free space optical communication

1. PRESENTATION
ON
“ FREE SPACE OPTICAL COMMUNICATION”
Submitted by:
SUBMITTED BY-
MUDIT RATHORE
ADM NO-15JE001217
DEPARTMENT OF ELECTRONICS ENGINEERING
IIT(ISM), DHANBAD

2. Outline
 Introduction
 History
 Working
 Advantages
 Disadvantages
 Applications
 Security
 Conclusion
 References

3. Introduction
 FSO involves communication through free space ie vacuum and finds
extensive application in interstellar space.
 FSO is an upcoming technique used for broadband communication as
we face RF spectrum scarcity with respect to increasing throughput
requirements.
 Useful in places where physical connections are impossible.
 Free space optical spectrum is license free and nearly unlimited.

4. Introduction:-
 FSO is a line-of-sight (LOS) technology that transmits a modulated
beam of visible or infrared light through the atmosphere for broadband
communications.
 FSO technology delivers cost-effective optical wireless connectivity,
power efficient, and a faster return on investment (ROI) for
Enterprises and Mobile Carriers.
 Of high usage where physical connections are impractical due to high
costs and other considerations.

5. History
 In 1880, Alexander Graham Bell invented the ‘photo-phone’ .
 The invention of lasers In the 1960s, revolutionized free space
optics.
 Germany, France and Japan made significant advancements in
free space optics for satellite communications.
 Military organizations especially were interested and forced
some developments.

6. Why FSO??
 Increasing
demand for high
bandwidth in
metro networks
 Last mile bottleneck
:Copper-based
connections limits
speed to an average of
around 12Mbps–
generally the slowest
link in the chain.
 Digging, delays and
associated costs to lay
fiber often make it
economically
prohibitive.
 RF-based networks require
immense capital investments
to acquire spectrum license.
Also bandwidth is limited to
622 Mbps
So FSO is
used as an
alternative!!

7. Working
Network traffic converted
into pulses of invisible light
representing 1’s and 0’s.
Transmitter projects the
carefully aimed light
pulses into the air.
Reverse direction
data transported
the same way.
A receiver at the other
end of the link collects the
light using lenses and/or
mirrors.
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.

8. Block Diagram
SOURCE
DESTINATION DEMODULATOR AMPLIFIER
PHOTO
DETECTOR
RECEIVE
OPTICS
TRANSMIT
OPTICS
DRIVER
LASER
DIODE
MODULATOR
ATMOSPHERIC
CHANNEL
Receiver
Transmitter

9. LED v/s LASER
LED
 Non coherent
 Few MHz
 Eye safe
 Preferred for indoor
applications.
 Optical power output.
LASER
 Coherent Beam
 Up to 10 GHz
 Harmful eye
 Can be used in all practical
outdoor applications
 FSO systems require LASER.

10. Advantages
 Installation cost is very low as compared to laying Fiber
 Highly secure transmission possible
 Unregulated Spectrum
 Low Power Consumption
 Ease of installation
 License-free long-range operation
 Immunity to electromagnetic interference
 Speed: high bit rates and low bit error rates

11. Disadvantages
 High Launch Power represents eye hazard.
 Physical obstruction
 Atmospheric barriers
 SNR can vary significantly with the distance and the ambient noise
 Low Power Source requires high sensitive receivers.
 If the sun goes exactly behind the transmitter, it can swamp the
signal.

12. Applications
 Metro Area Network (MAN)
 Last Mile Access
 Enterprise connectivity
 Fiber backup
 Backhaul
 Service acceleration
 Space Applications/Extraterrestrial(esp. in military)
 CCTV
 Video conferencing

13. Fso and Other Technologies
Coaxial cable Satellite Optical Fibre Free Space optics
Transmission
speed
500Mbps 90Mbps 100Mbps to
100Gbps
Varies
Ease of
installation
Moderate Difficult Difficult Moderate
Cost Moderate Moderate (not including
cost of satellite)
High Moderate
Maintenance
difficulty
Moderate Low Low Low
Skills Required to
install
Moderate High High Moderate
Applications Computer networks long distances Point-to-point Between buildings
Advantages Less susceptible to
interference
Speed, availability Not susceptible to
EMI
Price/ performance
Disadvantages Bulky, difficult to work
with
Propagation delay Difficult to
terminate
Can be intercepted

14. SECURITY
 FSO laser beams cannot be detected with spectrum analyzers
or RF meters.
 FSO laser transmissions are optical and travel along a line of
sight path that cannot be intercepted easily.
 The laser beams generated by FSO systems are narrow and
invisible, making them harder to find and even harder to intercept
and crack.
 Data can be transmitted over an encrypted connection adding
to the degree of security available in FSO network transmissions.

15. Conclusion
 For future short-range applications, optical wireless communications
present a viable and promising supplemental technology to radio
wireless systems and optical fiber.
 It provides a low cost, rapidly deployable method of gaining access to
fiber-quality connections and provides the lowest cost transmission
capacity in the broadband industry saving substantial up-front capital
investments.
 Can be installed for as little as one-tenth of the cost of laying fiber
cable, and about half as much as comparable microwave/RF wireless
systems thus eliminating the need to buy expensive spectrum, which
further distinguishes it from fixed wireless technologies.

16. References
[1] www.opticsinfobase.orgoefulltext.cfmuri=oe-19-26-B56&id=224428
[2] www.pi-usa.us/products/images/300x250_images/S-334-Red-Beams.jpg
[3] www.pi-usa.us/products/images/300x250_images/S-334-Red-Beams.jpg
[4] image.slidesharecdn.com/introductiontofsotechnology-
1216024918992120-8/95/introduction-to-fso-technology-3-
728.jpg?cb=1360750423
[5] image.slidesharecdn.com/freespaceoptics-140721105157-
phpapp02/95/free-space-optics-communication-9-
638.jpg?cb=1405957976
[6]www.optica.ru/EN/lant3a.jpg.
[7] http://cictr.ee.psu.edu/research/pcs/index_files/image010.jpg

17. THANK YOU
FURTHER
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