optical links cern versatile link project vl – oxford involvement cern vl+ for atlas/cms phase ii...
TRANSCRIPT
Oxford review Jan 15 1
Optical Links
• CERN Versatile Link Project VL– Oxford involvement
• CERN VL+ for ATLAS/CMS phase II upgrade– Introduction and aims– Oxford workpackage: reliability
Tony Weidberg
Oxford review Jan 15 2
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 Weidberg
Oxford review Jan 15 3
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 Weidberg
Oxford review Jan 15 4
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 Weidberg
Oxford review Jan 15 5
Radiation Source
• 60Co g 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 : 0.0265 to 22.5
kGy(Si)/hourTony Weidberg
Oxford review Jan 15 6
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 Weidberg
Oxford review Jan 15 7
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 Weidberg
4 channels 2*12*12 mm
Oxford review Jan 15 8
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 Weidberg
Oxford review Jan 15 9
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 Weidberg
Oxford review Jan 15 10
Transceiver Tests
• Monitor link performance while operating at elevated temperatures.
• Look for evidence of degradation using– Eye diagrams– BER scans
Tony Weidberg
Oxford review Jan 15 11
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 Weidberg
Oxford review Jan 15 12
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 Weidberg
Oxford review Jan 15 13
BER System
Tony Weidberg
FPGAVTRx
Optical attenuator
Power MeterVTRx
Optical Switches
Loopback testsOptical switches allow many VTRx to be tested in an environmental chamber.
Oxford review Jan 15 14
BER Scans• Measure BER vs OMA
(optical modulation amplitude).
• Define minimum OMA to achieve BER = 10-12.
• Measure this during continuous operation at elevated temperature.
• Curves show example BER scans with and w/o beam.
Tony Weidberg
Oxford review Jan 15 15
Backup
Tony Weidberg
Oxford review Jan 15 16
JDSU Mainframe
Tony Weidberg
Oxford review Jan 15 17
JDSU Power Meter
Tony Weidberg
Oxford review Jan 15 18
JDSU Optical Attenuator
Tony Weidberg
Oxford review Jan 15 19
Polatis Optical Switch
• Multiway optical switch (from UCL)
Tony Weidberg