Novel modulation formats for high-spectral efficiency optical transmission (Invited Paper)

We present two novel modulation formats, namely, optical differential 8-level phase-shift keying (OD8PSK) and differential polarization-phase-shift keying (DPolPSK) for high-spectral efficiency optical transmission. Both formats are constant-amplitude, tolerant to fiber nonlinearities, especially cross-phase modulation (XPM). Both formats use direct detection without the use of either active polarization control or phase locking at the receiver. DPolPSK also addresses practical use of polarization.