| High temperature pressure sensors have huge potential demands in aerospace,energy development,industrial smelting and other fields.Compared with traditional electrical sensors,optical fiber high temperature pressure sensors have many advantages such as high temperature resistance,corrosion resistance,anti-electromagnetic interference,and multiparameter measurement.Therefore,the research and development of optical fiber high temperature pressure sensor has important practical significance and application prospects.This paper takes the simultaneous monitoring of the internal temperature and pressure of the engine as the research goal,and uses the fiber Fabry-Perot(F-P)interferometric sensing structure as the research basis,combining photonic crystal fiber,thermally regenerated fiber Bragg gratings,hollow silica tube and other materials,a variety of optical fiber temperature and pressure sensing structures have been prepared and tested in experiments.The specific research contents are as follows:Based on the theory of fiber composite dual cavity sensing,we use hollow-core fiber to cascade part of grapefruit photonic crystal fiber,polarization-maintaining photonic crystal fiber,and hollow-core fiber to prepare three fiber microcavity sensors and conduct experimental tests.The air cavity and silica cavity of the three sensors have different temperature and pressure sensitivities,and the temperature and pressure values of the environment can be obtained through a dual-parameter matrix.This type of sensor is widely used,but it has problems such as large pressure monitoring error and low sensitivity under high temperature and pressure environment.Based on the fiber composite dual cavity sensing structure,we fabricated fiber optic high temperature pressure sensor based on Antiresonant mechanism by controlling the length of the air cavity.Experiments have tested that the sensor has a temperature sensitivity of 0.713 nm/? and a pressure sensitivity of4.033?0.921 nm/MPa in an environment of 25?1000 ? and 0?1 MPa.Compared with other interference sensors,the sensor is simple to manufacture,only one air chamber is needed to realize the dual-parameter measurement of temperature and pressure.The temperature and pressure sensitivity are higher than other sensors,which have certain application prospects in the field of optical fiber sensing.Taking advantage of the insensitivity of fiber Bragg grating(FBG)to pressure,we cascade the FBG and Fabry-Perot interferometer(FPI)to form an optical fiber hightemperature pressure sensor and design the protective package.In the experiment,the FBG is thermally annealed to form thermally regenerated fiber Bragg grating(RFBG)suitable for high temperature environment,and the temperature is calibrated by RFBG to determine the pressure sensitivity of the corresponding FPI at the temperature point,so as to realize the differentiated measurement of temperature and pressure.In order to improve the pressure sensitivity of the FPI sensor,we fabricated a parallel FPIs sensing structure using a hollow silica tube and optical fiber nested fusion method.Based on the Vernier effect,our sensor has a pressure sensitivity of 63.67?21.22 nm/MPa at25-600 ?,which is about 15 times the pressure sensitivity of a single FPI.In addition,by adjusting the position of the fusion splice point of the nested structure and increasing the collimation of the multi-mode fiber to the beam,we have reduced the temperature cross sensitivity of the sensor and improved the interference fringe contrast of the reflection spectrum.The parallel nesting structure is simple to manufacture and has a significant sensitivity amplification effect,and is suitable for the preparation of sensors based on the Vernier effect. |
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