  The nonlinear stage of modulational instability in optical fibers induced by
a wide and easily accessible class of localized perturbations is studied using
the nonlinear Schrodinger equation. It is showed that the development of
associated spatio-temporal patterns is strongly affected by the shape and the
parameters of the perturbation. Different scenarios are presented that involve
an auto-modulation developing in a characteristic wedge, possibly coexisting
with breathers which lie inside or outside the wedge.
