DOIM Parallel Optical Links: TX/RX

S. Hou, R.S. Lu19-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 A511 166

http://hepmail.phys.sinica.edu.tw/~doim

Introduction

DOIM: Dense Optical Interface Module

Byte-wide parallel optical link8-bits + clock53 Mbyte/sec, BER10-12

Transmitter :Laser-diode arrayASIC driver chip

Receiver :PIN-diode arrayASIC 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 array1550 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

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,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

Transmitter assembly

Die-bond / Wire bondlaser-diode array on BeO submountdriver chip on substratefibers on V-groove

Alignmentfibers to laser emitting facets

Receiver : PIN & ASIC driver

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

Receiver assembly

Die-bond / Wire bondPIN-diode array on Al2O3 submountdriver chip on substratefibers 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 http://hepmail.phys.sinica.edu.tw/~rslu/doim/

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 (oC)

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 (30oC)

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 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 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

BERTPC ISA boards TTL toTbert, 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=1.5x1013, (704 krad GaAs)

Temperature on substrate 44~76oC

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=3.0x1013 (1.4 Mrad GaAs)

IUCF irradiation

2 TX, AC mode, 3 flux rate

Cumulative fluence: 4.3, 12.8, 30 X1012

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 X1012

Cumulative dose: 320, 640 krad

IUCF irradiation

2 TX, DC mode, 3 flux rate, 8hours annealing

Cumulative fluence: 1.7, 5.1, 11.9 X1012

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