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Laser Communication

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What Is Laser Communication? Laser communications systems are wireless connections through the atmosphere. They work similarly to fiber optic links, except the fact ... – PowerPoint PPT presentation

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Title: Laser Communication


1
Laser Communication

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

2
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.

3
  • Light
  • Amplification by
  • Stimulated
  • Emission
    of

  • Radiation

4
Free Space Laser Communication
  • Transmitting information via a laser beam
  • Video
  • Data
  • Sound
  • Terrestrial / Space based systems

01000110011011101100111100101000001010111001000111
1001011011
5
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.

6
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

7
(No Transcript)
8
How Does it Work?
What is the Transmitter?
  • The transmitter involves
  • Signal processing electronics (analog/digital)
  • Laser modulator
  • Laser (visible, near visible wavelengths)

Laser
Signal
Transmitter
Signal
Receiver
laser
9
Modulation
  • AM
  • Easy with gas lasers, hard with diodes
  • PWM (Pulse Width Modulation)
  • PFM (Pulsed FM)
  • Potentially the highest bandwidth (gt100kHz)

10
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

11
Laser Diode
Laser Diodes include Photodiodes for feedback to
insure consistent output
12
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 NdYAG (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.

13
Human Spectral Response
14
Laser Classes
  • Class I Sealed systems
  • Class IA- Output lt 4.0 mW
  • Class II Output lt1mW
  • Class IIIa Output 1mW - 5mW
  • Class IIIb Output 5mW 500mW
  • Harmful to eyes, diffuse viewing OK
  • Class IV Output gt500mW
  • Harmful to skin and eyes, diffuse viewing
    hazardous

15
APPLICATIONS OF LASERS
  • In medical
  • Military
  • Industrial and commercial
  • Atmospheric
  • In Space

16
MEDICAL USE
HEART TREATMENT
  • The use of lasers has revolutionized
    medicine.There are six different types of
    laser-tissue interaction illustrated as
  • (Heat,Photochemistry,Photoablation,Florescence,Ion
    ization).
  • 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
17
MATERIAL PROCESSING
Industrial USE
DRILLING
  • Laser cutting,
  • Laser welding,
  • Laser brazing,
  • Laser bending,
  • Laser engraving or marking,
  • Laser cleaning, weapons etc.

Blind hole obtained by using an excimer laser
beam on CFC
Passing hole obtained by using an excimer laser
beam on CFC
18
IN MILITARY
  • Target designation and ranging,
  • Defensive countermeasures,
  • Communications
  • Directed energy weapons.
  • .

LASER RANGEFINDER
Revolver equipped with laser sight.
19
COMMERCIAL USE
HP LaserJet 4200 series printer
Laser printer
Lasers used for visual effects during a musical
performance.
Laser engraving
20
Atmospheric Use
CAPABILITIES
Airborne Laser (ABL)
  • 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

21
 The new communication 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.
22
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.

23
  • THANK YOU
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