Across ice-water-air visible light communications

Visible light communication (VLC) technology has gained significant attention due to its abundant spectrum resources and high channel capacity for future LiFi and underwater optical wireless communication applications in the 6 G era. Aiming at ubiquitous wireless communication, the study of VLC across different media becomes an important research topic. In particular, the optical wireless communication in ice remains limited. In this work, we investigate the optical attenuation characteristics of four-wavelength laser diodes (LDs) in single media (water, air, ice), as well as across air-ice and water-ice interfaces. The relationship between the optical attenuation and wavelength in different media has been studied experimentally to help understand the channel characteristics. To achieve high spectral efficiency, LD-based VLC system across ice-water-air media has been established using adaptive discrete multi-tone (DMT) modulation with quadrature amplitude modulation (QAM). Least mean squares (LMS) equalization algorithm is utilized to effectively reduce interference and distortion caused by the channel. At a transmission distance of 1.2 m, the VLC system using 483 nm LD achieves 3 Gbps in the air-to-ice (A2I) channel and 2.6 Gbps in the water-to-ice (W2I) channel. This study provides valuable insights in the cross-media VLC link, laying an important foundation for future development of VLC systems for glaciological and polar exploration.