Optical Fibres
Physics: Cambridge International GCSE Supplement, topic 3.2.8
Optical Fibres
Optical fibres transmit light by total internal reflection.
Cladding
- Each fibre has a core of optically dense material that is covered by a layer of cladding with a much lower optical density.
- This means that the boundary between the two materials has a very small critical angle.
Small critical angle
- Only light approaching the boundary at an angle that is very close to the normal (90 degrees to the boundary) will cross the boundary and be refracted (this light is lost).
Long distances
- Most of the light will be totally internally reflected and continue to travel through the core.
- In this way, optical fibres can transmit light over very long distances.
Test yourself on Optical Fibres
What are the key features of an optic fibre?
How is the cladding of an optic fibre different to the core?
What is meant by the phrase "a coherent bundle of fibres"?