An optical fiber cable, also known as fiber optic cable, is a cable containing one or more optical fibers that are used to carry light. The optical fiber elements are typically coated with plastic layers. Different types of cable are used for different applications, for long distance telecommunication. Optical fiber consists of a core and a layer, selected for total internal reflection due to the difference in the refractive index between the two. In practical fibers, the cladding is coated with a layer of acrylate polymer or polyimide. This coating protects the fiber from damage but does not contribute to its optical waveguide properties, individual coated fibers then have a tough resin buffer layer and/or core tube extruded around them to form the cable core. Several layers of protective sheathing, depending on the application, are added to form the cable, rigid fiber assemblies sometimes put light-absorbing glass between the fibers, to prevent light that leaks out of one fiber from entering another. This reduces cross-talk between the fibers, or reduces flare in fiber bundle imaging applications, for indoor applications, the jacketed fiber is generally enclosed, with a bundle of flexible fibrous polymer strength members like aramid, in a lightweight plastic cover to form a simple cable. Each end of the cable may be terminated with an optical fiber connector to allow it to be easily connected and disconnected from transmitting and receiving equipment. For use in more environments, a much more robust cable construction is required. In loose-tube construction the fiber is laid helically into semi-rigid tubes and this protects the fiber from tension during laying and due to temperature changes. Loose-tube fiber may be dry block or gel-filled, dry block offers less protection to the fibers than gel-filled, but costs considerably less. Instead of a tube, the fiber may be embedded in a heavy polymer jacket. Tight buffer cables are offered for a variety of applications, Breakout cables normally contain a ripcord, two non-conductive dielectric strengthening members, an aramid yarn, and 3 mm buffer tubing with an additional layer of Kevlar surrounding each fiber. The ripcord is a cord of strong yarn that is situated under the jacket of the cable for jacket removal. Distribution cables have an overall Kevlar wrapping, a ripcord, and these fiber units are commonly bundled with additional steel strength members, again with a helical twist to allow for stretching. A critical concern in outdoor cabling is to protect the fiber from contamination by water and this is accomplished by use of solid barriers such as copper tubes, and water-repellent jelly or water-absorbing powder surrounding the fiber. Finally, the cable may be armored to protect it from environmental hazards, in September 2012, NTT Japan demonstrated a single fiber cable that was able to transfer 1 petabit per second over a distance of 50 kilometers
A TOSLINK optical fiber cable with a clear jacket. These cables are used mainly for digital audio connections between devices.
A multi-fiber cable
Left: LC/PC connectors Right: SC/PC connectors All four connectors have white caps covering the ferrules.