Research On Multi-parameter Sensing Method In High Temperature Environment Based On Fabry-Perot Microcavity With Sapphire Fiber

Accurate measurement of physical parameters such as temperature,refractive index,and pressure in high-temperature environments is an important research content in aerospace and other fields.The Fabry-Perot microcavity sensor based on sapphire fiber has the advantages of high temperature resistance,high accuracy,small size and anti-electromagnetic interference,which is suitable for multi-parameter monitoring in high temperature environments.This paper carried out the research on the multi-parameter measurement method of Fabry-Perot microcavity based on sapphire fiber in high temperature environment,proposed the dual-sapphire-fiber-based self-filtering high-temperature sensing mechanism.Studied the sapphire composite Fabry-Perot dual-cavity and MEMS silicon-based composite Fabry-Perot dual-cavity and realized temperature-refractive index and temperature-atmospheric pressure dual-parameter sensing in high temperature environments.The main work of this paper includes:1.The influencing factors of the fringe visibility of Fabry-Perot microcavity sensing spectral interference signals based on sapphire fiber are studied.A dual-sapphire-fiber-based self-filtering Fabry-Perot microcavity high temperature sensing mechanism was developed and analyzed.Its beam coupling model is constructed.The dual-sapphire-fiber realizes dual-channel split transmission of input and output optical paths under high temperature environment.The input optical path channel is responsible for transmitting the light source to the sensitive Fabry-Perot microcavity.During the transmission process,the background reflected light introduced by the heterogeneous fiber fusion splice and the sapphire fiber end face is cut off by the end face of the input optical channeland does not participate in the superposition of the Fabry-Perot microcavity interference signal and self-filtering is realized on the optical path structure.The background reflected light received by the output optical path is greatly reduced and the visibility of interference signal fringes is significantly improved.The temperature experiment of 100～1080℃proves that the visibility of interference spectrum fringe of self-filtering sensor is above 43.96%and the temperature measurement resolution of 0.22℃and temperature measurement stability of 0.25℃are realized.2.A temperature-refractive index dual-parameter sensing method based on sapphire fiber and sapphire composite Fabry-Perot dual-cavity under high temperature environment is proposed.The three-layer structure of sapphire wafer-sapphire C-ring-sapphire reflector is used to form a sapphire wafer temperature-sensitive microcavity and an open-cavity refractive index-sensitive microcavity which can be used for dual-parameter measurement of temperature and refractive index.Achieve high precision measurement of temperature up to 1080℃and refractive index.The open-cavity microcavity is used to realize atmospheric pressure measurement in a closed environment,expand the sensing application field to high temperature-pressure dual-parameter sensing and realize pressure measurement sensitivity 9.225×10^-2～6.101×10^-1nm/kPa in the pressure range of 10～280kPa.3.The principle of the peak tracking demodulation method and the Fourier frequency domain demodulation method suitable for interference spectrum demodulation are studied,which lays the theoretical foundation for the sapphire fiber Fabry-Perot microcavity sensor to achieve large dynamic range and high-resolution physical parameter measurement.The temperature-pressure dual-parameter sensing method based on sapphire fiber and MEMS silicon-based composite Fabry-Perot dual-cavity under high temperature environment is studied.The sapphire fiber waveguide is used as the optical signal transmission and collection waveguide,and the MEMS silicon-based composite Fabry-Perot dual-cavity is the temperature-pressure sensitive unit.A sapphire fiber MEMS silicon-based composite Fabry-Perot dual-cavity sensor is constructed.Fourier frequency domain demodulation method combined with the peak tracking demodulation method of contour recognition reconstruction is used to realize the separate,extract and demodulate the composite Fabry-Perot dual-cavity interference spectrum signal in the frequency domain and wavelength domain under high crosstalk conditions.The high-sensitivity monitoring performance of the sensor with dual-parameters of temperature up to 800℃and pressure range of 20～280kPa is realized.The temperature measurement sensitivity is192.9nm/℃and the pressure measurement sensitivity is 7.93nm/kPa.