1. Interchannel Nonlinearities in Polarization-Multiplexed Transmission Marcus Winter Klaus Petermann Hochfrequenztechnik-Photonik TECHNISCHE UNIVERSITÄT BERLIN Dario Setti http://www.marcuswinter.de/publications/ecoc2009

2. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 cross-phase modulation (XPM) and cross-polarization modulation (XPolM)

3. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 XPolM is similar to XPM nonlinear variation of the birefringencerefractive index proportional to sum of interfering channel Stokes vectorspowers results in the modulation of signal polarizationphase

4. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 XPolM – where and what?

5. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 systems with large XPM impairment are affected (e.g. selective 10G 40G/100G upgrades) fully polarized signal becomes depolarized

6. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 depolarization can be visualized on the Poincaré sphere quantified by nonlinear DOP reduction XPolM model exists to predict this magnitude* * Winter et al., JLT 17 (27), p. 3739, 2009.

7. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 impairments in PolDM systems

8. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 single-polarization Tx is replaced by PolDM Tx Rx signal processing can follow PMD changes, but not XPolM

9. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 Rx polarization misalignment generates crosstalk between PolDM subchannels statistically, crosstalk depends only on the degree of polarization and the source amplitude

10. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 interleaving RZ-shaped symbols minimizes crosstalk amplitude at target sampling instant even with interleaving, the crosstalk is never zero, but significantly smaller due to signal distortions, noise, etc.

11. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 system simulations

12. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 nonlinear threshold of the NRZ interferers is reduced by 2dB due to XPolM (1dB when interleaving is used) 10 × 10G NRZ interferers w/ 25Gbaud PolDM-RZ-QPSK probe

13. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 mean values individual distribution

14. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 ROSNR penalties at 4 dBm NRZ power (mean DOP = 0.961)

15. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 ROSNR penalties at 3 dBm NRZ power (mean DOP = 0.975)

16. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 ROSNR penalties at 2 dBm NRZ power (mean DOP = 0.984) at 2 dBm, fluctuations become comparable to XPM-related spread at 4 dBm (3 dBm when interleaving is used)

17. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 summary

18. TECHNISCHE UNIVERSITÄT BERLIN ECOC 2009 – Tu.10.3.4 XPolM-induced depolarization leads to crosstalk between PolDM subchannels interleaving the subchannels can significantly reduce the crosstalk penalty (but not eliminate it) the mean nonlinear DOP reduction for 25 Gbaud PolDM- RZ-QPSK should not exceed 0.98 the resulting 10G NRZ interferer NLT penalty is up to 2 dB over XPM alone