Absorption loss at high temperatures in aluminum- and copper-coated optical fibers

Thermally induced variations in the optical loss of optical fibers with metal (copper and aluminum) coatings are studied. It is demonstrated that an increase in the loss related to the OH groups depends on the medium in which the annealing takes place (an increase in the loss related to the OH groups in argon is greater than the increase in air) and on the dopant (an increase in the loss in the core doped with GeO2 + P2O5 is greater than the increase in GeO2).