Shaping NRZ pulses and suppression of the inter-symbol interference by a second-harmonic-generating module

Soliton Management in Periodic Systems

“…This possibility was first proposed, in a rather abstract form, in work [139], and was further developed in papers [78,54], where it was demonstrated that SHG modules can be used to generate an effective negative Kerr effect (through the so-called cascading mechanism, i.e., repeated action of the corresponding quadratic nonlinearity), which will play the compensating role. The NLM model is described by equation (1.48), in which both (3{z) and 7(2) periodically jump between positive and negative values.…”

“…Dissipative attenuation of the signal inside the SHG crystal and the GVM between the FF and SH signals are not included, as both are negligible for relevant propagation lengths. Nevertheless, the model does imply that the GVM must be zero (or very small), which turns out to be necessary for a different reason: as demonstrated in work [78], a condition tantamount to the zero GVM provides for equalization of the phase-velocity mismatch across channels in the WDM system. The propagation of the signal in the fiber spans (with altering sign of the GVD coefficients, to provide for the dispersion compensation) obeys the ordinary NLS equation (1.48) for the field u{z, r) in the DM system.…”