Semiconductors and Optical Fibres

However information can also be:

magnetic in nature as found on magnetic tapes and computer hard discs or

optical in nature

So in order to use light to transmit information along a fibre, we need:

light sources to convert electrical signals into light signals

light detectors to convert light signals into electrical signals

Right now most of these "tasks" are done by semiconductors devices.
Light-Emitting diodes and laser diodes are used as light sources while photodiodes are used as detectors.

In order to understand how these devices work, we first need to understand the properties of semiconducting materials.