Impact of group-delay ripple in transmission systems including phase-modulated formats

We derive an analytic expression for the signal distortion that results from the effects of group-delay ripple (GDR). When reduced to its simplified first-order form, our expression provides a clear physical picture of how the signal is affected by the ripple period, magnitude, and how the mean signal frequency is located with respect to the ripple peaks. We also find the optical signal-to-noise ratio penalty associated with the ripple to be dependent on the phase relationship among the signal bits. Particular analysis on the impact of GDR in differential phase-shift keying transmission is presented.