1. Four Wave Mixing (FWM) Spring 2004 EE290F Xiaoxue Zhao

2. Contents Origin of FWM Effect on WDM systems Solutions  Polarization Allocation  Unequal Channel Spacing  Dispersion Management

3. Origin of FWM [1] Third order nonlinearity Energy Conservation Momentum Conservation—phase matching

4. Origin of FWM—Phase Matching [2]

5. Effects on WDM Systems [2] Channel spacing and fiber dispersion are small enough

6. Effects on WDM Systems [3] Nonlinear Crosstalk equally spacing, product terms fall at channel frequency Coherent interference

7. Effects on WDM Systems [4] Bit pattern Power Depletion

8. Effects on WDM Systems—Solutions Polarization Allocation Unequal spacing Dispersion management

9. Polarization Allocation [5]

11. Add polarization filter at the receiver end

12. Unequal Channel Spacing [6]

14. Dispersion-Management [4] No dispersion-zero point Total accumulated dispersion near zero

15. Dispersion Management [7] Dispersion map for dispersion- compensating fiber (DCF) Small core area

16. New Type of Fibers Large effective area fiber Nonzero dispersion shifted fiber (NZ-DSF) http://www.corning.com/opticalfiber/products__services/reprints/r1083.asp large-effective-area fiber (red) suppressed four-wave mixing crosstalk to -22.5 dB, compared to -19.0 dB for NZ-DSF fiber (blue).

17. References  [1] G.Agrawal “Nonlinear Fiber Optics”, 3rd edition  [2] G Agrawal “Fiber-Optics Communication Systems” 3rd edition  [3] Nori Sibata, Ralf Braun and Robert Waarts, IEEE J. Quantum Electron. QE23, 1205, 1987  [4] Ivan Kaminow and Thomas Koch, OFT IIIA  [5] C. Mahon, L. Olofsson, E. Bodtker, G. Jacobsen, IEEE Photon. Tech. Lett. 8,575, 1996  [6] F. Forghieri, R. Tkach, A. Chroplyvy, J. Lightwave Tech, 13, 889 1995  [7] R. Tkach, R. Derosier and et. al, IEEE Photon. Tech. Lett. 7, 1369, 1995