On spatially disjoint lightpaths in optical networks

Abstract

The core network in the information communication technology infrastructure is based on the optical fiber technology. The core network is of prime importance because it connects all the central offices in the wired communication networks and the mobile switching centers in the wireless communication networks. The optical link between two network nodes is a lightpath, which offers very high speed, low loss, lower cost, highly reliable, secure and very high capacity, end-to-end communication over a very long distance. Any damage to a lightpath in the event of a disaster may lead to massive service interruptions and financial losses for the network operators. Therefore, survivable routing in these networks is very important. Generally, the survivability is ensured by having a backup lightpath to keep communication intact because the primary and the backup light paths are always disjoint. However, they may still fail simultaneously in the event of a large-scale disaster, if their separation distance in the physical plane is small. Hence, the spatial distance between the disjoint lightpaths should also be taken into consideration when establishing the lightpaths. Our contributions in this paper are twofold: (1) a routing algorithm is proposed for provisioning a pair of link-disjoint lightpaths between two network nodes such that their minimum spatial distance (while disregarding safe regions) is maximized, and (2) another routing algorithm is proposed for provisioning a pair of link-disjoint lightpaths such that the path weight of the primary lightpath is minimized, subject to the constraint that the backup lightpath has some particular geographical distance from the primary lightpath. Through extensive simulations, we show that our first algorithm can provide maximum survivability against spatial-based simultaneous link failures (due to the maximized spatial distance), whereas the second algorithm can tune the spatial distance between the lightpaths keeping in view the target survivability requirements and the path weight for the primary lightpath.