光信号可以直接输入到下一段光纤链路继续传输，也可以直接输出，用于控制或者探测。
根据本申请的光纤放大器，通过将多模泵产生的多模泵浦激光转化为单模泵浦激光，从而可以使用输出功率更大、成本更低的多模泵代替输出功率较低且成本较高的单模泵，有助于降低泵浦成本，提高光放饱和出光功率。
本申请实施例还提供了一种装置，包括处理器和接口。所述处理器可用于执行上述方法实施例中的方法。
应理解，上述处理装置可以是一个芯片。例如，该处理装置可以是现场可编程门阵列(field programmable gate array，FPGA)，可以是专用集成芯片(application specific integrated circuit，ASIC)，还可以是系统芯片(system on chip，SoC)，还可以是中央处理器(central processor unit，CPU)，还可以是网络处理器(network processor，NP)，还可以是数字信号处理电路(digital signal processor，DSP)，还可以是微控制器(micro controller unit，MCU)，还可以是可编程控制器(programmable logic device，PLD)或其他集成芯片。
在实现过程中，上述方法的各步骤可以通过处理器中的硬件的集成逻辑电路或者软件形式的指令完成。结合本申请实施例所公开的方法的步骤可以直接体现为硬件处理器执行完成，或者用处理器中的硬件及软件模块组合执行完成。软件模块可以位于随机存储器，闪存、只读存储器，可编程只读存储器或者电可擦写可编程存储器、寄存器等本领域成熟的存储介质 中。该存储介质位于存储器，处理器读取存储器中的信息，结合其硬件完成上述方法的步骤。为避免重复，这里不再详细描述。
应注意，本申请实施例中的处理器可以是一种集成电路芯片，具有信号的处理能力。在实现过程中，上述方法实施例的各步骤可以通过处理器中的硬件的集成逻辑电路或者软件形式的指令完成。上述的处理器可以是通用处理器、数字信号处理器(DSP)、专用集成电路(ASIC)、现场可编程门阵列(FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件。可以实现或者执行本申请实施例中的公开的各方法、步骤及逻辑框图。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。结合本申请实施例所公开的方法的步骤可以直接体现为硬件译码处理器执行完成，或者用译码处理器中的硬件及软件模块组合执行完成。软件模块可以位于随机存储器，闪存、只读存储器，可编程只读存储器或者电可擦写可编程存储器、寄存器等本领域成熟的存储介质中。该存储介质位于存储器，处理器读取存储器中的信息，结合其硬件完成上述方法的步骤。
可以理解，本申请实施例中的存储器可以是易失性存储器或非易失性存储器，或可包括易失性和非易失性存储器两者。其中，非易失性存储器可以是只读存储器(read-only memory，ROM)、可编程只读存储器(programmable ROM，PROM)、可擦除可编程只读存储器(erasable PROM，EPROM)、电可擦除可编程只读存储器(electrically EPROM，EEPROM)或闪存。易失性存储器可以是随机存取存储器(random access memory，RAM)，其用作外部高速缓存。通过示例性但不是限制性说明，许多形式的RAM可用，例如静态随机存取存储器(static RAM，SRAM)、动态随机存取存储器(dynamic RAM，DRAM)、同步动态随机存取存储器(synchronous DRAM，SDRAM)、双倍数据速率同步动态随机存取存储器(double data rate SDRAM，DDR SDRAM)、增强型同步动态随机存取存储器(enhanced SDRAM，ESDRAM)、同步连接动态随机存取存储器(synchlink DRAM，SLDRAM)和直接内存总线随机存取存储器(direct rambus RAM，DR RAM)。应注意，本文描述的系统和方法的存储器旨在包括但不限于这些和任意其它适合类型的存储器。
根据本申请实施例提供的方法，本申请还提供一种计算机程序产品，该计算机程序产品包括：计算机程序代码，当该计算机程序代码在计算机上运行时，使得该计算机执行图9所示实施例的方法。
根据本申请实施例提供的方法，本申请还提供一种计算机可读介质，该计算机可读介质存储有程序代码，当该程序代码在计算机上运行时，使得该计算机执行图9所示实施例的方法。
在上述实施例中，可以全部或部分地通过软件、硬件、固件或者其任意组合来实现。当使用软件实现时，可以全部或部分地以计算机程序产品的形式实现。所述计算机程序产品包括一个或多个计算机指令。在计算机上加载和执行所述计算机指令时，全部或部分地产生按照本申请实施例所述的流程或功能。所述计算机可以是通用计算机、专用计算机、计算机网络、或者其他可编程装置。所述计算机指令可以存储在计算机可读存储介质中，或者从一个计算机可读存储介质向另一个计算机可读存储介质传输，例如，所述计算机指令可以从一个网站站点、计算机、服务器或数据中心通过有线(例如同轴电缆、光纤、数字用户线(digital subscriber line，DSL))或无线(例如红外、无线、微波等)方式向另一个网站站点、计算机、服务器或数据中心进行传输。所述计算机可读存 储介质可以是计算机能够存取的任何可用介质或者是包含一个或多个可用介质集成的服务器、数据中心等数据存储设备。所述可用介质可以是磁性介质(例如，软盘、硬盘、磁带)、光介质(例如，高密度数字视频光盘(digital video disc，DVD))、或者半导体介质(例如，固态硬盘(solid state disc，SSD))等。
