Research On Dynamic Strain Monitoring Technology Based On Brillouin Scattering Spectrum

Distributed optical fiber sensing technology has many important meanings in building and other engineering applications.By reviewing the relevant literatures at home and abroad,we realize the practical significance of distributed optical fiber sensing technology.After analyzing a variety of distributed optical fiber sensing technology.We propose a new distributed optical fiber temperature/strain sensing system which based on Brillouin scattering by taking advantage of the unique advantage of Brillouin scattering.This system can detect the temperature/strain along the fiber quickly.Here are the main studies of the paper:1.Basing on the Brillouin scattering principle,a Brillouin distributed optical fiber sensing theoretical model is derived.And we discuss the differences in the mechanisms of spontaneous emission and stimulated Brillouin scattering.The relationship between Brillouin frequency shift and fiber temperature/strain variation is discussed in detail.Relationship between Brillouin scattered light intensity and temperature/strain changes is also discussed.And the main performance parameters of the Brillouin sensor system is analyzed.The main factors affecting various performance parameters is explored,this work lays the foundation for the design of the sensing system2.The BOTDA system is designed,an experimental system is set up,and fiber-optic strain sensing experiments are conducted.The frequency synthesizer is controlled by serial debugging software to move the optical frequency of continuous detection light.Three-dimensional inspection software is prepared to realize real-time acquisition of fiber Brillouin frequency spectrum.The scanning interval and width of frequency and the length of the sensing fiber affect the measuring time of the system The experiment verified that the measurement time is 40 s,spatial resolution is 4m.3.Innovative solution based on optical auto-coherence sensing that can quickly reduce measurement time is proposed.Theoretical model for obtaining Brillouin scattered light frequency information through an auto-coherent optical path is established.The key structural devices matched with this new solution is descripted.Focuses on the separation of Rayleigh scattered light from Brillouin scattered light.4.The designed self-coherent optical path structure is combined,we deduce The theoretical model for generating Brillouin difference frequency information by optical heterodyne technology.Demodulation problem for difference frequency information,A method for demodulating real-time difference frequency information using a 3x3 coupler is proposed.And we deduce the theoretical model of 3×3 coupler demodulation.MATLAB software is used to carry out simulation analysis of multiple frequency information demodulation.The conclusion that the 3×3 coupler can accurately demodulate the signal frequency is gotten,provide a theoretical basis for strain/temperature demodulation of new sensing solutions.5.the construction of the entire innovative experimental system is finished,a display interface is written by using C++ programming language and MFC framework protocol.Theoretically,it is confirmed that this method can greatly shorten the measurement time.