Reconfiguration of unicast or multicast connections in an optical network is a critical task. Indeed, if it is not carried out correctly, it can lead to optical flow (also called flow) interruptions that can cause damage to the network operator. It is therefore common to perform the reconfigu-ration in several steps. In this study, we focused on multicast connection reconfiguration because multicast connection become more attractive and efficient technique to transmit flow of multicast applications. A Multicast connection in an optical network can be represented by a point-to-multipoint all-optical path called light-tree. In short, we explain how to select a pair of sub-trees (current sub-tree, new sub-tree) to be reconfigured at a given step of the reconfiguration process.