Abstract
We propose a novel method to improve the spatial resolution of Brillouin optical time-domain reflectometry (BOTDR), referred to as synthetic BOTDR (S-BOTDR), and experimentally verify the resolution improvements. Due to the uncertainty relation between position and frequency, the spatial resolution of a conventional BOTDR system has been limited to about one meter. In S-BOTDR, a synthetic spectrum is obtained by combining four Brillouin spectrums measured with different composite pump lights and different composite low-pass filters. We mathematically show that the resolution limit, in principle, for conventional BOTDR can be surpassed by S-BOTDR and experimentally prove that S-BOTDR attained a 10-cm spatial resolution. To the best of our knowledge, this has never been achieved or reported.
Highlights
The spectrum of Brillouin scattering in optical fiber shifts in proportion to changes in the strain and temperature of the fiber
Since Brillouin optical time-domain reflectometry (BOTDR) uses only one end of a fiber, it is suitable for long distance measurement, whereas Brillouin optical time-domain analysis (BOTDA) uses pump and probe lights that are injected from both ends of a fiber
We mathematically show that the resolution limit in principle for conventional BOTDR could be overcome by synthetic BOTDR (S-BOTDR) and experimentally prove that 10-cm spatial resolution, which is much smaller than the conventional BOTDR limit, is attained by S-BOTDR
Summary
The spectrum of Brillouin scattering in optical fiber shifts in proportion to changes in the strain and temperature of the fiber. To improve the spatial resolution of both techniques, it is necessary to narrow the pulse; the linewidth of the observed spectrum becomes wider and makes measurement of the spectral shift difficult. The authors of [12,13,14] proposed methods to suppress or cancel the undesired part of the spectrum by combining two different measurements By these methods, high-resolution measurement of centimeter-order for BOTDA has been attained. We propose a novel method, referred to as synthetic BOTDR (S-BOTDR), to improve the spatial resolution of BOTDR In this method, a synthetic Brillouin spectrum is constructed by combining several spectrums obtained by BOTDR measurements with different pump lights and low-pass filters.
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