Enhanced BOTDA Sensors Based on Brillouin Phase Recovery Using Kramers-Kronig Relation

We have proposed and demonstrated an enhanced Brillouin optical time-domain analysis (BOTDA) sensing system with fast measurement speed based on the Brillouin phase recovery using Kramers-Kronig (KK) relation. The non-Lorentz Brillouin gain spectrum (BGS) and Brillouin phase spectrum (BPS) measured by BOTDA are theoretically validated to satisfy KK relation and hence the BPS is digitally recovered by performing Hilbert Transform (HT) to the measured BGS. The recovery of the whole BPS along the 45km fiber only consumes 0.3s. Both simulation and experiment have been carried out to analyze the quality of the recovered BPS under various conditions. By making use of the excellent linearity of the recovered BPS, we accelerate the data processing speed by three times through Linear Fitting (LF) of BPS, without compromise of the sensing accuracy. With implementation of simple HT and LF, this scheme does not need modification of the BOTDA setup and complicated data processing algorithm, which would be a practical way for applications where fast measurement speed is needed, especially in long-distance and high-spatial resolution sensing.