Orbital Angular Momentum Beams for High-Capacity Communications There is a growing interest in structured light, especially orbital angular momentum (OAM) beams, due to its unique amplitude and phase structure. Multiple orthogonal OAM beams can be utilized to enable high-capacity communication systems in various scenarios. This review will discuss the properties, challenges, advances, and perspectives of OAM-based optical communications, including the following (a) basic multiplexing and encodi...