Influences of irradiation on network microstructure of low water peak optical fiber material

A study of the influences of irradiation on network microstructure in optical fiber material by Raman and infrared spectroscopy is presented. A local doping hybrid three- and four-membered ring (3MRs–4MRs) microstructure model is proposed for the binary silica optical fiber material. Density functional theory (DFT) calculations for doping hybrid rings show that the germanium atom is easily doped among mixed rings and network interstices to form steady doping hybrid rings of network microstructure. Ge-doped 4MRs microstructure is found to be energetically more stable than 3MRs while the Ge–O bond is easier to rupture and generates color centers by the external energy effect. The theoretical calculations are validated with Raman and infrared spectra measurement of fiber material microstructure by gamma-ray irradiation. The number of the 3MRs and 4MRs, especially 3MRs, are obviously reduced with increasing irradiation doses.