Soliton stability against polarization-mode-dispersion in the split-step system

We consider polarization dynamics of solitons in the split-step system (SSM), built as a periodic concatenation of dispersive and nonlinear segments. The model is based on coupled equations for two polarizations, which include birefringence and PMD (polarization-mode dispersion) in the form of random misalignments of the principal polarization axes at junctions between fiber segments. By means of direct simulations, we identify a full stability region for solitons (RZ signals) in the system, and compare it with that in the regular SSM. Beyond the stability border, pulses suffer splitting (which is a characteristic feature of the SSM). Considering co-transmission of soliton pairs, we conclude that the minimum separation between the RZ signals necessary to prevent their interaction increases by ≃25% in comparison with the regular (single-polarization) SSM.