Résumé
Multicast routing in all optical WDM networks where the light splitting capacity of some optical switches is limited is an important problem. The computation problem of the minimum cost multicast routes under optical constraints is NP-difficult. To solve the optimal multicast routing problem under physical constraints, we propose a new routing structure called 'light-hierarchy''. In a light-hierarchy, the multicast route can traverse the same optical switch several times using the same wavelength. This new routing structure may improve both the cost of the optical structures and the throughput on WDM multicast networks.