Fibre optic cabling is a type of data cabling that gives the user higher bandwidth and transmission across greater distances than could be achieved with other types of cabling and so is a popular form of cabling for computer networks, broadband and other applications.
Fibre optic cabling is made up of a core, cladding and buffer coating.
Essentially, the core carries light pulses (which contain the data) through the middle of the cable, replacing the electrical signals used in copper cabling and thereby allowing for faster transmission due to the speed of light.
The buffer coating then reflects light pulses back into the core and allows the light to 'bounce' around corners and bends providing 'total internal reflection' and acting as a 'waveguide' (so called due to the fact that light is more a 'waveform' than a particle).
Finally, the buffer coating provides the outer-most layer of fibre optic cabling and protects both the core and the cladding from damage from moisture or impact.
In this way, fibre optics are able to carry far more data and offer far less resistance than metal wires, and as they do not use electrical impulses they are also immune to electromagnetic interference and so would be un-affected by EMP.