Using fiber with negative dispersion and electro-absorption modulator to alleviate both dispersion- and nonlinearity-induced penalties

The proper combination of source linewidth enhancement factor (alpha) through electro-absorption modulator (EAM) and fiber dispersion coefficient D in wavelength division multiplexed (WDM) optical transmission systems can greatly extend the dispersion-limited system regeneration length Lreg (up to 70% for a 16 X 10 Gb/s X 400 km system). Four-wave-mixing-induced power penalty will only slightly increase due to the none-zero fiber dispersion, although more Erbium-doped fiber amplifiers are needed to compensate for the fiber attenuation. This scheme can also effectively suppress the modulation instability and self-phase modulation, etc. In general, when dispersion management or dispersion compensation measures are adopted for WDM systems using EAM with positive (alpha) , slightly over-compensation the fiber dispersion for all channels can effectively extend Lreg or reduce the dispersion-induced eye opening penalty if fiber nonlinearities remain tolerable.