A cascade-pumped fiber laser based on a double-ended output oscillator

Abstract

The invention discloses a cascade pumped fiber laser based on a double-ended output oscillator, comprising a laser resonant cavity, a forward pump signal combiner, a backward pump signal combiner, a cladding light filter, an optical fiber end cap and at least two double-ended output laser oscillators; the forward pump signal combiner comprises a first signal input arm, a first pump signal output arm and a plurality of first pump injection arms; the backward pump signal combiner comprises a second signal input arm, a second pump signal output arm and a plurality of second pump injection arms; the forward output optical fiber of each double-ended output laser oscillator is connected to the corresponding first pump injection arm, and the backward output optical fiber is connected to the corresponding second pump injection arm; the first signal input arm is fused with the energy transmission optical fiber; the first pump signal output arm is connected to one end of the laser resonant cavity; and the other end of the laser resonant cavity is connected to the second signal input arm. The invention improves the utilization efficiency of pump light and the overall electro-optical efficiency of the laser.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber lasers and relates to a cascade pumped optical fiber laser based on a double-end output oscillator. Background Art

[0002] Compared with the main oscillator power amplifier structure fiber laser, the all-fiber laser oscillator has the advantages of low cost, compact structure, simple control logic, stable performance, and strong anti-reflection and return ability. It is widely used in industrial processing.

[0003] With the expansion of application fields, the power demand for fiber laser oscillators is getting higher and higher. Double-ended pumped fiber lasers can inject higher pump powers, which helps to improve the overall power of fiber lasers. However, in general double-ended pumped lasers, the pump source generally uses a fiber-coupled semiconductor laser as a pump source (i.e., LD directly pumped fiber lasers), or a single-ended output short-wavelength fiber laser as a pump source (i.e., cascade pumped fiber lasers). In these two types of pumping lasers, each pump arm needs to be connected to a pump source, which increases the number of pump sources, the system cost, and the size.

[0004] In addition, in a double-ended pumped laser, if the forward pump light is not completely absorbed by the gain fiber, the residual pump light will be transmitted to the backward pump signal combiner and output from the pump arm of the backward combiner; conversely, if the backward pump light is not completely absorbed by the gain fiber, the residual pump light will be transmitted to the backward pump signal combiner and output from the pump arm of the forward combiner. General double-ended pumped fiber lasers use fiber-coupled semiconductor lasers or single-ended short-wavelength fiber lasers. The residual pump light output from the backward or forward combiner will be injected into the fiber-coupled semiconductor laser or short-wavelength laser, but it cannot be reused to be injected into the main laser, resulting in low overall laser efficiency. Summary of the invention

[0005] The object of the present invention is to provide a cascade pumped fiber laser based on a double-ended output oscillator, which can improve the utilization efficiency of pump light and ensure the overall electro-optical efficiency of the laser.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A cascade pumped fiber laser based on a double-ended output oscillator, the cascade pumped fiber laser comprising a laser resonant cavity, a forward pump signal combiner 5, a backward pump signal combiner 6, a cladding light filter 7, a fiber end cap 8 and at least two double-ended output laser oscillators 4;

[0008] The forward pump signal combiner 5 includes a first signal input arm 5-1, a first pump signal output arm 5-3 and a plurality of first pump injection arms 5-2; the backward pump signal combiner 6 includes a second signal input arm 6-1, a second pump signal output arm 6-3 and a plurality of second pump injection arms 6-2;

[0009] The forward output optical fiber 4-10 of each double-ended output laser oscillator 4 is connected to the corresponding first pump injection arm 5-2; the backward output optical fiber 4-9 of each double-ended output laser oscillator 4 is connected to the corresponding second pump injection arm 6-2;

[0010] The first signal input arm 5-1 is fused with the energy transmission optical fiber; the first pump signal output arm 5-3 is connected to one end of the laser resonant cavity; the other end of the laser resonant cavity is connected to the second signal input arm 6-1; the second signal output arm 6-3, the cladding light filter 7 and the optical fiber end cap 8 are connected in sequence.

[0011] Further, the laser resonant cavity includes a high-reflection fiber Bragg grating 2, a gain fiber 1 and a low-reflection fiber Bragg grating 3;

[0012] The forward pump signal combiner 5, the high reflection fiber Bragg grating 2, the gain fiber 1, the low reflection fiber Bragg grating 3 and the backward pump signal combiner 6 are connected in sequence through the energy transmission fiber.

