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WHAT IF I TRANSMIT LIGHT WITHOUT OPTICAL FIBRE?

FREE SPACE OPTICS(F.S.O.)

PRESENTED BY :- VIVEK SHRIVASTAVBRANCH/YEAR :- E&c ENGG.,4TH YEARSECTION :- ‘B’

Contents :-IntroductionVarious configurationsIndoor and outdoor implementationsVarious attenuation factorsAdvantages and DisadvantagesPresent usages of technologyfuture scope with technologyConclusionreferences

\INTRODUCTION:-

FIBRE REPLACED BY FREE SPACE

INFORMATION TARNSMISSION BY LIGHT BEAMS THROUGH THE ATMOSPHERE

In F.S.O.

‘Ofc’ v/s ‘fso’

‘Wireless’ does not imply roaming

VARIOUS CONFIG. : -

Mainly Three types of configuration is there:-

a. Line of site(LOS) config.b. Directed-non LOS config.

Hybrid config.c. Non Directed-non LOS

config. Diffused config.

Indoor implementation:-Interference:-

Incandescent light(~2800 K) max. attenuation.Sunlight (~6000K)Florescent lamp

Attenuation :-o Free space loss(due to beam divergence) –impo.o Atmospheric loss (not much in indoors)

Eye safety:-most importantshould be class 1 safe(< 0.5 mW, 880 nm, LASER)restricts system power (though LEDs can be used at higher

powers, but Bandwidth limited)

Outdoor implementation :-•Attenuation – Most Important

oAtmospheric Loss (varies with weather)0.2 dB/km in exceptionally clear weather300 dB/km in very dense fogRestricts the range (~500m in most commercial systems)May need low capacity back-up RF links

•Scintillation Noise (atmospheric turbulence induced intensity fluctuations) – speckled pattern•Alignment Issues – Line of sight•Interference

Sunlight (~ 6000 K)

Various Attenuation factors :-

Attenuation factors ….contd.

PR= PT . Areceiver . e –σ.R/(Div-range)2

PR ~ PT e –σ.R

WHERE σ IS ATTENUATION FACTOR FOR TRANSMISSION

Free Space losses-beam divergenceAtmospheric losses exponential term– dominates

Scattering + Absorption

Attenuation :: Scattering

Depends on particle sizeSize parameter α = 2π r/λ‘ r ’ varies with atmospheric composition

r << λ => σ ~ λ-4 Rayleigh Scattering-fogr ~ λ => σ ~ λ-1.6 to 0 Mie Scatteringr >> λ => σ ~ λ0 Geometric Scattering

Thus, larger λ => lower attenuation

Scint i l lat ion noise : -

Inhomogenities in Temp. and Pressure

Variations in Refractive Index along the transmission path

Speckled pattern (both in time and space) at the receiver

Advantages of FSO :-

Link capacity:-capable of sending up to 1.25 Gbps of

data, voice, and video communications simultaneously through the air

enables optical communications at the speed of light

full-duplex Gigabit Ethernet throughoutWDM(wavelength division multiplexing)

leading upto 10Gbps connectivity.

Advantages …….. Contd.

•Economical :-Uses optical transceiver-cheaperNo licensing for spectrum-bandwidth

allocation is freeRequires no software upgradation –for

particular deviceImmune to radio frequency interference and saturation.

Advantages …….. Contd.

•Simpler to install-just connecting the to transceiver.

•High bit rates.•low bit error rates•Protocol transparency-using highly directional beam.•easy to encrypt any data travelling across the FSO connection

Disadvantages of FSO : -Beam dispersion-atmospheric effect.Atmospheric absorptionFog -one of major cause.ScintillationSun at opposite side to receiver-swamp signals.Shadowing .

Disadvantage…….. Contd.

Requires a compatible area for installation.

Devices require maintenance.

Application-FSO :-•LAN-to-LAN connections on campuses at Fast Ethernet or Gigabit Ethernet speeds•LAN-to-LAN connections in a city- Metropolitan area network.•Converged Voice-Data-Connection•Temporary network installation (for events or other purposes).•Re-establish high-speed connection quickly (disaster recovery).

Application-FSO :- ..Contd.•For communications between spacecraft, including elements of a satellite constellation.

•As option for intra connectivity in companies.

Future scope of technology:- •Deep space exploration.

•High speed switching systems.

•Analogous to satellite communication link.

•Will reduce the effective cost of means of communications.

Some snaps-FSO :-

Conclusions :-Short distance connectivity.Atmospheric condition dependency.

Higher speed and bandwidth.

Immune to data loss.Highly secure.Fast temporary

installation.Free of cost spectrum.

Every technologies have short comesBut its merits are the reason they are

being used in various technologies

“Reveals a new world to be explored”.

References : -1. An Introduction to Free-space Optical Communications Hennes HENNIGER1, Otakar

WILFERT2,1 Institute of Communications and Navigation, German Aerospace Center (DLR), 82230 Wessling, Germany,2University of Technology Purkynova 118, CZ-61200 Brno, Czech Republic.

2. www.w ikk iped ia . com3. www. f reespaceopt i cs . com4. Free-Space Optical Communications at JPL/NASA H. Hemmati.5. Integration Scenarios for Free Space Optics in Next Generation (4G) Wireless Networks

Waqar Hameed*, S. Sheikh Muhammad** and Noor Muhammad Sheikh*.6. Experimental Performance Study of a Very High Speed Free Space Optic Link at the

University of Beira Interior Campus: a Case Study.7. An Intra-Chip Free-Space Optical Interconnection, Jing Xue, Alok Garg, Berkehan

Ciftcioglu, ShangWang, Jianyun Hu, Ioannis Savidis, yManish Jain,Michael Huang, Hui Wu, Eby G. Friedman, yGary W. Wicks, yDuncan Moore.

8. Google search-images.

Thankyou

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