Increasing the Efficiency of Span-restorable Mesh Networks on Low-connectivity Graphs

We propose a refinement to existing methods for span-restorable mesh capacity design to increase the capacity efficiency on sparse facility graphs. The resultant designs comprise a special class of restorable network that is intermediate between pure span restoration and path restoration. Most of the efficiency of path restoration is achieved by targeting chain sub-networks that ordinarily require ring-like spare capacity under span restoration but restoration in the new networks continues to require only a span restoration mechanism, which is potentially faster and simpler than for path restoration. The new approach views a network that has a low average nodal degree as a meta-mesh of chain sub-networks. The meta-mesh graph is a homeomorphism of the complete network in which edges are either direct spans or chains of degree-2 nodes. The main advantage is that loop-back type spare capacity is provided only for the working demands that originate or terminate in a chain, not entire flows crossing chains. The latter “express” flows are entirely mesh-protected within the meta-mesh which is of higher average nodal degree and hence more efficient for mesh restoration than the network as a whole. Additionally only the meta-mesh nodes need optical cross-connect functionality. Degree-2 sites require only OADMs or glass-throughs. OADMs having a passive waveband pass-through feature may be especially well suited to support the express flow of meta-mesh protected demands through the chain sub-networks.