Free space optics

Free Space Optics (FSO)

BY,

YASH

Copyright © 2002 Terabeam Corporation. All rights reserved. 1

Presentation Overview

• Idea behind Free Space Optics?
• Evolution of Free Space Optics?
• Why Free Space Optics?
• Challenges
• Applications
• Advantages of FSO


In the late nineteenth century, Alexander
Bell expanded his "phone-phone"
communication which was modulated by
sunlight.


In the mid-1960's NASA initiated
experiments to utilize the laser as a means
of communication between the ground and
space.


Evolution of Free Space Optics


Every thing was destroyed including
normal fiber link

Wall street stock market was closed
because the communication was
destroyed


• FSO communication between Merrill Lynch Brokerage and Wall
Street in New York following the terrorist attack that
destroyed normal fiber optic link


Why Free Space Optics?
Why Not Just Bury More Fiber?

• Cost
• Rights of Way
• Permits
• Trenching(digging)
• Time

With FSO, especially
through the window,
no permits, no
digging, no fees


How Fiber Optic Cable Works

Glass Fiber Strands
Light Source Detector

Detector Light Source

Network Network
Device Device

• Pulses of light communicate the data
• “ON” = 1
• “OFF = 0
• Capable of more than 40 Gbps


How FSO Works
3 A receiver at the other end of the
2 Transmitter projects the link collects the light using lenses
carefully aimed light pulses and/or mirrors
into the air

5 Reverse direction data
transported the same way.
• Full duplex

1 Network traffic 4 Received signal
converted into
converted back into
pulses of invisible
fiber or copper and
light representing
connected to the
1’s and 0’s
network

Anything that can be done in fiber
can be done with FSO

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


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


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
• Fungible equipment


Challenges Sunlight
Environmental factors
Window
Attenuation
Fog

Building
Motion

Scintillation Alignment

Range
Obstructions

Low Clouds

Each of these factors can “attenuate” (reduce) the signal.
However, there are ways to mitigate each environmental factor.

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


Challenges
Scintillation
• Beam spreading and wandering due to propagation through
air pockets of varying temperature, density, and index of
refraction.
• Almost mutually exclusive with fog attenuation.
• Results in increased error rate but not complete outage.


Application of Free Space Optics

1. Satellite Laser Communication

a)Space-to-Ground Lasercom Link

b)2000 km Link Distance

c)1 Gbps Transmission Rate


2. Military application of FSO

Air Force Navy

Its potential for low Secure communication with
electromagnetic emanation submerged submarines.
when transferring sensitive
data


Advantages

• Wireless communicate from A
to B

• Low costs ($10K to $20K)

• High bit rate (10 Mbps to 2.5
Gbps)

• Set up a link in a few days

• The lasers used are eye safe,
so even a butterfly can fly
unscathed through a beam


Conclusion

• FSO is just starting to be applied to solve the
Internet “last-mile” interconnectivity problem.

• Some believe that it may be the unlimited
bandwidth solution for the metro urban core of
downtown building-to-building communication, as
well as the optimal technology for home-to-home
and office-to-office connectivity


Reference

• http://www.lightpointe.com/

• http://www.freespaceoptic.com/

• http://www.fsonews.com/

• http://www.cablefreesolutions.com/

• http://www.thefoa.org/

• http://www.free-space-optics.org/

• http://www.freespaceoptics.com/

• http://www.opticsreport.com/


Free space optics

Recommandé

Recommandé

Contenu connexe

En vedette

En vedette (18)

Dernier

Dernier (20)

Free space optics