Investigation of Analysis of Water Vapor Present in Breath Using an Optoelectronic Sensor

In the present study, an off-axis cavity-enhanced absorption spectroscopy (OA-CEAS)-based optoelectronic sensor is reported for analysis of water vapor present in breath. First, theoretical study based on the HITRAN data base was performed in order to determine an isolated absorption line for detection of water vapor. After that, the experimental analysis of water vapor in breath was conducted using the absorption line found out from the theoretical study. A tunable laser system operating between the spectral range 1250 and 1350 nm was used. This laser was coupled into the CEAS cell via a lens with a focal length of 50 cm and a mirror. The cavity consists of two highly reflective mirrors positioned 50 cm apart with a reflectivity of > 99.96% over the spectral range between 700 and 1650 nm with a 2.54 cm diameter and a radius of curvature of 1 m