Recent progress in slope-assisted Brillouin optical correlation-domain reflectometry

Brillouin optical correlation-domain reflectometry (BOCDR) is one of the fiber-optic Brillouin-based distributed sensing techniques for strain and temperature with single-end accessibility. Since the first proposal of the basic concept in 2008, the performance of BOCDR has been drastically improved from a variety of aspects including high-speed operation. Here, we focus on one of the high-speed BOCDR configurations referred to as slope-assisted (SA-) BOCDR. In this configuration, instead of observing the whole Brillouin gain spectrum, only the spectral power at a certain frequency on the spectrum is detected, leading to frequency-sweep-free high-speed operation and some unique features. In this review paper, we describe the recent advances of SA-BOCDR technology from its principle to characterization and applications. We also discuss the current issues of SA-BOCDR and present a concluding remark.