Distributed Optical Fiber Sensing Spatial Domain/transformation Domain Noise Reduction

The development of optical fiber communications has enabled fiber media to be widely used in various fields.Among them,the Distributed Optical Fiber Sensing(DOFS)based on optical fiber is widely used in many aspects because of its various advantages,which has caused widespread concern.Among them,the Brillouin Optical Time Do-main Analyzer(BOTDA)and the Phase-Sensitive Optical Time-Domain Reflectometer(Φ-OTDR)are very classic in the DOFS system.This kind of system also has a wide range of application prospects.How to further improve the performance of the system has become a hot topic of research.In the DOFS system,it is impossible to collect the ideal pure signal in the real environ-ment due to the noise inside the system and the interference outside the system.Therefore,when dealing with a noisy signal,it is necessary to establish a suitable noise model for the signal,analyze the characteristics of the noise,and finally eliminate the influence of the noise on the system as much as possible.In this paper,a noise model based on empirical mode decomposition is proposed.EMD is used to eliminate system noise and ultimately improve system performance.The specific work of this article is described as follows:1.Introduced the scattering physics phenomenon in the optic fiber,mainly introduced the basic theory of Stimulated Brillouin Scattering(SBS)and Rayleigh scattering,and based on this,introduced Φ-based on Rayleigh scattering.The OTDR sensor system and the BOTDA sensor system based on the SBS function analyze the sensing principle of the system,and also introduce the evaluation index parameters of various sensing systems.The sources of possible noise in the DOFS system are analyzed.It mainly includes laser noise in the system,noise from various optical devices and electrical devices,and noise outside the system.2.The empirical mode decomposition is applied to the Φ-OTDR system and the input phase signal is decomposed into sub-signals.Through the method of mutual rela-tionship discriminant analysis and spectrum analysis,the noise-dominated sub-signals are removed,and the signal-dominated sub-signals are used to reconstruct signals to complete the noise reduction of the system signals and improve the performance of the Φ-OTDR system.3.The empirical mode decomposition is applied to the BOTDA system.After each signal acquired by the system is subjected to empirical mode decomposition,a partial sub signal is selected to reconstruct the signal of the system.The noise on the signal ultimately reduces the system’s uncertainty and compares it with existing image processing methods,highlighting the performance and role of the empirical mode decomposition method in the BOTDA system.