Experience with Parallel Optical Link

1
Experience with Parallel Optical Link for the CDF
Silicon Detector
S. Hou for the DOIM group Academia Sinica,
Taiwan
2
Introduction

• DOIM Dense Optical Interface Module
• Byte-wide parallel optical link
• 8-bits clock
• 53 Mbyte/sec, BER?10-12
• Transmitter
• Laser-diode array
• ASIC driver chip
• Receiver
• PIN-diode array
• ASIC receiver chip
• Multi-mode fiber ribbon
• Laser, Electrical characteristics
• Bit-error rate test
• Aging test
• Radiation Hardness
• Implementation in CDF

3
Transmitter Laser diode

• InGaAs/InP Edge-emitting laser diode
• 1550 nm wavelength
• 12-ch diode array (9 used)
• 250 ?m pitch
• 20 mA/channel
• Cleaved mirrors
• Facet coating
• Bare laser power
• ?1 mW/ch _at_20mA
• Insertion to fiber
• 200 800 ?W/ch
• Fabrication by
• Chunghwa Telecom
• Telecommunication Laboratories

4
Transmitter driver ASIC

• Custom design, biCMOS 0.8 ?m,AMS
• bipolar transistors only
• Inputs
• Diff. ECL or LVDS signals compatible
• differential ?100 mV
• Enable by TTL low
• Nine channels
• Vcc-VLD across
• output transistor, 50 ?, laser
• control current consumption
• At 3V, 20mA/ch nominal
• 2mA/0.1V adjustable slope

5
Transmitter assembly

• Die-bond / Wire bond
• laser-diode array on BeO submount
• driver chip on substrate
• fibers on V-groove
• Alignment
• fibers to laser emitting facets

6
Receiver PIN ASIC

• InGaAs/InP PIN diode
• 12-ch array, matching laser diode wavelength
• by TL, Chunghwa Telecom.
• Operation condition
• 50 800 ?W on, ?10 ?W off
• ?1.1 W/module
• Outputs
• differential ECL, nine independent channels

7
Receiver assembly

• Die-bond / Wire bond
• PIN-diode array on Al2O3 submount
• driver chip on substrate
• fibers on V-groove
• Alignment, fibers to PIN-diodes

8
Assembly procedure
9
Transmitter characteristics

• Transmitter tests
• L-I-V and temperature
• 50 MHz diff. Inputs, 2.5V common mode ?100 mV,
  50 Dcyc
• Laser light MT-12ST fanout Tek O/E probe

10
Laser diode L-I-V

• Laser light at 20, 30, 40oC
• water-bath chiller precision 0.1oC
• measured at substrate
• I-V
• little temperature dependence
• approximately linear
• L-V
• Drop with temperature
• Duty cycle
• diff. Input 50
• stable, little offset to 50

11
Laser diode temperature

• Light power vs. Temperature
• Measured in stable
• cooling/heating process
• Temperature at substrate
• precision 0.1oC
• Approximately linear drop
• to temperature

12
Receiver response

• Receiver connected to a Transmitter
• Light power chosen for
• wide distribution
• Light pulse width are consistent
• Receiver ECL outputs
• by a Tektronix diff. probe
• Consistent duty cycles in favored operation
  range (2.83.2V)
• Saturates for high light level

13
Transmitter uniformity light outputs

• Production transmitters
• light from pigtail at 30oC
• wide deviation channel-by-channel
• mainly due to insertion efficiency
• Span within 400 ?W
• ? 72 ?W to the mean/module
• Effect operation dynamic range in
• threshold, saturation limit

14
Transmitter uniformity light pulse widths

• Ch-Ch Light power deviation
• Is approximately a const. scaling factor
• L-V linear fit, normalized slope to L(3V)
  indep. of light power
• Light pulse width is uniform, ?1, indep. of
  light power

15
Receiver uniformity ECL duty cycles

• Two production batches
• monitored at 550 ?W 970 ?W
• light pulse width 45
• ECL duty cycle is uniform
• 48.1 at 550 ?W, (2nd batch)
• ?0.7
• 4 wider in 1st batch
• due to chip tuning
• Wide light input range
• Saturation monitored at 970 ?W

16
Receiver uniformity duty cycle deviation

• Input lights
• 950 ?W, width 45
• for all channels
• ECL outputs of a module
• deviation to the mean
• ?1.5
• for both batches

17
Bit-Error Rate test

• BERT by Fermilab
• PC ISA boards TTL to
• Tbert, Rbert boards
• At 63 MHz,
• minimum BER ?10 12
• Burn-in
• 3-days on ASICs, diodes
• 1-day BERT
• ? reject devices infant mortality
• bad components fail quickly

18
Accelerated Aging test

• 4 transmitters at 60oC, 330 days
• Wear-out degradation
• 0.15 ?0.08 ?W/day at 60oC
• no failure
• Accelerating factor
• Fexp(Ea/ kb) (1/T1 1/T2)
• F29 for T 5oC
• Failure due to light degradation
• Min transmitter spec 200 ?W
• down below receiver threshold 50 ?W
• 100 days at 60oC, or 8 years at 5oC
• 90 C.L. for 0 failure, P0.064
• upper limit 40 ch. In 3 years

19
INER 30 MeV proton Irradiation

• CDF requirement 200 kRad tolerance
• INER test beam transmitter in DC mode.
• fiber connection out of beam area, measuring L,
  T versus dose.

20
Bulk damage, annealing

• Bulk damage dominant, linear dep. to dose
• Ratio of light drop is consistent for a module,
  indep. of light power
• Degradation ?10 for 200 kRad

21
UC Davis 63.3 MeV proton

• UC Davis test beam 10 transmitters on two
  Port Cards
• Examined after 200, 400 kRad, for L I, V
  measurements
• Light degradation 10 for 200 kRad
• Similar I-V, L-V characteristics after
  irradiation,
• slope for L vs. V degrades similarly.

22
DOIM implementation transmitters

• Transmitters on Port Cards
• Total 570 transmitters
• 128 Port Cards,
• 5 transmitter each board

23
DOIM implementation receivers

• Receivers on FTM
• 10 receivers on each board, reading 2 Port Cards

24
Status

• 570 pairs implemented
• 10 bit-error flagged
• excess light at -5oC
• optical reflection, contact
• electrical pin contact
• ?2 has fatal damage
• is improving

25
Summary

• DOIM, a byte-wide optical link is implemented
  in CDF
• Edge-emitting laser light ? linear to I-V
  and T
• Laser-diode array coupling to pigtail fibers
• large deviation ? a major disadvantage
• Radiation tolerance is high
• bulk-damage dominant ? linear degradation
  to dose