Alternate Multihop Routing in Limited Reconfigurable Optical Networks

In this paper, we investigate the performance of limited reconfigurable optical networks when multihopping is used. Multihopping is achieved by dropping a wavelength at an intermediate node and transmitting on another wavelength at that node (O-E-O). A route can consist of several such hops each obeying the wavelength continuity constraint individually. Considering that a receiver and a transmitter are used for add/drop at a node, multihopping is restricted by the number of transponders and their tunabilities. We develop a dynamic routing strategy based on the availability and tunability of transponders as well as the wavelength availability. We adopt a share-per-link model for the usage of transponders within a reconfigurable node, and each node is assumed to be equipped with a ROADM which can add/drop any wavelength to any of the ports. We show that the proposed routing strategy improves the blocking performance significantly compared to fixed routing with or without multihopping or alternate routing methods without multihopping.