Theory And Technology Of Fiber Optic Gyro Using The Polarization-maintaining Optical Circulator

Fiber optic gyroscope(FOG)is an inertial navigation instrument based on the Sagnac effect.It is widely used to measure the angular velocity of the carrier relative to the inertial coordinates in military and civil fields.In this thesis,we use the polarization-maintaining optical circulator(PMOC)to improve the optical path structure of the traditional open-loop FOG,and we explore a new direct sampling demodulation method.This system can greatly reduce the cost of FOG.This thesis mainly includes two aspects of optical path structure and demodulation method,main points are as follows:In the part of optical path structure,a new FOG structure is proposed to replace the optical coupler and polarizer with PMOC,which can improve the utilization rate of optical power.Finally,the transmission matrix modeling and polarization error analysis of this FOG structure are carried out,and the feasibility of the proposed scheme is verified by experiments.In the part of demodulation method,traditional modulation and demodulation methods are introduced firstly.Then,aiming at the serious resource consumption of traditional modulation and demodulation methods,the direct sampling modulation and demodulation method is proposed.Its principle is described and the digital demodulation process of this method using field programmable gate array(FPGA)is introduced in detail.Finally,the error of the demodulation method is analyzed,including the influence of sampling point phase error and modulation depth error on output results.The experimental results are as follows:At room temperature conditions,the digital phase-locked amplifier is used to modulate and demodulate the FOG with 600 m polarization maintaining fiber ring.The zero bias is 7.75°/h.The nonlinearity of FOG is 197 ppm.And the zero bias instability is 0.064°/h.The direct sampling modulation and demodulation method is used to test the same system,and the results are as follows:The zero bias is 17°/h.The nonlinearity of FOG is 1140 ppm.And the zero bias instability is 0.119°/h.