All-fiber high-power narrow-linewidth laser long-distance transmission system and method

Abstract

The invention discloses an all-fiber high-power narrow-linewidth laser long-distance transmission system and method. The system comprises a narrow-linewidth laser, a pumping source, a pumping beam combiner, a gain fiber, a cladding light stripper, a coupling device, a double-core fiber and an output device. The laser outputs initial laser, the initial laser and pumping source light are injected into the gain optical fiber through the beam combiner to form high-power laser, the stripper removes residual pumping light, the coupling device guides the laser into the double-core optical fiber, the laser is periodically coupled between fiber cores to disperse power density and suppress stimulated Brillouin scattering, and finally the laser is shaped and output through the output device. System devices are connected through an optical fiber fusion splicer, a passive double-core optical fiber is replaced by an active double-core optical fiber and can be applied to an optical fiber amplifier, and long-distance stable transmission is achieved.

Description

Technical Field

[0001] This invention relates to the field of high-power fiber lasers, specifically to an all-fiber high-power narrow-linewidth laser long-distance transmission system and method. Background Technology

[0002] All-fiber high-power narrow-linewidth lasers possess advantages such as good beam quality, high electro-optic conversion efficiency, compact structure, and high stability, making them invaluable in industrial processing, military defense, and biomedical fields. To improve the ease of use and environmental adaptability of all-fiber high-power narrow-linewidth lasers, a certain length of transmission fiber is typically added to the end of the gain fiber in the main amplification stage. However, adding transmission fiber significantly reduces the nonlinear threshold of the fiber laser. Among these nonlinear phenomena, stimulated Brillouin scattering has the lowest threshold and is the first phenomenon to appear in all-fiber high-power narrow-linewidth lasers.

[0003] Stimulated Brillouin scattering (SBS) is a nonlinear effect produced by the combined action of signal light, Stokes light, and sound waves, exhibiting a distinct threshold characteristic. When this threshold is exceeded, a significant amount of signal light energy is transferred to the backward Stokes light, posing a serious threat to the system's safety and stable operation. The threshold formula for stimulated Brillouin scattering is as follows: ; Wherein, K is used to characterize the influence of the polarization state of the signal light. For the area of ​​the model field, The peak value of the Brillouin gain. For effective fiber length, For the signal beam width, The full width at half maximum (FWHM) of the Brillouin gain spectrum.

[0004] As shown in the threshold formula, given a fixed signal light, the stimulated Brillouin scattering threshold can be increased by increasing the mode area, decreasing the effective fiber length, and reducing the Brillouin gain peak value. Currently, the diameter of large-mode-area double-clad fibers has reached over 30 μm. Larger diameters lead to an increase in the number of modes the fiber can support, which can easily cause beam quality degradation. Reducing the effective fiber length limits the convenience and applicability of narrow-linewidth fiber lasers; therefore, the application of these two methods in further power enhancement is relatively limited. The expression for the Brillouin gain peak value is as follows: ; Based on current technology, reducing the Brillouin gain peak primarily involves lowering the acousto-optic overlap factor (fA). The acousto-optic overlap factor (fA) is determined by the overlap integral of the optical and acoustic fields in the fiber. Therefore, for ordinary double-clad fibers, reducing fA requires redesigning the fiber structure and material composition to alter the acoustic performance as needed while maintaining the optical properties—a highly complex process. Besides ordinary double-clad fibers, hollow-core fibers can also reduce fA by changing the transmission medium of the signal light. However, hollow-core fibers have poor compatibility with widely used double-clad fibers in terms of splicing, mode field, and NA, thus losing the advantages of all-fiber high-power lasers.

