Distributed generation of a 400-Gb/s Nyquist 16QAM dense superchannel by fiber-frequency conversion

We generate an ultra-dense 400-Gb/s superchannel by combining four spatially distributed 28-GBd-Nyquist-16QAM-sub-carrier transmitters using optical processing in nonlinear fibers. The multiplexed sub-carriers are precisely frequency-allocated with guard bands down to 0% and achieve bit-error ratios below 3.8×10⁻³.