These are sample fibre optic cables which are used for networking. 

Optical fibers are widely used in network communications, where they permit transmission over longer distances and at higher bandwidths (data rates) than wire cables. Fibers are used instead of metal wires because signals travel along them with less loss and are also immune to electromagnetic interference. This is useful for somewhere like CERN where magnets with their highly powerful magnetic fields could pose a problem.

Optical fibers typically include a transparent core surrounded by a transparent cladding material. Light is kept in the core by total internal reflection.

One of the cable installation techniques used at CERN is "blowing" the fibre optic cables down tubes (other techniques involve normal cable pulling). The "blowing" operation uses compressed air, and specifically allows to reduce working time in the delicate areas (eg areas with high radioactivity where radiation exposure needs to be kept to a minimum). For this method, microtubes are blown into the carrying tubes, then the fibre optic cables are blown into the microtubes.

Fibers that support many propagation paths are called multi-mode fibers (MMF), while those that only support a single mode are called single-mode fibers (SMF). Multi-mode fibers generally have a wider core diameter, and are used for short-distance communication links and for applications where high power must be transmitted.

Single-mode fibers are used for long distance communication links. Long distance link is related to the bandwidth itself, eg. for a 1Gbps link, the SMF is used from 10km whereas for 100Gbps, the SMF is needed from 150m. The highest the bandwidth is, the shortest distance a MMF can be used for.

Single-mode fibre have a 9 µm core, and multi-mode fibres have a 50 µm core. Both have a cladding of 125 µm diameter.

For single-mode fibres, with multiplexing, optical fibre bandwidth can now reach 100Gbps over several hundred kilometers. The next coming network interfaces will soon reach 200Gbps and later on 400Gbps.