Bandwidth of Micro Twisted-Pair Cables
and Spliced SIMM/GRIN Fibers and
Radiation Hardness of PIN/VCSEL Arrays
Richard Kass
The Ohio State University
W. Fernando, K.K. Gan, A. Law, H.P. Kagan, R.D. Kass, S. Smith
The Ohio State University
M.R.M. Lebbai, P.L. Skubic
University of Oklahoma
OUTLINE
Introduction-ATLAS/Pixel Detector/SuperLHC
Bandwidth of micro twisted-pair cables
Bandwidth of fusion spliced SIMM-GRIN fibers
Radiation hardness of PIN/VCSEL arrays
Summary
R. Kass
IEEE06/San Diego
N18-5 1
The Current ATLAS Pixel Detector
ATLAS is a detector at CERN designed to study 14 TeV pp collisions
Detector upgrade planned for Super-LHC in 2015
Pixel Detector:
ATLAS’s Inner most charged particle tracker
Measures (x,y,z) to ~30 mm
Pixel detector is based on silicon
Pixel size 50mm by 400 mm ~100 million
pixels
Radiation hardness is an issue
must last ~ 10 years
A pixel module contains:
1 sensor (2x6cm) ~40000 pixels
16 front end (FE) chips 2x8 array
Flex-hybrid
1 module control chip (MCC)
There are ~1700 modules
~108 channels
~1.85m
R. Kass
IEEE06/San Diego
N18-5 2
Present Pixel Opto-link Architecture
Current optical link of pixel detector transmits signals at 80 Mb/s
Opto-link separated from FE modules by ~1m
transmit control & data signals (LVDS) to/from modules on micro twisted pairs
Use PIN/VCSEL arrays
Use 8 m of rad-hard/low-bandwidth SIMM fiber fusion
spliced to 70 m rad-tolerant/medium-bandwidth GRIN fiber
a Simplify opto-board and FE module production
a Sensitive optical components see lower radiation level than modules
a PIN/VCSEL arrays allow use of robust ribbon fiber
~150m
~1m
optoboard
VCSEL:
VDC:
PIN:
DORIC:
R. Kass
Vertical Cavity Surface Emitting Laser diode
VCSEL Driver Circuit
PiN diode
Digital Optical Receiver Integrated Circuit
optoboard holds VCSELs, VDCs, PINS
IEEE06/San Diego
N18-5 3
R&D Issues for Super-LHC
A Bandwidth of ~ 640 Mb/s is needed
Can micro twisted pair transmit at this speed?
Can fusion spliced SIMM/GRIN fiber transmit at this speed?
Radiation Hardness of opto-board components
Can PIN/VCSEL arrays survive SLHC radiation dosage?
~150m
~1m
optoboard
R. Kass
IEEE06/San Diego
N18-5 4
Bandwidth of Micro Twisted Pairs
Bandwidth of 3 micro twisted-pair wires were compared.
Wire used is MWS Wire Industries Twistite
38 AWG (25mm insulation, 100um wire, 150mm OD) (current pixel cable)
5 turns per inch, with 75Ω termination.
36 AWG (9um insulation, 127um wire,145um OD)
10 turns per inch , with 100Ω termination.
5 turns per inch, with 75Ω termination.
Bandwidth measurements made with LeCroy Wavemaster 8600A digital scope
(6 GHz input bandwidth, and 7.5GHz differential probe)
Eye diagrams made using pseudo-random data (650Mb/s, 1 Gb/s)
Eye masks adapted from Gigabit Ethernet Spec. (IEEE std. 802.3)
R. Kass
IEEE06/San Diego
N18-5 5
Bandwidth of Micro Twisted Pairs
Bandwidth of 3 micro twisted-pair wires were compared:
38 AWG/100 mm, 2 turns/cm (current pixel cable)
36 AWG/127 mm, 2 turns/cm
36 AWG/127 mm, 4 turns/cm
1000
AWG 38, 5 TPI
AWG 36, 5 TPI
AWG 36, 10 TPI
800
2 T/cm
2 T/cm
4 T/cm
AWG 38, 5 TPI
Fall Time (20% - 80%) (ps)
Rise Time (20% - 80%) (ps)
1000
600
400
200
AWG 36, 5 TPI
800
AWG 36, 10 TPI
600
400
200
0
0
50
70
90
110
Length (cm)
130
150
50
70
90
110
Length (cm)
130
150
The Current pixel cable is the best!
