Brillouin optical correlation domain analysis based on chaotic laser with suppressed time delay signature

A new technology for Brillouin optical correlation domain analysis (BOCDA) based on chaotic laser is proposed, analyzed and demonstrated. The numerical simulation shows that the stimulated acoustic field has the secondary spurious peaks, which are the result of a weak amplitude autocorrelation of the chaotic signal occurring at the delay time of the external cavity, i.e., time delay signature (TDS). These secondary spurious peaks deteriorate the Brillouin gain spectrum and decrease the performance of the chaotic BOCDA system. The effect of the injection current and feedback strength on the TDS suppression is theoretically analyzed. By optimizing the two free parameters, chaotic laser sources operate in a TDS suppression region. Ultimately, a 3.2 km long single-mode fiber with a spatial resolution of 7.4 cm is experimentally demonstrated. The uncertainty of the local Brillouin frequency shift is ± 1.2 MHz.