Fiber Optic Curvature and Torsion Sensor Based on Waveband Multiplexing

Fiber optic sensors have gained significant attention in recent years due to their compactness, high sensitivity, and immunity to electromagnetic interference, making them ideal for various sensing applications. This study focuses on the development and evaluation of a microfiber-assisted cavity Mach-Zehnder Interferometer (MA-MZI) structure, incorporating a microfiber component to enhance its performance in curvature, shear strain, and temperature sensing. The analysis begins by investigating the influence of microfiber diameter, length, and offset on the spectral characteristics of the MA-MZI structure. Both curvature and torsion strain sensing properties are examined, revealing significant intensity changes with distinct waveband differences. In the curvature test, the L-band demonstrates a high intensity sensitivity of -138.2 dB/m-<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup>, while the torsion experiment shows that the C-band achieves an intensity sensitivity of 23.98 dB/(rad/cm). Additionally, the temperature sensing characteristics of the MA-MZI structure are evaluated, showing a C-band temperature sensitivity of -0.19 nm/°C and an L-band sensitivity of -0.124 nm/°C within the 23-28°C range, indicating that the sensor effectively reduces temperature-induced cross-sensitivity during curvature and twist measurements, ensuring more accurate performance across varying conditions.