Hydrophilic cladding fiber based on silicone hydrogel for temperature, humidity, and salinity detection.

We propose a hydrophilic cladding optical fiber based on silicone hydrogel (HCF-SH), employing a highly hydrophilic copolymeric silicone hydrogel as the cladding and 98% glycerol as the high-refractive-index core. Owing to its high water content and excellent biocompatibility, the silicone hydrogel responds sensitively to environmental changes such as temperature and humidity, thereby modulating total internal reflection and altering optical transmission. The glycerol core ensures stability and provides a large refractive-index contrast with the cladding, enabling efficient light confinement and propagation. Furthermore, the replaceable liquid core offers flexible and tunable optical properties. The HCF-SH enables real-time monitoring of temperature, humidity, and salinity, demonstrating strong potential for environmental monitoring and biomedical sensing applications.