optical fiber

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A flexible transparent fiber of extremely pure glass or plastic, generally between 10 and 200 microns in diameter, through which light can be transmitted by successive internal reflections, commonly used in telecommunications.

from the GNU version of the Collaborative International Dictionary of English.

• noun (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Alternative form of optical fibre.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

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