NIT-NL · Network Information Theory for NonLinear optical channels

Optical fiber systems carry nearly all of the global Internet traffic and are critical infrastructure for modernsociety. Long-haul optical networks are often based on the notion of wavelength division multiplexing (WDM). Athigh signal intensities, WDM systems are impaired by the inherent nonlinear effects involved in fiberpropagation. In the literature, the fundamental limits of WDM transmission are investigated using informationtheory. The prevalent viewpoint only focuses on achievable rates for individual users under different behavioralassumptions for the interfering users. NIT-NL deviates significantly from this single-user viewpoint and proposesa multi-user information theoretic approach for the WDM channel that investigates the region of simultaneouslyachievable rates for all the different users. NIT-NL aims to exploit this holistic perspective and realize a moreefficient utilization of the optical network resources. This will be achieved via a) characterization of closed forminner and outer bounds to the capacity region based on realistic channel models, b) asymptotic analyses in thelimit of high transmit power to infer the nature of optimal strategies in the highly nonlinear regime, and c)derivation of optimality conditions for simple and practical schemes such as treating interference as noise toachieve the sum-capacity of the given model. NIT-NL will have a direct impact on the scientific communityengaged in the long-standing quest of dealing with nonlinear impairments in optical channels, and the multi-userinformation theory community that will welcome its enrichment on nonlinear channel models. It will also benefitthe European telecommunications industry and standardization initiatives.