Study on cross-phase modulation (XPM) effect on amplitude and differentially phase-modulated multilevel signals in DWDM transmission

The characteristic degradation mechanism of the cross-phase modulation (XPM) effect on multilevel amplitude and differentially phase-shift keying (APSK) signals in dense wavelength-division-multiplexing (DWDM) transmissions is analyzed and experimentally investigated, for the first time. Based on the results, we successfully demonstrate a 0.48-Tb/s (30-Gb/s/ch) 50-GHz-spaced 16-channel DWDM 160-km unrepeatered transmission of eight-level APSK signals suppressing the XPM-induced degradation.