Optical and mechanical effects of frozen-in stresses and strains in optical fibers

Frozen-in stresses and strains can significantly impact both the optical and mechanical performance of optical fibers, enabling unique functionalities or leading to serious impairments. Frozen-in strains can be grouped into two general categories: those directly inducing strong birefringence, which are associated with residual elastic stresses; and those inducing a substantially isotropic index perturbation, which can be described as inelastic frozen-in strains. Both types of frozen-in strains can be simultaneously present in the same optical fiber. Frozen-in viscoelasticity 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. The optical and mechanical effects of both types of frozen-in stresses and strains are reviewed. Both practical applications as well as impairments are discussed.