We investigate the theory of a nonlinear magneto-optic Fabry-Perot interfer
ometer, filled with an isotropic dielectric that possesses Linear and nonli
near artificial gyrotropy. We show that the nonreciprocity leads to specifi
c multistable transmission patterns and, in particular, to a polarization c
ontrolled multistability at constant input intensity. We also show that the
reciprocity of the cavity can be restored effectively for certain paramete
r regimes. [S0031-9007(99)08486-0].