Based on an optical fiber Fabry-Perot（F-P） tunable filter

the methods to demodulate and calibrate the wavelength of FBG are discussed.According to the method of turning the voltage signal into rectangle pulse to demodulate and calibrate the wavelength

very high accuracy and stability are attained and a wavelength demodulator that has been used extensively in large-scale multipoint monitor engineering is designed.At last

an example of wavelength demodulation and calibration is given

and accuracy can reach to ±2 pm.