Daniel Ricci

Radiation Tolerant Optical Fibers: From Sample Testing to Large Series Production

The process of selecting, manufacturing, and installing a large quantity (2500 km) of commercially available radiation tolerant specialty fibers is described. Radiation tests of various types of fibers from different manufacturers provided sufficient understanding of the radiation effects to select the best performing fiber type. Systematic verification of a sample of each preform assured a constant quality of the series production and allowed assessing the impact of small variations in the manufacturing process on the radiation hardness and the optical transmission characteristics. The fiber cable installation technique based on microjetting and plastic cable ducts has been validated for areas with high levels of radiation.

Single-Event Upsets in photodiodes for multi-Gb/s data transmission

A Single-Event Upset study has been carried out on PIN photodiodes from a range of manufacturers. A total of 22 devices of eleven types from six vendors were exposed to a beam of 63 MeV protons. The angle of incidence of the proton beam was varied between normal and grazing incidence for three data-rates (1.5, 2.0 and 2.5 Gb/s). We report on the cross-sections measured as well as on the detailed statistics of the interactions that we measured using novel functionalities in a custom-designed Bit Error Rate Tester. We have observed upsets lasting for multiple bit periods and have measured, over a large range of input optical power, a small fraction of errors in which an upset causes a transmitted zero to be detected as a one at the receiver.

Evaluation of Multi-Gbps Optical Transceivers for Use in Future HEP Experiments

Future experiments at the European Organization for Nuclear Research (CERN) will increase the demand for highbandwidth optical links. Custom developments for deployment within the detector volumes might be based on commercially available optical transceivers (TRxs). We present our evaluation of Commercial Off-the-Shelf (COTS) multi-Gbps optical TRxs. This serves as the basis to evaluate the performance of the future Versatile Transceiver (VTRx) that is being developed at CERN in the context of the Versatile Link project. We describe the devices evaluated, the experimental set-up for parametric testing, and our analysis of the performance data.

Large-Scale Procurement of Radiation Resistant Single-Mode Optical Fibers for CERN

2400 km of special radiation resistant optical fibres were procured by CERN (European Organization for Nuclear Research), for the installation of more than 55 km of optical fibre cables in the accelerator complex underground during the Long Shutdown 1 (LS1). In the frame of this large-scale industrial production, a thorough quality assurance plan (QAP) was put in place and followed at each step of the process. In-depth qualification of optical fibres preceded the 17-month procurement process. All supplied batches were tested for their resistance to radiation, leading to more than 65 quality control irradiation tests. During the cable assembly process and the installations works, a full traceability down to the optical fibre level was ensured. The actions put in place in the frame of the QAP led to successful installation works and to full respect of the LS1 planning.

Macro-Bending Influence on Radiation Induced Attenuation Measurement in Optical Fibres

Influence of the bending radius on the measurement of radiation induced attenuation in glass optical fibres is discussed in this paper. Radiation induced attenuation measured in two single-mode fibre types shows discrepancies when coiled around a low bending radius spool: the observed attenuation is lower than expected. A series of dedicated tests reveals that this invalid measurement is related to the displacement of the mode field towards the cladding when the fibre is bent with a low radius, and to the different radiation resistances of the core and cladding glasses. For irradiation tests of optical fibres, the spool radius should therefore be carefully chosen.

CMS Tracker, ECAL and Pixel Optical Cabling: Installation and Performance Verification

The installation of 52304 optical links for the readout and control of the CMS Tracker, ECAL and Pixel detectors is complete. 768 96-way optical cables were installed and tested using an optical time-domain reflectometer. The testing was followed by connections at high density optical fibre patchpanels. Finally, a further round of testing and troubleshooting following feedback from system commissioning with the Tracker Data Acquisition was carried out. Over 90% of the faults found were recovered, resulting overall in only 0.1% of dead optical link channels in the CMS Tracker.

Integration of the CMS Tracker Optical Links

The world’s largest point-to-point optical link system is being developed at CERN for readout and control of the CMS Tracker. The optical links are currently being integrated into the Tracker sub-detector systems and preparations are underway for final cabling and connection of the Tracker in CMS at LHC Point 5. Development was recently completed on the dense, in-line optical patch-panel in addition to the back-end patch-panel. Quality assurance and quality control procedures related to cabling and connections, acceptance tests, and tests of final system performance have been defined and practiced. The recent experience during sub-detector integration and the CMS Magnet Test Cosmic Challenge is described.

CMS Optical Links : Lessons learned from Mass Production

The CMS Tracker will install over 40000 optical links in its data-readout and control system, representing an unprecedented deployment of this technology in a Particle Physics Experiment. After reviewing the Quality Process employed in this project, a summary of the performance data measured during production will be shown. The analysis of this data will then be used to illustrate how the performance of the installed system may be predicted, giving confidence that the specified functionality will be attained in the final system. Completion of the production has allowed reflection upon the processes used and improvements for future such projects will be given in the form of some lessons learned.

Potential Upgrade of the CMS Tracker Analog Readout Optical Links using Bandwidth Efficient Digital Modulation

The potential application of advanced digital communication schemes in a future upgrade of the CMS Tracker readout optical links is currently being investigated at CERN. We show experimentally that multi-Gbit/s data rates are possible over the current 40 MSamples/s analog optical links by employing techniques similar to those used in ADSL. The concept involves using one or more digitally-modulated sinusoidal carriers in order to make efficient use of the available bandwidth.

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

Foreseen upgrades over the next decades enable LHC to operate at a higher luminosity (HL-LHC). Accordingly, the optical links designed to transmit particle collision data need to be hardened against increased radiation level, allowing for a reliable communication. In this paper we study the fibre cabling design of a link between the transceiver optical front-end and the data control room. The radiation penalty calculation takes temperature drop down to ‒30°C into account. The proposed solution concatenates radiation-resistance and conventional fibres using multi-fibre interconnections. The end-to-end link loss during HL-LHC lifetime is estimated strictly less than 3.5 dB complying with predefined margin.