A Compact Fiber Cascaded Structure Incorporating Hollow Core Fiber With Large Inner Diameter for Simultaneous Measurement of Curvature and Temperature

A compact fiber cascaded structure for simultaneous measurement of curvature and temperature based on Fabry-Perot (FP) interference and anti-resonant (AR) mechanism is designed and experimentally demonstrated. The proposed structure is manufactured by sandwiching a segment of hollow core fiber (HCF) with large inner diameter and suitable length between two segments of single mode fibers (SMFs). Three sample sensors were fabricated with different HCF lengths. With theoretical analysis and experimental verifications, an HCF length of 1197
μ
m was selected for curvature and temperature experiments. The reflection fringes based on FP interference and transmission envelopes based on AR mechanism can be monitored to measure curvature and temperature variations at the same time. From experimental results, the sensitivities of curvature based on AR mechanism and FP interference are 0.2345 nm/m
⁻¹
and -0.1021 nm/m
⁻¹
, and those of sensitivities of temperature are 0.0172 nm/°C and 0.0017 nm/°C, respectively. Therefore, the different responses in curvature and temperature based on two mechanisms enable the proposed structure to simultaneously measure curvature and temperature.