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Title: Multiplexed visible light communication systems using GaN-based sources
Author: Viola, Shaun
ISNI:       0000 0004 7963 1285
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2019
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With the emergence of efficient semiconductor solid state lighting a new application space has emerged for communications, namely visible light communications (VLC). The high speed modulation capabilities of Gallium Nitride (GaN) based LEDs and laser diodes means these devices have the potential to supplement or replace existing radio wave standards such as Wifi, as well as creating new applications for optical communications such as underwater VLC. Given the ever increasing demand for information in modern society, it is desirable to continually increase the bandwidth capabilities of communication systems through both exploration of unused frequency spectrum, like the visible spectrum, and also the application of existing and developing multiplexing techniques. This thesis will focus on the investigation of quadrature amplitude modulation (QAM) based orthogonal frequency division multiplexing (OFDM) as applied to GaN based sources in various VLC systems. In this thesis investigation of complex modulation formats and advanced multiplexing techniques applied to novel m-LED devices has shown VLC system bandwidths of up to 655 MHz and data rates of up to 7.91 Gbit/s which, to the authors knowledge, is the highest data rate achieved using a single m-LED pixel for data transmission. The laser based VLC systems shown in this thesis have utilised both the simplest form of baseband modulation on off keying (OOK) as well as QAM based OFDM. These systems, at the time of publication, demonstrated the highest data rate achieved for each of these modulation types using commercially available devices. In addition to multiplexing using orthogonal frequencies the implementation of spatial multiplexing has become an area of great interest for free-space optical (FSO) communication links, particularly for its use in last-mile links within larger optical networks. Light carrying orbital angular momentum (OAM) has emerged as a potential candidate that could be utilised for multiplexing independent channels. The feasability of OAM multiplexing underwater has been investigated through analysis of inter-channel crosstalk for a set of 11 OAM modes propagating through 3 m of slowly flowing water, similar to that found in Oceanic conditions. At publication this was the first investigation of its kind where crosstalk effects induced by flowing water were measured.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: QC Physics ; T Technology (General)