Redundant Passive Optical Network (PON)
A single OLT can be equipped with a redundant PON port or PON card serving one ONT with two paths across a redundant optical plant. This PON equipment-level redundancy, from one OLT, is a means to provide fiber route diversity using the FSAN ITU standard Type-B PON redundancy option. Type-B PON redundancy is a purely passive solution, defined in principle by FSAN ITU standards, and is contingent on deploying 2:x Passive Optical splitters. These highly reliable 2:x optical splitters provide both protection, redundancy and splitting functions in the optical plant. CIOs and IT pros have a great amout of flexibility as to where these splitters can be placed in their optical plant infrastructure. For example, the 2:x Passive Optical splitters can either be positioned for centralized (e.g. near the data center) or distributed (e.g. far from the data center) architectures. These 2:x passive optical splitters support a variety of split ratios, including 2:8, 2:16 and 2:32, dependent on the type and number of ONTs being subtended. They can be sourced from major Layer-1 optics manufacturers.
Redundant Optical Line Terminals (OLT)
Two OLTs at geographically dispersed locations can also be configured to serve one ONT with two paths across a redundant optical plant. Because of this, Type-B PON redundancy provides options for fiber route diversity to different PON ports in the same OLT, different PON cards in the same OLT, and different OLTs in geographically dispersed locations. The use of redundant OLTs in two locations represents the pinnacle of reliability being 99.9999%, as six-nines network availability is the culmination of all redundancy options, including dual homing routers, equipment redundancy and Type-B PON redundancy with fiber route diversity and geographically dispersed OLTs.