Research On Key Techniques Of Photonic Crystal Fiber Optic Gyroscope

Photonic crystal fiber optic gyroscope,(PFC-FOG)is a very potential blue print that uses photonic crystal fiber instead of single mode and polarization-maintaining fiber,it is becoming an effective way to present and future research focus to solve FOG temperature stability,magnetic susceptibility and noise issues.This paper makes environmental error(temperature,vibration,radiation,etc.)FOG drift issues as a starting point,research PFC-FOG key technologies in suppressing the effect of FOG environment research system,at the level of the project realization,this paper includes:(1)The paper introduces the Sagnac effect and expounds the principle of FOG at the first place,PCF-FOG overall structural desigh and theoretical modeling are proposed then,finally,we design a ditital modeling system for the entire FOG system based on each module of FOG is modeled respectively,which pave the way to analyze the error of PCF-FOG for subsequent.(2)According to the light source shared triaxial PCF-FOG program,the overall structure of PCF-FOG is presented.The theoretical models of optics devices and PCF-FOG are established with the help of Jones matrix,and the errors of light path and circuit are analyzed.Then use the finite element method to derive the non-reciprocal phase shift of optical fiber ring under the temperature field and vibration environment,and analyze the influence of erbium-doped PCF light stability on FOG output.The analysis results provide a theoretical basis and direction to improve the performance of PFC-FOG.(3)The calculation and simulation are performed by the optical fiber loop non-reciprocal error model and finite difference time domain(FDTD)method.The results verify that the optimal wound layers is exist,and the eight symmetrical winding method has obvious advantages on the FOG temperature drift suppression and start-up time shorten.According to the characteristics of FOG temperature drift,the PCF-FOG temperature drift compensation approach is proposed,this approach is accomplished by using linear regression method.By using this method,start-up time is further reduced,and the validity of it is verified by the actual gyro data.(4)By an optical fiber wound parameter optimization and multivariate regression model temperature compensation reduced FOG's start-up time,a simulation is operated to vertified PCF-FOG output drift caused by the vibration depends on the axial vibration of shaft,the sum of pigtail's length of two sides is asymmetry and the realation of the size of drift and pigtail's asymmetry is linear,gives the single-stage method to achieve modulation interference fringes large range of situations,finally the magnetic field error,factors faraday phase shift analysis and summary,wherein the line birefringence fiber twist rate,the fiber length can affect the size of drift while Faraday Effect interference contrast two light beams interfere with reverse time;(5)To achieve goal of polarization maintaining PCF-FOG prototype,the thesis broke the two key technologies,which are the splicing technology of PCF and the traditional polarization maintaining fiber splicing technology and fixing axis.By adjusting the current with different welding and mode field changing based on simulation and discharge mode field trimming technology research,the polarization maintaining PCF with low loss and low crosstalk welding is achieved which is the fundamental conditions of designing for the polarization maintaining PCF-FOG prototype.For the signal processing,a normalization algorithm is designed in order to eliminate the light source and optical power.The gyro sensor input DC-coupled is added in the DC channel and normalization algorithm is added in the demodulation algorithm.Under these settings,the control loop parameters are optimized to achieve the goal of signal detection and controlling independent with optical gain.The experimental results show that the improved digital detection system can well inhabitant the influence of changes in the optical path loss.For the temperature compensation,based on the disadvantage of the existing methods,the relevance vector machine(RVM)is built based on the Bayes framework which is used in the FOG temperature compensation.Compared with the temperature compensation based on quadratic polynomial regression,neural networks and SVM temperature compensation method,this method can be used to describe the temperature characteristics of FOG more accurately.The results showed that the gyro bias stability is enhanced obviously under the whole temperature range.(6)In the thesis,the comparative experiments of polarization maintaining photonic crystal fiber sensing loop and conventional fiber ring temperature sensitive loop are tested.The temperature test of the photonic crystal fiber gyro in variable temperature case is also done.The experiment results shows that the polarization maintaining photonic crystal fiber has a strong temperature stability and polarization maintaining photonic crystal fiber optic gyro has the potential advantages of temperature suppressing effect,improving the gyroscopic stability and improve accuracy gyro.In order to verify the PCF-FOG performance further,the thesis proposed PCF-FOG dual-axis rotary navigation system to verified methods.After using the new dual axial rotation method,the positioning error is significantly reduced.And compared with the conventional fiber optic gyro,PCF-FOG meets the accuracy requirements.