 An optical fiber or optical fiber 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 electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss. In addition, fibers are immune to electromagnetic interference, the problem from which metal wires suffer excessively. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry lighting or images out of confined spaces, as in the case of a fiber scope. 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 the cores around by a transparent cladding material with a lower index of refraction. Fibers are 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 the 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 1,000 meters 3,300 feet. Being able to join optical fibers with low loss is important in fiber optic communication. This is more complex than joining the 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 the 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 semipermanent 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 opics. The term was coined by Indian physicist Narendra Singh Kapini, who is widely acknowledged as the father of fiber opics.