Intermittent events due to spectral filtering induced multi-pulsing instability in a mode-locked fiber laser

In this paper, numerical simulations of an all-normal dispersion ring cavity mode-locked fiber laser have been reported, revealing the existence of rogue waves in the chaotic transition regime between a stable single-pulse state and a multi-pulse state. The chaotic states manifest as a result of multi-pulsing instability induced by the intra-cavity spectral filtering effect and were studied by gradually decreasing the filter bandwidth from a stable or quasi-stable state to a stable multi-pulsing state. For a specific set of cavity parameters and a range of Gaussian-shaped filter bandwidths, stable dissipative solitons characterized by a cat-ear-shaped spectrum were obtained. Reducing the filter bandwidth below the stable range first produced non-stationary quasi-stable states containing multiple soliton explosions and then eventually a stable multi-pulsing state with individual dissipative solitons. The histograms of spectral intensities in the quasi-stable states exhibited long-tailed distributions containing rogue waves. Rogue waves were also observed during the build-up of the dissipative soliton from white Gaussian noise even though the pulse finally evolved to a stable state. By modifying the cavity parameters, noise-like pulses (NLPs) were obtained which are by nature a quasi-stable state and exhibited rogue waves in the spectral intensity histogram. In the NLP state of operation, the reduction of filter bandwidth below a certain range produced multiple dissipative solitons with stable waveform. Additionally, the influence of different filter shapes on the state transition dynamics was also explored. It was found that the range of filter bandwidths for which chaotic states exist varies for different filter shapes depending on their spectral confinement.