[0013] Further, the laser resonant cavity includes a high-reflection fiber Bragg grating 2, a gain fiber 1 and a low-reflection fiber Bragg grating 3;

[0014] The high-reflection fiber Bragg grating 2, the forward pump signal combiner 5, the gain fiber 1, the backward pump signal combiner 6 and the low-reflection fiber Bragg grating 3 are connected in sequence.

[0015] Furthermore, the central wavelengths of the high-reflection fiber Bragg grating 2 and the low-reflection fiber Bragg grating 3 match.

[0016] Furthermore, the working wavelength of the gain fiber 1, the high-reflection fiber grating 2 and the low-reflection fiber grating 3 in the ytterbium-doped fiber laser is 1050-1150 nm.

[0017] Furthermore, the gain optical fiber 1 comprises a core; the core is wrapped with a layer of non-doped silica-based glass;

[0018] The fiber core is a fiber core doped with rare earth activated particles, and is used to generate and transmit signal laser under the stimulation of pump light; the diameter of the fiber core is 6 to 200 μm, and the numerical aperture is 0.06 to 0.12 NA;

[0019] The quartz-based glass layer is used for transmitting pump laser; the diameter of the quartz-based glass layer is 125-1000 μm, and the numerical aperture is 0.12-0.46 NA.

[0020] Furthermore, the core cladding geometric dimensions of the gain optical fiber 1, the high-reflection optical fiber Bragg grating 2 and the low-reflection optical fiber Bragg grating 3 are all the same.

[0021] Furthermore, the wavelength of the double-ended output laser oscillator 4 in the ytterbium-doped fiber laser is 1000nm to 1040nm; the diameter of the forward output fiber 4-10 and the backward output fiber (4-9) of the double-ended output laser oscillator 4 is 6 to 200μm, and the numerical aperture is 0.06 to 0.46NA.

[0022] Furthermore, a first tilted grating is provided between each forward output optical fiber 4-10 and the corresponding first pump injection arm 5-2; and a second tilted grating is provided between each backward output optical fiber 4-9 and the corresponding second pump injection arm 6-2.

[0023] Beneficial effects of the present invention:

[0024] 1. The present invention uses short-wavelength pump light output by a double-end output laser oscillator to pump a long-wavelength laser. The laser output forward by the double-end output laser oscillator is injected into the forward pump signal combiner as the forward pump light of the long-wavelength laser. The forward pump signal combiner combines the forward pump light and injects it into the gain fiber. The gain fiber absorbs most of the forward pump light to generate laser. The residual forward pump light that is not completely absorbed by the gain fiber can pass through the low-reflection fiber grating and the backward pump signal combiner in sequence, and then be injected into the double-end output laser oscillator. After passing through the double-end output laser oscillator, it can be injected into the forward pump signal combiner again and absorbed by the gain fiber. Similarly, the double-end output laser oscillator outputs the laser beam backward. The laser is injected into the backward pump signal combiner as the backward pump light of the long wavelength laser. The backward pump signal combiner combines the backward pump light and injects it into the gain fiber. The gain fiber absorbs most of the backward pump light to generate laser. The residual backward pump light that is not completely absorbed by the gain fiber passes through the high-reflection fiber grating and the forward pump signal combiner in sequence, and is injected into the double-end output laser oscillator, and can be injected into the backward pump signal combiner again. In this way, the residual pump light that cannot be used in traditional lasers can be reused, thereby improving the utilization efficiency of the pump light and the overall electro-optical efficiency of the laser.

[0025] 2. The present invention uses short-wavelength pump light output by a double-ended output laser oscillator to pump the long-wavelength laser, which can enable a short-wavelength laser to pump the long-wavelength laser in both the forward and backward directions at the same time; whereas in a conventional cascade-pumped fiber laser, two independent pump lasers must be used to achieve forward and backward pumping of the laser; therefore, the present invention can reduce the number of pump lasers in a conventional laser by half, thereby reducing the volume, weight and cost of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of the structure of a cascade-pumped fiber laser based on a double-ended output oscillator;

[0027] Figure 2 Another structural diagram of a cascade-pumped fiber laser based on a double-ended output oscillator;

[0028] Figure 3 The third structural diagram of the cascade-pumped fiber laser based on a double-ended output oscillator;

[0029] Figure 4 This is a schematic diagram of the fourth structure of the cascade-pumped fiber laser based on a double-ended output oscillator. DETAILED DESCRIPTION

[0030] The specific implementation modes of the present invention are described in detail below with reference to the accompanying drawings.

