Research On Ultra-high-speed Demodulation Method Of Fabry-perot Sensors Based On Dispersion

Fabry Perot(F-P)interferometric sensors have the advantages of high resolution,high sensitivity,high temperature resistance,corrosion resistance,and electromagnetic interference resistance.Compared with the traditional fiber Bragg grating sensor,F-P sensors are smaller in size(?m)and can achieve more accurate point measurement and is particularly suitable for applications where sensor volume requirements are small and integration requirements are high,such as root stress distribution of narrow gears in mechanical fault monitoring or hole edge stress measurement of engine blades.However,in these dynamic detection scenarios,the F-P sensing array demodulation method is often required to have a higher demodulation rate,and the existing intensity demodulation method has low demodulation precision,a small range,and cannot be cascaded.The phase demodulation method is limited by the scanning speed of the scanning device,and it is difficult to achieve high-speed spectral acquisition.Based on the dispersion effect,this paper maps the spectral information of F-P to the time domain,and uses the wavelength selection characteristic of optical comb filter to restore time domain information to spectrum domain.The system combines optical time domain reflection(OTDR)technology to achieve ultra-high-speed acquisition of F-P spectral information.Then,the ultra-high-speed demodulation of the F-P sensor array is realized.The main research contents are as follows:(1)Study on the ultra-high-speed spectral-domain to time-domain mapping method based on dispersion.The interference principle inside the F-P and its sensing mechanism are derived,and the reflection spectrum indifferent case are simulated.The spectral aliasing process of F-P in series is analyzed and simulated.The spectral-domain to time-domain mapping model is established.The key technology of high-speed OTDR demodulation and the dispersion effect of optical fiber are studied to realize ultra-high-speed wavelength-domain to time-domain mapping.The characteristics of optical comb filter are analyzed,time-domain to spectral-domain reduction is implemented based on it.(2)Design and implement a dispersion-based F-P sensor ultra-high-speed demodulation system.Select and test the core components of the system.Analyze the demodulation process of the proposed method.Build and design the three-multiplexing method(time division multiplexing,frequency division multiplexing,time division + frequency division hybrid multiplexing)that can be realized in the proposed method.Research the position information and spectral information reduction of each F-P in the cascaded F-P sensors.Study the high-precision F-P cavity length demodulation algorithm.Based on the existing minimum mean square error method,an F-P cavity length demodulation algorithm based on peak to peak method + minimum mean square error + dichotomy is proposed.Comparing with existing algorithms,the verification algorithm improves the cavity length demodulation accuracy and demodulation speed.(3)Experimental test and application of ultra-high-speed demodulation method for F-P sensors based on dispersion.F-P sensor arrays are fabricated,static stability experiments and strain experiments are designed in different multiplexing cases to verify system stability and demodulation accuracy.The system is applied to the dynamically rotating mechanical gear to measure the strain at each point of the gear tooth during the meshing process of the gear,and to verify the system's ability to perform high-speed point measurement.