Measurements of non-elastic frozen-in residual stress near the cleaved end of an optical fiber by the inverse linear polarizing method

Abstract

Few years ago, the inverse linear polarizing method (ILPM) has been suggested as an effective measurement method for the residual stress of optical fibers by Y. Park et al. and it has been used as an important tool to study photoelastic and birefringent characteristics of optical fibers. Non-elastic frozen-in residual stress was only recently found to be an important draw-induced inelastic strain that can significantly perturb the refractive index profile and hence the waveguiding properties of optical fibers. We have investigated residual stress distributions of optical fibers drawn at various draw tensions along the distance from the cleaved fiber end by using the ILPM. From the measurement of residual stress distributions and the definition of the mean axial stress, we calculated non-elastic frozen-in residual stress of optical fibers drawn at various draw tension. By the calculation of non-elastic frozen-in residual stress distributions of optical fibers, we have found that non-elastic frozen-in residual stress in the optical fiber can be released near the cleaved fiber end and release degree of non-elastic frozen-in residual stress near the cleaved fiber end is proportional to draw tension applied on the optical fiber fabrication. We have also found that non-elastic frozen-in residual stress along the cleaved fiber end becomes restored and restoration tendency of non-elastic frozen-in residual stress from the cleaved fiber end is dependent on draw tension applied on the optical fiber fabrication.