[0005] Therefore, there is an urgent need for a high-power, narrow-linewidth laser long-distance transmission scheme that combines the characteristics of all-fiber technology, a high nonlinear threshold, and ease of implementation. Summary of the Invention

[0006] The main objective of this invention is to provide an all-fiber high-power narrow-linewidth laser long-distance transmission system and method. Through the technical means of "high-power pure laser generation (narrow-linewidth laser + pump combiner + gain fiber + cladding stripper), multi-core fiber power dispersion transmission (periodic coupling of dual-core and multi-core fibers to disperse power density), and all-fiber stable connection and secure output (fiber fusion splicing + fiber end caps)," combined with Stokes power ratio verification, this invention solves the technical problems of low stimulated Brillouin scattering (SBS) threshold, poor compatibility of traditional suppression schemes, and difficulty in balancing stability and ease of implementation in existing all-fiber high-power narrow-linewidth laser long-distance transmission. Ultimately, it achieves significant SBS suppression, ensures stable long-distance laser transmission, and simultaneously maintains the characteristics of all-fiber, high-purity output, and scenario scalability (adaptable to fiber amplifiers). To achieve the above objectives, this invention provides an all-fiber high-power narrow-linewidth laser long-distance transmission system comprising: A narrow-linewidth laser provides an initial narrow-linewidth laser signal; a pump source provides high-energy pump light, which is fused with the initial laser signal provided by the narrow-linewidth laser through a pump combiner and input into the gain fiber to form a high-power narrow-linewidth laser; residual pump light is removed by a cladding stripper. The coupling device transmits the narrow linewidth laser signal to be transmitted to the dual-core optical fiber; the dual-core optical fiber serves as the carrier for long-distance transmission of the narrow linewidth laser signal, and increases the transmission efficiency by reducing the Stokes power. One end of the fiber is connected to the output end of the coupling device, and the other end is connected to the output device (8); the output device is used to output the laser signal. The validity verification device verifies validity by calculating the ratio of Stokes power in a dual-core fiber to Stokes power in a regular single-core fiber.

[0007] Furthermore, the devices are connected to each other via a fiber optic fusion splicer.

[0008] Furthermore, the narrow linewidth laser is a fiber laser, a semiconductor laser, or a solid-state laser.

[0009] Furthermore, the output device is an optical fiber end cap.

[0010] Furthermore, the optical fiber structure is not limited to high-power narrow-linewidth laser transmission; by replacing the passive dual-core fiber in the system with an active dual-core fiber, it can be applied to optical fiber amplifiers.

[0011] Furthermore, the dual-core optical fiber can be replaced with a multi-core optical fiber, including 2-core, 4-core, and 8-core optical fibers.

[0012] Furthermore, in the core 1 of the dual-core optical fiber, the power accumulation of the Stokes light is as follows: ; in , represents the Stokes optical power within core 1 of the dual-core optical fiber; This is the initial injected power; The initial power of the Stokes light; The Brillouin gain coefficient; denoted as , where is the effective mode area of ​​the optical fiber; k is the coupling coefficient of the dual-core optical fiber. For transmission distance variables; This represents the total transmission length of the dual-core optical fiber.

[0013] Furthermore, in the core 2 of the dual-core optical fiber, the power accumulation of the Stokes light is as follows: ; in , represents the Stokes optical power within core 2 of the dual-core optical fiber; This is the initial injected power; The initial power of the Stokes light; The Brillouin gain coefficient; denoted as , where is the effective mode area of ​​the optical fiber; k is the coupling coefficient of the dual-core optical fiber. For transmission distance variables; This represents the total transmission length of the dual-core optical fiber.

[0014] Furthermore, the total Stokes light power in the dual-core optical fiber is: ; In a typical single-core optical fiber, the Stokes power accumulation is: ; Let R be the ratio of the Stokes power in a dual-core fiber to the Stokes power in a standard single-core fiber. Then: R= ; in , These represent the Stokes optical power in core 1 and core 2 of the dual-core optical fiber, respectively. This is the sum of the Stokes optical power of the two cores in a dual-core optical fiber; This represents the Stokes power in a single-core optical fiber. This is the initial injected power; The initial power of the Stokes light; The Brillouin gain coefficient; denoted as , where is the effective mode area of ​​the optical fiber; k is the coupling coefficient of the dual-core optical fiber. For transmission distance variables; This represents the total transmission length of the dual-core optical fiber.

