Multi-Path Delay Estimation for IM-DD System by Power Cepstrum

Multi-path interference (MPI) resulting from optical reflections at fiber connectors, transmitters, and receivers is a critical impairment that significantly impacts intensity modulation direct detection (IM-DD) systems. Promptly identifying and pinpointing the root cause of link failures in IM-DD systems is crucial. In this study, we present a method for estimating multi-path time delays in IM-DD systems based on power cepstrum analysis. We outline the fundamental principle of our proposed method and investigate the various factors that may affect the accuracy of the estimated results. Our results demonstrate the robustness of the proposed method against link noise and laser linewidth variations. Additionally, we assess the multi-path delay monitoring capability for systems with more than two paths, revealing that the relative amplitude strength and delay of muti-paths can be effectively monitored. Through experimental validation, we confirm the validity of our proposed method, as the results align well with theoretical and simulation outcomes. This introduces a novel efficient tool that facilitates the diagnosis and localization of failure causes in IM-DD links.