Research On Fiber Interferometric Triaxial Vector Vibration Sensing And Signal Demodulation System

Optical fiber triaxial vector vibration sensor has the advantages of high measurement accuracy,easy to network,strong anti-interference ability and so on.It has a broad application prospect in aerospace,bridge water conservancy engineering,safety production monitoring and other related technical fields.Based on the practical application,this paper focuses on the key technologies of optical fiber triaxial vector vibration sensing and demodulation system.The research of this subject has important scientific significance and application value.To solve the problem of low sensitivity of frequently-used fiber vector vibration sensors,on the basis of after studying the cantilever beam structure the intensity modulation type fiber optic sensor,wavelength modulation type fiber Bragg grating sensor and various interference phase modulation type structure on the sensitivity performance influence,designing the interferometric fiber membrane chip M-Z vibration sensor,and the design of the sensor are theoretical analysis and experimental research.The results show that the sensitivity of the designed sensor can reach 6969.5rad/g and the linearity is 99.8%.When the error range of sensitivity is ±5%,the frequency range is 10Hz-240 Hz.In order to realize high precision demodulation of signal in engineering application,based on the research of phase generated carrier demodulation technology and 3×3 coupler demodulation technology,An improved 3×3 coupler demodulation algorithm is designed to solve the problems of incomplete dc removal and the output of the automatic gain control is not proportional to that of the core control.The demodulation algorithm of the improved 3×3 coupler is analyzed by adjusting the amplification gain of the de-dc operation and replacing the original automatic gain control with amplitude normalization.The analysis results show that the linear correlation coefficient between the demodulation output and the input signal can reach 99.99%,especially when the phase deviation is less than 4°,the correlation number of the improved demodulation algorithm is very close to 1,that is,the waveform is demodulated almost without distortion,and the demodulation result basically recovers the phase information.Therefore,the improved demodulation algorithm of 3×3 coupler achieves the purpose of demodulating signals with high precision and improves the demodulation accuracy of the system.