Data Center (DC) servers consume a huge amount of energy. However, a part of this energy (cooling and information technology devices) can be saved by shutting down racks containing idle servers. This can be achieved by rerouting workloads from partially loaded racks, and thus allowing additional racks to switch into idle mode. Workload rerouting requires additional wired links or by optical wireless communication (OWC) links, which can be deployed on top the existing network. In comparison to classic wired infrastructure, OWC deployment and maintenance is faster and simpler, and it offers dynamic configuration of the network. Moreover, OWC can be used to augment the performance of virtualization techniques, which allow load balancing. In this paper we developed a mathematical model and an optimization algorithm along with numerical simulations, which evaluate the energy consumption in DCs. Results show that for a uniform distributed load between 24-100% and a 100% deployment of OWC links, 33% of the IT and cooling energy consumed can be saved.