EN/EL has installed and commissioned a large amount of optical fibers in the LHC machine and experiments allowing for high speed data communication over a flexible network in areas with ionising radiation. After a short introduction on optical communication and fiber blowing experience at CERN, this seminar will focus on the specialty fibers which have been designed to give low attenuation of light even at very high radiation doses summarizing the last 5 years of R&D in this area. The seminar is accessible for non-experts in the field.