Polarization switching and suppression of stimulated Raman scattering in birefringent optical fibers

We analyze stimulated Raman scattering in normally dispersive highly birefringent fibers under dual-frequency, orthogonal polarization pumping. Experiments show that stimulated Raman scattering can be suppressed in anyone of the fiber axes by two distinct processes prevailing at large and small group-velocity mismatches (GVM's), respectively, between the pumps. For a relatively large GVM, parametric four-wave mixing is the dominant process for the suppression of Raman-Stokes radiation. On the other hand, for a small GVM, the Raman-Stokes light is suppressed along the polarization direction of the highest-frequency pump, through a mechanism associated with the orthogonal component of the Raman gain. The sign of the GVM between the pumps allows for selecting the particular fiber axis where suppression of the Raman-Stokes radiation is desired. This selection is achieved by simply tuning the frequency spacing between the pumps. (C) 1998 Optical Society of America [S0740-3224(98)02005-0].