Backward pumping fiber laser amplification device

Abstract

The invention relates to a backward pumping fiber laser amplification device which comprises a signal light collimation module, a pumping light collimation module, a coupling module and a monitoring and feedback control circuit. The coupling module is arranged between the signal light collimation module and the pump light collimation module; pump light generated by the pump light collimation module passes through the coupling module, then coincides with a light path of the signal light collimation module, and enters a gain optical fiber in the signal light collimation module in the direction opposite to the signal light so as to achieve signal power amplification. The monitoring and feedback control circuit is used for monitoring the power fluctuation of the pump light and the signal light in real time and adjusting the pump diode in the pump light collimation module through negative feedback.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber lasers, and in particular to a backward pumped optical fiber laser amplification device. Background Art

[0002] In the field of ultrafast fiber lasers, backward pumping is an important fiber amplification method. The characteristic of this method is that the pump light source is placed at the back end of the amplifier so that the pump light propagates in the opposite direction to the signal light. This pumping method can effectively utilize the large gain bandwidth of the gain fiber and improve the gain bandwidth and signal-to-noise ratio of the amplifier.

[0003] However, there are the following technical problems in practical applications:

[0004] First, ultrafast fiber lasers have ultra-wide spectral bandwidth and ultra-high pulse peak power. The fiber combiner commonly used in traditional fiber laser amplification will introduce serious mode field mismatch problems when performing forward or backward pumping. This problem is particularly prominent in large mode field gain fiber amplifiers, resulting in a decrease in the output beam quality of the amplifier and a significant decrease in the pulse time domain contrast.

[0005] Secondly, traditional fiber optic device packaging technology usually uses GRIN lenses for laser collimation or focusing. However, the small size and short focal length of GRIN lenses make it difficult to effectively match large-core-diameter and large-mode-field gain fibers, limiting the actual application effect of the system.

[0006] Therefore, it is urgent to develop a new type of backward-pumped spatially coupled fiber amplifier device to solve the above problems. Summary of the invention

[0007] The present invention discloses a backward pumped fiber laser amplification device, which aims to solve the technical problems existing in the prior art. The present invention adopts the following technical solutions:

[0008] In one embodiment of the present invention, a backward pumped fiber laser amplification device is provided, comprising a signal light collimation module, a pump light collimation module, a coupling module and a monitoring and feedback control circuit;

[0009] The coupling module is arranged between the signal light collimation module and the pump light collimation module; the pump light generated by the pump light collimation module coincides with the optical path of the signal light collimation module after passing through the coupling module, and enters the gain optical fiber in the signal light collimation module in the opposite direction to the signal light, so as to realize signal power amplification;

[0010] The monitoring and feedback control circuit is used to monitor the power fluctuation of the pump light and the signal light in real time and adjust the pump diode in the pump light collimation module through negative feedback.

[0011] As a preferred technical solution, the signal light collimation module includes a front-stage optical fiber optical path, a gain optical fiber, a gain optical fiber connector, a signal light collimation sleeve and a signal light collimation lens which are arranged in sequence; the gain optical fiber connector and the signal light collimation lens are fixed in the signal light collimation sleeve;

[0012] The signal light is generated by the previous optical fiber path, enters the gain fiber through optical fiber fusion coupling, the signal light is amplified by the gain fiber and output, and enters the coupling module after passing through the signal light collimating lens.

[0013] As a preferred technical solution, the pump light collimation module includes a pump diode, a pump fiber connector, a pump light collimation sleeve and a pump light collimation lens which are arranged in sequence;

[0014] The pump light is generated by the pump diode, passes through the pump fiber connector and the pump light collimating lens in sequence, and then is output to the coupling module.

[0015] As a preferred technical solution, the coupling module includes a coupling adjustment device, an adjustable dichroic mirror and a fixed dichroic mirror;

[0016] The fixed dichroic mirror is arranged on the optical path of the pump light and is located at the incident end of the adjustable dichroic mirror, and is used to reflect the pump light to the adjustable dichroic mirror; the adjustable dichroic mirror is arranged on the optical path of the signal light, and is used to transmit the amplified signal light and reflect the pump light from the fixed dichroic mirror into the gain fiber, so as to provide pumping for the laser stimulated emission amplification, and to realize the power amplification of the signal light.

