Research On Data Processing In BOTDR Sensing System

The Brillouin Optical Time Domain Reflection(BOTDR)sensing system is a distributed optical fiber sensing system that utilizes the self-published Brillouin scattering effect in optical fibers to simultaneously monitor external temperature and stress changes.BOTDR sensing system has broad prospects in various fields,such as:optical fiber and cable manufacturing process,power security field,traffic roads,bridges,oil and gas pipelines and other large structures health monitoring.In the BOTDR sensing system,the backscattering signal is very weak,which causes the system noise to have a greater impact on the detection results.At the same time,the distributed measurement system results in a huge amount of data collected and the measurement time of the system is too long.In practical engineering applications,especially in scenarios that require high real-time and high accuracy,BOTDR sensing system needs to reduce measurement time while ensuring accuracy.Therefore,how to effectively process the weak scattered signals in the BOTDR optical fiber sensing system to ensure the detection accuracy and reduce the amount of data processing operations has become an important part of the Brillouin distributed optical fiber sensing system.Aiming at the high accuracy and high real-time requirements of the BOTDR sensing system in practical engineering applications,this paper mainly completes the research of the reflection signal processing in the system,and designs a complete set of algorithm schemes.This data processing scheme reduces the measurement time while ensuring the detection accuracy.The work done in this article is summarized as follows:1.Introduce the theory of BOTDR distributed optical fiber sensing system,analyze the linear relationship between Brillouin frequency shift(BFS)and external temperature and strain of optical fiber.And design a set of microwave heterodyne sweep frequency detection BOTDR sensing system.2.Analyzed the characteristics of Brillouin scattering signals,combined with the requirements of BOTDR system for high accuracy and high real-time,analyzed and compared the data processing algorithms of weak scattered signals.Finally,superimposed averaging,Morlet wavelet transform and particle swarm optimization(PSO)are used to complete the data analysis,forming a complete data processing scheme and verifying the feasibility of the algorithm through simulation.3.Build the experiment in the laboratory environment,and use the synchronous superimposed average denoising method to effectively extract the weak signal,use the Morlet wavelet transform to effectively extract the envelope of the Brillouin signal,and use particle swarm optimization(PSO)to estimate unknown parameters of Lorentzian model of Brillouin scattering signal.It is proved that this data processing scheme meets the requirements of high accuracy and high real-time performance of BOTDR system in practical engineering applications.