Predicting the In-System Performance of the CMS Tracker Analog Readout Optical Links
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Transcript of Predicting the In-System Performance of the CMS Tracker Analog Readout Optical Links
Predicting the In-System Performance of Predicting the In-System Performance of the CMS Tracker Analog Readout Optical the CMS Tracker Analog Readout Optical
LinksLinks
Stefanos DrisStefanos Dris
CERN & Imperial College, CERN & Imperial College, LondonLondon
CERN & Imperial College Stefanos Dris 15/9/2004
IntroductionIntroduction• 10 million channels in the CMS
Tracker read out by ~40 000 analog optical links.
• Electronic, optoelectronic, and optical components making up the readout links will vary in gain.
• What spread in gain and dynamic range from link to link can we expect in the final system as a result?
• Will system specifications be met?
• We are now in a position to find out by simulation based on real production test data.
IntroductionIntroduction
The Tracker Optical Links
Simulation
Specifications
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
Analog Readout Optical Analog Readout Optical LinksLinks
Introduction
The Tracker The Tracker Optical LinksOptical Links
Simulation
Specifications
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
SimulationSimulationSimulation: LLD DataSimulation: LLD Data
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Transconductance (mS)
Gain Setting 0Gain Setting 1Gain Setting 2Gain Setting 3
LLD Transconductance
• LLD has four gain settings, allowing a certain amount of gain equalization of the optical links in the final system.
Introduction
The Tracker Optical Links
SimulationSimulation
SpecificationSpecificationss
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
SimulationSimulationSimulation: Laser Tx DataSimulation: Laser Tx Data
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Laser Transmitter Slope Efficiency
Introduction
The Tracker Optical Links
SimulationSimulation
SpecificationSpecificationss
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
SimulationSimulationSimulation: AOH DataSimulation: AOH DataIntroduction
The Tracker Optical Links
SimulationSimulation
SpecificationSpecificationss
Results
Conclusions
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Efficiency (mW/mV)
Gain Setting 0Gain Setting 1Gain Setting 2Gain Setting 3
AOH Efficiency
• Calculated AOH efficiency, using LLD and Laser Tx data
CERN & Imperial College Stefanos Dris 15/9/2004
SimulationSimulationSimulation: Patch PanelsSimulation: Patch Panels
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MU Connector Insertion Loss
Introduction
The Tracker Optical Links
SimulationSimulation
SpecificationSpecificationss
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
SimulationSimulationSimulation: Receiver DataSimulation: Receiver Data
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4540353025Responsivity (mA/mW)
ARx12 Responsivity
Introduction
The Tracker Optical Links
SimulationSimulation
SpecificationSpecificationss
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
SimulationSimulationSimulation: Load ResistorSimulation: Load Resistor
• Resistors used have 1% tolerance.• Assumed a 4σ Gaussian distribution.
• The load resistor offers another handle in tuning the gain of the optical link.
• The ARx12 contains a current mode amplifier that converts the optical power into an electrical current. This is changed into a voltage by the load resistor.
• The current value is 100, but is not frozen.
Introduction
The Tracker Optical Links
SimulationSimulation
SpecificationSpecificationss
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
Simulation: MethodSimulation: MethodSample PDF of each component
Multiply samples together to obtainoverall link gain for each LLD setting
Gain = LLD * Laser Tx * Connector Insertion Losses* ARx Responsivity * Load Resistor
Result: Four gains for each LLDsetting
Choose LLD setting whichresults to overall gain
closest to 0.8V/V
With LLDSwitching?
YES
Choose same LLD setting(0,1,2, or 3) every time.
NO
Repeat until 1 millionlink gains have been
produced
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Pro
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1.41.21.00.80.60.40.20.0Insertion Loss (dB)
MFS Connector (Distributed Patch Panel) Insertion Loss0.080.070.060.050.040.030.020.010.00
Pro
babi
lity
1.41.21.00.80.60.40.20.0Insertion Loss (dB)
MU Connector (In-Line Patch Panel) Insertion Loss
0.020
0.015
0.010
0.005
0.000
Pro
babi
lity
0.0500.0450.0400.0350.030Slope Efficiency (mW/mA)
Laser Transmitter Slope Efficiency
0.020
0.015
0.010
0.005
0.000
Pro
babi
lity
4540353025Responsivity (mA/mW)
ARx12 Responsivity
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Transconductance (mS)
Gain Setting 3
LLD Transconductance
Gain Setting 0
Gain Setting 1
Gain Setting 2
µ = 5.38mS
µ = 8.06mS
µ = 13.41mS
µ = 10.74mS • Use Inverse Transform Method to obtain random sample from each component PDF.
• Multiply each sample together to get overall optical link gain. 4 LLD settings 4 link gains.
