Free space optics (FSO) uses visible light communication or infrared light to transmit data wirelessly over the air. It works by using a laser or LED light source to transmit data to a photodetector. FSO systems provide high-speed fiber-like bandwidth without the need for cables or licensing. Common applications include extending metropolitan networks, providing last mile access, connecting enterprise buildings, and cellular backhaul. FSO experiences less attenuation than radio frequencies and can transmit data at speeds up to 10 Gbps.

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TABLE OF CONTENTS.
1. Introduction....................................................4
2. History of FSO……………………………....4
3. Working of FSO……………………………..5
4. Method of operation…………………….5
5. Application……………………...............7
6. Optical transmission…………………………6
7. Wireless speed of light with EDFA………....7
8. Conclusion……………………………………8
9. References…………………………………….9
LIST OF FIGURES.
1. 2. FSO Block diagram…………….6
2. 3. Incident Laser beam……….....6
3. FSO internal structure………………5
4. Data passes through Layer……….7
5. Ethernet Format……………………..8
6. He-Ne laser tube……………………….5
7. Fso internal structure………………….6
8. Transmission vs Wavelength graph…...7
9. Architecture of EDFA………………....8

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1.INTRODUCTION
Free-space optical communication (FSO) systems (in space and inside the atmosphere)
have developed in response to a growing need for high-speed and tap-proof
communication systems. Links involving satellites, deep-space probes, ground stations,
unmanned aerial vehicles (UAVs), high altitude platforms (HAPs), aircraft, and other
nomadic communication partners are of practical interest. Moreover, all links can be
used in both military and civilian contexts. FSO is the next frontier for net-centric
connectivity, as bandwidth, spectrum and security issues favor its adoption as an
adjunct to radio frequency (RF) communications.
While fixed FSO links between buildings have long been established and today form a
separate commercial product segment in local and metropolitan area networks. the
mobile and long-range applications of this technology are aggravated by extreme
requirements for pointing and tracking accuracy because of the small optical beam
divergences involved.
2. HISTORY OF FREE SPACE OPTICS
Optical communication has been used thousand of year. In 1880,Alexander Graham
Bell and his assistant Charles summer tainter created photophone at Bell's newly
established laboratory in washington,Dc. Bell patented photophone, which modulated
light reflect from the sun with a voice signal and transmitted that across the free space
to a solid state dectecor.thus was born FSO(free space optics). On june 3,1880 Bell
made world’s first wireless telephone,which was used between two building at distance
213 meter.
In 1962, Dr. Erahard kube was developed first HeNe laser(HeliumNeon laser) at Bell
Telephone laboratories.
In 1962, Dr. Erahard kube was developed first HeNe laser(HeliumNeon laser) at Bell
Telephone laboratories. HeNe laser is a type of laser whose gain medium consists of a
mixture of Helium and Neon(10:1)inside a small bore capillary tube,usually excited

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byBy a DC electrical discharge,pressure maintain inside the tube is 1mm of Hg And
emitted the light at 1.15 m in the infrared specturm, was first gas laser.
FIGURE1.1 –He-Ne LASER TUBE
3.HOW FREE SPACE OPTICS WORK.
FSO technology is surprisingly simple. It's based on connectivity between FSO-based
optical wireless units, each consisting of an optical transceiver with a transmitter and a
receiver to provide full-duplex (bi-directional) capability. Each optical wireless unit
uses an optical source, plus a lens or telescope that transmits light through the
atmosphere to another lens receiving the information. At this point, the receiving lens
or telescope connects to a high-sensitivity receiver via optical fiber. This FSO
technology approach has a number of advantages: Requires no RF spectrum licensing.
Is easily upgradeable, and its open interfaces support equipment from a variety of
vendors, which helps enterprises and service providers protect their investment in
embedded telecommunications infrastructures. Requires no security software upgrades.
Is immune to radio frequency interference or saturation. Can be deployed behind
windows, eliminating the need for costly rooftop rights.
.

