80-Channel WDM-MDM Transmission Over 50-km Ring-Core Fiber using a Compact OAM DEMUX and Modular 4×4 MIMO Equalization. - Junwei Zhang; Yuanhui Wen; Heyun Tan; Jie Liu; Lei Shen; Maochun Wang; Jiangbo Zhu; Changjian Guo; Yujie Chen; Zhaohui Li; Siyuan Yu (OFC, 2019)