Optical Fiber Sensor for Monitoring the Evaporation of Ethanol–Water Mixtures

An inline optical fiber sensor is proposed to monitor in real time the evaporation process of ethanol–water binary mixtures. The sensor presents two interferometers, a cladding modal interferometer (CMI) and a Mach–Zehnder interferometer (MZI). The CMI is used to acquire the variations in the external medium refractive index, presenting a maximum sensitivity of 387 nm/RIU, and to attain the variation in the sample concentration profile, while the MZI monitors temperature fluctuations. For comparison purposes, an image analysis is also conducted to obtain the droplet profile. The sensor proposed in this work is a promising alternative in applications where a rigorous measurement of volatile organic compound concentrations is required, and in the study of chemical and physical properties related to the evaporation process.