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Optical Transceiver

User Training

Transceiver Testing April 2011

April 2011

OTX Testing User Training

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


Effect of increasing bias current Effect of increasing Modulation Voltage

Definitions: AOP, OMA, ER

-

April 2011


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


• 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


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


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


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


Stage 3 – Final Test (Option 1)N2102B

Golden Source


Optical Fiber (MMF)

Data Electrical RX

)

VOA, e.g. N7768A

DUT

N2101B

N2100B

April 2011


Optical & Electrical Tested in Parallel N2100B

Final Test (Option 2)

G ld S

N2102B

Golden Source


Optical Fiber (MMF)

Data Electrical RX

)

VOA, e.g. N7768ARF Switch

DUT

Optical & Electrical Tested & Serially with Crosstalk

RF SwitchN2101B

April 2011


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


Optical & Electrical Tested Serially (no crosstalk testing)

Optical Parameters Measured – Mask TestMin Required Equipment:

Typical Measurement Conditions:

Pattern Generator

Optical DCA


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


Optical Parameters Measured – Rise/Fall Time

Min Required Equipment:

Pattern Generator

Optical DCAOptical DCA


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


Optical Parameters Measured – Jitter – RMS & DJ

Min Required Equipment:

Pattern Generator



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 (?)


Set by various Standards

Typical Limit TJ 0.26UI for BER 10-12

April 2011


Optical Parameter MeasuredDUT Disabled – Low Light MeasurementDUT Disabled Low Light MeasurementMin Required Equipment:

Pattern Generator


Optional: Optical Power Meter

T i l M t C ditiTypical Measurement Conditions:

DUT is disabled via DISABLE PIN


Signal must be less than 26 dBm

April 2011


Electrical Parameters measured By DCARise & Fall Time & JitterRise & Fall Time & JitterMin Required Equipment:

Pattern Generator

Electrical DCA


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


Set by various Standards

Typical Limit TJ 0.26UI for BER 10-12

April 2011


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


Sample Data Sheet, continued

April 2011


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