Weak grating array distributed vibration sensing system and method

Abstract

The invention discloses a weak grating array distributed vibration sensing system and a weak grating array distributed vibration sensing method, belongs to the technical field of fiber grating sensing, and solves the problems that demodulation by using a double-arm interferometer in the prior art is easily interfered by an external environment, the bottom noise is large, and the frequency responsebandwidth is relatively narrow. The weak grating array distributed vibration sensing system comprises: a narrow linewidth laser used for generating continuous light with a certain central wavelength;an acoustic optical modulator that is used for modulating the continuous light into a corresponding double-pulse signal; a circulator that is used for transmitting the double-pulse signal to the weakgrating array. The weak grating array reflects the double-pulse signal to a circulator; the circulator is also used for transmitting the reflected double-pulse signal to the 3 * 3 coupler; the 3 * 3coupler is used for enabling the reflected double-pulse signal to form interference and generating an interference signal; and the system also includes a photoelectric detector that is used for acquiring interference signals and converting the interference signals into electric signals. According to the invention, the system bottom noise is reduced, and the signal-to-noise ratio and the frequencyresponse range are improved.

Description

technical field [0001] The invention relates to the technical field of fiber grating sensing, in particular to a weak grating array distributed vibration sensing system and method. Background technique [0002] For the signal acquisition and demodulation end of the distributed weak grating vibration sensing demodulation system; according to the vibration sensing mechanism of the fiber grating, the vibration signal is essentially modulated into the interference signal, and the demodulation of the vibration signal is actually the phase Demodulation: At present, the commonly used phase demodulation methods in distributed sensing systems include quadrature (IQ) demodulation algorithm, phase carrier generation (PGC) detection method and 3×3 coupler demodulation algorithm; [0003] For the signal demodulation of the distributed weak grating vibration sensing demodulation system, the commonly used interferometers are Mach-Zehnder interferometer, Sagnac interferometer and Michelson ...

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Problems solved by technology

[0003] For the signal demodulation of the distributed weak grating vibration sensing demodulation system, the commonly used interferometers are Mach-Zehnder interferometer, Sagnac interferometer, and Michelson interferometer; the pulsed light is reflected back by the continuous weak grating, and finally reaches the interferometer Among them, interference occurs in the coupler after passing through two unequal length interference arms, so that the reflected light of adjacent weak gratings interferes; the interferometer with sensitive arms is easily disturbed by the external environment, such as the temperature of the chassis, the fan , external noise, vibration and other influences, resulting in a large noise floor for signal demodulation, thus affecting the signal-to-noise ratio of the system

In addition, most of the existing vibration sensing systems have a narrow frequency response bandwidth, and it is difficult to respond to low frequencies.

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