Page 191 - Concise Encyclopedia of Robotics

many narrowband signals, to be sent over a single beam of light. This
method of data transmission is used in some mobile robotic systems.
A laser-communications transmitter has a signal processor or ampli-
fier, a modulator, and laser (upper part of illustration). The receiver
uses a photocell, an amplifier, and a signal processor (lower part of illus-
tration). Any form of data can be sent, including voice, television, and
digital signals. Laser communications systems can be either line-of-sight
or fiber-optic.
Input Laser Data Transmission
Laser
Signal Modulator
processor

Laser beam

Signal
processor Amplifier

Photodetector

Output
Laser data transmission

In a line-of-sight system, the beam travels in a straight line through
space or clear air. Because laser beams remain narrow for long distances,
long-range communication is possible. However, this scheme does not
work well through clouds, fog, rain, snow, or other obstructions. The
alignment of the laser and the photodetector must be precise.

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