Advancing Test in Coherent Transmission Systems. Daniel van der Weide

Transcription

1 Advancing Test in Coherent Transmission Systems Daniel van der Weide 1

2 Otametra History Comlex Measurements Made Simle First 10 Systems Sold January 2011 Acquired by Tektronix -- July 2011 Founded Set 2007 CSLA 40G Product Launched March 2009 (OFC/NFOEC) CSLA 100G Product Launched Setember Set W

3 What does a Coherent Lightwave Signal Analyzer do? Enables total calibration to make hardware golden Analog front end ath gains, hase angles Frequency resonse Path delays (skew) Removes laser frequency offset Removes laser hase fluctuations Presents resulting modulation field Constellation Eye Diagram Q lot EM Can also model receiver function and even imairments Remove CD, ISI, etc.; measure BER Emulate a delay-line interferometer for differential signaling 3 Set W

4 Coherent Lightwave Signal Analyzer Architecture otical signal LO hotodetectors hase/ olarization diversity hybrid (all assive) A/D converters RAM rocessor dislay The otical signal analyzer uses burst-mode coherent detection it includes a local oscillator laser and a hase/olarization diverse hybrid Oututs from several hotodetectors are digitized by high seed (e.g. 50 Gs/s) A/D converters for an interval of time and stored in RAM A microrocessor asynchronously reads the values from RAM and comutes the required arameters of the signal All the information about the signal over the interval of time is known electric field (in-hase & quadrature arts) in both olarization states In rincile any signal arameter can be deduced by an aroriate algorithm 4 Set W

5 OM4000 Otical Modulation Analyzer Series Comlete and oen solutions to comlex measurement challenges in long-haul fiber-otic communications Advanced dual-olarization in-hase and quadrature receiver with integrated signal and reference tunable laser sources Oen-architecture MATLAB-based comutational engine offers owerful hase-recovery analyses with olarization, bit-error rates, and record/layback Grahical user interface controls frequently-used instrument functions: Laser control Modulation schemes PRBS or user-generated data Works with all major real-time oscilloscoes Easily ugradable 5 Set W

6 Why do I need a Coherent Lightwave Signal Analyzer? Understand and otimize otical networks emloying advanced modulation Measure constellation arameters, quadrature and modulator bias values, symbol masks, EM, signal and hase sectra, BER, Q vs. decision threshold Save time, enable a wider range of users Transition from R&D to qualification and roduction environments Enable automation Test equalization and hase recovery algorithms CD, PMD, ISI Understand effects of bandwidth limitations At the transmitter, digitizer, and receiver 6 Set W

7 Measuring TX Constellation Imerfections: EM Im Re Distance of a symbol oint from the ideal location. Instantaneous or rms value Normalized to ideal symbol magnitude QAM EM often normalized to largest symbol magnitude 7 Set W

8 Measuring TX Constellation Imerfections: Q-factor Im Counts errors as decision threshold is moved. Errors fitted to error function in Q-sace Re Plot, max-q and otimum decision threshold 8 Set W

9 Measuring TX Constellation Imerfections: Phase Angle Im Re 9 Set W

10 Examle: Modulator Bias Adjustment 10 Set W

11 Examle: Adjusting Tributary Timing Skew 11 Set W

12 Measurements Available for QPSK Signals 12 Set W

13 Measurements Available for QAM Signals 13 Set W

14 20 G RZ DQPSK 14 Set W

15 One DC Module being Comensated. CD = 900 s/nm 15 Set W

16 2 CD Modules CD = 1700 s/nm 16 Set W

17 Data Acquisition and Processing Flow Acquire Data Filtering (cable comensation) Acquisition and Dislay Loo Pre-rocessing (e.g.cd and PMD comensation can be done) Core Processing (hase and clock recovery, olarization resolution, resamling) Dislay Formatted Data 17 Set W

18 Interaction Between GUI and MATLAB GUI Write Analysis Parameters to MATLAB Worksace Acquire Scoe Record Write Record to MATLAB Worksace MATLAB Clock Recovery Polarization Estimation Phase Estimation Ambiguity Resolution 2nd Phase Estimate Count Bit Errors Calculate Constellation Parameters GUI Plot Results Eyes, Constellation Diagrams, Poincaré Shere Reort Bit Errors Reort Q-factors, Constellation Parameters block SigTye, FreqWindow, etc. Matlab worksace zxsym, zysym, zx, zy, DecTh, etc. 18 Set W

19 Flow Diagram (single ol case) scoe samle rate symbol rate ClockRetime AlyPhase AlyPhase symbol center E-field scoe record EstimateClock EstimateSOP EstimatePhase AlignTribs EstimatePhase count bit errors Q-factor const arams continuous E-field ClockRetime scoe samle rate N x symbol rate AlyPhase 19 Set W