• Choose one of the four link gains according to switching algorithm.
• Repeat 1 million times.
Introduction
The Tracker Optical Links
SimulationSimulation
SpecificationSpecificationss
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
SpecificationsSpecifications
Single-ended gain
Min Typical Max
0.25 0.8 2.5 V/VAt nominal LLD setting 1, no switching
0.3 0.8 1.3 V/V With LLD switching
• Target link gain = 0.8V/V• This corresponds to 80 ADC counts per 25 000 electrons from the
detectors.• Data is digitized, and there are 8bits of information for the signal. At the
target gain, 80 000 electrons can be transmitted with 8bits. • Assumption:
– For 320μm detectors, 1MIP = 25 000 electrons– For 500μm detectors, 1MIP = 39 000 electrons
• Therefore, for thin detectors, 3.2MIP signals can be transmitted without clipping using 8bits (2MIPs for thick detectors).
Introduction
The Tracker Optical Links
Simulation
SpecificationSpecificationss
Results
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults30000
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Introduction
The Tracker Optical Links
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ResultsResults
Conclusions
• ‘Single gain’ (no switching) distributions are roughly Gaussian.
• Gain 0 distribution tail exceeds 0.8V/V target. These links cannot be set to a lower setting.
• ‘Switching algorithm simply selects LLD gain setting which results in overall link gain closest to 0.8V/V.
• Switching is like cutting through ‘single gain’ distributions and selecting the slices centered on the target 0.8V/V.
CERN & Imperial College Stefanos Dris 15/9/2004
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ResultsResults
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LLD Gain Setting Gain 0: 65.46% Gain 1: 34.45%
Gain 2: 0.09%Gain 3: 0.00%
Gain Spread with Switching
Introduction
The Tracker Optical Links
Simulation
Specifications
ResultsResults
Conclusions
• ‘Single gain’ (no switching) distributions are roughly Gaussian.
• Gain 0 distribution tail exceeds 0.8V/V target. These links cannot be set to a lower setting.
• ‘Switching algorithm simply selects LLD gain setting which results in overall link gain closest to 0.8V/V.
• Switching is like cutting through ‘single gain’ distributions and selecting the slices centered on the target 0.8V/V.
• Possible to estimate ‘hard limits’ of the switched distribution by calculation.
• Average gain ~0.775V/V.• 99.9% of the links will have gains
from 0.64 to 0.96V/V.
CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
Dynamic Range• Analog data is digitized by 10-bit ADC, but 2 MSBs are discarded later.• Dynamic Range: Maximum signal size in electrons that can be transmitted
without clipping using 8bits.• Can translate this value into MIPs for both thin (320μm) and thick (500μm)
detectors.
Introduction
The Tracker Optical Links
Simulation
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ResultsResults
Conclusions
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Optical Link InputElectrons
CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
• Optical link output signal size in ADC bits, as a function of the input from the detectors in electrons.
• Solid line corresponds to the typical (target) gain value of 0.8V/V.
Introduction
The Tracker Optical Links
Simulation
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ResultsResults
Conclusions
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CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
• Optical link output signal size in ADC bits, as a function of the input from the detectors in electrons.
• Solid line corresponds to the typical (target) gain value of 0.8V/V.• 2 MSBs of the 10-bit ADC are discarded, therefore 8bits available to
accommodate the signals.
Introduction
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Simulation
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ResultsResults
Conclusions
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utpu
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CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
• Optical link output signal size in ADC bits, as a function of the input from the detectors in electrons.
• Solid line corresponds to the typical (target) gain value of 0.8V/V.• 2 MSBs of the 10-bit ADC are discarded, therefore 8bits available to accommodate the
signals.• At link gain = 0.8V/V, signals up to 80 000 electrons can be transmitted without clipping (80
000 e-/8bits).
Introduction
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Simulation
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ResultsResults
Conclusions
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CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
• Shaded area corresponds to minimum and maximum link gains determined by the simulation.
Introduction
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CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
• Shaded area corresponds to minimum and maximum link gains determined by the simulation.
• Minimum dynamic range = ~63 200 e-/8bits• Maximum dynamic range = ~100 500 e-/8bits
Introduction
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Simulation
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ResultsResults
Conclusions
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CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
• Shaded area corresponds to minimum and maximum link gains determined by the simulation.
• Minimum dynamic range = ~63 200 e-/8bits• Maximum dynamic range = ~100 500 e-/8bits• Knowing the distribution of the gain, we can calculate the distribution of the
dynamic range.• 99.9% of the links will have a dynamic range from ~66 500 to 100 000 e-/8bits.
