Nonlinear response of the semiconductor pre-amplifier in next generation 400 Gb/s ethernet 40-km transceivers

The nonlinear response of a bulk semiconductor optical pre-amplifier in a 16 × 25 Gb/s WDM implementation for the next 40-km Ethernet link, operating at 400 Gbps is numerically analysed. It is found that the effect of carrier-heating-induced four-wave mixing for channel spacing values between 200 and 800 GHz is rather modest despite the large number of optical channels. In contrast, cross-gain modulation is uncovered as the main impairment, and its dependence on the system channel-spacing value is quantified and explained in terms of the interplay between amplifier saturation and fibre dispersion. Useful design parameters for the optoelectronic transceivers, operating at 25.781 Gb/s in traditional on-off keying scheme, are put forward.