Centralized monitoring and fault localization for passive optical network

A real-time, centralized and cost efficient monitoring and fault localization system is presented. In this system, a superluminescent diode (SLED) is used as the monitoring signal and the signal is reflected by using different types of fiber Bragg gratings (FBGs); uniform and phase-shifted FBGs as branch identifiers. We demonstrate the enhancement of monitoring wavelength whereas for a distinct center wavelength, it represents the reflection spectrum of two types of FBG or two branches in the network. Thus, more optical network units (ONUs) can be monitored for the specific monitoring source with limited bandwidth. The system is capable to monitor up to 64 ONUs with BER of 10^-15.