10-04-2012, 11:22 AM
Laser communication systems
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INTRODUCTION
The laser communication system transmits sound or music signals through a laser beam. The intensity of the laser beam changes with the amplitude of the sound signal. The variation in the intensity of the laser beam is converted into a variation in voltage level by using a solar panel. The voltage variation on the solar panel is amplified by a low voltage audio power amplifier LM386 and reproduced by a speaker. The maximum output of audio amplifier LM386 is 1 watt, while the voltage gain is 20 to 200.
The circuit consists of a transmitter and a receiver, both built around IC LM386, powered by a 9V battery.
MECHANISM
The circuit diagram shows a laser diode(LD1) with a maximum operating voltage of around 2.6V DC and maximum operating current of 45mA is used to transmit an audio signal. The voltage divider network formed by R2, R3 & VR3 keeps the voltage as well as the current for the laser diode in the safe region.
Potentiometer VR1(10 kilo ohm) is used to change the level of the input audio signal. The audio input(Vin) is taken from the preamplifier output of the music system. Capacitor C2 & preset VR2 are used to vary the gain of the LM386.
APPLICATIONS
The technology is useful where the physical connections are impractical due to high costs or other considerations.
Typically scenarios for use are:
• LAN-to-LAN connections on campuses at Fast Ethernet or Gigabit speeds.
• LAN-to-LAN connections in a city a metropolitan area network.
• To cross a public road or other barriers which the sender and receiver do not own
• Speedy service delivery of high-bandwidth access to optical fiber networks
• Converged Voice-Data-Connection
• Temporary network installation (for events or other purposes)
• Re-establish high-speed connection quickly (disaster recovery)
• As an alternative or upgrade add-on to existing wireless technologies
• As a safety add-on for important fiber connections (redundancy)
• For communications between spacecraft including elements of a satellite constellation For inter- and intra -chip communication.
ADVANTAGES
• Ease of deployment
• License-free long-range operation (in contrast with radio communication)
• High bit rates.
• Low bit error rates.
• Immunity to electromagnetic interference.
• Full duplex operation.
• Protocol transparency.
• Very secure due to the high directionality and narrowness of the beam(s)