An optical fibre is a flexible, transparent strand of silica which acts as a waveguide to facilitate the transmission of light. Each strand of fibre is approximately the size of a human hair (mm's?) and consists of an inner core and an outer cladding material.
Light travels along the core through the process of total internal reflection; the signal reinforced by the outer cladding layer which has a lower index of refraction. Transmitters and receivers on either end of the cable transfer light along the cable, and convert electronic signals into light pulses, and vice versa.
Fibre optic technology is revolutionising ICT because the infrastructure is perfectly suited to carry data both further and faster than any previously used medium. Fibre can carry larger amounts of data (more bandwidth) with less loss in the intensity of the signal (attenuation) and without electromagnetic interference. In addition, fibre is more flexible, thinner and lighter than any other telecommunication medium. Fibre optic technology can hence carry a signal at 300 000 km/s (the speed of light) along a cable that in theory has unlimited bandwidth.