[0015] In another aspect, the present invention provides a method for long-distance transmission of high-power, narrow-linewidth laser light using an all-fiber optic cable, comprising the following steps: Step 1: Utilize a narrow-linewidth laser to output an initial low-power, narrow-linewidth laser seed signal; output high-energy pump light through a pump source, and fuse the pump light with the laser seed signal through a pump combiner, injecting them together into the gain fiber; the gain fiber absorbs the pump light energy, amplifying the laser seed signal into a high-power, narrow-linewidth laser, while a cladding stripper removes residual unabsorbed pump light, resulting in a pure high-power, narrow-linewidth laser signal; Step 2: The pure high-power narrow-linewidth laser signal is efficiently introduced into the multi-core optical fiber through the coupling device. The laser energy is periodically coupled between multiple cores of the multi-core optical fiber. By spatially dispersing the power density, the nonlinear effect of stimulated Brillouin scattering is suppressed, and long-distance stable transmission is achieved. Step 3: The laser signal transmitted through the multi-core fiber is exported through the fiber end cap. The beam expansion characteristics of the end cap are used to reduce the power density at the end face and avoid end face damage, ultimately outputting a stable high-power narrow-linewidth laser.

[0016] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: 1. The present invention provides an all-fiber high-power narrow-linewidth laser long-distance transmission system, which disperses high-power laser energy to multiple fiber cores through periodic coupling between the fiber cores of a dual-core fiber, thereby significantly reducing the power density of a single fiber core.

[0017] 2. The present invention provides an all-fiber high-power narrow-linewidth laser long-distance transmission system, which provides high-energy pump light through a pump source, and the initial laser signal provided by the pump combiner and the narrow-linewidth laser is fused into the input gain fiber to form a high-power narrow-linewidth laser. The cladding stripper removes the residual pump light, thereby achieving the technical effect of obtaining a pure high-power narrow-linewidth laser signal. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of an all-fiber high-power narrow-linewidth laser long-distance transmission system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a double-clad single-core optical fiber structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of a double-clad multi-core optical fiber structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of power transfer in a multi-core optical fiber according to an embodiment of the present invention; Figure 5 This is a flowchart of the all-fiber high-power narrow-linewidth laser long-distance transmission method according to an embodiment of the present invention; In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1-narrow linewidth laser, 2-pump source, 3-pump combiner, 4-gain fiber, 5-cladding stripper, 6-coupling device, 7-dual-core fiber, 8-output device, 9-inner cladding, 10-outer cladding, 11-single-core fiber, 12-multi-core fiber. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0020] Please refer to Figure 1A long-distance transmission system for high-power narrow-linewidth lasers using all-fiber optics, wherein the high-power narrow-linewidth fiber laser is a narrow-linewidth laser with a MOPA structure. In this system, a narrow-linewidth laser 1 is used to provide a narrow-linewidth laser seed, with an output wavelength of 1064nm and a linewidth of 1GHz. Its output end is connected to the signal input end of the signal pump combiner 3. The narrow-linewidth laser 1 can be a fiber laser, a semiconductor laser, or a solid-state laser. The output end of the pump source 2 is connected to the pump input end of the signal pump combiner 3. The output section of the signal pump combiner 3 is connected to the gain fiber 4, which has a core diameter of 25μm and an inner cladding diameter of 400μm. The other end of the gain fiber 4 is connected to the cladding stripper 5 to remove residual pump light. The output end of the cladding stripper 5 is connected to the input end of the coupling device 6, and the laser is transmitted to a dual-core fiber 7, where both the core and side core diameters are 25μm. Preferably, the dual-core fiber has 2, 4, or 8 cores. After transmission through the dual-core fiber, the laser is output through the output device 8. Output device 8 is a fiber end cap, which reduces the power density at the end face and avoids end face damage, ultimately outputting a stable high-power, narrow-linewidth laser. Interconnection between system devices is achieved through a fiber optic fusion splicer.

[0021] This fiber optic structure is not limited to high-power, narrow-linewidth laser transmission; by replacing the passive dual-core fiber in the system with an active dual-core fiber, it can be applied to fiber optic amplifiers.

