Research And Measurement Of Polarization Characteristics Of Fiber In Fiber Optic Current Sensor

As the basic theory of the Fiber Optics,the polarization in the optical fiber has been paid more attention by the researchers as the rapidly developing of the optical fiber communication and the optical fiber sensing.In the field of optical fiber sensing,the sensor based on the polarization measurement is developing rapidly and plays an important role in various fields.This dissertation is based on the polarization analysis,study and analyze the polarization phenomenon of the optical fiber especially the birefringence characteristic,including the research on the binary polarization measurement system(PMS),analysis of the measurement algorithms for the linear birefringence and the circular birefringence,modeling and simulation of the Fiber Optical Current Sensor(FOCS),distributed measurement of the birefringence based on the polarization optical frequency domain reflectometer(POFDR).The major innovations of this dissertation are as follows:1.An accurate and simultaneous measurement method for fiber linear and circular birefringence based on the binary PMS is proposed.Compared with the polarization measurement based on the analog technology in the past,our measurement has the advantages of accuracy,repeatability and high resolution,which are confirmed in the experiment in this dissertation.By the binary PMS,the residual linear birefringence and circular birefringence in the spun fiber are simultaneously measured,and the temperature coefficients of the two parameters in the range of-40°C to 80°C are obtained for the first time,the fluctuation of the measured results are both less than 1%.The method and the experimental results presented in this dissertation will be of great value to the practical application of the FOCS.2.Based on the theory of wave optics,we first study the interferometric reflective FOCS and establish the theoretical model of the interferometric reflective FOCS.Then,we simulate the effect of the linear and circular birefringence on the accuracy of the FOCS.After that,based on the actual measurement results of the spun fiber,the simulation of the FOCS is carried out by using the measured data.According to the characteristics of the temperature dependence of the spun fiber,the relative change of Faraday rotation angle is defined as(43),this parameter is very necessary for the temperature compensation work in the practical application of the FOCS.3.The distributed measurement of linear birefringence in an optical fiber is studied in this dissertation.First,we study the system composition and analyze the principle of POFDR.Then,we analyze the Muller matrix of the round-trip in an optical fiber and obtain the relation between the state of the polarization(SOP)of the input signal and the SOP of the output signal that after the Rayleigh scattering.Finally,we give out a distributed measurement method of the linear birefringence in the optical fiber.