Optical fiber vibration sensing system of single light source pulse and sensing method thereof

Abstract

The invention discloses an optical fiber vibration sensing system of a single light source pulse and a sensing method of the optical fiber vibration sensing system of the single light source pulse. Under the control of FPGA, a code is formed by an optical pulse, coded pulsed light is formed through a coupler, a sensing optical fiber is injected through an optical fiber circulator, interference is generated by backward propagation scattered light generated in the process of the propagation of the sensing optical fiber, the interference enters into the coupler through the optical fiber circulator to be interfered with local oscillating light, and beat frequency signals are generated; the beat frequency signals are converted into electrical signals by a photoelectric detector, difference frequency components are filtered through a band-pass filter circuit, the reduction of beat frequency is achieved through a frequency mixer, at last the signals are collected and amplified by a collection card, in an upper computer, the respective amplitude modulation and demodulation of each control frequency are achieved, and decoding and location processing are carried out. The optical fiber vibration sensing system of the single light source pulse has the advantages, peculiar to a distributed optical fiber detecting and monitoring system, of being distributed and subject to small external disturbance such as electromagnetism, the installation is convenient, and various vibration detecting and monitoring application, especially for long distance pipeline monitoring and perimeter security, can be met well.

Description

Technical field [0001] The invention relates to the field of optical fiber sensing, in particular to a single-light source pulse encoding optical fiber vibration sensing system and a sensing method thereof. 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, building structure health monitoring and other fields. Research hotspots. [0003] The Mach-Zehnder / Sagnac interferometer distributed optical fiber sensing system uses the detection of the phase difference changes caused by external disturbances in the two sensing optical paths, and locates through the method of related time delay estimation, which can have a good sense of vibration. However, due to the difficulty of determining the time delay by the relevant time delay estimation method, the positioning accuracy of t...

AI Technical Summary

Problems solved by technology

At the same time, because the spatial resolution is related to the pulse length, very narrow pulses are often used for spatial resolution, usually tens to hundreds of nanoseconds, so the return light intensity is weak, and the signal resolution is low after long-distance transmission , limiting the dynamic range

[0006] The Φ-OTDR based on pulse modulation can effectively improve the sensing distance on the basis of ensuring the spatial resolution, but because each modulation pulse needs to be independent of each other, multiple light sources are required to realize the system complexity. , the cost is also higher

Images