A broadband flatten Er-doped superfluorescent fiber source is designed and implemented,in which the double-pass backward pump is adopted.The dual pumps are obtained by using a 980 nm 1×2 coupler and a 980 nm laser diode(LD).This configuration improves the characters such as power,bandwith and flatness of the source without using any external spectral filters.The highest power of the source is up to 41.48 mW(16.18 dBm),the 3 dB band width is 40 nm,and flatness is ±1.5 dB,and the structure is simp...