SLHC Optoelectronics

Tony Weidberg ATLAS Tracker Upgrade Liverpool December '06

1

SLHC Optoelectronics

• Readout architectures

• Technologies for TX

• High speed multiplexing

• Packaging

• Radiation hardness and reliability testing


2

Architecture (1) Low speed links• Like current SCT: 2 data links/module (redundancy)


3

Architecture (2) High Speed Links

• High speed MUX at end of supermodule.

Data Concentrator 1

Data Concentrator 8

MUX LD

Modules


4

Architecture for Pixels

• MCC reads out n pixel chips. For SLHC, pixel chip size similar occupancies x10 data transmission rates x10.

• Pixels need 1-2 Gbits/s.

• Question: can we have a common architecture for pixels and strips?


5

Cost Estimates (1)

• Assume Strawman layout for strips– 21824 modules barrel 11968 modules disks

• Low speed links: scale based on actual costs of SCT links + input from S-C Lee on commercial costs for opto-packages.

• Total for strips = 32.7 MCHF (components only).


6

Costs (2)• High speed links• Multiplex 30 modules one fibre. Data rate

~3 GBits/s.• Scale costs from actual costs of LHCb GOL/VCSEL

readout at 1.6 GBits/s. Larger uncertainties here. No redundancy in this calculation.

• Estimated total cost for strips ~ 2 MCHF.• This estimate is approximate but conclusion High

speed links costs << low speed links. Francois Vasey “you have to fill the bandwidth of the fibre to be cost effective”.

• Note a mixed solution with low speed fibres along supermodule and multiplexing to high speed links at the end of a stave would also be very expensive (only ~ 30% of the cost is for fibre).


7

Advantages Low Speed Links

• Grounding: separate ground for each module but – have to join grounds for serial powering– ATLAS SCT had common grounds for

larger number of modules (40 or 52) in End caps with no significant change in noise (TTC Redundancy interlinks s/c DGND).

– For barrel SCT had 100 redundancy links between DGND for neighboring modules in loop of 12 modules. No increase in noise seen.


8

Disadvantages Low Speed Links• Cost much higher!• Packaging more difficult (space constraints more

severe)• Single source for rad-hard SIMM fibre; might not be

available for SLHC.• Fragile fibres on detector are not good (had many fibre

breakages, some not repairable).• After mounting on detector, failures could not be

replaced ( failures 4 or 5 years before start of operation were not recoverable).

• Mounting is very difficult, time consuming labour costs high.

• Needs new chip set and we have nobody to work on it• Nobody interested in links to work on this option.


9

Low vs High Speed Links

• Low speed versus high speed affects everything in system:– Fibres, transmitters, packaging affects

supermodule engineering.– We won’t make much progress until we make a

decision.

• My suggestion: – Adopt high speed links as baseline.– Low speed links as fall back if we can’t solve

noise problems for modules.


10

Technologies

• VCSELs @ 850 nm (ATLAS) + SIMM/GRIN fibre.

• EELs @ 1310 nm (CMS) + SM fibre.

• VCSELs @ 1310 nm (new) + SM fibre.


11

VCSELs @ 850 nm (1)

• Advantages:– Very radiation hard, very small threshold shifts at

SLHC fluences ( next transparencies)– Easy to couple into MM fibres.

• Disadvantages– Needs custom packaging a la SCT/Pixel.– Bandwidth of SIMM fibre too low and GRIN fibre

not radiation hard enough mixed SIMM/GRIN fibre.

– Needs custom fibres concerns on cost and availability.


12

Radiation Hardness VCSELs

• See talk by Issever at LECC 2006 http://indico.cern.ch/contributionDisplay.py?contribId=47&sessionId=12&confId=574

• No significant change in slope efficiencies up to SLHC fluence

• Small threshold shifts transparency• But some channels became sick after

annealing @ 15 mA. Not understood needs further studies…


13

Results – Threshold Shift (After-Before)

0

0.5

1

1.5

2

2.5

3

0 1 2 3 4 5 6 7 8 9 10

Fluence 10^15 [n(1 MeV)/cm2]

T

hre

sho

ld [

mA

]Δ

Th

resh

old

[m

A]

5 years SLHC @ 10^35 cm-2 sec-1 with a safety factor of 2

1.0E+14

1.0E+15

1.0E+16

1.0E+17

1.0E+18

0 20 40 60

Radius [cm]

1 M

eV

neu

tro

n F

luen

ce

[n/c

m^

2]

Si

GaAs

10 days @ 10mA annealed and 5 days @ 15mA annealed

LHC, annealed @ 20mA, proton implant


14

VCSELs @ 850 nm (2)• Fibre Bandwidth

– Very radiation hard SIMM fibre has low bandwidth > ~50 MHz km

– Radiation tolerant GRIN fibre has higher bandwidth 1121 MHz km.

