The Invisible Web

There is an invisible web beneath CERN that keeps the entire system going. It often goes unnoticed, yet is responsible for transmitting the vast amounts of data produced at CERN: the optical fibre network.


CERN’s 35,000 km of optical fibres are also used to synchronise the accelerators, take measurements of the beams and to send controls to the LHC. The network is maintained by a team of seven specialists working in the Cabling and Optical Fibres Section of the Engineering Department, while another eight specialists are responsible for copper control and direct current (DC) power cabling (412,000 cables at CERN). Although their work is essential to keep the LHC running, their record-breaking developments often go unspoken. In a recent seminar held on 14 October, the Optical Fibre team had the opportunity to present their exceptional work with radiation-resistant optical fibres.

Daniel Ricci at the CCC optical fibre “starpoint”, which serves the LHC installations and the computing centre in Meyrin.
“Over the past 7 years, we have developed special optical fibres that can resist the radiation levels of the LHC,” says Daniel Ricci, leader of the Cabling and Optical Fibre section. “The qualification testing for these fibres is now being finalised.” Over 2,500 km of special radiation-resistant optical fibres have been installed in the LHC, and their success has garnered the interest of other institutes dealing with radiation. Their most recent work has been done in collaboration with the International Thermonuclear Experimental Reactor (ITER).

The team has also improved the blowing technique used to install optical fibre cables. Industry can typically blow optical fibre lines a few hundred metres at a time, yet the length between sectors in the LHC is approximately 3.3 km! “In order to maintain the optical fibres while the LHC is in operation, we had to develop our own method to blow lines over this record-breaking distance in a single attempt,” says Ricci.

Layout of the optical fibre network at CERN.

The optical fibre network at CERN is constantly evolving. Every time a new project is developed or a new building is constructed, new optical fibres have to be laid out. “The installation of optical fibres never ends – there are always new projects, modifications of existing projects, and systems that need their copper cabling updating,” says Ricci. In the long term, Ricci and his team would like to provide the SPS with an optical fibre infrastructure similar to that of the LHC. “The SPS currently has optical fibres running between specific points and the central control station. Extending the optical fibre network around the whole circumference of the SPS would certainly be a major improvement,” concludes Ricci.

The Cabling and Optical Fibre section is going to be particularly busy during the upcoming Christmas technical stop. They will be preparing for major works that are planned for the 2012 shutdown, laying the groundwork for the new equipment, and installing a series of cable trays and racks at Point 7 and Point 8 of the LHC.


Did you know?

Optical fibres have a long history at CERN, which was one of the first institutions in Europe to use them for telecommunications. The first optical fibre was used 32 years ago for the synchronisation of the SPS accelerator. It covered the distance between Prévessin and Meyrin and was the longest optical fibre in Europe at that time.

by Katarina Anthony