All-fiber amplifier capable of improving photon darkening resistance

Abstract

In order to solve the problem of output performance degradation of an existing fiber laser amplifier in a high-radiation environment, especially the problems of laser efficiency reduction and light beam quality degradation caused by radiation induction defects, the invention provides an all-fiber amplifier for improving photon darkening resistance. According to the laser, the bleaching light circulator is connected behind the gain optical fiber of the amplifier, so that the bleaching laser can circularly enter the gain optical fiber of the amplifier in a reciprocating manner, and circular bleaching of the gain optical fiber is realized, so that the light bleaching efficiency can be effectively improved, and the energy density of the bleaching light in the gain optical fiber can be enhanced; and the anti-darkening performance and the working life of the all-fiber amplifier in a high-radiation environment are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber lasers, and in particular to an all-optical fiber amplifier with improved anti-photon darkening performance. Background Art

[0002] With the continuous exploration of space by human beings and the rapid development of space technology, the application breadth and scenarios of fiber lasers in the space field have greatly increased, such as space laser communications, lidar, space waste disposal, fiber laser gyroscopes, etc. However, the space environment is very harsh, mainly manifested in that fiber lasers will be irradiated by high-energy electromagnetic radiation (X-rays, gamma rays) and charged particles (positrons, protons, alpha particles, etc.). The highest-energy rays such as gamma rays and X-rays have the greatest impact on the active optical fiber in the laser. Rare earth-doped active optical fibers will produce various types of defects (or "color centers") under space irradiation conditions, resulting in increased losses and reduced output power and service life of fiber lasers.

[0003] High-power fiber lasers for space applications are affected not only by the radiation-induced darkening effect, but also by the photon darkening effect. As the operation time of high-power lasers increases, the output power of the fiber laser decreases rapidly and gradually reaches a stable state due to the increase in background loss in the doped fiber core. This phenomenon is the photon darkening effect. The photon darkening effect will cause the laser light threshold to increase, the system stability to decrease, and the working life to shorten, which limits the industrial application and development of high-power fiber lasers.

[0004] As a potential solution to achieve anti-darkening fiber lasers, photobleaching technology is based on the principle of using light of a specific wavelength to irradiate the optical fiber to reduce or repair ion defects induced by radiation or photon darkening. However, the efficiency and practicality of existing photobleaching technology are limited by the injection method and energy density of the bleaching light. When low-power-density bleaching light is injected into the laser system, due to the inherent loss of the bleaching light in the optical fiber device, the low-power-density bleaching light has limited ability to repair ion defects caused by darkening, making it difficult to achieve efficient and stable bleaching effects. Summary of the invention

[0005] In order to solve the output performance attenuation problem encountered by existing fiber laser amplifiers in high radiation environments, especially the problem of laser efficiency reduction and beam quality degradation caused by radiation-induced defects, the present invention proposes an all-fiber amplifier with improved anti-photon darkening performance. The laser is connected to a bleaching light circulator behind the gain fiber of the amplifier, so that the bleaching laser can circulate back and forth into the gain fiber of the amplifier, thereby achieving cyclic and efficient bleaching of the gain fiber, thereby improving the anti-darkening performance of the all-fiber amplifier in radiation environments and photon darkening conditions.

[0006] In order to achieve the above technical purpose, the technical solution adopted by the present invention is:

[0007] On the one hand, the present invention provides an all-fiber amplifier with improved anti-photon darkening performance, comprising a seed laser, a bleaching light source, a wavelength division multiplexer, a forward pump signal combiner, a gain fiber, a fiber-coupled semiconductor laser, and a bleaching light circulator; the forward pump signal combiner has a signal input fiber, a signal output fiber, and at least one pump energy transmission fiber;

[0008] The seed laser and the bleaching light source are connected to a wavelength division multiplexer, the wavelength division multiplexer energy transmission fiber is connected to the signal input fiber of the forward pump signal combiner, and each pump energy transmission fiber of the forward pump signal combiner is connected to a fiber-coupled semiconductor laser; one end of the gain fiber is connected to the signal output fiber of the forward pump signal combiner, and the other end is connected to the signal input fiber of the bleaching light circulator, the bleaching laser output by the bleaching light source and the pump light output by multiple fiber-coupled semiconductor lasers are transmitted in the cladding of the gain fiber, and the signal laser output by the seed laser is transmitted in the core of the gain fiber;

[0009] The bleaching light circulator has a pump energy transmission fiber closed loop. The incompletely absorbed bleaching laser output to the bleaching light circulator through the fiber cladding of the gain fiber re-enters the gain fiber through the pump energy transmission fiber closed loop in the bleaching light circulator, thereby realizing cyclic bleaching of the gain fiber. The signal laser output through the core of the gain fiber is output through the signal output fiber of the bleaching light circulator.