20 Otametra Product Family OM4000 Otical Modulation Analyzer Series OM1106 Signal Analysis Software Otional hardware suort OM1206 Signal Analysis Test Set Software ortion of the OM4106 Includes tools for customer hybrid receiver calibration/ test OM2010 Tunable Laser Source Provides additional laser sources 20 Set W

21 Coherent Receiver Imairments Bandwidth Grou delay variation I-Q Crosstalk (hybrid hase angle error) CMRR Polarization crosstalk Channel gain imbalance Channel delay mismatch RF mismatch effect on grou delay Frequency-domain crosstalk Nonlinearity 21 Set W

22 Coherent Receiver Testing Relace inut signals with reference signals Relace ADC with real-time oscilloscoe New OIF Agreement IA OIF Test overall: Path gains Cross talk Phase angles At any frequency or wavelength 22 Set W

23 Measured Relative Gain (db) Sources of Polarization Crosstalk LO Y Resulting LO Moves with l and Tem LO X W W 1/ ER 5 Imerfect LO Laser Extinction Imerfect Key or Slice Alignment PM-fiber-induced Rotation Finite PBS Extinction Ratio 0-5 Gain 1-2 Gain 3-4 Gain 1-3 Gain Laser Frequency (THz) 23 Set W

24 Effect of ol-crosstalk on Phase Angle Im E X Im E X E Y ER S ER LO Re X-Inhase Outut X-Quadrature Outut Aarent E x is modified by E Y leakage 20 db + 20dB: ± db +15dB: ±3.6 E X Re Effect scales u if E Y larger than E x EX E Y ER S ER LO 24 Set W

25 Simle Hybrid Receiver Reresentation E S E LO [a] [b] [c] [d] [e] [f] [g] [h] E S H E E E E Syi Syr Sxi Sxr S S LO E E a E b R 1 * 1 1 Syi Syr Sxi Sxr y y x x y y x x y y x x y y x x E E E E Im Re Im Re Im Re Im Re Im Re Im Re Im Re Im Re 25 Set W

26 Otical Hybrid Calibration h h h h HE h h h h h h h h E H h h h h E E E E xr xi yr yi Aly Ex or Ey, measure hase angle Or How to set Ex? Ey? What about crosstalk effect on angle? Aly E1 and E2, find all hybrid arameters E1 E2 = 0 (new coordinate system) Rotate back to hybrid system Entire H is needed to find H-1 This gives full imact of finding E given 26 Set W

27 Measured Quadrature Phase Error Gain, Crosstalk (db) Hybrid Phase Angle, Gain, and Crosstalk Excites RX under test with heterodyne signal Two orthogonal olarizations Comuter takes data from scoe and calculates hybrid arameters 5 Tunable laser ermits full-band testing Comuter Sig LO RX under test f1 f Signal Frequency (THz) 5 Phase deg Phase deg Laser Frequency (THz) 27 Set W

28 Controller Laser 1 Laser 2 Receiver Testing Detail OM4106B Polarization Switch Slitter USB Otical Power Meter LO Polarization diverse Coherent front-end Real-time Oscilloscoe Signal RX under test Comuter 28 Set W

29 Controller Controller Laser 1 Controller Laser 1 Laser 2 Calibration Kit Otions Polarization Switch OM4106B/ OM3105B-603 C-band Calibration Source and Software. Includes 2 lasers. Use this otion when C-band receiver has no Otametra sources. OM4106B/ OM3105B-604 L-band Calibration Source and Software. Includes 2 lasers. Use this otion when L-band receiver has no Otametra sources. Polarization Switch OM4106B/ OM3105B-601 C-band Calibration Source and Software. Includes 1 laser. Use this otion when C-band receiver has an Otametra Reference Laser. OM4106B/ OM3105B-602 L-band Calibration Source and Software. Includes 1 laser Use this otion when L-band receiver has an Otametra Reference Laser. Polarization Switch OM4106B/ OM3105B-600 Calibration Source and Software. Includes no lasers. Use this otion when receiver has 2 Otametra sources for Reference and Signal. Kit also includes otical ower slitter and USB otical ower meter not shown. A real time samling scoe is required for calibration (not rovided). 29 Set W

30 Controller L-Laser C-Laser Controller L-Laser C-Laser C+L Calibration Kit Polarizatio n Switch OM4106B/ OM3105B-605 C or L-band Calibration Source and Software. Includes 2 lasers combined to make a C+L source. Use this otion when receiver has a similar Otametra C+L Reference. Tyical Coherent Receiver Calibration test set u (below). Comuter and Real-time oscilloscoe are not art of the kit. Receiver urchased searately. C+L Slitter USB Otical Power Meter C+L Otical hybrid RX RX Real-time Oscilloscoe RX under test Comuter 30 Set W

31 Conclusions Coherent Lightwave Signal Analyzers can quantify quality of transmitter signal Otametra also offers tools for receiver characterization Heterodyne analysis can be used to extract a simle hybrid matrix describing the analog receiver front end Measuring integrated receiver roerties allows inclusion of otical and electrical cross-talk effects 31 Set W