Free Space Optical Communication
. CHAPTER-1
INTRODUCTION
Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to transmit data for telecommunications orcomputer networking. "Free space" means air, outer space, vacuum, or something similar. This contrasts with using solids such as optical fiber cable or an optical transmission line. The technology is useful where the physical connections are impractical due to high costs or other considerations. Free-space optical communication (FSO) systems (in space and inside the atmosphere) have developed in response to a growing need for high-speed and tap-proof communication systems. Links involving satellites, deep-space probes, ground stations, unmanned aerial vehicles (UAVs), high altitude platforms (HAPs), aircraft, and other nomadic communication partners are of practical interest. Moreover, all links can be used in both military and civilian contexts. FSO is the next frontier for net-centric connectivity, as bandwidth, spectrum and security issues favor its adoption as an adjunct to radio frequency (RF) communications. While fixed FSO links between buildings have long been established and today form a separate commercial product segment in local and metropolitan area networks , the mobile and long-range applications of this technology are aggravated by extreme requirements for pointing and tracking accuracy because of the small optical beam divergences involved. This challenge has to be addressed to fully exploit the benefits of optical links. Furthermore, long-haul optical links through the atmosphere suffer from strong fading as a result of index-of-refraction turbulence (IRT) and link blockage by obscuration such as clouds, snow and rain. In this article an overview of the challenges a system designer has to respond to when implementing an FSO system is provided. Typical gains and losses along the path from the transmitter through the medium, to the receiver are introduced
INTRODUCTION
Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to transmit data for telecommunications orcomputer networking. "Free space" means air, outer space, vacuum, or something similar. This contrasts with using solids such as optical fiber cable or an optical transmission line. The technology is useful where the physical connections are impractical due to high costs or other considerations. Free-space optical communication (FSO) systems (in space and inside the atmosphere) have developed in response to a growing need for high-speed and tap-proof communication systems. Links involving satellites, deep-space probes, ground stations, unmanned aerial vehicles (UAVs), high altitude platforms (HAPs), aircraft, and other nomadic communication partners are of practical interest. Moreover, all links can be used in both military and civilian contexts. FSO is the next frontier for net-centric connectivity, as bandwidth, spectrum and security issues favor its adoption as an adjunct to radio frequency (RF) communications. While fixed FSO links between buildings have long been established and today form a separate commercial product segment in local and metropolitan area networks , the mobile and long-range applications of this technology are aggravated by extreme requirements for pointing and tracking accuracy because of the small optical beam divergences involved. This challenge has to be addressed to fully exploit the benefits of optical links. Furthermore, long-haul optical links through the atmosphere suffer from strong fading as a result of index-of-refraction turbulence (IRT) and link blockage by obscuration such as clouds, snow and rain. In this article an overview of the challenges a system designer has to respond to when implementing an FSO system is provided. Typical gains and losses along the path from the transmitter through the medium, to the receiver are introduced
References: [1] F. J. Duarte, Secure interferometric communications in free space, Opt. Commun. 205, 313-319 (2002). [2] http://www.cs.utah.edu/cmpmsi/papers09/paper1.pdf CMP-MSI: 3rd Workshop on Chip Multiprocessor Memory Systems and Interconnects held in conjunction with the 36th International Symposium on Computer Architecture, June 2009. [3] http://www.esa.int/esaTE/SEMN6HQJNVE_index_0.html [4] en.wikipedia.org/wiki/Free-space_optical_communication [pic]