Research On Fiber Bragg Grating Temperature/pressure Sensing System

In this thesis,the research status and application of Fiber Bragg Grating sensor and Fiber Bragg Grating demodulation technology at home and abroad are summarized,and the coupling mode theory,temperature,pressure and strain sensing principle,various demodulation technology and temperature-strain cross sensitivity of Fiber Bragg Grating are studied deeply.In the research of fiber grating sensors: the sensor packages for different uses were summarized and analyzed,a liquid pressure sensor structure based on the thin-walled cylinder principle was designed.This structure uses the form of a semi-solid and semithrough hole.Double grating method was used to give temperature compensation to the pressure sensing grating.It is calculated that its pressure sensitivity is 38.04pm/MPa,which is about 12 times that of a bare grating,which improves the pressure sensitivity to a certain extent.The fatigue characteristics of the structure are simulated,and the fatigue life under different pressures is obtained,which proves that it can withstand a pressure of20 MPa.The relationship between the deformation and pressure of different materials is compared,which provides a basis for the selection of materials for this structure.The traditional I-shaped substrate-type temperature sensor was modeled and simulated,and the strain condition under pressure was analyzed.In order to reduce the impact of the strain,a strain isolation structure with an increased U-shaped groove was adopted.Simulation results prove that this structure can effectively isolate the strain and avoid the problem of cross-sensitivity of temperature and strain to some extent.In the research of demodulation systems: this thesis introduced and analyzed the principles of multiple modes of demodulation systems.According to the research content,a fiber grating demodulation system based on a tunable F-P filter was selected and designed,and the factors affecting the accuracy of the demodulation were analyzed.In order to calibrate the error caused by the temperature drift of the F-P etalon wavelength,a demodulation system using the acetylene gas cell for composite wavelength reference is proposed and designed.The principle of the composite wavelength reference is analyzed.The temperature sensor to be used in the experiment was calibrated,and the errors caused by different fitting methods were compared.The existing fiber grating demodulator and temperature sensor in the laboratory was evaluated,the temperature sensor was calibrated,and the repeatability and stability of the demodulator were tested and data analyzed.