Control for Suppression of Channel Power Excursions in ROADM-Based WDM Chain Networks

This paper addresses the problem of reducing power excursions in amplified wavelength division multiplexed networks with reconfigurable optical add-drop multiplexers (ROADM) and wavelength selective switches (WSS). In dynamic network loading scenarios, conventional WSS control leads to transient power excursions across the chain. Two WSS control strategies are considered: an integral-control and a modified integral-coordinated control for tracking. For both algorithms, convergence at an isolated node is shown to depend on the optical amplifier nonlinear gain coupling quantified by its Lipschitz constant. In a chain network with independently controlled ROADM nodes, the modified WSS control effectively decouples the nodes and reduces WSS transient power excursions across the chain. The bounds on these reductions are quantified analytically with respect to the L₂ norm, by applying Lyapunov analysis techniques for the interconnected chain system. Numerical results that verify and compare the two WSS control strategies are provided by implementation on a Transparent Optical Mesh (ATOM) platform for two realistic dynamic network loading scenarios.