Free Space Optics (FSO) communications, also called Free Space Photonics (FSP) or Optical Wireless, refers to the transmission of modulated visible or infrared (IR) beams through the atmosphere to obtain optical communications. Like fiber, Free Space Optics (FSO) uses lasers to transmit data, but instead of enclosing the data stream in a glass fiber, it is transmitted through the air. Free Space Optics (FSO) works on the same basic principle as Infrared television remote controls, wireless keyboards

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A
SEMINAR REPORT
ON
“Screenless Display Technology”
As a Partial Fulfillment
For The Degree of Bachelor of Engineering in
Computer Science & Engineering
3rd
Year (5th
Semester)
YEAR: - 2014
Guided By: Prepared By:
Prof. Chandani A Naik Dilip j. Prajapati
Faculty of Engineering Technology & Research,
Isroli-Bardoli
Department of Computer Science & Engineering

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Certificate
This is to Certified that the seminar entitled FREE SPACE OPTICS carried out by
Mr. Dilip J. Prajapati PEN 130843131016 in partial fulfillments for the award of
Bachelor of Engineering in Computer Science & Engineering of Faculty of
Engineering Technology & Research, Isroli-Bardoli during the Academic year
2014-2015. It is certified that all corrections/suggestions indicated for Internal
Assessment have been incorporated in the Report. The seminar report has been
approved as it satisfies the academic requirements in respect of seminar work
prescribed for the said Degree.
Seminar Guide H. O. D.
Prof. C A Naik Prof. B R Bhatt

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ACKNOWLEDGEMENT
I would like to take this opportunity to best my acknowledgements to all the
persons who have directly or indirectly been involved with me in making my seminar
feasible and to run it up into a successful piece of work.
A report as all encompassing as this is never the work of one or two people
laboring in quiet solitude. It is the product of many hands, and countless hours from
many people. My thanks go to all those who helped, whether through their comments,
feedback, edits or suggestions. I express a deep sense of gratitude to the Head of the
Computer Science and Engineering Department, Prof. Bhavini R Bhatt and guide
Prof. Chandani A Naik who has helped me throughout my seminar.
How can I forget my college? Without whom I can’t do anything. I would like
to thank my management for their invaluable support. Their patience, understanding
and love gave us strength and will power to work through the long tedious hours in
studying the subject and preparing the report.
Last but not the least, I would also like to thank my friends and classmates
who co-operated during the preparation of my seminar report and without them this
report has not been possible. Their ideas helped me a lot to improve my project
report.
Dilip J. Prajapati
130843131016

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ABSTRACT
Free Space Optics (FSO) or Optical Wireless, refers to the transmission of
modulated visible or infrared (IR) beams through the air to obtain optical
communications. Like fiber, Free Space Optics (FSO) uses lasers to transmit data, but
instead of enclosing the data stream in a glass fiber, it is transmitted through the air. It
is a secure, cost-effective alternative to other wireless connectivity options. This form
of delivering communication has a lot of compelling advantages.
Data rates comparable to fiber transmission can be carried with very low error
rates, while the extremely narrow laser beam widths ensure that it is possible to co-
locate multiple transceivers without risk of mutual interference in a given location.
FSO has roles to play as primary access medium and backup technology. It could also
be the solution for high speed residential access. Though this technology sprang into
being, its applications are wide and many. It indeed is the technology of the future.

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INDEX
Sr. No.TITLE Page No.
ABSTRACT
1 INTRODUCTION1
1.1 DEFINIATION1
2 HISTROY2
3 HOW FREE SPACE OPTICS (FSO)WORKS 3
3.1 OPTICAL COMMUNICATION 5
3.2FSO:Wireless, at the Speed of Light 5
4 FSO ARCHITECTURES 6
4.1 POINT TO POINT 6
4.2 MESH ARCHITECTURE 6
4.3 POINT TO MULTIPOINT ARCHITECTURE 7
5 WHY FSO?8
6 APPLICATION OF FSO9
7 ADVANTAGES OF FSO11
8FREE SPACE OPTICS (FSO) SECURITY12
9 FSO CHALLENGES 13
10 CONCULSION16
REFRENCES 18

