Research Of Resonator Fiber Optic Gyroscope Based On Photonic Crystal Fiber

As new generations of inertial sensors,Resonator fiber optic gyro(RFOG)measure the angular velocity by detect the resonance frequency deviation of two light transmitted in the opposite direction.Compared with the interferometric fiber optic gyroscope(IFOG),RFOG exhibits better performance,for example,shorter fiber length,higher detection precision and larger dynamic range which has been valued by inertial technology developed countries.And the United States,Japan and Europe have paid more attention to the investigation of RFOG However,the development of RFOG technology is not mature,the main reasons are that magnetic field and temperature have a great influence on the performance of resonator,and polarization-induced noise and Rayleigh backscattering noise problem are difficult to solve,all of these limit the development of RFOG.In this dissertation,we propose to investigate the performance of RFOG based on photonic crystal fiber,and start from research subject of designing high performance fiber,restraining temperature and magnetic field effects,and suppressing polarization noise and backscattering noise to improve the overall performance of resonator fiber optic gyro.The following main topics are included in this dissertation:1.Design of high performance photonic crystal fiber and temperature effect investigationFirstly,we introduce the principle of photonic crystal fiber(PCF)and by optimizing the birefringence,an octagonal photonic crystal fiber with hybrid structure is proposed.The birefringence reaches Lite magnitude of 10-3,and two zero dispersion points are obtained.Then we propose a hybrid-core photonic crystal fiber by optimizing the fiber core,of which the birefringence reaches the magnitude of 10-2,and the influence of fiber parameter on dispersion,birefringence and nonlinear coefficient are analyzed.Secondly,the influence of temperature effect on the photonic crystal fiber is analyzed by using Finite Element Method(FEM).We mainly analyzes the temperature sensitivity of effective refractive index and birefringence,and the temperature coefficients of those characteristics are obtained by curve fitting-Results show that the temperature sensitivity of the proposed photonic crystal fiber is lower than conventional fiber.For example,the temperature sensitivity of effective refractive index and birefringence are two magnitudes and one magnitude lower than that of conventional fiber,respectively.2.Polarization analysis and Faraday-induced error suppression of resonatorFirstly,we analyze the relationship between resonant characteristics,finesse and sensitivity and characteristics of fiber or coupler.Results show that photonic crystal fiber resonator exhibits similar performance compared with conventional fiber,and it can completely replace the conventional fiber in resonator fiber optic gyro.Secondly,polarization model is obtained by using Jones matrix,and the influences of temperature on resonance curve are analyzed.Results show that there are two eigen-states of polarizations(ESOPs)in resonance curve and temperature fluctuation will result in the change of distance between two ESOPs.Once this fluctuation become serious,it will cause the overlap between the two ESOPs,which will bring distortion in the demodulation of resonance curve.After comparison,it is found that the distance between two ESOPs is larger than that of conventional fiber,which exhibits better performance in suppressing temperature effect.Meanwhile,the Faraday phase error induced by magnetic field is also analyzed,which will be enlarge with the increasing of fiber length and torsion rate.And this will bring error in the gyro signal,which can be depressed by high(or)birefringence.The further investigation shows that high birefringence is at least one magnitude higher than low birefringence in the inhibition of the Faraday phase error.Lastly,a dual-ring resonator is proposed to depress the influence of temperature fluctuation on the polarization,and experimental setups are carried out to test the resonance curve of dual-ring resonator,which accords well with the simulation.It is found that dual-ring resonator exhibits better performance than single-ring resonator in suppressing the temperature effect by comparing the resonance curve and polarization of the two resonators.In addition,the polarization error of dual-ring resonator is two magnitudes lower than that of single-ring resonator.3.Backscattering error suppression based on double triangle wave modulation technologyFirstly,the dynamic response of fiber optic resonator is analyzed and normalized output under triangle wave,sine wave and sawtooth wave modulation technology are investigated.The influence of modulation method,modulation frequency and modulation index on the performance of resonator is also analyzed and results show that triangle wave modulation technology exhibits better performance than the other two modulation technology.Secondly,double triangle wave modulation technology is proposed to suppress the backscattering error in RFOG,and comparing the performance with that of double sine wave modulation technology.Results show that double triangle wave modulation technology exhibits better performance than double sine wave modulation technology in suppressing backscattering error by carrier suppression.In addition,the modulation frequency and modulation index of double modulation will affect the linear region of demodulation signal,and the optimized modulation frequencies are obtained and verified.Analysis shows that there is a linear work area for double triangle wave modulation technology in RFOG...