POLARIZATION MODULATION INSTABILITY IN WEAKLY BIREFRINGENT FIBERS

Modulation instability generated by the coherent interaction of two po larization modes in a weakly birefringent optical fiber has been obser ved in the normal dispersion regime. In contrast to previous observati ons of cross-phase-modulation instability in the visible, the two gene rated sidebands have the same polarization, which is orthogonal to tha t of the pump, and their frequency shift is readily controlled by vari ation of the birefringence of the fiber. The frequency of the modulati on and its qualitative features agree with those theoretically predict ed.