How does fibre-optic technology work?
A fibre-optic cable is made of glass drawn into a very thin strand, its thickness comparable to a human hair. The glass strand (known as the core) is coated with two layers of plastic (called the cladding). The cladding absorbs no light from the core, creating the equivalent of a mirror around the glass strand. This mirror creates total internal reflection, so that light travelling through the fibre bounces off it at shallow angles and stays completely within the core. This means that though the fibre may be many miles long, light can still pass through it. To use a fibre-optic cable for communications, any analogue signals (such as voice) are first translated into digital signals. An LED or laser at one end of the fibre switches on and off to send a light signal representing each bit. An optical receiver at the other end decodes these signals and converts them back. Modern fibre systems can transmit billions of bits per second with a single laser turning on and off several billions of
