Fiber Optic FBG-FPI Sensor Dual Parameters Research On Demodulation Technology

Fiber optic sensors possess anti-electromagnetic interference characteristics,which enable medical monitoring in strong electromagnetic environments such as nuclear magnetic resonance and CT scans.Additionally,their small size,high accuracy,and biocompatibility make them suitable for implantable medical monitoring.The composite structure of fiber optic gratings and Fabry-Perot cavities can achieve synchronized monitoring of pressure and temperature,which,when applied to biomedical research,provides vital physiological information and diagnostic basis for diseases.This article focuses on the following research work:This article focuses on the composite fiber optic sensor,which combines Fabry-Perot interferometry(FPI)and fiber Bragg grating(FBG)technology.The effects of FPI cavity length on the output pressure signal and the effects of FBG central wavelength on the output temperature signal are analyzed.Furthermore,an analysis of the pressure-temperature cross-sensitivity of the sensor structure is conducted.A demodulation system for a FBG-FPI composite sensor is built,which includes optical path and circuit design,as well as algorithm implementation.The optical path involves building the demodulation path and spectral analyzer driver,while the circuit design includes power conversion,AD sampling,and serial communication circuits.The demodulation algorithm design includes spectrum calibration and solving cavity length and central wavelength using cross-correlation and centroid methods,with raised cosine filtering applied to the results.Simulation is performed using C++ language,and an interactive interface is designed to achieve the synchronized dynamic display of the FPI cavity length and FBG central wavelength.Based on the demodulation system,a temperature-pressure composite test platform is established to test the sensor in the range of 22-43℃ and 750-900 mmHg,determining the main performance indicators of the sensor.The pressure sensitivity is superior to 2.3nm/mmHg,with linearity not less than 0.999,and the temperature sensitivity is superior to 10pm/℃,with linearity not less than 0.992.To address the pressure-temperature cross-sensitivity of the sensor,a compensation algorithm for Fabry-Perot cavity length is designed,enabling accurate measurement of pressure and temperature.