Single Modal Interference-Based Fiber-Optic Sensor for Simultaneous Measurement of Curvature and Strain With Dual-Differential Temperature Compensation

In this paper, a thin-core fiber-based in-line Mach–Zehnder interferometer is theoretically and experimentally demonstrated, and a high sensitivity consistency of temperature (>0.995) is obtained owing to the formed single modal interference. Furthermore, the nonlinear wavelength-dependence of elastic-optical coefficient is characterized, and a sharp intensity inversion between the macro- and micro-bending states is experimentally observed. Then, a novel dual-differential compensation (DDC) method is proposed to eliminate the temperature errors in the measured curvature and strain. By means of DDC, the variations of curvature and strain can be simultaneously detected and discriminated without the crosstalk of ambient temperature, and the corrected sensitivities, respectively, reach −17.67 nm/m
⁻¹
and −1.92 pm/
$\mu \varepsilon $
. This fabricated sensor is very practical and promising for the accurate measurement of multiple parameters.