[0031] Embodiment 1:

[0032] This embodiment provides a cascade pumped fiber laser based on a double-ended output oscillator. Figure 1 The cascade pumped fiber laser comprises a laser resonant cavity, a forward pump signal combiner 5, a backward pump signal combiner 6, a cladding light filter 7, a fiber end cap 8 and at least two double-ended output laser oscillators 4. The forward pump signal combiner 5 and the backward pump signal combiner 6 in this embodiment can both transmit signal lasers in both directions.

[0033] The laser resonant cavity of this embodiment includes a high-reflection fiber Bragg grating 2, a gain fiber 1, and a low-reflection fiber Bragg grating 3 which are sequentially spliced ​​by fiber fusion. Among them, the working wavelength of the gain fiber 1, the high-reflection fiber Bragg grating 2, and the low-reflection fiber Bragg grating 3 in the ytterbium-doped fiber laser is 1050-1150nm. The gain fiber 1 is a double-clad or triple-clad structure. Among them, the core is doped with rare earth activated particles, which can generate and transmit signal lasers under the stimulation of pump light; the inner cladding is a non-doped quartz-based glass layer, which can transmit pump lasers; the core diameter of the gain fiber 1 is between 6 and 200μm, and the core numerical aperture is 0.06 to 0.12NA; the diameter of the quartz-based glass layer is between 125 and 1000μm, and the inner cladding numerical aperture is 0.12 to 0.46NA. The core cladding geometric dimensions of the gain fiber 1, the high-reflection fiber Bragg grating 2, and the low-reflection fiber Bragg grating 3 are the same. The reflectivity of the high-reflection fiber Bragg grating 2 is greater than 95%, and most of the reverse signal laser transmitted from the gain fiber 1 is reflected into the gain fiber 1. The reflectivity of the low-reflection fiber Bragg grating 3 is between 5% and 70%, and part of the signal laser transmitted from the gain fiber 1 is reflected into the gain fiber 1, and part of it is output through the low-reflection fiber Bragg grating 2.

[0034] The central wavelengths of the high-reflection fiber Bragg grating 2 and the low-reflection fiber Bragg grating 3 of this embodiment are matched, and the central wavelengths thereof are the central wavelengths of the laser output by the cascade pumped fiber laser.

[0035] In this embodiment, the forward pump signal combiner 5 includes a first signal input arm 5-1, a first pump signal output arm 5-3 and a plurality of first pump injection arms 5-2. The backward pump signal combiner 6 includes a second signal input arm 6-1, a second pump signal output arm 6-3 and a plurality of second pump injection arms 6-2. The forward output fiber 4-10 of each double-ended output laser oscillator 4 is connected to the corresponding first pump injection arm 5-2; the backward output fiber 4-9 of each double-ended output laser oscillator 4 is connected to the corresponding second pump injection arm 6-2; the first signal input arm 5-1 is fused with the energy transmission fiber; the first pump signal output arm 5-3, the high reflection fiber grating 2, the gain fiber 1, the low reflection fiber grating 3 and the second signal input arm 6-1 of the backward pump signal combiner 6 are connected in sequence through the pump signal energy transmission fiber; the second signal output arm 6-3 of the backward pump signal combiner 6, the cladding light filter 7 and the fiber end cap 8 are connected in sequence. The double-ended output laser oscillator 4 may adopt an existing double-ended output linear cavity all-fiber laser oscillator, and its structure will not be described in detail.

[0036] The double-ended output laser oscillator 4 of this embodiment is a high-brightness fiber laser with an output wavelength shorter than the working wavelength of the cascade pump fiber laser. For example, in an ytterbium-doped fiber laser, the wavelength of the double-ended output laser oscillator 4 is 1000nm-1040nm, which is shorter than the central wavelength of the high-reflection fiber grating 2, 1050-1150nm, to ensure that the short-wavelength laser (i.e., pump light) can be effectively absorbed by the gain fiber 1 and converted into a laser output with the same central wavelength as the high-reflection fiber grating 2; the diameters of the forward output fiber 4-10 and the backward output fiber 4-9 of the double-ended output laser oscillator 4 are both 6-200μm, and the numerical apertures are both 0.06-0.46NA. .

