MTEL Technology and Engineering

Correct Response: A. In fiber-optic telephone systems, a digital signal is transmitted by a laser through an optical cable. Because it is a digital signal, it is composed of binary digits represented by the light source turning on and off extremely rapidly. These cables contain glass fibers that are not used for conducting electrical current (B). Being digital in nature, the information is contained in the on and off switching of the light source and not in changes in wavelength (C) or color (D).