[0010] Preferably, the bleaching light circulator includes a fiber bundle end, a signal fiber and at least one pair of pump energy transmission fibers, the signal fiber includes a signal input fiber and a signal output fiber, the two pairs of pump energy transmission fibers are fused in pairs to form a pump energy transmission fiber closed loop, the pump energy transmission fibers are fused in pairs to form a pump energy transmission fiber fusion point, the gain fiber is connected to the signal input fiber of the bleaching light circulator, the signal laser output through the core of the gain fiber is output through the signal input fiber and the signal output fiber of the bleaching light circulator, the laser output through the cladding of the gain fiber re-enters the gain fiber through the pump energy transmission fiber closed loop of the bleaching light circulator. Further, it also includes a cladding light filter and a fiber end cap, the signal output fiber of the bleaching light circulator is connected to the cladding light filter, the cladding light filter is connected to the fiber end cap, and the core and cladding diameters of the cladding light filter are greater than or equal to the core and cladding diameters of the signal output fiber of the bleaching light circulator.

[0011] Preferably, the bleaching light circulator can be composed of a reverse pump signal combiner, the core / cladding diameter of the signal input fiber of the reverse pump signal combiner matches the core / cladding diameter of the gain fiber, the number n of pump energy transmission fibers of the reverse pump signal combiner satisfies 2≤n≤36, and n is an even number, and the pump energy transmission fibers are fused in pairs to form a plurality of pump energy transmission fiber closed loops.

[0012] As another preferred embodiment, the present invention also includes a reverse pump signal combiner, the signal output optical fiber of the bleaching light circulator is connected to the reverse pump signal combiner, the reverse pump signal combiner has a signal input optical fiber, a signal output optical fiber and at least one pump energy transmission optical fiber, the signal input optical fiber of the reverse pump signal combiner is connected to the signal output optical fiber of the bleaching light circulator, the signal output optical fiber of the reverse pump signal combiner is connected to the cladding light filter, each pump energy transmission optical fiber of the reverse pump signal combiner is connected to a fiber-coupled semiconductor laser, the signal output optical fiber of the reverse pump signal combiner is connected to the cladding light filter, the cladding light filter is connected to the optical fiber end cap, and the core and cladding diameters of the cladding light filter are greater than or equal to the core and cladding diameters of the signal output optical fiber of the reverse pump signal combiner.

[0013] Preferably, the gain fiber of the present invention is a step-index fiber doped with rare earth ions, and the rare earth ions are one or more of ytterbium ions, erbium ions, neodymium ions, thulium ions, and holmium ions; the cross-sectional structure of the gain fiber is one of single cladding, double cladding, triple cladding, or a prefabricated specific stacked structure.

[0014] Preferably, the wavelength range of the bleaching laser generated by the bleaching light source of the present invention is between 360nm and 780nm, and the output power is between 1mW and 10W; the bleaching laser generated by the bleaching light source is a single wavelength laser, a dual wavelength laser or a combination of multiple wavelengths.

[0015] Preferably, the fiber-coupled semiconductor laser of the present invention is an excitation source for the gain fiber to generate upper energy level particles, and its output wavelength matches the absorption peak of the rare earth ions doped in the gain fiber. The output wavelength of the fiber-coupled semiconductor laser is one or more combinations of 808nm, 915nm, 940nm, and 976nm.

[0016] Preferably, the output mode of the seed laser of the present invention is optical fiber output, the core diameter range of the output optical fiber is 5 μm to 50 μm, and the wavelength range of the signal laser generated by the seed laser is 950 nm to 1200 nm.

[0017] The above-mentioned all-fiber amplifier with improved anti-photon darkening performance can be used in a γ-ray, X-ray or ultraviolet radiation environment or a photon darkening environment, and can realize online bleaching in a γ-ray, X-ray or ultraviolet radiation environment or realize offline bleaching after working in a γ-ray, X-ray or ultraviolet radiation environment.

