1. 1

2. CONTENTS
FSO Technology
Why FSO?
Features and Benefits
System Overview
System design
Application
Challenges
Conclusion
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3. FSO - Technology
• Fiber less laser driven LOS technology
• No licensing required
• FSO links are full duplex
• Operating wavelength range
• 780-900nm
• 1500-1600nm
• Use invisible modulated beams of light instead of
radio waves
• Transmission speed up to 1.25 Gbps
3

4. WHY FSO?
• Electro-magnetic frequency
spectrum has been gobbled up.
• The airwaves are becoming
severely overcrowded.
• Little space left in the radio
spectrum, to add more
information channels.
• For this reason, many
companies and individuals are
looking toward light(optical
communication). 4

5. Features and Benefits
• Very high data-rates (several Gbps).
• Small beam divergence minimizes
free-space losses.
• Low power-consumption.
• Requires no RF spectrum licensing.
• Is easily upgradeable.
• Requires no security software
upgrades.
• Long range point to point links.
• No cables required. 5

6. SYSTEM OVERVIEW
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7. How FSO works?
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1 Network traffic
converted into
pulses of
invisible light .
2
Transmitter projects the
carefully aimed light pulses
into the air
5 Reverse direction data
transported the same way.
• Full duplex
3 A receiver at the other end of the
link collects the light using
lenses and/or mirrors
4 Received signal
converted back into
fiber or copper and
connected to the
network
Anything that can be done in fiber can
be done with FSO

8. How FSO works? Conti…
• Optical wireless unit uses an optical sources +
transmitting lens or telescope that transits light
through the atmosphere to receiving lens.
• It transmit invisible, eye-safe light beams from
source to destination using low power infrared laser
in the THz spectrum.
• Light focused on highly sensitive detector receiver.
• At this point, the receiving lens or telescope connect
with optical cable which gives our original
information. 8

9. Transceiver Unit
• The received laser beam (yellow) is much wider than the
transmitted beam (red). That’s why the receiver lens is so
much larger than the transmitter lens.
• Both lenses, which share the same axis.
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10. COMPONENTS OF TRANSRECEIVER
• The modulated light source, is a LASER, which provides
the transmitted optical signal.
LASER
1. Modulates at 20 Mbps to 2.5 Gbps
2. Coherent, Operate in the 850 to 1550 wavelength band
PIN photodiodes
• Inexpensive
• Sensitive in the red and infrared spectrum
Avalanche Photodiodes (APD)
• Expensive
• Excellent red sensitivity 10

11. Narrow and Directional Beams
• Beams only a few meters in diameter at a kilometer
• Allows VERY close spacing of links without interference
• Highly secure
• Efficient use of energy
• Ranges of 20m to more than 8km possible
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12. Requirements of a good
transmission system
High Bandwidth
Low BER
High SNR
Power efficient
Provide Data
Security.
Low cost
Easy to install and
maintain 12

13. System design
• LOS OPERATION
• SPECTRAL ALLOCATION
• ALTERNATE ROUTING
• NETWORK TOPOLOGIES
• NETWORK SCALABILITY
• COVERAGE AREA
• DEPLOYMENT AND
INSTALLATION
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14. Application
• Deep space communications.
• Building to building computer data links; very high
data rates.
• Weather, geophysical, remote communication.
• Optical radar; shape, speed, direction and range.
• Remote telephone links; cheaper than microwave.
• Metro network extensions.
• Campus wide computer networks.
• City-wide information broadcasting .
• Inter-office data links. 14

15. 15
Sunlight
Scintillation
Obstruction
Window
Attenuation
Fog
Building
Motion
Low Clouds
Alignment
Range
Each of these factors can “attenuate” (reduce) the signal.
However, there are ways to mitigate each environmental factor
Environmental factors

16. CHALLENGES FOR FSO
Atmosphere(Fog)- Design a network
that shortens FSO link distances
Absorption - Suspended water
molecules in the atmosphere
extinguish photons. Thus decrease
power density (attenuation) of beam .
Scattering - Scattering is caused
when the wavelength collides with the
scatterer.
• Reyleigh scattering-When the scatterer
is smaller than the wavelength.
• Mie scattering-When the scatterer is of
comparable size to the wavelength.
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fog
smoke

17. Continued….
 Physical obstructions: Flying birds
can temporarily block a beam, but this
tends to cause only short
interruptions.
Building sway/seismic activity: It
can upset receiver and transmitter
alignment.
Safety: It is also a concern because
the technology uses lasers for
transmission
Scintillation: Heated air rising from
the earth creates temperature
variations among different air pockets
and cause fluctuations in signal
amplitude 17

18.  Disaster management as was
exhibited during the Sept 11
attacks.
 Merill Lynch & Co. has set up
FSO system from its Vesey
Street office towers across the
Hudson River to an alternate
site in New Jersey.
 TeraBeam, a major producer of
FSO equipment, successfully
deployed FSO at the Sydney
Summer Olympic Games.
 A network of FSO devices is fast
coming up in Seattle which is
touted as the Capital of Fog. 18
Implementation of FSO

19. Conclusion
• It give very high data rate.
• Very cheaper than fiber optic
communication.
• Can be deployed behind
windows, if rooftop sites are
costly.
• Also used for temporary
connection.
• Give more information
security than other technology,
requires no security software. 19

20. THANK YOU!!!
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21. Q & A
Thank you for giving your attention!
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