37-Air-Core Chalcogenide Ring Fiber with >4000 Radially Fundamental OAM Modes Across C+L Bands

A 37-air-core ring fiber is proposed to support over 4000 OAM modes for highly dense SDM and maintain radially single-mode condition, featuring <-49 dB crosstalk at 1550 nm and <-20 dB crosstalk across C+L bands after 100-km fiber propagation.