This study presents a control plane design for an optical multicast-capable datacenter network and evaluates the system performance using simulations. The increasing number of datacenter applications with heavy one-to-many communications has raised the need for an efficient group data delivery solution. We propose a clean-slate architecture that uses optical multicast technology to enable ultra-fast, energy-efficient, low cost, and highly reliable group data delivery in the datacenter. Since the optical components are agnostic of existing communication protocols, I design novel control mechanisms to coordinate datacenter applications with the optical network. Applications send explicit requests for group data delivery through an API exposed by a centralized controller. Based on the collected traffic demands, the controller computes optical resource allocations using a proposed control algorithm to maximize utilization of the optical network. Finally, the controller changes the optical network topology according to the computation decision and sets forwarding rules to route traffic to the correct data paths. I evaluate the optimality and complexity of the control algorithm with real datacenter traffic. It achieves near optimal solutions in almost all experiment cases and can finish computation instantaneously on a large datacenter setting. I also develop a set of simulators to compare the performance of our system against a number of state-of-the-art group data delivery approaches, such as the non-blocking datacenter architecture, datacenter BitTorrent, datacenter IP multicast, etc. Extensive simulations using synthetic traffic show our solution can provide an order of magnitude performance improvement. Tradeoffs of our system are analyzed quantitatively as well.