Optical fiber distributed monitoring system and method

Abstract

The embodiment of the invention provides an optical fiber distributed monitoring system and method, and relates to the field of optical fiber sensing. The system includes a laser, an acousto-optic modulator, a phase matching interferometer, a photoelectric detector, and a phase demodulation module. The backward Rayleigh scattered light, containing the parameter information, of a sensing optical fiber enters the phase matching interferometer and then enters the two arms of the phase matching interferometer. The phases of the light of two arms of the phase matching interferometer are modulated through a first modulation waveform and a second modulation waveform, and then the light of two arms of the phase matching interferometer interferes with each other to generate interference light. Thephotoelectric detector converts an optical signal into an electric signal, and the phase demodulation module processes the electric signal based on the Hilbert algorithm to obtain the parameter changecondition of a to-be-tested environment. Since there is no need of the collection of the modulation waveform when the Hilbert algorithm is used for processing, and the amplitude difference between afirst modulated wave and a second modulated wave is greater than or equal to an amplitude difference threshold capable of enabling the phase difference of the two arms of the phase matching interferometer to be 2*Pi, the processing can be performed.

Description

technical field [0001] The invention relates to the field of optical fiber sensing, in particular to an optical fiber distributed monitoring system and method. Background technique [0002] Optical fiber distributed sensing technology can continuously measure the external physical parameters distributed along the optical fiber geometric path. It is widely used in intelligent bridges, highways, important buildings, gas pipeline monitoring and other fields. Optical fiber distributed monitoring mainly includes two distributed monitoring systems based on intensity demodulation and phase demodulation. The distributed monitoring system of intensity demodulation can only demodulate the back Rayleigh scattered light intensity change information within a unit pulse. The scope of application limited, and the distributed monitoring system of phase demodulation can demodulate the phase information of the back Rayleigh scattered light interference light in a unit pulse, which has a wide...

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Problems solved by technology

[0003] The PGC scheme needs to increase the carrier, and it needs to collect the interference light and the modulation wave at the same time, that is, it needs to demodulate two signals at the same time, so the frequency and amplitude of the carrier need to be strictly quantified to meet the requirements of the demodulation accuracy of the system. The dynamic range of the system is limited by the carrier frequency

3×3 coupler demodulation requires simultaneous acquisition of 3 signals, which leads to a larger amount of data and complicates the system, because the 3×3 coupler demodulation principle is based on an included angle of 120°, but the actual production of 3×3 couplers does not It is not exactly 120°, so the included angle of the 3×3 coupler will also affect the demodulation accuracy

[0004] To sum up, the process of obtaining demodulation data in the prior art is relatively complicated, and there are many factors affecting the accuracy, resulting in low accuracy of the obtained demodulation data

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