[0037] The geometric dimensions of the input optical fiber of the layer light filter 7 of this embodiment are consistent with the geometric dimensions of the pump signal energy transmission optical fiber to filter out the residual pump light and high-order mode laser in the optical fiber; the optical fiber end cap 8 is used for signal light beam expansion output to reduce the power density of the output end face and improve the reliability of the laser.

[0038] In order to prevent the parasitic oscillation of the laser caused by the feedback of light in other bands other than the laser band, the first signal input arm 5 - 1 in this embodiment is fused with the energy transmission optical fiber 9 at an angle of 8 degrees.

[0039] The working process of this embodiment is as follows: the forward pump light output from the front end of the double-ended output laser oscillator array 4 is sequentially combined by the forward pump signal combiner 5 and then injected into the gain fiber 1 in the laser resonant cavity, and the gain fiber 1 is pumped; the gain fiber 1 absorbs most of the forward pump light to generate laser, and the residual forward pump light not absorbed by the gain fiber 1 is sequentially injected into the double-ended output laser oscillator array 4 through the low-reflection fiber grating 3 and the second pump injection arm 6-2 of the backward pump signal combiner 6, and after passing through the double-ended output laser oscillator 4, it can be injected into the forward pump signal combiner 5 again and absorbed by the gain fiber; the double-ended output The backward pump light output from the rear end of the laser oscillator array 4 is sequentially combined by the backward pump signal combiner 6 and then injected into the gain fiber 1 in the laser resonant cavity to pump the gain fiber 1; the gain fiber 1 absorbs most of the backward pump light to generate laser, and the residual backward pump light not absorbed by the gain fiber 1 is sequentially injected into the double-end output laser oscillator array 4 through the high-reflection grating 2 and the first pump injection arm 5-2 of the forward pump signal combiner 5. After passing through the double-end output laser oscillator, it can be injected into the backward pump signal combiner again, thereby improving the utilization efficiency of the pump light, thereby improving the overall electro-optical efficiency of the laser.

[0040] The laser light generated by the pump light absorbed by the gain fiber 1 in the laser resonant cavity is transmitted from the left and right directions (or both ends) of the gain fiber. The laser light transmitted to the left is reflected by the high-reflection fiber grating 2 back to the gain fiber 1 and amplified; the laser light transmitted to the right is reflected by the low-reflection fiber grating 3 and then returned to the gain fiber 1 and amplified; the laser light in the laser resonant cavity is oscillated and generates a stable laser light after multiple reflections by the high-reflection fiber grating 2 and the low-reflection fiber grating 3 and multiple amplifications by the gain fiber 1; part of the laser light generated in the laser resonant cavity and transmitted to the right is output to the outside of the laser resonant cavity after being transmitted by the low-reflection fiber grating 3, and then output 6-3 through the second pump signal arm of the backward pump signal combiner 6, and then is filtered by the cladding light filter 7 in turn and then expanded and output through the fiber end cap 8.

[0041] Embodiment 2:

[0042] The structure of this embodiment is basically the same as that of the embodiment 1, except that the connection relationship between the laser resonant cavity and the forward pump signal combiner 5 and the backward pump signal combiner 6 is different, as follows:

[0043] Each forward output fiber 4-10 is connected to the corresponding first pump injection arm 5-2; each backward output fiber 4-9 is connected to the corresponding second pump injection arm 6-2; the first signal input arm 5-1 is connected to one end of the high-reflection fiber Bragg grating 2, and the other end of the high-reflection fiber Bragg grating 2 is fused with the energy transfer fiber 9 at an angle of 8 degrees, which can avoid the parasitic oscillation of the laser caused by other light feedback in the non-laser band. The first pump signal output arm 5-3 is connected to one end of the gain fiber 1 through the pump signal energy transfer fiber; the other end of the gain fiber 1 is connected to the second signal input arm 6-1 of the backward pump signal combiner 6 through the pump signal energy transfer fiber; the second signal output arm 6-3 of the backward pump signal combiner 6, the low-reflection fiber Bragg grating 3, the cladding light filter 7 and the fiber end cap 8 are connected in sequence, refer to Figure 2 .

