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Intra-channel Four Wave Mixing (IFWM) induced phase noise in Coherent Communication Systems

Explore the impact of Intra-channel Four Wave Mixing (IFWM) induced phase noise on coherent communication systems. Discuss Kerr nonlinearity, IFWM statistics, and phase noise reduction techniques. Investigate correlation structure and future work analysis.

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Intra-channel Four Wave Mixing (IFWM) induced phase noise in Coherent Communication Systems

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  1. Intra-channel Four Wave Mixing (IFWM) induced phase noise in Coherent Communication Systems Alan Pak Tao Lau Department of Electrical Engineering, Stanford University June 6, 2007

  2. Outline • Kerr nonlinearity induced phase noise in coherent communication systems • Statistics of IFWM phase noise • Phase noise reduction through exploiting correlation of IFWM • Conclusions/Future work

  3. Kerr Nonlinearity • induced intensity dependent refractive index • Self phase modulation induced Nonlinear Phase Shift • Nonlinear Phase Noise when random

  4. Phase noise in coherent communication systems • Laser phase noise • Laser linewidth • Carrier recovery mechanisms • Linear phase noise • ASE noise from inline amplifiers • Nonlinear phase noise • Phase fluctuations from randomness of data • Interaction of ASE noise and signal with Kerr nonlinearity – Gordon-Mollenauer effect • Shot noise / Thermal noise

  5. Signal propagation in optical fibers • Pulse trains • Nonlinear Schordinger Equation (NLSE) • Perturbation Linear solution to NLSE • SPM on : • IXPM on : • IFWM on :

  6. IFWM phase noise • IFWM induced phase noise on bit 0 • IFWM technically information, but hard to fully exploit

  7. What we know about • arecorrelated Wei and Liu, Optics Lett., Vol. 28, Issue 23, pp. 2300-2302 Ho, PTL vol. 17, no. 4, Apr. 2005, pp. 789-791 • No analytical knowledge of pmf, correlation, variance • Basically, know nothing about IFWM phase noise!

  8. Variance for QPSK systems

  9. Correlation

  10. for 40GSym/s QPSK systems • 33% RZ Gaussian pulses Sampling points SMF DCF DCM

  11. SMF SMF DCF DCF DCM DCM overall length Ltot with N spans

  12. pmf of • No analytical knowledge of pmf • Error probability for PSK/DPSK system with IFWM and receiver phase noise • Is it possible to at least approximate ?

  13. Approximate pmf • Insight: terms in are pairwise independent • Only a consequence of module addition in phase of

  14. for QPSK/DQPSK systems DQPSK QPSK • DQPSK: Group terms from that are correlated with each other

  15. Tail Probability IFWM Rec. QPSK DQPSK

  16. Exploiting • Optimal linear prediction of • 1.8 dB improvement when dominates • 0.8-1 dB improvement in presence of ASE noise

  17. Exploiting • Decorrelate through whitening filter • ISI channel. Can apply MLSD if are assumed to be independent • Approximate the pmf of

  18. Comparison of phase noises

  19. Conclusions/Future Work • Analyzed the correlation structure of IFWM induced phase noise • Approximate pmf of in PSK/DPSK systems • System performance improvement by exploiting correlation structure of through optimal linear prediction • MLSD Acknowledgements • Sahand Rabbani • Prof. Kahn

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