  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.
