Optical Field Distribution Investigation Of Optical Fiber Based On Vector Finite Element Method

In the modern society, the optical access to the home and even extends to the users' computer terminals are the progressive realization of truly all-optical network in many developed countries. Optical fiber is the most basic deliver physical medium in optical communication system, so it is very important to research the fiber optical field distribution. Through that, the mode field structure, transfer constant, transfer or closing conditions, transmission power, the number of modes and other characteristics can be further analyzed. The transmission characteristics of optical fiber can be understand visually and directly based on the theory.Vector finite element is a widely used numerical method in electromagnetic engineering calculation, but there are few reports of the applications in the research fiber optical field distribution. This thesis introduces the method to the calculation of fiber optical field distribution.The thesis comprehensively reviews the development process of optical analysis, vector finite element method'domestic and international developments, latest research results and their characteristics and applications.By studying the mode theory of fiber optical field, the mathematical expressions of light wave field are gave. Then from the fiber vector wave equation, the thesis analyzes and discusses the classification of optical field patterns, the linear polarization mode in actual transmission and photoelectric field distribution of each LPmn mode and gives the light field model parameter based on obtaining the characteristic equation of optical vector solution. The thesis comprehensively analyzes the main technical specifications and typical characteristics of the step-and graded index multimode fiber and the common single-mode fiber, discusses the attenuation, dispersion and nonlinear optical effects and researches the attenuation spectrum of single-mode fiber, SI multimode fiber and GI multimode fiber and the dispersion spectrum of several common single-mode fiber.The thesis researches the basic principles of vector finite element method, introduces the variational principle and the solution process and structures the vector basis functions of the rectangular block and tetrahedral unit. Then from full the electric field vector functionals, study the rectangular blocks unit matrix of the passive region filled in axial anisotropic media and the tetrahedral unit matrix of the passive region filled in isotropic homogeneous medium, which are calculated respectively. In addition, the interpolation-type triangular and tetrahedral higher order vector finite element are constructed.The equivalent vector functionals of lossless medium and lossy medium problems which define the new vector inner product based on generalized variational principle are deduced from the non-homogeneous vector wave equation which is satisfied by the optical electric and magnetic field vector. Then by establishing G.652 fiber theoretical model, setting the solving process and using tetrahedral element mesh to discretize vector functional equivalent, the G.652 fiber optical field distribution of electric vector, optical intensity distribution and dispersion curves are numerically simulated, which are consistent with the conclusions of the actual fiber parameters. The results show that it is feasible and effective to study the fiber optical field distribution based on vector finite element method.