Abstract: The operation principle of Erbium-doped superfluorescent fiber source (SFS) and several configurations of Erbium-doped SFS are analyzed. The singlepass-backward (SPB) SFS was selected as the source of the fiber optic gyroscope in the application. The factors which may affect the output characteristics of SPB SFS were investigated theoretically. The effect of the Erbium-doped fiber length on pump effective, mean wavelength, spectral linewidth and thermal stability of SPB SFS were analyzed in experiments. It is found that there is an optimal value for the Erbium-doped fiber length for SPB SFS. Using the optimal Erbium-doped fiber length, the influence of the pump power on the spectral-line shape was demonstrated. The stability of the output spectrum and power of SFS at －40℃～60℃ was discussed. A source suitable for inertial navigation grade FOG was obtained.