Strain and temperature sensor based on fiber Bragg grating cascaded bi-tapered four-core fiber Mach–Zehnder interferometer

A novel strain and temperature sensor based on the fiber Bragg grating (FBG) cascaded two-tapered four-core fiber (FCF) Mach–Zehnder interference (MZI) is proposed and fabricated. The two optical fiber tapers, acting respectively as a beam splitter and a coupler, are able to produce interference phenomena, so the high interference extinction ratio (above 20 dB) can be obtained. The attenuation peak at 1562 nm and the FBG center wavelength at 1550 nm in the transmission spectra are, respectively, selected to represent MZI and FBG as the monitoring wavelengths. The results indicate that the sensitivities of MZI to strain and temperature are −1.83 pm μϵ⁻¹ and 46.93 pm C⁻¹, respectively, and those of FBG to strain and temperature are 1.26 pm μϵ⁻¹ and 10.58 pm C⁻¹, respectively. Both the FBG and MZI exhibit insensitivity to the refractive index. The cascaded sensor has good linearity and is applied to measure the strain and temperature simultaneously. (paper)