Magnetooptical properties of index-gradient optical fibers

The magnetooptical Faraday rotation of a guided He-Ne laser beam in index-gradient fibers was measured. The proportionality between the rotation of the polarization vector and the length of the light path in an applied homogeneous longitudinal magnetic field is disturbed. The measuring results can be explained by means of a theoretical model combining the Faraday effect with birefringence.