A three-terminal coupled φ-OTDR measurement device and method based on Sagnac interferometer with adjustable phase.

By using a three-terminal coupled-OTDR measurement device based on a Sagnac interferometer, and by adjusting the signal phase difference with a semiconductor optical amplifier and employing a differential cross-multiplication algorithm, the problems of insufficient spatial resolution and demodulation accuracy in existing technologies are solved, and the correct recovery and high-precision demodulation of different vibration signals are achieved.

CN116773004BActive Publication Date: 2026-05-26TAIYUAN UNIVERSITY OF TECHNOLOGY
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
TAIYUAN UNIVERSITY OF TECHNOLOGY
Filing Date
2023-06-29
Publication Date
2026-05-26

AI Technical Summary

Technical Problem

Existing interferometric three-terminal coupled-OTDR systems suffer from the problem that spatial resolution and demodulation accuracy cannot be satisfied simultaneously, and they cannot correctly recover signal waveforms when faced with vibration signals of different intensities and frequencies.

Method used

A three-terminal coupled-OTDR measurement device based on the phase-tunable Sagnac interferometer is adopted. A Sagnac interferometer is formed with the Sagnac ring through a 3×3 coupler, and a semiconductor optical amplifier is inserted in the Sagnac ring. The phase difference between the positive and negative signals in the Sagnac ring is adjusted by controlling the intensity of the control beam, and demodulation is performed by combining the differential cross-multiplication algorithm.

Benefits of technology

It achieves accurate recovery of vibration signals of different intensities and frequencies, improves the spatial resolution and demodulation accuracy of the system, and avoids the resolution reduction problem caused by optical path difference in Michelson or Mach-Zehnder interferometers.

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Abstract

This invention relates to distributed fiber optic sensing systems. A phase-tunable three-terminal coupled φ-OTDR measurement device based on a Sagnac interferometer is disclosed, comprising: a first pulsed light source, a first optical circulator, a sensing fiber, a continuous fiber amplifier module, a second optical circulator, a 3×3 optical coupler, a Sagnac ring, a semiconductor optical amplifier, a 1×2 optical coupler, a second pulsed light source, a second acousto-optic modulator, a first photodetector, a second photodetector, a third photodetector, and a data acquisition card. This invention achieves phase demodulation of different vibration signals by setting a semiconductor optical amplifier in the Sagnac ring and adjusting the phase difference between two signals by regulating the intensity of the control beam. Furthermore, it effectively avoids the problem of reduced spatial resolution caused by path difference between two signals in Michelson or Mach-Zehnder interferometers.
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