Dynamic Demodulation System Based On Fiber Fabry-Perot Tunable Filter

Fiber Bragg Grating sensor has a lot of advantages such as outstanding electric insulation function, resisting electromagnetic interference and corrosion, high sensitivity, small volume, little weight and so on. It is widely used in construction, electric power and medical industry. It is a hot spot of fiber sensing field. As a sensing element, optical grating transforms information measured to the movement of reflected wavelength that is wavelength coding. As a result, it can not be influenced by the fluctuation of optical source power and system loss. The key use of FBG transducer is to detect the minute shift of Bragg reflecting wavelength precisely, that is to demodulate the coded wavelength signal. The thesis' subject is dynamic demodulation system based on fiber Fabry-Perot tunable filter.Firstly, the development of demodulation technology of FBG sensing signal in the world was introduced, and the features of several demodulation method were analyzed.Secondly, the coupled-mode theory of the light transmitting in fiber is expatiated and based on which the Bragg formula and reflectivity/transmission formula is deduced. We also analyzed the sensing principle of FBG strain sensor, press sensor and temperature sensor.The last but not the least, designed a kind of fiber Fabry-Perot tunable filter's dynamic demodulating system, demodulation of system work well during the experiment; Found the linear relational expression between wavelength going through filter and FBG tunable voltage by experiments, Designed and made experimental installation of strain by using overhanging beam. Then the Fiber Fabry-Perot Tunable Filter's demodulating system applied to this experimental installation of strain, and I gain significative experimental results, The experimental results indicated that this design scheme on fiber Fabry-Perot tunable filter demodulating system was feasible and had practicable value.