In this study, system approach is applied by Volterra series for the previously designed non-linear optoelectronic feedback laser diode system. Photon (P0) and gain (g) equalities are obtained from zero order solution and are used for the geometrical approach. The relation between gain and photon population is determined according to threshold current (I th) for possible linear regions. The maximum and minimum angle and the corresponding Ith ratio values are computed. The optimum linear region, maximum Ith ratio for linear usage and the corresponding Ith value where the saturation point begins are also determined.