Extraction of Brillouin frequency shift from Brillouin gain spectrum in Brillouin distributed fiber sensors using K nearest neighbor algorithm

•BFS extraction technology based on K Nearest Neighbor Algorithm provides a new research idea for BOTDA to extract BFS in low SNRs.•BFS extraction accuracy decreases with the decrease of SNR and the increase of frequency step.•The uncertainty of BFS extraction by KNN can be 0.44 with frequency scanning step of 1MHz and SNR of 11dB.