Routing and wavelength assignment computed jointly for a given set of multicast trees reduces the total wavelength conversion

A significant drawback when establishing multicast optical trees (light-tree) using lambda channels in wavelength division multiplexing (WDM) network is the potentially large amount of wavelength converters (WCs), which are required when the wavelength continuity constraint cannot be satisfied across each light-tree. Prior works address this challenge by solving the routing and wavelength assignment (RWA) problem for each individual light-tree sequentially, to locally minimize the number of WCs required by each light-tree. In this paper, the authors intend to solve the RWA problem for a group of light-trees with the objective of globally minimizing the number of WCs that are required to support the entire group of multicast requests. The rationale for using the proposed RWA solution is that a joint solution of the RWA problem across the whole set of requested multicast trees may significantly reduce the number of WCs overall.