Abstract
The GN-model has been proposed as an approximate but sufficiently accurate tool for predicting uncompensated optical coherent transmission system performance, in realistic scenarios. For this specific use, the GN-model has enjoyed substantial validation, both simulative and experimental. Recently, however, it has been pointed out that its predictions, when used to obtain a detailed picture of non-linear interference (NLI) noise accumulation along a link, may be affected by a substantial NLI overestimation error, especially in the first spans of the link. In this paper we analyze in detail the GN-model errors. We discuss recently proposed formulas for correcting such errors and show that they neglect several contributions to NLI, so that they may substantially underestimate NLI in specific situations, especially over low-dispersion fibers. We derive a complete set of formulas accounting for all single, cross, and multi-channel effects, This set constitutes what we have called the enhanced GN-model (EGN-model). We extensively validate the EGN model by comparison with accurate simulations in several different system scenarios. The overall EGN model accuracy is found to be very good when assessing detailed span-by-span NLI accumulation and excellent when estimating realistic system maximum reach. The computational complexity vs. accuracy trade-offs of the various versions of the GN and EGN models are extensively discussed.
Highlights
Building on results from several similar prior modeling efforts [1,2,3,4,5], the GN-model of nonlinear fiber propagation has recently been proposed [6,7,8,9,10,11,12,13,14]
In particular in [22], the first peer-reviewed published paper on the subject, we presented for the first time a detailed picture of the predicted and actual non-linear interference (NLI) noise variance accumulated along realistic links based on polarization-multiplexed (PM) QPSK and PM16QAM
In this paper we adopt a similar approach to that indicated in [24] and in Sect. 3 we provide for the first time the GN-model ‘correction terms’ for single-channel non linearity, which was not addressed in [24]
Summary
Building on results from several similar prior modeling efforts [1,2,3,4,5], the GN-model of nonlinear fiber propagation has recently been proposed [6,7,8,9,10,11,12,13,14]. The GN-model main purpose has declaredly been that of providing a simple but sufficiently accurate tool for the prediction of the main system performance indicators in uncompensated l0nks that make use of coherent detection Typical such indicators are maximum reach and optimum launch power. We find that the XPM formulas proposed in [24] may in certain cases substantially underestimate NLI, especially with low-dispersion fibers This circumstance is extensively discussed in both Sect. We point out that, for the purpose of system performance studies, an analytical closed-form GN-model correction formula, based on an approximation of the EGN-model, has been proposed in [26] This approximation adds little complexity to that of the GN-model and substantially improves its accuracy. We call ‘incoherent GN-model’ the simplified GN-model version that assumes incoherent NLI accumulation, described in [14] as Eq (9)
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