Optical Wireless Communications: new opportunities and applications

Optical Wireless Communications (OWCs) are a family of technologies for wireless communications which exploit optical signals for data transmission. More generally the term OWC is used to describe an optical communication in the near-Infrared (IR) portion of the electromagnetic spectrum, while transmissions in the visible range (380-780 nm) are usually referred to as Visible Light Communications (VLCs). The first papers about OWC can be traced back to the '70s, and to 2001 for VLC. InfraRed Data Association (IrDA), founded in 1993, provided the standardization for IR communications to push the commercial development of this technology. On the other side, it was necessary to wait until 2003 for visible technology to become subject of interest outside the academic world with the founding of the Visible Light Communications Consortium (VLCC) in Japan , that in 2014 became Visible Light Communication Association (VLCA). Although a vast segment of these writings is represented by telecommunications, there are relevant contributions, new concepts and ideas, that branched to address novel applications and features. Moreover, the evolution of the Internet of Things (IoT) and of the "always connected" paradigm has highlighted the limitations of widespread wireless radio systems. Interference, strictly regulated bandwidth and environmental constrains represent obstacles that aect Radio Frequency (RF) signals and hence limit the development of RF-based applications. Among these, secure Personal Area Network (PAN), underwater communications for autonomous vehicles or transmission systems for high radiation environments represent a range of applications that can be addressed by OWC technology. This thesis addresses the study and the design of OWC and VLC systems as an alternative to RF communications, in particular whenever RF are not suitable for specic applications. The thesis is organized as follows: Chapter 1 details the known limits and issues of RF systems and a brief description of the OWC and VLC alternatives already explored for selected applications. Chapter 2 presents a general description of OWC communications, describing their general features, adopted devices, channel properties and modulation formats. Chapter 3 describes the design and testing of a VLC prototype embedded in a common table lamp for indoor PAN with an extended characterization of its performances. Chapter 4 reports the design and testing of a Optical Camera Communication (OCC) system with a novel approach to the use of Region of Interest (RoI) algorithms to improve signal processing and reduce channel losses. Chapter 5 relates to the design, realization and testing of a pair of underwater optical modems that provide Ethernet connection in harsh conditions in an operative scenario. Chapter 6 finally summarizes the contributions presented in the previous chapters and gives a picture of the future possible developments of the applications explored in this thesis.