Abstract: A broadband Erbium-doped passively mode-locked fiber laser has been proposed and demonstrated, which lays the foundation for optical comb and fiber femtosecond pulse. The fiber laser is based on the nonlinear polarization rotation technique of mode-locked mechanism. Meanwhile, the C-band and L-band fiber has been reasonably combined in large normal dispersion region to ensure that the gain bandwidth covers C+L band. When the pump power reaches 350mW, the pulses operate stably with fundamental frequency of 4.32MHz, the 3dB bandwidth of spectrum is 58.5nm and 20dB spectrum covers 1522nm to 1630nm, which covers the whole C+L band. The method of gain joint to broaden spectrum can effectively avoid nonlinear phase noise of spectrum component and it is conducive to compress the pulses further.

Key words: laser techniques; C+L band; passively mode-locked; fiber laser