Numerical investigation on inherent pulse-energy fluctuations in the noise-like pulse mode-locked fiber laser

•Low-intensity pulses exhibit higher RIN compared with high-intensity pulses.•The RIN along the cavity is not a constant and influenced by optical components.•Gain saturation effect in the active fiber can suppress pulse-energy fluctuation.•Spectral filter with appropriate profile and bandwidth is benefit to RIN reduction. The pulse-energy fluctuations of noise-like pulses (NLPs) are investigated by numerical simulations for modeling the all-normal dispersion Yb-doped fiber lasers. The intracavity distributions of the pulse-energy fluctuations are presented for the fiber lasers based on the Gaussian filter and saturable absorbers (SAs) with monotonic or sinusoidal transmission curves. The results show that the pulse-energy fluctuations in the cavity are at the minimum after the gain fibers due the gain saturation effect, especially when the pulse energy is close to the saturation energy in the gain fiber. Moreover, in the case of the sinusoidal SA, the pulse-energy fluctuations can be effectively decreased by properly choosing the spectral bandwidth and transmission profile of the filter and the modulation depth of the SA.