[0044] The working process of this embodiment is as follows: the forward pump light output from the front end of the double-ended output laser oscillator array 4 is sequentially combined by the forward pump signal combiner 5 and then injected into the gain fiber 1 in the laser resonant cavity, and the gain fiber 1 is pumped; the gain fiber 1 absorbs most of the forward pump light to generate laser light, and the residual forward pump light not absorbed by the gain fiber 1 is injected into the double-ended output laser oscillator array 4 through the second pump injection arm 6-2 of the backward pump signal combiner 6, and after passing through the double-ended output laser oscillator 4, it can be injected into the forward pump signal combiner 5 again and absorbed by the gain fiber 1; the double-ended output laser oscillator The backward pump light output from the rear end of the array 4 is sequentially combined by the backward pump signal combiner 6 and then injected into the gain fiber 1 in the laser resonant cavity to pump the gain fiber 1; the gain fiber 1 absorbs most of the backward pump light to generate laser, and the residual backward pump light not absorbed by the gain fiber 1 is injected into the double-end output laser oscillator array 4 through the first pump injection arm 5-2 of the backward pump signal combiner 5. After passing through the double-end output laser oscillator 4, it can be injected into the backward pump signal combiner 6 again and absorbed by the gain fiber 1, thereby improving the utilization efficiency of the pump light and thus improving the overall electro-optical efficiency of the laser.

[0045] In the laser resonant cavity, the laser generated by the pump light absorbed by the gain fiber 1 is transmitted from the left and right directions of the gain fiber 1. The laser transmitted to the left passes through the first signal output arm 5-3 and the first signal input arm 5-1 of the forward pump signal combiner 5 in sequence, and is reflected by the high-reflection fiber grating 2 back to the gain fiber 1 and amplified; the laser transmitted to the right passes through the second signal input arm 6-2 and the second signal output arm 6-3 of the forward pump signal combiner 6 in sequence, and is reflected by the low-reflection fiber grating 3 back to the gain fiber 1 and amplified; The laser in the optical resonant cavity is reflected multiple times by the high-reflection fiber Bragg grating 2 and the low-reflection fiber Bragg grating 3 and amplified multiple times by the gain fiber 1, and automatically selects the laser that meets the central wavelength of the high-reflection fiber Bragg grating 2 and the low-reflection fiber Bragg grating 3 to start oscillation and generate stable laser; part of the laser generated in the resonant cavity and transmitted to the right is transmitted through the low-reflection fiber Bragg grating 3 and then output to the outside of the resonant cavity, and then passes through the second pump signal arm output 6-3 of the backward pump signal combiner 6, and then passes through the cladding light filter 7 for filtering and is output through the fiber end cap 8 for expansion.

[0046] Embodiment 3:

[0047] The structure of this embodiment is basically the same as that of embodiment 1, except that: a first tilted grating 10 is provided between each forward output optical fiber 4-10 and the corresponding first pump injection arm 5-2; a second tilted grating 11 is provided between each backward output optical fiber 4-9 and the corresponding second pump injection arm 6-2, Figure 3The first tilted grating 10 and the second tilted grating 11 both transmit the working wavelength (1000nm-1040nm) of the double-ended output laser oscillator 4 and reflect the working wavelength (1050-1150nm) of the cascade pumped fiber laser to avoid self-excitation of the double-ended output laser oscillator 4 due to long wavelength laser injection.

[0048] Embodiment 4:

[0049] The structure of this embodiment is basically the same as that of embodiment 2, except that: a first tilted grating 10 is provided between each forward output optical fiber 4-10 and the corresponding first pump injection arm 5-2; a second tilted grating 11 is provided between each backward output optical fiber 4-9 and the corresponding second pump injection arm 6-2, Figure 4 The first tilted grating 10 and the second tilted grating 11 both transmit the working wavelength (1000nm-1040nm) of the double-ended output laser oscillator 4 and reflect the working wavelength (1050-1150nm) of the cascade pumped fiber laser to avoid self-excitation of the double-ended output laser oscillator 4 due to long wavelength laser injection.

