Change of the refractive index in an optical fiber due to external forces.

This paper investigates experimentally the change of the refractive index, due to forces such as pulling and pure bending, in an optical fiber fabricated by the CVD technique. It is found that this phenomenon can be interpreted in terms of a simple model of the fiber, that is, a mechanically homogeneous circular rod. We compare the effect of the refractive-index change and that of a geometrical deformation of the fiber on transmission characteristics. A new method based on photoelasticity is also proposed to measure the curvature distribution of a fiber whose axis is deformed by external forces.