Fiber-optic distributed measurement of polarization beat length using slope-assisted Brillouin optical correlation-domai
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Fiber‑optic distributed measurement of polarization beat length using slope‑assisted Brillouin optical correlation‑domain reflectometry Heeyoung Lee1 · Kohei Noda2,3 · Kentaro Nakamura2 · Yosuke Mizuno3 Received: 14 June 2020 / Accepted: 28 September 2020 © The Optical Society of Japan 2020
Abstract We demonstrate distributed measurement of the polarization beat length along single-mode optical fibers (SMFs) using slope-assisted Brillouin optical correlation-domain reflectometry (BOCDR) with high spatial resolution, long measurement range, high sampling rate, and single-end accessibility. The beat lengths of SMFs wound on mandrels with radii of 10.5, 7.5, and 3.4 cm are measured to be 36.0, 18.2, and 3.7 m, respectively, which agree well with theoretical calculations. This indicates that a unique beyond-nominal-resolution effect of slope-assisted BOCDR does not influence the measurement. Subsequently, distributed beat length measurement is demonstrated using an SMF comprising two sections wound on mandrels with different radii (10.5 and 3.4 cm). Keywords Optical fiber sensing · Distributed measurement · Correlation-domain technique · Polarization beat length In the recent high-speed fiber-optic communication with a transmission rate of > 100 Gbps, polarization mode dispersion (PMD), i.e., the differential group delay (DGD) between two polarization modes propagating along single-mode fibers (SMFs), has proved to be one of the most serious effects that degrade the transmission capacity. It is thus of great significance to obtain the information of DGD. Though several methods of measuring PMD have been developed [1], they provide merely the overall DGD of a certain link, not spatially resolved information of DGD along a fiber. Polarization-sensitive optical time-domain reflectometry (POTDR), which is a simple technique based on Rayleigh-scattered polarized light, has been developed [2–4], and its applicability to local birefringence (the beat length) measurement over a long distance has been demonstrated. However, POTDR has lower spatial resolution and longer measurement time. Polarization-sensitive optical frequency-domain reflectometry (POFDR) is also a technique for measuring the beat * Heeyoung Lee hylee@shibaura‑it.ac.jp 1
College of Engineering, Shibaura Institute of Technology, Tokyo 135‑8548, Japan
2
Institute of Innovative Research, Tokyo Institute of Technology, Yokohama 226‑8503, Japan
3
Faculty of Engineering, Yokohama National University, Yokohama 240‑8501, Japan
length distributions with extremely high resolution [5–7], but the measurement range was strictly limited. As another approach, the polarization dependence of Brillouin scattering has also been used to measure the beat length distributions along optical fibers [8–10]. Using a method based on Brillouin optical correlation-domain analysis (BOCDA) [11–15], a high spatial resolution of 2.7 cm was achieved [8]. However, light injection to both ends of the fiber under test (FUT) is not convenient in long-range app
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