In lightwaves propagating in an optical fiber, (a) Rayleigh scattering and (b) scattering caused primarily by (i) impurities, such as hydroxyl and iron ions, and (ii) vacancy defects, interstitial defects, and scattering centers in the intrinsic material from which the fiber is made. See also  configuration scattering,  interstitial defect,  ion,  lightwave,  optical fiber,  propagation,  Rayleigh scattering,  scattering,  scattering center,  vacancy defect.