Long-range chaotic Brillouin optical correlation domain analysis with more than one million resolving points

We propose and experimentally demonstrate a long-range chaotic Brillouin optical correlation domain analysis by employing an optimized time-gated scheme and differential denoising configuration,where the number of effective resolving points largely increases to more than one million.The deterioration of the chaotic Brillouin gain spectrum(BGS)and limitation of sensing range owing to the intrinsic noise structure,resulting from the time delay signature(TDS)and nonzero background of chaotic laser,is theoretically analyzed.The optimized time-gated scheme with a higher extinction ratio is used to eliminate the TDS-induced impact.The signal-to-background ratio of the measured BGS is enhanced by the differential denoising scheme to furthest remove the accumulated nonzero noise floor along the fiber,and the pure chaotic BGS is ulteriorly obtained by the Lorentz fit.Ultimately,distributed strain sensing along a 27.54-km fiber with a 2.69-cm spatial resolution is experimentally demonstrated,and the number of effective resolving points is more than 1,020,000.