Optical Duobinary Format from Demodulation of DPSK using Athermal Delay Interferometer

We experimentally demonstrate the transformation of 42.7-Gb/s optical DPSK signals into high-quality duobinary signals by optical filtering in an athermal delay-interferometer filter. The resulting duobinary signal has good back-to-back performance and also shows high tolerance to chromatic dispersion and concatenated optical filtering. The repetitive passbands of the filter provide simultaneous transformation of multiple 42.7-Gb/s channels on the ITU grid without affecting 10.7-Gb/s channels, thereby allowing hybrid-rate wavelength-division-multiplexed transmission with 50-GHz channel spacing.