Reduced-bandwidth duobinary differential continuous-phase Modulation format for optical communications

We demonstrate a new modulation format based on differential phase-shift keying (DPSK) with a duobinary-shaped modulating signal for applications in optical communications. Compared to conventional DPSK and using the 20-dB full-width criterion, numerical and experimental data show a bandwidth reduction by a factor of two resulting in a better tolerance to group-velocity dispersion but at the expense of a back-to-back sensitivity degradation of 3.5 dB.