Fault detection performance of a multi-mode transmission reflection analysis for a few-mode fiber link

We propose a novel monitoring technique based on multi-mode transmission reflection analysis for a long-reach few-mode fiber (FMF) based mode division multiplexing system. By launching unmodulated continuous-wave optical light modes into the corresponding spatial modes of the FMF, the transmitted and reflected or backscattered optical powers can be measured and quantitatively analyzed to accurately characterize and locate the fault. The influences of the capture fraction, attenuation coefficient, and Rayleigh backscattering coefficient are discussed, and simulation results show that the proposed method can realize the fault location of the FMF link. Moreover, considering the influence of mode crosstalk on localization accuracy, it is clear that using the monitoring combination modes LP₀₁ and LP₂₁ gives a high precision of 3.58 m.