In this paper

we propose to use two Fabry-Perot（F-P）cavities as the double-edged filters to achieve the wavelength demodulation in Fiber Bragg Grating（FBG）sensor system.Since the reflected FBG signal through the two filters have different spectral characteristics and light intensities

the ratio of two intensities can be used to determine the wavelength of the measured light.Through the calculation and simulation

the system can realize the demodulation of the sensing FBG signal.The simulation results show that the system is more accurate with ideal linearity.Moreover

the system does not have mechanical movement at the time of demodulation

which means the measurement speed is faster and the running speed is more stable.