Research On Multi-parameter Demodulation Technology Based On Brillouin Scattering Distributed Optical Fiber Sensing

The distributed optical fiber sensing system based on Brillouin Optical Time Domain Reflectance(BOTDR)has the characteristics of single-ended incidence and simple structure.It can not only sense temperature and strain through optical fiber,but also transmit information.Aerospace and other fields play an important role.Compared with traditional mechanical and electrical sensors,it has the characteristics of temperature resistance,corrosion resistance and electromagnetic interference resistance,and be used in harsh environmental conditions.However,the backscatter signal of the BOTDR system is weak,and there are problems such as low signal-to-noise ratio,long measurement time,and cross-sensitivity between the parameters to be measured,which restrict the development of BOTDR sensing technology.Therefore,in response to the above problems,this article has carried out research on multi-parameter demodulation technology based on Brillouin scattering distributed optical fiber sensing on the basis of in-depth analysis and research on BOTDR sensing technology,which is important for improving the performance of BOTDR sensing system.Meaning.Based on a large number of references and analysis of the research status of BOTDR systems at home and abroad,this paper expounds the principle of Brillouin scattering in detail.First,a curve fitting algorithm for Brillouin scattering spectrum using Adam algorithm is proposed,and its model is established,and a heterodyne BOTDR strain detection system is built.The experimental results show that the demodulated average strain error after fitting the scattering spectrum curve with this algorithm is 24.89 ??,the fitting degree can reach 0.9989,the root mean square error is 0.1105,and the curve fitting time is only 18.5ms;secondly,the analysis Influencing factors of BOTDR performance,explored the influence of different light source linewidths and different pulse widths on the Brillouin scattering spectrum width;again,through simulation and experiments,explored the signal-to-noise ratio under different pulse extinction ratios;next,using Brillouin The width measurement of the stimulated Brillouin scattering threshold;Finally,build a BOTDR system for heterodyne coherent detection,and perform sensing experiments after calibrating temperature and frequency conversion coefficient.The experimental results show that the temperature error range is ±2.2?,and the spatial resolution is 5m.In the 10km strain sensing experiment,when the maximum measured strain of the BOTDR system is 9500 ??,the demodulation error of the strain is ±37.1.??.