As the bandwidth and services are evolved drastically in access networks, PON provides a powerful solution to satisfy such the increasing demand. To ensure the security and reliability of PON that monitoring system is necessary during operation, administration, and maintenance. In this paper, the requirements and challenges of optical layer monitoring in PON are discussed, and an extensive and detailed survey of the monitoring techniques and designs is given both for TDM-PON and WDM-PON. Among these proposed PON monitoring system, all of them are still lacking in a complete monitoring functions, and the hybrid design with complementary monitoring functions will be a promising solution for future PON system.
WDM-PON TDM-PON OCDM NMS BLS RSOA ASE ONU OLT RN AWG OTDR OFDR B-OTDR