Statistical Method for Multi-Path Interference Detection in IMDD Optical Links

With millions of optical links deployed in a typical Data Center (DC) network, telemetry is becoming increasingly important, especially as the number of links and transmission bandwidths rise over time. Multi-path interference (MPI) arising out of multiple optical reflections from fiber connectors, transmitters and receivers is one optical impairment that has been known to cause performance degradation of links in the DC. Through monitoring the statistics of each pulse amplitude modulation (PAM) level at the receiver, we propose and experimentally demonstrate a digital signal processing (DSP) based method to detect the presence of a high level of MPI in intensity modulation direct detection (IMDD) networks. Having this information at hand, the fiber path can be cleaned before an optical link is degraded or fails, which can prevent misdiagnosis and can save time and effort spent on triaging after failure.