Fiber-optic-based evanescent field chemical sensor using tunable diode lasers for the midinfrared spectral region

A new fiber-optic sensor system, comprised of an IR tunable diode laser source and an unclad multimode IR fiber, is described. Design considerations, theoretical predictions, and experimental verification of the sensor performance are presented. This sensor has a relatively high sensitivity, and it will be very useful for monitoring and controlling in situ and in real time, concentrations and chemical transformations of liquids and pastes