Free Space optical communication- seminar ppt

1. BY –
DIGISHA SINGHAL 13BEC026
RITIKA BISWAS 13BEC088
GUIDED BY -PROF. DHAVAL SHAH
FREE SPACE OPTICAL
COMMUNICATION

2. Motivation
 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.
[1]
[2]

3. Objectives
 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.

4. Outline
 Introduction
 Working
 Challenges
 Advantages-disadvantages
 Applications
 Conclusions
 References

5. Introduction
 Line of Sight “Fiber-less” laser driven technology.
 Operating wavelength range :
1) 780-900 nm
2) 1500-1600nm
 Up to 1 Gbps Ethernet
 Distances – up to 5km.
[3]

6. History
 In 1880, Alexander Graham Bell invented the ‘photophone’ .
 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.

7. 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!!

8. Working
1 Network traffic converted
into pulses of invisible light
representing 1’s and 0’s.
2 Transmitter projects the
carefully aimed light
pulses into the air.
5 Reverse direction
data transported
the same way.
3 A receiver at the other
end of the link collects the
light using lenses and/or
mirrors.
4 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.
[5]

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

10. Working
 Based on Connectivity between FSO based optical wireless units, each consists of
an optical transceiver to provide bi-directional capability.
 The modulated light source(laser/LED) provides the transmitted optical signal,
determines all the transmitter capabilities of the system which is then
transmitted through the atmosphere.
 On the receiving end, once the signal is received, after undergoing the influences
of the time-dispersive channel and ambient light, the optical signal is directly
translated into a photocurrent at the detector.
 The electrical SNR in optical links depends on the square of the optical power,
which has a deep impact on both design and performance of OW systems.
[6]

11. Working (Cont.)
 TRANSMITTER : One or more laser diodes (LD) or light
emitting diodes (LED) are used. The choice between LED and
LD is determined by standard factors.
 RECIEVER:

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

13. Range of Wavelengths Used
 780–850 nm: These wavelengths are suitable for FSO
operation and several vendors provide high power lasers
in this region.
 1520–1600 nm : high quality transmitter and detector
components are readily available, but more expensive and
detectors are less sensitive. 50-65 times much power can
be transmitted.
 10,000nm (10 mm): relatively new to the commercial FSO
arena, being developed because of claims of better fog
transmission characteristics. Fewer components available
at 10,1000 nm

14. Challenges faced
Environmental factors: Sunlight
Building
Motion
Alignment
Window
Attenuation
Fog
These factors can “attenuate” (reduce) the signal.
Scintillation
Range
Obstructions
Low Clouds
[8]

15. • Significant
reduction in beam
intensity
• Causes a
decrease in the
power density
• Modifies light
characteristics
or hinders the
passage of light
FOG ABSORPTION
SCATTERINGSCINTILLATION
Challenges(Cont.)
•Fluctuations in
signal amplitude
leading to image
distortion

16. Advantages
[9]
 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
[10]

17. 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.

18. Applications
 Metro Area Network (MAN)
 Last Mile Access
 Enterprise connectivity
 Fiber backup
 Backhaul
 Service acceleration
 Space Applications/Extraterrestrial(esp. in military)
 CCTV
 Video conferencing
[11]

19. 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

20. Future Of FSO
 The FSO industry shows some strength, and the FSO market is
growing, though with much less speed as compared to
required speed.
 Perhaps the best overall prospects are in space, where
progress is being made in improving acquisition and tracking.
 The FSO industry consists of mostly established vendors that
manufacture equipment for various distances and speeds of
transmission. The highest speed of 2.5 Gb/s promises to be
increased to 10 Gb/s in future.

21. 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 (it requires no FCC), which further distinguishes it from
fixed wireless technologies.

22. References
1. http://www.fsona.com/
2. http://en.wikipedia.org/wiki/Free_Space_Optics
3. http://www.slideshare.net/
4. http://www.ieeexplore.ieee.org.proxy.library.carleton.ca/s
tamp/stamp.jsp?tp=&arnumber=4446618
5. http://web.mst.edu/~mobildat/Free%20Space%20Optics/
index.html
6. http://freespaceoptics.org
7. http://www.freespaceoptic.com
8. http://www.free-space-optics.org/

23. 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

24. References
[8] image.slidesharescdn.com/freespaceoptics-140721105157-phpapp
02/95/free-space-optics-communication-19-638.jpg?cb=1405957976/
[9] http://www.gigapackets.com/images/ManRunningUpArrow250.jpg
[10] termistron.com/ilginc-devre/guc-tasarrufu-devresi/Power%20Saver
%20circuit.jpg
[11] etutorials.org/shared/images/tutorials/tutorial_63/F02tk06.jpg
[12] http://www.yugatech.com/blog/wp-content/uploads/2010/03/wimax.
gif
[13] beyondthescores.files.wordpress.com/2013/07/edu627-blog-3-2.jpg

25. FURTHER QUERIES?????
THANK YOU