The Collaborative International Dictionary of English v.0.48:

Fiber optics \Fi"ber op`tics\,, n.
   that branch of optics which studies the transmission of light
   through thin transparent fibers.

   Note: Light transmission through optical fibers has become an
         important means of data and telephone signal
         transmission, in some areas superseding the carrying of
         vioce and data signals through electrical pulses over
         copper wire. It is also used for directly carrying
         images from otherwise inaccessible locations, as from
         inside the body, for medical procedures. Light
         transmission via fiber optics for data transmission
         uses an optical fiber made of specially purified
         glass with low light absorption characteristics.
         [PJC]

WordNet (r) 3.0 (2006):

fiber optics
    n 1: the transmission of light signals via glass fibers [syn:
         fiber optics, fiberoptics, fibre optics,
         fibreoptics]

The Free On-line Dictionary of Computing (30 December 2018):

fiber optics

    US spelling of "fibre optics".  See optical
   fibre.

   (1997-03-31)