Optical pi/2-DPSK and Its Tolerance to Filtering and Polarization-Mode Dispersion

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