Abstract Double index chalcogenide fibers, based on tellurium, arsenic, and selenium, have been made by an original technique. This technique, based on the build-in-casting method, is achieved in a sealed silica ampoule. In view of the low attenuation obtained in the mid-infrared (IR), these fibers are used to implement Fiber Evanescent Wave Spectroscopy (FEWS). As the IR light is only propagated through the core of the waveguide, a chemical etching is applied in order to remove the glassy cladding of the sensing zone. IR spectra of ethanol and chloroform, recorded with such sensor, are presented showing the high sensitivity of the method.