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High-temperature enhanced Rayleigh scattering optical fiber sensor for borehole applications

This study presents a high-temperature distributed acoustic sensor (HT-DAS) optical fiber that utilizes a single layer of unique specialty coating with elevated thermal stability applied atop a 125 μm single-mode transmission fiber, where the fiber features enhanced Rayleigh backscattering sensitivity combined with long-term robustness and survivability up to 150 °. The developed HT-DAS fiber possesses a similar level of mechanical strength and transmission loss as most industrial specialty and telecommunication optical fibers, but also exhibits remarkable distributed sensing characteristics: enhanced elastic backscattering signal intensity about 12 dB above the base Rayleigh scattering level of non-enhanced fiber. Most importantly, this fiber extends service feasibility to a relatively high temperature regime for 1 year at about 150°C, according to life-time estimation based on thermogravimetric analysis, failure mode analysis, and accelerated aging reliability test.