Design On FBG Wavelength Demodulation System Based On A Tunable F-P Filter

Fiber Bragg Grating(FBG) are new fiber sensors.They have some special characters,such as immunity from interference,thermostability,corrosion resistance and far transmission range.They can also keep away from light intensity fluctuation and fiber bending loss due to the modulation by wavelength as sensing signals.FBG sensors are dramatically better than traditional ones on real time monitoring systems. They can measure parameters like stress,temperature and strain,so FBG sensors have widely applied in the field of structure health monitoring,aerospace and petrochemical industry.The difficulty of this technology in practical project is how to demodulate the wavelength.The demodulation system with high accuracy,low cost is be of great signifiance.This thesis mainly study on FBG wavelength demodulation system based on a tunable fabry-perot filter.First of all,the paper presents the development and application of FBG sensors.Both FBG sensor theory and F-P theory are introduced too.Subsequently,for solving the inherent defect like hysteresis and creep of F-P filter, a modified series real time correction system is designed. It is used for correcting the function beween voltage and wavelength.Signal distortion is made by noise.The exact peak point can ascertain the moment.Lowpass filtering technology and curve fitting technology are used for digital signal processing.They can find the point of peak,so the demodulation accuracy is improved availably.