A time-domain extended gaussian noise model

From first-order perturbation theory, we derive the autocorrelation function of the nonlinear interference in coherent optical links. We show that the fundamental assumptions of the Gaussian noise (GN) model regarding stationary Gaussian statistics of the transmitted signal can be removed for a more complete model accounting for the fine details of the cyclostationary modulation format. We first give an intuitive presentation of the theory, and then provide a formal mathematical treatment based on symbol cumulants and discuss its key assumptions and limitations. The proposed model includes dual polarization effects, wavelength-division multiplexing and the nonlinear signal to amplified spontaneous emission noise interaction along the line, thus neglecting only the impact of four-wave mixing.