Dissolved gas sensing using an anti-resonant hollow core optical fiber

Author Posting. © Optical Society of America, 2021. This article is posted here by permission of Optical Society of America for personal use. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. The definitive version was published in Applied Optics 60(33), (2021): 10354–10358, https://doi.org/10.1364/AO.439787.Sensors that measure dissolved gases directly are needed for environmental, industrial, and biomedical applications. Here we present a hollow core fiber optic sensor capable of measuring dissolved methane gas in liquids using only nanoliters of sample gas. The sensor is based on an anti-resonant hollow core fiber combined with a permeable capillary membrane inlet that extracts gas from the liquid for analysis. Using a small capillary inlet for gas extraction is only possible due to the small amount of sample gas needed for analysis, and it presents new possibilities for dissolved gas analysis in a simple, robust, and compact sensor configuration. We demonstrate the sensing technique using wavelength modulation spectroscopy and measure methane dissolved in water with a 1 lower detection limit of 230 ppb, a resolution of 45 ppb, and a response time of ∼8min.NOAA Ocean Exploration and Research (NA18OAR0110354); Schmidt Marine Technology Partners (G-2004-59353); Woods Hole Oceanographic Institution (Innovative Technology Award)