Stimulated Brillouin scattering (SBS) in optical fibers has been studied extensively since the first experimental investigation by Ippen and Stolen. Because of the high SBS gain coefficient and long interaction lengths in optical fibers, it is one of the dominant nonlinear effects to occur. For pulsed lasers this is especially important due to the high peak powers involved. The interaction length is generally taken to be the coherence length (or pulse width for transform limited pulses). It was shown by Fluck et. al. that the SBS threshold for pulses is lower for polarizing fiber We experimentally investigate SBS in polarization-maintaining (PM) fiber with square optical pulses having a duration short compared to the fiber transit time, and show that just above threshold, SBS is generated over the entire length of the fiber. We also show measurements of the SBS threshold for pulse durations short compared to the SBS phonon lifetime (～l6 ns) and show detailed measurements of the pulse distortion on the pulse transmitted through the fiber.
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