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Free Space Optics The Speed of Fiber The Flexibility of Wireless What is Free Space Optics (FSO)? Free-space optics (FSO) is a line-of-sight technology that uses lasers to provide optical bandwidth connections that can send and receive voice, video, and data. Speeds can reach up to 2.5Gbps and those speeds can be transmitted up to 4km over any protocol. FSO provides a fiber optic connection using air instead of glass Why FSO? Requires no spectrum licensing. •Is easily upgradeable, and its open interfaces support equipment from a variety of vendors. •Requires no security software. •Is immune to radio frequency interference or saturation. •Can be deployed behind windows, eliminating the need for costly rooftop rights. History Its old technology! Originally developed for NASA and the military in the 1960s, well before Fiber Optic Cables How it Works FSO technology is based on connectivity between FSO-based optical wireless units, each consisting of a high-power optical source (i.e. LASAR), plus a lens that transmits light through the atmosphere to another lens receiving the information. At this point the receiving lens connects to a high-sensitivity receiver via optical fiber. Challenges and Solutions Fog: The primary challenge to FSO. The water droplets in fog can completely hinder the passage of light through a combination of absorption, scattering, and refraction. The only solutions so far is to shorten distances and add redundancies Absorption: Absorption occurs when water molecules in the atmosphere extinguish light, leading to a decrease in the power density of the FSO. Absorption occurs more readily at some wavelengths than others. Absorption can be overcome by using power appropriate to atmospheric conditions, and use of FSO units with multiple beams. Scattering: Caused when light beams hit particulates in the are and are directed else ware. Multiple beams and network redundancies can combat this. Challenges and Solutions Physical obstructions: Flying birds or construction cranes can temporarily block single-beam FSO systems. Optical wireless products using multi-beam systems (spatial diversity) can also counter temporary obstructions. Scintillation: Heated air rising from the earth or man-made devices such as heating ducts create temperature variations among different air pockets. This can cause fluctuations in signal amplitude which leads to "image dancing" at the FSO-based receiver end Multi-beam systems can also be used to limit Scintillation problems Building sway/seismic activity: The movement of buildings can upset receiver and transmitter alignment. New FSO-based optical wireless offerings use a large receivers, tracking, and multiple beams to maintain connectivity. For more information visit www.freespaceoptics.org