50G BPSK, 100G SP-QPSK, 200G 8QAM, 400G 64QAM Ultra Long Single Span Unrepeatered Transmission Over 670.64km, 653.35km, 601.93km and 502.13km Respectively. - Jian Xu; Jiekui Yu; Qianggao Hu; Ming Li; Jiasheng Liu; Qing Luo; Liyan Huang; Jie Luo; Hongyan Zhou; Lei Zhang; Shugang Jia; Xiaohong Zhang; et al. (OFC, 2019)