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LIST OF FIGURES
FIG. NO. TITLE PAGE NO.
3 (A) FSO WORKING 3
3 (B) FSO SUBSYSTEM WORK 4
3 (C) THE COMPONENTS OF A SENSOR NODE 5
4 (A) POINT TO POINT ARCHITECTURE 6
4 (B) MESH ARCHITECTURE 6
4 (C) POINT TO MULTIPOINT ARCHITECTURE 7
9 (A) FOG 14
9 (B) SCINTILLATION 15

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Chapter 1
Introduction
Free Space Optics (FSO) communications, also called Free Space
Photonics (FSP) or Optical Wireless, refers to the transmission of modulated
visible or infrared (IR) beams through the atmosphere to obtain optical
communications. Like fiber, Free Space Optics (FSO) uses lasers to transmit
data, but instead of enclosing the data stream in a glass fiber, it is transmitted
through the air. Free Space Optics (FSO) works on the same basic principle
as Infrared television remote controls, wireless keyboards or wireless Palm
devices.
1.1 Definition
Free space optics or FSO, free space photonics or optical wireless, refers to the
transmission of modulated visible or infrared beams through the atmosphere to obtain
optical communication. FSO systems can function over distances of several
kilometers.
FSO is a line-of-sight technology, which enables optical transmission up to
2.5 Gbps of data, voice and video communications, allowing optical connectivity
without deploying fiber optic cable or securing spectrum licenses. Free space optics
require light, which can be focused by using either light emitting diodes (LED) or
LASERS(light amplification by stimulated emission of radiation). The use of lasers is
a simple concept similar to optical transmissions using fiber-optic cables, the only
difference being the medium.
As long as there is a clear line of sight between the source and the destination
and enough transmitter power, communication is possible virtually at the speed of
light. Because light travels through air faster than it does through glass, so it is fair to
classify FSO as optical communications at the speed of light.

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Chapter 2
History
The engineering maturity of Free Space Optics (FSO) is often
underestimated, due to a misunderstanding of how long Free Space Optics
(FSO) systems have been under development. Historically, Free Space Optics
(FSO) or optical wireless communications was first demonstrated by
Alexander Graham Bell in the late nineteenth century (prior to his
demonstration of the telephone!). Bell’s Free Space Optics (FSO) experiment
converted voice sounds into telephone signals and transmitted them between
receivers through free air space along a beam of light for a distance of some
600 feet. Calling his experimental device the “photophone,” Bell considered
this optical technology – and not the telephone – his preeminent invention
because it did not require wires for transmission.
Although Bell’s photophone never became a commercial reality, it
demonstrated the basic principle of optical communications. Essentially all of
the engineering of today’s Free Space Optics (FSO) or free space optical
communications systems was done over the past 40 years or so, mostly for
defense applications. By addressing the principal engineering challenges of
Free Space Optics (FSO), this aerospace/defense activity established a strong
foundation upon which today’s commercial laser-based Free Space Optics
(FSO) systems are based.

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Chapter 3
How Free Space Optics (FSO) Works
Optical systems work in the infrared or near infrared region of light and the
easiest way to visualize how the work is imagine, two points interconnected with fiber
optic cable and then remove the cable. The infrared carrier used for transmitting the
signal is generated either by a high power LED or a laser diode. Two parallel beams
are used, one for transmission and one for reception, taking a standard data, voice or
video signal, converting it to a digital format and transmitting it through free space.
Today’s modern laser system provide network connectivity at speed of 622
Mega bits/sec and beyond with total reliability. The beams are kept very narrow to
ensure that it does not interfere with other FSO beams. The receive detectors are
either PIN diodes or avalanche photodiodes.
Fig. 3 (A):- FSO Working
The FSO transmits invisible eye safe light beams from transmitter to the
receiver using low power infrared lasers in the tera hertz spectrum. FSO can function
over kilometers.

