Protection of Inter-ONU Connectivity in Advanced PON with Minimum Trenching Cost

High-capacity and low-cost Passive Optical Network (PON) is a competitive solution for demanding applications that require low latency and high availability (e.g., 5G fronthaul). Recent proposals show that strict latency requirements can be satisfied by directly connecting Optical Network Units (ONUs) through the Remote Node, in an architecture called Advanced PON. To ensure high reliability of inter-ONU connections against fiber cuts, in this paper we propose two protection schemes that implement path protection and link protection in the context of advanced PONs. Our numerical results show that path protection requires (4-13)% more trenching to place spatially disjoint backup fibers compared to link protection, but might still be practical because of lower equipment complexity.