Research Of The Fiber Bragg Grating Temperature Sensor Based On Dynamic F-P Cavity

This kind of sensor which is based on FBG have many advantages, it will be an important development direction of modern sensor technology. Through the demodulation of FBG wavelength, we can obtain the physical quantities, such as strain、temperature and so on.First, the coupled-mode theory of FBG is analyzed in detail at the beginning of the paper. Second, the strain sensing model and the temperature sensing model are discussed, also the sensitivity coefficients based on both of model are be deduced. What follows is a brief summary of the common demodulation methods about FBG. Meanwhile based on the tunable Fabry-Perot (F-P), it is proposed that a method of demodulation wavelength with the dynamic extrinsic F-P cavity. The reflected light of FBG is modulated by the F-P cavity which is constructed of a PZT. By the theoretical analysis, the modulated intensity varies with the length of F-P cavity as cosine-like. When PZT has a vibration driven by a sine voltage, the cosine-like signal will move, and a linear relationship between the signal curve shift and FBG wavelength offset is numerically simulated, it can be applied to FBG wavelength of demodulation. Utilizing a temperature measurement system made up of the F-P cavity and an FBG, the liquid temperature measurement is carried out in different temperature. Linear relationship between variation of the liquid temperature and the peak migration of cosine-like signal is proved when the temperature changed from35℃to70℃, and the linear fitting degree arrived as99.5%.Research proves that, the FBG temperature measuring system based on the dynamic F-P cavity is available. It is much more cheaper、simpler convenient to process signal, compared to the other temperature measurement system. With the depth research, it is expected to achieve higher accuracy and form sensor network for measuring multiple parameter at the same time, which has extensive applications in many areas.