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Wavelength:
Currently available FSO hardware is of two types based on the operating
wavelength – 800 nm(nanometer) and 1550 nm. 1550 FSO systems are selected
because of more eye safety, reduced solar background radiation and
compatibility with existing technology infrastructure.
Subsystem:
Fig. 3(B):- FSO Subsystem work
In the transmitting section, the data is given to the modulator for modulating
signal and the driver is for activating the laser. In the receiver section the optical
signal is detected and it is converted to electrical signal, preamplifier is used to
amplify the signal and then given to demodulator for getting original signal. Tracking
system which determines the path of the beam and there is special detector (CCD,
CMOS) for detecting the signal and given to pre amplifier. The servo system is used
for controlling system, the signal coming from the path to the processor and compares
with the environmental condition, if there is any change in the signal then the servo
system is used to correct the signal.
Modulator Driver Laser TransmitopticData in
De-Modulator preamplifier detector Receive opticData out
preamplifier Special
detector
Trackingoptic
Processor Servo systems
Environmental
condition

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3.1Optical Communication
Optical communication is any form of telecommunication that uses light as the
transmission medium.An optical communication system consists of a transmitter,
which encodes amessageinto an optical signal, a channel, which carries the signal to
itsdestination, and a receiver, which reproduces the message from the received
optical signal.
Fig. 3.1(C): - Optical communication
3.2 FSO: Wireless, At the Speed of Light
Unlike radio and microwave systems, Free Space Optics (FSO) is an
optical technology and no spectrum licensing or frequency coordination with
other users is required, interference from or to other systems or equipment is not
a concern, and the point-to-point laser signal is extremely difficult to intercept,
and therefore secure. Data rates comparable to optical fiber transmission can be
carried by Free Space Optics (FSO) systems with very low error rates, while the
extremely narrow laser beam widths ensure that there is almost no practical limit
to the number of separate Free Space Optics (FSO) links that can be installed in
a given location.

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Chapter 4
FSO Architectures
4.1 Point-To-Point Architecture
Point-to-point architecture is a dedicated connection that offers higher
bandwidth but is less scalable .In a point-to-point configuration, FSO can support
speeds between 155Mbits/sec and 10Gbits/sec at a distance of 2 kilometers (km) to
4km. “Access” claims it can deliver 10Gbits/ sec. “Terabeam” can provide up to
2Gbits/sec now, while “AirFiber” and “Lightpointe” have promised Gigabit Ethernet
capabilities sometime in 2001..
Fig 4 (A):- Point to Point Architecture
4.2 Mesh Architecture
Mesh architectures may offer redundancy and higher reliability with easy node
addition but restrict distances more than the other options.
Fig. 4 (B):- Mesh Architecture

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A meshed configuration can support 622Mbits/sec at a distance of 200 meters
(m) to 450m. TeraBeam claims to have successfully tested 160Gbit/sec speeds in its
lab, but such speeds in the real world are surely a year or two off.
4.3 Point-.To-Multipoint Architecture
Point-to-multipoint architecture offers cheaper connections and facilitates
node addition but at the expense of lower bandwidth than the point-to-point option.
Fig 4 (c):- Point to multipoint Architecture
In a point-to-multipoint arrangement, FSO can support the same speeds as the
point-to-point arrangement -155Mbits/sec to 10Gbits/sec-at 1km to 2km.

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Chapter 5
Why FSO?
The increasing demand for high bandwidth in metro networks is relentless,
and service providers' pursuit of a range of applications, including metro network
extension, enterprise LAN-to-LAN connectivity, wireless backhaul and LMDS
supplement has created an imbalance. This imbalance is often referred to as the
"last mile bottleneck." Service providers are faced with the need to turn up
services quickly and cost-effectively at a time when capital expenditures are
constrained. But the last mile bottleneck is only part of a larger problem. Similar
issues exist in other parts of the metro networks. "Connectivity bottleneck" better
addresses the core dilemma. As any network planner will tell you, the connectivity
bottleneck is everywhere in metro networks.
From a technology standpoint, there are several options to address this
"connectivity bottleneck," but most don't make economic sense.
The first, most obvious choice is fiber-optic cable. Without a doubt, fiber is the
most reliable means of providing optical communications. But the digging, delays
and associated costs to lay fiber often make it economically prohibitive. Moreover,
once fiber is deployed, it becomes a "sunk" cost and cannot be re-deployed if a
customer relocates or switches to a competing service provider, making it
extremely difficult to recover the investment in a reasonable timeframe.
Another option is radio frequency (RF) technology. RF is a mature technology that
offers longer ranges distances than FSO, but RF-based networks require immense
capital investments to acquire spectrum license. Yet, RF technologies cannot scale
to optical capacities of 2.5 gigabits. The current RF bandwidth ceiling is 622
megabits. When compared to FSO, RF does not make economic sense for service
providers looking to extend optical networks.

