Shantanu NAIK
Transcript of Shantanu NAIK
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FREE SPACE OPTICAL COMMUNICATION
(FSO)
Submitted By : Shantanu Praksah Naik
Branch : ECE( 3rd year)
Roll no : CSJMA10001390102
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PRESENTATION OVERVIEW
Introduction to FSO ?
Why FSO Today ?
Free-space optics subsystems
Working of FSO
Basic Architectures
Free Space Optics Applications
Challenges
Eye Safety
FSO Advantages
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Why FSO Today
Why Not Just Bury More Fiber?
No Trenching as in laying fiber optics
Less Installation Time
Low Cost
High data rates, up to 2.5Gbps at
present and 10 Gbps in the nearfuture.
Requires no RF spectrum licensing.
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FREE-SPACE OPTICS SUBSYSTEMS
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How FSO Works1 Network traffic converted into
pulses of invisible light
representing 1s and 0s
2Transmitter projects the
carefully aimed light pulsesinto the air
3 A receiver at the other end of
the link collects the light using
lenses and/or mirrors
Received signal converted back
into fiber or copper and
connected to the network
4
Reverse direction data transported
the same way. FULL DUPLEX5
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Basic Architectures
1. POINT TO POINT ARCHITECTUREIn this architecture two places are
connected using FSO technology
2. MESH ARCHITECTURE
Composed of a series of interconnected nodes
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3. POINT-TO-MULTIPOINT ARCHITECTUREA single node serves as an originator and multiple
links emanate from it.
4. MULTIPLE PTP ARCHITECTURESuitable to create an extensive link path
between distant buildings
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FSO CORE APPLICATIONS
METRO NETWORK EXTENSIONSFSO can be deployed to extend an existing metro ring or
to connect new networks
ENTERPRISE CONNECTIVITY
The flexibility of FSO allows it to be deployed in manyenterprise applications
FIBER COMPLEMENTFSO may also be deployed as a redundant link to back-up
fiber
DWDM SERVICESIndependent players aiming to build their own fiber rings
may use FSO to complete part of the ring
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CHALLENGES IN WORKINGSunlight
Building
Motion
Alignment
WindowAttenuation
Fog
Each of these factors can attenuate (reduce) the signal. However, there
are ways to mitigate each environmental factor.
Scintillation
RangeObstructions
Low Clouds
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Challenges
Atmospheric Attenuation - FOG
Absorption or scattering of opticalsignals 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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ChallengesSCINTILLATION
Scintillation is the spatial variation in light intensity caused byatmospheric turbulence
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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Challenges
Building Motion
Type Cause(s) Magnitude Frequency
Tip/tilt Thermal
expansion
High Once per day
Sway Wind Medium Once everyseveralseconds
Vibration Equipment (e.g.,HVAC), doorslamming, etc.
Low Many timesper second
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Challenges
Building Motion Thermal Expansion
Results from Seattle
Deployment:
15% of buildingsmove more than 4
mrad
5% of buildings move
more than 6 mrad
1% of buildings move
more than 10 mrad
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Challenges
Compensating for Building Motion Two Methods
1. Automatic Pointing and Tracking
Allows narrow divergence beams for greater link margin
System is always optimally aligned for maximum link margin
Additional cost and complexity
1. Large Divergence and Field of View
Beam spread is larger than expected building motion Reduces link margin due to reduced energy density
Low cost
0.2 1 mrad divergence
= 0.2 to 1 meter spread at 1 km
2 10 mrad divergence
=2 to 10 meter spread at 1 km
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EYE SAFETY AND FREE SPACE OPTICS
Laser beams with wavelengths in the range of 400 to 1400 nm
emit light that passes through the cornea and lens and is
focused onto a tiny spot on the retina (NOT SAFE)
wavelengths above 1400 nm are absorbed by the cornea and
lens, and do not focus onto the retina(SAFE)
Any FSO system can be designed eye safe independent of the
wavelength used
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FREE SPACE OPTICS (FSO)
ADVANTAGES
Requires no RF spectrum licensing.
Is immune to radio frequency interference or saturation.
Very secure due to high directionality and narrow ness of
beams
Zero chances of network failure.
Full Duplex Operation
Can be deployed behind windows, eliminating the need for
costly rooftop rights
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CONCLUSION
FSO network can be rapidly deployed to provide
immediate service to the customers. Though not
very popular at the moment FSO has a tremendous
scope for deployment. FSO adds the wireless
feature to OFC and thus provide a boon in the field
of high bandwidth requirements.
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REFERENCES
[1] Willebrand, S. Ghuman Baksheesh. Free Space
Optics : Enabling Optical Connectivity in Todays
Networks Publisher Sams Publishing
[2] Clark Gerald R. Free Space Optics : Extending the
Metro Optical Networks. Publisher : LightPointe.
[3] http://www.wikipedia.org
[4] http://www.lightpointe.com
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THANK YOU