| With the advancement of fiber-optic sensing technology,fiber-optic sensors have been applied in fields such as aviation,industry,medicine and military,for measuring parameters such as temperature,pressure,and strain.The fiber-optic pressure sensor,in comparison to traditional pressure sensors,has become an important development direction in the field of pressure measurement due to the advantages of fast response,high sensitivity,small size and high resistance to electromagnetic interference.This article focuses on the research of the thin film fiber-optic Fabry-Perot pressure sensor based on shock wave pressure measurement.The main research content includes the following aspects:(1)The introduction and theoretical analysis of the fiber-optic Fabry-Perot sensor.Two typical structures of the fiber-optic Fabry-Perot sensors and the current status of domestic and international research are introduced.The multi-beam interference principle is demonstrated,and the reflection spectrum characteristics under different reflectivities are studied.The displacement vector between the upper and lower surfaces of the thin film and the change in optical phase are analyzed under pressure.(2)Design and simulation of the thin film fiber-optic Fabry-Perot sensors.According to the experimental requirements,a fiber-optic Fabry-Perot sensor with a gold-parylene-gold three-layer film structure is designed,with the gold film used as the reflective surface of the Fabry-Perot cavity to improve the reflectivity,and the parylene used as the cavity of the Fabry-Perot cavity to feel the external pressure.Finite element software is used to simulate the sensor,including the energy distribution of the electromagnetic field,the reflectivity of the sensor under the wave optics module,and the model force,resonant frequency,and deformation of the Fabry-Perot cavity under the structural mechanics module.The structural parameters of the sensor are optimized.(3)Comparison and verification of demodulation methods.The demodulation methods of fiber-optic Fabry-Perot sensors including phase demodulation and intensity demodulation are introduced,and their advantages and disadvantages are analyzed.Considering the characteristics of shock wave signals,the intensity demodulation method is selected to demodulate the sensor.A single-wavelength phase cosine intensity demodulation algorithm is proposed,and the feasibility of the algorithm is verified through theoretical analysis.(4)Packaging and testing of the thin film fiber-optic Fabry-Perot sensors.The static pressure test package and dynamic pressure test package of the sensor are completed.The static pressure calibration and test system of the sensor was designed and built,and experiments were conducted on the static characteristics of the sensor such as range,linearity and stability.The results show that the cavity length of the sensor changes 18.8 nm within the pressure measurement range of 60 MPa,which is basically consistent with the simulation results.The dynamic pressure test system of the sensor is designed and built,and a lamp-pumped YAG laser is used to ionize the alloy target to produce a small explosion.A thin film fibre-optic Fabry-Perot sensor was used to collect and measure the shock wave signal generated by the explosion.The fastest rise time of the measured shock wave signal was 96 ns and the maximum pressure was 7.87 MPa. |
