Waves

Question 1

What is Modal Dispersion and how can it be stopped?

Answer 1

Light rays enter the fibre at different angles, and so take different paths. So, rays will reach the end at different times.
Prevent it by making the fibres as thin as possible.

Question 2

What is Material Dispersion and how can it be stopped?

Answer 2

Light of different wavelengths travel at different speeds through a fibre.
Prevent it by using monochromatic light.

Question 3

What is pulse broadening?

Answer 3

Caused by both types of dispersion, makes the signal broader at the end. Broadened pulses can overlap and confuse the signal.

Question 4

What is an optical fibre repeater/relay?

Answer 4

It boosts/regenerates the signal, which reduces signal degradation by absorption and dispersion.

Question 5

What is absorption?

Answer 5

Some energy from the rays are absorbed by the fibre, reducing the amplitude of the signal.

Question 6

What is Cladding used for?

Answer 6

Surrounds the core. It has a lower refractive index than the core to allow for TIR, protection from scratches which could allow rays to escape.