A computer-implemented method and system for designing a fiber optic network for a plurality of premises in a geographic area that has existing infrastructure. The system includes an input module arranged to electronically receive design outputs comprising geographic locations of nodes in the fiber optic network and arcs extending between the nodes, relative to at least elements of existing infrastructure used as geographic locations for the nodes and the arcs, the elements of the existing infrastructure being associated with characterizing data that characterizes the elements of existing infrastructure; the input module is further arranged to electronically receive validation data corresponding to the elements of the existing infrastructure, the validation data being indicative of validity of the characterizing data. The system includes an optimizer arranged to electronically generate new design outputs by optimizing geographic locations of the nodes and the arcs in the fiber optic network.