best explanation

1. A Technical Seminar
Presentation
On
FREE SPACE OPTICAL WIRELESS COMMUNICATION
Guide :
Mrs. N. LAVANYA
Assistant Professor
Presented by :
S. SAI CHARAN
197Z1A04A6

2. Contents:
• Why Free Space Optics?
• Challenges
• Advantages and Disadvantages
• Applications
• Conclusion

3. Why Free Space Optics?
How Fiber Optic Cable Works
Light Source
Glass Fiber Strands
Detector
Network
Device
• Pulses of light communicate the data
• “ON” = 1
• “OFF = 0
• Capable of more than 40 Gbps
• >7 CDs a second
Light Source
Detector
Network
Device

4. Why Free Space Optics?
Why Not Just Bury More Fiber?
• Cost
• Digging
• Permits
• Trenching
• Time
With FSO, especially through the
window, no permits, no digging,
no fees

5. Why Free Space Optics?
How FSO Works
1 Network traffic
converted into
pulses of invisible
light representing
1’s and 0’s
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

6. Why Free Space Optics?
Very Narrow and Directional Beams
• Beams only a few meters in diameter at a kilometer
• Allows VERY close spacing of links without interference
• No side lobes
• Highly secure
• Efficient use of energy
• Ranges of 20m to more than 8km possible

7. Why Free Space Optics?
Deployment Behind Windows
• Rapid installations without trenching and
permitting
• Direct connection to the end user
• Bypasses the building owner
• No roof rights
• No riser rights

8. 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

9. Challenges
Environmental factors
Sunlight
Building
Motion
Alignment
Window
Attenuation
Fog
Scintillation
Range
Obstructions
Low Clouds
Each of these factors can “attenuate” (reduce) the signal.
However, there are ways to mitigate each environmental factor.

10. 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
• 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

11. 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

12. Challenges
Building Motion – Thermal Expansion
Results from Seattle Deployment:
• 15% of buildings move more
than 4mrad
• 5% of buildings move more
than 6mrad
• 1% of buildings move more
than 10mrad

13. ADVANTAGES
• It is secure.
• Low maintenance.
• Low cost as compared to fibre networks.
• License-free-long range operations.
DISADVANTAGES
• High lunch power represents eye hazard.
• Light interference negatively effect system performance.
• Low power source requires high sensitive receivers.

14. CONCLUSION
• For future short-range applications, optical wireless communications present a viable and promising
supplemental technology to radio wireless systems.
• Recent advances in the performance of optical links (in terms of both transmission speed and spatial
coverage) are based above all on efficient digital signal processing techniques.

15. THANK YOU