[0050] It is obvious to those skilled in the art that the embodiments of the present invention are not limited to the details of the above exemplary embodiments, and that the embodiments of the present invention can be implemented in other specific forms without departing from the spirit or basic features of the embodiments of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the embodiments of the present invention is limited by the attached claims rather than the above description, so it is intended to include all changes that fall within the meaning and scope of the equivalent elements of the claims in the embodiments of the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units, modules or devices stated in the system, device or terminal claims can also be implemented by the same unit, module or device through software or hardware. The words first, second, etc. are used to indicate names, and do not indicate any particular order.

[0051] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the embodiments of the present invention and are not intended to limit them. Although the embodiments of the present invention have been described in detail with reference to the above preferred implementation modes, those skilled in the art should understand that the technical solutions of the embodiments of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cascade-pumped fiber laser based on a double-ended output oscillator, characterized in that: The cascade pumped fiber laser comprises a laser resonant cavity, a forward pump signal combiner (5), a backward pump signal combiner (6), a cladding light filter (7), a fiber end cap (8) and at least two double-ended output laser oscillators (4); The forward pump signal combiner (5) comprises a first signal input arm (5-1), a first pump signal output arm (5-3) and a plurality of first pump injection arms (5-2); the backward pump signal combiner (6) comprises a second signal input arm (6-1), a second pump signal output arm (6-3) and a plurality of second pump injection arms (6-2); The forward output optical fiber (4-10) of each double-ended output laser oscillator (4) is connected to the corresponding first pump injection arm (5-2); the backward output optical fiber (4-9) of each double-ended output laser oscillator (4) is connected to the corresponding second pump injection arm (6-2); The first signal input arm (5-1) is fused with the energy transmission optical fiber; the first pump signal output arm (5-3) is connected to one end of the laser resonant cavity; the other end of the laser resonant cavity is connected to the second signal input arm (6-1); the second pump signal output arm (6-3), the cladding light filter (7) and the optical fiber end cap (8) are connected in sequence; The laser resonant cavity comprises a high-reflection fiber Bragg grating (2), a gain fiber (1) and a low-reflection fiber Bragg grating (3); the operating wavelength of the gain fiber (1), the high-reflection fiber Bragg grating (2) and the low-reflection fiber Bragg grating (3) in an ytterbium-doped fiber laser is 1050-1150 nm; The wavelength of the double-end output laser oscillator (4) in the ytterbium-doped fiber laser is 1000nm-1040nm; the diameter of the forward output fiber (4-10) and the backward output fiber (4-9) of the double-end output laser oscillator (4) is 6-200μm, and the numerical aperture is 0.06-0.46NA.

2. The cascade-pumped fiber laser according to claim 1, characterized in that: The forward pump signal combiner (5), the high reflection fiber Bragg grating (2), the gain fiber (1), the low reflection fiber Bragg grating (3) and the backward pump signal combiner (6) are connected in sequence via energy transmission optical fibers.

3. The cascade-pumped fiber laser according to claim 2, characterized in that: The high-reflection optical fiber Bragg grating (2), the forward pump signal beam combiner (5), the gain optical fiber (1), the backward pump signal beam combiner (6) and the low-reflection optical fiber Bragg grating (3) are connected in sequence.

4. The cascade-pumped fiber laser according to claim 2 or 3, characterized in that: The central wavelengths of the high-reflection optical fiber grating (2) and the low-reflection optical fiber grating (3) are matched.

5. The cascade-pumped fiber laser according to claim 4, characterized in that: The gain optical fiber (1) comprises a fiber core; the fiber core is wrapped with a layer of non-doped silica-based glass; The fiber core is a fiber core doped with rare earth activated particles, and is used to generate and transmit signal laser under the stimulation of pump light; the diameter of the fiber core is 6-200 μm, and the numerical aperture is 0.06-0.12 NA; The quartz-based glass layer is used to transmit pump laser; the diameter of the quartz-based glass layer is 125-1000 μm, and the numerical aperture is 0.12-0.46 NA.

6. The cascade-pumped fiber laser according to claim 5, characterized in that: The core cladding geometric dimensions of the gain optical fiber (1), the high-reflection optical fiber grating (2) and the low-reflection optical fiber grating (3) are all the same.

7. The cascade-pumped fiber laser according to any one of claims 1 to 6, characterized in that: A first tilted grating (10) is arranged between each forward output optical fiber (4-10) and the corresponding first pump injection arm (5-2); and a second tilted grating (11) is arranged between each backward output optical fiber (4-9) and the corresponding second pump injection arm (6-2).

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