A Simple and Effective Closed-Form GN Model Correction Formula Accounting for Signal Non-Gaussian Distribution

Abstract

Abstract-The GN model of non-linear fiber propagation has been shown to overestimate the variance of non-linearity due to the signal Gaussianity approximation, leading to maximum reach predictions for realistic optical systems which may be pessimistic by about 5% to 15%, depending on fiber type and system set-up. Analytical corrections have been proposed, which however substantially increase the model complexity. In this paper we provide a simple closed-form GN model correction formula, derived from the EGN model, which we show to be quite effective in correcting for the GN model tendency to overestimate non-linearity. The formula also permits to clearly identify the correction dependence on key system parameters, such as span length and loss.

A Closed-Form Approximation of the Gaussian Noise Model in the Presence of Inter-Channel Stimulated Raman Scattering

“…This significantly simplifies the modeling of NLI in optical mesh networks as fiber spans are variably loaded. The approach is consistent with the observations in [22], [33].…”

“…Closed-form approximations, that predict the nonlinear interference power in coherent transmission systems, were derived for lossless fibers [3], [17] and lossy fibers using lumped amplification [13], [18]- [22] as well as for distributed Raman amplified links [23].…”

A Modulation Format Correction Formula for the Gaussian Noise Model in the Presence of Inter-Channel Stimulated Raman Scattering

“…In the case of of QPSK, only the channel of interest exhibits Gaussian modulation for validation purposes. For comparison the result of [21,Eq. (1)] is shown, which proposed a modulation format correction formula in the absence of ISRS.…”

“…In the approach taken in this work, only the most dominant contribution, the cross-phase modulation contribution, is taken into account. It has been shown that this approach is sufficiently accurate with only a minor loss in accuracy [21], [24]- [27]. The approach is particularly accurate in high dispersive fibers such as standard single mode fiber (SMF) and systems with high symbol rates or channel spacings.…”

A Simple Nonlinearity-Tailored Probabilistic Shaping Distribution for Square QAM

“…For the nonlinear fiber channel, a different distribution can achieve better performance in reach and throughput. In this work, we include the constellation excess kurtosis induced signal-to-noise ratio (SNR) gain; i.e., that the constellation shape can reduce the nonlinear interference, as analytically predicted by [5][6][7]. This method yields distributions that introduce less nonlinear interference than a MB distribution and more importantly outperform it in terms of mutual information, as demonstrated in [8].…”