Passive homodyne demodulation device and passive homodyne demodulation method for fai-OTDR (optical time domain reflectometer)

Abstract

The invention discloses a passive homodyne demodulation device and a passive homodyne demodulation method for a fai-OTDR (optical time domain reflectometer). The device consists of piezoelectric ceramics, an optical fiber coupler, a photoelectric detector, an analysis control module and a piezoelectric ceramic driver module. The method belongs to a PGC (programmed gain control)algorithm with phase modulation degree measurement improvement, the passive homodyne detection of Rayleigh scattering light phases in sensing optical fibers of the fai-OTDR is realized, the phase external modulation is carried out through PZT (plumbum-based lanthanum-doped zirconate titanate), Rayleigh scattering light and local reference light interference signals are unfolded through a Bessel function, the amplitude value of each subharmonic items unfolded by the Bessel function is analyzed, further, the phase modulation degree is obtained through analysis, and the Rayleigh scattering light phase is further solved. The structure of the device is simple, the sensitivity is high, and the performance is stable. The method has the advantages that the passive homodyne detection of the Rayleigh scattering light in the sensing optical fibers of the fai-OTDR is realized, a detecting device is simplified, and the operation cost of a system is reduced. The device and the method are applicable to optical fiber hydrophones, public security, ground invasion detection, failure positioning and the like.

Description

technical field [0001] The present invention relates to a distributed optical fiber sensor and a Φ-OTDR; it also relates to a method for passive homodyne demodulation, especially a distributed sensor for optical fiber phase modulation detection using low-cost PZT piezoelectric ceramics A detection device and a detection method for the phase of back Rayleigh scattered light. Background technique [0002] Distributed optical fiber sensing technology uses an optical fiber as an extended sensing element. Any section of the optical fiber is not only a sensing unit, but also an information transmission channel for other sensing units. Distribution information that changes over time. It eliminates the sensing "blind zone" existing in traditional sensing units, and fundamentally breaks through the traditional single-point measurement limitation. Among them, Optical Time Domain Reflectometry (OTDR) is the most mature optical fiber distributed sensing technology at present, and is ...

AI Technical Summary

Problems solved by technology

Φ-OTDR is based on the principle of detecting Rayleigh scattered light in the optical fiber, and responds to external vibration and temperature changes through the phase change of Rayleigh scattered light. The detection method of Rayleigh scattered light is divided into heterodyne detection and homodyne detection, heterodyne detection Mainly use acousto-optic or electro-optic frequency shifter to frequency shift the reference light. The acousto-optic frequency shifter has stable performance, but the modulation bandwidth is limited and the price is expensive. The integrated electro-optic frequency shifter has high modulation frequency, but the performance varies with temperature and environment changes

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