Polynomial Closed Form Model for Ultra-Wideband Transmission Systems

Ultrafast and accurate physical layer models are essential for designing, optimizing and managing ultra-wideband optical transmission systems. We present a closed-form Gaussian-Noise (GN)/Enhanced-GN (EGN) model, named Polynomial Closed-Form Model (PCFM). The key to deriving PCFM is expressing the spatial power profile of each channel along a span as a polynomial. Then, under reasonable approximations, the integral calculation can be carried out analytically, for any chosen degree of the polynomial. We present a full detailed derivation of the model. We then validate it vs. the numerically integrated GN-model in a 60/100 km challenging multiband (C+L+S) scenario, including Raman amplification and inter-channel Raman scattering. We then show that the approach works well also in the special case of the presence of multiple lumped loss along the fiber. Overall, the approach shows high reliability and broad generality, achieving a generalized Signal-to-Noise Ratio (GSNR) accuracy of nonlinear interference (NLI) within 0.3 dB of the GN-model benchmark. A software implementing the model, fully reconfigurable to any type of system layout, is available for download under the Creative Commons 4.0 License.