芝浦工業大学との共同研究の成果が Scientific Reports に掲載されました。

ブリルアン光相関領域反射計において観測されるレイリーノイズスペクトルの発生要因を解明した論文が、Scientific Reports に掲載されました。芝浦工業大学の菊地君（M1）が中心となって進めた共同研究の成果です。

K. Kikuchi, H. Lee, R. Inoue, K. Noda, and Y. Mizuno, “Mechanisms of multi-layered Rayleigh noise in Brillouin optical correlation-domain reflectometry,” Sci. Rep., vol. 14, 23513 (2024).

In Brillouin optical correlation-domain reflectometry (BOCDR), sinusoidal modulation is applied to the output frequency of a light source, with spatial resolution inversely related to the modulation amplitude. We have developed an effective method to estimate the modulation amplitude using the width of the noise spectrum caused by Rayleigh scattering, eliminating the need for an optical spectrum analyzer or modifications to existing equipment. However, the Rayleigh noise spectrum often displays a three-layered structure, complicating the identification of the appropriate spectral components for estimating the modulation amplitude. In this work, we investigate the origins of this three-layered Rayleigh noise spectrum and identify the directivity of an optical circulator as the source of the third noise component. As replacing the circulator with alternative optical components is not easy, it remains an essential part of the system. Our analysis shows that the third noise component exhibits significantly small variation in spectral width with changes in modulation frequency compared to the first and second components. This characteristic allows for the effective separation and identification of the third noise component, thereby enhancing the accuracy and convenience of modulation amplitude estimation in BOCDR.