Optical Fiber Gratings for Humidity Measurements: A Review

A review of the current status of humidity sensors based on optical fiber gratings (OFGs) is presented. Humidity monitoring and its control are gaining importance in several fields including industrial processes and health. This review aims at giving an overview of the major developments over the last decades and categorizing the recent progress in humidity sensors based on the OFGs functionalization. This review describes the measurement principle of these sensors, their metrological properties, the materials used to functionalize OFGs, and the factors which influence the sensors' response.