ORIGINAL RESEARCH article
Front. Phys.
Sec. Optics and Photonics
Volume 13 - 2025 | doi: 10.3389/fphy.2025.1609493
This article is part of the Research TopicNovel Optical Measurement and Imaging Technologies using Broadband Light SourcesView all 6 articles
Phase demodulation of hybrid 3×3 coupler and Sagnac interferometer for φ-OTDR
Provisionally accepted
- 1Taiyuan University of Technology, Taiyuan, China
- 2Taiyuan Normal University, Taiyuan, Shanxi Province, China
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A hybrid phase demodulation structure combining a 3×3 coupler and Sagnac interferometer is proposed to improve the spatial resolution and phase demodulation performance of the phase-sensitive optical time-domain reflectometer (φ-OTDR). In this structure, the forward and reverse light propagation paths in the Sagnac interferometer have identical optical path lengths, thereby solving the spatial resolution degradation issue caused by optical path differences in conventional schemes (such as the 3×3 demodulation scheme combined with unbalanced Michelson or Mach-Zehnder interferometers). In addition, by integrating a Semiconductor Optical Amplifier (SOA) into the Sagnac interferometer, the phase difference between the forward and reverse paths can be dynamically adjusted, thus enhancing the signal-to-noise ratio (SNR) of the three output signals and ensuring high phase demodulation quality. Through theoretical analysis and numerical simulation, the performance enhancement effect of this structure has been verified. The results indicate that the SOA modulates the phase offset of the three output signals, significantly improving the phase demodulation quality and extending the amplitude and frequency response range of the system. Compared with the positioning results achieved by the unbalanced Michelson scheme, this method offers higher spatial resolution.
Keywords: Distributed acoustic sensing, Sagnac interferometer, spatial resolution, amplitudefrequency response, Phase demodulation
Received: 10 Apr 2025; Accepted: 23 Jun 2025.
Copyright: © 2025 BinYuan, Wang, Zhang, Ma, He, Liu, Wang and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Tingyu Wang, Taiyuan Normal University, Taiyuan, 130012, Shanxi Province, China
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