Unrepeatered transmission of single-carrier 800 Gb/s over 447.96 km with simplified third-order ROPA system

To achieve the longest distance of 800 Gb/s unrepeatered transmission, we use commercial 800 Gb/s transceivers with soft-decision FEC, optimized high-order Raman pumps, and enhanced bidirectional ROPA with third-order Raman pumping in this experiment to optimize system performance. Two types of G.654E fibers are also fully characterized and used as span fibers. The improvement of transmission distance is mainly due to the remote pump power for RGU can be increased by nearly 4 dB in G.654E fiber by the third-order Raman pumping. At last, a single 800 Gb/s channel is transmitted over 447.96 km with a span loss of 73.16 dB. As far as we know, this is the longest 800 Gb/s unrepeatered transmission distance ever reported.