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

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. Outline. Kerr nonlinearity induced phase noise in coherent communication systems

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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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