The surface of the fiber optic humidity sensor is a layered structure composed of silicon oxide and zirconia with different reflection coefficients. Through advanced thermal curing technology, the pore size of the sensor surface is controlled at 0.3nm, and water molecules at 0.28nm can penetrate. The controller emits a beam of near-infrared light at 790-820nm, which is transmitted to the sensor through a fiber optic cable. The water molecules entering the sensor will change the reflection coefficient of the light, causing a change in wavelength, which is proportional to the moisture content of the medium.