Polarization effects in short- and long-period fibre gratings:: a generalized approach

Short- and long-period fibre gratings with linear birefringence and/or rotational effects are studied by using a generalized coupled mode theory which, in a truncated form, is a very good approximation as long as the periodic perturbation is small. This generalized theory made possible the study of the contra-directional and co-directional couplings in an isotropic optical fibre with an isotropic periodic perturbation, in an anisotropic optical fibre with a periodic perturbation and in a fibre with an anisotropic periodic perturbation. That is to say, of short- and long-period fibre gratings with linear birefringence and rotational effects, also in the most general case in which the periodic perturbation is optically anisotropic.