Introduction
The Tracker Optical Links
Simulation
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ResultsResults
Conclusions
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Electrons
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CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
• For thin detectors (320μm), 1MIP=~25 000e-
• Hence at 0.8V/V gain, the system can transmit ~3.2MIPs/8bits without clipping.• 99.9% of the links will have a dynamic range from ~2.65 to 4 MIPs/8bits
Introduction
The Tracker Optical Links
Simulation
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ResultsResults
Conclusions
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6543210MIPs (320µm detectors)
Electrons
0
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V/V
0.80
V/V
0.64
V/V
CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
• For thick detectors (500μm), 1MIP=~39 000e-
• Hence at 0.8V/V gain, the system can transmit ~2.1 MIPs/8bits without clipping.• 99.9% of the links will have a dynamic range from ~1.7 to 2.6 MIPs/8bits
Introduction
The Tracker Optical Links
Simulation
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ResultsResults
Conclusions
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6543210MIPs (320µm detectors)
3210MIPs (500µm detectors)
Electrons
1.01
V/V
0.80
V/V
0.64
V/V
CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
Real System Data• 123 Tracker End Cap system optical links in test beam. • Relative agreement between simulation and real data.• ‘Single gain’ distributions of the real system are a few percent higher than
in simulation, with larger spread. This is most likely due to electronic components on either side of the optical link which were not simulated.
• Upper and lower limits of both switched distributions are almost identical – not surprising, given same switching algorithm is used and the dominant effect of gain settings 0 and 1 in both cases.
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LLD Gain SettingGain 0: 72.4%Gain 1: 21.1%Gain 2: 1.6%Gain 3: 4.9%
Test Beam Simulated
Introduction
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Simulation
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ResultsResults
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CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults
Previous Study• Uniform component distributions assumed.• Typical LLD gain setting was thought to be 1, now it is 0.• Larger range of gains than those predicted with real production data.
– Due to low-end tail of Gain 3 distribution.– Hence, low-gain links could not be compensated as well as high-gain links (the
opposite of the current situation).
• Ignoring the Gain 3 low-end tail, the extents of the spread are the same as in current simulation.
Introduction
The Tracker Optical Links
Simulation
Specifications
ResultsResults
Conclusions
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LLD Gain SettingGain 0: 11.00%Gain 1: 36.01%Gain 2: 30.18%Gain 3: 22.80%
CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults40000
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LLD Gain Setting Gain 0: 65.46% Gain 1: 34.45%
Gain 2: 0.09%Gain 3: 0.00%
Load Resistor• In addition to the
switchable LLD, there is a second handle on the gain of the full optical link.
• The Load Resistor value can still be changed to shift the ‘single gain’ distributions.
100Ω
Introduction
The Tracker Optical Links
Simulation
Specifications
ResultsResults
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResultsLoad Resistor
• In addition to the switchable LLD, there is a second handle on the gain of the full optical link.
• The Load Resistor value can still be changed to shift the ‘single gain’ distributions.
90.9Ω
Introduction
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Simulation
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ResultsResults
Conclusions
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LLD Gain Setting Gain 0: 33.87% Gain 1: 65.17%
Gain 2: 0.96%Gain 3: 0.00%
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CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResultsLoad Resistor
• In addition to the switchable LLD, there is a second handle on the gain of the full optical link.
• The Load Resistor value can still be changed to shift the ‘single gain’ distributions.
80.6Ω
Introduction
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Simulation
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ResultsResults
Conclusions
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LLD Gain SettingGain 0: 6.29%
Gain 1: 85.30%Gain 2: 8.38%Gain 3: 0.03%
CERN & Imperial College Stefanos Dris 15/9/2004
ResultsResults40000
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LLD Gain SettingGain 0: 1.16%
Gain 1: 77.50% Gain 2: 21.10%
Gain 3: 0.24%
Load Resistor• In addition to the
switchable LLD, there is a second handle on the gain of the full optical link.
• The Load Resistor value can still be changed to shift the ‘single gain’ distributions.
75Ω
Introduction
The Tracker Optical Links
Simulation
Specifications
ResultsResults
Conclusions
CERN & Imperial College Stefanos Dris 15/9/2004
ConclusionsConclusionsIntroduction
The Tracker Optical Links
Simulation
Specifications
Results
ConclusionsConclusions
• A model has been developed for the CMS Tracker analog optical link and used in a Monte Carlo simulation to assess the performance that can be expected in the final system.
• The specifications will be met for every one of the 40 000 links.
• The gains of the links will lie between 0.64 and 0.96V/V, i.e. 32% of the specified switched gain spread.
• The ‘single gain’ (non switched) distributions are slightly higher in mean than expected, due to higher gains in the laser transmitter and LLD, as well as low insertion loss of the connectors. This means the typical setting for the LLD is gain 0.
