Distributed optical fiber vibration sensing system capable of eliminating fading noise and its demodulation method

Abstract

A distributed optical fiber vibration sensing system capable of eliminating fading noise and its demodulation method, including: a signal generation module, a narrow linewidth laser light source module, a frequency sweeping and cutting pulse module, a circulator, a sensing fiber, and a coherent receiving module , a photoelectric conversion module and a digital signal processing module; the computer obtains the reflectivity curve of the sensing fiber by generating multiple digital band-pass filters with different frequency bands and non-overlapping, combined with the original data segments from multiple frequency-sweeping detection light pulses; Perform phase-shifting average processing on the reflectivity curves to obtain multiple integrated reflectivity curves without interference and polarization fading; perform delay differential processing on the integrated reflectivity curves to obtain multiple phase difference curves; calculate the variance of the phase difference curves to obtain a Phase variance curve; determine the vibration point according to the variance in the phase variance curve, and obtain the position and vibration waveform of the vibration point; the invention has reasonable design, high positioning accuracy, and can simultaneously obtain high spatial resolution and long detection distance.

Description

technical field [0001] The invention relates to a technology in the field of optical fiber sensing, in particular to a distributed optical fiber vibration sensing system capable of eliminating fading noise and a demodulation method thereof. Background technique [0002] Vibration sensing technology is widely used in engineering fields, such as boundary intrusion monitoring, structural health monitoring, oil pipeline safety monitoring, seismic wave monitoring, etc. Traditional vibration sensors are generally mechanical or electromagnetic, and there are many problems. For example, in a strong electric field environment, traditional vibration sensors are susceptible to electromagnetic interference and cannot work normally; in an inflammable and explosive environment, electric sparks will be generated. Causing accidents; In remote locations, there are power supply issues; Distributed sensing cannot be achieved. These defects severely limit the practical application of tradition...

AI Technical Summary

Problems solved by technology

[0006] Aiming at the defects of low signal-to-noise ratio and inability to eliminate polarization fading and interference fading noise in the prior art, the present invention proposes a distributed optical fiber vibration sensing system and its demodulation method that can eliminate fading noise. The series signal performs vibration detection on the sensing fiber, the returned Rayleigh backscattered light beats the reference light, and then uses a matched filter to obtain phase information, and then uses the "frequency conversion-phase shift average" method to perform depolarization fading and interference fading , according to the phase information without fading noise to accurately locate the position of the vibration point and the vibration waveform, the signal-to-noise ratio is high

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