Research On Two-Dimensional Decomposition Method Of Distributed Optical Fiber Sensor Vibration Signal

The distributed fiber optic vibration sensing technology,represented by Phase sensitive Optical Time Domain Reflectometer(Phase-OTDR),is based on the transmission properties of the fiber optic signal and measures the collected external environmental vibration parameters.With the widespread application of distributed fiber optic sensing technology,the processing method for collecting fiber optic vibration signals has been studied by many people,and empirical mode decomposition method is the foundation for vibration signal analysis and processing research.Based on the characteristics of two-dimensional vibration signals collected by the Phase-OTDR instrument,the research object of empirical mode decomposition method is expanded from one-dimensional signals to twodimensional signals.The empirical mode decomposition method is improved,and the construction of the extreme envelope curve of onedimensional signals is improved to the construction of the extreme envelope surface of two-dimensional signals.Surface empirical mode decomposition method and surface set empirical mode decomposition method are proposed to achieve two-dimensional signal decomposition research.(1)This paper investigates the empirical mode decomposition method for two-dimensional decomposed surfaces(Camber EMD).According to the two-dimensional distribution characteristics of the vibration signals of Phase-OTDR optical fibers,this paper proposes a surface empirical mode decomposition method.Considering the two dimensional characteristics of two-dimensional Phase-OTDR vibration signals,the fitting of envelope curve in the empirical mode decomposition method is improved to the fitting of envelope surface by obtaining the extreme value of the twodimensional signal and surface interpolation.The two-dimensional decomposition of Phase-OTDR fiber vibration signal is completed.(2)This paper investigates the empirical mode decomposition method for two-dimensional decomposed surfaces(Camber EEMD).The surface empirical mode decomposition method can realize the decomposition of two-dimensional signals.Due to the existence of interference factors in the environment,the collected Phase-OTDR fiber vibration signal is always composed of useful signals and noise,and the noise in the signal is easy to lead to the phenomenon of frequency cross among the components of the decomposed signal.In view of this phenomenon,this paper proposes a surface set empirical mode decomposition method.White noise can be used to change the properties of signal extremum distribution.Random white noise is added to the original fiber vibration signal,and the mean value of the eigenmode function obtained by multiple decomposition of the new signal is taken as the final result.The Camber-EEMD decomposition method based on Phase-OTDR fiber vibration signal is studied.(3)Phase-OTDR signal decomposition effect validation experiment.In this paper,the optical fiber vibration signal actually collected by the Phase-OTDR instrument is taken as the experimental object,and the improved EMD and EEMD methods and the improved Camber-EMD and Camber-EEMD methods are used to verify the Phase-OTDR distributed optical fiber vibration signal respectively.The signal quality and experimental effect were evaluated from multiple angles by using three evaluation indexes:peak signal-to-noise ratio,root-mean-square error and orthogonality.(4)Phase OTDR signal recognition effect verification experiment.The method proposed in this paper is compared with other methods in signal decomposition and signal recognition experiments.The experimental results further show that the proposed method is applicable.In this paper,the two-dimensional decomposition method of vibration signal of Phase-OTDR distributed optical fiber sensing can simultaneously process the signal characteristics of optical fiber vibration signal in the space-time dimension,and the decomposed signal components retain the characteristics of the original target signal,improve the decomposition accuracy,and reduce the degree of mode aliasing between signals.The effectiveness of the proposed method is verified by experiments on vibration and recognition of Phase-OTDR vibration signals.