An optical fiber (or optical fibre) is a flexible, transparent fiber made of high quality extruded glass (silica) or plastic, slightly thicker than a human hair. It can function as a waveguide, or “light pipe”, to transmit light between the two ends of the fiber.
Use fibers instead of metal wires because the signal travels along them with less loss and is also immune to electromagnetic interference. The fibers are also used for lighting and are wrapped into bundles so that they can be used to carry images, allowing viewing in confined spaces. Specially designed fibers are used in a variety of other applications, including sensors and fiber lasers.
Optical fibers typically include a transparent core surrounded by a transparent cladding material with a lower index of refraction. Light is kept in the core by total internal reflection. This causes the fiber to act as a waveguide. 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).
The length of the fiber is more complex than connecting the wires or cables. The ends of the fibers must be carefully cut and then stitched together mechanically or by combining them with heat. A special fiber connector for detachable connections is also available.