400-Gb/s Single-Photodiode Polarization-Agnostic Kramers–Kronig Reception of Distributedly Aggregated Superchannel

In its most simple implementation, the Kramers-Kronig (KK) scheme allows the reception of complex modulation formats with a single photodiode. Thereby, in analogy to a heterodyne receiver, an additional continuous wave signal is used that allows under certain conditions the distortion-free reconstruction of the data signal. We present experimental investigations on a novel KK scheme based on inherently polarization-aligned KK carrier generation at the receiver. We use a distributed superchannel aggregation scheme to demonstrate the ultra-wideband single-photodiode reception of a 3 × 33-GBd single-polarization 32 quadratic-amplitude modulation superchannel with this scheme. The impact of polarization rotations is discussed, and we show that variations in data or KK carrier polarization will only affect the carrier-to-signal power ratio (CSPR), leading to an increase or decrease from the optimum CSPR by about 6 dB. A net capacity of 400 Gb/s is demonstrated for optimized conditions. In addition, we demonstrate transmission measurements over a 60-km standard single-mode fiber link with a 344-Gb/s net rate superchannel (3 × 28 GBd sub-carriers) with the novel KK scheme.