[0022] The principle behind this device's ability to transmit high-power, narrow-linewidth lasers over long distances is analyzed below: Please refer to Figure 2 In traditional double-clad optical fibers, there is only one core 11, and all narrow-linewidth lasers are confined within this region. Therefore, the core region has extremely high power density. Backward Stokes light accumulates continuously within the core, exhibiting exponential growth, which poses a serious threat to the stable operation of the system.

[0023] ; Where g is the seed power of SBS, and g is the Brillouin gain coefficient. L represents the injected narrow-linewidth laser power, L is the fiber length, and A is the effective mode area.

[0024] Please refer to Figure 3 In a dual-core optical fiber, multiple cores share the same cladding. Based on whether energy coupling exists between the cores, it can be divided into conventional dual-core optical fibers and integrated dual-core optical fibers. Integrated dual-core optical fibers have cores spaced far apart, resulting in very weak power crosstalk, and have been widely used in optical fiber communication. Please refer to [reference needed]. Figure 4 In a conventional dual-core fiber, the energy injected from a single core will be periodically exchanged among all the cores.

[0025] Taking a dual-core fiber as an example, assuming that at z=0, all power is concentrated in core 1, the power evolution between the two cores can be expressed as follows based on the existing coupling mode equations and power evolution formulas for dual-core fibers: Pcore1= ; Pcore2= ; Where Pcore1 is the transmission power in fiber core 1, Pcore2 is the transmission power in fiber core 2, and k is the coupling coefficient between the two fiber cores.

[0026] Based on the above relationship, in one of the two-core optical fibers, the cumulative transmission distance... ,or .

[0027] In core 1 of the dual-core fiber, the power accumulation of the Stokes light is as follows: ; In core 2 of the dual-core optical fiber, the power accumulation of the Stokes light is as follows: ; The Stokes power in the two fiber cores is: ; In a typical single-core optical fiber, the Stokes power accumulation is: ; Let R be the ratio of the Stokes power in a dual-core fiber to the Stokes power in a standard single-core fiber. Then: R= To simplify it: R= ); in , These represent the Stokes optical power in core 1 and core 2 of the dual-core optical fiber, respectively. This is the sum of the Stokes optical power of the two cores in a dual-core optical fiber; The initial power of the Stokes light; The Brillouin gain coefficient; denoted as , where is the effective mode area of ​​the optical fiber; k is the coupling coefficient of the dual-core optical fiber. For transmission distance variables; This represents the total transmission length of the dual-core optical fiber.

[0028] For large-mode-field fibers with a core diameter of 30µm and a cladding diameter of 400µm, the R-value can reach below 50%, significantly reducing the optical power of Stokes fibers and enhancing transmission capability.

[0029] Taking a square layout with 4-core optical fibers as an example, the rest of the equipment remains unchanged. Power evolution formula: Based on coupled-mode theory, initial power After injection into fiber core 1, the power evolution formula for the four fiber cores is as follows: Stokes optical power calculation: Substituting into the Stokes optical power accumulation formula, the total Stokes optical power of the 4-core fiber is calculated. With single-core optical fiber The ratio R is: in This is the sum of the Stokes optical power of all cores in a 4-core optical fiber; This is the initial injected power; The initial power of the Stokes light; The Brillouin gain coefficient; denoted as , where is the effective mode area of ​​the optical fiber; k is the coupling coefficient of the dual-core optical fiber. For transmission distance variables; R is the total transmission length of the dual-core fiber; R is the ratio of the Stokes optical power of the dual-core fiber to that of the single-core fiber.

[0030] The same R-value method can be derived for other multi-core optical fibers.

[0031] In Example 2, for further optimization of the existing dual-core transmission method, this Example 2 provides a method based on the dual-core transmission system. Through the collaborative design of "hardware architecture optimization + deep intervention of DSP algorithm", a real-time digital signal processing module is introduced on the dual-core optical fiber infrastructure to realize dynamic monitoring, accurate modeling and reverse compensation of nonlinear effects, break through the power-distance bottleneck of the existing transmission system, and adapt to application scenarios such as long-distance laser power transmission and cross-domain laser communication.

