Summary of the effects of radiation upon the passive optical components of the Versatile Link

Abstract

The LHC luminosity upgrade, known as the High Luminosity LHC (HL-LHC) will require high-speed optical links to read out data from its detectors. The ATLAS and CMS experiments in collaboration with CERN have developed the Versatile Link in order to address the technical issues of optical data transmission within the harsh radiation environment experienced by any experiment within the HL-LHC. Passive optical components can suffer damage in the form of reduced optical transparency (radiation induced absorption or RIA), reduced bandwidth, and mechanical damage to the components themselves and their connection hardware. This paper summarizes the results of the optical and mechanical tests that have been performed on the Versatile Link's passive optical components. The authors conclude that two single mode and two multimode fibres, as well as standard connector components, can be qualified for use in the HL-LHC environment. The qualifying fibers are: Corning SMF-28e, DrakaElite® SRH-SMF, Corning Clearcurve® OM4 multimode graded index, and DrakaElite® SRH-MMF.

Fibre Optics Cabling Design for LHC Detectors Upgrade Using Variable Radiation Induced Attenuation Model

“…Assuming maximum 0.38 dB propagation loss and 1.75 dB for five optical interconnections by 12-fibre and 24-fibre MPO ferrules, the end-to-end link loss is in the order of 3.5 dB which is below the link margin set at 3.7 dB. It worth noting that optical connectors using multi-fibre MT and MPO ferrules are shown to have negligible loss due to radiation in the presumed radiation levels [6]. …”

Readout Technologies for Future Detectors

“…The high-speed components were found to be much more rad-tolerance than the low-speed interface. So far the majority of fiber-optical data transmission in HEP experiments are relying on VCSELs and EELs [2,9]. The Si-photonics technology is relatively new to HEP; it has been explored since 2011 for use in the present and future experiments [7,10].…”

“…Versatile Link+, a custom radiation tolerant fiber-optical transceiver for the HL-LHC experiments, operates at 10.24 Gb/s per fiber [1,2]. Without significant advances in radiation tolerant data transmission technologies, more than one million optical fibers operating at 10 Gb/s will be needed to transmit 10 Pb/s off an FCC-hh detector to event building network.…”

Fast (optical) Links

“…The optical modules also become fully customized [12,13] for both the Phase-I and Phase-II constructions due to the special requirements on module dimension, channel density, and tolerance to radiation and magnetic field in particle detectors. The electricaloptical signal converters and fibers are identified in the CERN led common project Versatile Link [12,14] and the focus is now on VCSEL (vertical-cavity surface-emitting laser) and multi-mode fibers that are characterized to be radiation tolerant for applications in the LHC experiments. Given the size of these detectors and the added transmission loss due to radiation a nominal fiber length is chosen to be 150 meters in these R&D projects [15], which matches well with the short-range (SR) fiber optics data transmission in industry, mostly for data centers.…”