We report the simulation and modeling of a passively Q-switched dual-cavity fiber-laser-doped Yb–Yb. To the best of our knowledge, this is the first time that the traveling-wave model has been applied to the study of the dynamics and to the optimization of the two laser signals produced by the two-cavity laser. An excellent agreement between our simulation results and the experimental measurements published by other researchers is obtained. In addition, we show that the density of the saturable absorber (SA) is a crucial parameter for the optimization of the two laser signals. An increase in the peak power of the two laser signals by an order of magnitude is obtained by increasing the density of the SA.