Design strategies and merit of system parameters for uniform uncompensated links supporting Nyquist-WDM transmission

We consider the transmission of Nyquist-wavelengthdivision- multiplexed channels based on polarization-multiplexed m-ary QAM multilevel modulation formats with DSP-based coherent detection over point-to-point uncompensated periodically amplified uniform fiber links. Taking into account both the effect of amplified spontaneous emission noise accumulation and generation of nonlinear interference (NLI) introduced by fiber propagation, we propose three different design strategies: the maximization of both the Q margin and the span-loss margin, for a given span length, and the maximization of the total link length given a target performance. We propose and apply an approximation for the Gaussian-noise model in order to evaluate the NLI intensity, deriving for the three design strategies the merit of link and signal parameters. Finally, we validate the proposed methodologies using experimental and simulative results already published in the literatur