Free Space Optics (FSO)
Technology Overview
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Copyright © 2002 Terabeam Corporation. All rights reserved.
1
Presentation Overview
• Introduction
• Why Free Space Optics?
• How FSO Works
• Challenges
• Advantages of FSO
• Applications of FSO
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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INTRODUCTION
• Free space optics is line of sight technology which
uses laser and photo detector to provide optical
connection between two system without fiber.
• FSO can transmit data ,audio and video at the speed
of 2.5GHz.
• FSO uses invisible infrared laser light with
wavelength of 750nm or 1500nm..
• FSO is full duplex(It can transmit data in both
direction).
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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Why Free Space Optics?
Why Not Just Bury More Fiber?
• Cost
• Rights of Way
• Permits
• Trenching
• Time
With FSO, especially through
the window, no permits, no
digging, no fees
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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Why Free Space Optics?
The FSO “Value Proposition”
• No interference
• Unlicensed
• Easy to install
• Through the window
(or from the rooftop)
• No trenching, no permits
• Fiber-like data rates
• Many deployment options
• Fungible equipment
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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Why Free Space Optics?
How Fiber Optic Cable Works
Glass Fiber Strands
Light Source
Detector
Detector
Light Source
Network
Device
Network
Device
• Pulses of light communicate the data
• “ON” = 1
• “OFF = 0
• Capable of more than 40 Gbps
• >7 CDs a second
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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How FSO Works
2 Transmitter projects the
carefully aimed light pulses
into the air
3 A receiver at the other end of the
link collects the light using lenses
and/or mirrors
5 Reverse direction data
transported the same way.
• Full duplex
1 Network traffic
converted into
pulses of invisible
light representing
1’s and 0’s
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
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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Challenges
Sunlight
Environmental factors
Window
Attenuation
Fog
Building
Motion
Alignment
Scintillation
Obstructions
Range
Low Clouds
Each of these factors can “attenuate” (reduce) the signal.
However, there are ways to mitigate each environmental factor.
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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Challenges
Atmospheric Attenuation - FOG
• Absorption or scattering of optical
signals due to airborne particles
• Primarily FOG but can be rain,
snow, smoke, dust, etc.
• Can result in a complete outage
• FSO wavelengths and fog droplets
are close to equal in size
– (Mie Scattering)
• Typical FSO systems work 2-3X
further than the human eye can see
• High availability deployments
require short links that can operate
in the fog
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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Challenges
Low Clouds, Rain, Snow and Dust
• Low Clouds
– Very similar to fog
– May accompany rain and snow
• Rain
– Drop sizes larger than fog and
wavelength of light
– Extremely heavy rain (can’t see
through it) can take a link down
– Water sheeting on windows
• Heavy Snow
– May cause ice build-up on windows
– Whiteout conditions
• Sand Storms
– Likely only in desert areas; rare in
the urban core
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Challenges
Scintillation
• Beam spreading and wandering due to propagation through
air pockets of varying temperature, density, and index of
refraction.
• Almost mutually exclusive with fog attenuation.
• Results in increased error rate but not complete outage.
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Copyright © 2002 Terabeam Corporation. All rights reserved.
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ADVANTAGES OF FSO
•
DATA SECURITY:
To overcome the security in a network two conditions are necessary
1)Intercept enough of the signal to reconstruct data packet and
2)Be able to decode that information.
•
NO LICENCE REQUIRE
•
INSTALLATION COST IS VERY LOW
•
HIGHLY SECURED TRANSMISSION IS POSSIBLE
•
HIGH DATA RATE UPTO 2.5 GHz TO 10 GHz IN NEARER FUTURE .
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 Air Force
 Its potential for low
electromagnetic emanation
when transferring sensitive
data
 Navy
 Secure communication
with submerged
submarines.
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Copyright © 2002 Terabeam Corporation. All rights reserved.
13
THANK YOU
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