Mechanism of multiple-soliton formation in passively mode-locked fiber lasers

Based on the coupled complex nonlinear Schrodinger equations, the evolvement of the multi-pulse trains is numerically investigated in erbium-doped fiber ring mode-locked laser using the nonlinear polarization rotation technique. The results show that the transmittance function of the mode-locked fiber ring laser can affect the output of multi-pulsing with the small signal gain increasing. The formation of the multiple-soliton is the result of the peak-power-clamping effects, such as the dispersive waves and pulse-splitting and the soliton energy quantization. It is the dynamic balance between the gain competition and the loss caused by the nonlinear polarization evolvement.