Next Generation Optical Wireless Communication Systems

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Chapter 2.2 Overview of FSO Technology:
FSO technology consist of the transfer of data/information between two points using optical radiation as the carrier signal through unguided channels. The transported data is modulated on the intensity, phase, or frequency of the optical carrier. An FSO link is fundamentally based on line-of-sight (LOS) transmission with no obstruction along the propagation path, thus ensuring very high data rate transmission in the absence of any multipath induced dispersion [59, 60]. The unguided channels could be any, or a combination of, space, sea-water, or atmosphere. The focus in this work is on terrestrial FSO and, as such, the channel of interest is the atmosphere. (Figure 2-1: Setup of the FSO Sender and receiver)
FSO systems allow the use of narrow divergence, directional laser beams, which provide high security with a low probability of interception or detection; features that can be desirable in many applications. Narrow and highly focused optical beams are also important in situations where the channel is not clear due to fog. For example, penetration of dense fog over a kilometre distance is achievable at Gbps data rates with a beam divergence of 0.1 mrad. Furthermore, the tight antenna patterns of FSO links allow considerable spatial re-use, and wireless networks using such connectivity are highly scalable, in marked contrast to ad-hoc RF networks, which are non-scalable [61, 62].
The basic features, areas of applications, and the description of each fundamental block of an FSO system are further discussed in the following sections.
2.3 Features of FSO:
Several typical features of FSO technology are presented below:
i. Huge modulation bandwidth - The frequency range of an optical carrier spans from 10¹²-10¹ Hz, which corresponds to 2000 THz bandwidth. This is a key feature since the amount of data that can be transmitted is directly related to the bandwidth of the carrier. Optical communication permits a far

Dr. Aymen Gatri, born in Tunis, Tunisia, has received his first engineering degree from the University of Wuppertal in Germany and his PhD in Physics, Mathematics and Electrical Engineering with a focus on Optical Wireless Communications from the Northumbria University Newcastle, UK. He has more than 14 years of professional experience in various industries and positions including IT, automotive, defense, raw materials and energy. Dr. Gatri has conducted several research projects at the School of Northumbria Communications Research Lab., Optical Communications and the Bonn Rhein Sieg University of Applied Sciences. His research focus is digital transformation among various industries, in particular how digital transformation is driving 5G, IoT and futuristic Cybersecurity strategies.