Optical Fiber Humidity Sensor Using Nafion^R‐Tri‐Phenylcarbinol Composite

By using Nafion film with tri‐phenylcarbinol, the optical fiber humidity sensor was fabricated. The optical intensity around 450 nm in the reflection mode increases with the relative humidity. The resolution, i.e., the sensitivity to the relative humidity decreases in the range above 30% relative humidity. In a dry atmosphere, the dye exists in the form of tri‐phenylcarbonium ion, and with increasing the relative humidity, the dye structure changes from the carbonium ion to carbinol.