Optical /spl pi//2-DPSK and its tolerance to filtering and polarization-mode dispersion

Optical /spl pi//2 differential phase-shift keying (/spl pi//2-DPSK) is a modulation technique which encodes the binary information in relative phase shifts of /spl pi//2 and -/spl pi//2 between adjacent optical pulses. Here, we experimentally demonstrate /spl pi//2-DPSK at the bit rate of 42.7 Gb/s. It is found that /spl pi//2-DPSK outperforms conventional DPSK in the presence of strong optical filtering and polarization-mode dispersion (PMD).