Development and characterization of systems for optical wireless and visible light communication

This doctoral Thesis deals with several aspects of communication through visible and infrared light by exploiting and building on the expertise of our research group at LENS in the study and manipulation of light. Over the course of three years, the project has focused on the investigation and implementation of an optical wireless communication system in several application scenarios. A pivotal aspect is the use of appropriately modulated LED light sources, allowing for the realization of long-range (10–100 m) optical channels for the delivery of information over even shorter times than those achieved in radiofrequency transmissions. One of the key applications herein demonstrated is within the field of intelligent transportation systems: this contribution provides methods to increase vehicular safety, such as the real-time relaying of traffic information for quick response in critical road situations and platooning. Some original indoor applications are also proposed, including the first full optical characterization of a communication link exploiting the existing illumination system of a real museum to deliver dedicated information and services. Furthermore, efficient long-range transmission through free space is achieved using a mid-infrared laser source, whose behavior is modeled according to different possible extents of atmospheric absorption and scattering. Finally, we present a preliminary characterization of a new reception system consisting of an optical antenna coupled with a photodiode to overcome the étendue principle and achieve fast data transmission up to 100 m even under direct sunlight irradiation. In summary, this work shows the capabilities and potential of optical wireless communication, which is now almost mature for implementation in synergy with radiofrequency-based technologies to accomplish fast, reliable, and secure pervasive communication networks.