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Performance of CULP-CDMA Receivers Based on Four Wave Mixers

Noshad, Mohammad | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39909 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Salehi, Javad
  7. Abstract:
  8. In this thesis the performance of the all optical AND gates, based the Four Wave Mixing process (FWM), for application in optical communication and computing systems, has been investigated. In the performance analysis of these AND gates, we mainly focus on its application in the receivers of the Optical Code Division Multiple Access (OCDMA) systems. For analyzing the performance of these receivers we utilize the existing mathematical model for FWM [1-5], which leads to the nonlinear Schrodinger (NLS) coupled equations. The attenuation, chromatic dispersion and Raman scattering effects have been taken into account in this model and the scalar approximation, for approximating the relation between the electrical field and polarization, has been used for mathematical simplicity. Using the FWM model (by neglecting the chromatic dispersion and Raman scattering) we drive the spectral domain auto-correlation function of the mixer’s output signal and then, using this function, we calculate the mean and variance of the photo-detector’s output current. In evaluating the performance of the receiver, we neglect the attenuation and dispersion effects in the optical network and also the shot, beat and thermal noises at the receiver, and only consider Multiple-Access Interference (MAI) and FWM noise in our calculations. For calculating the bit error probability we use Gaussian approximation for the probability density function (pdf) of the output current and then plot the BER in terms of the active users number for different pump powers. We also plot the SNR in terms of the normalized pump bandwidth in order to get the optimum bandwidth for maximizing the SNR and then analyze the results.

  9. Keywords:
  10. Volterra Series ; Autocorrelation Function ; Bit Error Rate ; Optical Code Division Multiple Access (OCDMA) ; Four Wave Mixing ; Schrodinger Nonlinear Equations

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