[0018] Compared with the prior art, the technical effects that the present invention can produce are:

[0019] The present invention injects the bleaching light generated by the bleaching light source into the gain fiber in the amplifier to bleach the gain fiber. Since a bleaching light circulator is connected behind the gain fiber, and the bleaching light circulator has a pump energy transmission fiber closed loop, the bleaching laser output by the amplifier that is not completely absorbed can circulate back and forth into the gain fiber in the amplifier to achieve cyclic bleaching of the gain fiber, which can not only effectively improve the light bleaching efficiency, but also enhance the energy density of the bleaching light in the gain fiber cladding, significantly improving the anti-darkening performance and working life of the optical fiber amplifier in a high radiation environment. The method of the present invention can effectively improve the bleaching efficiency of the all-fiber amplifier and greatly improve the anti-darkening performance of the amplifier.

[0020] The laser in the present invention is an all-fiber structure, and the bleaching light source can achieve both online bleaching effects and offline time-sharing bleaching. It has a simple structure and is easy to operate, and can greatly expand the application of fiber lasers in different radiation environments and photodarkening environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 This is a schematic diagram of the structure of an all-fiber amplifier with improved anti-photon darkening performance provided by Example 1 of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of a bidirectionally pumped all-fiber amplifier with improved anti-photon darkening performance provided by Example 2 of the present invention;

[0024] Figure 3 is a schematic structural diagram of a bleaching light circulator provided by an embodiment of the present invention;

[0025] Figure 4 is a schematic structural diagram of a bleaching light circulator provided by an embodiment of the present invention;

[0026] Figure annotation:

[0027] 1. Gain fiber; 2. Forward pump signal combiner; 3. Pump energy transmission fiber; 4. Fiber-coupled semiconductor laser; 5. Wavelength division multiplexer; 6. Wavelength division multiplexer energy transmission fiber; 7. Bleaching light source; 8. Seed laser; 9. Bleaching light circulator; 10. Signal input fiber; 11. Fiber beam combining end; 12. Pump energy transmission fiber closed loop; 13. Pump energy transmission fiber fusion point; 14. Signal output fiber; 15. Cladding light filter; 16. Fiber end cap; 17. Reverse pump signal combiner;

[0028] 12-1, first pump energy transmission fiber; 12-2, second pump energy transmission fiber; 12-3, third pump energy transmission fiber; 12-4, fourth pump energy transmission fiber; 12-5, fifth pump energy transmission fiber; 12-6, sixth pump energy transmission fiber; 13-1, fusion point of first pump energy transmission fiber; 13-2, fusion point of second pump energy transmission fiber; 13-3, fusion point of third pump energy transmission fiber. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the 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.

[0030] The principle of the all-fiber amplifier with improved anti-photon darkening performance conceived by the present invention is: by introducing a bleaching light circulator behind the gain fiber in the all-fiber amplifier, the bleaching laser injected into the gain fiber cladding of the amplifier passes through the pump energy transfer fiber closed loop of the bleaching light circulator and returns to the gain fiber cladding of the amplifier, thereby achieving cyclic reciprocating bleaching of the gain fiber, increasing the power density of the bleaching laser in the gain fiber cladding, and thus improving the photon darkening bleaching effect.

[0031] Reference Figure 1 , is a schematic diagram of the structure of an all-fiber amplifier with improved anti-photon darkening performance provided in Example 1 of the present invention, including a seed laser 8, a bleaching light source 7, a wavelength division multiplexer 5, a forward pump signal combiner 2, a gain fiber 1, a fiber-coupled semiconductor laser 4, a bleaching light circulator 9, a cladding light filter 15, and a fiber end cap 16.

[0032] The seed laser 8 and the bleaching light source 7 are connected to the wavelength division multiplexer 5, and the wavelength division multiplexer energy transmission fiber 6 is connected to the signal input fiber of the forward pump signal combiner 2. The signal laser output by the seed laser 8 and the bleaching laser output by the bleaching light source 7 are coupled into the amplifier through the wavelength division multiplexer energy transmission fiber 6, and the bleaching laser is used to bleach the photon darkening and radiation darkening of the gain fiber.

[0033] One end of the gain fiber 1 of the amplifier is connected to the signal output fiber of the forward pump signal combiner 2 , and the other end is connected to the signal input fiber of the bleaching light circulator 9 .

