Infrared fibers for medium power delivery in the 10-um region and remote spectroscopy

A new generation of infrared fibers, the TeX glass fibers, operating from 3 to 13 micrometers , exhibits a minimum attenuation of about 0.5 dB/m in the 7 - 9.5 micrometers range. A polymer coating on these fibers increases the mechanical properties and fibers with high flexibility have been obtained. CO 2 laser power delivery has been performed using a TeX glass fiber. More than 2.6 W has been transmitted through a 1 meter long fiber by injecting the maximum output power of the laser. One of the most promising applications of these glass fibers is the remote spectroscopy using either evanescent wave or direct absorption analysis. These technologies provide an opportunity to realize in situ and on-line control of chemical and biological processes. Our prototype system using a FTIR spectrometer allows quantitative and qualitative detection of organic species such as alcohol, cosmetic products which have their fingerprints in the spectral region from 3 to 13 micrometers . The detection efficiency using evanescent wave absorption has been studied as a function of the fiber's diameter. It has been found that this efficiency increases very rapidly when the fiber's diameter decreases.