High-temperature interferometric fiber-optic acoustic logging sensor based on a thin-walled metal sensitization structure

To address the limitations of conventional electric acoustic logging tools, a long-cavity interferometric fiber-optic acoustic sensor incorporating a thin-walled metal sensitization structure is proposed for acoustic remote detection. Finite element simulations investigated the influence of the mandrel-air cavity parameters on sensing performance: Young's modulus and Poisson's ratio of the sensitivity-enhancing layer and mandrel dimensions. Experimental characterization demonstrates that the optimized sensor achieves a stable acoustic pressure sensitivity of -156.56<i>d</i><i>B</i> re 1 rad/µPa over the frequency range of 20-600 Hz while operating reliably at 240°C. With triaxial acceleration sensitivities below 0.12 rad/g (-18<i>d</i><i>B</i> re 1 rad/g), this design exhibits reliable performance even in a complex downhole environment. The proposed sensor with a pressure-resistant packaging structure is promising in the development of next-generation optical fiber acoustic logging tools for deep oil and gas exploration.