  In this paper, we propose an energy efficient passive optical network (PON)
architecture for backhaul connectivity in indoor visible light communication
(VLC) systems. The proposed network is used to support a fog computing
architecture designed to allow users with processing demands to access
dedicated fog nodes and idle processing resources in other user devices (UDs)
within the same building. The fog resources within a building complement fog
nodes at the access and metro networks and the central cloud data center. A
mixed integer linear programming (MILP) model is developed to minimize the
total power consumption associated with serving demands over the proposed
architecture. A scenario that considers applications with intensive demands is
examined to evaluate the energy efficiency of the proposed architecture. A
comparison is conducted between allocating the demands in the fog nodes and
serving the demands in the conventional cloud data center. Additionally, the
proposed architecture is compared with an architecture based on state-of-art
Spine-and-Leaf (SL) connectivity. Relative to the SL architecture and serving
all the demands in the cloud, the adoption of the PON-based architecture
achieves 84% and 86% reductions, respectively.
