VERTEX 2002
Experience with Parallel Optical Linkfor the CDF Silicon Detector
S. Hou for the DOIM groupAcademia Sinica, Taiwan
VERTEX 2002
Introduction
DOIM: Dense Optical Interface Module Byte-wide parallel optical link
8-bits + clock53 Mbyte/sec, BER10-12
Transmitter :Laser-diode arrayASIC driver chip
Receiver :PIN-diode arrayASIC receiver chip
Multi-mode fiber ribbon
Laser, Electrical characteristics Bit-error rate test Aging test Radiation Hardness Implementation in CDF
VERTEX 2002
Transmitter: Laser diode
InGaAs/InP Edge-emitting laser diode :1550 nm wavelength12-ch diode array (9 used)250 m pitch20 mA/channel
Cleaved mirrorsFacet coating
Bare laser power: 1 mW/ch @20mAInsertion to fiber: 200 ~ 800 W/ch
Fabrication byChunghwa Telecom Telecommunication Laboratories
VERTEX 2002
Transmitter: driver ASIC
Custom design, biCMOS 0.8 m,AMSbipolar transistors only
Inputs :Diff. ECL or LVDS signals compatibledifferential 100 mVEnable 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
VERTEX 2002
Transmitter assembly Die-bond / Wire bond
laser-diode array on BeO submountdriver chip on substratefibers on V-groove
Alignmentfibers to laser emitting facets
VERTEX 2002
Receiver : PIN & ASIC InGaAs/InP PIN diode :
12-ch array, matching laser diode wavelengthby TL, Chunghwa Telecom.
Operation condition :50 ~ 800 W on, 10 W off1.1 W/module
Outputs :differential ECL, nine independent channels
VERTEX 2002
Receiver assembly Die-bond / Wire bond
PIN-diode array on Al2O3 submountdriver chip on substratefibers on V-groove
Alignment, fibers to PIN-diodes
VERTEX 2002
Assembly procedure
VERTEX 2002
Transmitter characteristics Transmitter tests :
L-I-V and temperature 50 MHz diff. Inputs, 2.5V common mode 100 mV, 50% +DcycLaser light MT-12ST fanout & Tek O/E probe
VERTEX 2002
Laser diode: L-I-V
Laser light at 20, 30, 40oCwater-bath chiller precision ~0.1oCmeasured at substrate
I-V little temperature dependenceapproximately linear
L-V Drop with temperature
Duty cyclediff. Input 50%stable, little offset to 50%
VERTEX 2002
Laser diode: temperature
Light power vs. Temperature Measured in stable cooling/heating process
Temperature at substrate precision ~0.1oC
Approximately linear drop to temperature
VERTEX 2002
Receiver response
Receiver connected to a Transmitter Light power chosen forwide distribution
Light pulse width are consistent
Receiver ECL outputsby a Tektronix diff. probe
Consistent duty cycles in favored operation range (2.8~3.2V)
Saturates for high light level
VERTEX 2002
Transmitter uniformity : light outputs
Production transmitterslight from pigtail at 30oCwide deviation channel-by-channelmainly due to insertion efficiency
Span within ~400 W ~72 W to the mean/module
Effect operation dynamic range in threshold, saturation limit
VERTEX 2002
Transmitter uniformity : light pulse widths
Ch-Ch Light power deviationIs approximately a const. scaling factorL-V linear fit, normalized slope to L(3V) indep. of light power
Light pulse width is uniform, ~1%, indep. of light power
VERTEX 2002
Receiver uniformity : ECL duty cycles
Two production batchesmonitored at 550 W & 970 Wlight pulse width 45%
ECL duty cycle is uniform48.1% 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
VERTEX 2002
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
VERTEX 2002
Bit-Error Rate test
BERT by FermilabPC ISA boards TTL toTbert, 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
VERTEX 2002
Accelerated Aging test
4 transmitters at 60oC, 330 days
Wear-out degradation0.15 0.08 W/day at 60oCno failure
Accelerating factor F=exp(Ea/ kb) (1/T1 –1/T2)F=29 for T= – 5oC
Failure due to light degradationMin transmitter spec 200 Wdown below receiver threshold 50 W~100 days at 60oC, or 8 years at – 5oC
90% C.L. for 0 failure, P=0.064 upper limit = 40 ch. In 3 years
VERTEX 2002
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.
VERTEX 2002
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
VERTEX 2002
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.
VERTEX 2002
DOIM implementation : transmitters
Transmitters on Port Cards
Total 570 transmitters
128 Port Cards,
5 transmitter each board
VERTEX 2002
DOIM implementation : receivers
Receivers on FTM
10 receivers on each board, reading 2 Port Cards
VERTEX 2002
Status
570 pairs implemented
~10 % bit-error flaggedexcess light at -5oCoptical reflection, contactelectrical pin contact2% has fatal damage
is improving
VERTEX 2002
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