40-Gb/s DBPSK and DQPSK Formats for Transparent 50-GHz DWDM Transmission

Today's dense wavelength division multiplexed (DWDM) long haul and metropolitan networks are being upgraded from 10-Gb/s to 40-Gb/s, to support the growing traffic demands. Reconfigurable add/drop multiplexers (ROADMs) allow for transparent networking at 50-GHz channel spacing. This paper addresses the challenges to support 40-Gb/s by examining two promising modulation formats, namely differential binary and quadrature phase shift keying (DBPSK and DQPSK). We investigated several variants of the two formats and present performances under optical filtering, crosstalk and polarization mode dispersion. We also discuss ROADM node architectures that have bearing on overall system performance.