Laser Communication


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  • Laser Communication

    1. 1. Laser Communication
    2. 2. What Is Laser Communication? <ul><li>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. </li></ul>
    3. 3. L ight A mplification by S timulated E mission of R adiation
    4. 4. Free Space Laser Communication <ul><li>Transmitting information via a laser beam </li></ul><ul><ul><li>Video </li></ul></ul><ul><ul><li>Data </li></ul></ul><ul><ul><li>Sound </li></ul></ul><ul><li>Terrestrial / Space based systems </li></ul>010001100110111011001111001010000010101110010001111001011011
    5. 5. How Does it Work? Signal Transmitter Receiver Signal Laser laser
    6. 6. <ul><li>Photo resistor </li></ul>High Level design Conditioning MCU MCU Conditioning Conditioning UART UART A/D PORT Laser Diode
    7. 7. What is the Transmitter? <ul><li>The transmitter involves: </li></ul><ul><ul><li>Signal processing electronics (analog/digital) </li></ul></ul><ul><ul><li>Laser modulator </li></ul></ul><ul><ul><li>Laser (visible, near visible wavelengths) </li></ul></ul>
    8. 8. RUBY LASER
    9. 9. Laser Diode Laser Diodes include Photodiodes for feedback to insure consistent output.
    10. 10. Modulation <ul><li>AM </li></ul><ul><ul><li>Easy with gas lasers, hard with diodes </li></ul></ul><ul><li>PWM (Pulse Width Modulation) </li></ul><ul><li>PFM (Pulsed FM) </li></ul><ul><ul><li>Potentially the highest bandwidth (>100kHz) </li></ul></ul>
    11. 11. What is the Receiver? <ul><li>The receiver involves: </li></ul><ul><ul><li>Telescope (referred to as ‘antenna’) </li></ul></ul><ul><ul><li>Signal processor </li></ul></ul><ul><ul><li>Detector </li></ul></ul><ul><li>Often both ends will be equipped </li></ul><ul><li>with a receiver and transmitter </li></ul>- PIN diodes -Avalanche Photo Diodes (APD) -Single or multiple detectors
    12. 12. 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
    13. 13. 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
    14. 14. Why Laser Communication? <ul><li>Current high speed communications technology: </li></ul><ul><ul><li>Radio </li></ul></ul><ul><ul><li>Fiber Optics </li></ul></ul>
    15. 15. 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
    16. 16. <ul><li>Not always possible to lay fiber lines </li></ul><ul><ul><li>Satellites </li></ul></ul><ul><ul><li>Combat zones </li></ul></ul><ul><ul><li>Physically / Economically not practical </li></ul></ul><ul><ul><li>Emergencies </li></ul></ul><ul><li>LC being incorporated into fiber optic networks when fiber is not practical. </li></ul>Why not Fiber Optics?
    17. 17. <ul><li>Bandwidth </li></ul><ul><ul><li>for Laser Communication (LC) is 100 times greater than for RF. </li></ul></ul><ul><li>Power </li></ul><ul><ul><li>in LC is directed at target, so much less transmission power required. Also the power loss is less. </li></ul></ul><ul><li>Size / Weight </li></ul><ul><ul><li>LC antenna is much smaller than RF. </li></ul></ul><ul><li>Security </li></ul><ul><ul><li>Due to low divergence of laser beam, LC is more secure than RF. </li></ul></ul>Why not RF?
    18. 18. Current Applications <ul><li>Defense and sensitive areas. </li></ul><ul><li>At airports for communication across the runways. </li></ul><ul><li>Mass communication </li></ul><ul><ul><ul><li>400 TV channels </li></ul></ul></ul><ul><ul><ul><li>40,000 phone conversations </li></ul></ul></ul><ul><li>NASA </li></ul><ul><ul><li>Satellite - satellite </li></ul></ul><ul><ul><li>Earth - satellite </li></ul></ul>Earth
    19. 19. Groundstation Description <ul><li>Control System (data and tracking) </li></ul><ul><li>Telescope & LASER Mounts </li></ul><ul><li>LASER & Transmission Optics </li></ul><ul><li>Receiving Package (photodetector) </li></ul><ul><li>Utilize Science Team’s Telescope & Processing Capability for LASER Communication </li></ul><ul><li>Transmission & Receiving Package. </li></ul>Satellite Description
    20. 20. Uplink/Downlink Data Processing Sequence Bits Bit Encoder to Symbol LASER Transfer Optics Channel (Atmos.) Receiving Optics Amplifier Symbol Recovery Error Correction Bits
    21. 22. Opportunities For Student Involvement <ul><li>LASER Research </li></ul><ul><li>LASER Modulation Circuitry </li></ul><ul><li>Encoding/Decoding Circuitry </li></ul>
    22. 23. Contact Information <ul><li>Matthew Johnson ( </li></ul><ul><li>Freddy Valenzuela ( </li></ul><ul><li>Http:// </li></ul>For more information regarding laser communication: