Report on test methodologies from the February11th and 12th lab work
Objective: Test the tests
Stretch Camnitz- LightWave DivisionAgilent Technologies Test Equipment [email protected]
Test methods ReportMar 12, 2002
Page 2
Proposal to have an open laboratory prior to theFebruary interim meeting• Proposed procedures must be validated on several devices• Follow up and refinement of “Raleigh” modifications through
subsequent serial PMD teleconferences• Test beds built during between Jan 18th and Feb 11th• A “Public” lab (open to anyone)• A “Private” lab (those who signed up were given 3 hours of private
use on the test beds)• Eight participants
Test methods ReportMar 12, 2002
Page 3
Some results from the January meeting inRaleigh• New proposals for stressed eye receiver testing• New proposals for transmitter jitter testing• Report on root causes for difficulties in performing jitter bathtub
stressed receiver test measurements• Verification needed on “real” devices
Test methods ReportMar 12, 2002
Page 4
Test system overview
• Transmitter test bed:• Jitter bathtub
measurement• Transmitter
Dispersion Penalty(TDP) measurement
• Receiver test bed:• “Old” stressed eye• “Simplified” Stress
Test methods ReportMar 12, 2002
Page 5
D4.1 vs D4.0: What hasn’t Changed:
StressedTestSignal
RXUnderTest
SignalQualityMeasurement
TXUnderTest
Calibration
Test methods ReportMar 12, 2002
Page 6
D4.1 vs D4.0: Two Major Changes:
StressedTestSignal
RXUnderTest
SignalQualityMeasurement
TXUnderTest
Calibration
“Simplified” Stress:Additive Amplitude ISI
Replace Jitter BTWith Eye Mask +TDP
Test methods ReportMar 12, 2002
Page 7
Contract Between TX and RX
Bathtub jitterTX must produce less jitter than
stressed eyeRX must successfully receive
stressed eye
• TDP methodology• TX must produce a smaller
sensitivity penalty than stressedeye
• RX must successfully receivestressed eye
Test methods ReportMar 12, 2002
Page 8
Matrix of measured Penalties
Three transmitters
Two receivers
“Verygood”
referencetransmitter
Transmitterunder test
Maximum dispersion 10-12
TDP
dBm
Variableoptical
attenuator
Force decisionpoint +/-0.1? UI
Stressedeye
generator
Testreceiver
CDR
Receiverunder
testCDR
BER
10-12
TDP
dBm
BER
_______________________________________| | Receiver || Transmitter | Test Rx | Rx U.T. || V.good ref. | cal. for TDP | Inform. sens. || Tx U.T. | TDP | || Stressed eye |cal.for str.sens. | Norm. sens. |
from Raleigh, NC, January 2002 Matrix of measured Penalties
Test methods ReportMar 12, 2002
Page 9
Effect of Test Equipment non-ideality
Jitter Bathtub method• Tend to over-estimate jitter of TX• Tend to over-estimate jitter in
stressed RX test signal• These two effects tend to partially
cancel out• But, not all test equipment has
equal non-ideality• How does jitter combine?
• TDP method• Substitutional method:
• first order compensation forjitter in measurement RX
• But what about differencesbetween reference RX?
Test methods ReportMar 12, 2002
Page 10
40 MHzJitter
JitterModulator
LPFPatternGenerator
Modulator OpticalAtten
ErrorDetector
O/EConverter
10.3125 GHzClock
Laser1310/1550 nm
2 GHzSine
DUT
OpticalAtten
ClockRecovery
Rx
Tx
10 dB Coupler
Test Fiber
Test System Block Diagram
Test methods ReportMar 12, 2002
Page 11
Receiver Test
• Unstressed• Simplified
Stress• PRBS31
40 MHzJitter
JitterModulator
LPFPatternGenerator
Modulator OpticalAtten
10.3125 GHzClock
Laser1310/1550 nm
2 GHzSine
DUTRx
Tx
7.5 GHz BT filter
Test methods ReportMar 12, 2002
Page 12
Original Stress vs Simplified Stress
Original Stress:Emphasis on LPFAdded RJ• Hard to Adjust Filter• Need BT measurement to Calibrate• Non-ideal Frequency Response:
• larger pattern dependence• larger Sigma, smaller W
