A GN-model closed-form formula considering coherency terms in the Link function and covering all possible islands in 2-D GN integration

Efficient evaluation of nonlinearity in modern coherent optical telecommunication networks is necessary for design, optimization and management. The original GN model formula can not be used in real time applications due to long processing time needed for numerical 2-D integration, particularly when facing with full C band or C+L band. There are closed form approximations of the GN model which has been mathematically derived based on some assumptions which fail in low dispersion regime. In this work, we derive a GN closed form formula without any restrictive assumption capable of handling arbitrary WDM combs and arbitrary link structures in closed form which can be used with a very good accuracy with respect to original GN formula for networks employing both high and low dispersion fibers.