Optical Links CERN Versatile Link Project VL – Oxford involvement CERN VL+ for ATLAS/CMS phase II upgrade – Introduction and aims – Oxford workpackage: reliability Tony WeidbergOxford review Jan 151

Versatile Link Optical links for data read out from detector and Timing, Trigger and Control data needed by the detector. Generic system for LHC detector upgrades Tony WeidbergOxford review Jan 152

Versatile Link Need radiation-tolerant optoelectronics for on-detector components. – Select VCSELs and p-i-n diodes from radiation studies. – Want very reliable and low mas/non-magnetic package. – Commercial optical transceivers can’t be used – Need radiation-tolerant ASICs. – Too much material, magnetic and use ferrite cores as inductors in laser drivers. Keep optical sub-assembly and commercial connectors for reliability but use plastic package. Tony WeidbergOxford review Jan 153

Oxford Involvement Todd, Tony, graduate students + workshops. Radiation testing of passive optical components – Fibres Radiation Induced Attenuation (RIA) Fibre bandwidth Mechanical reliability – Fibre cables – Connectors – Couplers Suitable components qualified for HL-LHC doses. Tony WeidbergOxford review Jan 154

Radiation Source 60 Co  sources at RITA (SCK SEN) Belgium &BNL. Annealing of damage can be very important – Temperature and dose rate important At HL-LHC Si detectors will operate ~ -25C – Warm and cold measurements of fibres Dose rates : to 22.5 kGy(Si)/hour Tony WeidbergOxford review Jan 155

VL+ Increase speed for data links to 9.6 Gbits/s. – New lpGBTx in 65 nm technology – New lower mass/smaller size transceivers. VCSELs not inside hermetic TO can  reliability testing critical  Oxford responsibility (already have experience from ATLAS SCT). Tony WeidbergOxford review Jan 156

VL+ Transceivers Very dense packaging being developed Customise commercial parts – Specify VCSEELs and p-i-n diodes – Supply rad-hard LDD and TIA Develop module – Bare die – Commercial optical interface blocks Tony WeidbergOxford review Jan channels 2*12*12 mm

Optical Links Reliability Tests “If you think safety is expensive, try having an accident” Plenty of painful experience in ATLAS  must perform rigorous testing before production. VCSEL tests – VCSELs used in current VTRx – New VCSELs for VL+ Transceiver tests – Current VL package: VTRx – New packages for VL+, e.g. LightPeak. Tony WeidbergOxford review Jan 158

VCSEL Tests Standard damp heat tests – 1000 hours, 85C/85% RH. – Drive current 10 mA dc – Measure optical power continuously. – Aim for much higher statistics than we have done in the past  learn about infant mortality and random failure rates as well as lifetime. – So far we have tested 2 VCSELs, would like to do 200 devices? Tony WeidbergOxford review Jan 159

Transceiver Tests Monitor link performance while operating at elevated temperatures. Look for evidence of degradation using – Eye diagrams – BER scans Tony WeidbergOxford review Jan 1510

Eye Diagrams Use Digital Communication Analyser to measure eye diagrams – DCA firmware upgraded to allow testing at a bit rate of 4.8 Gbits/s. – Determine many parameters, e.g. horizontal and vertical eye opening, rise and fall times, noise, random and deterministic jitter. Tony WeidbergOxford review Jan 1511

Equipment for BER Scan FPGA – Generates PSRB data – Measures BER Loopback test, e.g. transceiver VTRx to receiver VTRx. Computer controlled optical attenuator to allow scan of BER vs OMA. Has a 10% and 90% tap to allow for power measurement during BER scan. Optical switch to allow many channels to be measured. We have a copy of CERN VL system so we can use their firmware and software (almost) Tony WeidbergOxford review Jan 1512

BER System Tony WeidbergOxford review Jan 1513 FPGA VTRx Optical attenuator Power Meter VTRx Optical Switches Loopback tests Optical switches allow many VTRx to be tested in an environmental chamber.

BER Scans Measure BER vs OMA (optical modulation amplitude). Define minimum OMA to achieve BER = Measure this during continuous operation at elevated temperature. Curves show example BER scans with and w/o beam. Tony WeidbergOxford review Jan 1514

Backup Tony WeidbergOxford review Jan 1515

JDSU Mainframe Tony WeidbergOxford review Jan 1516

JDSU Power Meter Tony WeidbergOxford review Jan 1517

JDSU Optical Attenuator Tony WeidbergOxford review Jan 1518

Polatis Optical Switch Multiway optical switch (from UCL) Tony WeidbergOxford review Jan 1519