Simplified Stress:Additive Amplitude ISISinusoidal Jitter• Easier to Adjust ISI, SJ• Measure with Oscilloscope• More ideal frequency response• Smaller pattern dependence• W larger, Sigma is smaller
Test methods ReportMar 12, 2002
Page 13
Clean signal- 7.5 GHz BT filter
20 GHz scope BW
Test methods ReportMar 12, 2002
Page 14
Original Stress; 4.5 GHz filter
Test methods ReportMar 12, 2002
Page 15
Original stress-Pattern dependence
PRBS7PRBS31
Log
Erro
r Rat
e
Test methods ReportMar 12, 2002
Page 16
Simplified Stress- 7.5 BT filter
20 GHz scope BW
Test methods ReportMar 12, 2002
Page 17
PRBS 31 – Nostress vs Simplified StressLo
g Er
ror R
ate
Test methods ReportMar 12, 2002
Page 18
PRBS 31 – Nostress vs Simplified Stress Vertical “Q” Plot
Amplitude Slice Setpoint
Log
Erro
r Rat
e
Test methods ReportMar 12, 2002
Page 19
Transmitter Test
• Eye Mask• Bathtub Jitter• TDP (+- 0.1 UI
decision point)• PRBS31
ErrorDetector
O/EConverter
DUT
OpticalAtten
ClockRecovery
Rx
Tx
10 dB Coupler
Test Fiber
Test methods ReportMar 12, 2002
Page 20
Bathtub Curve vs TDP
Bathtub Jitter Measurement• Tests Low and High Probability
Jitter• Does not test Vertical Eye Closure
• Left to eye mask
TDP• Classical TDP tests Vertical Eye
Closure• TDP with Offset sampling point
tests Vertical Eye Closure and Jitter• Sensitivity to Jitter depends on
choice of Sampling Point Offset
Test methods ReportMar 12, 2002
Page 21
RX Frequency response
-12
-10
-8
-6
-4
-2
0
2
0.1 5.1 10.1 15.1 20.1
Frequency GHz
Am
plitu
de d
BRef RX Ref RX 7.5 GHz BT filter
Test methods ReportMar 12, 2002
Page 22
TDP Meas and BT measurement on Simpl stressLo
g Er
ror R
ate
X XDecision points
Test methods ReportMar 12, 2002
Page 23
Reference RX penalties; 7.5 GHz RX BT filter
SimplifiedStress +-10ps
+-1 ps+-10ps
+-1 ps
No Stress
3.5 dB2 dB
Log
Erro
r Rat
e
Test methods ReportMar 12, 2002
Page 24
Effect of Decision Point Offset- ref RX
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25 30 35
Total Decision Point Offset [ps]
Pena
lty d
B
Series1
Test methods ReportMar 12, 2002
Page 25
Direct Tx No Fiber (Pier’s Mask)
Test methods ReportMar 12, 2002
Page 26
Direct Laser Tx With Fiber (Petar’s Mask)
Test methods ReportMar 12, 2002
Page 27
Tx Test; PRBS31; No Stress; “10 km” fiberLo
g Er
ror R
ate
Test methods ReportMar 12, 2002
Page 28
TDP +- 0.1 UI; TX through FiberLo
g Er
ror R
ate
CleanRefSignal
SimplifiedStress
Log
Erro
r Rat
e
2.5 dB penalty
Test methods ReportMar 12, 2002
Page 29
TDP correlation to BT curves
Correlation
0
0.5
1
1.5
2
2.5
3
3.5
0 10 20 30 40 50 60 70
BT width @1E=10 [ps]
Pena
lty d
B
TX DUTs
Test methods ReportMar 12, 2002
Page 30
TDP Table- TX results
3.5 dB penaltyStressed Eye
1 to 3 dB penaltyTX DUT
calibrationClean Source
RX DUTReference RX+/- 0.1 UI
Test methods ReportMar 12, 2002
Page 31
Receiver Test
• Unstressed• Simplified
Stress• PRBS31
40 MHzJitter
JitterModulator
LPFPatternGenerator
Modulator OpticalAtten
10.3125 GHzClock
Laser1310/1550 nm
2 GHzSine
DUTRx
Tx
7.5 GHz BT filter
Test methods ReportMar 12, 2002
Page 32
Rx BER vs OMA – Simplified Stress vs NostressLo
g Er
ror R
ate
SJ ~.25UI
No Stress
Simplified Stress
4 dB
Test methods ReportMar 12, 2002
Page 33
Rx Sensitivity with Simplified StressLo
g Er
ror R
ate
Test methods ReportMar 12, 2002
Page 34
TDP Table
3.5-7 dB penaltyOMA=-11 to –5dBm
3.5 dB penaltyStressed Eye
1 to 3 dB penaltyTX DUT
Nominal sensitivity-18 to –11 dBm
calibrationClean Source
RX DUTReference RX+/- 0.1 UI
Test methods ReportMar 12, 2002
Page 35
Summary
• Simplified Stress BT curves qualitatively similar to actual DML TXcurves
• TDP measured with +-0.1 UI decision point offset correlates with BTcurve
• All TX DUTs measured smaller penalties than simplified stress• Simplified stress induced moderate to large power penalties in RX
DUTs• Simplified Stress/TDP methodology seems to be workable using
optimized test Receiver