[0034] The bleaching light circulator 9 includes a fiber bundle end 11, a signal fiber and at least one pair of pump energy transmission fibers, the signal fiber includes a signal input fiber 10 and a signal output fiber 14, the two pairs of pump energy transmission fibers are fused in pairs to form a pump energy transmission fiber closed loop 12, and the pump energy transmission fibers are fused in pairs to form a pump energy transmission fiber fusion point 13, the gain fiber 1 is connected to the signal input fiber 10 of the bleaching light circulator 9, the signal laser output through the core of the gain fiber 1 is output through the signal input fiber 10 and the signal output fiber 14 of the bleaching light circulator 9, and the laser output through the cladding of the gain fiber 1 re-enters the gain fiber 1 through the pump energy transmission fiber closed loop 12 of the bleaching light circulator 9.

[0035] The signal output fiber 14 of the bleaching light circulator 9 is connected to the cladding light filter 15, and the cladding light filter 15 is connected to the fiber end cap 16. After the laser output by the gain fiber 1 is filtered by the cladding light filter 15 to remove the residual pump light and other component lights, it is expanded and output through the fiber end cap 16. The core and cladding diameters of the cladding light filter 15 are greater than or equal to the core and cladding diameters of the signal output fiber 14 of the bleaching light circulator 9.

[0036] The bleaching laser generated by the bleaching light source 7 is coupled into the forward pump signal combiner 2 through the wavelength division multiplexer energy transmission fiber 6, and then injected into the cladding of the amplifier's gain fiber 1 through the signal output fiber of the forward pump signal combiner 2, so as to bleach the photon darkening and radiation darkening of the gain fiber. The incompletely absorbed bleaching laser re-enters the amplifier's gain fiber cladding through the pump energy transmission fiber closed loop 12 of the bleaching light circulator 9, thereby forming a cyclic bleaching effect.

[0037] The bleaching light circulator 9 can be composed of a reverse pump signal combiner, the signal input fiber 10 of the reverse pump signal combiner is connected to one end of the gain fiber 1, and the core / cladding diameter of the signal input fiber 10 matches the core / cladding diameter of the gain fiber 1. The number n of pump energy transmission fibers of the reverse pump signal combiner satisfies 2≤n≤36, and n is an even number, and the pump energy transmission fibers are fused in pairs to form a plurality of pump energy transmission fiber closed loops.

[0038] The output mode of the seed laser 8 is optical fiber output, and the core diameter range of the output optical fiber is 5μm to 50μm; the signal laser wavelength range generated by the seed laser 8 is 950nm to 1200nm, and preferably a 1080nm laser with a core diameter of 10μm realizes single-mode output.

[0039] The bleaching laser wavelength range of the bleaching light source 7 is between 360nm and 780nm, and the output power is between 1mW and 10W, including single-wavelength laser, dual-wavelength laser or a combination of multiple wavelengths, which is used to perform photo-darkening bleaching on the gain fiber. Preferably, the bleaching light source 7 adopts a 450nm blue light laser with an output power of 100mW.

[0040] The bleaching laser generated by the bleaching light source 7 is transmitted in the cladding, and its transmission path is: bleaching laser generated by the bleaching light source 7 → wavelength division multiplexer 5 → forward pump signal combiner 2 → gain fiber 1 → bleaching light circulator 9 → pump energy transmission fiber closed loop 12 in the bleaching light circulator 9 → bleaching light circulator 9 → gain fiber 1 → forward pump signal combiner 2.

[0041] The signal laser generated by the seed laser 8 is transmitted in the fiber core, and its transmission path is: signal laser generated by the seed laser 8 → wavelength division multiplexer 5 → forward pump signal combiner 2 → gain fiber 1 → bleaching light circulator 9 → signal output fiber 14 of bleaching light circulator 9 → cladding light filter 15 → fiber end cap 16.

[0042] Reference Figure 2 , is a schematic diagram of the structure of an all-fiber amplifier with improved anti-photon darkening performance provided by Example 2 of the present invention. The all-fiber amplifier of Example 2 is a bidirectional pumping structure. Figure 2 The schematic diagram of the embodiment shown in FIG. Figure 1 The optical path structures of the embodiments shown are basically the same, including a seed laser 8, a bleaching light source 7, a wavelength division multiplexer 5, a forward pump signal combiner 2, a gain fiber 1, a fiber-coupled semiconductor laser 4, a bleaching light circulator 9, a cladding light filter 15, a fiber end cap 16, and a reverse pump signal combiner 17.