[0032] The system adopts a full-link architecture of "transmitter preprocessing - transmission real-time monitoring - receiver DSP compensation - output closed-loop optimization," using dual-core optical fiber as the transmission carrier. The front end consists of a high-power, clean laser emission unit composed of a narrow-linewidth fiber laser, a pump combiner, gain fiber, and a cladding stripper, outputting narrow-linewidth laser light which is injected into the dual-core fiber. Distributed optical sensors are deployed every 20km along the link to collect transmission status data in real time. In the mid-section, a high-speed photodetector and analog-to-digital converter (ADC) convert the transmitted optical signal into an electrical signal and simultaneously acquire the I / Q components. The core DSP unit adopts an FPGA+ARM heterogeneous architecture, achieving precise compensation through signal preprocessing, multi-parameter coupled nonlinear modeling (for SBS / SPM / XPM), adaptive predistortion, and Volterra series inverse filtering, with a processing delay of <10μs. The back-end reconstructs the optical signal through a 14-bit 60GS / s digital-to-analog converter (DAC) and a 20GHz electro-optic modulator, and finally outputs it through a high-transmittance coated fiber end cap. At the same time, the output indicators are monitored in real time by a beam quality analyzer and fed back to the DSP unit to form a closed-loop control, ensuring stable transmission throughout the entire link.

[0033] Distributed optical sensing integration: In a dual-core fiber optic link, a temperature-power sensor based on a fiber optic grating (FBG) is embedded every 20 km. Temperature sensitivity is achieved by monitoring the wavelength shift of the FBG's reflection spectrum. The system can obtain the intensity of nonlinear effects in different transmission segments in real time (such as the proportion of backward Stokes optical power caused by SBS) and power attenuation, providing segmented data support for DSP compensation and avoiding local overcompensation or undercompensation problems caused by "whole segment compensation".

[0034] I / Q signal synchronous acquisition: Dual-channel photodetectors are used to acquire the output signals of the dual-core optical fiber respectively. A high-precision clock synchronization module (synchronization error <1ps) ensures the time alignment of the two-channel I / Q signals, avoiding compensation deviation caused by signal delay. It is especially suitable for dynamic compensation scenarios of power coupling between dual cores.

[0035] DSP Algorithm System and Implementation Process Core algorithm logic: Based on the core principle of "modeling first, then compensation, and finally optimization," a multi-level algorithm system is constructed. Compensation strategies are designed for the three main nonlinear effects: SBS, SPM, and XPM. The specific logic is as follows: Signal preprocessing layer: The acquired electrical signals are subjected to noise suppression (using wavelet threshold denoising algorithm, noise suppression ratio >30dB), DC offset cancellation (adaptive DC subtraction, offset <0.1mV), and signal equalization (fractional interval equalizer to compensate for intersymbol interference caused by fiber dispersion), providing a clean signal foundation for subsequent nonlinear modeling.

[0036] Nonlinear modeling layer: Based on segmented power and temperature data, a "multi-parameter coupled nonlinear model" is constructed. For SBS: A segmented Stokes power prediction model is adopted, combined with the power evolution formula of dual-core fiber. Introducing a temperature correction factor Real-time calculation of SBS threshold and Stokes optical power ratio for different transmission segments; For SPM / XPM: A "polynomial phase retrieval model" is used to represent phase distortion as a power series. The coefficients were fitted using the least squares method. This enables precise quantification of phase distortion.

[0037] Inverse compensation layer: Based on the modeling results, a dual compensation strategy of "adaptive predistortion + real-time inverse filtering" is adopted. Predistortion compensation: At the transmitting end, a predistortion signal opposite to the nonlinear distortion is generated by DSP (e.g., to compensate for phase lead caused by SPM, a phase lag signal is injected) to cancel out part of the nonlinear effects in advance. The predistortion compensation efficiency is >60%. Real-time reverse filtering: The "Volterra series filtering algorithm" is used at the receiving end. The 2nd to 4th order Volterra kernel function is used to perform reverse convolution operation on the acquired distorted signal to accurately eliminate the power attenuation caused by SBS and the spectral broadening caused by SPM. The signal distortion after compensation is <3%.

