In this paper the absorption cross sections of Er3+ in the fluoride glasses host are obtained from its measured stimulated emission cross sections using the more general theory of McCumber. Based on this

we make the theoretical and experimental study of the multichannel signal amplification in an Erbium-doped fiber amplifiers which have a flattened small signal gain spectrum and get the same results. we also propose a new simple plan for gain equalization in "Wavelength Division Multiplexing + Erbium-Doped Fiber Amplifiers"Trunk lightwave systems by using Erbium-Doped Fluoride Fiber Amplifiers as its repeaters.