[0043] Figure 2 The embodiment shown and Figure 1The difference of the illustrated embodiment is that: the signal output fiber 14 of the bleaching light circulator 9 is connected to the reverse pumping signal combiner 17, the reverse pumping signal combiner 17 has a signal input fiber, a signal output fiber and at least one pumping energy transmission fiber 3, the signal input fiber of the reverse pumping signal combiner 17 is connected to the signal output fiber 14 of the bleaching light circulator 9, each pumping energy transmission fiber 3 of the reverse pumping signal combiner 17 is connected to a fiber-coupled semiconductor laser 4, the signal output fiber of the reverse pumping signal combiner 17 is connected to the cladding light filter 15, the cladding light filter 15 is connected to the fiber end cap 16, and the core and cladding diameters of the cladding light filter 15 are greater than or equal to the core and cladding diameters of the signal output fiber of the reverse pumping signal combiner 17.

[0044] Increasing the reverse pump signal combiner 17 to inject reverse pump power can further improve the output power of the all-fiber amplifier. In order to allow the pump power injected by the fiber-coupled semiconductor laser 4 connected to the reverse pump signal combiner 17 to smoothly pass through the bleaching light circulator 9 and enter the amplifier gain fiber, the size of the signal input fiber 10 of the bleaching light circulator 9 is kept consistent with the size of the signal output fiber 14.

[0045] The bleaching light circulator 9 can be a side pump signal combiner, including a fiber combining end 11, a signal input fiber 10, a signal output fiber 14 and at least one pump power transmission fiber closed loop 12. A pump power transmission fiber closed loop 12 is formed by fusion splicing two pump power transmission fibers, wherein the pump power transmission fibers are fused to form a pump power transmission fiber fusion point 13. The two ends of the pump power transmission fiber closed loop 12 are thinned and attached to the cladding of the signal fiber to form a fiber combining end 11. The signal input fiber 10 and the signal output fiber 14 of the bleaching light circulator 9 are the same fiber, and there is no need to melt and taper.

[0046] In any of the above embodiments:

[0047] The gain fiber 1 is a step-refractive-index fiber doped with rare earth ions, wherein the doped rare earth ions are one or more of ytterbium ions, erbium ions, neodymium ions, thulium ions, and holmium ions; the cross-sectional structure of the gain fiber 1 is one of single cladding, double cladding, triple cladding, or a prefabricated specific stacked structure.

[0048] The forward pump signal combiner 2 has a signal input fiber, a signal output fiber and at least one pump energy transmission fiber 3 ; the at least one pump energy transmission fiber 3 of the forward pump signal combiner 2 is connected to a fiber-coupled semiconductor laser 4 .

[0049] The fiber-coupled semiconductor laser 4 is the excitation source for the gain fiber 1 to generate upper-level particles, and its output wavelength matches the absorption peak of the rare earth ions doped in the gain fiber 1, which can be one or more combinations of 808nm, 915nm, 940nm, and 976nm.

[0050] The present invention is applicable to various radiation environments, including radiation environments such as gamma rays, X-rays, ultraviolet rays, and photon darkening environments. The present invention can realize both online bleaching and offline bleaching. Online bleaching means that in a radiation environment such as gamma rays, X-rays, ultraviolet rays, or a photon darkening environment, the all-fiber amplifier synchronously turns on a bleaching light source during operation, and the bleaching light source bleaches the irradiated gain fiber online during the operation of the all-fiber amplifier. Offline bleaching means that the all-fiber amplifier working in a radiation environment such as gamma rays, X-rays, ultraviolet rays, or a photon darkening environment will cause an increase in loss, thereby reducing the output power and service life of the all-fiber amplifier. For the all-fiber amplifier working in a radiation environment such as gamma rays, X-rays, ultraviolet rays, or a photon darkening environment, the scheme proposed by the present invention is used to turn on the bleaching light source 7 in a radiation-free environment, and use the bleaching light source 7 to inject a bleaching laser into the cladding of the gain fiber 1 of the amplifier, and the bleaching laser bleaches the gain fiber 1. After bleaching, the output performance of the all-fiber amplifier is restored to the state before radiation or darkening, and it is repeatedly used and bleached.

