Title: Free Space Optics
1Free Space Optics
The Speed of Fiber The Flexibility of Wireless
2What 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
3Why 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.
4History
Its old technology! Originally developed for
NASA and the military in the 1960s, well before
Fiber Optic Cables
5How 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.
6Challenges 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.
7Challenges 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.
8For more information visit www.freespaceoptics.org