[0017] As a preferred technical solution, the coupling adjustment device is used to achieve horizontal and vertical angle adjustment of the adjustable dichroic mirror to ensure high-efficiency coupling of the pump light and the gain fiber;

[0018] The coupling adjustment device includes a fixed base, an elastic O-ring, a dichroic mirror base, and an inclination adjustment screw; the fixed base is connected to a torque device through a surface groove for horizontal rotation, so as to achieve horizontal angle adjustment of the adjustable dichroic mirror; the elastic O-ring is used to connect the fixed base and the dichroic mirror base; the inclination adjustment screw is used to adjust the distance between the fixed base and the dichroic mirror base, so as to achieve vertical inclination adjustment of the adjustable dichroic mirror.

[0019] As a preferred technical solution, the coupling adjustment device further includes a fixing screw, which is used to lock the distance between the fixed base and the dichroic mirror base.

[0020] As a preferred technical solution, it also includes a signal light monitoring device;

[0021] The adjustable dichroic mirror has a transmittance of 95% and a reflectance of 5% for the signal light; the transmitted part directly enters the free space, and the reflected part enters the signal light monitoring device after being transmitted by the fixed dichroic mirror to monitor the power of the signal light.

[0022] As a preferred technical solution, it also includes a pump light monitoring device;

[0023] The fixed dichroic mirror has a reflectivity of 98% and a transmittance of 2% for the pump light; the reflected part is output to the adjustable dichroic mirror, and the transmitted part enters the pump light monitoring device to monitor the power of the pump light.

[0024] As a preferred technical solution, the signal light monitoring device and the pump light monitoring device respectively include photodetectors for converting optical signals into electrical signals and transmitting them to the monitoring and feedback control circuit.

[0025] As a preferred technical solution, the monitoring and feedback control circuit is used to monitor the power fluctuation of the pump light and the signal light according to the electrical signals of the signal light monitoring device and the pump light monitoring device, and adjust the output power of the pump diode.

[0026] One embodiment of the above invention has the following advantages or beneficial effects:

[0027] The present invention mainly provides a backward pumped fiber laser amplification device, which includes a signal light collimation module, a pump light collimation module, a coupling module and a monitoring and feedback control circuit. Through the special arrangement of the adjustable dichroic mirror and the fixed dichroic mirror in the coupling module, the spatial coupling of the pump light and the signal light is realized, and the mode mismatch problem of the traditional fiber combiner in the large mode field fiber is avoided. At the same time, the horizontal and vertical bidirectional precision adjustment function of the coupling adjustment device ensures the high-efficiency coupling of the pump light and the gain fiber.

[0028] Furthermore, the power monitoring function of the signal light and the pump light is integrated in the coupling optical path. Through the reasonable splitting ratio design of the dichroic mirror, the real-time power monitoring of the dual optical paths is realized without affecting the transmission efficiency of the main optical path. Combined with the precise adjustment of the pump diode by the monitoring and feedback control circuit, not only the long-term stability of the system is improved, but also the entire fiber amplifier system can still maintain the stable output efficiency of high-power laser in the temperature change environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments, which constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions explain the present invention and do not constitute improper limitations on the present invention. In the drawings:

[0030] Figure 1A schematic diagram of the optical path of a back-pumped fiber laser amplification device disclosed in one embodiment of the present invention;

[0031] Figure 2 A schematic structural diagram of a post-pumped fiber laser amplification device disclosed in one embodiment of the present invention;

[0032] Figure 3 A schematic diagram of the structure of a coupling module disclosed in one embodiment of the present invention;

[0033] Figure 4 A front view of a coupling adjustment device disclosed in one embodiment of the present invention;

[0034] Figure 5 A side view of a coupling adjustment device disclosed in one embodiment of the present invention;

[0035] Figure 6 A three-dimensional diagram of a coupling adjustment device disclosed in one embodiment of the present invention.

[0036] Description of reference numerals:

[0037] Signal light collimation module 10, front-stage optical fiber optical path 11, gain optical fiber 12, gain optical fiber connector 13, signal light collimation sleeve 14, signal light collimation lens 15, signal light 16, pump light collimation module 20, pump diode 21, pump optical fiber connector 22, pump light collimation sleeve 23, pump light collimation lens 24, pump light 25, coupling module 30, fixed dichroic mirror 31, adjustable dichroic mirror 32, coupling adjustment device 33, fixed base 331, elastic O-ring 332, dichroic mirror base 333, tilt adjustment screw 334, fixing screw 335, monitoring and feedback control circuit 40, pump light monitoring device 51, signal light monitoring device 52. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. In the description of the present invention, it should be noted that the term "or" is usually used in the sense of including "and / or", unless the content clearly indicates otherwise.

