Enhancing Long-Range Brillouin Optical Correlation Domain Analysis With a Reconfigurable Optical Delay Line

We propose and experimentally demonstrate the enhancement of a long-range Brillouin optical correlation domain analysis (BOCDA) system by utilizing a reconfigurable optical delay line (RODL). The RODL replaces the several-hundred-kilometer-long delay fiber traditionally used for controlling correlation order in the BOCDA system with time-domain data processing. The RODL, comprised of 11 units of dual 1x2 opto-mechanical switches arranged in a cascaded switch matrix, provides access to 2048 different optical paths, with a maximum differential length of 40.94 meters. This configuration enables the adjustment of the length of the delay line, allowing for the uniform shifting of all correlation peaks (CPs) generated in the BOCDA system. The incorporation of the RODL addresses issue related to non-uniform sensing intervals and significantly reduces localization errors in CPs caused by variations in ambient temperature surrounding the delay fiber. In our experimental studies, we have successfully achieved a consistent sensing interval of 5084 CPs along a 52.6 km sensing fiber and have empirically confirmed a substantial reduction in CP localization errors along the sensing fiber.