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Double slope-assisted Brillouin optical correlation domain analysis

Fiber-optic Brillouin sensors for temperature and strain distributed monitoring offer unique performance in terms of distance, high spatial resolution and accuracy. Most of the available systems rely on Brillouin Optical Time-Domain Analysis (BOTDA) techniques, which employ pulsed pump signals guaranteeing a spatial resolution fundamentally limited to 1 meter [1]. An attractive alternative approach is the so-called Brillouin Optical Correlation-Domain Analysis (BOCDA), based on the simultaneous phase modulation of both pump and probe waves [2]. In this way, efficient amplification occurs only in a confined fiber section, called correlation peak, where the Brillouin phase-matching condition is satisfied. Correlation peak width can be made arbitrarily narrow and its position along the sensing fiber can be selected by properly tuning the phase modulation rate. Phase-BOCDA sensors can thus guarantee high flexibility in measurement configuration, with spatial resolution that can reach even sub-centimetric scale though at the expense of long acquisition times.