WHAT IF I TRANSMIT LIGHT WITHOUT OPTICAL FIBRE? Powerpoint Templates

FREE SPACE OPTICS (F.S.O.) PRESENTED BY :- VIVEK SHRIVASTAV BRANCH/YEAR :- E&c ENGG.,4TH YEAR SECTION :- ‘B’

Contents :- Introduction Various configurations Indoor and outdoor implementations Various attenuation factors Advantages and Disadvantages Present usages of technology future scope with technology Conclusion references

In F.S.O. \ INTRODUCTION:- FIBRE REPLACED BY FREE SPACE INFORMATION TARNSMISSION BY LIGHT BEAMS THROUGH THE ATMOSPHERE

‘Wireless’ does not imply roaming ‘Ofc’ v/s ‘fso’ ‘Wireless’ does not imply roaming

Various config. :- Mainly Three types of configuration is there:- Line of site(LOS) config. Directed-non LOS config. Hybrid config. Non Directed-non LOS config. Diffused config.

Indoor implementation:- Interference:- Incandescent light(~2800 K) max. attenuation. Sunlight (~6000K) Florescent lamp Attenuation :- Free space loss(due to beam divergence) –impo. Atmospheric loss (not much in indoors) Eye safety:-most important should 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 Atmospheric Loss (varies with weather) 0.2 dB/km in exceptionally clear weather 300 dB/km in very dense fog Restricts 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 divergence Atmospheric losses exponential term– dominates Scattering + Absorption

Thus, larger λ => lower attenuation Attenuation :: Scattering Depends on particle size Size parameter α = 2π r/λ ‘ r ’ varies with atmospheric composition r << λ => σ ~ λ-4 Rayleigh Scattering-fog r ~ λ => σ ~ λ-1.6 to 0 Mie Scattering r >> λ => σ ~ λ0 Geometric Scattering Thus, larger λ => lower attenuation

Scintillation noise :- Inhomogenities in Temp. and Pressure Variations in Refractive Index along the transmission path Speckled pattern (both in time and space) at the receiver

Link capacity:- Advantages of FSO :- 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 throughout WDM(wavelength division multiplexing) leading upto 10Gbps connectivity.

Economical :- Advantages …….. Contd. Uses optical transceiver-cheaper No licensing for spectrum-bandwidth allocation is free Requires no software upgradation –for particular device Immune 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 absorption Fog -one of major cause. Scintillation Sun 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 comes But its merits are the reason they are being used in various technologies “Reveals a new world to be explored”.

References :- 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. www.wikkipedia.com www.freespaceoptics.com Free-Space Optical Communications at JPL/NASA H. Hemmati. Integration Scenarios for Free Space Optics in Next Generation (4G) Wireless Networks Waqar Hameed*, S. Sheikh Muhammad** and Noor Muhammad Sheikh*. Experimental Performance Study of a Very High Speed Free Space Optic Link at the University of Beira Interior Campus: a Case Study. 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. Google search-images.

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