Method and system for positioning disturbance signal of optical fiber distributed disturbance sensing system

Abstract

The invention discloses a method for positioning a disturbance signal of an optical fiber distributed disturbance sensing system. The method comprises the following steps of: S1, performing noise reduction processing on backward Rayleigh scattering light by using a wavelet threshold noise reduction method of EMD to obtain a noise reduction signal; S2, performing segmentation processing according to the overall level of the data acquired by the system, and determining alarm thresholds of different distance range segments; and S3, positioning a disturbance event according to the noise reductionsignal obtained in the step S1 and the alarm threshold set in the step S2. On the basis of not introducing other technologies into the system, a long monitoring distance and a low false alarm rate areachieved. The method is simple in process, easy to implement, low in cost and suitable for practical application.

Description

technical field [0001] The invention belongs to the field of optical fiber distributed disturbance sensors, and in particular relates to a signal processing method of a Φ-OTDR optical fiber distributed disturbance sensing system based on an EMD wavelet threshold noise reduction method and a segmented threshold method. Background technique [0002] The optical fiber distributed optical fiber sensing system based on the phase-sensitive optical time domain reflectometer (Φ-OTDR) uses pulsed light with narrow linewidth and low frequency drift, and detects the back Rayleigh scattering generated in the optical fiber within a fixed pulse width through a photodetector. Light, after subsequent data processing, achieves the monitoring and positioning of the disturbance position. [0003] The sensing distance of the traditional Φ-OTDR optical fiber distributed disturbance sensing system can generally only reach about 26km. Due to the limitation of nonlinear effects, it is difficult to ...

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Problems solved by technology

[0003] The sensing distance of the traditional Φ-OTDR optical fiber distributed disturbance sensing system can only reach about 26km. Due to the limitation of nonlinear effects, it is difficult to achieve long-distance monitoring and low false alarm rate.

In order to improve the sensing distance, the existing solutions not only increase the system cost but also increase the complexity of the system by introducing new amplification technology.

In order to reduce the false alarm rate, Empirical Mode Decomposition (EMD) and wavelet threshold denoising method are usually used, and the EMD denoising method discards some high-frequency components from the decomposed components. At the same time, part of the useful information in the high frequency band is also lost together, which may lead to serious distortion of the useful signal; the wavelet threshold noise reduction method also has the same defect, while discarding the noise signal, it also discards the useful signal together, so how to effectively It is particularly important to remove the noise signal and reduce the distortion of the real signal to achieve longer distance monitoring and reduce the false alarm rate

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