Nonlinear Fiber Optics: Pulse Compression and Dark Solitons
This dissertation is concerned with two aspects of the nonlinear optics in fibers. One aspect regards ultrashort (pulse width <50 fs) pulse compression and the other optical dark solitons. We examine the effects of higher-order dispersion and nonlinearity on pulse compression in a medium with "normal" group velocity dispersion. We numerically simulate pulse propagation in optical fibers under the influence of both effects, for the first time. According to these results, these additional terms are particularly responsible for the spectral asymmetry and cubic phase (nonlinear frequency chirp) in the output spectrum of the fiber. By including the possible asymmetry of the input pulse, our results agree well with experimentally obtained spectra. A Gires -Tournois interferometer is designed to compensate for cubic phase compensation. The validity of Taylor series expansion up to the fourth-order of fiber dispersion is shown to be accurate for pulse durations longer than 10 fs at moderate input power levels. We also numerically study propagation properties of fundamental and higher-order dark solitons. A comparison of the stabilities against small perturbations such as fiber loss, background noise, and mutual interactions of dark solitons to that of their bright soliton counterparts is made. We find that dark solitons possess higher stabilities against these perturbations. Dark soliton evolution under constant gain is also investigated. The possibility of loss compensation by Raman amplification is demonstrated. Even dark solitons are investigated. Finally, we propose a novel method for generating dark solitons with constant background by modulating a waveguide Mach-Zehnder interferometer.
- Pub Date:
- Engineering: Electronics and Electrical; Physics: Optics