Spectrum Assignment constraints for improved OSNR in optical networks with dynamic traffic

In dynamic-traffic Wavelength Division Multiplexing (WDM) networks, it is desirable to guarantee each optical circuit a minimum Optical Signal-to-Noise Ratio (OSNR) throughout the circuit's entire lifetime. The objective of this paper is to increase such guaranteed OSNR, which in turn enables bandwidth-efficient modulation formats to be applied to the circuit signals. The guaranteed OSNR is improved by applying OSNR-driven Spectrum Assignment (OSA) constraints to each fiber link in the network, based on its forecast traffic volume (offered load). Applying OSA constraints to fiber links has two conflicting outcomes. On the one hand, circuit requests may experience higher blocking probabilities due to the lack of usable spectrum. On the other hand, the adverse effects of medium nonlinearity may be contained, thus yielding improved circuit OSNR. Two OSA constraints are described and their favorable impact on circuit OSNR (up to 2.75 dB gain) is estimated by using a Gaussian Noise (GN) model and an event-driven simulation of two WDM networks supporting dynamic circuits.