Lauri Olantera

The Versatile Transceiver: towards production readiness

Detectors involved in the upgrade programme of the LHC will need high-speed optical links to transfer readout and control data. The link front-end will be based on a radiation tolerant opto-electronic module, the Versatile Transceiver (VTRx), developed under the Versatile Link project. In this contribution we present a test system and protocol to be used to verify the compliance of the VTRx modules to the specifications, and a Versatile Link demonstrator based on the VTRx and the Gigabit Link Interface Board. Finally, we introduce the Small Footprint VTRx which is being designed for the CMS Tracker upgrade.

Modeling TID Effects in Mach-Zehnder Interferometer Silicon Modulator for HL-LHC Data Transmission Applications

High-speed Mach-Zehnder interferometer silicon modulators were exposed to a total ionizing dose of 1.3 MGy, levels comparable to the worst radiation levels for a tracking detector after 10 years of operation at the High-Luminosity LHC, show a sensitivity to ionizing radiation after exposure to a dose of a few hundred kGy. A physical model to describe the effect of ionizing radiation on the modulators has been developed and is used to predict whether a more radiation-hard modulator can be designed to survive the harshest radiation environments expected at the HL-LHC.

Gamma irradiation of minimal latency Hollow-Core Photonic Bandgap Fibres

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 1550nm 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 hour exposure to gamma-rays, resulting in a radiation-induced attenuation of only 2.1dB/km at an accumulated dose of 940kGy.

Laser and photodiode environmental evaluation for the Versatile Link project

We summarize the results obtained in a series of radiation tests of candidate laser and photodiode components for use in the Versatile Transceiver (VTRx), the front-end component of the Versatile Link. We have carried out radiation testing at a full spectrum of sources (neutrons, pions, gammas) and can now compare the results and show that the range of components that meet the radiation tolerance requirements is rather large. In addition, devices have been operated in a high magnetic field to qualify them for use in (HL-) LHC detectors.

Neutron and X-ray irradiation of silicon based Mach-Zehnder modulators

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 1.2×1015 n cm−2 and 1.3 MGy respectively.

Temperature characterization of versatile transceivers

The Versatile Transceiver is a part of the Versatile Link project, which is developing optical link architectures and components for future HL-LHC experiments. While having considerable size and weight constraints, Versatile Transceivers must work under severe environmental conditions. One such environmental parameter is the temperature: the operating temperature range is specified to be from -30 to +60?C. In this contribution we present the results of the temperature characterization of the VTRx transmitter and receiver. Several transmitter candidates from three different manufacturers have been characterized: multi-mode Vertical Cavity Surface-Emitting Lasers and a single-mode Edge-Emitter Laser. Also both single- and multi-mode receivers have been tested.

Versatile transceiver and transmitter production status

Production of the Versatile transceiver and twin transmitter modules for use in the readout and control systems of upgrading LHC detector systems is starting. We review the performance of the prototypes produced so far and show that the modules are ready for production. We outline the commercial actions being taken to procure parts and assemblies and show the production plan for delivering known good parts in the various flavours required for the upgrade projects that will be using them.

High Dose Gamma Irradiation of Lasers and p-i-n Photodiodes for HL-LHC Data Transmission Applications

Lasers and photodiodes for high luminosity large Hadron collider (HL-LHC) data transmission applications were irradiated with a 1-Gy dose of 60Co gammas. No change was observed in the performance of the lasers tested, and an order of magnitude increase in the leakage current of the InGaAs photodiodes was measured.

A system-level model for high-speed, radiation-hard optical links in HEP experiments based on silicon Mach-Zehnder modulators

Silicon Mach-Zehnder modulators have been shown to be relatively insensitive to displacement damage beyond a 1-MeV-equivalent neutron fluence of 3⋅1016n/cm2. Recent investigations on optimized device designs have also led to a high resistance against total ionizing dose levels of above 1 MGy. Such devices could potentially replace electrical and/or optical links close to the particle interaction points in future high energy physics experiments. Since they require an external continuous-wave light source, radiation-hard optical links based on silicon Mach-Zehnder modulators need to have a different system design when compared to existing directly modulated laser-based optical links. 10 Gb/s eye diagrams of irradiated Mach-Zehnder modulators were measured. The outcomes demonstrate the suitability for using these components in harsh radiation environments. A proposal for the implementation of silicon Mach-Zehnder modulators in CERNs particle detectors was developed and a model to calculate the system performance is presented. The optical power budget and the electrical power dissipation of the proposed link is compared to that of the upcoming Versatile Link system that will be installed in 2018.

System-level testing of the Versatile Link components

During the first upgrade phase of the Large Hadron Collider experiments, high-speed optical links will be deployed to achieve the bandwidth needed to exploit the increasing luminosity and to allow data acquisition at higher rates. The Versatile Transceiver (VTRx) and Versatile Twin Transmitter (VTTx) modules are in their final development phase before production. They support different link architectures and offer compatibility with either single-mode or multi-mode fibre plants. This paper describes the supported link configurations and presents the system-level testing of the VTRx and VTTx front-end modules with various commercial-off-the-shelf back-end components.