Research On Stability Of Light-duty FBG Demodulation System For Spacecraft In Temperature Changing Environment

The environment of the spacecraft is complex and changeable,so the reliability and long-term stability of the working state is an important guarantee for the safety of the operation.Monitor the structural health of the spacecraft through active detection of thermal parameters,which is conducive to the fault investigation and trend prediction,and it is of great significance to prolong its operational life.Fiber Bragg grating has many advantages,such as tolerance to corrosion,strong electromagnetic interference,high optical frequency selectivity,multi-channel and multi-point multiplexing.It has broad application prospects in aerospace.Based on the characteristics of temperature dynamic-changing in space environment,we put forward a FBG demodulation method with suppression of wave in wavelength scanning process.Experiments are conducted to study the development and changing system.The development of the system and experimental study in temperature changing environment are carried out.The finished works are as follows:1)A multi-channel FBG demodulation system with light-weight,high speed and high precision is developed including high power narrow band scanning light source based on tunable optical fiber F-P filter(FFP-TF),power type scanning control driving circuit and photoelectric detecting circuit and integrated multi-channel optical fiber sensing and reference links.The lightweight FBG demodulation system is build for spacecraft use with demodulation and scanning frequency up to 1.6kHz.The algorithm and software for the system are developed2)The method for suppressing wavelength scanning function was studied in temperature varying environment.Due to the effect on the repeatability deviation of FFP-TF's wavelength scanning nonlinear curve,we proposed a stable demodulation method based on optical fiber Michelson interferometer(AFMI),and the optical frequency subdivision in wavelength interval of F-P etalon is achieved.Then we analyzed temperature stability of AFMI and programmed the local optical frequency subdivision demodulation algorithm.Therefore,the increase of the wavelength results' fluctuation caused by the increasing wavelength scanning repeatability deviation is suppressed.3)Research on the performance in temperature changing environment of the FBG sensing system is carried out.The experiment result shows that,when temperature changes at average rate of 2.2?/min,the amplitude of fluctuation is ±28.5pm of former method without AFMI,and SD 8.6pm.However,the amplitude of fluctuation using AFMI is ±3.5pm,and SD 1.4pm.The results verify the effectiveness of the proposed method on the stability of the system.