The dynamics of a fiber ring laser mode locked by nonlinear polarization rotation is reduced to a quintic complex Ginzburg-Landau (CGLQ) equation. The coefficients of the equation are explicitly given as functions of the physical parameters of the laser, especially the orientation of the phase plates. Then known results about analytic solutions, stability of pulse-like solutions, and bound states of the CGLQ equation are examined from the point of view of their dependence with regard to the physical parameters.