Method for reducing dead zone probability in phi-OTDR system based on space division multiplexing

Abstract

The invention discloses a method for reducing dead zone probability in a phi-OTDR system based on space division multiplexing, which comprises the following steps: equally dividing an intermediate frequency signal into N groups of data, numbering the data in sequence and reversing the data in even number sections to obtain N groups of data aligned end to end, carrying out orthogonal demodulation,and demodulating amplitude and phase information; selecting one group with the maximum amplitude at the same position in the N groups of data and recording the serial number of the group as addressinginformation of the selected phase; carrying out difference on the data of two adjacent columns according to the phase information of the N groups of data to obtain a phase variation matrix of two adjacent columns at each position; according to the addressing information, obtaining phase differences of two adjacent columns under each distance length and adding the phase differences to the phase ofthe previous position to obtain phase information corrected under the distance length; and selecting a proper distance to perform phase difference on the corrected phase information matrix accordingto actual requirements, and performing unwrapping to obtain actual vibration information of the optical cable along the line. According to the invention, the probability of phase demodulation errors can be reduced by carrying out selective reconstruction on the phase at each position.

Description

technical field [0001] The invention relates to a method for reducing dead zone probability in a Φ-OTDR system based on space division multiplexing, and belongs to the technical field of optical fiber sensing. Background technique [0002] Phase-sensitive optical time-domain reflectometry (Φ-OTDR) is a new type of distributed optical fiber sensing technology. It has the characteristics of high sensitivity, fast response speed and distributed sensing. It can realize the detection and dynamic monitoring of weak vibration events. Therefore, it has broad application prospects in the fields of large-scale structural health monitoring, perimeter security and pipeline safety detection. Φ-OTDR uses the coherent fading phenomenon of the back Rayleigh scattered light of the optical pulse for sensing, using a narrow linewidth laser light source, the light source has high coherence, and the generated backscattered signal will undergo coherent fading, namely coherent Rayleigh noise. Wh...

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Problems solved by technology

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, provide a method for reducing the dead zone probability in a Φ-OTDR system based on space division multiplexing, solve the problem of extracting correct phase information in coherent Rayleigh noise, and reduce dead zone probability. The problem of the probability of occurrence of the area

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