[0038] Closed-loop optimization layer: This layer incorporates monitoring data from the output beam quality analyzer. (Power stability) is fed back to the DSP unit, and the compensation parameters (such as Volterra kernel function coefficients and predistortion amplitude) are dynamically adjusted through the PID algorithm. When transmission conditions change (such as temperature fluctuations) Power fluctuation When the parameter iteration is completed within 10μs, the system can be kept stable for a long time.

[0039] Algorithm Implementation Flow Initialization phase: After the system is powered on, the DSP unit loads the basic compensation parameters (based on offline training data of typical transmission scenarios), and at the same time, the distributed sensors collect initial link data (temperature, power baseline) to establish an initial nonlinear model. Real-time operation phase: The I / Q signal output from the dual-core optical fiber is acquired once every 1μs, and the temperature and power data of the sensor are acquired simultaneously. The nonlinear model is updated every 10μs, adjusting the Volterra filter coefficients and predistortion parameters. Every 100μs, the output beam quality data is fed back to the closed-loop optimization module to correct the compensation strategy. Anomaly Handling Phase: When nonlinear effects exceed the standard (e.g., Stokes optical power ratio > 10%) or hardware failure (e.g., detector signal loss), the DSP unit triggers an alarm and automatically switches to the backup compensation parameter set to ensure that the signal is not interrupted.

[0040] Example 3 Please refer to Figure 5 This embodiment 3 provides a method for long-distance transmission of high-power, narrow-linewidth lasers using all-fiber optics, comprising the following steps: Step 1: Use a narrow-linewidth laser 1 to output an initial low-power, narrow-linewidth laser seed signal; output high-energy pump light through pump source 2, and fuse the pump light with the laser seed signal through pump combiner 3, and inject them together into gain fiber 4; gain fiber absorbs pump light energy, amplifies the laser seed signal into a high-power narrow-linewidth laser, and at the same time removes residual unabsorbed pump light 5 through cladding stripper, to obtain a pure high-power narrow-linewidth laser signal; Step 2: The pure high-power narrow-linewidth laser signal is efficiently introduced into the multi-core optical fiber 7 through the coupling device 6. The laser energy is periodically coupled between multiple cores of the multi-core optical fiber. By spatially dispersing the power density, the nonlinear effect of stimulated Brillouin scattering (SBS) is suppressed, and long-distance stable transmission is achieved. Step 3: The laser signal transmitted through the dual-core fiber is exported through the fiber end cap. The beam expansion characteristics of the end cap are used to reduce the power density at the end face and avoid end face damage, ultimately outputting a stable high-power narrow-linewidth laser.

[0041] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A long-distance transmission system for high-power, narrow-linewidth lasers using all-fiber optics, characterized in that: Includes: a narrow linewidth laser (1) provides an initial narrow linewidth laser signal; a pump source (2) provides high-energy pump light, which is fused with the initial laser signal provided by the narrow linewidth laser (1) through a pump combiner (3) and input gain fiber (4) to form a high-power narrow linewidth laser; and a cladding stripper (5) removes residual pump light. The coupling device (6) transmits the narrow linewidth laser signal to be transmitted to the dual-core fiber (7); the dual-core fiber (7) serves as the carrier for long-distance transmission of the narrow linewidth laser signal, and increases the transmission efficiency by reducing the Stokes power. One end of the fiber is connected to the output end of the coupling device (6), and the other end is connected to the output device (8); the output device (8) is used to output the laser signal. The validity verification device verifies validity by calculating the ratio of Stokes optical power in a dual-core fiber to that in a regular single-core fiber. The validity was verified by the ratio R of the total Stokes optical power in a dual-core fiber to the Stokes optical power in a conventional single-core fiber. , This is the sum of the core power coupling evolution power of the two Stokes fiber cores in the dual-core optical fiber. The Stokes power of a single-core fiber; the smaller the Stokes power ratio R, the more effective it is.

2. The all-fiber high-power narrow-linewidth laser long-distance transmission system according to claim 1, characterized in that, The devices are connected by a fiber optic fusion splicer.

