Nonlinear impairments in extremely dense WDM systems

The capacity of current optical transmission systems could be greatly increased by using extremely dense wavelength-division-multiplexing. We show that this technique could suffer from enhanced interchannel interactions because of the very low frequency spacing. Considering 10-Gb/s channels with 12.5-GHz spacing, significant impairments can arise both in nonzero dispersion fiber and conventional single-mode fiber links. The effect is ascribed to cross-phase modulation, and could be partially mitigated by a proper dispersion map.