Research On Key Technologies Of Fiber Grating Demodulation System

Compared with traditional airborne antennas,the wing integrated conformal antenna has better aerodynamic and electrical performance.However,when the wing structure is deformed,the antenna performance will deteriorate.Therefore,it is necessary to monitor the deformation of the wing in real time for electrical performance.Performance compensation.It is planned to use the contact measurement scheme to embed the fiber grating sensor in the wing structure to monitor the temperature,strain and other parameters for a long time.However,the existing fiber grating sensor demodulation products cannot be directly applied to the project,so the demodulation range needs to be developed A fiber grating sensor demodulation system with large,large number of channels,and convenient function expansionBased on the theory of fiber grating sensing,this paper deeply researches related technologies such as demodulation methods,peak-finding algorithm addressing schemes,combined with engineering practice,analyzes various factors that affect the accuracy and stability of demodulation,and determines the parameters of the system;The demodulation system design based on the tunable Fabry-Perot filtering demodulation method combined with the Gaussian fitting peak finding algorithm and the relative position wavelength addressing scheme;the software and hardware modules of the demodulation system are developed,including the system optical circuit,hardware circuit,and control Programs,etc.;system design is optimized to reduce the influence of noise,system nonlinearity and other interference factors on demodulation accuracy;system experiment platform is constructed,fiber grating temperature sensing test experiment is carried out,and the measured value of standard demodulator is compared By comparison,the measurement accuracy,stability and other performance indicators of the demodulation system are verified,and the experiment is analyzed and researched.In the specific implementation of the scheme,in order to reduce the error fluctuation caused by the unstable power of the light source,we selected a tunable Fabry-Perot filter demodulation method that is not affected by the light intensity.In the optical path system,we selected a relatively flat broadband light source and For high-precision F-P filters,we use Gaussian fitting peak-finding algorithm for waveform data processing in the demodulation program,so that the wavelength demodulation result has nothing to do with the waveform peak;to weaken the tuning response delay,hysteresis effect,and Due to the influence of temperature drift characteristics,optical reflection instability and other characteristics,we use etalon as the reference optical path in the optical path system,and demodulate and correct through the relative position addressing scheme.We use the lower frequency sawtooth voltage drive in the circuit F-P filter;in order to reduce the influence of noise and error interference,we use a stable output voltage chip with high stability for the photoelectric signal conversion,signal conditioning,AD sampling and other modules in the hardware circuit,and the voltage input and output are connected There are filter capacitors.We have added reference voltage calibration to the FP filter drive circuit and AD sampling circuit.In addition,according to the characteristics of the fiber grating reflection spectrum,we use a high-speed AD sampling circuit to synchronously oversample the spectral waveforms of multiple channels,and the spectral waveforms The data is processed by time-frequency analysis,filtering,floating threshold selection,peak finding fitting,addressing calibration,etc.to ensure the measurement accuracy and stability of the system.The main indicators of this system after experimental testing are as follows: the number of channels is 8,the data transmission rate is about 93.33 Mbps,the wavelength resolution is less than 1pm,the demodulation range is 1527~1565nm,the wavelength variation error is less than 4pm,and the temperature variation measurement error is less than 0.4?,the measurement error of strain change is less than 4??,comparing the main design indicators of the system,it can be concluded that the measurement accuracy and stability of the demodulation system designed in this paper meet the design requirements.