在本说明书中使用的术语“部件”、“模块”、“系统”等用于表示计算机相关的实体、硬件、固件、硬件和软件的组合、软件、或执行中的软件。例如，部件可以是但不限于，在处理器上运行的进程、处理器、对象、可执行文件、执行线程、程序和/或计算机。通过图示，在计算设备上运行的应用和计算设备都可以是部件。一个或多个部件可驻留在进程和/或执行线程中，部件可位于一个计算机上和/或分布在两个或更多个计算机之间。此外，这些部件可从在上面存储有各种数据结构的各种计算机可读介质执行。部件可例如根据具有一个或多个数据分组(例如来自与本地系统、分布式系统和/或网络间的另一部件交互的二个部件的数据，例如通过信号与其它系统交互的互联网)的信号通过本地和/或远程进程来通信。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各种说明性逻辑块(illustrative logical block)和步骤(step)，能够以电子硬件、或者计算机软件和电子硬件的结合来实现。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本申请的范围。
所属领域的技术人员可以清楚地了解到，为描述的方便和简洁，上述描述的系统、装置和单元的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。
在本申请所提供的几个实施例中，应该理解到，所揭露的系统、装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本申请各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以所述权利要求的保护范围为准。

Claims (14)

  1. 一种光纤放大器，其特征在于，包括：
    多模泵浦单元，用于产生多模泵浦激光；
    输入单元，用于将输入光信号和所述多模泵浦激光输入到第一光路，所述第一光路属于谐振放大单元；
    所述谐振放大单元，用于根据所述多模泵浦激光生成第一波长范围的单模泵浦激光，将所述第一波长范围的单模泵浦激光在所述第一光路中反复振荡，以使得所述第一波长范围的单模泵浦激光放大所述输入光信号；
    输出单元，用于输出放大后的输入光信号。
  2. 根据权利要求1所述的光纤放大器，其特征在于，所述多模泵浦激光的波长范围为880至980nm，所述第一波长范围为970至1030nm。
  3. 根据权利要求1或2所述的光纤放大器，其特征在于，所述第一光路包括：
    双包层掺镱光纤，用于吸收所述多模泵浦激光，产生和放大所述第一波长范围的单模泵浦激光；
    掺铒光纤，用于吸收所述第一波长范围的单模泵浦激光，放大输入光信号。
  4. 根据权利要求3所述的光纤放大器，其特征在于，所述谐振放大单元还包括包层泵浦剥离器，用于剥除所述双包层掺镱光纤未吸收的所述多模泵浦激光。
  5. 根据权利要求4所述的光纤放大器，其特征在于，所述包层泵浦剥离器位于所述掺铒光纤和所述双包层掺镱光纤之间。
  6. 根据权利要求1至5中任一项所述的光纤放大器，其特征在于，所述谐振放大单元包括谐振腔，所述谐振放大单元通过所述谐振腔将所述第一波长范围的单模泵浦激光在所述第一光路中反复振荡。
  7. 根据权利要求6所述的光纤放大器，其特征在于，所述谐振腔包括第一光纤光栅和第二光纤光栅，所述第一光纤光栅和所述第二光纤光栅对所述第一波长范围的单模泵浦激光的反射率大于第一阈值，所述第一光纤光栅和所述第二光纤光栅对所述放大后的输入光信号的透射率大于第二阈值。
  8. 根据权利要求7所述的光纤放大器，其特征在于，所述第一光纤光栅和所述第二光纤光栅的波长差值小于所述第一光纤光栅和所述第二光纤光栅的反射带宽。
  9. 根据权利要求1至6中任一项所述的光纤放大器，其特征在于，所述输入单元还包括第一波分复用器，用于将所述输入光信号和所述多模泵浦激光耦合进所述第一光路。
  10. 根据权利要求9所述的光纤放大器，其特征在于，所述输出单元还包括第二波分复用器，用于将所述放大后的输入光信号从所述第一光路中分离并输出。
  11. 根据权利要求1至10中任一项所述的光纤放大器，其特征在于，所述输出单元还包括增益平坦滤波器和/或可调光衰减器。
  12. 根据权利要求1至11中任一项所述的光纤放大器，其特征在于，所述掺铒光纤为以下任一项：
    单模掺饵光纤、大模场掺铒光纤、双包层掺铒光纤。
  13. 一种放大光信号的方法，其特征在于，包括：
    接收输入光信号，并将所述输入光信号输入到第一光路；
    产生多模泵浦激光；
    根据所述多模泵浦激光生成第一波长范围的单模泵浦激光，将第一波长范围的单模泵浦激光在所述第一光路中反复振荡，以使得所述第一波长范围的单模泵浦激光放大所述输入光信号；
    输出放大后的输入光信号。
  14. 一种光纤通信系统，其特征在于，包括：
    多芯传输光纤，所述多芯传输光纤用于传输输入光信号；
    光放站点，所述光放站点包括如权利要求1至12中任一项所述的光纤放大器，所述光纤放大器用于放大所述输入光信号。
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