[0039] In the description of the present invention, the terms “first”, “second”, etc. are only used to distinguish the descriptions and should not be understood as indicating or implying relative importance.

[0040] Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] The widely used fiber combiners have serious mode mismatch problems in large mode area fiber amplifiers. This mismatch not only leads to a decrease in the quality of the output beam, but also significantly reduces the time domain contrast of the pulse. At the same time, traditional fiber optic device packaging technology usually uses GRIN lenses for laser collimation or focusing, but due to the small size and short focal length of GRIN lenses, it is difficult to effectively match them with large core diameter and large mode area gain fibers. In addition, the existing technology lacks an effective real-time power monitoring and feedback control mechanism, making it difficult for the system to maintain a stable output efficiency under the influence of environmental factors such as temperature changes.

[0042] In order to solve the problems existing in the prior art, reference is made to Figure 1 — Figure 6 The embodiment of the present invention provides a backward pumped fiber laser amplification device, the structure of which at least includes a signal light collimation module 10, a pump light collimation module 20, a coupling module 30 and a monitoring and feedback control circuit 40; wherein the signal light collimation module 10 is used to transmit and amplify the input signal light 16, and collimate the amplified signal light 16 for output; the pump light collimation module 20 is used to generate pump light 25 and collimate it and output it to the coupling module 30; the coupling module 30 is used to realize the spatial coupling of the pump light 25 and the signal light 16, and ensure that the pump light 25 can enter the gain fiber 12 in the opposite direction to the signal light 16, and also has a splitting function, which is used to separate part of the signal light 16 and the pump light 25 for power monitoring; the monitoring and feedback control circuit 40 is used to receive the power information of the separated signal light 16 and the pump light 25, and adjust the output power of the pump diode 21 in the pump light collimation module 20 through negative feedback control to achieve stable operation of the system.

[0043] like Figure 1 , Figure 2 Preferably, the coupling module 30 is arranged between the signal light collimation module 10 and the pump light collimation module 20. The pump light 25 generated by the pump light collimation module 20 coincides with the optical path of the signal light collimation module 10 after passing through the coupling module 30, and enters the gain optical fiber 12 in the signal light collimation module 10 in the opposite direction to the signal light 16, so as to realize signal power amplification.

[0044] In a preferred embodiment, the signal light collimation module 10 includes a front-stage optical fiber path 11, a gain optical fiber 12, a gain optical fiber connector 13, a signal light collimation sleeve 14 and a signal light collimation lens 15 which are arranged in sequence; wherein the signal light is generated by the front-stage optical fiber path 11, and is connected to the gain optical fiber 12 by optical fiber fusion splicing, the gain optical fiber 12 is used to achieve power amplification of the signal light 16, the output end of the gain optical fiber 12 is fixed in the signal light collimation sleeve 14 through the gain optical fiber connector 13, the signal light collimation lens 15 is also fixed in the signal light collimation sleeve 14, the signal light collimation lens 15 is used to collimate the output amplified signal light 16 and transmit it to the coupling module 30, and the signal light collimation sleeve 14 is used to provide a stable mechanical installation reference for the optical element.

[0045] In a preferred embodiment, the pump light collimation module 20 includes a pump diode 21, a pump fiber connector 22, a pump light collimation sleeve 23 and a pump light collimation lens 24 which are arranged in sequence; the pump light 25 is generated by the pump diode 21 and transmitted through the pump fiber, and the pump fiber is fixed in the pump light collimation sleeve 23 through the pump fiber connector 22. The pump light collimation lens 24 is also fixed in the pump light collimation sleeve 23, and is used to collimate the output pump light 25 and transmit it to the coupling module 30.

[0046] Preferably, the optical paths of the signal light collimation module 10 and the pump light collimation module 20 are kept parallel, which enables the coupling module 30 to achieve precise spatial overlap of the pump light 25 and the signal light 16 on the one hand, and is conducive to folding the optical path in a limited space, making the entire device structure more compact.

