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Optical Transceiver
User Training
Transceiver Testing April 2011
April 2011
OTX Testing User Training
Page 1
How is an SFP tested?Stage 1 – The Tuning StageStage 1 The Tuning Stage
ALL SFP’s need to be biased/configured individually.
Th t th t d t t dThe parameters that need to tuned are :
Average Optical Power (AOP)
Extinction Ratio
& OMA (O ti l M d l ti A lit d )& OMA (Optical Modulation Amplitude)
Crossing Percentage
The variables that are changed are:
Bias Current & Modulation Voltage
April 2011
OTX Testing User Training
Page 2
Effect of increasing bias current Effect of increasing Modulation Voltage
Definitions: AOP, OMA, ER
-
April 2011
OTX Testing User Training
Page 3
How is the Tuning Done?I t t R i d P tt G t P tt i tInstruments Required: Pattern Generator
& DCA
Pattern requirement: Ideally PRBS7 but optional
Tuning can be done:
Manually via a OR AutomatedManually via a screwdriver
OR Automatedvia the i2C bus & a PC
IMPORTANT POINTS TO REALISE:
• The Bias Current & Modulation Voltage are controls within the SFP
• For Multi-Rate SFP’s the settings for each rate is stored
• Adjusting the Pattern Generators output Modulation Voltage has no effect
• Typically the PXIT BERT is used at this stage but only for Pattern Generation
April 2011
OTX Testing User Training
Page 4
• Typically the PXIT BERT is used at this stage – but only for Pattern Generation
Stage 1 – Tuning Set-Up
N2101BN2101BN2100B
SFP Eval BoardBERT DCAData Electrical TXClock Signal
April 2011
OTX Testing User Training
Page 5
g
Optical Fiber (MMF)
Stage 2 – Receiver Sensitivity Test Set-up
Variable
Data Electrical TXClock Signal
Optical Fiber (MMF)
Data Electrical RX
Variable Optical Attenuator
Golden SFPOptical Fiber (MMF)
N2101B
DUT – SFP
April 2011
OTX Testing User Training
Page 6
BER SensitivitySensitivity is a measure of how weak an input signal can get before the bit error ratio (BER) exceeds some specified numberSensitivity is a measure of how weak an input signal can get before the bit-error ratio (BER) exceeds some specified number.
Protocol Required BER
SONET 10-10
Gigabit Ethernet 10-12Gigabit Ethernet 10
& Fibre Channel 10-12
How long does it take to measure a reliable BER of 10-12 at 1GBps?
A few seconds? A few minutes? A few hours? 1 Day??
NO NO NO YES
April 2011
OTX Testing User Training
Page 7
27 hours for 100 errors @ 1 Gig !!
BER Measurements in Manufacturing
Manufacturing Requirement – test time must be short
Option 1:Just measure BER at 1 low power level & compare to Jus easu e a o po e e e & co pa e oa known pass value
Option 2:Measure Waterfall curve at a few low power levels
& extrapolate to get BER at higher power levels
Measurement time can be cut from minutes or hours to seconds.
April 2011
OTX Testing User Training
Page 8
Stage 3 – Final Test (Option 1)N2102B
Golden Source
Data Electrical TXClock Signal
Optical Fiber (MMF)
Data Electrical RX
)
VOA, e.g. N7768A
DUT
N2101B
N2100B
April 2011
OTX Testing User Training
Page 9
Optical & Electrical Tested in Parallel N2100B
Final Test (Option 2)
G ld S
N2102B
Golden Source
Data Electrical TXClock Signal
Optical Fiber (MMF)
Data Electrical RX
)
VOA, e.g. N7768ARF Switch
DUT
Optical & Electrical Tested & Serially with Crosstalk
RF SwitchN2101B
April 2011
OTX Testing User Training
Page 10
Optical & Electrical Tested & Serially with Crosstalk N2100B
Golden Source
Final Test (Option 3)
RF Switch Data Electrical TXClock Signal
Optical Fiber (MMF)
Data Electrical RX
)
DUT
Optical & Electrical Tested Serially (no crosstalk testing)
N2101BN2100B
April 2011
OTX Testing User Training
Page 11
Optical & Electrical Tested Serially (no crosstalk testing)
Optical Parameters Measured – Mask TestMin Required Equipment:
Typical Measurement Conditions:
Pattern Generator
Optical DCA
Typical Measurement Conditions:
PRBS 7 (1,2&4xFC,GigE)
No. Of Waveforms ( large 200 -500)
4th O d BT filt t b d4th Order BT filter must be used
Correct Mask must be used
Done at Final Test
Done at 1 optical level (?)Done at 1 optical level (?)
Pass Fail Criteria:
Manufacturer sets their own Pass/ Fail Margin
Typical Margin Limit – 30%
Quality can be assessed by Finding Max Fail Margin
April 2011
OTX Testing User Training
Page 12
Optical Parameters Measured – Rise/Fall Time
Min Required Equipment:
Pattern Generator
Optical DCAOptical DCA
Typical Measurement Conditions:
PRBS 7 (1,2&4xFC,GigE) (?)
No. Of Waveforms (small or large)
4th Order BT filter ON (required) & OFF
Done at Final Test
Done at 1 optical level (?)
20% to 80% points
P F il C it iPass Fail Criteria:
Manufacturer sets their own (??)
Typical Limit @ 4Gig 105ms (filter on)
April 2011
OTX Testing User Training
Page 13
Optical Parameters Measured – Jitter – RMS & DJ
Min Required Equipment:
Pattern Generator
Optical DCAOptical DCA
Typical Measurement Conditions:
K28.7 – RMS Jitter
K28.5 – DJ JItter
No. Of Waveforms (Larger but not Huge)
4th Order BT filter ON (required?)
Done at Final Test
Done at 1 optical level (?)
P F il C it iPass Fail Criteria:
Set by various Standards
Typical Limit TJ 0.26UI for BER 10-12
April 2011
OTX Testing User Training
Page 14
Optical Parameter MeasuredDUT Disabled – Low Light MeasurementDUT Disabled Low Light MeasurementMin Required Equipment:
Pattern Generator
Optical DCAOptical DCA
Optional: Optical Power Meter
T i l M t C ditiTypical Measurement Conditions:
DUT is disabled via DISABLE PIN
P F il C it iPass Fail Criteria:
Signal must be less than 26 dBm
April 2011
OTX Testing User Training
Page 15
Electrical Parameters measured By DCARise & Fall Time & JitterRise & Fall Time & JitterMin Required Equipment:
Pattern Generator
Electrical DCA
Typical Measurement Conditions:
Some test Diffentially (Most S E)Some test Diffentially (Most S.E)
Some test Just 1 of the SFP’s RX o/p
No. Of Waveforms (Larger but not Huge)
Done at Final TestDone at Final Test
Done at 1 optical level
P F il C it iPass Fail Criteria:
Set by various Standards
Typical Limit TJ 0.26UI for BER 10-12
April 2011
OTX Testing User Training
Page 16
Sample Data Sheet (for illustration only)( y)
No intent to go through this in
APPENDIX
No intent to go through this in detail, but useful to have.
APPENDIX
April 2011
OTX Testing User Training
Page 17
Sample Data Sheet, continued
April 2011
OTX Testing User Training
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Sample Data Sheet, continued
April 2011
OTX Testing User Training
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Sample Data Sheet, continued
April 2011
OTX Testing User Training
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Sample Data Sheet, continued
April 2011
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Sample Data Sheet, continued
April 2011
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Sample Data Sheet, continued
April 2011
OTX Testing User Training
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