Fiber-optic cable is a networking medium that uses modulated light
transmissions. It can be costlier than other networking media, depending on the
purity and the size of the fiber used. The connectors that terminate fiber also
tend to be more expensive. Fiber is not susceptible to electromagnetic or radio
frequency interference. It is capable of higher data rates than any of the
other types of current networking media. As the diameter of the fiber gets
smaller, the maximum transmission rate increases.
Data for fiber-optic
cable are converted into pulses of light and this light is allowed to propagate
down the fiber.
As illustrated in Figure
, the
light-guiding parts of an optical fiber are referred to as the core and the
cladding. The core is usually very pure glass with a lower index of refraction.
When a cladding layer of glass or plastic with a low index of refraction
surrounds the core glass, light can be trapped in the fiber core. This process
is called total internal reflection, and it allows the optical fiber to act
like a light pipe that guides light for tremendous distances, even around
bends.
Fiber-optic communication is rooted in a number of inventions
made in the 19th century. It was not until the 1960s, when solid-state laser
light sources and high-quality impurity-free glasses were introduced, that
fiber-optic communication became practical. Telephone companies, who saw its
benefits for long-distance communication, pioneered its use on a widespread
basis.