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FIGURE 1.2–FSO INTERNAL STRUCTURE
4. OPTICAL TRANSMISSION
By its very nature, remote sensing implies that the source being measured is some
distance away from the optical receiver. The atmospheric path between the source and
receiver will attenuate the sources signature and is likely to change its spectral shape.
These changes have important implications for developing remote sensing systems and
interpreting their data.
FIGURE 4.5 –TRANSMISSION VS. WAVELENGTH.
5. SCINTILLATION

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Performance of many laser communications systems is adversely affected by
scintillation on bright sunny days. Through a large aperture receiver, widely spaced
transmitters, finely tuned receive filtering, and automatic gain control, downtime due
to scintillation can be avoided.
6.FSO :WIRELESS AT THE SPEED OF LIGHT
Optical wireless, based on FSO-technology, is an outdoor wireless product category
that provides the speed of fiber, with the flexibility of wireless. It enables optical
transmission at speeds of up to 1.25 Gbps and, in the future, is capable of speeds of 10
Gbps using WDM.This is not possible with any fixed wireless or RF technology.
Optical wireless also eliminates the need to buy expensive spectrum (it requires no
municipal license approvals worldwide), which further distinguishes it from fixed
wireless technologies. Moreover, FSO technology’s narrow beam transmission is
typically two meters versus 20 meters and more for traditional, even newer radio-based
technologies such as millimeter-wave radio. Optical wireless products' similarities with
conventional wired optical solutions enable the seamless integration of access networks
with optical core networks and helps to realize the vision of an all-optical network
4.HOW FREE SPACE OPTICS (FSO) CAN HELP YOU.
FSO’s freedom from licensing and regulation translates into ease, speed and low cost
of deployment. Since Free Space Optics (FSO) 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 Free Space
Optics (FSO) equipment to operate in a very favorable environment. The only essential
requirement for Free Space Optics (FSO) or optical wireless transmission is line of sight
between the two ends of the link.
For Metro Area Network (MAN) providers the last mile or even feet can be the most
daunting. Free Space Optics (FSO) networks can close this gap and allow new
customers access to high-speed MAN’s. Providers also can take advantage of the

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reduced risk of installing an Free Space Optics (FSO) network which can later be
redeployed.
5.THE MARKET. WHY FREE SPACE OPTICS(FSO).
The global telecommunications network has seen massive expansion over the last few
years. First came the tremendous growth of the optical fiber long-haul, wide-area
network (WAN), followed by a more recent emphasis on metropolitan area networks
(MANs). Meanwhile, local area networks (LANs) and gigabit ethernet ports are being
deployed with a comparable growth rate. In order for this tremendous network capacity
to be exploited, and for the users to be able to utilize the broad array of new services
becoming available, network designers must provide a flexible and cost-effective
means for the users to access the telecommunications network. Presently, however,
most local loop network connections are limited to 1.5 Mbps (a T1 line). As a
consequence, there is a strong need for a high-bandwidth bridge (the “last mile” or “first
mile”) between the LANs and the MANs or WANs.
Free Space Optics (FSO) systems represent one of the most promising approaches for
addressing the emerging broadband access market and its “last mile” bottleneck. Free
Space Optics (FSO) systems offer many features, principal among them being low start-
up and operational costs, rapid deployment, and high fiber-like bandwidths due to the
optical nature of the technology.
4.METHOD OF OPERATION IN FSO.
FSO systems operate very much like a fiber optic connection using a cable. Themain
difference being the attenuation in a cable is known and controllable, whereasin a FSO
link that uses theatmosphere as the media, the exact attenuation of the link can vary by
the second and is unknowable. To make this type of system work a device known as a
laser diode , photon detector reciver, digital data.
19

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FIGURE 1.2 – FSO BLOCK DIAGRAM.
FIGURE 1.3 –INCIDENT LASER BEAM.
It consist the many lenses. Single element lens that focuses light to detector. In fact
some unique application require even more exotic optical front ends, such as in
ACTIVE system designs where the optical assembly both project project a light source
such as a laser to illuminate the object and also receives the resultant photons that are
reflected from the object.
5. SCATTERING IN FSO.

