Optic fibre cables are comprised of four layers. Data is transferred using beams of light by utilising an effect known as total internal reflection.
Light travels into the glass core, and so long as it is above the critical angle, total internal reflection will occur, causing light to reflect off of the inside of the glass core repeatedly until it reaches the other end.
There are a number of different types of data transmission cables. Among them are: coaxial cables, twisted pairs, and optical fibres. I will give an in-depth description and comparison for each of them.
This type of cable is comprised of four layers. The innermost, is a copper wire which is the conductor, and carries the signal. This is then covered by a dielectric insulating layer, which has a copper braid wrapped around it, with a further outer protection and insulation layer on the outside of that. The copper braid acts as a screen, which greatly reduces leakage in and out of the cable.