Optical fibres rely on total internal reflection for their operation.

An optical fibre is a thin rod of high-quality glass. Light/infrared getting in at one end undergoes repeated total internal reflection and emerges at the other end.

Notice that the light refracts towards the normal as it enters the optical fibre.

Notice what happens when the light hits the end of the fibre. The angle of incidence is now less than the critical angle and the light refracts away from the normal into the air. You may be expected to complete a diagram similar to the one above in an exam.

Optical fibres work even when the fibre is bent.