LAUSR

Abstract In this paper, an optical fiber sensor consisting of a Mach–Zehnder interferometer (MZI) cascaded with a fiber Bragg grating (FBG) is proposed and experimentally demonstrated. The MZI consists of two novel trapezoid cone structures and a length of single mode fiber (SMF). Each structure is fabricated by cutting a down-taper, which is served as a coupler to excite the m th cladding mode and re-couple it to the fiber core. The cascaded FBG is employed for temperature compensation. As refractive index (RI) and temperature change, the transmission spectra of the MZI and FBG shift. Thus, RI and temperature can be simultaneously measured by monitoring the valley shift. The proposed sensor exhibits a RI sensitivity of -101.30 nm/RIU (refractive index unit) in range of 1.333-1.365. Meanwhile, the temperature sensitivity is 0.10 nm/°C and 0.01 nm/°C in the range of 25–95 °C. The proposed sensor has the advantages of low cost, low insertion loss, high sensitivity, easy fabrication and good stability.