– Splice 8m of SIMM fibre to ~ 80m GRIN fibre (as done for current Pixel readout).

– Could operate up to ~ 5 Gbits/s.• Demonstration of Bandwidth

– Tests by KK Gan (OSU) See talk at LECC 2006 http://indico.cern.ch/contributionDisplay.py?contribId=48&sessionId=12&confId=574

– Scope photos of eye diagrams at 2 Gbits/s transparency


15


16

EELs

• Advantages– Couple to SM fibre at 1310 nm choice of

commercial fibres that are sufficiently radiation hard and very high bandwidth.

– Can survive SLHC fluences.

• Disadvantages– Higher thresholds than VCSELs and larger

threshold shifts with radiation.– More difficult to couple to fibre but can be done

by telecoms companies (as for current CMS).


17

Radiation damage EELs• Threshold shift for

SLHC worst case 2 1015 cm2 is ~105 mA.

• 70% of damage will be annealed during operation

• Threshold before irradiation ~ 4 mA. after full SLHC fluence threshold ~ 36 mA (high!).

K. Gill, SPIE 2002.

http://cms-tk-opto.web.cern.ch/cms%2Dtk%2Dopto/tk/publications/wdocs/kg_spie2002.pdf

300 MeV/c




18

VCSELs @ 1310

• Advantages– Best of both worlds. High bandwidth, availability

of several sources of commercial radiation hard fibre. VCSELs @ 1310 nm expected to be very radiation hard.

• Disadvantages– New technology concern about availability.– Need to verify radiation hardness and reliability.

Major effort in conjunction with CMS.


19

High Speed Multiplexing

• Current technology: GOL on 0.25 m CMOS. Operates at 1.6 GBits/s . Radiation hard.

• Should be possible to go faster with 0.13 or 0.09 m.

• CERN project aims to develop MUX ASIC.

• SMU also developing MUX as part of LOC.


20

CERN VBDL Proposal

• Versatile bi-directional links for ATLAS & CMS – Use for data, TTC and experimental

control.– Following transparencies from P. Morerira,

LECC 2006 talk http://indico.cern.ch/contributionDisplay.py?contribId=128&sessionId=22&confId=574

21

Transceiver Module

O/E

E/O

GBT

DAQTimingTriggerExperiment Control

Common definition

MCM containing the ASIC, optoelectronic components and optical and electrical connectors.

Multi-protocol ASICQualified optoelectronic components(COTS)

Configurable to multiple optical networks (user driven)

22

Limiting Amplifier

Specifications:• Data rate: 3.60 Gbit/s• Gain: > 55 dB• Bandwidth > 2.52 GHz• Equivalent input noise: < 1 mV• Minimum input signal (differential): 10 mV• Maximum input signal (differential): 600 mV

Specifications:• Data rate: 3.60 Gbit/s• Gain: > 55 dB• Bandwidth > 2.52 GHz• Equivalent input noise: < 1 mV• Minimum input signal (differential): 10 mV• Maximum input signal (differential): 600 mV

23

Limiting AmplifierOffset

CancellationBias Gain

CellGainCell

GainCell

GainCell

Output Buffer

Size: 194 m × 194 m

24

Limiting Amplifier

3.35 Gbit/s3.35 Gbit/s 1 Gbit/s1 Gbit/s

25

CERN VBDL Summary (1)• Versatile Link solution for:

– Timing Trigger Links;– Data Acquisition Links;– Experiment Control Links.

