Abstract

Wavelength Division Multiplexed (WDM) networks that route optical connections using intel ligent optical cross-connects (OXCs) is firmly established as the core constituent of next generation networks. With connection rates reaching tens of Gigabits/s, preventing and repairing failures is increasingly becoming an integral part of the network design process. In this work we consider two categories of end-to-end path restoration as supported in Tellium Aurora Optical Switch™ (see also [1]).* In end-to-end dedicated (1 + 1) mesh protection (Figure 1), the ingress and egress OXCs of the failed connection attempt to restore the signal on a predefined backup path that is disjoint, or diverse, from the primary path. Path diversity guarantees that primary and backup paths will not simultaneously succumb to the same failure. This approach requires large amount of capacity, that is more than the working capacity since backup paths are longer than working paths. However the backup path remains “live” in permanence, thus saving crucial path-setup latency when recovery takes place. In shared mesh restoration (Figure 2), backup paths can share capacity if the corresponding primary paths are mutually diverse. Compared to dedicated (1 +1) mesh protection, this scheme allows considerable saving in terms of capacity required.¹ In addition, the backup resources can be utilized for lower priority pre-emptible traffic in normal network operating mode. However recovery is slower than dedicated (1 + 1) mesh protections, essentially because it involves signaling and path-setup procedures to establish the backup path. In particular, we note that the restoration time will be proportional to the length of the backup path and the number of hops, and if recovery latency is an issue this length must be kept under acceptable limits. However this constraints may increase the cost of the solutions, as it is sometime more cost-effective to use longer paths with available shareable capacity than shorter paths where shareable capacity must be reserved.

© 2002 Optical Society of America