Multicomponent trace gas detection with hollow-core fiber photothermal interferometry and time-division multiplexing

Abstract

We report a multicomponent photothermal gas sensor with a conjoined-tube hollow-core optical fiber gas cell. With a common Fabry-Perot probe interferometer and a common gas cell, simultaneous detection of methane, acetylene and ammonia can be achieved by time-division multiplexing. Experiments with a 15-cm-long hollow-core fiber demonstrated noise-equivalent concentration of 24.2 parts-per-billion (ppb) for methane, 11.6 ppb for acetylene, and 46.1 ppb for ammonia. The dynamic range is measured to be around 5 orders of magnitude. The crosstalk issue is addressed by spectrum fitting. Assisted with an air pump and a compact gas chamber, the response time of less than 10 s is achieved.