  We report the observation of different localized structures coexisting for
the same parameter values in an extended system. The experimental findings are
carried out in a nonlinear optical interferometer, and are fully confirmed by
numerical simulations. The existence of each kind of localized structure is put
in relation to a corresponding delocalized pattern observed. Quantitative
evaluation of the range of pump parameter allowing bistability between
localized structures is given. The dependence of the phenomena on the other
relevant parameters is discussed.
