Properties of silver halide core-clad fibers and the use of fiber bundles for thermal imaging

Optical IR fibers with core-clad structure are of great importance, because they have better qualities than unclad fibers for most IR fiber applications, especially in CO₂ laser power delivery and radiometry. We have fabricated core-clad polycrystalline silver halide optical fibers with different compositions and core diameters. These fibers are easier to handle than unclad fibers and, in spite of their higher attenuation, they can transmit more power density than unclad fibers. The behavior of the scattering losses along these fibers and other optical properties were measured and compared with unclad silver halide fibers. We show that the higher losses in clad fibers result from excessive scattering. The improvement in the fabrication process of clad fibers enabled the production of new elements such as single-mode fibers and fiber bundles for thermal imaging.