Optimal Design of WDM Ring Networks to Minimize SDH ADMs

In this paper, we study the routing and wavelength assignment in WDM ring network supporting multiple high-level SONET/SDH self-healing rings. The optimal design of ring networks was formulated by using integer linear programming (ILP) and solved numerically. The objective of our optimization is to minimize the number of ADMs (Add-Drop Multiplexer) used in high-level SDH layer, the cost of which is dominant in WDM ring networks supporting SDH services as pointed out recently. For the first time, the impact of route selection and traffic patterns was demonstrated in this paper. Through the extensive numerical simulations, these results of two typical ring network architectures, bi-directional and unidirectional rings, were compared under different traffic patterns. Our simulation results show that proper route selection can result in significant ADMs saving in bi-directional ring network.