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Thesis Defense : Pierre Walczak

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Nonlinear propagation of partially coherent waves in optical fibers

January 12, 2016 — 13h30 — Amphi Glorieux (CERLA)


This thesis deals with nonlinear propagation of partially coherent waves in optical fibers. We focus our attention on systems of random waves that are well described by the integrable one dimensional nonlinear Schrödinger equation. We study both experimentally and numerically the statistical evolution of power fluctuations of random waves both in normal and in anomalous dispersion regimes.

In order to measure statistics of the power fluctuations of partially coherent optical waves with typical time scales in the range of picosecond, we have performed an asynchronous optical sampling method. Our experiments show that nonlinear propagation strongly influences the statistics of wave systems by producing deviations from the normal distribution. The probability of occurrence of extreme events is significantly enhanced in the focusing regime whereas it is strongly reduced in the defocucing regime. Our numerical simulations of the one-dimensional nonlinear Schrödinger equation reproduce experimental results in a quantitative way. Moreover, our results provide evidence of the emergence of coherent structures embedded in the random fluctuations. In the focusing regime, we observe coherent structures similar to solitons on finite background that are now considered as prototypes of rogue waves.

From our work about nonlinear propagation of random waves in systems described by nearly-integrable equations, we hope to contribute to the development of the field of ntegrable turbulence.

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