Research And Design Of Signal Demodulation System For Fiber Optic Fabry-Perot Sensor

Along with the increasing complexity of industrial environment and the development of artificial intelligence,the application range of sensors is more and more extensive.Among them,optical fiber Fabry-Perot(F-P)sensors have the advantages of small size,stable performance,high pressure resistance,corrosion resistance,strong electromagnetic interference resistance and high sensitivity.Therefore,it has been widely used in measurement of temperature,stress,pressure and curvature.Demodulation technology is very important for fiber F-P sensing systems,and research on optical fiber F-P sensor signal demodulation systems has received extensive attention.Most of the traditional demodulation systems use spectrum analyzer.The spectrum analyzer is bulky and expensive,which is not conducive to the practical use of the optical fiber F-P sensor.Therefore,a small-volume,low-cost demodulation system has great significance for the popularization of optical fiber F-P sensor.This thesis designs a spectral measurement scheme based on scanning laser,which has wavelength calibration capability.The spectral measurement and spectral feature extraction were completed by Labview software to realize the wavelength demodulation of the interference valley in the reflection spectrum of the optical fiber F-P sensor.The main research contents of this paper are as follows:(1)Based on the principle of multi-beam interference of F-P cavity and its sensing principle,the demodulation system of existing optical fiber F,-P sensor is investigated.Aiming at the shortcomings of traditional F-P sensor demodulation system,the F-P sensor demodulation method based on spectral measurement is optimized,and the demodulation principle of optical fiber F-P sensor based on scanning laser is theoretically analyzed.(2)The optical fiber F-P sensor signal demodulation system based on spectral measurement method is studied,including spectral measurement optical path module,spectral measurement control unit and Labview demodulation software.The spectral measurement was realized by the scanning filter method,and the optical fiber F-P etalon was introduced as the wavelength correction module.The spectral measurement control unit used the STM32 microcontroller,which consists of two parts:the hardware circuit and the control program.The spectral demodulation algorithm was further studied.The Labview software realized the synthesis spectrum,waveform display,automatic tracking and identification of interference valley wavelength and data storage and so on.(3)The key performance indicators of the designed demodulation system were verified.The peak detection error was 0.93%.The spectral measurement repeatability relative error was within 0.1%,and the interference valley detection accuracy relative error was less than 0.6%.The spectral refresh rate is 2.12s,and the maximum system demodulation error was 1%.The optical fiber F-P sensor signal demodulation system designed in this thesis can automatically take the corresponding wavelength value and intensity value of the interference valley to realize signal demodulation.The system has the advantages of small size,low cost,embedded orientation and low power consumption.It has potential development space in the application of optical fiber F-P sensor,which can promote the practical application of optical fiber F-P sensor detection system.