Infrared glass fibers for evanescent wave spectroscopy

IR glass optical fibers have been developed in order to optimize their response when they are used as evanescent wave chemical sensors. The diameter of the sensitive part of the fiber can be reduced by tapering the fiber during the drawing process or by chemical polishing. In using an FTIR spectrometer associated with a MCT detector, it was possible to evaluate the influence of the fiber diameter on the polymer coating IR signature as well as the sensitivity of a such sensor. The high flexibility of thin fibers allows the achievement of a detection probe which has been introduced in a microwave oven in order to follow a chemical reaction. It is verified that the chalcogen-based fiber is not sensitive to microwave radiation and gives excellent on line IR fingerprints to check kinetics and reaction mechanisms.