opto-rx measurements for pixel upgrade

Opto-Rx Measurements for Pixel Upgrade

M.Friedl, M.Pernicka

HEPHY Vienna

2M.Friedl, M.Pernicka (HEPHY Vienna)23 April 2009

Opto-Rx Measurementsfor Pixel Upgrade

What? Why? How?

• Digital optical 320 Mb/s transmission is intended for pixel phase 1 upgrade

• Recycling of existing optical links possible?– Sender side appears OK– Most severe bandwidth limitation in

12-way receiver (ARx12) ~100 MHz• Comparative test of digital transmission

at 320 Mb/s between existing ARx12 and Zarlink engineering sample

• Each mounted on test board (clean environment)

• ARx12 with external fast, self-biased,LVDS-output comparators (ADCMP604)

ARx12

Zarlink

Comp.



Sender / Receiver Setup

Agilent 8110Apulse/patterngenerator

AOH (TOB type)

AOH test setup

Tektronix DSA70804 Scope

Receiverboards



Test A – Unbalanced Periodal Signals

• 40 MHz with variable duty cycle (Ton/Tperiod)

• Considerable distortions up to misinterpretation due to threshold imbalance

• Bad result. However: This is a very unrealistic situation…

0 1 1 0 0 0 0 0 0 1 1 0

Example: 25% duty cyclerepresents repetitive unbalanced 1100 0000 code

Ton Tperiod

Code SenderOpt_Head(analog) ARx12 Zarlink

1111 0000 50.0% 49.8% 47.3% 50.1%

1100 0000 25.0% 25.6% 32.7% 35.3%

1000 0000 12.5% 12.4% 27.0% ---

Receiver



Test B – Balanced PRBS @ 320Mb/s with Sequence of 0s or 1s

• 15000 words of programmable pattern filled with PRBS14 (=balanced)

• Programming 1s (or 0s) from the beginning of the pattern until remaining PRBS bits become corrupted

• Amazing result:– Zarlink tolerates ~700 consecutive 1s (or 0s) without effect on

subsequent pattern– With more than ~700 same symbols, subsequent single bits

deteriorate or vanish completely (symmetric behavior)– ARx12 even tolerates ~3000 consecutive 1s

• Perfectly suitable for pixel system, where even 20 consecutive 1s or 0s are extremely unlikely



Test C – Eye Diagram @ 320Mb/s (1)

• Optical Head (analog)

• Limited rise time (mostly due to pattern generator)

• Stable timing

• Solid eye opening




• Zarlink (digital)

• Perfectly fine

• High bandwidth(Zarlink can do 1.6Gb/s)




• ARx12+comparator (digital)

• Narrow opening withbest settings of pulse generator (amplitude),AOH (offset) and Rx12(offset)

• Unusable with non-optimal settings(where Zarlink still works perfectly well)



Test Conclusions

• ARx12 performance is marginal – even on a lab test bench in a noise-free environment

• Needs careful tuning of parameters in order to work• Hence we don’t recommend its use in a production system

• Zarlink works very well – but is not a commercial product• Normally 850nm, this engineering sample has 1310nm photodiode• Francois is in contact with manufacturer to see if we can get 200

pcs. of 1310nm wavelength version

• Alternative: ARx12 mechanics + photodiode with faster (digital) amplifier

• Roland is in contact with manufacturer (Helix)



Modification of Pixel-FED (1)

New daughter board(instead of 3 ADC cards)including Zarlink receiver

• Don’t need to remove current ARx12 allowseasy swapping betweenold and new systems

• Need new front panelin any case

• Keep single slot size

• Keep VME base board



Modification of Pixel-FED (2)

Old ADC card

New daughter board

Zarlink (mountedon daughter board)

Front panel

VME board

Need higher connectors than nowAvailable from different vendor (samples ordered for compatibility tests)

OLD

NEW

ARx12

ARx12

opto-rx measurements for pixel upgrade

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