[0051] Reference Figure 3, is a schematic diagram of the structure of a bleaching light circulator provided in one embodiment of the present invention, specifically a bleaching light circulator composed of a (6+1)ⅹ1 reverse pump signal combiner. The bleaching light circulator 9 has a fiber bundle end 11, a signal input fiber 10, a signal output fiber 14 and three pump energy transmission fiber closed loops 12, the three pump energy transmission fiber closed loops 12 include six pump energy transmission fibers, specifically a first pump energy transmission fiber 12-1, a second pump energy transmission fiber 12-2, a third pump energy transmission fiber 12-3, a fourth pump energy transmission fiber 12-4, a fifth pump energy transmission fiber 12-5 and a sixth pump energy transmission fiber 12-6, wherein the first pump energy transmission fiber 12-1 and the sixth pump energy transmission fiber 12-6 are fused to form a first pump energy transmission fiber fusion point 13-1, the second pump energy transmission fiber 12-2 and the fifth pump energy transmission fiber 12-5 are fused to form a second pump energy transmission fiber fusion point 13-2, and the third pump energy transmission fiber 12-3 and the fourth pump energy transmission fiber 12-4 are fused to form a third pump energy transmission fiber fusion point 13-3. Specifically, the signal input fiber sizes of the reverse pump signal combiner include the common 20 / 400μm, 25 / 400μm, 30 / 400μm, 30 / 600μm, etc., the signal output fiber sizes include 20 / 250μm, 25 / 250μm, 30 / 250μm, 42 / 250μm, etc., and the pump energy transmission fiber sizes include 105 / 125μm, 135 / 155μm, 220 / 242μm, etc.

[0052] Reference Figure 4 , is a schematic diagram of the structure of a bleaching light circulator provided in one embodiment of the present invention, specifically a bleaching light circulator composed of a (2+1)ⅹ1 side pump signal combiner. The bleaching light circulator 9 has a fiber combining end 11, a signal input fiber 10, a signal output fiber 14 and a pump energy transmission fiber closed loop 12. The pump energy transmission fiber closed loop 12 includes two pump energy transmission fibers, a first pump energy transmission fiber 12-1 and a second pump energy transmission fiber 12-2, and the first pump energy transmission fiber 12-1 and the second pump energy transmission fiber 12-2 are fused to form a first pump energy transmission fiber fusion point 13-1. The signal input fiber 10 and the signal output fiber 14 of the side pump signal combiner are the same fiber, and their core / cladding sizes are consistent, which can be applied to backward pumping and bidirectional pumping fiber lasers to achieve reverse pump power injection. Specifically, the signal input fiber sizes of the side-pumped signal combiner include the common 20 / 400μm, 25 / 400μm, 30 / 400μm, etc., the signal output fiber sizes include 20 / 400μm, 25 / 400μm, 30 / 400μm, etc., and the pump energy transmission fiber sizes include 105 / 125μm, 135 / 155μm, 220 / 242μm, etc.

[0053] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0054] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An all-fiber amplifier with improved anti-photon darkening performance, characterized in that: It includes a seed laser, a bleaching light source, a wavelength division multiplexer, a forward pump signal combiner, a gain fiber, a fiber-coupled semiconductor laser, and a bleaching light circulator; the forward pump signal combiner has a signal input fiber, a signal output fiber and at least one pump energy transmission fiber; The seed laser and the bleaching light source are connected to a wavelength division multiplexer, the wavelength division multiplexer energy transmission fiber is connected to the signal input fiber of the forward pump signal combiner, and each pump energy transmission fiber of the forward pump signal combiner is connected to a fiber-coupled semiconductor laser; one end of the gain fiber is connected to the signal output fiber of the forward pump signal combiner, and the other end is connected to the signal input fiber of the bleaching light circulator, the bleaching laser output by the bleaching light source and the pump light output by multiple fiber-coupled semiconductor lasers are transmitted in the cladding of the gain fiber, and the signal laser output by the seed laser is transmitted in the core of the gain fiber; The bleaching light circulator has a pump energy transmission fiber closed loop. The incompletely absorbed bleaching laser output to the bleaching light circulator through the fiber cladding of the gain fiber re-enters the gain fiber through the pump energy transmission fiber closed loop in the bleaching light circulator, thereby realizing cyclic bleaching of the gain fiber. The signal laser output through the core of the gain fiber is output through the signal output fiber of the bleaching light circulator.

