Synchronous In-phase And Quadrature Demodulation Technique For Resonant Micro-Optic Gyro Scope

Resonant micro-optic gyroscope(RMOG)is a high accuracy rotation sensor based on the Sagnac effect,which is considered as a significant approach to realize miniaturization and integration.The basic principle is that frequency difference generated between the counterpropagating resonant beams is proportional to the angular rate of rotation.However,the frequency difference introduced by the Sagnac effect is too weak to be detected out on the laser central frequency.Thus,the signal detection technique is essential to a high-performance RMOG.In this dissertation,an in-phase and quadrature demodulation technique is introduced to improve the detection accuracy.The main researches include:(1)Use a PIN photodiode as the light intensity-current conversion element,design and develop a detection circuit with a trans-impedance amplifier(TIA)as its core.The noise caused by the detection circuit is greatly reduced by the low-noise,high-gain TIA module and the highpass filter.The test results show that the angle random walk(ARW)caused by the equivalent input noise of developed detection circuit is 0.046°/?h at 1m W detection optical power,which is closed to the calculated theoretical sensitivity of 0.043°/?h.The noise of the developed detection circuit can be almost ignored and the noise characteristic of the photodetector meets the detection accuracy requirements of the RMOG.(2)For the widely used phase modulation and synchronous demodulation technique in the RMOG,analyze the effects of the phase fluctuation on the demodulation output.Compared with the maximum slope of the optimal phase,the slope at the resonant point decreases by about 1.1%,6.1% and 22.1%,respectively,when the phase deviation is ?/25,?/10 and ?/5;Develop an inphase and quadrature demodulation technique and establish the RMOG system based on silica waveguide ring resonator.The demodulation curves with two demodulation techniques are tested and the phase fluctuation under laboratory temperature and varying temperature is measured.The test results show that the demodulation output is not affected by the phase fluctuation caused by the environmental temperature changes.With the application of in-phase and quadrature demodulation technique to the RMOG,the ARW of the gyro reaches 0.5°/?h.The bias stability of 9°/h based on Allan deviation is successfully demonstrated over a 1800 s timeframe,which is 1.6 times better than that obtained using the synchronous demodulation technique.(3)Preliminarily develop a time-division multiplexing RMOG system based on the optical switch in order to improve the reciprocity of the two back-propagating light in the resonator and effectively suppress the backscattering noise.The reciprocal modulation is applied to improve the reciprocity between the back-propagating light in the clockwise and counter-clockwise directions.Based on this,the optical switch is used to separate the signal light and the backscattered light in time domain by applying the time-division multiplexed signal to switch the light propagating in the clockwise and counter-clockwise directions,which can suppress the backscattered noise effectively;Analyze the influence of crosstalk and switching time on the backscattering noise and establish the time-division multiplexing RMOG,the experimental results verify the suppression on backscattering noise.