The purpose of this example is to demonstrate the dispersion-managed soliton regime in a fiber link with loss and periodical amplification. Ideal lossless and loss-managed solitons require GVD parameter beta2 to stay constant along the fiber length. Modern WDM lightwave systems employ dispersion management to compensate for cumulative dispersion and to suppress FWM penalties. It was demonstrated that solitons can form even when beta2 varies along the fiber length but their properties are quite different. This kind of solitons is called dispersion-managed solitons.
The figure below demonstrates the layout to study dispersion-managed soliton regime in a long-haul fiber link. It represents the circulating loop setup, where each loop is consist of six regular fiber spans, one dispersion-compensating fiber (DCF) span, optical filter and seven optical amplifiers - EDFAs, with total loop length about 180 km. Pulse will travel total 100 loops or 18,000km.