Based on a segment of Ytterbium-doped dual-cladding fiber (YDF), an all-fiber superfluorescent fiber source (SFS) experimental system is demonstrated. The characteristics of double-ended output SFS is researched under forward pump condition. And the effects of YDF with different length on the performances of SFS are discussed. Experimental result shows that backward output SFS has higher conversion efficiency and broader bandwidth. When the length of gain fiber becomes shorter, the laser oscillation threshold is higher and thus higher output power can be obtained. With the increasing of gain fiber length, the maximum output power decreases, but the bandwidth of the output spectrum increases at the same time.