Vector modulational instability induced by parametric resonance in periodically tapered highly birefringent optical fibers

We study the modulational instability induced by periodic variations of group-velocity dispersion and nonlinear coefficients in a highly birefringent fiber. We observe, for each resonance order, the presence of two pairs of genuine vector-type sidebands, which are spectrally unbalanced between the polarization components for nonzero group-index mismatch, and one pair of balanced sidebands emerging and dominating at increasing group-index mismatch. As the conventional modulational instabilitymanifests itself, it is partially suppressed by the proximity of these additional unstable regions.