Development of a single-ended mid-infrared fiber-coupled laser absorption sensor for measurements of temperature, CO, and CO2 in harsh environments

The design and application of a single-ended mid-infrared fiber-coupled laser absorption spectroscopy sensor for acquiring measurements of temperature, CO, and CO2 via time-multiplexed wavelength-modulation spectroscopy (TM-WMS) are presented. This sensor utilizes an indium trifluoride (InF3) fiber bundle with six large multi-mode (MM) catch fibers surrounding one smaller single-mode pitch fiber and a custom optics housing to collect laser light that is back-scattered off native surfaces. The fraction of light collected by the sensor was evaluated for targets made of common materials used in combustion applications (i.e., aluminum, steel, and copper). The sensor was demonstrated with 1 kHz measurements of temperature, CO, and CO2 in steady and unsteady propane-air flames with a target standoff distance of 3 cm. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.