Fibre cables are extremely diverse in terms of the type of fibre used the way they are constructed and the materials used as well as the number of fibres present. Optical fibres are exceedingly thin strands of silica (glass) of exceptionally high purity that transfer light from one end to the other with the least amount of loss possible.
Multimode fibre and singlemode fibre are the two most common forms of fibre.
Multiple light rays (modes) can be carried at the same time using multimode fibre which has variable optical characteristics at its core simply light traveling the shortest path (down the middle) travels the slowest.
The bigger core simplifies connections and allows for the use of lower-cost LED and VCSEL technologies that operate in the 850nm wavelength window to be utilised. Because of dispersion the range is limited and it is typically utilised as premises and data centre cabling when the distance is less than a kilometre. It is available in two core sizes: 62.5 microns and 50 microns.
Singlemode fibre has a much lower core size of 9 microns and a single light channel allowing it to traverse much longer distances of up to 100 kilometres. It is also much more cost effective than multimode fibre. These require more expensive electronics that work in multiple wavelength windows and are frequently utilised in long-distance LANs cable TV and telephony applications among other things.