Fiber optic

Fiber optics, also commonly called optical fiber, are conductors of electromagnetic radiation in the infrared or visible light spectra. They are made of glass or plastic of controlled refractive index, so that the light is passed along the fiber by the principle of total internal reflection. Cables using this technology can carry immense amounts of information with much less signal loss than those propagating electrons over copper.

They may also be used to carry light for illumination and for direct viewing, as in endoscopy.