R. Kass
IEEE06/San Diego
N18-5 6
Micro Twisted Pair Eye Diagrams
60 cm pixel cable
140 cm pixel cable
650 Mb/s
Transmission at 650 Mb/s is adequate
1.3Gb/s
Transmission at 1.3 Gb/s may be acceptable
R. Kass
IEEE06/San Diego
N18-5 7
Bandwidth of Fusion Spliced Fiber
GRIN: Graded Index multi mode optical fiber
GRIN fibers are rad-tolerant with medium bandwidth
SIMM: Single Index MultiMode optical fiber
SIMM fibers are rad-hard but lower bandwidth
Present system designed to work at 80Mb/s but will it work at1Gb/s ?
Bandwidth Test Setup for existing Pixel Architecture
splices made using Fujikura fusion splicer
R. Kass
IEEE06/San Diego
N18-5 8
Bandwidth of Fusion Spliced Fiber
1 m GRIN fiber
8 + 80 m spliced SIMM/GRIN fiber
2 Gb/s
Transmission up to 2 Gb/s looks adequate
R. Kass
IEEE06/San Diego
N18-5 9
Radiation Level at SuperLHC
Optical link of current pixel detector is mounted on patch panel:
a much reduced radiation level compared to collision point:
SI (PIN) @ SLHC:
n 2.5 x 1015 1-MeV neq/cm2
n 4.3 x 1015 p/cm2 or 114 Mrad for 24 GeV protons
GaAs (VCSEL) @ SLHC:
n 14 x 1015 1-MeV neq/cm2
n 2.7 x 1015 p/cm2 or 71 Mrad for 24 GeV protons
R. Kass
IEEE06/San Diego
N18-5 10
SLHC Issues for PIN/VCSEL
PIN:
What is responsivity after irradiation?
What is rise/fall time after irradiation?
VCSEL:
Driver chip will most likely be fabricated with 0.13 mm process
operating voltage is 1.2 V
thick oxide option can operate at 2.5 V
a VCSEL requirement: < 2.3 V to produce 10 mA or more
some VCSELs require > 2.3 V to operate at 10 mA or more
What is rise/fall time after irradiation?
What is optical power after irradiation?
What current is needed for annealing?
We irradiated 4 different kinds of VCSELs:
Optowell
Advanced Optical Components (AOC)
ULM Photonics (5Gb/s and 10Gb/s versions)
R. Kass
IEEE06/San Diego
N18-5 11
Real Time Monitoring in T7 Beam Test
Real time testing of opto-board system using loop-back setup
Compare transmitted and decoded data
measure minimum PIN current for no bit errors
Measure optical power
25m optical
Opto-board
fiber cable
clock
bi-phase marked
optical signal
PIN
decoded data
VCSEL
VDC
decoded clock
VCSEL
VDC
In control room
DORIC
Signal routed back to
opto-baord via test board
attached to 80-pin
connector & test board
data
In beam
Bit error test setup
at CERN’sT-7 beamline
24 GeV protons
Two VCSEL arrays
from same vendor
per opto-board
R. Kass
IEEE06/San Diego
N18-5 12
Results: PIN Responsivity
PINS are manufactured by TRUELIGHT
7
0.7
Post-irrad
Pre-irrad
6
(mA/mW)
Responsivity
PIN Responsivity (A/W)
0.6
Count
Count
5
4
3
2
1
0.5
0.4
0.3
0.2
Pre Irrad
Post Irrad
0.1
0
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1
6
11
16
21
26
Channel Number
