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Differential Modal Dispersion Emulator for 10Gb/s MMF Links

Peter KirkpatrickIntel Optical Platform Division

01.06.04

ForIEEE 802.3 10Gb/s on FDDI-grade MMF Study Group

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IntroductionArchitectureArchitectureCapabilities and LimitationsCapabilities and LimitationsPossible Fit to StandardPossible Fit to StandardTap AnalysisTap AnalysisModeling Round Robin FibersModeling Round Robin FibersPower BudgetPower BudgetFuture DevelopmentFuture DevelopmentReferencesReferences

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ArchitectureMethod to reliably reproduce worst case modal dispersionSMF Transversal filter- concept

– Split SMF to N delays, each with VOA, gain to compensate insertion lossReference (DUT) Tx, electrically bandwidth limited

– Can be any SMF pigtailed/pluggable TxReference (DUT) Rx

– Can be any SMF/MMF pigtailed/pluggable Rx

Tx 1:N

PM

PM

PM

PM

N:1 Rx

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Capabilities and LimitationsThis test bed can:This test bed can:–– Create variable DMD to test Rx/EDC performanceCreate variable DMD to test Rx/EDC performance

• Weights are continuously variable• Delays are fixed, but by varying weights over time a

variable delay can be approximated

This test bed cannot:This test bed cannot:–– Evaluate different launch conditionsEvaluate different launch conditions–– Evaluate the effects of spatial filtering (Rx optics)Evaluate the effects of spatial filtering (Rx optics)

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Possible Fit to StandardCompare to 802.3ae 10GBASECompare to 802.3ae 10GBASE--L Stressed RxL Stressed Rx–– Add DMD Emulator between E/O and RxAdd DMD Emulator between E/O and Rx–– Does not test compliance of Rx filteringDoes not test compliance of Rx filtering

802.3ae TDP needs modification to evaluate launch802.3ae TDP needs modification to evaluate launch–– Add DMD characterization after known channelAdd DMD characterization after known channel

Clock

PPG

E/ODMD

EmulatorRx EDC

DUT

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Tap AnalysisTap AnalysisN = 16 TapsN = 16 TapsTap spacing 50psTap spacing 50ps–– Speed of light in fiber, 2.01x10Speed of light in fiber, 2.01x1088 m/sm/s–– Delay is 4.96ps/mmDelay is 4.96ps/mm–– ∆∆l = 10.2l = 10.2 +/+/-- 0.5mm = 50.3 +/0.5mm = 50.3 +/-- 2.5ps2.5ps

Maximum offset is 750psMaximum offset is 750ps–– Empirical match to Round Robin fibersEmpirical match to Round Robin fibers

By weighting taps in real time, effective By weighting taps in real time, effective time delay variation is possibletime delay variation is possible

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Tap AnalysisTap AnalysisTransversal Filter Maximum Delaydelay = 750ps, power ratio = 50%

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800 900 1000

time <ps>

Amplitu

de

Transversal Filter Resolutiondelay = 16x50ps, power ratio = 1/16

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 100 200 300 400 500 600 700 800 900 1000

time <ps>

Am

plitu

de

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Modeling Round Robin FibersModeling Round Robin Fibers

'Bad' Fiber Impulse Response

-20

0

20

40

60

80

100

120

0 300 600 900 1200 1500

Time <ps>

Am

plitu

de

2orange0, 1.0dB ROFL, 500MHz.km

N=16, t=50ps, 7.0GHz

2530, 500 MHz*km2530, 500 MHz*km'Good' Fiber Impulse Response

-20

0

20

40

60

80

100

120

0 250 500 750 1000 1250 1500

Time <ps>

Am

plitu

de

1blue000, OFL, 2530 MHz.km

N=16, t=50ps, 7.5GHz

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Worst of Round Robin FibersWorst of Round Robin Fibers

'Ugly' Fiber Impulse Response

-20

0

20

40

60

80

100

120

140

0 300 600 900 1200 1500

Time <ps>

Nor

mal

ized

Am

plitu

de

1green00, 0.5dB ROFL, 270 MHz.km

N=16, t=50ps, 7.0GHz

270 MHz*km270 MHz*km

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Tap AnalysisTap Analysis-- another exampleanother example22

PepeljugoskiPepeljugoski, et al, 2003, et al, 200317 Modes17 ModesMaximum delay 180psMaximum delay 180psFrom eye diagram this From eye diagram this is not the worst case is not the worst case that we have seenthat we have seen

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Power BudgetCompensate insertion loss with 1310nm SOAProvide Enough Rx Power to Test Overload

--5 dB5 dBFilter ILFilter IL

0 dBm0 dBmMax Rx PowerMax Rx Power

+2 dBm+2 dBmTx PowerTx Power

--2.5 dB2.5 dBCombiner ILCombiner IL

--1 dB1 dBPower Meter ILPower Meter IL

--1 dB1 dBAttenuator ILAttenuator IL

--2.5 dB2.5 dBSplitter ILSplitter IL

+10 dB+10 dBSOA SOA IL+GainIL+Gain

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EDC Test Bed- Future DevelopmentContinue working with MMF Channel– Reference/DUT Tx

• Can be any SMF/MMF Tx– Launch to MMF (center, offset, OFL, ROFL, other)

• Use patchcords• Leverage previous work

– Various (worst case) MMF links– Reference/DUT Rx

• Can be any MMF Rx (want all light, linear TIA or AGC)• Ideal Rx does not exist now, working with available parts

Calibrate SMF Channel to results

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References1.1. Understanding Multimode Bandwidth and Differential Understanding Multimode Bandwidth and Differential

Mode Delay Measurements and Their ApplicationsMode Delay Measurements and Their Applications, P. , P. KolesarKolesar, D. , D. MazzareseMazzarese, , Proceedings of the 51Proceedings of the 51stst IWCSIWCS, , November 2002.November 2002.

2.2. Modeling and Simulation of NextModeling and Simulation of Next--Generation Multimode Generation Multimode Fiber LinksFiber Links, P. , P. PepeljugowskiPepeljugowski, S. , S. GolowichGolowich, A. , A. RitgerRitger, P. , P. KolesarKolesar, A. , A. RisteskiRisteski, , Journal of Journal of LightwaveLightwave TechnologyTechnology, , Vol. 21, No. 5, May 2003.Vol. 21, No. 5, May 2003.