Research On Satellite Borne Optical Fiber Bragg Grating Sensing Demodulation System

Fiber Bragg grating(FBG)sensors is very suitable for structural health monitoring(SHM)of spacecraft,because of its small size,light weight,immune to electromagnetic,anti-corrosion,multiplexing capabilities and forming network.In this paper,research of FBG sensing demodulation system is carried out for the practical requirements of precision and large capacity in satellite borne application.Based on challenges brought by sapce environment,temperature-stable FBG sensing demodulation method using composite wavelength references is proposed.Satellite borne sensing demodulation system is developed,carrying out vacuum thermal cycling experimental study.The major work of the thesis as follows:1)Satellite borne multi-channel parallel FBG sensing demodulation system is developed.Based on the characteristics of the space environment,general design of the demodulation system is accomplished.Satellite borne high-power narrowband fast scanning light source,multi-channel parallel detection optical module and wavelength reference optical module are designed based on the general design.Intergrated tunable filter driving circuit,power circuit and photoelectric detection are also designed based on that.The demodulation system works well with the scanning wavelength covering 1525nm~1565nm,speed 400Hz。2)Research on wavelength calibration method of the sensing demodulation system is carried out.Based on the temperature-stable and fast demodulation requirements,proposed by satellite borne application,the temperature characteristics of F-P etalon and acetylene(C2H2)gas cell is analyzed.Temperature-stable FBG sensing demodulation method using composite wavelength references is proposed.The strongest spectral line of acetylene gas cell and different compensation caused by different interference order of F-P etalon are taken into consideration in the core method.Fast demodulation software is designed after analysis of the demodulation method.3)Research on temperature cycling and vacuum thermal performance of satellite borne FBG sensing system is carried out.The experimental result shows that the wavelength demodulates stablely and demodulated result varies in ±1.2 pm,and SD 0.39 pm at the range of 0℃~55℃.The effective temperature sensing demodulaiton of the demodulaiton system is achieved in high vacuum at the temperature range of-30℃~50℃.