Study On Underwater Shock Wave Pressure Sensor Based On Fiber Optic F-P Cavity

With the development and popularization of optical fiber sensing technology,a variety of fiber optic sensors have been developed.Among them,fiber optic pressure sensors are widely used in various measurement fields such as biology,medicine,and industry.Fiber optic pressure sensors have many remarkable features.Advantages,such as:signal transmission through optical fiber,attenuation is very weak,can be applied to ultra-long-distance transmission;secondly,the fiber itself has anti-electromagnetic interference,high temperature resistance,chemical corrosion resistance,and can work normally under various harsh conditions.Finally,the fiber optic pressure sensor is small in size,fast in response,has a very high space-time resolution,can meet various measurement needs,and the fiber cost is extremely low,which is very suitable for large-scale manufacturing and one-time measurement.In this paper,the pressure sensor of underwater shock wave generated by extracorporeal shock wave lithotripter is studied.The full quartz fiber Fabry Perot pressure sensor is studied.This paper first introduces the basic working principle and demodulation mechanism of fiber optic sensors,and analyzes two basic types of fiber optic sensors.The basic composition of fiber Fabry Perot sensor and the research status at home and abroad are introduced.The typical structure and interference principle of fiber Fabry Perot sensor are introduced.The relationship between the fineness and reflectivity of Fabry Perot interferometer is given.Several types of fiber Fabry Perot sensors are introduced.The mainstream demodulation method introduces the multiplex demodulation method of fiber Fabry Perot sensor-three-wavelength demodulation.The design and manufacture of the all-quartz diaphragm fiber Fabry Perot pressure sensor are mainly studied.The three-beam interference output expression of the sensor is given.The reflectivity,FP cavity length and diaphragm thickness of the three end faces of the sensor are obtained by curve fitting.The problem of the cavity loss of the extrinsic FP cavity sensor is studied.The relationship between the interference fringe visibility of the sensor and the cavity length is considered in consideration of the intracavity loss.The cutting and welding problems of the capillary quartz tube are introduced in detail.The cavity length cutting control method of the FP cavity sensor is given.The interference and elimination means of the reflected light on the outer surface of the sensor diaphragm are discussed.The fabrication of the FP cavity sensor sensitive diaphragm is discussed.The processing technology was studied.Finally,based on the piston pressure calibration machine,the sensor was statically calibrated,and the underwater shock wave test experiment system was established.The electromagnetic extracorporeal shock wave lithotripter was used as the pressure source,and the underwater shock wave was measured.Experiments show that the sensor sensitivity reaches 3.42 DEG MPa^-1,the linearity is 0.9975,the forward repeatability of the sensor is 0.0341%,the repeatability is 0.0331%,and the dynamic response time of the sensor does not exceed 0.62us,which satisfies the test requirements of underwater shock wave.The sensor's tolerance test shows that the sensing technology used in the experiment can withstand the penetration of 18 shock waves with a peak pressure of 60 MPa before rupture.