関根君（M1）の成果が Optical Fiber Technology に受理されました。
光相関領域反射計において偏波状態制御により近接反射点を分離検出した関根君（M1）の論文が、Optical Fiber Technology に受理されました。
Y. Sekine, Y. Higa, K. Motoda, T. Kiyozumi, T. Ishimaru, H. Takahashi, K. Toge, and Y. Mizuno, “Identification of closely spaced reflection points by polarization-state-controlled optical correlation-domain reflectometry,” Opt. Fiber Technol., accepted.
Reliable identification of localized reflection events is essential for diagnosing optical fiber links in high-capacity communication networks. Optical correlation-domain reflectometry (OCDR) enables distributed reflectivity measurements with high spatial selectivity; however, closely spaced reflection points can be difficult to distinguish when their reflection peaks overlap because of insufficient effective spatial resolution or surrounding noise. Here, we propose and experimentally demonstrate a polarization-state-control method for identifying closely spaced reflection points in OCDR. The method exploits the polarization dependence of the beat-signal waveform and selectively enhances the contribution from each reflection point by adjusting the polarization state of the reference light. Experiments were performed using two reflection points with separations of 5.0, 3.0, and 1.3 cm in three OCDR configurations: sinusoidal-modulation OCDR with an acousto-optic modulator (AOM), sinusoidal-modulation OCDR without an AOM, and periodic pseudo-random modulation OCDR. Under polarization-scrambled conditions, the two reflection contributions appeared as a single overlapped response in all configurations. In contrast, reference-polarization adjustment produced states that selectively enhanced either reflection point, enabling their contributions to be identified down to the smallest tested separation of 1.3 cm. For the 5.0-cm condition, the apparent 3-dB peak widths ranged from 8.2 to 12.3 cm and exceeded the physical separation, confirming that the identification did not result from conventional peak-width-limited spatial resolution. The proposed method therefore provides an additional degree of freedom for identifying overlapping reflection events, provided that they exhibit sufficiently distinguishable effective polarization responses.
