The resonant behaviour of the Faraday rotation in a medium with linear   birefringence
  It is shown that the monochromatic optical wave propagating through the medium with linear birefringence in presence of a signal electromagnetic wave (whose wavelength is equal to the polarization beats length), displays Faraday rotation having the frequency of the signal wave and unsuppressed by linear birefringence. The effect is resonant with respect to the frequency of a signal wave. The "sharpness" of the resonance is defined by length of the birefringent medium. 
G.G.Kozlov