3. Why FSO?
Only about 5% of commercial
buildings are lit with fiber
Wide Area Networks between
major cities are extremely fast
•Fiber based
Local Area Networks in
buildings are also fast
The connections in
between are typically
a lot slower
The “Last Mile” Bottleneck Problem
9. Advantages of FSO
Easy to install
• Rapid installations without trenching and permitting
through the window
• Direct connection to the end user
• Bypasses the building owner
• No roof rights
• No riser rights
12. Challenges of FSO
• Compensating for Building Sway – 2 Methods
• Automatic Pointing and Tracking
using MEMS technology
0.2 – 1 mrad divergence
= 0.2 to 1 meter spread at 1 km
13. Challenges of FSO
• Compensating for Building Motion
• Large Divergence and Field of View
2 – 10 mrad divergence
=2 to 10 meter spread at 1 km
21. Comparison
Criteria FSO Optical Fiber RF
Installation Easy Difficult Easy
Cost Moderate High Moderate
Maintenance time Short Large Short
Most common uses Last Mile solution
(short distance)
Long distance Short/Long distance
Security Moderate High Moderate
Flying birds can temporarily block a single beam, but this tends to cause only short interruptions, and transmissions are easily and automatically resumed.
The movement of buildings can upset receiver and transmitter alignment.
-Heated air rising from the earth or man-made devices such as heating ducts creates temperature variations among different air pockets. This can cause fluctuations in signal amplitude which leads to image fluctuations at the FSO receiver end.
-Beam spreading and wandering due to propagation through air pockets of varying temperature, density, and index of refraction.
-: The major challenge to FSO communications is fog. The primary way to counter fog when deploying FSO is through a network design that shortens FSO link distances and adds network redundancies. FSO installations in foggy cities such as San Francisco have successfully achieved carrier-class reliability
To those unfamiliar with FSO, safety is often a concern because the technology uses lasers for transmission.
Mitigation of power
Wavelength=1550 nm
Stratospheric Conditions.
Low attenuation, no cloud interference, low tempreture…etc.
Cost Effective (Compared to Satellites
Estimated Range: more than 600km.
