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Interaction of Nonlinear pulses for Nondestructive Characterization of the Highly Nonlinear Fiber

Alishahi, Fatemeh | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 50078 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Mehrani, Khashayar
  7. Abstract:
  8. In this thesis, while a comprehensive study of different methods for the characterization of the optical fibers is done, a unique and effective method is being introduced for the characterization of the dispersion coefficient of Highly Nonlinear Fibers (HNLFs). The proposed method is based on the Brillouin Optical Time Domain Analysis (BOTDA) of a wave generated by the Four Wave Mixing (FWM) interaction. The current method, which includes an experimental scheme and an algorithm for solving the inverse problem, offers high sensitivity and experimental accuracy at the longitudinal resolution of 1 meter. The noise level has been considerably reduced by understanding different sources of the experimental noise. As a result the experimental accuracy is fairly close to the numerical accuracy. Furthermore, the BOTDA scheme has been effectively modified to fit with the characterization purposes and prevent Brillouin pump depletion. Also, for the proposed scheme the problematic issues cuased by the unwanted polarization rotation and non-scalar interactions along the fiber, have been fairly circumvented. High sensitivity of the scheme is achieved by placing the signal of four wave mixing at the edge of instability modulation spectrum of a high power pump in both phase sensitive and phase insensitive shemes. For the phase insensitive scheme, the spectrum variations which is due to the dispersion coefficient variations results in the high sensitivity to the diserson coefficient. On the other hand, in the phase sensitive scheme, the richer dynamics of the phase sensitive amplification further assists the former cause of sensitivity. Furthermore, the algorithm for solving inverse problem has to inevitably deal with spurious solutions. In the proposed method, certain provisions have been made to avoid such solutions
  9. Keywords:
  10. Highly Nonlinear Fiber ; Four Wave Mixing ; Ultrashort Light Pulses ; Dispersion Coefficient ; Brillouin Optical Time Domain Analysis ; Brillouin Backscuttering

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