In a power grid used to distribute electricity, optical fibers can be inserted inside overhead ground wires to form an optical network infrastructure for data communications. We consider the problem of topology design for such a network. To solve the problem, we modify existing methods for topology designs to take into account the topology limitation imposed by an existing power grid. For the design, we adopt a two-level hierarchical architecture consisting of a central backbone connecting multiple access networks. We separate the design into two steps. First, we select the concentrator or backbone nodes and their node members by solving a modified version of the well-known concentrator location problem. Second, we find the connections among concentrators subject to the two-connectivity constraint on the backbone topology. Selection and connection of concentrators are done using integer linear programming (ILP). To reduce the amount of computations involved, as an intermediate step, we provide a method for simplifying of the power grid graph to reduce the problem size for the second step. We solve and present some numerical results for a randomly generated 30-node power grid topology. Key words: topology design, power grids.