By optimizing the gain ratio and dispersion compensation fiber length ratio of Raman/erbium-doped hybrid fiber amplifier(HFA),a novel optimal HFA configuration was presented for given non-linearity impact.The noise performances of optimal HFA,other HFA,all erbium-doped fiber amplifiers(EDFA) and all fiber Raman amplifiers(FRA) are compared for the use as preamplifiers.The maximum reachable distances of multi-span systems were analyzed when these fiber amplifiers are used as inline amplifiers.The optimal HFA can improve the amplifying system performance.