Study On Techniques Of Fusing Splicing In High-power Fiber Laser

Fiber lasers are widely used in various fields with good beam quality,monochromaticity and high stability.With the emergence of double-clad large mode field fiber,high power pump energy input and high power laser transmission problem can be solved.However,in the laser structure,the quality of fiber fusion directly affects the performance of fiber lasers.Therefore,the study of fiber fusion splicing technology is of great significance.In this paper,the fusion splicing process and temperature control of the fusion point of the fiber laser are studied,which solves the problem of high fiber splicing defects in high power fiber lasers and high splicing temperature.In this paper,the demand for the project,to solve the development of 4kW continuous fiber laser key splicing point of the high temperature problem.The finite element analysis and fiber tracking are used to simulate the fiber splicing point.The welding parameters are optimized by using the control variable method.The problem of high splicing point temperature is solved by improving the quality of the splicing point and increasing its heat dissipation rate.Specific work is as follows:(1)studied the theory of splicing points.Firstly,the optical characteristics of the splicing points in different positions of the laser are analyzed based on the basic structure of the fiber laser and the optical transmission characteristics of the doubleclad fiber.Secondly,the mode coupling equation in the case of refractive index perturbation is derived based on the optical waveguide model theory.Based on the propagation characteristics of the radiation pattern,the influence of the spatial transient of the high-order mode on the output power and thermal effect of the laser in the fiber laser is briefly analyzed.Finally,the splicing process of fiber is introduced.The mechanical,material and optical properties of the fusion fusion point are analyzed,and the method of splicing quality evaluation is summarized.(2)studied the related technology in fiber splicing.First of all,the pretreatment of the fiber before splicing,combined with the fiber material and stress characteristics of the optical fiber cutting angle and axial dislocation caused by the melting point defects.Second,the refractive index of the cladding layer changes in the boundary.Two kinds of non-contact detection methods of reflection method and refraction method are summarized.Using Zemax software to analyze the microfilm morphology of the welds by refraction method.For the passive and doped fiber junctions,the circular cladding of the Zemax analog fiber propagates to the hexagonal cladding.Finally,the optimization experiment of fiber splicing parameters is designed.The influence of splicing parameters such as splicing time,splicing power and thermal push delay on splicing quality is summarized by a large number of experiments.(3)studied the fiber post-processing technology.First,the thermal effect at the fiber fusion point is studied.The energy loss and mode field change of the incision before and after coating were simulated by Tracpro and Comsol software.The temperature distribution of the splicing point and the incision was verified by experiments.This problem is solved by selecting the appropriate organic solvent for the solder joint and the front and rear incisions.Secondly,several fiber splice cooling structures were designed.The temperature distribution of the splicing point and the heat dissipation effect of the different groove type on the fiber splicing point are analyzed by using Comsol.At the same time,the influence of thermal radiation on the temperature of the doped fiber was studied by combining the radiation theory.Finally,the core thermal stress is simulated.The use of the design of the U-type cooling structure not only reduces the fiber temperature and make the fiber temperature more uniform,reducing the core thermal stress.The research on the splicing technology of high power fiber laser solves the problem of heat generation at key fusion points.Under the condition of natural air cooling,the temperature of 1kW pump light doped fiber is below 40 ?.Improve the efficiency and stability of high-power fiber lasers,and provide important technical support for the successful development of 4kW continuous fiber lasers.