Three-parameter measurement optical fiber sensor based on a hybrid structure

We have proposed a hybrid-structured optical fiber sensor that can measure curvature, temperature, and transverse load. The hybrid structure is made by fusing a section of hollow-core fiber (HCF) between an air bubble and an up-taper. The air bubble acts as a Fabry–Perot interferometer (FPI) and at the same time serves as excitation for a Mach–Zehnder interferometer (MZI). HCF is used as an anti-resonant reflected optical waveguide (ARROW), which periodically decreases in the resonant wavelength of the optical transmission spectrum. The transverse load can be measured by demodulating the reflection spectrum of the FPI. By demodulating the wavelength shift of the MZI for temperature sensing and the intensity change of ARROW inclination for curvature sensing, the curvature and temperature can be measured simultaneously. The experimental results show that the transverse load sensitivity of the FPI is 1.53 nm/N. The curvature and temperature sensitivities are 33.23 d B / m − 1 and 20.3 pm/°C, respectively, and the cross-sensitivity is 0.0003 m − 1 / ∘ C . Due to its ease of manufacture, low crosstalk, and high sensitivity, the hybrid-structured optical fiber sensor is suitable for multi-parameter measurement applications.