  The continually growing demands for traffic as a result of advanced
technologies in 5G and 6G systems offering services with intensive demands such
as IoT and virtual reality applications has resulted in significant performance
expectations of data center networks (DCNs). More specifically, DCNs are
expected to meet high bandwidth connectivity, high throughput, low latency, and
high scalability requirements. However, the current wired DCN architectures
introduce large cabling requirements and limit the ability to reconfigure data
centres as they expand. To that end, wireless technologies such as Optical
Wireless Communication (OWC) have been proposed as a viable and cost-effective
solution to meet the aforementioned requirements. This paper proposes the use
of Infrared (IR) OWC systems that employ Wavelength Division Multiplexing (WDM)
to enhance the DCN communication in the downlink direction; i.e. from Access
Points (APs) in the ceiling, connected to spine switches, to receivers attached
to the top of the racks representing leaf switches. The proposed systems
utilize Angle Diversity Transmitters (ADTs) mounted on the room ceiling to
facilitate inter-rack communication. Two different optical receiver types are
considered, namely Angle Diversity Receivers (ADRs) and Wide Field-of-View
Receivers (WFOVR). The simulation (i.e. channel modeling) results show that our
proposed data center links achieve good data rates in the data centre up to 15
Gbps.
