Recently, both quartic self-similar pulses (QSSPs) and dissipative pure-quartic-solitons (DPQSs) pulses have been theoretically demonstrated in mode-locked fiber laser with pure positive fourth-order dispersion (FOD). Here, we investigate the existence regions and dynamics of those two soliton pulses by numerically solving the cubic-quintic Ginzburg-Landau equation. We find the positive FOD fiber laser tends to emit QSSPs in the presence of high nonlinear gain, while it is apt to generate DPQS pulses in the case of low nonlinear gain. An unstable pulse region separates the QSSP region from the...
