Evaluation Of An FTIR/Fluoride Optical Fiber System For Remote Sensing Of Combustion Products

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Abstract
Infrared transmitting optical fibers were combined with a Fourier Transform Infrared Spectrometer (FTIR) to perform remote quantitative gas analysis. A glass clad fluoride fiber, 1/2 meter in length, transmitted the infrared radiation to a double pass reflective gas cell, with a total pathlength of 10 cm, and a second fiber returned the absorbed characteristic spectrum back to the instrument. Methane (CH4), carbon dioxide (CO2), and carbon monoxide (CO), were readily detected to very low concentrations in nitrogen with this arrangement. The concentration range and lower detection limit are dependent upon the absorption coefficient of each gas, the pathlength of absorption, and the available energy throughput at the detection wavelength. Carbon monoxide had the largest range of detection at this pathlength, with detection capabilities from 100 vol% to 0.3 vol% in nitrogen. Methane was detected from 15 vol% to 0.2 vol% and carbon dioxide was detected from 2.5 vol% to 0.05 vol%. From this study, it was determined that the fluoride fiber/FTIR system can be utilized to remotely detect gases effectively. Proper adjustment of the absorption pathlength will enable each gas to be detected over a broad range of concentrations.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

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