Development Of Optical Wedge Demodulation System For F-P Fiber-optic Sensor

Fabry-Perot(F-P)fiber-optic sensors are sensors working based on the principle of light interference.For their advantages of high accuracy,non-contact,tiny size,high resolution,anti-electromagnetic interference,etc.,F-P fiber-optic sensors have found many applications in automotive industry,aviation,aerospace,medical,and so on.Aiming at the demodulation of F-P fiber-optic sensors,this paper designs a system of optical wedge demodulation based on the principle of non-scanning correlation demodulation.This system adopts the combined structure of fiber collimator,Powell prism and optical wedge to achieve absolute measurement of cavity length of F-P fiber-optic sensors.Main contents include the following aspects:The article starts with the interference principle of F-P fiber-optic sensors and analyzes their light interference.Based on the principle F-P fiber-optic sensors,the advantages and disadvantages of several current demodulation schemes are analyzed and compared,and the scheme used in this optical wedge demodulation system is determined: the non-scanning correlation demodulation method.According to the demodulation scheme,the corresponding mathematical model is established.In order to verify the correctness of the mathematical model and the feasibility of the demodulation scheme,Gaussian light source was selected to simulate the relevant interference signals output by the demodulation system.Through experiments,it can be seen that the simulation results and the preset F-P fiber-optic sensors has the same cavity length,which verifies the correctness of the mathematical model and the feasibility of the demodulation system.Then,according to the determined demodulation scheme,the entire demodulation system is divided into two parts: optical path and circuit.In the optical path,the selection of the light source,the selection of each optical device,how to select the parameters of the optical device and the construction of the optical path are discussed.The circuit design includes five circuit modules: power supply,CCD driver,FPGA,A/D conversion,and serial communication module.The power module provides the voltage required by each circuit module for the entire circuit.FPGA,as the core controller of the circuit,drives the CCD,AD conversion,and serial port.The parameters of each chip in the circuit are explained and the specific model of the chip is determined.Finally,an experimental platform was set up according to the demodulation scheme.By designing a reasonable correlation interference signal peak algorithm,the pixel position corresponding to the peak is determined.The demodulation system was calibrated according to the standard cavity-length F-P fiber-optic sensor,and the linear relationship between the cavity length of the F-P fiber optic sensor and the peak position of the relevant interference signal was obtained.The demodulation of the absolute cavity length of the F-P fiber-optic sensor was realized.After experimental verification,it can be concluded that the measurement error of the system in the range of cavity length from 60?m to 100?m did not exceed 0.025%.