title: Cooperative luminescence and absorption in Ytterbium-doped silica fiber and the fiber nonlinear transmission coefficient at lambda=980 nm with a regard to the Ytterbium ion-pairs' effect: Comment.
abstract: Recently, significant power losses in ytterbium-doped fibers have been interpreted as resulting from the formation of ytterbium ion pairs [A. V. Kir'yanov et al., Opt. Express 14, 3981 (2006)]. However, there appears to be strong evidence against this model.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Paschotta
authors.forename: Anne C
authors.initials: AC
authors.lastname: Tropper