FIBER OPTIC EVANESCENT FIELD SENSORS FOR GASEOUS SPECIES USING MIR TRANSPARENT FIBERS

A new method of optical gas sensing is presented which uses evanescent waves of optical fibers. Gas detection can be done in a simple, flexi ble, and possibly distributed way using a single optical fiber as both the sensor with an active element of 10 cm and the transmission line for optical signals. The detection of several single gaseous species - such as hexane, trichloro-trifluoro-ethane, methane, acetone, etc. as well as gaseous mixtures in a concentration range of 1-10% could be a chieved with an average reproducibility of 2-3% with a chalcogenide fi ber optic coupled to an IFS 88 Bruker spectrometer.