Medical use of optical fibres

Optical fibres are often used in medical procedures. One example is to use an endoscope to illuminate and visualise areas that couldn't normally be seen. Doctors used to have to operate to see what the problem was.

The optical fibre of an endoscope is passed down through the oesophagus to see inside the patients stomach.

If you were to see the end of the endoscope, this is what you would see:

End of an endoscope with the fibre optics and other parts labelled.

Two of the main fibre optic features used in an endoscope are cables that light up (illuminate) the inside of the stomach. The other main feature is a fibre optic viewing cable that allows you to see what the problem is:

The path light takes down the fibre optic of an endoscope.

Both of these fibre optic cables rely on total internal reflection. Without this, neither feature would work.