| I numerically simulated long-distance, high-bit-rate, wavelength-division-multiplexed transmission in dispersion-managed systems. I investigated chirped return-to-zero (CRZ) and dispersion managed soliton (DMS) formats that have been employed in experimental demonstration systems—including the Tyco-CRZ system [1], [2], the CNET-DMS system [3]–[5], and the KDD-RZ system [6]–[9]—as well as our own system at University of Maryland Baltimore County (UMBC) 10]-[15], Consistent with earlier experiments, I find that the chirped return-to-zero format has significant advantages over the periodically stationary dispersion-managed soliton format in wavelength-division-multiplexed systems. Hence, the dispersion-managed soliton and the chirped return-to-zero pulse formats used in practice have converged toward a quasilinear evolution that is not periodically stationary. I elucidate the physical reasons for these advantages. I will discuss in detail the dynamics of the chirped return-to-zero systems, carefully distinguishing noise effects, single-channel nonlinear effects, and multi-channel nonlinear effects. In this way, I provide a physical basis for understanding chirped return-to-zero systems that should prove useful for future system design. In particular, I find that the pulse evolution is dominated by linear dispersion and that the spread in the eye diagram is dominated by signal-spontaneous beat noise, just like in linear systems, although nonlinearity plays an important role and must be carefully mitigated. |
