Derivation of Raman threshold formulas for CW double-clad fiber amplifiers

We show that the classic Raman threshold formula is unsuitable to accurately predict the onset of Raman scattering in high-power CW double-clad fiber amplifiers. Consequently new analytical formulas for the Raman threshold are obtained and their accuracy is tested. Using these new formulas, the dependence of the Raman threshold on various parameters is studied. (C) 2009 Optical Society of America