A new approach is investigated for the fabrication of double index chalcogenide glass fibers. The preform is obtained by an original technique based on "build-in casting" inside a sealed silica container. The two glasses, chosen in the Te– As–Se system, are prepared separately by purification, melting and homogenization of the raw elements under vacuum. The core/clad structure is obtained by using a core composition, which is enriched with tellurium. A strict control of the fabrication parameters allows one to obtain well-defined core/clad diameter ratios. The preform is drawn at 270 °C and coated on line by a protective polymer.