Study On Optical Fiber Pressure Sensor Based On Micro Ellipsoid Air Cavity

Fiber-optic Fabry-Perot sensor is an optical fiber sensor with small size,simple structure,low cost,high measurement accuracy and large detection range.It is easy to product,and has been widely used to measure physical quantities(strain,temperature,pressure),chemical quantities(humidity,pH,refractive index)and biomass in the fields of civil engineering and aerospace.We propose a fiber-optic Fabry-Perot pressure sensor based on micro-ellipsoidal air cavity,analyze the high-sensitivity fiber-optic pressure sensor model,propose a new pressure sensing scheme,and conduct an experimental test.Different from the existing Fabry-Perot pressure sensor fabrication technology,we use ordinary single-mode fiber and solid-core photonic crystal fiber fusion technology to form the air cavity.With low transmission loss and high contrast of the interference signal fringes,the all-quartz structure sensor has small temperature crosstalk and has a good application prospect in the field of pressure sensing.This paper presents a fiber Fabry-Perot pressure sensor based on micro-ellipsoidal air cavity structure.In this paper,the propagation of light in the air cavity is analyzed,and the variation law between the radius of curvature of the air cavity and the cavity length is studied under the condition of fixed volume.At the same time,we discuss the loss in the cavity under different shapes of the air cavity,the relationship between the shape change of the air cavity and the transmission loss is simulated by MATLAB software.Then the basic mathematical model of the pressure sensor was established.Based on the basic model,we use ANSYS software to simulate the mechanical properties of the pressure-sensitive film.The influence of the thickness of the pressure-sensitive film and the effective radius of the film on the central deflection of the film was discussed.Afterwards,we select the suitable cavity length,pressure-sensitive membrane thickness and other geometric parameters of the micro-ellipsoidal air cavity pressure sensor.According to the selected geometric parameters of the sensor and the actual structure of the sensor,we design the fabrication process steps of the Fabry-Perot pressure sensor.A sensor sample was made,and an experimental platform was also set up for sensor reflection spectrum test and pressure test.Wavelength tracking method is used to demodulate the pressure of the sensitive membrane.The demodulated data is fitted with the least squares method to obtain the mathematical model of pressure-wave trough wavelength.The linearity and sensitivity of the sensor are calibrated.