Robustness of Quality of Transmission estimators for IC-RWA to uneven channel powers in core optical networks

The quality of transmission (QoT) estimators, envisaged to optimize the impairment constraint routing and wavelength assignment (IC-RWA) in optical transparent networks, are often assessed in a steady configuration by means of re-circulation loops and/or transmissions simulations. In such context the powers of the WDM channels are regularly fixed to a given set of values related to a given point of the periodical transmission. But in installed systems these powers may become uneven, for instance because of the imperfect flatness of optical amplifiers gains over the band occupied by the transmitted WDM comb. In such a frame of a most realistic channel power evolution, this paper investigates the predictions accuracy of a QoT estimator in terms of non-linear effects impact. Hence, we achieved transmission simulations of 50 GHz-spaced channels over several network sections featuring optical amplifiers with no perfectly flat gain. Despite such feature, it appears that the non-linear phase remains a well suited parameter to characterize the penalties induced by the non-linear effects provided that the channel powers excursion remains in the range [-1 dB, 1 dB].