S Papadopoulos

Versatile Transceiver developments

SLHC experiment upgrades will make substantial use of optical links to enable high-speed data readout and control. The Versatile Link project will develop and assess optical link architectures and components suitable for deployment at SLHC. The on-detector element will be a bidirectional opto-electronic module: the Versatile Transceiver (VTRx) that will be based on a commercially available module type minimally customized to meet the constraints of the SLHC on-detector environment in terms of mass, volume, power consumption, operational temperature and radiation environment. This paper brings together the status of development of the VTRx in terms of packaging, environmental testing and functional testing.

Single-Event Upsets in Photoreceivers for Multi-Gb/s SLHC Data Transmission

A 63 MeV proton beam was used to perform a single event upset (SEU) test on a candidate component for a future high luminosity large hadron collider (HL-LHC) high speed optical. An in-lab error injector was used to show that 1-0 bit errors are caused by the amplifiers response to the large signal caused by a single event transient (SET) in the photodiode.

The versatile transceiver proof of concept

SLHC experiment upgrades will make substantial use of optical links to enable high-speed data readout and control. The Versatile Link project will develop and assess optical link architectures and components suitable for deployment at SLHC. The on-detector element will be bidirectional optoelectronic module: the Versatile Transceiver that will be based on a commercially available module type minimally customized to meet the constraints of the SLHC on-detector environment in terms of mass, volume, power consumption, operational temperature and radiation environment. We report on the first proof of concept phase of the development, showing the steps towards customization and first results of the radiation resistance of candidate optoelectronic components.

Modal Dispersion Mitigation in Standard Single-Mode Fibers at 850 nm With Fiber Mode Filters

We investigate the possibility of using a fiber which supports only the fundamental LP01 mode at 850 nm as a mode filter to overcome modal dispersion in standard single-mode fiber links that employ either multitransverse or single-transverse-mode vertical-cavity surface-emitting lasers. The individual power penalties due to modal noise and modal crosstalk effects in the link are investigated.

Versatile transceiver development status

The Versatile Link common project is developing optical link architectures and components to be used for readout and control of future HL-LHC experiments. The on-detector opto-electronic module, the Versatile Transceiver (VTRx), is derived from an industry standard module type and is adapted through minimal customization to the requirements dictated by the HL-LHC-specific front-end environment. We present the methods and results of the functional tests carried out on the transceiver components and summarize the development status of the different VTRx variants. Finally we show the results obtained using the packaged VTRx module.

Modelling radiation-effects and annealing in semiconductor lasers for use in future particle physics experiments

Optical link components used in future particle physics experiments will typically be exposed to intense radiation fields during the lifetime of the experiment and the qualification of these components in terms of radiation tolerance is thus required. We have created a model that describes the degradation of the L-I characteristic of a semiconductor laser undergoing irradiation with the annealing processes taken into account. This model can be used to predict the behaviour of a laser being irradiated with the different particle fluxes at different locations inside a particle physics experiment. The robustness of the model has been checked against the experimental data obtained during high-fluence (in excess of 1015 particles/cm2) neutron and pion irradiation testing in 2009 and 2010.

FPGA-based bit-error-rate tester for SEU-hardened optical links

The next generation of optical links for future High-Energy Physics experiments will require components qualified for use in radiation-hard environments. To cope with radiation induced single-event upsets, the physical layer protocol will include Forward Error Correction (FEC). Bit-Error-Rate (BER) testing is a widely used method to characterize digital transmission systems. In order to measure the BER with and without the proposed FEC, simultaneously on several devices, a multi-channel BER tester has been developed. This paper describes the architecture of the tester, its implementation in a Xilinx Virtex-5 FPGA device and discusses the experimental results.

Modelling radiation-effects in semiconductor lasers for use in SLHC experiments

Optical link components in the SLHC inner detectors are to be exposed to intense radiation fields during operation, and, hence, their qualification in terms of radiation tolerance is required. We have created a model that describes a semiconductor laser undergoing irradiation to enable the extrapolation to full lifetime total fluences from lower fluence radiation tests. This model uses a rate-equation approach with modified gain calculation that takes thermal rollover into account. The model is used to fit experimental data obtained during high-fluence (in excess of 1015 particles/cm2) neutron and pion irradiation tests and evaluate its prediction capability.

An electroabsorption modulator-based network architecture for particle physics applications

The forthcoming increase in rate of data production and radiation levels, associated with the transition to High-Luminosity Large Hadron Collider, necessitates a readout link upgrade. Such upgrade is also an opportunity to move to a more efficient network infrastructure through the introduction of new technologies and it is in light of this that we explore the possibility of using a unified optical network architecture based on using Reflective Electroabsorption Modulators at the detector side. We evaluate the performance of the new architecture and investigate the way operating and environmental parameters such as wavelength and temperature affect it.

Characterization of Semiconductor Lasers for Radiation Hard High Speed Transceivers

In the context of the versatile link project, a set of semiconductor lasers were studied and modelled aiming at the optimization of the laser driver circuit. High frequency measurements of the laser diode devices in terms of reflected and transmission characteristics were made and used to support the development of a model that can be applied to study their input impedance characteristics and light modulation properties. Furthermore the interaction between the laser driver, interconnect network and the laser device itself can be studied using this model. Simulation results will be compared to measured data to validate the model and methodology.