C-band 100-Gbaud/λ PAM-4 Transmission Enabled by Hardware-Efficient Nonlinear Equalizer with Weight-Sharing Pruning.

A Volterra nonlinear equalizer (VNLE) can effectively mitigate both linear and nonlinear impairments arising in intensity-modulation direct-detection (IM-DD) transmission systems. However, the high computational complexity of the VNLE hinders its applications. Here, we propose a hardware-efficient Volterra equalizer with weight-sharing pruning (VE-WSP). Such an equalizer first uses the k-means++ clustering algorithm for the weight sharing within the same cluster, and then ranks the cluster centroid weight for pruning, leading to a significant computational complexity reduction without sacrificing any equalization performance. We experimentally verified that the use of VE-WSP can enable the C-band 100-GBaud/λ PAM-4 transmission over a 1-km standard single-mode fiber (SSMF), to reach the 20% soft-decision forward error correction (SD-FEC) threshold. Meanwhile, the proposed VE-WSP can reduce the computational complexity by 51% and 21%, in terms of multiplication and addition, respectively, in comparison with the VNLE.