  Hybrid mode-locking has been widely used in enhancing pulse quality, however
how the hybrid two mode-locking techniques work remains unclear. In this paper,
we experimentally investigate three pulse formation mechanisms in saturable
absorbers (SA) and nonlinear polarization evolution (NPE) passively hybrid
mode-locked fiber laser, which are SA-dominated, NPE-dominated, and SA-NPE
co-domination switching. Clarified the exists dynamic competition and
cooperation among the mode-locking techniques. For the first time, the method
of simulating filtered gain spectrum with customized filtering is proposed, and
the switching of pulse formation mechanisms is numerically investigated using
the coupled Ginzburg-Landau equations. Our results deepen the understanding of
hybrid mode-locked fiber lasers and provided a foundation for multi-wavelength
mode-locked lasers with different mode-locking techniques in a single cavity.
