The behavior of Erbium-doped superflorescent fiber sources (SFS) is simulated numerically. Both simulated output power and spectral shape of SFS are shown to be in good agreement with the experimental results for the cases of SPB/SPF configurations. The theoretical analysis of SFS in double-pass backward configuration (DPB) are presented for the first time. It is shown that with certain reflectivity reflector, DPB SFS can provide not only higher pump efficiency but also larger spectral width than other configuration SFSs under stable operation conditions.