In the context of this work, a computer program is developed for the simulation of the interference fringe patterns of laboratory-scale pool-fires of organic fuels. With the help of this simulation tool, the formation as well as the dynamics of typical structural components in the interference fringe patterns in the flame neck and the flame plume are modelled. A model conception for the formation of the interference fringe patterns in the flame plume is developed. The temperature field is modelled as a relatively cold convection column, into which a large amount of statistically distributed hot volume elements with gaussian temperature distribution is inserted. The simulation with this model conception shows the typical structure of the measured interference fringe patterns in the flame plume with good congruence. The physical meaning of the velocity of the interference fringe pattern shift within the areas of the flame neck and the flame plume is examined. It is shown in particular that the temporally averaged shifting velocity in vertical direction in the flame neck can be identified as a temporally averaged ascent rate of the flame gases within the region of the thermal boundary layer. For the flame plume, the shifting velocity can be interpreted as a flow velocity averaged over time and the line of sight.