In order to realize a high flattening C+L-band fiber source by C band matching L band closely

a superfluorescent light source structure with three-stage two-pumping is presented. Firstly

the experimental equipment is composed of three erbium-doped fibers

two 980 nm LDs

a Wavelength Division Multiplexer (WDM)

an isolater（ISO）and a 3 dB coupler. Then

a high flattening C+L-band fiber source is achieved by optimizing the lengths of three erbium-doped fibers and adjusting the powers of two pumps

and the mechanism of production is also analyzed. Experimental results indicate that when the lengths of three fibers are 11.5 m

53 m

6.5 m and the powers of the two pumps are 65 mW

115 mW respectively

the light source can offer a linewidth in 75.68 nm with a power ripple of 3 dB

and the flatness of the spectra from 1 543 nm to 1 603 nm is less than ±1.3 dB without any external spectral filters. The high flattening C+L-band superfluorescent light source can satisfy the requirements of the optical fiber sensing and optical fiber communication systems.