Development of radiation-hard optical links for the CMS tracker at CERN

Abstract

A radiation-hard optical link is under development for readout and control of the tracking detector in the future CMS experiment at the CERN Large Hadron Collider.We present the optical system architecture based on edgeemitting InGaAsP laser-diode transmitters operating at a wavelength of 1.3pm, single mode fiber ribbons, multi-way connectors and InGaAs Pin photodiode receivers.We report on radiation hardness tests of lasers, photodiodes, fibers and connectors. Increases of laser threshold and pin leakage currents with hadron fluence have been observed together with decreases in laser slope-efficiency and photodiode responsivity. Short lengths of single-mode optical fiber and multi-way connectors have been found to be little affected by radiation damage.We analyze the analog and digital performance of prototype optical links transmitting data generated at a 40MSamples/s rate. Distortion, settling time, bandwidth, noise, dynamic range and bit-error-rate results are discussed.

Radiation damage and annealing in 1310-nm InGaAsP/InP lasers for the CMS tracker

“…A system of 50000 analogue optical links, using InGaAsP/InP lasers operating at 1310nm, will be used to transfer data signals from more than 10 million microstrip detector channels in the tracker system of the Compact Muon Solenoid (CMS) experiment [1][2][3]. This experiment is currently under construction and will operate at the Large Hadron Collider (LHC), a 7+7 TeV proton-proton collider also being built at CERN.…”

<title>Wavelength-based analog-to-digital conversion</title>

“…[23] The individual photonic components comprising the ADC have been individually shown to be rather resistant to a wide range of radiation environments. These path trimmers may be as simple as standard single mode optical fiber with lengths on the order of centimeters.…”

Ageing tests of radiation damaged lasers and photodiodes for the CMS experiment at CERN

“…few thousand hours) , therefore extrapolation to some failure criteria is normally used to determine the MTTF, which is then scaled to the required working temperature using equation (1). Unfortunately there was no available activation energy data, for wearout or random failure, for the lasers tested here, and it was not possible to conduct ageing tests at different temperatures since we had a limited number of samples.…”

“…The optical links will be based on 1310nm InGaAsP edge-emitting lasers and InGaAs p-i-n photodiodes, coupled via standard telecom single-mode fiber with several connectorized break-points [1]. The analogue links will run at 40Msample/s and the digital links will run at 40MHz.…”

“…A system of 50000 analogue and several thousand digital optical links is being developed at CERN for readout and control of the CMS Tracker [1,2]. The optoelectronic devices inside the tracker will be exposed to a harsh radiation environment over the lifetime of at least 10 years.…”