channel number
Responsivity
Responsivity (mA/mW)
(uA/uW)
Responsivity of PINs decrease by ~50% after SLHC dosage
R. Kass
IEEE06/San Diego
N18-5 13
VCSEL LIV Characteristics
Pre-irradiation
OSU V0010 (Advanced Optical Components HFE8012-101)
Opto-Board 3151 Left VCSEL
OSU V0012 (Optowell AM85-1N112)
Opto-Board 3152 Left VCSEL
3500
3500
2
2.5
1.8
3000
3000
1000
Optowell
500
1.4
1.2
2000
1
1500
0.8
1000
0.6
AOC
0.5
500
Voltage (V)
(mW)
power
Power
(μW)
1
Voltage (V)
1500
Voltage (V)
(mW)
power
Power (μW)
1.5
2000
2500
Voltage (V)
1.6
2
2500
0.4
0.2
0
0
4
6
8
10
0
12
0
0
2
Current (mA)
current
(mA)
ULM 5Gb/s
0.5
0
0
6
8
10
12
Current (mA)
current (mA)
(mW)
power
Power (μW)
1
Voltage (V)
1500
Voltage (V)
power
Power (mW)
(μW)
1.5
2000
2.5
2500
2
2500
4
12
3000
3000
2
10
OSU V006 (ULM 10 Gb/s ULM850-10-TN-N0112U)
Opto-Board 2150 Left VCSEL
2.5
0
8
Current (mA)
3500
500
6
current (mA)
OSU V005 (ULM 5 Gb/s ULM850-05-TN-B0112U)
Opto-Board 2151 Left VCSEL
1000
4
2
2000
1.5
1500
1
1000
ULM 10Gb/s
500
Voltage (V)
2
Voltage (V)
0
0.5
0
0
0
2
4
6
8
10
12
Current (mA)
current
(mA)
ULM requires higher voltage to operate
All arrays have very good optical power
R. Kass
IEEE06/San Diego
N18-5 14
VCSEL Power vs Dosage
SLHC
0.6
40
0.4
20
0.2
0.0
0
100
200
Time (Hours)
300
ULM 5G
2.8
2.4
Data Optical Power (mW)
60
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Ch 6
Ch 7
Dose
2.0
1.6
0
400
40
20
0.4
0.0
0
100
200
Time (Hours)
300
40
0.3
20
0.0
0
1.2
60
0.8
AOC
100
1.2
60
0.6
1.5
80
80
71 MRad
0.9
120
71 MRad
100
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Ch 6
Ch 7
Dose
1.2
120
0
400
100
200
Time (Hours)
ULM 10G
0
400
120
100
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Ch 6
Ch 7
Dose
0.9
300
Dose (Mrads)
80
71 MRad
AOC
80
71 MRad
60
0.6
40
0.3
Dose (Mrads)
0.8
1.5
Data Optical Power (mW)
1.0
100
Data Optical Power (mW)
Ch 1
Ch 2
Ch 3
Ch 4
Ch 5
Ch 6
Ch 7
Dose
1.8
Dose (Mrads)
Data Optical Power (mW)
1.2
120
Dose (Mrads)
Optowell
1.4
20
0.0
0
100
200
Time (Hours)
300
0
400
Optowell survives to SLHC dosage
Other VCSELs might survive with more annealing or slower irradiation
R. Kass
IEEE06/San Diego
N18-5 15
Summary
J Micro twisted-pair cable of current ATLAS pixel detector
can be used for transmission up to 1 Gb/s
J Fusion spliced SIMM/GRIN fiber can transmit up to 2 Gb/s
J PIN responsivity decreases by 50% after SLHC dosage
J Optowell VCSEL survives SLHC dosage
J Current opto-link architecture satisfies SLHC requirements
R. Kass
IEEE06/San Diego
N18-5 16
extra slides
R. Kass
IEEE06/San Diego
N18-5 17
Setup for Irradiation in Shuttle at CERN
25 meter optical fiber
Opto-boards
Rad hard
optical
fibers
CERN T7
Remotely moves
in/out of beam
R. Kass
IEEE06/San Diego
CERN T7
N18-5 18