Suppression of spurious tones in fiber system simulations based on the split-step method

The most commonly used algorithm in fiber systems simulation is the Split-Step Method (SSM). It is based on the partition of fiber spans into steps. At each step, the nonlinear (Kerr effect) and linear (dispersion) operators of the Nonlinear Schrodinger Equation (NLSE) are applied separately. A smaller step-size induces a better accuracy, but increases computational time, thus a trade-off between these two opposite requirements must be found. The simulation artifacts induced by a wrong step-size choice should first be characterized, then a law to keep them under control must be found. The SSM may generate spurious Sideband Instability (SI) and Four-Wave Mixing (FWM) tones. The artifacts are shown for the case of simulation with Uniform Step-Size Distribution (USSD). The novel method we present is based on a Logarithmic Step-Size Distribution (LSSD), and its originality is the quantitative control on the induced artifacts.