Observation of the evolution of mode-locked solitons in different dispersion regimes of fiber lasers

An all-fiber laser of mode-locked solitons based on the nonlinear polarization rotation (NPR) is proposed with a simple fiber ring cavity. The net dispersion of the ring cavity is adjusted by changing lengths of the erbium-doped fiber (EDF) and single mode fibers (SMFs) in the cavity, resulting in three different dispersion regimes: anomalous dispersion, normal dispersion, and near-zero dispersion. With different intracavity dispersions, the proposed laser can deliver the conventional soliton, typical dissipation soliton (DSs). These nonlinear waves show different features, including the spectral shapes and time traces. Especially in the near-zero dispersion cavity, the DS presents the ultra-broad spectral width. The experiment results provide insight into the evolution of mode-locked solitons with the net cavity dispersion in fiber lasers.