Flexible Single-Mode Polymer Optical Fiber-Based Modal Interferometer for High-Sensitivity Bending Measurement

A flexible single-mode polymer optical fiber (SMPOF) based modal interferometer for high-sensitivity wrist bending measurement is presented. The SMPOF is fabricated by cyclo-olefin polymer (COP) material via the preform-to-fiber drawing technology. A section of the SMPOF is sandwiched between two standard silica single-mode fibers (SMF) via ultraviolet-cured resin (UV Resin), which constructs the modal interferometer sensor. As the bending applies to the SMPOF, the wavelength and interference depth are modulated simultaneously. Experimental results show that within the curvature range of 0.606–1.364 m
⁻¹
, the curvature sensitivity reaches −4951.965 nm/m
⁻¹
. We also demonstrate its application in high-sensitivity wrist bending measurement by mounting this sensor on the wrist. Since it exhibits the advantages of strong flexibility, high sensitivity, and ease of integration, it is expected to have practical applications in robot joint posture detection and human wearable medical treatment.