Development And Application Of Fiber Grating High Temperature Sensor And Fiber Microcavity Interferometer High Pressure Sensor

Today,with the development of industry and automation,sensor technology is particularly important.The advent of optical fiber sensors has made up for the obvious disadvantages of many electrical sensors,such as electromagnetic interference,environmental corrosion,difficulty in signal transmission and networking.The most striking advantage of optical fiber sensors is that they are cheap to make and do not produce electrical sparks.These characteristics make fiber optic sensors widely used in petrochemical,natural gas,bridge construction,aerospace and other fields.In this paper,the high temperature and high pressure measurement is realized by using fiber Bragg grating and fiber microcavity interferometer as sensors for the measurement needs of electromagnetic induction welding,oil and gas exploitation,aeroengine and other extreme environments.The main research contents of this paper include: the principle and demodulation method of high temperature and high pressure sensing of optical fiber,the development and testing of high temperature sensor of optical fiber grating,the development and testing of high pressure sensor of optical fiber microcavity interferometer,the preparation and testing of high temperature and high pressure integrated measurement optical fiber sensor.(1)For high temperature sensor,the high pressure sensor at home and abroad and the present research and development of integration of high temperature and high pressure sensor to carry out the research,summarizes and analyzes the advantages and shortcomings of all kinds of sensors,sure to satisfy the small volume,light weight,no spark of optical fiber Bragg grating and optical microcavity interferometer has a huge advantage in realize high temperature and high pressure measurement.Therefore,this paper mainly studies the high temperature and high pressure integrated sensing technology based on fiber Bragg grating and fiber microcavity interferometer.(2)High temperature resistant fiber Bragg gratings were prepared by femtosecond laser point-by-point method,and then fiber Bragg gratings high temperature sensors were developed,and the high temperature response characteristics were tested.The annealing and quenching processes of fiber Bragg grating are studied.At the same time,fiber Bragg grating shows excellent repeatability after annealing at high temperature.The developed FBG temperature sensor has a temperature sensitivity of 13.35 pm/? at 550 ? and a temperature response rate of208 ?/s.Finally,the fiber Bragg grating high temperature sensor is applied to the spot temperature monitoring in the electromagnetic induction welding process.(3)Fiber microcavity interferometer based on pure quartz film was prepared by using the methods of fiber end surface grinding,hollow glass tube fusion and precision cutting.On this basis,fiber microcavity interferometer high-pressure sensor was developed to achieve the measurement of 40 MPa(hydraulic pressure)at room temperature.The sensitivity to pressure measurement was improved by changing the thickness of the quartz film.The relationship between the pressure response of the sensor and the thickness of the film was studied.Pressure sensors exhibit good repeatability and their repeatability errors are negatively correlated with diaphragm thickness(the thinner the diaphragm thickness,the greater the repeatability errors).At the same time,the finite element analysis software Comsol was used for theoretical verification,and it was found that when the thickness reached 2.09 ?m,the pressure response of the sensor had a maximum sensitivity value.The theoretical simulation proved that the deformation of the quartz film resulted from the instantaneous thermal expansion and cold contraction during the processing and discharge process,resulting in the nonlinear response of the device under high voltage.Under the condition of both pressure sensitivity and linear fitting degree,the optimized design of quartz diaphragm thickness was 4.63 ?m and the optimal sensitivity of the pressure sensor for fiber microcavity interferometer was developed.The sensor sensitivity was:-1.436nm/MPa,and the linear fitting degree R squared value was: 0.991.(4)On the basis of studying the work of fiber grating high temperature sensor and fiber microcavity interferometer high pressure sensor respectively,the two structures are used to cascade and package,and then the high temperature and high pressure integrated fiber sensor is developed.The high temperature and high pressure integrated testing device was designed and built,and the high temperature and high pressure integrated fiber sensor was developed to achieve simultaneous measurement at 500 ? and 5 MPa(pressure).The test results show that the sensitivity of FBG temperature sensor increases by 0.000813 nm /? for each 1 MPa increase of gas pressure.The pressure sensitivity of the fiber microcavity interferometer decreases by0.000173 nm/MPa for each 1 ? increase in gas temperature.Temperature sensitivity:0.0141 nm/?,temperature measurement accuracy: 0.7% FS;Pressure sensitivity:-0.73 nm/MPa,pressure measurement accuracy: 1.37% FS.The fiber Bragg grating high temperature sensor and fiber microcavity interferometer high pressure sensor developed in this paper are expected to be widely used in the fields of aeroengine monitoring,oil and gas resources exploration and exploitation,deep-sea environment detection,advanced welding process monitoring and so on.