We have carried out a systematic study of optical emission in Yb doped fiber glass materials which can be used for fiber laser applications. The stimulated emissions cross- sections of these materials have been calculated. The wavelength dependence of emission of these materials has been studied. The peak emission cross section in Yb doped Silica glass is 2.6 pm2 and the peak wavelength is at 974 nm. The co-dopants do not significantly alter the emission cross section or the peak wavelength of this cross section.