A Survey on Reconfigurable Intelligent Surface-Assisted Optical Wireless Communications

Reconfigurable intelligent surfaces (RISs) have attracted significant interest in recent years, primarily due to their ability to dynamically manipulate the propagation characteristics of the electromagnetic environment. By intelligently adjusting the phase, amplitude, or polarization of incident signals, RISs can enhance signal coverage, mitigate interference, and improve link reliability, offering a low-cost and energy-efficient solution for next-generation wireless communication systems. While RIS technologies have been widely explored in radio frequency bands such as sub-6 GHz, millimeter wave (mmWave), and terahertz (THz), their application to the optical domain—encompassing free-space optical communication (FSOC) and visible light communication (VLC)—is a relatively recent development. Optical wireless communication (OWC) leverages the unlicensed optical spectrum to deliver high-capacity wireless links. However, FSOC systems exhibit significant vulnerability to line-of-sight (LoS) blockage. Although VLC systems are more resilient to non-line-of-sight (NLoS) conditions, they still experience performance degradation in shadowed environments. As an emerging class of optical communication devices, optical reconfigurable intelligent surfaces (ORISs) have the ability to control essential characteristics of optical beams. and offer a promising approach to enhance signal robustness and coverage by enabling dynamic beam control and path reconfiguration. In this paper, we provide a comprehensive overview of the state-of-the-art in ORISs, categorizing them into mirror-based, meta-surface-based, and simultaneous transmission and reflection (STAR)-based structures. We highlight the distinct characteristics of ORIS deployment in key OWC subset technologies, i.e., FSOC and VLC. For both, we review classical channel models and discuss their extension to ORIS-assisted scenarios, identifying open challenges in channel modeling. We emphasize the pivotal role of transceiver architecture—whether based on intensity modulation/direct detection (IM/DD) or coherent modulation/coherent detection (CM/CD)—as it dictates the exploitable signal dimensions. Accordingly, we classify existing studies based on transceiver type and analyze how ORISs can be leveraged to enhance system performance. This taxonomy provides insight into the capabilities and limitations of ORIS integration across different OWC configurations. Finally, we outline several promising research directions and identify key open challenges for future work.