東京科学大学との共同研究の成果が Journal of Lightwave Technology に受理されました。

3×3ファイバカプラを用いて位相バイアスを増大させたサニャック干渉計による空中可聴音検出を実証した論文が、Journal of Lightwave Technology に受理されました。東京科学大学のWangさん（D3）と中村先生が中心となって進めた共同研究の成果です。

Z. Wang, Y. Mizuno, and K. Nakamura, “Airborne audible sound detection via phase bias-enhanced Sagnac interferometer using 3×3 fiber coupler,” J. Lightwave Technol., accepted.

In recent years, fiber-optic interferometers have attracted considerable attention for airborne acoustic wave detection. Among them, the Sagnac interferometer has been particularly favored due to its strong suppression of low-frequency thermal disturbances and vibrational noise. This paper proposes a phase-bias-enhanced Sagnac interferometric system, which introduces a stable phase bias via a 3×3 fiber coupler, significantly improving acoustic sensitivity. The system eliminates the need for mechanical diaphragms and instead detects sound through refractive index modulation in air, offering higher stability and retaining intrinsic immunity to electromagnetic interference. Its acoustic sensing element adopts a free-space optical path without physical barriers, minimizing disturbance to the acoustic field during measurement. In addition, the system architecture avoids the use of expensive and complex optical components such as electro-optic modulators, resulting in a more compact, simplified, and cost-effective design. Experimental results demonstrate successful detection of airborne audible sound in the 200 Hz – 13 kHz range using an 8 km fiber delay coil. The system exhibits high sensitivity, good signal-to-noise ratio, and excellent robustness. This research presents a simple, stable, and cost-efficient solution for high-precision acoustic sensing, showing great potential for applications in sound monitoring, environmental perception, and non-contact acoustic signal acquisition.