Fault detection of few-mode fiber based on high-order mode with high fault detection sensitivity

We report on the fusion splice loss characteristics of each mode in few-mode fiber (FMF). The fusion fault loss characteristics of all modes of the six-mode step-index and graded-index fibers are measured, respectively. The high-order modes with high fault detection sensitivity are presented. The fault events with different loss amplitudes can be accurately characterized by high-order modes. On this basis, a fault detection and location method for FMF based on backscattered light of high-order modes is proposed and experimentally demonstrated. Rayleigh backscattering light of high-order modes is utilized to detect the faults of 7.2 km six-mode step-index fiber with three fusion splice points with different fusion quality, the detection results of each mode are compared. The high-order modes LP21a, LP21b, and LP02 with high fault detection sensitivity are shown, three fault points located around 1.03, 3.1, and 3.2 km of the FMF are successfully detected. While the LP01, LP11a, and LP11b modes can detect only one fault point, which is located around 3.19 km of the FMF.