Attenuation at 106μm in loaded and unloaded polycrystalline KRS-5 fibers

Extruded polycrystalline KRS-5 fiber exhibits a large amount of residual strain. This strain, which results from the large forces applied in the extrusion process, is a major contribution to the total attenuation. To study the effect of strain on fiber loss, we have measured the total attenuation coefficient αT and the attenuation coefficient due to scattering, αS, as a function of stress applied along the fiber axis. The applied stress σ induces a change in the refractive index, which in turn leads to bulk scattering and excess fiber loss. We have found that αT ∼ σ2, which is in accord with an extension of a recent theory by Harrington and Sparks.