Fiber Wireless (FiWi) access network is the incorporation of optical access network and wireless access network. ONU Placement is important issue in FiWi, since it relates to the network performance and cost of the network. The present research work finding the potential sites of ONUs in the network with the help of proposed algorithm. In this, Firstly ONUs are put in the center part of the grids in network. Further the positions of ONUs are optimized with Whale optimization algorithm followed by minimizing of the ONUs. Hence proposed work gives potential sites for ONUs. Simulation result demonstrates and proves the utility of the present paper.