[0047] In a preferred embodiment, the coupling module 30 includes a coupling adjustment device 33, an adjustable dichroic mirror 32 and a fixed dichroic mirror 31; wherein the fixed dichroic mirror 31 is arranged on the optical path of the pump light 25 and is located at the incident end of the adjustable dichroic mirror 32. The pump light 25 from the pump light collimation module 20 is first irradiated onto the fixed dichroic mirror 31, and enters the adjustable dichroic mirror 32 after being reflected by the fixed dichroic mirror 31. At the same time, the amplified signal light 16 from the signal light collimation module 10 is directly irradiated onto the adjustable dichroic mirror 32. The setting of the adjustable dichroic mirror 32 enables 95% of the signal light 16 to be transmitted through, while reflecting the pump light 25 from the fixed dichroic mirror 31, thereby achieving spatial overlap of the pump light 25 and the signal light 16, and ensuring that the pump light 25 can enter the gain fiber 12 in the opposite direction to the signal light 16, providing pumping for laser stimulated emission amplification, and realizing power amplification of the signal light 16.

[0048] Preferably, the adjustable dichroic mirror 32 and the fixed dichroic mirror 31 are the same type of 45° incident angle reflectors, wherein the adjustable dichroic mirror 32 has a high reflectivity (≥99%) for the pump light 25 with a wavelength of 976nm, and has a transmittance of 95% and a reflectivity of 5% for the signal light 16 with a wavelength of 1030nm; the fixed dichroic mirror 31 has a reflectivity of 98% and a transmittance of 2% for the pump light 25 with a wavelength of 976nm, and has a high transmittance (≥95%) for the signal light 16 with a wavelength of 1030nm.

[0049] like Figure 1 , Figure 3 — Figure 6 In a preferred embodiment, the fixed dichroic mirror 31 is placed at an angle of 45° on the optical path of the pump light 25, and the pump light 25 is reflected 90° and then incident on the adjustable dichroic mirror 32; the adjustable dichroic mirror 32 is also placed at an angle of 45° on the optical path of the signal light 16, and 95% of the signal light 16 is transmitted into the free space, and at the same time, the pump light 25 from the fixed dichroic mirror 31 is reflected 90° and then overlaps with the optical path of the signal light 16; the 2% pump light 25 transmitted through the fixed dichroic mirror 31 and the 5% signal light 16 reflected from the adjustable dichroic mirror 32 are respectively used for real-time power monitoring. This design of lens arrangement and splitting ratio not only ensures the transmission efficiency of the main optical path, but also realizes the power monitoring function of the dual optical paths.

[0050] In a preferred embodiment, the coupling adjustment device 33 is used to achieve horizontal and vertical angle adjustment of the adjustable dichroic mirror 32 to ensure high-efficiency coupling of the pump light 25 with the gain fiber 12 .

[0051] like Figure 3 — Figure 6 Preferably, the coupling adjustment device 33 includes a fixed base 331, an elastic O-ring 332, a dichroic mirror base 333, a fixing screw 335 and an inclination adjustment screw 334; wherein the adjustable dichroic mirror 32 is fixed on the dichroic mirror base 333, and the dichroic mirror base 333 is connected to the fixed base 331 through the elastic O-ring 332; a groove is provided at the bottom of the fixed base 331, which is connected to the torque device through the groove to realize the rotation adjustment of the adjustable dichroic mirror 32 in the horizontal plane; a plurality of inclination adjustment screws 334 are installed between the fixed base 331 and the dichroic mirror base 333 in a circumferentially uniformly distributed manner, and by adjusting the distance between the inclination adjustment screw 334 and the base, the adjustable dichroic mirror 32 can be accurately adjusted in the vertical direction; the fixing screw 335 is used to lock the relative position between the fixed base 331 and the dichroic mirror base 333 after the adjustment is completed, so as to achieve long-term structural stability. In this embodiment, the structure of the torque device is not specifically limited, and those skilled in the art may select any implementation method disclosed in the prior art.

[0052] In a preferred embodiment, the backward-pumped fiber laser amplifier device also includes a signal light monitoring device 52 and a pump light monitoring device 51; the signal light monitoring device 52 is arranged on the transmission light path of the fixed dichroic mirror 31, and is used to receive the 5% signal light 16 reflected by the adjustable dichroic mirror 32 and transmitted through the fixed dichroic mirror 31, so as to perform power monitoring of the signal light 16; the pump light monitoring device 51 is arranged on the transmission light path of the fixed dichroic mirror 31, and is used to receive the 2% pump light 25 transmitted through the fixed dichroic mirror 31, so as to perform power monitoring of the pump light 25.

