Optical fiber communications using orbital angular momentum modes

This paper presents a comprehensive review of the research efforts in harnessing orbital angular momentum (OAM) modes for space-division multiplexed (SDM) optical fiber communications, including both multi-core and mode-division approaches. With their inherent characteristics of rotational invariance, modal intensity uniformity, and manageable modal degeneracy, OAM modes uniquely enable ultra-high-capacity transmission while significantly mitigating inter-channel crosstalk and simplifying system architecture. Underpinned by these advantages, remarkable progress has been made across the critical components of OAM-based systems: advanced fibers supporting high-density low-crosstalk propagation of high-order OAM modes across distances of tens to hundreds of kilometers, high-performance scalable multiplexers and demultiplexers, and optical amplifiers with equalized modal gain. Collectively, these innovations have promoted OAM-based SDM systems to a technological level characterized by petabit-per-second capacities and ultra-high spectral efficiencies, longer transmission reaches, with low and manageable MIMO processing complexity. Together, they position OAM technology as a transformative solution to the capacity bottlenecks of conventional single-mode fibers, paving the way for the next generation of high-density, energy-efficient optical networks.