Multiwavelength optical networks with limited wavelength conversion

This paper proposes optical wavelength division multiplexed (WDM) networks with limited wavelength conversion that can efficiently support lightpaths (connections) between nodes. Each lightpath follows a route in the network and must be assigned a channel along each link in its route. The load λ_max of a set of lightpath requests is the maximum over all links of the number of lightpaths that use the link. At least λ_max wavelengths will be needed to assign channels to the lightpaths. If the network has full wavelength conversion capabilities then λ_max wavelengths are sufficient to perform the channel assignment. We propose ring networks with a fixed wavelength conversion capability within the nodes that can support all lightpath request sets with load λ_max at most W-1, where W is the number of wavelengths in each link. We also propose ring networks with selective pairwise wavelength conversion capability within the nodes that can support all lightpath request sets with load λ_max at most W. We also propose a star network with fixed wavelength conversion capability at its hub node that can support all lightpath request sets with load λ_max at most W. We extend this result to tree networks and networks with arbitrary topologies. These results show that significant improvements in traffic-carrying capacity can be obtained in WDM network by providing a very limited wavelength conversion capability within the network