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The third alternative is wire- and copper-based technologies, (i.e. cable modem,
T1s or DSL). Although copper infrastructure is available almost everywhere and
the percentage of buildings connected to copper is much higher than fiber, it is still
not a viable alternative for solving the connectivity bottleneck. The biggest hurdle
is bandwidth scalability. Copper technologies may ease some short-term pain, but
the bandwidth limitations of 2 megabits to 3 megabits make them a marginal
solution, even on a good day.
The fourth-and often most viable-alternative is FSO. The technology is an optimal
solution, given its optical base, bandwidth scalability, speed of deployment (hours
versus weeks or months), re-deployment and portability, and cost-effectiveness
(on average, one-fifth the cost of installing fiber-optic cable).
Only 5 percent of the buildings in the United States are connected to fiber-optic
infrastructure (backbone), yet 75 percent are within one mile of fiber. As
bandwidth demands increase and businesses turn to high-speed LANs, it becomes
more frustrating to be connected to the outside world through lower-speed
connections such as DSL, cable modems or T1s. Most of the recent trenching to
lay fiber has been to improve the metro core (backbone), while the metro access
and edge have completely been ignored. Studies show that disconnects occurs in
the metro network core, primarily due to cost constraints and the deployment of
such non-scalable, non-optical technologies such as LMDS. Metro optical
networks have not yet delivered on their promise. High capacity at affordable
prices still eludes the ultimate end-user.

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Chapter 6
Applications of FSO
Optical communication systems are becoming more and more popular as
the interest and requirement in high capacity and long distance space communications
grow. FSO overcomes the last mile access bottleneck by sending high bit rate signals
through the air using laser transmission.
Applications of FSO system are many and varied but a few can be listed.
1. Metro Area Network (MAN): FSO network can close the gap between
the last mile customers, there by providing access to new customers to high
speed MAN’s resulting to Metro Network extension.
2. Last Mile Access: End users can be connected to high speed links using
FSO. It can also be used to bypass local loop systems to provide business with
high speed connections.
3. Enterprise connectivity: As FSO links can be installed with ease, they
provide a natural method of interconnecting LAN segments that are housed in
buildings separated by public streets or other right-of-way property.
4. Fiber backup: FSO can also be deployed in redundant links to backup
fiber in place of a second fiber link.
5. Backhaul: FSO can be used to carry cellular telephone traffic from antenna
towers back to facilities wired into the public switched telephone network.
6. Service acceleration: Instant services to the customers before fiber being
laid.

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Chapter 7
Advantages of FSO
Free space optical (FSO) systems offer a flexible networking solution
that delivers on the promise of broadband. Only free space optics or Free
Space Optics (FSO) provides the essential combination of qualities required
to bring the traffic to the optical fiber backbone – virtually unlimited
bandwidth, low cost, ease and speed of deployment. Freedom from licensing
and regulation translates into ease, speed and low cost of deployment. Since
Free Space Optics (FSO) optical wireless transceivers can transmit and
receive through windows, it is possible to mount Free Space Optics (FSO)
systems inside buildings, reducing the need to compete for roof space,
simplifying wiring and cabling, and permitting the equipment to operate in a
very favorable environment. The only essential for Free Space Optics (FSO)
is line of sight between the two ends of the link.

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Chapter 8
Free Space Optics (FSO) Security
Security is an important element of data transmission, irrespective of the
network topology. It is especially important for military and corporate applications.
Building a network on the SONA beam platform is one of the best ways to ensure that
data transmission between any two points is completely secure. Its focused
transmission beam foils jammers and eavesdroppers and enhances security. Moreover,
fSONA systems can use any signal-scrambling technology that optical fiber can use.
The common perception of wireless is that it offers less security than wire line
connections. In fact, Free Space Optics (FSO) is far more secure than RF or
other wireless-based transmission technologies for several reasons:
 Free Space Optics (FSO) laser beams cannot be detected with
spectrum analyzers or RF meters.
 Free Space Optics (FSO) laser transmissions are optical and travel
along a line of sight path that cannot be intercepted easily. It
requires a matching Free Space Optics (FSO) transceiver carefully
aligned to complete the transmission. Interception is very difficult
and extremely unlikely.
 The laser beams generated by Free Space Optics (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 Free Space Optics (FSO)
network transmissions.

