Transcript Laser Communication PRESENTED BY, TRISHA PAUL Dept. ECE(8th sem) Roll No. 08182003028 Reg. No. 081820110199

Laser Communication
PRESENTED BY,
TRISHA PAUL
Dept. ECE(8th sem)
Roll No. 08182003028
Reg. No. 081820110199
What Is Laser Communication?
Laser communications 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.
 A laser is a device that emits light
(electromagnetic radiation) through a process
called stimulated emission.
 The term "laser" is an acronym for Light
Amplification by Stimulated Emission of
Radiation.
Light
Amplification by
Stimulated
Emission of
Radiation
Free Space Laser Communication
 Transmitting information via a laser beam
 Video
 Data
 Sound
 Terrestrial / Space based systems
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Properties of Laser Light
Laser light is very different from normal light.
 Monochromatic: One specific wavelength (Color) determined by the
amount of energy released when the electron drops to a lower orbit.
 Coherent: “Organized” -- each photon moves in step with the others. All of
the photons have wave fronts that launch in unison.
 Directional: A laser light has a very tight beam and is very strong and
concentrated. A flashlight, on the other hand, releases light in many directions,
and the light is very weak and diffuse.
To make these three properties occur takes something called stimulated
emission. This does not occur in ordinary flashlight -- in a flashlight, all of the
atoms release their photons randomly. In stimulated emission, photon emission
is organized.
DIFFERENT STEPS
 A laser makes light by passing
electricity through a gas.
 This makes the gas emit (give
out) light waves at a precise
wavelength.
 The light waves bounce back and
forth along a tube between two
mirrors.
 This encourages the gas to give
out more light exactly in step
with the original light waves. It
also amplifies (makes brighter)
the beam of light
How
Does
it Work?
What
is the
Transmitter?
► The
transmitter involves:
Transmitter
Signal
 Signal processing
electronics
Laser
(analog/digital)
Signal
 Laser Receiver
modulator
 Laser (visible, near visible wavelengths)
laser
Modulation
AM
 Easy with gas lasers, hard with diodes
PWM (Pulse Width Modulation)
PFM (Pulsed FM)
 Potentially the highest bandwidth
(>100kHz)
What is the Receiver?
► The
receiver involves:
 Telescope (referred to as ‘antenna’)
 Signal processor
 Detector
-PIN diodes
-Avalanche Photo Diodes
(APD)
-Single or multiple detectors
Often both ends will be equipped
with a receiver and transmitter
Laser Diode
Laser Diodes
include
Photodiodes for
feedback to insure
consistent output
Types of Lasers
Lasers are designated by the type of lasing material employed:

Solid-state Lasers: Lasing Material Distributed in a Solid Matrix
ruby or Nd:YAG (Neodymium: Yttrium- Aluminum Garnet ;1,064 nm).
 Gas Lasers: He, HeNe, Most common gas lasers; visible red light. CO2
lasers emit energy in the far-infrared, used for cutting.
 EXCIMER lasers: (the name is derived from the terms excited and
dimers) use reactive gases, such as chlorine and fluorine, mixed with
inert gases such as Ar, Kr or Xe. When electrically stimulated, a pseudo
molecule (dimer) is produced. When lased, the dimer produces light in
the ultraviolet range.
 Dye lasers: use complex organic dyes, such as rhodamine 6G, in
liquid solution or suspension as lasing media. They are tunable over a
broad range of wavelengths.
 Semiconductor lasers: diode lasers, are not solid-state lasers.
These electronic devices are generally very small and use low power.
They may be built into larger arrays, such as the writing source in some
laser printers or CD players.
Human Spectral Response
Laser Classes
 Class I – Sealed systems
 Class IA- Output < 4.0 mW
 Class II – Output <1mW
 Class IIIa – Output 1mW - 5mW
 Class IIIb – Output 5mW – 500mW
 Harmful to eyes, diffuse viewing OK
 Class IV – Output >500mW
 Harmful to skin and eyes, diffuse viewing
hazardous
APPLICATIONS OF LASERS
In medical
Military
Industrial and commercial
Atmospheric
In Space
MEDICAL USE
HEART TREATMENT
 The
use
of
lasers
has
revolutionized
medicine.There are six different types of lasertissue interaction illustrated as:
(Heat,Photochemistry,Photoablation,Florescence,Ioniza
tion).
 The accuracy of the laser assures that only the




desired portion of a specimen is affected by the
laser.
The strength of the laser provides any medical
treatment with adequate power to ablate the plaque.
The efficiency of the laser provides a better
medical treatment because it takes less repetitions
of the treatment to complete the procedure.
A laser beam fired into the heart can help
people suffering from angina pectoris
Lasers can be used to correct defects of the lens
and cornea as well as repair tears and holes in
the retina.
EYE TREATMENT
Industrial USE
MATERIAL PROCESSING
DRILLING
 Laser cutting,
 Laser welding,
 Laser brazing,
 Laser bending,
Blind hole obtained by using an
excimer laser beam on CFC
 Laser engraving
or marking,
 Laser cleaning,
weapons etc.
Passing hole obtained by using an
excimer laser beam on CFC
IN MILITARY
 Target designation and ranging,
 Defensive countermeasures,
 Communications
 Directed energy weapons.
.
LASER RANGEFINDER
Revolver equipped
with laser sight.
COMMERCIAL USE
HP LaserJet 4200 series printer
Laser printer
Lasers used for visual effects
during a musical performance.
Laser engraving
Atmospheric Use
Airborne Laser (ABL)
CAPABILITIES
•Operates autonomously,
above the clouds, outside the
range of threat weapons but
sufficiently close to enemy
territory
•Engages early, destroying
ballistic missiles in their boost
phase of flight over launch
area
•Cues and tracks targets,
communicating with other
joint theater assets for
layered defense system
In Space
Two-way laser communication
in space has long been a goal
for NASA because it would
enable data transmission rates
that are 10 to 1,000 times
higher than traditional radio
waves. While lasers and radio
transmissions both travel at
light-speed, lasers can pack
more data. It's similar to
moving from a dial-up Internet
connection to broadband.
The new communication system
Advantages over RF?
 Bandwidth
 for Laser Communication (LC) is 100 times greater than for
RF.
 Power
 in LC is directed at target, so much less transmission
power 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.
THANK YOU