• The model can be used to demonstrate the effect of changing the values of readout components (e.g. the receiver’s load resistor). We could tailor the positions of the single-gain distributions to achieve a typical LLD setting of 1, or change the shape of the distribution to something more desirable.
• Different switching algorithms can be tested.• Components of the readout system (not part of the optical link) can be
added to achieve even more realistic results. Temperature effects on the AOH can also be included.
CERN & Imperial College Stefanos Dris 15/9/2004
ConclusionsConclusionsIntroduction
The Tracker Optical Links
Simulation
Specifications
Results
ConclusionsConclusions
• A model has been developed for the CMS Tracker analog optical link and used in a Monte Carlo simulation to assess the performance that can be expected in the final system.
• The specifications will be met for every one of the 40 000 links.• The gains of the links will lie between 0.64 and 0.96V/V, i.e.
32% of the specified switched gain spread. • The ‘single gain’ (non switched) distributions are slightly higher in
mean than expected, due to higher gains in the laser transmitter and LLD, as well as low insertion loss of the connectors. This means the typical setting for the LLD is gain 0.
• The model can be used to demonstrate the effect of changing the values of readout components (e.g. the receiver’s load resistor). We could tailor the positions of the single-gain distributions to achieve a typical LLD setting of 1, or change the shape of the distribution to something more desirable.
• Different switching algorithms can be tested.• Components of the readout system (not part of the optical link) can
be added to achieve even more realistic results. Temperature effects on the AOH can also be included.
CERN & Imperial College Stefanos Dris 15/9/2004
ConclusionsConclusionsIntroduction
The Tracker Optical Links
Simulation
Specifications
Results
ConclusionsConclusions
• A model has been developed for the CMS Tracker analog optical link and used in a Monte Carlo simulation to assess the performance that can be expected in the final system.
• The specifications will be met for every one of the 40 000 links.• The gains of the links will lie between 0.64 and 0.96V/V, i.e. 32% of
the specified switched gain spread. • The ‘single gain’ (non switched) distributions are slightly
higher in mean than expected, due to higher gains in the laser transmitter and LLD, as well as low insertion loss of the connectors. This means the typical setting for the LLD is gain 0.
• The model can be used to demonstrate the effect of changing the values of readout components (e.g. the receiver’s load resistor). We could tailor the positions of the single-gain distributions to achieve a typical LLD setting of 1, or change the shape of the distribution to something more desirable.
• Different switching algorithms can be tested.• Components of the readout system (not part of the optical link) can be
added to achieve even more realistic results. Temperature effects on the AOH can also be included.
CERN & Imperial College Stefanos Dris 15/9/2004
ConclusionsConclusionsIntroduction
The Tracker Optical Links
Simulation
Specifications
Results
ConclusionsConclusions
• A model has been developed for the CMS Tracker analog optical link and used in a Monte Carlo simulation to assess the performance that can be expected in the final system.
• The specifications will be met for every one of the 40 000 links.• The gains of the links will lie between 0.64 and 0.96V/V, i.e. 32% of
the specified switched gain spread. • The ‘single gain’ (non switched) distributions are slightly higher in
mean than expected, due to higher gains in the laser transmitter and LLD, as well as low insertion loss of the connectors. This means the typical setting for the LLD is gain 0.
• The model can be used to demonstrate the effect of changing the values of readout components (e.g. the receiver’s load resistor). We could tailor the positions of the single-gain distributions to achieve a typical LLD setting of 1, or change the shape of the distribution to something more desirable.
• Different switching algorithms can be tested.• Components of the readout system (not part of the optical link) can
be added to achieve even more realistic results. Temperature effects on the AOH can also be included.
CERN & Imperial College Stefanos Dris 15/9/2004
ConclusionsConclusionsIntroduction
The Tracker Optical Links
Simulation
Specifications
Results
ConclusionsConclusions
• A model has been developed for the CMS Tracker analog optical link and used in a Monte Carlo simulation to assess the performance that can be expected in the final system.
• The specifications will be met for every one of the 40 000 links.• The gains of the links will lie between 0.64 and 0.96V/V, i.e. 32% of
the specified switched gain spread. • The ‘single gain’ (non switched) distributions are slightly higher in
mean than expected, due to higher gains in the laser transmitter and LLD, as well as low insertion loss of the connectors. This means the typical setting for the LLD is gain 0.
• The model can be used to demonstrate the effect of changing the values of readout components (e.g. the receiver’s load resistor). We could tailor the positions of the single-gain distributions to achieve a typical LLD setting of 1, or change the shape of the distribution to something more desirable.
• Different switching algorithms can be tested.• Components of the readout system (not part of the optical
link) can be added to achieve even more realistic results. Temperature effects on the AOH can also be included.