Stydy On Demodulation Technology For Fiber Grating Geophone

Along with the development of geophone technology, the demand of frequency, dynamicrange, precision and resolution ration is increased. However the traditional geophone can notmeet the needs of seismic exploration. As one of the most potential and successful opticpassive device, the geophone that is made of FBG has particular advantages to traditionalexplorer such as: the sensing information is coded in wavelength, can construct sensingnetwork easily; higher accuracy; larger dynamic range; better immunity, which meet the newneeds in the seism probing field.The main obstacles of practical application of the fiber Bragg grating sensor is the sensingsignal demodulation, the fiber Bragg grating sensor demodulation method which wasdeveloped has several method, but the demodulation method which can applicate practicallyhas not so much and the price is expensive. Wavelength demodulation of fiber Bragg gratingdemodulation technique is a widely used technology. How to detect and process the tiny offsetof center wavelength, i.e. to demodulate the wavelength signal of FBG is the key to make FBGuse more widely. This text is based on tune matching grating filter demodulation technology,DSP and Labview are selected to collect, dispose and display demodulation signals, realizingto demodulate seism signals. Experiment indicates this demodulation system voltageresolution ration is0.732mV,wavelength resolution ration is5pm and dynamic range can reach70dB.The main contents of this paper include:1. FBG transmit theory model and the sensing theory are introduced; the demodulationmethods of FBG sensing applications are introduced, especially advantages and disadvantagesof several model demodulation methods of FBG are analyzed and contrasted.2. From the function of demodulation system and design request, we select tune matchinggrating filter method as the system demodulation scheme, the system of optical unit and thedesign method of electric circuits are given in detail; DSP and Labview are selected as the coreof late data processing, experiment system is designed finally. 3. The debug results of the main hardware and software of this system is presented. Andthrough the experimental testing and results analyzing, we demonstrate the feasibility andrationality of the devised scheme for this demodulation experimental system. Throughoptimizing the design of the hardware and software and increasing the number of the A/Dcollection point, the testing precision and resolution of the system can be more improved.