In recent years the implementation of Erbium-doped fiber amplifiers allowed to extend high-bit rate transmission to transoceanic distances. But the demand for an increase in transmission capacity is unprecedented and grows continuously. Despite the intrinsically small values of the nonlinear coefficient for silica, the nonlinear effects in optical fibers can be observed even at low powers considering that the light is confined in a relative small area over long (i.e. transoceanic) interaction lengths due to the extremely low attenuation coefficient and the event of optical amplifiers. This is the reason why nonlinear effects can not be ignored when considering light propagation in optical fibers. In the thesis we have studied different ways both to measure the nonlinear coefficient in optical fibers and how to exploit nonlinearities in a useful way in order to build switches or to perform measurements of different optical fibers parameters (e.g. chromatic dispersion, PMD).