DOIM Parallel Optical Link s: TX/RX S. Hou, R.S. Lu 19-Dec-2003, Lake Geneva

Outline Electrical characteristics Laser array, PIN array, driver chips Bit-error rate test BERT at FCC Current balance test Enable, laser on/off Radiation Hardness UCDavis, INER, IUCF Most materials in cdf note 6497 Vertex 2002, NIM A

Introduction DOIM: Dense Optical Interface Module Byte-wide parallel optical link 8-bits + clock 53 Mbyte/sec, BER  Transmitter : Laser-diode array ASIC driver chip Receiver : PIN-diode array ASIC receiver chip Multi-mode fiber ribbon

DOIM implementation : transmitters Transmitters on Port Cards Total 570 transmitters 128 Port Cards, 5 transmitter each board

DOIM implementation : receivers Receivers on FTM 10 receivers on each board, reading 2 Port Cards

Laser diode array InGaAs/InP Edge-emitting laser diode array 1550 nm wavelength 12-ch diode array (9 used) 250  m pitch 20 mA/channel Cleaved mirrors Facet coating Bare laser power:  1 Insertion to fiber: 200 ~ 800  W/ch Custom made by Chunghwa Telecom Light cone : uniformity in far-field angle major application problem

Laser transmitter ASIC driver 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 : V cc -V LD across output transistor, 50 , laser control current consumption At 3V, 20mA/ch nominal ~2mA/0.1V adjustable slope

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

Receiver : PIN & ASIC driver 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

Receiver assembly Die-bond / Wire bond PIN-diode array on Al 2 O 3 submount driver chip on substrate fibers on V-groove Alignment, fibers to PIN-diodes

Laser transmitter characteristics Inputs: ECL or LVDS signal TTL-enable Constant Current through LDA or dummy 50  Light by O/E probe Input ECL TTL enable Current probe O/E light TTL enable

Current balance test 16 TX’s have been tested. Max. current change at 7mA while enable/disable TX. Records at

Laser diode: L-I-V Laser light at I,V and Temperature I-V approximately linear Duty cycle stable output to input 50% Linear to temperature Temp ( o C)

Receiver response Laser light source chosen for wide distribution light pulse width are consistent Examine Receiver ECL outputs use Tektronix diff. probe Consistent duty cycles in operation range 2.8~3.2V Saturates for high light level

Uniformity : transmitter light outputs Laser light at pigtail (30 o C) channel-by-channel span ~400  W  ~72  W to the mean/module Reduced dynamic range in operation

Uniformity : laser light pulse widths Light pulse width is uniform  ~1%, indep. of light power

Uniformity : receiver ECL output 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, (2 nd batch)  =0.7% 4% wider in 1 st batch due to chip tuning Wide light input range Saturation at 970  W

Uniformity : ECL duty cycle deviation Receivers examied with Input lights ~950  W, width 45% for all channels ECL outputs of a module deviation to the mean  ~1.5% for both batches

Bit-Error Rate test BERT PC ISA boards TTL to Tbert, Rbert boards At 63 MHz, minimum BER  10 –12

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.

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.

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

IUCF DOIM irradiation Nice test setup, cooling fan killed 202 MeV proton, fluence=1.5x10 13, (704 krad GaAs) Temperature on substrate 44~76 o C AC mode DC mode

CDF requirement : Laser transmitter 200 krad tolerance Online measurement, AC/DC modes, water chilled fiber ECL inputs (pulse generator) Fiber ribbon cable outputs  Octopus  OE +Digital scope  DC PIN meters IUCF 200 MeV proton Irradiation

IUCF irradiation, signal quality AC mode (25MHz), laser signal monitored by O/E Two TX’s in beam, one channel eachbefore/after irradiation No degradation in duty cycle Before irradiation at fluence=3.0x10 13 (1.4 Mrad GaAs)

IUCF irradiation 2 TX, AC mode, 3 flux rate Cumulative fluence: 4.3, 12.8, 30 X10 12 Cumulative dose: 200, 600, 1400 krad

IUCF irradiation Flux rate dependence is nil Light degradation is a constant factor  less than 10% at 200 krad

IUCF irradiation 2 TX, AD to DC mode Cumulative fluence: 6.8, 13.6 X10 12 Cumulative dose: 320, 640 krad

IUCF irradiation 2 TX, DC mode, 3 flux rate, 8hours annealing Cumulative fluence: 1.7, 5.1, 11.9 X10 12 Cumulative dose: 80, 240, 560 krad  8hrs

Summary DOIM : delicate, yet tough p-n junction application Edge-emitting laser  sensitive to temperature Receiver  delicate on ECL fiber cable is GLASS!! Radiation tolerance is sufficient for CDF 10% degradation issue, can live on