Research On Fiber Bragg Grating Sensor Demodulation System

Comparing with conventional electrical sensors,fiber grating sensor has many unique advantages.Such as it is distributed sensing and wavelength coding in design.It's also easy to install and embed inside the object because of its light structure.What's more,it doesn't use power,which makes it use low power consumption and good anti-jamming ability.All of these make it's widely used in oil industry,aerospace material structure health monitoring,bridge and dam status monitoring.Fiber grating demodulation is used to measure fiber Bragg sensor's wavelength.Therefore,demodulation system is an important part in the whole fiber sensor system.A set of fiber Bragg grating sensor demodulation system is developed based on the related research.The main research work shows as below.1.The paper studies the sensing mechanism of fiber grating sensor,designs the demodulation system's technology scheme and key parameter based on fiber fabry-perot tunable filter after the analysis of typical demodulation technology.2.According to demodulation system's technical requirements,a set of data acquisition and drive control circuit based on FPGA is designed,which includes filter drive circuit,photoelectric signal conversion circuit,A/D acquisition circuit and Ethernet communication interface circuit.In addition,circuit's drive control is complete by the FPGA programming.3.Because of the repetitive and nonlinear error caused by hysteresis,creep and cavity length drift during filter scanning the wavelength,a complete filter calibration model is established.In hardware,temperature control system and the reference grating is added.In software,generalized regression neural network is used to fit the drive characteristic curve.4.According to the features of fiber Bragg grating spectrum,A peak-searching model is designed based on the study of typical peak-searching algorithm,What's more,the influence to peak-searching effect caused by spectral signal SNR,threshold and algorithm is studied.5.The system experimental platform is built based on system scheme's design and key technology's research.According to the system's temperature demodulation test experiment,system stability and repeatability error is analyzed by comparing with MOI demodulation.