Research On Thermal Characteristics Of Dual-polarization Fiber Optic Gyroscope

Fiber optic gyroscope(FOG)is an inertial navigation instrument based on the Sagnac Effect.Compared with traditional gyroscope,FOG has advantages of high precision,fast startup,impact resistance,low cost,long life,etc.,and has been widely used in inertial measurement occasions such as sea,land,air and space.At present,the most mature interferometric FOG is in single-polarization type,which only uses one axis of the polarization-maintaining fiber to transmiss.Although this kind of FOG is simple in structure and easy to realize,the contradiction between precision,weight and volume and environmental adaptability will become more and more prominent with the continuous improvement of the requirements on precision,weight and volume in the development of fiber optic gyroscope.Dual-polarization FOG is a new type which based on the traditional single-polarization interferometric FOG.By connecting a polariztion beam splitter(PBS)at each side of the polarization-maintaining fiber(PMF)coil,the input light transmit along the fast and the slow axis of the PMF coil twice before output,thus doubling the effective optical path and the theoretical accuracy.Like the single-polarization FOG,dual-polarization fiber optic gyroscope is sensitive to the ambient temperature changes due to the influence of photoelectric devices' temperature characteristics.Among them,the fiber coil is most seriously affected by the temperature.So,in this paper,the theoretical analysis and experimental research of the fiber optic path of dualpolarization FOG are carried out.Firstly,this paper introduces the basic situation of FOG briefly,and describe the purpose,significance and main content of research on temperature characteristics of double-polarization FOG.Secondly,this paper introduces Sagnac principle,and the relevant knowledge of PMF and PBS.Through discussion the influence of temperature characteristics of each optical device,temperature noise and residual temperature,it is confirmes the research of this paper is based on fiber coil.Thirdly,the thermal-induced non-reciprocity error of FOG is analyzed by considering temperature and thermal-stress.This paper introduces the structure of double-polarization FOG,and analyzes its thermal error according to its special optical structure.With the different position of 90° polarization transfer welding spot,this paper establish two error models between conversion fusion contact located in inner and side.Then,the 2D cross-section model of the fiber coil with the quadrupole symmetric winding method is established.In addition,by using the previous error formula,the discretization model of thermal non-reciprocity error of dual-polarization FOG is established.The thermal error of dual-polarization FOG was simulated and analyzed in position of 90° melting point,index temperature coefficient and tail.Then,this paper introduces the finite element briefly,and use simulation software COMSOL to analyze the temperature characteristics of the dual-polarization FOG in previous model.It concludes the relative position of temperature excitation,the rate of environmental temperature change and the parameters of coil.Finally,by using dual-polarization FOG prototype as experimental object,the static precision,scale factor stability and temperature characteristics are studied.These experiments prove the correctness and improvement of accuracy,and verifies the correctness of the error model and discretization model established of fiber coil in the simulation.