A flexible, transparent cable made of glass (silica) or plastic, slightly thicker than a human hair, that includes a transparent core surrounded by a transparent cladding material. Widely used in fiber-optic communications, optical fibers function as a waveguide, or “light pipe”, to transmit light over long distances and at high bandwidths (data rates). They have replaced metal wires because signals travel along them with less loss and are also immune to electromagnetic interference.