Simultaneous measurement of temperature and depth using Fabry–Perot interferometers with draw-tower gratings

【摘要】 Marine monitoring faces significant challenges due to the vast spatial scale and subtle variations in environmental parameters, necessitating distributed sensor systems with exceptional sensitivity and multiplexing capabilities. While existing high-sensitivity fiber optic sensors lack sufficient multiplexing capacity for large-scale deployment, we present a novel distributed sensing scheme integrating Fabry–Perot interferometers（FPIs） with draw-tower gratings（DTGs）. Each FPI is constructed through two adjacent DTGs interconnected via functionalized sensing fibers with distinct coating materials to decouple the mutual cross-sensitivity between temperature and pressure. Through mechanical capsulation with a pressure-sensitive copper tube, hydrostatic pressure-induced deformation creates measurable axial strain gradients in the optical fiber, achieving enhanced depth sensitivity. The experimental results show that the sensor exhibits good linear responses（R²> 0.99） across tested parameter ranges, with measured temperature and depth sensitivities of12,784 rad/℃ and 801 rad/m, respectively, consistent with theoretical models. The system achieves remarkable resolution of 1.56 × 10^-5℃（temperature） and 2.50 × 10^-4m（depth） through phase-sensitive detection. Leveraging the ultra-weak reflectivity of DTGs and the compatibility of the sensing array with the Michelson interferometer（MI）, the sensing structure exhibits excellent multiplexing capability. With advantages of high sensitivity, unprecedented resolution, and ease of multiplexing, the structure possesses significant potential as an efficient solution for distributed measurements in marine engineering.更多还原

【Abstract】 Marine monitoring faces significant challenges due to the vast spatial scale and subtle variations in environmental parameters, necessitating distributed sensor systems with exceptional sensitivity and multiplexing capabilities. While existing high-sensitivity fiber optic sensors lack sufficient multiplexing capacity for large-scale deployment, we present a novel distributed sensing scheme integrating Fabry–Perot interferometers（FPIs） with draw-tower gratings（DTGs）. Each FPI is constructed through two adjacent DTGs interconnected via functionalized sensing fibers with distinct coating materials to decouple the mutual cross-sensitivity between temperature and pressure. Through mechanical capsulation with a pressure-sensitive copper tube, hydrostatic pressure-induced deformation creates measurable axial strain gradients in the optical fiber, achieving enhanced depth sensitivity. The experimental results show that the sensor exhibits good linear responses（R²> 0.99） across tested parameter ranges, with measured temperature and depth sensitivities of12,784 rad/℃ and 801 rad/m, respectively, consistent with theoretical models. The system achieves remarkable resolution of 1.56 × 10^-5℃（temperature） and 2.50 × 10^-4m（depth） through phase-sensitive detection. Leveraging the ultra-weak reflectivity of DTGs and the compatibility of the sensing array with the Michelson interferometer（MI）, the sensing structure exhibits excellent multiplexing capability. With advantages of high sensitivity, unprecedented resolution, and ease of multiplexing, the structure possesses significant potential as an efficient solution for distributed measurements in marine engineering.更多还原