Research On The Polarization Error And Key Component Of Optical Fiber Gyroscope

Fiber optical gyroscope (FOG), operating based on the mechanism of Sagnac effect, is an important measuring facility of angular velocity with all solid structure. Due to its many unique advantages, such as low expense, small volume, light weight, fast initiation, large dynamic domain and high precision, it has wide application future for military and civil field and has been a hot spot in the research of fiber sensors. In order to further elevate gyroscope's capabilities, it's decisive that how to efficiently reduce the output errors and develop the key components with high performances. In this paper we focus on the investigation of polarization errors arose from different devices and fiber couplers.Polarization error has significant influence on the stability of zero offset, thus the study on polarization error arose from different devices is valuable for further optimization of design and improvement of performances of FOG In this thesis, the Jones matrixes of various devices are established and the formula of intensity output is deduced by utilizing the theory of transferring matrix and coherence matrix. The light phase is demodulated from the intensity output through square wave modulation. Then the polarization errors arose from the fluctuation of light source (including the power fluctuation and polarization degree fluctuation), the fluctuation of coupling ratio of polarization maintaining fiber coupler and the alignment error are studied respectively. The error capacity of optical devices for gyroscopes of different accuracy class is given after comparing the polarization errors induced by the error sources mentioned above.Polarization maintaining fiber coupler is a key component of FOG, its stability of coupling ratio is affected by several factors, such as polarization dependence, wavelength dependence, temperature dependence and birefringence dependence. The coupled coefficient is deduced theoretically based on the theory of coupling mode. In succession, according to the orthogonality of polarization modes in polarization maintaining fiber (PMF) the coupled coefficients of fast axis and slow axis are derived. On the basis of former theoretical analysis, the variation of coupling ratio of PANDA polarization maintaining fiber coupler caused by alignment error, wavelength fluctuation, varied coupling length, changed birefringence are computed numerically. This study is meaningful to the fiber selection, draw technique and encapsulation technique for the couplers with high performances. Dual-core photonic crystal fiber (PCF) can be applied to broadband couplers. In order to design an innovative type of broadband and polarization-insensitive coupler with excellent properties based on Fluorine-doped dual-core PCF, the impacts of structural and physical parameters on the coupling characteristics of dual-core PCF are investigated numerically by employing the finite element method (FEM). By referring to the numerical analysis, a newly constructed dual-core PCF coupler with an elliptical central air hole is proposed and its broadband and polarization-insensitive characteristics are optimized. This design improves the compatibility dual-core PCF with conventional fiber and feasibility in fiber fabrication remarkably.