The Coherent Polynomials Closed-Form Model for Evaluating Nonlinear Interference in Any Island

Abstract

We improve the accuracy of the GN Polynomial Closed-Form Model (PCFM) by incorporating the spectral NLI PSD and the coherent accumulation along the link. The proposed model is capable of accurately evaluating the NLI over any rectangular integration domain without relying on the machine-learning correction factors, even in low-dispersion and low-baud-rate subcarrier systems.

This paper is a follow-up to P. Poggiolini, Y. Jiang, Y. Gao, F. Forghieri, "Polynomial Closed Form Model for Ultra-Wideband Transmission Systems," in Journal of Lightwave Technology, 2026, doi: 10.1109/JLT.2026.3678322