How does fiber actually work? When a device like your computer has information to send, that data starts out as electrical energy. A laser in the computer converts the signals to photons – tiny particles of electromagnetic energy, otherwise known as light – and sends them in rapid succession down the core of the hair-thin fiber. Photons travel in waves through the inner core of the fiber. Because this core region has higher refractive index (i.e. light travels more slowly) than does the fiber’s outer cladding, the light signal is focused within the core and prevented from radiating out of the fiber. In addition, fiber cores are made from very high purity materials (typically Silica and Germania) to assure that the light energy is not absorbed or scattered by impurities. Radiation, absorption, and scattering are all forms of energy loss, also known as attenuation. By keeping such losses as low as possible, fiber allows light and the information it carries to travel great distances from the original source.