Study On Temperature Characteristics Of Scanning Light Source Module And Demodulation Stabilization Method In Fiber Grating Demodulation

With the development of our country’s aerospace industry,the safety of spacecraft on orbit is highly valued by relevant researchers.Faced with complex and ever-changing space environment,structural health monitoring can grasp the working status of the spacecraft in real time,and realize early warning and failure protection of faults.It is of great significance for the spacecraft to successfully complete the scheduled tasks.Fiber Bragg Grating(FBG)sensors have the ability of measuring the force and thermal parameters,and are small in size,light in weight,anti-electromagnetic interference,and can be multiplexed,and are widely used in the aerospace field.The FBG sensing demodulation system based on tunable Fabry-Perot filter has a wide range of research and applications due to its wide tuning range and high demodulation accuracy.In this paper,the temperature characteristics of the scanning light source in the FBG sensing demodulation system are studied in view of the wide temperature range and fast changing speed of aerospace environment.The stabilization method of FBG sensing demodulation in variable temperature environment is proposed,and the algorithm design and experimental research are carried out..The main work done as follows:1)A high-power,narrow-line scanning light source module with FBG sensing system and its power-driven triangular wave circuit are designed.Temperature experiments are carried out to study the effect of temperature on the performance of the scanning light source driving circuit,output spectral flatness and wavelength tuning nonlinearity influences.2)The normalized flattening of the output spectrum of the scanning light source and the non-linear wavelength-suppressed suppression algorithm are studied.Aiming at the change of spectral flatness of scanning light source caused by variable temperature environment and further affecting the FP etalon and the FBG peak-finding stability,a planarization algorithm based on spectral baseline extraction and transformation is proposed.Aiming at the non-linear deterioration of wavelength tuning of scanning light source caused by variable temperature environment,FP etalon FBG demodulation stability,proposed FBG demodulation stabilization method based on multi-wavelength composite reference of FP etalon and HCN gas chamber.3)The stability of FBG sensing demodulation under multi-wavelength composite reference in variable temperature environment was investigated experimentally.Experimental results show that the FBG demodulation fluctuation is up to 56.8 pm and the corresponding standard deviation is 24.0 pm for FP etalon reference and single chamber wavelength correction at an average rate of 2.2 ℃ / min.For FP etalon and HCN gas Multi-wavelength composite reference,FBG demodulation fluctuations were suppressed within ± 11.7pm,the standard deviation of 4.6 pm,respectively,than the single-wavelength correction chamber increased by 4.9 times and 5.2 times.Therefore,the multi-wavelength composite reference and correction method can improve the demodulation stability of the FBG sensing system under the condition of temperature change.