1.1 History of Free Space Optics
Even though fibre-optic communications gained worldwide acceptance in the telecommunication industry, FSO communications is still considered relatively new. But optical communication, in various forms, has been used for thousands of years. The Ancient Greeks polished their shields to send signals during battle. In the modern era, semaphores and wireless solar telegraphs called heliographs were developed, using coded signals to communicate with their recipients. In 1880 Alexander Graham Bell and his assistant Charles Sumner Tainter created the Photophone, at Bell's newly established Volta Laboratory in Washington, DC. Bell considered it his most important invention. The device allowed for the transmission of sound on a beam of light. On June 3, 1880, Bell conducted the world's first wireless telephone transmission between two buildings, some 213 meters apart Its first practical use came in military communication systems many decades later. Carl developed the Lichtsprechgerät 80 (direct translation: light speaking device) that the German army used in their World War II anti-aircraft defence units. The invention of lasers in the 1960s revolutionized free space optics. Military organizations were particularly interested and boosted their development. However the technology lost market momentum when the installation of optical fibre networks for civilian uses was at its peak. Many simple and inexpensive consumer remote controls use low-speed communication using infrared (IR) light. This is known as consumer IR technologies. Dr. Erhard Kube, Light Pointe’s Chief Scientist widely regarded as the "father of FSO technology," in the journal of Nachrichtentechnik, in June 1968.
1.2 FSO over Other Communication
The increasing demand for high bandwidth in metro networks is relentless, and service providers pursuit of a range of applications, including metro network extension, enterprise LAN-to-LAN connectivity, wireless backhaul and LMDS supplement has created an imbalance. This imbalance is often referred to as the "last mile bottleneck." Service providers are faced with the need to provide services quickly and cost-effectively at a time when capital expenditures are constrained. But the last mile bottleneck is only part of a larger problem. Similar issues exist in other parts of the metro networks. "Connectivity bottleneck" better addresses the core dilemma Free-space optics FSO communications is a technology that uses modulated optical beams to transmit information line of sight through the atmosphere. First option is fibre optics. Fibre optics deals with study of propagation of light through transparent dielectric waveguide. Fibre optics used for transmission of data from point to point location Fibre optics are immune to cross talk and interference, but its maintaince.repairing,test procedure are difficult and costly.While FSO can be deployed faster and cheaper when compared with optical fibre FSO transmission links can be deployed quicker and in some instances more economically, than optical fibre links. Second option is the radio frequency (RF). RF communication is an incumbent and evolving technology that has high utility and will be the major method for wireless communication for the indefinite future. At lower data rates RF is excellent at providing coverage, due to the scattering and the diffraction of the radio waves, and the sensitivity of the receivers that can be constructed However, RF suffers from several constraints that people are not satisfied with its Performance For next generation of wireless communication. RF requires relatively large device with sophisticated circuits, while wireless optical communication only requires very small and cheap LED and photon detector as transceivers and easier of installation. For RF, one must...
References:  http://www.lightpointe.com
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