Optical fiber as distributed acoustic sensing element with improved Rayleigh backscattering sensitivity and robustness under elevated temperature

Distributed sensing optical fibers have been recognized for their unparalleled ability in discriminating and measuring environmental variables on strain, temperature, and vibration behaviors. For its ubiquitous industrial values in monitoring dynamic events in pipelines, railroads, perimeter surveillance, subsea, highway and so forth, distributed acoustic sensing (DAS) market is expected to grow steadily in the next few years. However, the inferior thermal stability of standard optical fiber coating, along with the native weakness Rayleigh scattering reflectivity, make the traditional telecommunication grade fibers-based DAS component suboptimal for mid-temperature environment deployment such as oilfield exploration and detection. Here, we report DAS fibers prototype with enhanced backscattering reflection and improved thermal robustness for feasible mid-temperature application. Typically, the 8/125/200 μm DAS fiber is fabricated from a G.652 compliant single-mode preform, coated with dual-layer of proprietary UV curable and high optical transparent write-through coatings, and further followed by a post-draw UV processing technology to increase the elastic scattering reflectivity in the optical fiber. Depending on the selected coating materials and fiber designs, developed DAS fibers are demonstrated with low level of OTDR attenuation, enhanced elastic backscattering signal amplitude about 15+ dB above Rayleigh level, and exceptional thermal reliability against elevated temperature conditions.