This work studies games with coupled constraints in general topology optical wavelengthdivision multiplexed (WDM) networks towards optimizing channel optical signal-to-noise ratio (OSNR). We first develop a model to describe the network and an OSNR model for each link by investigating the interaction between the network and physical layers. The nonlinear threshold is considered as the link capacity constraint and we study the case in which channel powers are adjustable at optical switching nodes (e.g., optical cross-connects (OXCs)). An OSNR Nash game is formulated with coupled utilities and constraints, in which each player (channel) maximizes its own utility function related to minimizing its individual OSNR degradation. We exploit this OSNR Nash game in three types of network topologies: multi-link topology, quasi-ring topology and general topology. A hierarchical decomposition approach leads to a lower-level game for channels with no coupled constraints and a higherlevel optimization problem for the network. Computation of equilibria based on this hierarchical algorithm is discussed and evaluated by simulation for each of the three network topologies. & 2013 Elsevier Ltd All rights reserved.