This work analyzes the use of the K-means clustering algorithm to mitigate nonlinear phase noise in singlespan coherent systems, such as long-reach passive optical networks (LR-PONs). Simulations revealed that for a 100-km LR-PON employing 16-ary quadrature amplitude modulation (QAM) and considering a 1:64 splitting ratio, the adoption of K-means with K-means++ initialization achieves an optimum bit error ratio (BER) of 6.3 • 10 −4 , whereas employing maximum likelihood, 10 −3 is obtained. We also show that in order to achieve this performance improvement in 90% of the cases, K-means requires only 2,000 symbols.

Coherent optical interconnects with up to 400-Gbps transmission rates and distances exceeding 80 km have been proposed to meet the increasing capacity demand of inter-datacenter communications. The interplay between the fiber Kerr effect and the receiver noise posses an upper-bound to the transmission distance. In this paper, we used numerical simulations to find the maximum achievable range of 400-Gbps unrepeated singlewavelength links with single and dual polarization. Simulations reveal that, for a forward error correction code limit of 10-3 , the maximum distance is 145 km for dual-polarization, which can be used as a benchmark to assess the transmitter/receiver-induced penalties.

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