  The ability to provide very high data rates is a significant benefit of
optical wireless communication (OWC) systems. In this paper, an optical
wireless downlink in a data centre that uses wavelength division multiple
access (WDMA) is designed. Red, yellow, green and blue (RYGB) laser diodes
(LDs) are used as transmitters to provide a high modulation bandwidth. A WDMA
scheme based on RYGB LDs is used to provide communication for multiple racks at
the same time from the same light unit. Two types of optical receivers are
examined in this study; an angle diversity receiver (ADR) with three branches
and a 10 pixel imaging receiver (ImR). The proposed data centre achieves high
data rates with a higher signal-to-interference-plus-noise ratio (SINR) for
each rack while using simple on-off-keying (OOK) modulation.
