Optical fiber An optical fiber is a flexible, transparent fiber made of a pure glass
(silica) not much thicker than a human hair. It functions as a waveguide, or “light pipe”,
to transmit light between the two ends of the fiber.
The field of applied science and
engineering concerned with the design and application of optical fibers is known as fiber
optics. Optical fibers are widely used in fiber-optic communications, which permits
transmission over longer distances and at higher bandwidths (data rates) than other forms
of communication. Fibers are used instead of metal wires because signals travel along
them with less loss and are also immune to electromagnetic interference. Fibers are also
used for illumination, and are wrapped in bundles so that they may be used to carry
images, thus allowing viewing in confined spaces. Specially-designed fibers are used for
a variety of other applications, including sensors and fiber lasers.
Fibers that support many propagation paths or transverse modes are called multi-mode fibers (MMF), while those that only 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.
Single-mode fibers are used for most communication links longer than 1,050 meters (3,440 ft). Joining lengths of optical fiber is more complex than joining electrical wire or cable. The ends of the fibers must be carefully cleaved, and then spliced together, either mechanically or by fusing them with heat. Special optical fiber connectors for removable connections are also available.
NASA used fiber optics in the television cameras sent to the moon. At the time, the use in the cameras was classified confidential, and only those with the right security clearance or those accompanied by someone with the right security clearance were permitted to handle the cameras.
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