Modular Propagation Theoretical Study On Optical Voltage Sensor Based On Modular Interference

The voltage sensor based on modular interference has solved many problems of traditional transformer. So, it has aroused the extensive attetion from people. The research on the propagation characteristics of elliptical-core fiber in this paper is a basic theoretical research work for the study of the voltage sensor based on modular interference.First of all,this paper presents the situation for optical fiber voltage transformers as well as the background of researchs of them today. There are many problems in traditional voltage transformers. After that the fiber voltage sensor based on modular interference is put forward.Then use the prevalant Marcatili method to analyse the elliptical core optical fiber which we choose.Based on the parameters of the fiber,the field function and propagation constant of the modes are obtained.Use the powerful funcion for plotting of Mathematica,we can protract the field sketch of single mode and the modeular interference field.Then give the rules of modular phase difference and interference output intensity distribution.Based on the method of several modes interference in perfect circular core step-index fiber,then the calculate the output indensity for the three modes interference when there is the second order mode in elliptical core fiber.At last,to amend the differrence in the near field due to Macatili method ngnores the influence in four corenrs.In the paper,the effective index method and the perturbation opproach are used to caculate the propagation constant.The output indensity of modes function and modular interference are given by perturbation approach.Through the comparing the results from the three methods,point out the perturbation opproach is more accurtate than the others.The precious direction of making the fiber voltage sensor use widely in the future is presented by the theory and experiment research above.