Simulation of performance improvement by fiber nonlinearity in spectrum-sliced WDM systems

Simulation studies show that in spectrum-sliced WDM systems nonlinear bandwidth expansion at the receiver may be used to reduce excess noise while keeping the transmitted optical bandwidth small. This is important because small transmitted bandwidths are important to minimize dispersion effects, and to maximize capacity for a given total bandwidth. The performance improvement can be explained by observing the auto-covariance curves of the photo-detected signal. The optical filter after the nonlinear fiber in NBER makes the covariance curve narrower than that of the input signal, but can cause a rise in the tails if the filter bandwidth is too large. Simulations of auto-covariance and Q-factor indicate that to maximize system performance there is an optimum bandwidth of the optical filter following the nonlinear bandwidth expansion.