1.  Presented By: Prabindra Kunwar
 Course: Bsc IT
 Roll no : 110315717
 Sec : D

2.  INTRODUCTION
 BRIEF OVERVIEW
 USES AND TECHNOLOGY
 OBJECTIVES
 ADVANTAGES
 LIMITATIONS
 CONCLUSION

3.  FSO is a line-of-sight technology
which uses LASERS and Photo
detectors to provide optical
connections between two points—
without the fiber.
 FSO can transmit data, voice or video
at speeds capable of reaching 2.5
Gbps.Products capable of speeds
upto10 Gbps are expected to hit the
markets within one year.
 FSO units consist of an optical
transceiver with a laser (transmitter)
and a Photo detector (receiver) to
provide full duplex (bi-directional)
capability.
 FSO systems use invisible infrared
laser light wavelengths in the 750nm
to 1550nm range.

4.  Optical communications, in various forms, have
been used for thousands of years. The Ancient
Greeks polished their shields to send signals during
battle. In the modern era, semaphores and wireless
solar telegraphs called heliographs were
developed, using coded signals to communicate
with their recipients.
 The invention of lasers in the 1960s revolutionized
free space optics. Military organizations were
particularly interested and boosted their
development. However the technology lost market
momentum when the installation of optical fiber
networks for civilian uses was at its peak.

5. Birth of Laser FSO Communications
In the mid-1960's NASA initiated
experiments to utilize the laser as
a means of communication
between the ground and space.
Gemini-7

6.  Free-space point-to-point optical links can be
implemented using infrared laser light, although low-
data-rate communication over short distances is possible
using LEDs.
 Free Space Optics are additionally used for
communications between spacecraft.
 Maximum range for terrestrial links is in the order of 2 to
3 km,but the stability and quality of the link is highly
dependent on atmospheric factors such as rain, fog, dust
and heat.
 In outer space, the communication range of free-space
optical communication is currently in the order of several
thousand kilometers,but has the potential to bridge
interplanetary distances of millions of kilometers, using
optical telescopes as beam expanders.

7.  LAN-to-LAN connections on campuses at Fast
Ethernet or Gigabit Ethernet speeds.
 LAN-to-LAN connections in a city, a metropolitan area network
 To cross a public road or other barriers which the sender and
receiver do not own.
 Speedy service delivery of high-bandwidth access to optical
fiber networks.
 Converged Voice-Data-Connection.
 Temporary network installation (for events or other purposes).
 Reestablish high-speed connection quickly (disaster recovery)
 As an alternative or upgrade add-on to existing wireless
technologies.
 As a safety add-on for important fiber connections (redundancy)
 For communications between spacecraft, including elements of
a satellite constellation.

8.  No licensing required.
 Wireless communicate from A to B.
 High bit rate (10 Mbps to 2.5 Gbps).
 Low error bit rates .
 Set up a link in a few days.
 The lasers used are eye safe.
 Installation cost is very low.
 Highly secure transmission possible.
 High data rates,upto 2.5 Gbps at present and 10 Gbps in
the near future.
 Very secure due to the high directionality and narrowness
of the beam.

9. THE FOLLWING FACTORS CAN CAUSE HIGH ERROR BIT-
RATES..
 Fog:
The major challenge to FSO
communications is fog. The primary way to
counter fog when deploying FSO is through a
network design that shortens FSO link
distances and adds network redundancies.
FSO installations in foggy cities such as San
Francisco have successfully achieved carrier-
class reliability.
 Absorption:
Absorption occurs when suspended
water molecules in the terrestrial atmosphere
extinguish photons. This causes a decrease
in the power density (attenuation) of the FSO

10. Physical obstructions:
Flying birds can temporarily block a single beam,
but this tends to cause only short interruptions, and
transmissions are easily and automatically resumed.
Building sway/ seismic activity:
The movement of buildings can upset receiver
and transmitter alignment.
Safety:
To those unfamiliar with FSO, safety is often a
concern because the technology uses lasers for
transmission.
Scintillation:
Heated air rising from the earth or man-made
devices such as heating ducts creates temperature
variations among different air pockets. This can cause
fluctuations in signal amplitude which leads to image
fluctuations at the FSO receiver end.

11. Free-space optical communication (FSO) is an optical communication technology that
uses light propagating in free space to transmit data for telecommunications or computer
networking. "Free space" means air, outer space, vacuum, or something similar. This
contrasts with using solids such as optical fiber cable or an optical transmission line. The
technology is useful where the physical connections are impractical due to high costs or
other considerations