ENVS 1200 Chapter Notes - Chapter 20: Electromagnetic Radiation, Optical Fiber
13 May 2018
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ENVS 1200 Chapter 20 Notes – Summary
Introduction
• A single fiber can carry information at rates of hundreds of millions of bits per second.
• Fiber-optic cable is nearly invulnerable to most forms of noise
• Since the signal is optical, not electrical.
• It is also difficult to tap into a fiber-optic cable, which offers some measure of security.
• At the nodes, signals are readily converted between light and electrical for
interconnection with other media types.
• Its huge data-carrying capacity makes fiber-optic technology highly desirable in many
situations.
• Etire ouities are eig rewired with fier-optic cables to provide improved
communication capability for the future.
• Electromagnetic wave transmissions do not require a specific physical medium
• Simply propagate through space or through any material that is relatively transparent to
the waves.
• For signaling purposes, the medium is space; radio waves are the carriers.
• Electromagnetic waves having frequencies above 1GHz but below the frequencies of
light are generally referred to as microwaves.
• Microwaves are the most common form of wave transmission carrier although lower-
frequency radio waves are also used.
• Microwaves are unguided, but they can be tightly focused and used point-to-point
between microwave antennas or between a microwave antenna and a satellite.
• Lower-frequency radio waves are less directional and harder to focus and require much
larger antennas.
• Recall that the size of an antenna is inversely proportional to its frequency.
• They also provide less bandwidth.
• Conversely, higher-frequency waves are more susceptible to attenuation within the
physical medium that the wave travels through.
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