Optical fibre

Infrared signals can also carry data along optical fibres: thin glass or plastic strands that guide the radiation around bends by repeated total internal reflection. Infrared security systems may detect the radiation associated with a warm person to trigger an alarm or light; other systems use an infrared beam and detect when it is interrupted. In each case, the equipment uses an infrared signal or a change in detected infrared to respond.

Visible light enables vision and is used in lighting, photography and cameras. It is also used to carry information through optical fibres. Light is guided along a thin glass or plastic fibre, allowing data to follow a curved route rather than travelling only in a straight line through open air.