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Transcript
Options for Optical Links at SLHC
Francois Vasey, CERN/PH-MIC
with input from ATLAS and CMS colleagues





Margins of existing ATLAS and CMS TK OL
Options for OL upgrades
Some proposals
The joint optoelectronics working group
Conclusion
28-Sep-06
[email protected]
0
Optical Links for the ATLAS and CMS Trackers
ATLAS
Digital links
(40/80Mb/s)
CMS
Analogue readout links
(40MS/s, 8bits)
Digital control links
(80 Mb/s)
17.5k
Channels
40k+ 3k
Channels
VCSEL
850nm
MM
EELaser
1310nm
SM
28-Sep-06
[email protected]
1
The Optical Link Margins (1: Tx)
Tx Radiation Hardness


Operating point shifts
Thermal management
becomes crucial



Thermal resistance
Annealing
Compliance voltage
BEFORE annealing
Optical Output Power [W]

1000
100
10
1
0.1
0.01
0
20
40
60
80
100
120
140
80
1.0
60
0.8
Ith
Eff of LD1
40
0.4
20
0.2
LHC 1.0
2.0
3.0
4.0
Fluence [10 n/cm ] 20MeV
15
28-Sep-06
[email protected]
0.6
2
2
Relative Efficiency [W/mA]
Preliminary
Threshold Ith [mA]
Input Current [mA]
The Optical Link Margins (2: Rx total)
Rx Radiation Hardness



Leakage current damage
definitely appears to be
‘saturating’
Responsivity going to zero
No significant annealing
Ultimate limit reached
10
10
10
10
10
10
10
-3
leakage current (A)

leakage current (A)

-4
-5
-6
-7
10
10
10
10
-9
10
1
154
2
1.0
photocurrent at 100uW (uA)
0.6
0.4
0.2
LHC
1
-5
-6
-7
-8
-9
0.8
0.6
0.4
0.2
0.0
0.1
10
154
2
1
10
annealing time (hrs)
fluence (10 n/cm )
[email protected]
-4
1.0
0.8
0.0
0.1
-3
0.1 1 10
annealing time (hrs)
10
fluence (10 n/cm )
photocurrent at 100uW (uA)
10
-8
0.1
28-Sep-06
10
3
Optical Link Margins (3: Rx SEE)

Rx SEE cross-section


Bit rate dependent
Incidence-angle dependent
28-Sep-06
[email protected]
4
Optical Link Margins (4: fiber)

Fiber Radiation Hardness


(0.05-0.1dB/m)
To be reconfirmed
28-Sep-06
[email protected]
5
Optical Link Margins (5: link)

Fiber Capacity




CMS SISM: >>10GHz∙km
Electronics


ATLAS SIMM: 50-80 MHz∙km
ATLAS GRIN: 1000 MHz∙km
Binary 40/80MBps

Analogue 100MHz
Digital 80MBps

20cm from beam axis

Geometry

18cm from beam axis
28-Sep-06
[email protected]
6
Margins for operation at SLHC (6: summary)

Tx and Rx need careful study



Fiber



Generalized Bottleneck
Geometry


Radiation tolerance probably OK
Capacity increase OK in SM, NOT OK in SIMM, OK in GRIN
Electronics


Are we reaching the limit?
Rx SEE sensitivity to be mitigated
Possibility to move away from beam axis to gain margin against
radiation damage
Good overall agreement between ATLAS and CMS
observations
28-Sep-06
[email protected]
7
The Options for an Upgrade (1)

Reuse the existing system


Check margins carefully
Boost analog link capacity by
developing CODEC and MODEM


Develop TRx, SERDES and
CODEC


See paper by P. Moreira
Check compatibility and margins
of legacy fiber and connectors
?
Start from scratch


See paper by S. Dris
Reuse the fiber plant only


Cod
Ser
Tx
Cod/Mod
Possibly using components
identical to existing ones
A combination of the above

Rx
Des
Dec
Dec/Demod
Geometry dependent system
implementation
28-Sep-06
[email protected]
8
Novelty
The Options for an Upgrade (2)

Start from scratch

Reuse the fiber plant only

Reuse the existing system
components
development
Resources
28-Sep-06
[email protected]
9
Proposal 1: The ATLAS SCT Straw-Link

(T. Weidberg, Oxford, Oct 05)



2500 links
2.5Gbps
Start from scratch
TTC
FanOut
M1
M2
M30
Clock
Data
MUX
28-Sep-06
PDA
PDA
LD
[email protected]
10
Proposal 2: ATLAS Pixels


K.K. Gan, Ohio State University
Reuse existing cable plant

1m micro twisted pair, 8m SIMM fiber, 70m GRIN fiber, 1Gbps
1m40 TP
2Gbps 9m SIMM + 20m GRIN
0.65Gbps
1.3 Gbps
28-Sep-06
[email protected]
11
Proposal 3: The versatile bi-directional
digital link
GBT Chipset

Opto 1
S. Marchioro, P. Moreira, CERN, 2005


Opto 2
3-6Gbps
Versatile
Opto
Startbidi
from
or 3reuse fiber plant
TRx scratch
28-Sep-06
[email protected]
12
Proposal 4: Flipped OE devices on SoS substrate


Ping Gui, Jingbo Ye, SMU, 2005
Start from scratch or reuse fiber plant
UTSi
integrated
photo
detector
UTSi integrated circuitry
receiver circuitry
VCSEL driver circuitry
quad VCSEL array
flip chip
attachment
quad PIN array
200 um
transparent
sapphire
substrate
(UTSi)
MMF ribbon fiber
28-Sep-06
[email protected]
13
active
CMOS
layer
The Joint Optoelectronics Working Group
System
FE
28-Sep-06
TRx1
Optical Link 1
TRx1
Rx2
Optical Link 2
Tx2
Tx3
Optical Link 3
Rx3
[email protected]
BE
14
Joint
Optoelectronics
Working Group
Joint Optoelectronics
Working Group
ResourcesSurvey
Distribution
Result



5
Series1
CERN
Ljubljana
Minnesota
Ohio
Oklahoma
Oxford
Polytechnique
RAL
SMU
Strasbourg
8
7
6
5
FTE 4
3
2
1
0
11.4
13 institutes, 23FTE
2 development projects (SMU, CERN)
Collaborative proposals in preparation
28-Sep-06
CERN
[email protected]
EU
US
6.6
10.2
ATLAS
12.8
15
CMS
Conclusions

Options for Optical Links at SLHC are:




Reuse existing system (open to CMS only)
Reuse fiber plant only (open to CMS and ATLAS Pixels)
Start from scratch (possibly using components identical to existing ones).
Check margins of existing components thoroughly

Investigate Laser and PIN diodes in depth




Will we reach the total dose limit at SLHC?
Draw a line of usability at SLHC, with safety margin.
Investigate electronic mitigation techniques (total dose and SEE).
For new components, concentrate on only very few options.



Generic and versatile
The joint optoelectronics working group has the potential to coordinate a
few parallel projects across experiments.
System level aspects to be addressed by the experiments.
28-Sep-06
[email protected]
16