Convergence of the chirped return-to-zero and dispersion managed soliton modulation formats in WDM systems

We investigated chirped return-to-zero (CRZ) and dispersion-managed soliton (DMS) formats that have been employed in experimental demonstration systems at Tyco, CNET, and KDD. We find that the DMS format and the CRZ pulse format used in these systems have been converging. By careful study of noise effects, single-channel nonlinear effects, and multichannel nonlinear effects, we provide evidence that these systems all operate in a quasi-linear region. In this regime, the pulse shape evolution is dominated by linear dispersion and the spread in the eye diagrams is dominated by signal-spontaneous beat noise, much as would be the case in a linear system. However, it is necessary to carefully manage the nonlinearity in these systems to minimize timing jitter due to interpulse interactions in a single channel, as well as interchannel interactions. Thus, nonlinearity plays an important role in system design.