Presentation on theme: "Laser Communication PRESENTED BY, TRISHA PAUL TRISHA PAUL Dept. ECE(8th sem) Dept. ECE(8th sem) Roll No. 08182003028 Roll No. 08182003028 Reg. No. 081820110199."— Presentation transcript:
Laser Communication PRESENTED BY, TRISHA PAUL TRISHA PAUL Dept. ECE(8th sem) Dept. ECE(8th sem) Roll No Roll No Reg. No Reg. No
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.
L ight A mplification by S timulated E mission of R adiation
Free Space Laser Communication Transmitting information via a laser beam Video Data Sound Terrestrial / Space based systems
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? Signal Transmitter Receiver Signal Laser laser What is the Transmitter? ► The transmitter involves: Signal processing electronics (analog/digital) Laser modulator Laser (visible, near visible wavelengths)
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 Often both ends will be equipped with a receiver and transmitter - - PIN diodes -Avalanche Photo Diodes (APD) -Single or multiple detectors
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. CO 2 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 The use of lasers has revolutionized medicine. There are six different types of laser- tissue 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. HEART TREATMENT EYE TREATMENT
MATERIAL PROCESSING Laser cutting, Laser welding, Laser brazing, Laser bending, Laser engraving or marking, Laser cleaning, weapons etc. Industrial USE DRILLING Blind hole obtained by using an excimer laser beam on CFC 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 Lasers used for visual effects during a musical performance. HP LaserJet 4200 series printer Laser printer Laser engraving
Atmospheric Use 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 CAPABILITIES Airborne Laser (ABL)
The new communication system The new communication system 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. In Space
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. Advantages over RF?