Distributed Fiber Optic Vibration Sensing Method and System Based on Pulse Code External Modulation

Abstract

The invention discloses a distributed optical fiber vibration sensing method and system based on pulse coding external modulation. The method comprises the steps that a reverse echo curve obtained by continuous k times of optical pulse emitting is selected, an average time and interval parameters are preset, and a plurality of average curves are acquired; the standardized average curves are combined to form a two-dimensional signal matrix Y, a range matrix is selected to calculate a local range, the vibration strength of a sensing optical fiber is evaluated according to all elements in a range matrix to acquire a vibration space position, the data at the ith point in each echo curve after decoding delay are extracted to obtain time domain sampling signals of vibration. The system comprises a photoelectric detector which forms electrical signals and a signal collecting and regulating device which is used for conducting amplification and analog-digital conversion to achieve digital signals, the digital signals are transmitted into a computer to achieve decoding, time delay, positioning and extraction time domain processing, and the vibration condition along the line of distributed sensors. The distributed optical fiber vibration sensing method and system based on pulse coding external modulation meet the demand for various vibration detection and monitoring application, and is particularly suitable for long-distance pipeline monitoring and perimeter security.

Description

technical field [0001] The invention relates to the field of optical fiber sensing, in particular to a distributed optical fiber vibration sensing method and system based on pulse code external modulation. Background technique [0002] Due to its high sensitivity, immunity to electromagnetic interference, wide detection range, and low cost, distributed optical fiber sensing systems are widely used in long-distance oil and gas pipeline monitoring, perimeter security, and building structure health monitoring. research hotspots. [0003] The Mach-Zehnder / Sagnac interferometer distributed optical fiber sensing system uses the phase difference change caused by external disturbances in the two sensing optical paths to be detected, and is positioned by the correlation time delay estimation method, which can sense vibration well. However, due to the difficulty of determining the time delay in the correlation time delay estimation method itself, the positioning accuracy of this meth...

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Problems solved by technology

[0007] The present invention provides a distributed optical fiber vibration sensing method and system based on pulse code external modulation. The present invention overcomes the problem of insufficient sensing sensitivity of existing monitoring and detection systems under the condition of ensuring positioning accuracy. See the description below for details. :

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