Mitigating the effects of the gain-dependence of the Brillouin line-shape on dynamic BOTDA sensing methods.

It has been recently shown that in stimulated Brillouin amplification (pulsed pump & CW probe) the line-shape of the normalized logarithmic Brillouin Gain Spectrum (BGS) broadens with increasing gain. Most pronounced for short pump pulses, a linewidth increase of ~3 MHz (~1.5 MHz) per dB of additional gain was observed for a pump pulse width of 15 ns (30 ns), respectively.

Gain dependence of the linewidth of Brillouin amplification in optical fibers.

We report a novel, pump-power dependent, linewidth broadening effect in stimulated Brillouin amplification of a continuous-wave probe by a pulsed pump. This behavior is different from the case of two interacting continuous-wave pump and probe fields, where the shape of the logarithmic Brillouin gain spectrum is independent of the pump power. Studying this effect numerically and experimentally and also analytically, we find that for a given width of the pump pulse the Brillouin linewidth grows linearly with the Brillouin logarithmic gain with a slope, which inversely depends on the pulse width.