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ATERM PAPER PRESENTATION

ON“FSO”

BY PRIYA HADA

Enroll.no.10302155ASETAUR

NOV,2012

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CONTENTSFSO TechnologyWhy FSO?Features and BenefitsSystem OverviewSystem designApplicationChallengesConclusion

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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

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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).

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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.

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SYSTEM OVERVIEW

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How FSO works?

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

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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.

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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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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

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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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Requirements of a good transmission system

High BandwidthLow BERHigh SNRPower efficientProvide Data

Security.Low costEasy to install and

maintain

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System design

• LOS OPERATION• SPECTRAL ALLOCATION• ALTERNATE ROUTING• NETWORK TOPOLOGIES• NETWORK SCALABILITY• COVERAGE AREA• DEPLOYMENT AND

INSTALLATION

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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. • Computer to printer links

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Sunlight

Scintillation

Obstruction

WindowAttenuation

FogBuilding 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

CHALLENGES FOR FSOAtmosphere(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

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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

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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.

Implementation of FSO

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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.

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THANK YOU!!!

Q & A

Thank you for giving your attention!

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