Distributed Vibration Sensor Based On OFDR And Its Application In Wind Power Monitoring

Distributed optical fiber sensing technology has the advantages of anti-electromagnetic interference,corrosion resistance,light weight,small volume,etc,which makes it have a broad application prospect in aerospace,petrochemical,electronic power,civil engineering and other fields.The optical frequency domain reflectometry(OFDR)technology analyzes the backscattering signal of optical fiber in frequency domain through coherent detection,which has very high resolution and ultra-long sensing distance,and has become one of the research hotspots of distributed optical fiber sensing technology.However,the further development of OFDR system performance is affected by the phase noise caused by the tuning nonlinearity and the modulation depth parameter of demodulation algorithm.In this paper,a high precision and high spatial resolution distributed optical fiber sensing method based on phase sensitive OFDR technology is studied and applied to the vibration signal monitoring of wind power gears.The main works are as follows:(1)The concepts of distributed optical fiber sensing and OFDR system are introduced.A simulation experiment system of distributed optical fiber sensing based on OFDR is built,and the nonlinear tuning of light source in OFDR system is theoretically analyzed and simulated.(2)Aiming at the tuning nonlinearity of laser source in OFDR system,a nonlinear compensation algorithm based on PRA is proposed.In this method,the nonlinear phase of the light source is first expressed by the polynomial phase function,then the coefficients of the polynomial phase function are estimated,and finally the nonlinear phase is eliminated by combining with the matched Fourier transform.The simulation results confirm that the spatial resolution of the reflection point measurement signal can be improved after compensation,and the spatial resolution reaches 0.5m at the sensing distance of 26.8km.(3)A distributed strain fiber sensing method with high spatial resolution based on phase-sensitive OFDR is studied.By analyzing the direct demodulation strain information of the phase change of Rayleigh backscattered light,the weaker stress change is measured.The improved demodulation algorithm based on ARC-DSM eliminates the influence of modulation depth and greatly improves the understanding of modulation effect.The simulation results show that the static strain resolution of the system can reach 0.1 με and the spatial resolution can reach 0.1m within the 300 m range(4)A phase sensitive OFDR monitoring and simulation system for wind turbine was established based on MATLAB platform and the analysis of gear vibration signal of wind turbine.The nonlinear compensation method and the improved demodulation algorithm proposed in this paper are applied to the sensor system to realize the demodulation of the vibration signals of the wind turbine gears with different frequencies and amplitudes,and the validity of the method is verified...