Research On High Temperature Sensing And Demodulation Technology Of Fiber Bragg Grating

Compared to the traditional resistance temperature sensor,the fiber Bragg grating(FBG)temperature sensor has advantages of anti-interference,quick response,etc.,which can be used for temperature measurement under various harsh environments,and has a high measurement accuracy.For the practical application of the FBG temperature sensor,the key point is how to accurately demodulate the wavelength drift information returned by the sensor and the durability of the sensor in high-temperature environments.In this paper,through the protective packaging of the pure silica FBG with polyimide coating fabricated by femtosecond laser,and based on the spectroscopic demodulation principle,a sensor and its demodulation system for high-temperature measurement were designed and implemented.The main research work is as follows:Firstly,the relationship between the reflected spectral signal and the temperature was deduced from the principle of FBG transmission and sensing.Several major demodulation methods were compared and analyzed,and the spectral demodulation method using the integrated InGaAs detector array was determined.Then,the FBG temperature sensor demodulation system was designed and established,which mainly included four parts: system structure design,device selection,circuit design,and software design.Mainly used the ASE light source and the small digital spectrometer device,and the circuit design part was based on the characteristics and performance requirements of the reflected spectrum signal,the A/D module was used to digitally convert the spectrum signal,and the signal processing was performed through the FPGA control circuit to achieve sensing demodulation,and completed the software development and debugging of each module accordingly.Finally,through the use of a stainless-steel capillary to package the sensor and complete the calibration test,built an experimental platform to verify the feasibility of the hardware circuit and software algorithm,completed the peak determination of the reflected spectrum signal,and then achieved temperature demodulation.Through experiments,the temperature sensitivity of the sensor is 14.45 pm/?,which can work stably under 800?,its maximum temperature resistance can reach about 1000?,the wavelength sensitivity of the demodulation system is 5 pm,17 KHz demodulation rate,the temperature resolution is less than 1?,and the maximum measurement error of temperature measurement is 0.071%,which has a small measurement error and high measurement stability to achieve the expected goal.