Dispersion-managed Solitons

This chapter provides an overview of dispersion management and dispersion-managed solitons. With dispersion management, the transmission line consists of segments of fiber whose individual dispersion parameters (Dl ocal ) are of alternating algebraic sign: D + local and D - local. Furthermore, this arrangement, or dispersion map, is ideally periodic. For each map period, the accumulated dispersions of the two segments nearly cancel, so that the path-average dispersion parameter of the map, D, is usually much smaller than either: D + local or ׀D - local׀. To support solitons, D is also positive. In response to the relatively large, alternating D local values, the pulse width tends to undergo a large fractional change, periodic with the map. This pulse breathing is accompanied and promoted by a similarly periodic variation in the chirp parameter, with the chirp passing through zero at or near the center of each fiber segment. To obtain dispersion-managed solitons, the pulse intensity must be increased until self-phase modulation produces a phase shift across the pulse that just cancels out the net phase shift produced by the dispersive term within each map period. This periodic cancellation of phase shifts eliminates the net pulse broadening from D, so that the pulse behavior becomes truly periodic.