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Laser Communication

Laser Communication






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Laser Communication Laser Communication Presentation Transcript

  • Laser Communication
  • 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.
  • 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
  • How Does it Work? Signal Transmitter Receiver Signal Laser laser
    • Photo resistor
    High Level design Conditioning MCU MCU Conditioning Conditioning UART UART A/D PORT Laser Diode
  • What is the Transmitter?
    • The transmitter involves:
      • Signal processing electronics (analog/digital)
      • Laser modulator
      • Laser (visible, near visible wavelengths)
  • Laser Diode Laser Diodes include Photodiodes for feedback to insure consistent output.
  • 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
  • Avalanche photodiode-2 Stabilisation of working point of APD: . Gain =75 Temperature stabilisation. Thermoelectrically cooler stabilisation system is inside of APD module AVALANCHE PHOTO DIODE
  • System Comparison (OC3 1km products) OpticalAccess ICS LightPointer Transmit Power (mW) 10 (10 dBm) 100 (20 dBm) 4 (6 dBm) Beam Diverg (mrad) 2.5 11 3 Receive Area (cm^2) 52 232 200 Min Recv Power (nW) 100 (-40 dBm) 32 (-45 dBm) 50 (-43 dBm) Price $19.5k $25k $24k
  • Why Laser Communication?
    • Current high speed communications technology:
      • Radio
      • Fiber Optics
  • Laser Link Geometry Critical Design Parameters Beam Divergence = 3 mrad Diameter = 3 m Beam area = 70686 cm 2 Distance = 1km Receive area = 200 cm 2 Transmit Power Receiver sensitivity
    • 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.
    Why not Fiber Optics?
    • 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.
    Why not RF?
  • Current Applications
    • Defense and sensitive areas.
    • At airports for communication across the runways.
    • Mass communication
        • 400 TV channels
        • 40,000 phone conversations
    • NASA
      • Satellite - satellite
      • Earth - satellite
  • Groundstation Description
    • Control System (data and tracking)
    • Telescope & LASER Mounts
    • LASER & Transmission Optics
    • Receiving Package (photodetector)
    • Utilize Science Team’s Telescope & Processing Capability for LASER Communication
    • Transmission & Receiving Package.
    Satellite Description
  • Uplink/Downlink Data Processing Sequence Bits Bit Encoder to Symbol LASER Transfer Optics Channel (Atmos.) Receiving Optics Amplifier Symbol Recovery Error Correction Bits
  • Opportunities For Student Involvement
    • LASER Research
    • LASER Modulation Circuitry
    • Encoding/Decoding Circuitry
  • Contact Information
    • Matthew Johnson (mjohnson@u.arizona.edu)
    • Freddy Valenzuela (acv@bigdog.engr.arizona.edu)
    • Http://www.physics.arizona.edu/ssp/sti
    For more information regarding laser communication: