Phase sensitive light time domain reflection system based on dual homologous heterodyne coherent detection

Abstract

The invention discloses a phase sensitive light time domain reflection system based on dual homologous heterodyne coherent detection, and the system consists of a laser, a coupler, an AOM (acoustic optical modulator), an EOM (electro-optic modulator), an erbium-doped optical fiber amplifier, a filter, a circulator, balance detectors, power dividers, and a data collection card. The balance detector 1 enables the beat frequency signals of received modulated light and local oscillation light to be converted into AC signals, and the balance detector 2 enables the beat frequency signals of received Rayleigh light and local oscillation light to be converted into AC signals, wherein the frequency mixing of the AC signals is carried out through the power dividers 1 and 2, and the outputted AC signals are converted into digital signals through the data collection card, and the processing of the data signals are carried out in a computer. The system carries out the tracking of the drift of frequency and phase changes in a detection arm through a beat frequency signal which is generated by an interference reference arm and does not contain vibration information, can effectively avoid a distortion phenomenon of a detected signal, obtains the stable vibration signal intensity and frequency information, and improves the recognition rate of a vibration source.

Description

technical field [0001] The invention relates to a distributed optical fiber vibration sensing system, in particular to a phase sensitive optical time domain reflection system based on double homologous heterodyne coherent detection. Background technique [0002] At present, phase-sensitive optical time-domain reflectometry technology is developing rapidly. It can realize real-time monitoring of multi-point disturbances. It has the advantages of high sensitivity, wide dynamic range, and strong anti-electromagnetic interference characteristics. Safety monitoring and real-time early warning in multiple fields such as health and train operation status. The research on this technology has been based on the accurate identification of multi-point positioning and steering signals to reduce the false alarm rate of the system. [0003] The realization of phase-sensitive optical time-domain reflectometry mainly depends on two system structures: direct detection and coherent detection....

AI Technical Summary

Problems solved by technology

Another method first converts the AC signal into a digital signal, and then performs digital mixing and digital filtering in the computer, so digital coherent detection requires a data acquisition card with an ultra-high acquisition frequency, and at the same time requires more storage space and data processing Time, resulting in poor real-time digital coherent detection method

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