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Test Plan for PMD Testing of a WDM Receiver

Test Plan for PMD Testing of a WDM Receiver. Henry Yaffe, Principal January 2004. Recommended Test Program. Process Establish test procedure (automation recommended) Schedule time in front of systems Experiments: Measure bare receiver

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Test Plan for PMD Testing of a WDM Receiver

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  1. Test Plan for PMD Testing of a WDM Receiver Henry Yaffe, Principal January 2004

  2. Recommended Test Program • Process • Establish test procedure (automation recommended) • Schedule time in front of systems • Experiments: • Measure bare receiver • Use NRT PMD Source to map to Joint Probability Distribution Function • Analyze data - Calculate Total Outage Probability for different mean span PMDs. • Addendum • If desired, add more impairments (CD, non-linearities) and re-measure www.NewRidgeTech.com

  3. 10-6 BER vs. OSNR Back-to-back 40 ps PMDC 60 ps PMDC Relative OSNR Penalties 80 ps PMDC 60 ps uncompensated 10-12 Back to Back BER Recommended: 10-12 BER as limit (else, each test is too time-consuming) OSNR Test Basis: System Margin (OSNR) as Performance Benchmark www.NewRidgeTech.com

  4. 55/2297 40/2263 70/2051 80/1587 55/1598 75/1488 40/1386 75/1183 20/1183 55/1097 40/894 20/566 40/0 80/0 20/0 60/0 0/0 Recommended Tests to Acquire OSNR Performance for 25 Ps PMD Ex.: 17 states can adequately cover the 25psec (25%) contour www.NewRidgeTech.com

  5. Acquiring the data • Test basis: • Set & maintain all system parameters • Vary OSNR for a given PMD state & measure BER • Characterization process: • Set PMD state • Set OSNR • Set RX power • Record: payload, B3 BERs, error counts, elapsed time, OSNR, and RX power every 30 seconds • Continue recording for >5 min and <30 min (or 10 hits) • Increment OSNR, repeat www.NewRidgeTech.com

  6. 25 km SMF-28 PMDE EDFA Tx Attenuators Polarization scramblers BERT OSA 10 % Tunable 10* 9 11 12 7 6 2 3* 5 8 1 90/10 PMDC* Rx 90/10 Filter 10 % Power meter Test Stand Required for PMD Testing • Automated BER v OSNR at fixed RX power • Allows efficient measurement of many PMD states • Decreases data acquisition time by 3-4x • * Polarization scrambler 3 is not needed if no optical PMDC is used www.NewRidgeTech.com

  7. Test Setup – Equipment Key • Launch Polarization Scrambler – ensures no launch at SOP, which could create artificially high-quality eye • PMDE – controllable PMD source • PMDE Output Polarization Scrambler (optional, only use with 10) – randomly varies SOP to provide “speed” input • Fiber spool – source of “residual” chromatic dispersion (appropriate for chirped systems) • EDFA input attenuator – ASE noise control (OSNR) • EDFA – ASE source • EDFA output attenuator – power control • OSA – OSNR measurement • DWDM Filter – models DWDM effects • PMDC (optional) – compensates for PMD • Power meter – power measurement to maintain constant Rx dBm • BERT – measure BER as performance output www.NewRidgeTech.com

  8. Test Conditions • To establish consistent and verifiable test results • Testing should be conducted PMD as the only impairment • A benchmark system operating level should be set and maintained (Rx power, etc.) • For a given WDM system: • Maintain a constant received power (dBm) level • Turn FEC off (or measure pre-FEC) • Turn SBS Suppression off (if used) • Maintain a fixed (preferably zero, to avoid confusing effects) level of residual chromatic dispersion at the RCVR www.NewRidgeTech.com

  9. Benefits of Automation Can Rapidly Acquire Data to Model Real-world Performance • For network-realistic PMDC characterization: • Reasonable sampling of PMD states is required • Try to define points where DGD & SOPMD performance degrades • Probability of reaching any those states is relevant to system performance • Testing each data point is time-consuming: • Need ~1hr for good statistics at 10-12 BER • Measure for minimum of 5-10 minutes for full SOP coverage • BER v OSNR curves (3-4 points) takes 1 to 2 hours • Automation improves confidence of characterization • Can characterize 10 to 20 PMD states in 24 hours with automation • Compare to ~ 5 to 8 manually per 8 hour shift • OSA, power meter, 2 attenuators, BERT, PMDE are GPIB interfaced • PMD, test time, polling time, OSNRs, and RX powers set by user www.NewRidgeTech.com

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