  Data centers based on Passive Optical Networks (PONs) can offer scalability,
low cost and high energy-efficiency. Application in data centers can use
Virtual Machines (VMs) to provide efficient utilization of the physical
resources. This paper investigates the impact of VM placement on the
energyefficiency in a PON-based data center architecture that utilizes cascaded
Arrayed Waveguide Grating Routers (AWGRs). In this paper, we develop a Mixed
Integer Linear Programming (MILP) optimization model to optimize the VM
placement in the proposed PON-based data center architecture. This optimization
aims to minimize the power consumption of the networking and computing by
placing the VMs and their demands in the optimum number of resources (i.e.,
servers and networking devices) in the data center. We first minimize the
processing power consumption only and then we minimize the processing and
networking power consumption. The results show that a reduction in the
networking power consumption by up to 75% is achieved when performing joint
minimization of processing and networking power consumption compared to
considering the minimization of the processing power consumption only.