[0053] Preferably, the signal light monitoring device 52 and the pump light monitoring device 51 are both photoelectric detectors for converting received optical signals into electrical signals, which are transmitted to the monitoring and feedback control circuit 40 via a coaxial cable. The monitoring and feedback control circuit 40 calculates the power ratio of the pump light 25 to the signal light 16 based on the received signal, and adjusts the output power of the pump diode 21 in real time accordingly, thereby forming a closed-loop feedback control system to ensure that the system can maintain a stable output efficiency when the external environment changes such as temperature changes.

[0054] In a preferred embodiment, the monitoring and feedback control circuit 40 mainly includes a signal acquisition module, a microprocessor control unit and a drive circuit.

[0055] Specifically, the signal acquisition module is connected to the signal light monitoring device 52 and the pump light monitoring device 51 respectively, and receives and processes the electrical signals from the two photodetectors; the microprocessor control unit calculates the power ratio of the two optical signals in real time, and compares the ratio with the preset threshold value. When the power ratio deviates from the preset range, the microprocessor control unit will output a corresponding control signal to the drive circuit. The drive circuit adjusts the injection current of the pump diode 21 accordingly according to the received control signal, thereby adjusting its output power, effectively suppressing the output power instability of the system caused by factors such as temperature fluctuations, and ensuring the long-term stable operation of the laser amplifier.

[0056] In the above embodiment, the spatial coupling of the pump light 25 and the signal light 16 is achieved through the special arrangement of the adjustable dichroic mirror 32 and the fixed dichroic mirror 31 in the coupling module 30, thereby avoiding the mode mismatch problem of the conventional fiber combiner in the large mode field fiber. At the same time, the horizontal and vertical bidirectional precision adjustment function of the coupling adjustment device 33 ensures the high-efficiency coupling of the pump light 25 and the gain fiber 12.

[0057] Furthermore, the power monitoring function of the signal light 16 and the pump light 25 is integrated in the coupling optical path, and the real-time power monitoring of the dual optical paths is realized without affecting the transmission efficiency of the main optical path through the reasonable splitting ratio design of the dichroic mirror. The precise adjustment of the pump diode 21 by the monitoring and feedback control circuit 40 not only improves the long-term stability of the system, but also enables the entire optical fiber amplifier system to maintain the stable output efficiency of the high-power laser in a temperature-changing environment.

[0058] Finally, the backward-pumped fiber laser amplification device provided in the embodiment of the present invention adopts a modular design, the connection between the functional components is stable and reliable, installation and debugging are convenient, it has good engineering practicality, is suitable for large-scale production, and the overall structure is compact and has strong environmental adaptability, and can operate stably for a long time under complex working conditions.

[0059] Although example embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above example embodiments are merely exemplary and are not intended to limit the scope of the present application to this. Those of ordinary skill in the art may make various changes and modifications therein without departing from the scope and spirit of the present application. All these changes and modifications are intended to be included within the scope of the present application as required by the appended claims.

[0060] In the description provided herein, a large number of specific details are described. However, it is understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0061] Similarly, it should be understood that in order to streamline the present application and help understand one or more of the various inventive aspects, in the description of the exemplary embodiments of the present application, the various features of the present application are sometimes grouped together into a single embodiment, figure, or description thereof. However, the method of the present application should not be interpreted as reflecting the following intention: the claimed application requires more features than the features clearly stated in each claim. More specifically, as reflected in the corresponding claims, the inventive point is that the corresponding technical problem can be solved with features less than all the features of a single disclosed embodiment. Therefore, the claims following the specific embodiment are hereby explicitly incorporated into the specific embodiment, wherein each claim itself serves as a separate embodiment of the present application.

[0062] It will be understood by those skilled in the art that, except for mutually exclusive features, all features disclosed in this specification (including the accompanying claims, abstracts and drawings) and all processes or units of any method or device disclosed in this specification may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstracts and drawings) may be replaced by an alternative feature that provides the same, equivalent or similar purpose.

