Fiber optic hybrid structure based on an air bubble and thin taper for measurement of refractive index, temperature, and transverse load

Abstract A hybrid-structured optical fiber sensor for measurement of refractive index (RI), temperature, and transverse load is proposed and experimentally demonstrated, which is made by fusing a section of single-mode fiber (SMF) between an air bubble and a thin taper. The air bubble acts as a Fabry-Perot interferometer (FPI) and at the same time serves as excitation for Mach-Zehnder interferometer (MZI). The transverse load can be measured by demodulating the reflection spectrum of the FPI. The RI and temperature can be measured by demodulating the transmission spectrum of the MZI. The experimental results show that the transverse load sensitivity of FPI is 1.596 nm/N. The RI and temperature sensitivities are 103.2 nm/RIU and 103.2 pm/°C, respectively. Due to its ease of manufacture, low cost, and high sensitivity, the hybrid-structured optical fiber sensor is practical for sensing applications.