Optical duobinary format from demodulation of DPSK using athermal delay interferometer

We experimentally demonstrate the transformation of 42.7-Gb/s optical differential-phase-shift-keyed signals into high-quality duobinary signals by optical filtering in an athermal delay-interferometer (DI) filter. The resulting duobinary signals have good back-to-back performance and show high tolerance to chromatic dispersion and concatenated optical filtering. The repetitive passbands of the DI provide simultaneous transformation of multiple 42.7-Gb/s channels on a 50-GHz ITU grid. The passbands are wide enough not to affect 10.7-Gb/s channels, thereby also allowing hybrid-rate 50-GHz-spaced wavelength-division-multiplexed transmission using a single DI at the system input