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light scattering by atmospheric gases and molecules will attenuate optical signals
between the source and receiver by redirecting photons from their propagation paths.
These same phenomena can also increase the background signals observed by a remote
sensing system by redirecting solar radiation along the propagation path towards the
receiver.
6.FREE SPACE OPTICS (FSO) APPLICATION.
1.Metro network extensions:- FSO is used to extend existing metropolitan area
fiberings to connect new networks from outside.
2.Last mile access:- FSO can be used in high-speed links to connect end users with
ISPs.
3.Enterprise connectivity:- The ease in which FSO can be installed makes them a
solution for interconnecting LAN segments, housed in buildings separated by public
streets.
4.Fiber backup:- FSO may be deployed in redundant links to backup fiber in place of
a second fiber link.
5.Backhaul:- Used to carry cellular telephone traffic from antenna towers back to
facilities into the public switched telephone networks.
6.SERVICE TYPES AND NETEORK TRANSMISSION OF FSO.
Two basic service types (switching technologies)
1.Connection-oriented
2.Connectionless
Connection-oriented -Based on circuit switching (setup, connect, tear-down)

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Example: Public Switching Telephone Network (PSTN) Originally only supported
voice Not good for bursty traffic Connectionless Based on sending datagrams
Examples: Packet, massage, burst switching Improves bandwidth and network
utilization .
7.MAC Sub layer.
In Standard Ethernet, the MAC sublayer governs the operation of the access method.
It also frames data received from the upper layer and passes them to the physical layer.
8.Frame Format.
The Ethernet frame contains seven fields: preamble, SFD, DA, SA, length or type of
protocol data unit (PDU), upper-layer data, and the CRC Ethernet does not provide any
Fig.How Data Passes Through Layers.
Each computer has a layered protocols

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mechanism for acknowledging received frames, making it what is known as an
unreliable medium. Acknowledgments must be implemented at the higher layers.
9.FREE SPACE OPTICS (FSO) APPLICATION.
1.Metro network extensions:- FSO is used to extend existing metropolitan area fiberings
to connect new networks from outside.
2.Last mile access:- FSO can be used in high-speed links to connect end users with
ISPs.
3.Enterprise connectivity:- The ease in which FSO can be installed makes them a
solution for interconnecting LAN segments, housed in buildings separated by public
streets.
Fig-Ethernet frame.
Fig-Ethernet frame.

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4.Fiber backup:- FSO may be deployed in redundant links to backup fiber in place of a
second fiber link.
5.Backhaul:- Used to carry cellular telephone traffic from antenna towers back to
facilities into the public switched telephone networks.
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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11.REFERENCES.
1. Garcia, A. and Widjaja, I, Communication Networks. New York, NY:
McGraw- Hill, 2003.
2. Keshav, S. An Engineering Approach to Computer Networking. Reading,MA:
Addison-Wesley, 1997.
3. Kumar A., Manjunath, D., and Kuri, 1. Communication Networking. San
Francisco, CA: Morgan, Kaufmans, 2004.
4. Data communication and networking.Behrouz A.Forouzan.
5. 1] .V. W. S. Chan, “Coherent optical space communications system:
Architecture and technology issues,” in SPIE Control Communication
Technol. LasER Syst.,vol. 295, 1981, pp. 10–17.
6. [2]. V. W. S. Chan, “Space coherent optical communication systems—An
introduction,” IEEE J. Light wave Technol., vol. LT-5, pp. 633–637, Apr. 1987.
7. [3] Couch, L. Digital and Analog Communication Systems. Upper Saddle River
, NJ: Prentice Hall, 2000.

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