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Chapter 9
FSO Challenges
The advantages of free space optical wireless or Free Space Optics (FSO)
do not come without some cost. When light is transmitted through optical fiber,
transmission integrity is quite predictable – barring unforeseen (unexpected)
events such as backhoes or animal interference. When light is transmitted
through the air, as with Free Space Optics (FSO) optical wireless systems, it
must contend with a complex and not always quantifiable subject - the
atmosphere.
1. FOG
Fig. 9 (A):- Fog
Fog substantially attenuates visible radiation, and it has a similar affect on the near-
infrared wavelengths that are employed in FSO systems. Rain and snow have little
effect on FSO. Fog being microns in diameter, it hinder the passage of light by
absorption, scattering and reflection. Dealing with fog – which is known as Mie –
scattering, is largely a matter of boosting the transmitted power. Fog can be countered
by a network design with short FSO link distances. FSO installation in foggy cities
like San Francisco has successfully achieved carrier-class reliability.

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2. Physical Obstructions
Flying birds can temporarily block a single beam, but this tends to cause
only short interruptions and transmissions are easily and automatically re-assumed.
Multi-beam systems are used for better performance.
3. Scintillation
Fig. 9(A):-Scintillation
Scintillation refers the variations in light intensity caused by atmospheric
turbulence. Such turbulence may be caused by wind and temperature gradients
which results in air pockets of varying diversity act as prisms or lenses with time
varying properties. This scintillation affects on FSO can be tackled by multi
beam approach exploiting multiple regions of space- this approach is called
spatial diversity.
4. Solar Interference
This can be combated in two ways:
 The first is a long pass optical filter window used to block all wavelengths
below 850nm(nenometre) from entering the system.
 The second is an optical narrow band filter proceeding the receive detector
used to filter all but the wavelength actually used for intersystem
communications.
5. Scattering

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Scattering is caused when the wavelength collides with the scatterer. The physical
size of the scatterer determines the type of scattering.
 When the scatterer is smaller than the wavelength-Rayleigh scattering.
 When the scatterer is of comparable size to the wavelength -Mie
scattering.
 When the scatterer is much larger than the wavelength-Non-selective
scattering
In scattering there is no loss of energy, only a directional re-distribution of energy
which may cause reduction in beam intensity for longer distance.
6. Absorption
Absorption occurs when suspended water molecules in the terrestrial atmosphere
extinguish photons. This causes a decrease in the power density of the FSO beam and
directly affects the availability of a system. Absorption occurs more readily at some
wavelengths than others.
However, the use of appropriate power, based on atmospheric conditions, and use of
spatial diversity helps to maintain the required level of network availability.
7. Building Sway / Seismic Activity
One of the most common difficulties that arises when deploying FSO links on
tall buildings or towers is sway due to wind or seismic activity Both storms and
earthquakes can cause buildings to move enough to affect beam aiming. The
problem can be dealt with in two complementary ways: through beam
divergence and active tracking
 With beam divergence, the transmitted beam spread, forming optical
cones which can take many perturbations.
 Active tracking is based on movable mirrors that control the direction in
which beams are launched.

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Chapter 10
Conclusion
FSO enables optical transmission of voice video and data through air at very
high rates. It has key roles to play as primary access medium and backup technology.
Driven by the need for high speed local loop connectivity and the cost and the
difficulties of deploying fiber, the interest in FSO has certainly picked up dramatically
among service providers world wide. Instead of fiber coaxial systems, fiber laser
systems may turn out to be the best way to deliver high data rates to your home. FSO
continues to accelerate the vision of all optical networks cost effectively, reliably and
quickly with freedom and flexibility of deployment.

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Reference
1. Vikrant kaulgnd, “Free space optics Bridges the last mile’’ ,Electronics
for u , June 2003 pp . 38-40 .
2. Andy Emmerson , “ Fibreless Optics ’’ , Everyday practical electronics
, April 2003 pp . 248 .
Websites:
3. www.fsona.com
4. www.freespaceoptics.com
5. www.freespaceoptic.com
6. www.fsocentral.com
7. www.lightpointe.com
8. www.spie.org
9. www.osa.org