An
optical fiber or optical fibre is a flexible, transparent fiber made by
drawing glass (silica) or plastic to a diameter slightly thicker than
that of a human hair.Optical fibers are used most often as a means to
transmit light between the two ends of the fiber and find wide usage in
fiber-optic communications, where they permit transmission over longer
distances and at higher bandwidths (data rates) than wire cables. Fibers
are used instead of metal wires because signals travel along them with
less loss; in addition, fibers are immune to electromagnetic
interference, a problem from which metal wires suffer excessively.
Fibers are also used for illumination and imaging, and are often wrapped
in bundles so that they may be used to carry light into, or images out
of confined spaces, as in the case of a fiberscope.Specially designed
fibers are also used for a variety of other applications, some of them
being fiber optic sensors and fiber lasers.
Optical
fibers typically include a core surrounded by a transparent cladding
material with a lower index of refraction. Light is kept in the core by
the phenomenon of total internal reflection which causes the fiber to
act as a waveguide.Fibers that support many propagation paths or
transverse modes are called multi-mode fibers, while those that support a
single mode are called single-mode fibers (SMF). Multi-mode fibers
generally have a wider core diameter and are used for short-distance
communication links and for applications where high power must be
transmitted.[citation needed] Single-mode fibers are used for most
communication links longer than 1,000 meters (3,300 ft).[citation
needed]
Being
able to join optical fibers with low loss is important in fiber optic
communication.This is more complex than joining electrical wire or cable
and involves careful cleaving of the fibers, precise alignment of the
fiber cores, and the coupling of these aligned cores. For applications
that demand a permanent connection a fusion splice is common. In this
technique, an electric arc is used to melt the ends of the fibers
together. Another common technique is a mechanical splice, where the
ends of the fibers are held in contact by mechanical force. Temporary or
semi-permanent connections are made by means of specialized optical
fiber connectors.
The
field of applied science and engineering concerned with the design and
application of optical fibers is known as fiber optics. The term was
coined by Indian physicist Narinder Singh Kapany, who is widely
acknowledged as the father of fiber optics.