2. The all-fiber amplifier with improved anti-photon darkening performance according to claim 1, characterized in that: The bleaching light circulator comprises an optical fiber bundle combining end, a signal optical fiber and at least one pair of pump energy transmission optical fibers, wherein the signal optical fiber comprises a signal input optical fiber and a signal output optical fiber, and the two paired pump energy transmission optical fibers are fused in pairs to form a pump energy transmission optical fiber closed loop, and the pump energy transmission optical fiber fusion point is formed at the place where the pump energy transmission optical fibers are fused in pairs, and the gain optical fiber is connected to the signal input optical fiber of the bleaching light circulator, and the signal laser output through the core of the gain optical fiber is output through the signal input optical fiber and the signal output optical fiber of the bleaching light circulator, and the laser output through the cladding of the gain optical fiber re-enters the gain optical fiber through the pump energy transmission optical fiber closed loop of the bleaching light circulator.

3. The all-fiber amplifier with improved anti-photon darkening performance according to claim 1, characterized in that: It also includes a cladding light filter and an optical fiber end cap. The signal output optical fiber of the bleaching light circulator is connected to the cladding light filter, and the cladding light filter is connected to the optical fiber end cap. The core and cladding diameters of the cladding light filter are greater than or equal to the core and cladding diameters of the signal output optical fiber of the bleaching light circulator.

4. The all-fiber amplifier with improved anti-photon darkening performance according to claim 2, characterized in that: The bleaching light circulator is composed of a reverse pump signal combiner, the core / cladding diameter of the signal input fiber of the reverse pump signal combiner matches the core / cladding diameter of the gain fiber, the number n of the pump energy transmission fibers of the reverse pump signal combiner satisfies 2≤n≤36, and n is an even number, and the pump energy transmission fibers are fused in pairs to form a plurality of pump energy transmission fiber closed loops.

5. The all-fiber amplifier with improved anti-photon darkening performance according to claim 1, characterized in that: The invention comprises a reverse pump signal combiner, the signal output optical fiber of the bleaching light circulator is connected to the reverse pump signal combiner, the reverse pump signal combiner has a signal input optical fiber, a signal output optical fiber and at least one pump energy transmission optical fiber, the signal input optical fiber of the reverse pump signal combiner is connected to the signal output optical fiber of the bleaching light circulator, each pump energy transmission optical fiber of the reverse pump signal combiner is connected to a fiber-coupled semiconductor laser, the signal output optical fiber of the reverse pump signal combiner is connected to a cladding light filter, the cladding light filter is connected to an optical fiber end cap, and the core and cladding diameters of the cladding light filter are greater than or equal to the core and cladding diameters of the signal output optical fiber of the reverse pump signal combiner.

6. The all-fiber amplifier with improved anti-photon darkening performance according to any one of claims 1 to 5, characterized in that: The gain fiber is a step-refractive-index fiber doped with rare earth ions, wherein the doped rare earth ions are one or more of ytterbium ions, erbium ions, neodymium ions, thulium ions, and holmium ions; the cross-sectional structure of the gain fiber is one of single cladding, double cladding, triple cladding, or a prefabricated specific stacked structure.

7. The all-fiber amplifier with improved anti-photon darkening performance according to any one of claims 1 to 5, characterized in that: The wavelength range of the bleaching laser generated by the bleaching light source is between 360nm and 780nm, and the output power is between 1mW and 10W; the bleaching laser generated by the bleaching light source is single-wavelength laser, dual-wavelength laser or a combination of multiple wavelengths.

8. The all-fiber amplifier with improved anti-photon darkening performance according to any one of claims 1 to 5, characterized in that: The fiber-coupled semiconductor laser is an excitation source for the gain fiber to generate upper energy level particles, and its output wavelength matches the absorption peak of the rare earth ions doped in the gain fiber. The output wavelength of the fiber-coupled semiconductor laser is one or more combinations of 808nm, 915nm, 940nm, and 976nm.

9. The all-fiber amplifier with improved anti-photon darkening performance according to claim 1 or 2 or 3 or 4 or 5 or 7 or 8, characterized in that: The output mode of the seed laser is optical fiber output, the core diameter range of the output optical fiber is 5 μm to 50 μm, and the wavelength range of the signal laser generated by the seed laser is 950 nm to 1200 nm.

10. The all-fiber amplifier with improved anti-photodarkening performance as claimed in claim 1 can be used in a γ-ray, X-ray or ultraviolet radiation environment or a photodarkening environment, and can achieve online bleaching in a γ-ray, X-ray or ultraviolet radiation environment or offline bleaching after working in a γ-ray, X-ray or ultraviolet radiation environment.

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