Coupling Mechanism Of Waveguide Microstructured Fiber And Standard Fiber

A novel coupling technique based on waveguide microstructured fiber and standard single mode fiber was proposed by splicing and tapering the fusion point between the two fibers. There is a double taper structure in the heating zone. As stretching, light power comes into the core of microstructured fiber gradually. When the tapered zone reaches to a certain length, the coupling power reaches to the biggest value. The coupling technique is simple and effective. It is helpful to microstructured fiber based apparatus insert into traditional single core single mode fiber net and is helpful to hasten the utilization of microstructured fiber.The coupling model of microsturctured fiber and single core single mode fiber was established and experimentally investigated on multicore fiber, linear-core-array fiber and capillary optical fiber. The experimental setup was established and the experimental results were in agree with the theory predicts. The details are presented as follows:(1) Investigated coupling mechanism between different optical waveguides based on the structure and modes of several waveguides. We often consider about match degree of numerical aperture, mode fields and propagation phase when coupling occurs.(2) Introduced the coupling theory of single core single mode fiber and microstructured fiber in detailed. Based on direct coupling model and parallel column coupling model, the coupling model of single core single mode fiber and multicore single mode fiber was established, and the coupling power was analyzed during the splicing and tapering process. The theoretical model was built up and the characteristic curves of coupling power were simulated for twin core, three core and four core single mode fibers.(3) Considering the promising application in the field of high-quality fiber laser, the super-modes analysis for 5-core-array fiber was presented. The output fields of supermodes were analyzed and experimental tests were done according to two excitation situations.(4) According to Collins equation, the far field supermode distributions of 5-linear-core-array fiber were calculated. The quality of each supermode was analyzed in detail. In contrast, the technique we proposed can improve the beam quality and output power efficiently when linear core array fiber used in fiber laser.(5) Based on the two coupling methods, the coupling characteristics of two kind of capillary fiber, with annular core in the surface or embedded in the fiber well, were investigated respectively. Based on the theory of mode superposition, the relationship of tapered length and coupling efficiency was established. The coupling power was analyzed during the splicing and tapering process. And contrast analysis was given according to the two coupling methods.