Distributed optical fiber sensing system capable of realizing all phase demodulation and measuring method thereof

Abstract

The invention discloses a distributed optical fiber sensing system capable of realizing phase demodulation and a measuring method thereof. The distributed optical fiber sensing system comprises a narrow line width laser, a first coupler, a first acousto-optic modulator, a second acousto-optic modulator, a delayed optical fiber, a second coupler, a first erbium-doped optical fiber amplifier, a circulator, a second erbium-doped optical fiber amplifier, a filter, a photodetector, a data acquisition card and an industrial control machine. A heterodyne pulse pair is introduced into the traditionalphi-OTDR system, the vibration signal of a certain position of the optical fiber is modulated to the heterodyne frequency, and the amplitude and the frequency of the external vibration signal at any position along a to-be-tested optical fiber are obtained through a heterodyne demodulation algorithm. The amplitude and the frequency of the external vibration signal at any position along the to-be-tested optical fiber can be obtained in real time, and a large dynamic range can be acquired; and with an example of the heterodyne frequency of 50 kHz, the system can detect signals with the amplitudesfrom 0.1 rad to 100 rad and can detection signals with the frequencies from 10 Hz to 25 kHz.

Description

technical field [0001] The invention relates to optical fiber sensing technology, in particular to a distributed optical fiber sensing system capable of realizing all-phase demodulation and a measurement method thereof. Background technique [0002] Distributed optical fiber sensing is a new type of sensing technology. Unlike point sensors, distributed sensing can obtain vibration information at any position along the optical fiber, and the sensing distance can range from hundreds of meters to hundreds of kilometers. Distributed optical fiber sensing has been widely used in oil pipeline monitoring, perimeter security and other fields due to its advantages of anti-electromagnetic interference, high sensitivity and long sensing distance. [1] . One of the most widely used distributed optical fiber sensing systems is the phase-sensitive optical time domain reflectometer (Φ-OTDR) based on the principle of Rayleigh scattering in optical fibers. The system first injects a narrow ...

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Problems solved by technology

Because only the strength is judged, the traditional scheme cannot obtain the amplitude and frequency information of the external vibration signal very well.

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