Routing lightpaths in optical mesh networks with express links

Summary form only given. We examined the routing of protected lightpaths in an optical network with express links. To enable diverse routing, shared risk groups (SRGs) are assigned to the express link to be the union of all the SRGs on the underlying links. We examined the cost setting on the express links for routing the primary and backup paths. For routing primary paths, the express link is always preferred over the underlying links. For routing backup paths, the desirability of using express links depends strongly on the traffic demand. We find that biasing the routing of backup paths to mostly use underlying links while allowing express links to be used in some cases performs well in terms of switch ports and bandwidth miles used.