Abstract
Slope-assisted Brillouin optical time domain analysis (SA-BOTDA) is
a fast and distributed sensing technique that interrogates the Brillouin
gain spectrum (BGS) near the middle of the linear region of its slope,
allowing the measurement of high frequency vibrations. However,
environmentally-induced deviations of the interrogation point from the
rather small linear region around the optimum frequency position, result
in harmonic distortion and changes in the slope value, which determines
the gain-to-frequency conversion factor. Engineering the BGS by adding a
loss probe, we propose a novel and improved version of SA-BOTDA, having a
significantly wider drift tolerance for the interrogation point. Here,
using a 14 ns pump pulse and a judicious choice of the frequency of the
loss probe, we demonstrate an engineered BGS having a 70% wider frequency
range (as compared with the conventional BGS), where the interrogation
point can drift without compromising either the prescribed level of
harmonic distortion or the given slope tolerance, further benefiting the
flexibility and usage of SA-BOTDA.
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