The Versatile Link is a bi-directional digital optical data link operating at rates up to 4.8 Gbit/s and featuring radiation-resistant low-power and low-mass front-end components. The system is being ...developed in multimode or singlemode versions operating at 850 nm or 1310 nm wavelength respectively. It has serial data interfaces and is protocol-agnostic, but is targeted to operate in tandem with the GigaBit Transceiver (GBT) serializer/deserializer chip being designed at CERN. This paper gives an overview of the project status three and a half years after its launch. It describes the challenges encountered and highlights the solutions proposed at the system as well as the component level. It concludes with a positive feasibility assesment and an outlook for future project development directions.
Radiation tolerant, high speed optoelectronic data transmission links are fundamental building blocks in today's large scale High Energy Physics (HEP) detectors, as exemplified by the four ...experiments currently under commissioning at the Large Hadron Collider (LHC), see for example. New experiments or upgrades will impose even more stringent demands on these systems from the point of view of performance and radiation tolerance. This can already be seen from the developments underway for the Super Large Hadron Collider (SLHC) project, a proposed upgrade to the LHC aiming at increasing the luminosity of the machine by factor of 10 to 10{sup 35} cm{sup -2}s{sup -1}, and thus providing a better chance to see rare processes and improving statistically marginal measurements. In the past, specific data transmission links have been independently developed by each LHC experiment for data acquisition (DAQ), detector control as well as trigger and timing distribution (TTC). This was justified by the different types of applications being targeted as well as by technological limitations preventing one single solution from fitting all requirements. However with today's maturity of optoelectronic and CMOS technologies it is possible to envisage the development of a general purpose optical link which can cover most transmission applications: a Versatile Link. Such an approach has the clear advantage of concentrating the development effort on one single project targeting an optical link whose final functionality will only result from the topology and configuration settings adopted.
The LHC Bunch Clock is one of the most important accelerator signals delivered to theexperiments. Being directly derived from the Radio Frequency driving the beams in the acceleratorby a simple ...division of its frequency by a factor of 10, the Bunch Clock signal represents thefrequency at which the bunches are crossing each other at each experiment. It is thus used tosynchronize all the electronics systems in charge of event detection. Its frequency is around 40.079MHz, but varies with beam parameters (energy, particle type, etc) by a few hundreds of Hz.The present paper discusses the quality of this Bunch Clock signal in terms of jitter. It is inparticular compared to typical requirements of electronic components of the LHC detectors and putin perspective with the intrinsic jitter of the beam itself, to which this signal is related.
Particle detectors for future experiments at the HL-LHC will require new optical data transmitters that can provide high data rates and be resistant against high levels of radiation. Furthermore, new ...design paths for future optical readout systems for HL-LHC could be opened if there was a possibility to integrate the optical components with their driving electronics and possibly also the silicon particle sensors themselves. All these functionalities could potentially be combined in the silicon photonics technology which currently receives a lot of attention for conventional optical link systems. Silicon photonic test chips were designed in order to assess the suitability of this technology for deployment in high-energy physics experiments. The chips contain custom-designed Mach-Zehnder modulators, pre-designed "building-block" modulators, photodiodes and various other passive test structures. The simulation and design flow of the custom designed Mach-Zehnder modulators and some first measurement results of the chips are presented.
The present paper discusses recent advances on a Passive Optical Network inspired Timing-Trigger and Control scheme for the future upgrade of the TTC system installed in the LHC experiments' and more ...specifically the currently known as TTCex to TTCrx link. The timing PON is implemented with commercially available FPGAs and 1-Gigabit Ethernet PON transceivers and provides a fixed latency gigabit downlink that can carry level-1 trigger accept decisions and commands as well as an upstream link for feedback from the front-end electronics.
The GigaBit Laser Driver (GBLD) is a radiation tolerant ASIC which is part of the GigaBit Transceiver (GBT) chipset. It is aimed to drive both edge emitting and VCSEL laser diodes at a data rate in ...excess of 5 Gb/s. The GBLD can provide a modulation current up to 24 mA and abias current up to 43 mA. Pre- and de-emphasis functions are implemented to compensate for high external capacitive loads and asymmetric laser response. The chip is designed in a 130 nm CMOS technology and is powered by a single 2.5 V supply.
Hollow-Core Photonic-Bandgap Fibres (HC-PBGFs) offer several distinct advantages over conventional fibres, such as low latency and radiation hardness; properties that make HC-PBGFs interesting for ...the high energy physics community. This contribution presents the results from a gamma irradiation test carried out using a new type of HC-PBGF that combines sufficiently low attenuation over distances that are compatible with high energy physics applications together with a transmission bandwidth that covers the 1550 nm region. The radiation induced attenuation of the HC-PBGF was two orders of magnitude lower than that of a conventional fibre during a 67.5 h exposure to gamma-rays, resulting in a radiation-induced attenuation of only 2.1 dB/km at an accumulated dose of 940 kGy.
The LHCb experiment will upgrade its DAQ system to a trigger-less, 40 mHz readout in 2018. To be able to process the approximately 40 Tbit/s of data we will require a massive computing farm. This ...computing farm can no longer be installed underground in the vicinity of the detector anymore due to the increase in power and cooling requirements. An affordable, optical data transport solution has to be found to carry the data from the detector to the new data center on the surface. The distance to cover is 300 m with an additional 100 m of safety margin. This document covers the results of our measurements of the 4.8 Gbit/s Versatile Link signal over 400 m of OM3 and OM4 fibres.
We report on our recent investigation into the potential for using silicon-based Mach-Zehnder modulators in the harshest radiation environments of the High-Luminosity LHC. The effect of ionizing and ...non-ionizing radiation on the performance of the devices have been investigated using the 20 MeV neutron beam line at the Cyclotron Resource Centre in Louvain-La-Neuve and the X-ray irradiation facility in the CERN PH department. The devices were exposed to a total fluence and ionizing dose of 1.2x10 super(15) n cm super(?2) and 1.3 MGy respectively.
The GigaBit Laser Driver (GBLD) is a radiation tolerant ASIC designed to drive both edge emitting lasers and VCSELs at data rates up to 5 Gb/s. It is part of the GigaBit Transceiver (GBT) and ...Versatile Link projects, which are designing a bi-directional optical data transmission system capable of operating in the radiation environment of a typical HEP experiment. The GBLD can provide laser diode modulation currents up to 24 mA and laser bias currents up to 43 mA. Pre- and de-emphasis functions are implemented to compensate for high external capacitive loads and asymmetric laser response. The chip, designed in a 0.13 μm CMOS technology, is powered by a single 2.5 V power supply and can be programmed via an I 2 C interface.
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