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Free Space OpticsFSO
Mohamed Fahmy and Mohamed Seif
Introduction
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
Overview of FSO
Transmitter Channel ReceiverLens Lens/Mirror
Operation of FSO
Advantages of FSO
No interferenceHigh Security
Advantages of FSO
• High data rates• Up to 2.5 Gb/s
Advantages of FSO
• Spectrum is too large
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
Challenges of FSO
SunlghtBuilding Sway
Alignment
WindowAttenuation
Fog
Each of these factors can “attenuate” (reduce) the signal. However, there are ways to mitigate each environmental factor.
Scintillation
Obstructions
Low Clouds
Challenges of FSO
• Building Sway -misalignment
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
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
Challenges of FSO
• Scintillation
Challenges of FSO
• Atmospheric Attenuation
Challenges of FSO
• Experiment • Line of sight =2.4 km
Challenges of FSO
• Safety Considerations
• Strict international standards have been set for safety and performance.
Applications
FSO technology roadmap
• Enhance the performance of data rate• Highest speed 2.5 Gb/s• 10 Gb/s in the future • Fiber-like data rates
FSO technology rodmap
• Future Application • FSO on HAPs
Comparison
Criteria FSO Optical Fiber RFInstallation Easy Difficult EasyCost Moderate High ModerateMaintenance time Short Large ShortMost common uses Last Mile solution
(short distance) Long distance Short/Long distance
Security Moderate High Moderate
FSO manufacturers
References
[1]LINCOLIN laboratory, MASSACHUSETS INSTITUTE OF TECHNOLOGY [2] http://www.fsona.com/technology.php?sec=fso_guide[3] http://www.laseroptronics.com/index.cfm/id/57-66.htm[4] LightPointe_White_Paper_What_is_Free_Space_Optics[5] http://spectrum.ieee.org/semiconductors/optoelectronics/fiber-optics-without-fiber
THANK YOU …
