Research On Key Technologies Of Optical Fiber Temperature And Pressure Sensor Based On EFPI-FBG Composite Structure

In aviation propulsion systems,pressure and temperature changes caused by the instability of engine combustion have always been the focus of attention of testers and researchers.Commonly used temperature and pressure sensors often fail or damage under such complex environmental conditions.In recent years,due to many basic advantages of optical fiber testing technology itself,optical fiber sensors are considered by many researchers as the best solution to obtain measurement data in complex environments.Based on the application background of aero-engine propulsion system condition monitoring,this paper deeply studies the sensing principle of extrinsic Fabry-Perot interferometer and fiber Bragg grating,and analyzes the sensing mechanism of multiparameter sensing unit subject to external changes,A composite optical fiber sensor that can simultaneously measure pressure and temperature changes is designed and developed,and the performance test of the sensor sample is performed.Mainly completed the following work:First,this paper investigates the research progress of optical fiber pressure and temperature sensors,combs and summarizes the problems that need to be solved for different pressure and temperature sensing structures in the current research stage,and proposes the target selection of the optical fiber sensor structure design for this subject Type,that is,EFPI and FBG composite structure design.Combined with the target research direction,the basic principle of EFPI structure to realize pressure sensing was analyzed.Through the numerical simulation simulation results,the influence law of the sensitive diaphragm material and size on pressure sensing was obtained.Based on the analysis of basic principles,the sensing mechanism of the composite structure of EFPI and FBG is studied,and the expression form of the composite sensor signal of pressure and temperature is deduced.The spectrum shape of the composite sensor signal is obtained through simulation and simulation.The demodulation processing of experimental data provides a reference basis.According to the signal characteristics of the two sensor structures,the advantages and disadvantages of different demodulation algorithms for the cavity length of the Fabry-Perot cavity and the center wavelength of the Bragg grating are discussed,and the realization method of demodulation processing for the superimposed sensor signal is proposed.On the basis of theoretical and simulation research,the overall scheme of the optical fiber sensor and the large-scale pressure-sensitive diaphragm scheme are proposed,the combined structure of the EFPI and FBG composite sensing unit is designed,and the overall packaging method and steps of the sensor are designed.According to the design plan,the sample of the optical fiber temperature and pressure sensor was completed through the micro-electromechanical system(MEMS)processing and bonding technology.In order to verify the actual performance of the sensor,a set of sensor test system was built,and the sensor was repeatedly tested under the conditions of constant temperature changing pressure and constant pressure changing temperature,and the test results of fiber optic sensor samples were given.The experimental results show that the pressure sensitivity of the sensor sample reaches-0.727?m/MPa in the pressure range of 0-0.8MPa;the temperature sensitivity of the sensor sample is 0.009nm/°C in the temperature range of 50-200°C.In repeated pressure and temperature tests,the measurement results showed good linearity and repeatability.