Comparison of stimulated Brillouin scattering thresholds and spectra in nonpolarization-maintaining and polarization-maintaining passive fibers

Abstract

Stimulated Brillouin Scattering (SBS) is a polarization-dependent, nonlinear process that is often the limiting factor for high-power fiber laser applications. We report the results of experiments measuring the SBS thresholds and the SBS gain bandwidths in several passive optical fibers. Fibers with nearly identical mode-field diameters and loss coefficients from different manufacturers were selected. Observations from these experiments indicate that the SBS gain coefficient for fibers from different manufacturers varied significantly resulting in a 70% deviation in SBS threshold. Also, polarization-maintaining (PM) fiber exhibited a significant increase in the SBS threshold for a linearly polarized pump beam that is launched into the PM fiber at 45° relative to the fiber's slow axis. This increase in threshold was not mirrored in non-PM fiber. These results suggest that the polarization multiplier in the SBS threshold equation may be highest when a PM fiber is used with the appropriate launch conditions, rather than a non-PM conventional single-mode fiber. We will present the experimental results and a theoretical model demonstrating the polarization dependent gain properties in both PM and non-PM fiber.