Claims

1. A backward pumped fiber laser amplifier, characterized in that: It includes a signal light collimation module, a pump light collimation module, a coupling module and a monitoring and feedback control circuit; The coupling module is arranged between the signal light collimation module and the pump light collimation module; the pump light generated by the pump light collimation module coincides with the optical path of the signal light collimation module after passing through the coupling module, and enters the gain optical fiber in the signal light collimation module in the opposite direction to the signal light, so as to realize signal power amplification; The monitoring and feedback control circuit is used to monitor the power fluctuations of the pump light and the signal light in real time, and to adjust the pump diode in the pump light collimation module through negative feedback.

2. The backward pumped fiber laser amplification device according to claim 1, characterized in that: The signal light collimation module comprises a front-stage optical fiber optical path, the gain optical fiber, the gain optical fiber connector, a signal light collimation sleeve and a signal light collimation lens which are arranged in sequence; the gain optical fiber connector and the signal light collimation lens are fixed in the signal light collimation sleeve; The signal light is generated by the preceding optical fiber optical path, enters the gain optical fiber through optical fiber fusion coupling, the signal light is amplified by the gain optical fiber and then output, and enters the coupling module after passing through the signal light collimating lens.

3. The backward pumped fiber laser amplification device according to claim 1, characterized in that: The pump light collimation module comprises the pump diode, the pump fiber connector, the pump light collimation sleeve and the pump light collimation lens which are arranged in sequence; The pump light is generated by the pump diode, passes through the pump fiber connector and the pump light collimating lens in sequence, and is then output to the coupling module.

4. The backward pumped fiber laser amplification device according to claim 2, characterized in that: The coupling module comprises a coupling adjustment device, an adjustable dichroic mirror and a fixed dichroic mirror; The fixed dichroic mirror is arranged on the optical path of the pump light and is located at the incident end of the adjustable dichroic mirror, and is used to reflect the pump light to the adjustable dichroic mirror; the adjustable dichroic mirror is arranged on the optical path of the signal light, and is used to transmit the amplified signal light, and reflect the pump light from the fixed dichroic mirror into the gain optical fiber, so as to provide pumping for laser stimulated emission amplification, and realize power amplification of the signal light.

5. The backward pumped fiber laser amplification device according to claim 4, characterized in that: The coupling adjustment device is used to achieve horizontal and vertical angle adjustment of the adjustable dichroic mirror to ensure high-efficiency coupling of the pump light with the gain optical fiber; The coupling adjustment device includes a fixed base, an elastic O-ring, a dichroic mirror base, and an inclination adjustment screw; the fixed base is connected to a torque device through a surface groove for horizontal rotation, so as to achieve horizontal angle adjustment of the adjustable dichroic mirror; the elastic O-ring is used to connect the fixed base and the dichroic mirror base; the inclination adjustment screw is used to adjust the distance between the fixed base and the dichroic mirror base, so as to achieve vertical inclination adjustment of the adjustable dichroic mirror.

6. The backward pumped fiber laser amplification device according to claim 5, characterized in that: The coupling adjustment device further comprises a fixing screw, and the fixing screw is used to lock the distance between the fixing base and the dichroic mirror base.

7. The backward pumped fiber laser amplification device according to claim 4, characterized in that: Also included is a signal light monitoring device; The adjustable dichroic mirror has a transmittance of 95% and a reflectance of 5% for the signal light; the transmitted part directly enters the free space, and the reflected part enters the signal light monitoring device after being transmitted by the fixed dichroic mirror to monitor the power of the signal light.

8. The backward pumped fiber laser amplification device according to claim 7, characterized in that: Also included is a pump light monitoring device; The fixed dichroic mirror has a reflectivity of 98% and a transmittance of 2% for the pump light; wherein the reflected part is output to the adjustable dichroic mirror, and the transmitted part enters the pump light monitoring device to perform power monitoring of the pump light.

9. The backward pumped fiber laser amplification device according to claim 8, characterized in that: The signal light monitoring device and the pump light monitoring device respectively include a photodetector for converting an optical signal into an electrical signal and transmitting the electrical signal to the monitoring and feedback control circuit.

10. The backward pumped fiber laser amplification device according to claim 9, characterized in that: The monitoring and feedback control circuit is used to monitor the power fluctuation of the pump light and the signal light according to the electrical signals of the signal light monitoring device and the pump light monitoring device, and to adjust the output power of the pump diode.

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