• The system allows flexible link topologies:– Bi-directional– Uni-directional– Point-to-Point– Point-to-Multipoint

26

CERN VBDL Summary (2)

• Specifications and Interfaces are still evolving for which we need the feedback of the potential users

• Some universal building blocks have already been prototyped:– Laser driver– Encoder/decoder: Line code and FEC– Limiting amplifier

• The Versatile Bi-Directional Link project has been proposed by the Microelectronics group as a CERN common development.


27

LOC

• LOC being developed by SMU for LAr @ SLHC

• Integrate electronics and laser/PIN on chip using SOS technology see talk by Jingbo Ye at this workshop.

28

Link-on-Chip Architecture

Optical data

• Improve performance– No off-chip high speed lines– Flip-chip bonding reduces capacitance and inductance

• Reduce power consumption– No 50-Ohm transmission lines between chips

• Designed and Implemented in Silicon-on-Sapphire technology• Targeting speed:>2.5Gbps

LaserLaserDriverserializer

encoder

Flip-chipbonding

TXParallelData

REFclock

transmitter Module

Photonic

PIN

Receiver Module

TIA/LADe-

serializerDecoder

Parallel Data

Clock/Data recovery

Flip-chipbonding

REFclock

PLL and clock generator


29

Flipped OE devices on SoS substrate

transparent sapphire substrate(UTSi)

active CMOS layer

quad PIN array

flip chip attachment

quad VCSEL array

UTSi integrated photo detector

MMF ribbon fiber

VCSEL driver circuitry receiver circuitry

UTSi integrated circuitry

200 um

• Flip-chip bonding of OE devices to CMOS on sapphire– No wire-bonds – package performance scales to higher data rates

– Rugged and compact package


30

Transceiver IC with OE Devices and Link Performance

at 2.0GbpsTransceiver link eye at 3.2Gbps


31

Packaging

• Non trivial because must be radiation hard, non-magnetic, low mass, low Z material and fit in available space

• Full custom packaging. Eg SCT opto-package or Pixel MT coupled arrays

• Find Telecoms company package that is compatible with our requirements (CMS)


32

Custom Packaging - SCT


33

12 way array with MT guide pins for coupling to 12 way ribbon fibre

Used for Pixel on-detector and SCT/Pixel off-detector BOC


34

Telecoms Packaging

• CMS Analogue Opto Hybrid (AOH)

• 3 channels laser drivers, lasers and fibres

35

CMS Laser Sub-Mount• Compact: 4.5 * 4 * 1.3 mm3

• Fibre ends gold plated• Active alignment: resistor pads used to solder fibre

in location. Glue only for strain relief of fibre• Radiation hard by design

Removed for CMS (save $)


36

Pixel Links

• Consider option to keep similar architecture

• Number of links would be similar to current Pixel system and increase in luminosity 10 times higher data rate Need ~ 1 Gbit/s

• Develop similar architecture chips to current DORIC and VDC in 0.13 m

• See talk by K.K. Gan at this workshop


37

Common ATLAS/CMS WGs• Theme a- Lessons learned and to be learned.

– Collect info on successes and mistakes of the groups involved in the present detectors. Follow up on the technology choices made over 10 years ago. Produce a transparent account of the costs incurred. Create a repository for all publications. Monitor and follow up the performance and ageing of the installed links.

• Theme b- Radiation hardness and reliability of optoelectronic components. – Establish common procedures and common ways to represent

the irradiation data, share facilities and coordinate irradiation runs, avoid redundant tests and share results.

• Theme c- Common optical link reference test bench. – Define a reference test system for multi-gigabit/s optical links.

Define test procedures and evaluation criteria. Specify the interface to the links to be tested. Develop hard, software and FPGA-IP blocks. Purchase test equipment and build reference test bench. Test proposed SLHC links on common reference bench and evaluate with common criteria.


38

Outlook

• Much more work to do on radiation hardness:– Understand 850 nm VCSEL performance better– Compare damage factors in /p/n tests.– Start testing 1310 nm VCSELs.– Continue fibre testing to SLHC doses– Test Si and InGaAsP p-i-n diodes to SLHC fluences

• Packaging– Custom versus modified COTs

• System issues– Need decision on low speed vs high speed links– If we adopt high speed links many detailed questions:

• How many modules/link?• Do we want intermediate electrical multiplexing?• How do we introduce some level of redundancy?

SLHC Optoelectronics

Documents

Transcript of SLHC Optoelectronics