3. The all-fiber high-power narrow-linewidth laser long-distance transmission system according to claim 1, characterized in that, The narrow linewidth laser (1) is a fiber laser, a semiconductor laser, or a solid-state laser.

4. The all-fiber high-power narrow-linewidth laser long-distance transmission system according to claim 1, characterized in that, The output device (8) is an optical fiber end cap.

5. The all-fiber high-power narrow-linewidth laser long-distance transmission system according to any one of claims 1-4, characterized in that, The fiber optic structure is not limited to high-power narrow-linewidth laser transmission; by replacing the passive dual-core fiber in the system with an active dual-core fiber, it can be applied to fiber optic amplifiers.

6. The all-fiber high-power narrow-linewidth laser long-distance transmission system according to any one of claims 1-4, characterized in that, The dual-core optical fiber can be replaced with a multi-core optical fiber, including 2-core, 4-core, or 8-core fibers.

7. The all-fiber high-power narrow-linewidth laser long-distance transmission system according to claim 1, characterized in that, In the core 1 of the dual-core optical fiber, the power accumulation of the Stokes light is as follows: ； in , represents the Stokes optical power within core 1 of the dual-core optical fiber; This is the initial injected power; The initial power of the Stokes light; The Brillouin gain coefficient; denoted as , where is the effective mode area of ​​the optical fiber; k is the coupling coefficient of the dual-core optical fiber. For transmission distance variables; This represents the total transmission length of the dual-core optical fiber.

8. The all-fiber high-power narrow-linewidth laser long-distance transmission system according to claim 1, characterized in that, In core 2 of the dual-core optical fiber, the power accumulation of the Stokes light is as follows: ； in , represents the Stokes optical power within core 2 of the dual-core optical fiber; This is the initial injected power; The initial power of the Stokes light; The Brillouin gain coefficient; denoted as , where is the effective mode area of ​​the optical fiber; k is the coupling coefficient of the dual-core optical fiber. For transmission distance variables; This represents the total transmission length of the dual-core optical fiber.

9. The all-fiber high-power narrow-linewidth laser long-distance transmission system according to claim 1, characterized in that, The total Stokes optical power in the dual-core optical fiber is: ； In a typical single-core optical fiber, the Stokes power accumulation is: ； Let R be the ratio of the Stokes power in a dual-core fiber to the Stokes power in a standard single-core fiber. Then: R= ； in , These represent the Stokes optical power in core 1 and core 2 of the dual-core optical fiber, respectively. This is the sum of the Stokes optical power of the two cores in a dual-core optical fiber; This represents the Stokes power in a single-core optical fiber. This is the initial injected power; The initial power of the Stokes light; The Brillouin gain coefficient; denoted as , where is the effective mode area of ​​the optical fiber; k is the coupling coefficient of the dual-core optical fiber. For transmission distance variables; This represents the total transmission length of the dual-core optical fiber.

10. A method for long-distance transmission of high-power, narrow-linewidth laser light using an all-fiber optic cable, characterized in that: Includes the following steps: Step 1: Use a narrow-linewidth laser (1) to output an initial low-power, narrow-linewidth laser seed signal; output high-energy pump light through a pump source (2), and fuse the pump light with the laser seed signal through a pump combiner (3), and inject them together into the gain fiber (4); the gain fiber absorbs the pump light energy, amplifies the laser seed signal into a high-power narrow-linewidth laser, and removes the residual unabsorbed pump light through a cladding stripper (5) to obtain a pure high-power narrow-linewidth laser signal; Step 2: The pure high-power narrow-linewidth laser signal is efficiently introduced into the multi-core fiber (7) through the coupling device (6). The laser energy is periodically coupled between multiple cores of the multi-core fiber. By spatially dispersing the power density, the nonlinear effect of stimulated Brillouin scattering is suppressed, and long-distance stable transmission is achieved. Step 3: The laser signal transmitted through the multi-core fiber is exported through the fiber end cap. The beam expansion characteristics of the end cap are used to reduce the power density at the end face and avoid end face damage, ultimately outputting a stable high-power narrow-linewidth laser.

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