Free Space Optical Communications: An Overview
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paper_title: 2.5 Gbit/s free space optical link over 4.4 km

paper_content:

A new record in terrestrial free space optical transmission, 2.5 Gbit/s (single channel) over a 4.4 km range is reported. Optical data are transmitted over a horizontal path through the atmosphere, error free, using a specially designed optical telescope-transceiver, a conventional 1550 nm laser transmitter, 2.5 Gbit/s receiver/regenerator and a high power optical amplifier.
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paper_title: Fiber optics without fiber

paper_content:

Low-power infrared beams, which do not harm the eyes, are the means by which free-space optics (FSO) technology transmits data through the air between transceivers, or link heads, mounted on roof-tops or behind windows. It works over distances of several hundred meters to a few kilometers, depending upon atmospheric conditions. The authors believe that FSO could be the ultimate solution for high-speed residential access. Instead of hybrid fiber-coax systems, hybrid fiber-laser systems may turn out to be the best way to deliver high data rates directly to the home.
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paper_title: Effect of fog on free-space optical links employing imaging receivers

paper_content:

We analyze free-space optical links employing imaging receivers in the presence of misalignment and atmospheric effects, such as haze, fog or rain. We present a detailed propagation model based on the radiative transfer equation. We also compare the relative importance of two mechanisms by which these effects degrade link performance: signal attenuation and image blooming. We show that image blooming dominates over attenuation, except under medium-to-heavy fog conditions.
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paper_title: Sequential Optimization of Adaptive Arrays in Coherent Laser Communications

paper_content:

In optical wireless communications, a channel-matched adaptive coherent receiver may be implemented using an array of receive apertures. After atmospheric channel fading estimation, several replicas of a message received through the atmosphere are combined. As an alternative to training-based channel estimation, we analyze the performance of sequential techniques for direct optimization of multi-aperture array receivers in free-space coherent laser communications.
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paper_title: Outage analysis of relay-assisted free-space optical communications

paper_content:

Despite their attractive features, free-space optical (FSO) communications suffer from several challenges in practical deployment; the major of them is fading or scintillation. To overcome such limitations, multiple input multiple output (MIMO) and cooperative techniques have been proposed. Although the promising effects of cooperative transmissions in radio frequency (RF) communications have greatly been investigated, there have not been remarkable researches on cooperative transmissions in FSO communications. In this study, the authors consider a relay-assisted FSO communication and investigate the outage performance of two well-known cooperative protocols, namely amplify-and-forward (AF) and decode-and-forward (DF), for this communication system. By a new definition of the order of diversity, the authors derive an analytical expression for the performance comparison of different cooperative and non-cooperative protocols. The authors also evaluate the performance of a FSO communication with two transmitter telescopes (MIMO systems) and compare its outage probability with those of cooperation strategies. The authors investigate the best place for the relay for both the AF and DF strategies and show that relay-assisted techniques can be used for FSO communication to achieve spatial diversity. Their performance can surpass that of the two-transmitter case by properly choosing the location of the relay.
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paper_title: Fiber optics without fiber

paper_content:

Low-power infrared beams, which do not harm the eyes, are the means by which free-space optics (FSO) technology transmits data through the air between transceivers, or link heads, mounted on roof-tops or behind windows. It works over distances of several hundred meters to a few kilometers, depending upon atmospheric conditions. The authors believe that FSO could be the ultimate solution for high-speed residential access. Instead of hybrid fiber-coax systems, hybrid fiber-laser systems may turn out to be the best way to deliver high data rates directly to the home.
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paper_title: A Survey of Opportunities for Free Space Optics in Next Generation Cellular Networks

paper_content:

Cellular wireless networks have consistently relied upon Radio Frequency (RF) channels to provide connectivity between users and base stations. RF channels have also provided, in large part, connectivity within the Radio Access Network (RAN) and the Core Network (CN) for the purpose of connecting mobile users to the Public Switched Telephone Networks (PSTN) and Internet. However, other methods may be necessary in order to provide the faster data rates required by many new and emerging applications. This paper provides a comprehensive overview of the potential role for Free Space Optical (FSO) communications within next generation cellular networks. The argument is made that the increasing number of base stations, as well as the advanced topologies supported by next generation cellular networks, pave the way for a growing reliance upon FSO communications, with a view to support the high bandwidth applications offered to mobile users.
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Title: Free Space Optical Communications: An Overview

Section 1: INTRODUCTION
Description 1: This section introduces the concept of free space optical communications, its history, the challenges of existing communication methods, and the advantages of FSO technology.

Section 2: FREE SPACE OPTICS
Description 2: This section delves into the fundamentals of free space optics, comparing it with conventional optics and describing its technology and applications.

Section 3: FREE-SPACE OPTICAL NETWORKS
Description 3: This section covers the architecture options and market drivers for free-space optical networks, highlighting their configurations and benefits.

Section 4: DEPLOYMENT
Description 4: This section discusses various deployment scenarios for FSO technology, challenges faced, and solutions to overcome these obstacles.

Section 5: CONCLUSION
Description 5: This section summarizes the growth potential and future prospects of FSO technology, emphasizing its primary advantages and potential for expansion in high-speed communication networks.