Vectorial optical wireless communications: bridging optical physics and engineering for 6G and beyond

Abstract The demand for sixth-generation (6G) and future communication systems is pushing current wireless technologies, including the promising optical wireless communication (OWC), to their physical limits. For fundamental engineering breakthroughs, vectorial light rooted in optical physics provides a potential solution to OWC. The understanding of the physical essence of vectorial light and its use as a robust information carrier in disordered media touches upon the basic physical problem of seeking orders in disorders, thereby closely linking the future of OWC with advances in optical physics. Specifically, vectorial light fields, with different spatial modes loaded onto orthogonal polarizations, intrinsically multiplexes multiple degrees of freedom (DoFs) and enables a level of DoF control unattainable by traditional scalar modulation schemes, such as intensity modulation (IM) or homogeneous polarization modulation (PM). Furthermore, its inherent DoF coupling effect inspires novel vectorial modulation (VM) schemes, offering the possibility of a super-diversity gain. This opens up a development prospect for OWC and makes it different from conventional wireless technologies. To clarify this prospect, this article provides a systematic perspective rooted in optical physics, explaining how advances in this field are driving the evolution of scalar OWC into a vectorial era. Accordingly, we highlight the major challenges, opportunities, and preliminary solutions within this research trend. We further explore the new visions that vectorial OWC (VOWC) brings to the wireless community. For example, the multi-functional integration of optical communication, sensing, and imaging, driven by optical physics, is expected to upgrade the integrated sensing and communications functionality in 6G. Moreover, the systematic introduction of tools from cohomology theory and topological physics provides OWC with a physical perspective. We emphasize that by bridging optical physics and communication engineering, VOWC promises to greatly expand the technological vision and theoretical scope for 6G and beyond.