fibre that functions as a waveguide
. They are used in medical instruments (called fibrescopes
) to examine internal organs
They are also used in short-range telecommunications
Optical fibres consist of a glass core region that is surrounded by glass cladding. The core region has a larger refractive index than the cladding, so that the light is confined to that region as it propagates along the fibre. Fibre core diameters range between 1 and 100 micrometres, while cladding diameters are between 100 and 300 micrometres.
The step-index fibre consists of a glass core with a coaxial glass or plastic cladding of lower refractive index so that total internal reflection takes place at the interface between the core and the cladding.
In graded-index fibres, the fibre is stuctured, each layer of glass having a lower refractive index than the one inside it.