A Temperature and Curvature Dual Parametric Sensors Based on Seven Core Fiber and Taper-Biconcave Structure

A seven-core fiber (SCF) dual parametric sensor based on a taper-biconcave structure is proposed. The end faces of SCF and single-mode fiber (SMF) are discharged to form a spherical structure, and the spherical structures of the two fibers are fused to form two concave regions. The SCF is tapered using the flame melting method to excite interference between the fundamental and higher order modes. When the external environment is changed, the effective refractive indices of each core mode and cladding mode of the SCF are changed to different degrees, which causes changes in the interference spectrum of the sensor. The experimental results show that the temperature and curvature sensitivities of the sensor are 114.84 pm/°C and −13.60 nm/
$\text{m}^{-{1}}$
, respectively, and the temperature and curvature resolutions can reach 1.7666 °C and 0.0157m
$^{-{1}}$
, and the maximum crosstalk coefficient of the temperature to curvature is 3.02m
$^{-{1}}$
/RIU, which effectively solves the cross-sensitivity problem. This sensor has simple fabrication and high sensitivity and can be used for temperature and curvature detection in industrial production and precision measurement environments.