Research On Multiplexing And Demodulation Of Distributed FBG Sensing Network Based On M Sequence

In recent years,with the development and application of Fiber Bragg grating sensing technology,modulation and demodulation of Fiber Bragg grating have become a research hotspot in related fields.So far the capacity of the fiber grating sensing array,the number of reusable FBG is limited.At the same time common demodulation method has some shortcomings.Because influenced by device delay,the stability of the light source and wavelength range of tunable light source,the number of sensing gratings and the range of application are limited.In order to achieve multiplexing and demodulation of fiber Bragg grating of single wavelength,this paper intends to use code division multiplexing technology and related detection technology to improve the signal-to-noise ratio of the system and multiplexing number of sensing gratings.The main contents of the study are as follow:Firstly,based on the study of the principle of fiber Bragg grating sensor,the advantages and the comparison of the commonly used multiplexing technology and the demodulation method,it is focusing that code division multiplexing technology is used as the multiplexing method of fiber Bragg grating sensing and delay interferometer is used as system device of optical domain demodulation.Secondly,the system simulation of fiber grating multiplexing and demodulation based on pseudo-random code sequence is designed and built by using Optisystem7.0optical communication simulation software.In 10GBits/s transmission system,the transmitted code sequence can demodulate the 0.1ns delay of two Fiber Bragg grating points with the same wavelength.The relationship between the code sequence of different code length and the maximum number of gratings,and the relationship between the code length and the simulation effect of different code length are studied.Finally,the feasibility and correctness of fiber Bragg grating multiplexing and demodulation research scheme for pseudo-random code sequences are validated.Finally,an experimental system of multiplexing and demodulation of fiber grating sensing network based on pseudo-random code sequence is proposed.The differentreflection points on the fiber are identified by experimental system,and the influence of different temperature on the signal voltage output from the experimental system is studied by temperature experiment.