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

2. www.NewRidgeTech.com2 Recommended Test Program Process  Establish test procedure (automation recommended)  Schedule time in front of systems Experiments: 1. Measure bare receiver 2. 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

3. www.NewRidgeTech.com3 Test Basis: System Margin (OSNR) as Performance Benchmark Back to Back Back-to-back 40 ps PMDC 60 ps PMDC 80 ps PMDC 60 ps uncompensated BER vs. OSNR OSNR BER Relative OSNR Penalties 10 -12 10 -6 Recommended: 10 -12 BER as limit (else, each test is too time-consuming)

4. www.NewRidgeTech.com4 Recommended Tests to Acquire OSNR Performance for 25 Ps PMD 40/2263 20/566 40/0 0/0 60/0 40/1386 20/1183 55/1097 20/0 40/894 55/1598 55/2297 70/2051 75/1183 75/1488 80/1587 80/0 Ex.: 17 states can adequately cover the 25psec (25%) contour DGD (ps) SOPMD (ps 2 ) 00 200 566 1183 400 894 1386 2263 551097 1598 2297 600 702051 751183 1488 800 1587

5. www.NewRidgeTech.com5 Acquiring the data Test basis:  Set & maintain all system parameters  Vary OSNR for a given PMD state & measure BER Characterization process: 1. Set PMD state 2. Set OSNR 3. Set RX power 4. Record: payload, B3 BERs, error counts, elapsed time, OSNR, and RX power every 30 seconds 5. Continue recording for >5 min and <30 min (or 10 hits) 6. Increment OSNR, repeat

6. www.NewRidgeTech.com6 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 Tx EDFA Tunable Filter OSA Power meter 10% % 90/10 Polarization scramblers BERT 90/10 Attenuators 25 km SMF-28 1 2 3*5 67 8 910* 11 12 Rx PMDE PMDC*

7. www.NewRidgeTech.com7 Test Setup – Equipment Key 1.Launch Polarization Scrambler – ensures no launch at SOP, which could create artificially high-quality eye 2.PMDE – controllable PMD source 3.PMDE Output Polarization Scrambler (optional, only use with 10) – randomly varies SOP to provide “speed” input 4.Fiber spool – source of “residual” chromatic dispersion (appropriate for chirped systems) 5.EDFA input attenuator – ASE noise control (OSNR) 6.EDFA – ASE source 7.EDFA output attenuator – power control 8.OSA – OSNR measurement 9.DWDM Filter – models DWDM effects 10.PMDC (optional) – compensates for PMD 11.Power meter – power measurement to maintain constant Rx dBm 12.BERT – measure BER as performance output

8. www.NewRidgeTech.com8 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

9. www.NewRidgeTech.com9 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