Reconfiguration phase in rearrangeable multihop lightwave networks

A lightwave network consisting of geographically distributed access stations that communicate over a fiber infrastructure is considered. The access station electro-optic transceivers tap directly into the optical medium and transmit/receive on different wavelengths, thereby creating wavelength multiplexed channels that form a logical connection diagram among the stations. Such lightwave networks have the ability to superimpose a variety of logical connection diagrams, or virtual topologies, on top of the underlying optical infrastructure by proper assignment of transmit and receive wavelengths to the network stations. Furthermore, the use of transmitters and receivers that are tunable over a large portion of the optical band allows the network to be dynamically reconfigured. The connection diagram could thus be updated in response to changing traffic patterns and failure/recovery of access station equipment. Potential applications of rearrangeable lightwave networks range from a distributed ATM switch with traffic changing continuously as calls are established and terminated, to metropolitan or wide area networks with slowly changing traffic patterns. In the distributed switch, reconfiguration may occur frequently, and a new connection diagram would be sought each time a new call cannot be accommodated by the switch and would otherwise be rejected. In the wide area network setting, reconfiguration would take place less frequently as the expected traffic pattern slowly and predictably changes over time. This paper describes practical approaches for the reconfiguration phase, during which the network connection diagram is changed from an initial to a final configuration.