Flexible Optical Wireless Links and Nexwork

1
Flexible Optical Wireless Links and Nexwork

• IEEE Communication Magazine . March 2003

2
The Last-Mile problem

• Fiber optic network exist worldwide and the
  amount of installed fiber will continue to grow
• Construction is prohibitively high and can take
  month to finish

Service provider
Fiber giga bit/s
Customer
30k a few Mb/s
Central Hub
Virtually infinite Demand end user
Last mile
Infinite bandwidth backbone
3
Solution to the Last-Mile Optical Wireless
Network

• To replace existing copper cable
• Low cost

4
What is Optical wirelesscommunication?

• Optical carrier , rather then radio/microwave
  (305 THz)
• Outdoor link point up to 5 km
• Wireless network offer increase mobility
• Provide higher bandwidth

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Optical wireless vs Radio frequency
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Frequently Asked Question

• Did atmospheric condition make line-of-sight
  optical communication problematic and unreliable
  ?
• 1Gb/s over 1Km though very dense fogby use of
  special transmitter and receiver

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Eye Safety

• The maximum intensity that can enter the eye
  depend on the wavelength whether the laser is a
  small or extended source and the beam divergence
  angle
• In general OW systems operating at 1.3µm

Gaussian intensity profile Io 2 P/pw2
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Atmospheric Turbulence On Optical Links

• Problem
• Diameter fluctuate
• light dance
• Scintillation
• For longer ranges , in principle , turbulence
  effects can be mitigated by
• Adaptive optic transmitter/receiver
• Delayer diversity

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Atmospheric Turbulence On Optical Links cont.
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Link state

• In our Opacity wireless network approach
  responses to link state change include
• Varying the transmitter divergence , power ,
  and/or capacity
• Varying the transmission of the link
• Redirection of laser beams

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Optical link characteristics

• We are investigating high-data-rate free-space
  optical links that can be reconfigured
  dynamically
• Key characteristics include
• Optimal obscuration penetration
• Dynamic link acquisition , initiation , and
  tracking
• Topology control to provide robust quality of
  service

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Topology reconfigurationA Free-Space Optical
Example
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Experimental results
BER due to the topology control process
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Summary

• We present an overview of the issues affecting
  the implementation of an optical wireless
  net-working scheme
• Including
• Atmospheric effect
• Eye safety
• Topology control
• Laser beam configuration

THE END