Research On High Precision Demodulation Method Of Fiber Bragg Grating Reflection Spectrum Based On Gas Cell

In recent years,the research of high-precision demodulation technology of fiber Bragg grating(FBG)sensor has become a hot spot.Because the change of FBG center wavelength directly reflects the change of external temperature,pressure and other physical quantities,how to accurately detect the FBG center wavelength value to obtain more accurate information in harsh environment is the research direction of much concern.FBG demodulation system based on tunable F-P filter has high demodulation accuracy under constant temperature condition,but the performance of demodulation system will decline under the condition of temperature change,which directly affects the high-precision demodulation of FBG center wavelength.Therefore,this paper proposes a calibration method based on F-P etalon and acetylene chamber composite wavelength as reference wavelength,which can achieve high-precision demodulation of fiber Bragg grating reflection spectrum under variable temperature conditions.The main work of this paper is as follows:Firstly,a large number of papers and literatures are consulted,the research status of high-precision demodulation technology at home and abroad is summarized,and the principle,advantages and disadvantages of the commonly used demodulation technology in recent years are studied and analyzed,which lays the foundation for the design of FBG reflection spectrum high-precision demodulation system.Secondly,based on the theoretical analysis and experimental analysis of the temperature stability of F-P etalon and acetylene gas chamber,a fiber Bragg grating demodulation experimental system with the composite wavelength of F-P etalon and acetylene gas chamber as the reference wavelength is designed and built.The acquisition and storage of spectral data are completed,which provides a hardware platform for the realization of high-precision demodulation algorithm of FBG reflection wavelength.Finally,a method to calibrate the FBG reflection wavelength is studied,which takes the gas absorption peak of C₂H₂gas chamber as the main wavelength reference and the sparse wavelength of F-P etalon as the auxiliary wavelength reference.Through comparative analysis,it is found that the composite reference wavelength has higher demodulation accuracy.The accurate peak search algorithm in the case of multi peak spectrum is studied,which provides an effective reference for the accuracy of wavelength calibration.