Highly sensitive detection of microbending in single-mode fibers and its applications

This paper investigates the applicability of 1-μm-band mode-detection optical time domain reflectometry (OTDR), which detects microbending in single-mode fibers with high sensitivity by conducting measurements in the two-mode region of the fibers under test and observing the second-order mode of the backscattered light. To demonstrate its feasibility, we evaluate microbending losses as determined by the technique, and comparisons are made with conventional OTDR operating at the wavelength of 1650 nm. In addition, we discuss two potential applications of the technique. One is microbend sensing of fibers and cables for detecting microbending losses that are too small to be found with conventional OTDR. The other is health monitoring of installed fiber cables. This enables us to detect the growth in microbending losses at an earlier stage. Proof of concept is demonstrated experimentally.