optical fiber

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A flexible optically transparent fiber, usually made of glass or plastic, through which light can be transmitted by successive internal reflections.

Wiktionary

1. n. Alternative form of optical fibre.

GNU Webster's 1913

1. n. (Communications) A thin fiber of very pure glass used to carry signals transmitted by means of light. It has much greater information-carrying capacity than a copper wire, and in the 1990's became a dominant means of transmitting telephone communications over long distances.

WordNet 3.0

1. n. a very thin fiber made of glass that functions as a waveguide for light; used in bundles to transmit images