Investigation of duobinary modulation implementations for use in wavelength switched networks

We investigate the use of different duobinary modulation implementations in a wavelength-switched network operating at 10 Gb/s. The work specifically focuses on two methods of generating duobinary: phase shaped binary transmission (PSBT) which uses both a phase modulator and a Mach-Zehnder modulator (MZM) and enhanced PSBT (EPSBT) which uses two MZM's. We evaluate the benefit associated with modifying the extinction ratios of both implementations in order to optimise the signal for either short- (low back-to-back penalty) or long-distance transmission (good dispersion tolerance). The tolerance of these implementations to impairments associated with the settling of tunable lasers <;200 ns after switching (such as wavelength error and linewidth broadening) are also investigated and the associated penalties are found numerically.