Research On Demodulation Technology Of FBG Based On Wedge Interference And Fast Fourier Transform

With the continuous development of optic fiber sensing technology,a variety of new optic fiber sensors have been developed.FBG,which has the advantage of small volume,light weight,anti-corrosion and anti-electromagnetic interference,is widely used in biology,medicine,civil engineering,machinery and other fields.Demodulation of optical signal is the key technology in optical fiber sensing.Interference demodulation is the method that dispose the reflected light of FBG and then analyze the interference fringe to get information of reflected light wavelength,so that we can calculate the wavelength shift and accomplish demodulation.In this paper,we use wedge interference and FFT to complete the demodulation.In theory,the reflected light signal of FBG which go through a collimating lens will beat down to the bevel of cleft tip,and then equidistant light and dark stripes will form at the right angles.The stripes will be received by CCD and processed via FFT to calculate the reflected light wavelength,so that we could achieve demodulation purpose.Then specific research work is described below:First of all,the development history and present situation of fiber grating at home and abroad were introduced,and the application of FBG sensing characteristics in sensing field was described.Secondly,the sensing characteristics of Bragg gratings were studied,several common demodulation techniques of FBG sensor were introduced,and the principles were analyzed in detail.Thirdly,the principle of wedge interference ware further studied,the method of data processing was described,and the software used was introduced in a brief way.Then,the characteristics of the main components were used and the connection circuit were introduced.Finally,build the light path for experiment and process the experimental data,analyze the advantage and disadvantage of this experimental system.