Fault Tolerant P ON Topologies

Passive Optical Networks (PONs) are generally built on a broadcast, passive physical topology (typically, a bus, star or tree). Such topologies are vulnerable to link failures. This vulnerability is particularly critical in metropolitan network applications, where a street maintenance crew may inadvertently sever a fiber and thus cut off a section of the network. In this paper we propose a redundant, tree structured PON configuration which can withstand all single and most double link failures. The redundant configuration results from the superposition of two physically separate, diverserouted trees. This redundancy is transparent to the user.