Cross-phase Modulation-induced crosstalk for RZ-DPSK signals in dispersive transmission systems

In highly dispersive return-to-zero differential phase-shift keying (RZ-DPSK) transmission systems, the overlap of optical pulses gives a nonperiodic optical intensity that induces nonperiodic phase modulation to adjacent channels through cross-phase modulation (XPM). The variance of the differential phase induced by XPM and pulse overlap is derived analytically. The impact of pulse overlap is smaller for a system using short RZ optical pulses. For two adjacent channels without spectral overlap, the standard deviation (STD) of XPM-induced phase shift is approximately inversely proportional to the channel separation.