Pump-probe analysis of the cross-phase modulation degradation induced by 10 Gbit/s amplitude-shift-keyed signals on 40 Gbit/s DPSK signals

A study of the cross-phase modulation (XPM) degradation of differential-phase-shift-keyed (DPSK) signals due to amplitude-shift-keyed signals is performed using pump-probe simulation. Approximate expressions for the contributions of the XPM-induced intensity and phase modulation to the electrical current fluctuations at the differential-phase-exchange-keyed receiver are presented. It is shown that, unlike prior works and similar to intensity-modulated signals, the contribution of XPM-induced intensity modulation is dominant in systems using standard fiber or high residual dispersion.