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Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems Cross-Polarization Modulation in Polarization-Multiplexed Systems M. Winter, D. Kroushkov,

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Presentation on theme: "Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems Cross-Polarization Modulation in Polarization-Multiplexed Systems M. Winter, D. Kroushkov,"— Presentation transcript:

1 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems Cross-Polarization Modulation in Polarization-Multiplexed Systems M. Winter, D. Kroushkov, and K. Petermann IEEE Summer Topicals July 2010

2 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 2 typical DWDM system with a nonlinearity probe ► CW probe is unaffected by linear effects / SPM ► other channels are 10 Gbps OOK in 50 GHz grid

3 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 3 SOP evolution Tx output (fully polarized)

4 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems SOP evolution (without amplifier noise) 4 significant nonlinear depolarization rapid (symbol-to-symbol) fluctuations of the SOP what is going on and is this a problem?

5 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 5 cross-polarization modulation (XPolM) ► basics ► statistical models ► XPolM and polarization multiplex ► experiments

6 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems XPolM basics 6

7 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 7 XPolM is closely related to XPM nonlinear variation of the birefringence (index difference between x and y) refractive index proportional to sum of interfering channels‘ Stokes vectorspowers results in the modulation of signal polarization (phase difference between x and y) phase

8 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems nonlinear polarization effects known since at least 1969 ► e.g. Kerr shutter (Duguay and Hansen, APL, pp. 192+, 1969) XPolM first described in its „current version“ in 1995 ► Stokes space Manakov equation ► collision of two solitons ► Mollenauer et al., Optics Letters, pp , 1995 many-channel formulation in 2006 ► Menyuk and Marks, JLT, pp ,

9 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 9 Poincaré sphere probe channel DWDM interferers Stokes vector sum nonlinear rotation

10 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems statistical models 10

11 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems (interferer) Stokes vectors are not constant 11 ► length (intensity) varies due to walk-off ► (interferer and probe group velocity differs) ► direction (SOP) varies due to PMD ► (interferer and probe birefringence differs) ► both effects are random various models have been proposed to describe this behavior

12 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems ► carousel model (Bononi et al., JLT, pp , 2003) ► pump and probe rotate when both carry a mark ► two-channel system, no PMD 12 ► diffusion model (Winter et al., JLT, pp , 2009) ► SOPs evolve as random walk ► ensemble mean values only ► Karlsson‘s statistical model (JLT, pp , 2006) ► influence on PMD compensation ► mostly two-channel system, no PMD dependence

13 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems SOP distribution resembles diffusion 13

14 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems DWDM power/channel threshold for mean probe DOP=0.97 ► resonant dispersion map, 10 × 10 Gbps OOK interferers 50 GHz spacing 14

15 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 15 depolarization of probe vs. number of 3 dBm interferers ► difficult to simulate, expensive to measure ► saturates at about 20

16 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems XPolM and polarization multiplex 16

17 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 17 ► selective upgrade: 10G NRZ » 100G PolDM RZ-QPSK ► fits into 50 GHz grid a typical PolDM system

18 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems polarization DEMUX must be aligned to PolDM subchannels (visualization in Jones space) 18 ► otherwise crosstalk occurs from x to y and vice versa ► crosstalk increases with misalignment angle and with ► length of field vector detected field at y-Rx:

19 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems modern coherent receivers can handle subchannel SOP changes with PMD time constants ► DCF abuse with a screwdriver: 280 µrad/ns (Krummrich and Kotten, OFC 2004, FI3) 19 XPolM causes symbol-to-symbol fluctuations around mean SOP ► cannot be compensated (again like XPM)

20 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems interleaving RZ-shaped symbols minimizes crosstalk generation 20 time field amplitude at y-Rx aligned subchannels interleaved subchannels ► crosstalk is never zero because pulses at Rx are no longer RZ (accumulated GVD, PMD, noise)

21 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems × 10G NRZ interferers w/ 100G PolDM-RZ-QPSK probe ► 256 ps/nm RDPS, 10 interferers, SSMF, no PMD ► power/channel threshold is reduced by up to 2 dB

22 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 22 the statistical ensemble (mean DOP = 0.975) ► DOPs and ROSNRs spread over large range ► for DOPs < 0.98 (0.97), ROSNR penalties become significant

23 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems Xie showed how PolDM interferers can cause negligible XPolM compared to single-polarization (PTL, pp. 274+, 2009) ► requires RZ pulse shape and subchannel interleaving ► neighboring half-symbol slots have orthogonal polarization states ► probe SOP oscillates but rotation does not accumulate 23

24 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems experiments 24

25 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 25 ► onset of nonlinear penalties at much lower powers ► (near) saturation of penalties for large channel spacing (van den Borne et al., ECOC, 2004, Mo 4.5.5)

26 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 26 ► saturation of penalties for large number of interferers (Renaudier et al., PTL, pp , 2009)

27 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 27 ► benefit of PolDM vs. OOK interferers (Bertran-Pardo et al., OFC, 2008, OTuM5)

28 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems summary 28

29 Marcus Winter: XPolM in Polarization-Multiplex Transmission Systems 29 ► XPolM in DWDM systems causes depolarization ► diffusion model correctly predicts simulated behavior ► depolarization creates detrimental PolDM crosstalk ► can be reduced by interleaving PolDM subchannels slides available at


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