R&D for Optical Links

We are working on developing radiation-hard optical links for the HL-LHC

Previous work

We collaborated on the CERN Versatile Link project which is developing optical links which will be used for all the LHC experiments. We are responsible for all aspects of optical fibres, connectors and cables. We have undertaken research to determine the radiation tolerance of single mode and multimode optical fibres at cold temperatures. The beneficial annealing of the radiation damage is slowed down at low temperature, therefore we had to make a radiation hard cooling system to perform tests at a suitable nuclear reactor facility.

We have collaborated with a fibre manufacturer Prysmian to study the effect of radiation on the fibre bandwidth. We have also studied the effects of radiation on the mechanical reliability of the fibre core and cladding. This has enabled us to qualify suitable fibres for use inside trackers at the HL-LHC.

Todd Huffman with radiation test set-up: Arrangement for cold fibre test used for gamma radiation studies at SCK in Belgium

Current work

We are collaborating on the CERN Versatile Link Plus project to develop radiation-hard optical links for the LHC Phase II tracker upgrades. We are responsible for the reliability studies of the on-detector optoelectronics. This is a critical issue as we will have no access to these devices once they are installed in the ATLAS detector. We are performing a series of accelerated ageing studies on VCSELs (semiconductor lasers) and otpical transceivers which house the VCSELs and laser driver ASIC (lpGBLD10), the p-i-n photo-diode and the GBTIA receiver ASIC.

We have a well-equipped lab with a large environmental chamber, Optical Spectrum Analyser, Optical Time Domain Reflectometer (OTDR), optical probes and arrays of photodiodes for optical power measurements. We also have different types of fibre pull testing machines.
Environmental Chamber

Key References

  1. The radiation induced attenuation of optical fibres below −20°C exposed to lifetime HL-LHC doses at a dose rate of 700 Gy(Si)/hr, 20012 JINST 7 C01047, http://iopscience.iop.org/article/10.1088/1748-0221/7/01/C01047/meta
  2. A Study of the effect of a 500 kGy(Si) radiation does on the bandwidth of a radiation hard multi-mode fibre, 2012_JINST_7_P10021, http://dx.doi.org/10.1088/1748-0221/7/10/P10021
  3. VCSEL reliability in ATLAS and development of robust arrays, 2012_JINST_7_C01098, http://dx.doi.org/10.1088/1748-0221/7/01/C01098