Distribution drop fiber in-service fault management in enhanced EPON system

Ethernet passive optical network (EPON) is considered one of the best candidates for next-generation optical access solutions. Practical and cost-effective survivability and maintenance mechanisms are therefore becoming the key issues for continued development of viable EPON solutions. In addition, 80% of faults occur within the first/last mile. Therefore, in this paper, we propose in-service integrated fault management mechanisms at the distribution drop fibers (DDFs) in EPON. The proposed mechanisms can automatically detect and identify any signal anomalies and DDF faults in the physical layer, thus decreasing the operating expense (OpEx) to be incurred in sending off technicians in the field. The mechanisms are two-fold: pre-fault and post-fault. In the pre-fault mechanism, we use optical receiver type/length/value (TLV) code as a sensor for triggering the embedded miniaturized optical-time-domain reflectometry (OTDR), placed at optical network units (ONUs). This mechanism observes and measures the abnormal condition and reports it to the optical line terminal (OLT), via restoration plan fiber link. In post-fault mechanism, we divide the ONUs into several restoration groups (RGs) to guarantee upstream transmission of the affected ONUs. Lastly, the fault dynamic bandwidth allocation for fault management, referred as FDBA, is presented. Simulation results show that the proposed mechanisms can withstand DDF faults without any significant impact on the overall quality of service (QoS) performance, in terms of mean packet delay, queue length, system throughput, and packet loss.