This document discusses free space laser communication. It begins with an introduction to lasers and their basic principles. Free space laser communication works by transmitting information such as video, data, and sound via modulated laser beams through the atmosphere. Key components of the system include a transmitter with a laser and modulator, and a receiver with a telescope and detector. Laser communication has applications in areas where radio frequency and fiber optic links are not practical, and offers advantages like higher bandwidth and directivity compared to RF. However, atmospheric effects can cause attenuation and limitations for terrestrial applications.

1. FREE SPACE LASER
COMMUNICATION
PREPARED BY:
M.SRIKANTH REDDY

2. CONTENTS
 Abstract
 Introduction
 Basic Principle
 What is laser Communication?
 Free Space Laser Communication
 Why Laser Communication?
 Laser Communication System
 Current Application
 Advantages
 Dis Advantages
 Conclusion
 References

3. ABSTRACT
 Lasers have been considered for space communications since their realization in 1960. However, it was
soon recognized that although the laser had potential for the transfer of data at extremely high rates,
specific advancements were needed in component performance and systems engineering, is particularly
for space-qualified hardware.
 In this context, Vehicular Ad hoc Networks’ are emerging as a new class of wireless network, the
spontaneously formed between moving vehicles equipped the with wireless interfaces that could have
similar or different radio interface technologies, the communication the employing short-range to
medium-range communication systems. A VANET is a form of mobile add hold network, providing is
communications among nearby vehicles and between vehicles and nearby the fixed equipment on the
roadside.

 Vehicular networks are a novel class of wireless networks that have emerged thanks to advances in
wireless technologies and the automotive industry. Vehicular networks are spontaneously formed between
moving vehicles equipped with wireless interfaces that could be of homogeneous is the the
heterogeneous technologies. These networks, also known as VANETs, are considered as one of the ad hoc
network

4. INTRODUCTION
LASER?
‘Light Amplification by Stimulated Emmission of Radiation’
BASIC PRINCIPLE
 Absorption
 Spontaneous Emission
 Stimulated Emission
 Population Inversion

5. What is Laser Communication?
 Laser communication systems are wireless connections
through the atmosphere.They work similarly to fiber
optic links,except the fact that in lasers,beam is
transmitted through free space.

6. Free Space Laser Communication
■Transmitting information via a laser beam
 Video
 Data
 Sound
■Terrestrial/Space based systems

7. How does it work?

8. Transmitter
The transmitter involves:
 Signal Processing electronics(Analog/Digital)
 Laser modulator
 Laser(visible,near visible wavelengths)

9. Receiver
The receiver involves:
 Telescope(referred to as antenna)
 Signal processor
 Detector

10. Ruby Laser

11. Laser Diode
 “Laser diodes
include
Photodiodes
for feedback
to insure
consistent
output”

12. Modulation
■AM
 Easy with gas lasers,hard with diodes
■PWM(Pulse Width Modulation)
■PFM(Pulsed FM)
 Potentially the highest bandwidth(>100 KHz)

13. Why laser Communication?
 Current high speed comminication technology:
■Radio
■Fiber Optics

14. Why not Fiber optics?
■Not always possible to lay fiber lines
■Satellites
■Combat zones
■Physically/Economically not practical
■Emergencies
 LC being incorporated into fiber optic networks when fiber is
not practical

15. Why not RF?
 Bandwidth
■ for laser communication (LC) is 100 tmes greater than
for RF
 POWER
■In LC is directed at target,so much less transmitted power is
required.Also the power loss is less.
 SIZE/WEIGHT
■LC antenna is much smaller than RF.
 SECURITY
■Due to low divergence of laser beam,LC is more secure than
RF.

16. Applications
 Defence and sensitive areas.
 FSO communication.
 At airports for communication across
the runways.
 Mass communication.
■ 400 TV channels
■40,000 phone conversations
 NASA
■satellite-satellite
■Earth-satellite

17. Advantages
 Ease of development
 Can be used to power devices
 License-free long-range operation(in contrast with radio
communication)
 High bit rates
 Low bit error rates
 Immunity to electro magnetic interference
 Full duplex operation
 Protocol transparency
 No fresnel zone necessary

18. Disadvantages
 For terrestrial applications the principle limiting factors are:
 Beam dispersion
 Atmospheric absorption
 Rain
 Fog (10..~100 dB/km attenuation)
 Snow
 Scintillation
 Interference from background light sources (including the sun)
 Shadowing
 Pointing stability in wind
 Pollution/smog

19. Conclusion
 With the dramatic incerase in the drama handling
requirements for satellite communication services,laser.
 Inner satellite links offer an attractive alternative to offer with
RF with virtually unlimited potential and an unregulated
spectrum.
 The system angld component technology necessary for
successful inter satellite link exists today.

20. References
 Mathew Johnson (mjohnson@u.arizona.edu)
 Freddy Valenzuela
(acv@bigdog.engr.arizona.edu)
 http://www physics.arizona.edu/ssp/sti