Study On Sensing Signal Demodulation System For Fiber Bragg Grating Based On LabVIEW

Fiber Bragg Grating(FBG) sensor uses FBG as sensing elements. It has many excellent merits which other sensors do not have, such as small volume, light weight, resistance of the interference of electromagnetic, high sensitivity, electric insulation, and easy to form sensor networks. FBG sensor could measure temperature, strain and other physical quantities, so it is widely used in many fields.A demodulation system of fiber F-P tunable filter is designed based on LabVIEW in this paper. The demodulation system is simple, low cost, convenient data transmission, fast demodulating speed. The primary content includes:The coupled-mode theory in fiber is expatiated, the Bragg formula is deduced. The formula of the FBG sensor is demonstrated based on the strain sensing principle of the FBG sensor in the paper. The performance and working principle of main devices in this demodulation system are analyzed. The module circuits of the system are designed, such as, photoelectric conversion circuit, amplified circuit, shaping circuit and capturing signal circuit based on PIC16F877A. A mathematical model is proposed to calculate the sensing FBG center wavelength. In this mathematical model, the time intervals between the two rising edges of output signals are detected, then the changes of the sensing FBG center wavelength can be calculated. This measurement solves the instability problem of simultaneously displaying driving voltage signals and output signals in the traditional method. Signal processing program is designed and simulated in the LabVIEW. The experimental results are consistent with theoretical analysis, which conform the feasibility of the demodulation system.