Optical wireless data center networks (OW-DCNs), which employ optical wireless technology and optical wired switching technology, are gaining interest as they promise to eliminate cable complexity, as well as to create high bandwidth interconnections and a low-cost and power-efficient system. In particular, the incorporation of optical tunable transmitters (T-TXs) and passive optical beam steering technologies is a promising way to build an OW-DCN benefitting from the potential of fast optical switching speed, low switch control complexity, and easy reconfiguration. However, the practical deployment of such an OW-DCN remains a challenge as fast (nanosecond) T-TX is required for fast optical switching operation. Implementation of fast T-TX can be realized by an array of lasers and optical gates, which are combined with photonic integration technology to achieve a compact, stable, and efficient nanosecond T-TX. In this paper, we propose an OW-DCN based on arrayed waveguide grating routers and fast T-TXs that exploit photonic integrated circuit multicast switches (PIC-MCSs). This PIC-MCS chip not only offers nanosecond-scale fast optical switching but also plays an essential role in enabling multicast operation, T-TX sharing, and dynamic bandwidth allocation between the intra- and inter-cluster networks. A 4×2 PIC-MCS has been designed, fabricated, and characterized in this proposed OW-DCN system. Experimental results validate that the proposed OW-DCN supports lossless, nanosecond, and multicast switching operation. Moreover, the dynamic bandwidth allocation and optical packet switching capability have been experimentally demonstrated. Finally, system performance with this fabricated PIC-MCS chip in a 4×4 rack OW-DCN is experimentally validated for different transmission scenarios and modulation formats. Wavelength division multiplexing multicast transmission with 50 Gb/s non-return-to-zero on–off-keying signals has been verified with less than 1.5 dB power penalty. 58 Gb/s four-level pulse-amplitude modulation transmission has also shown operation below the forward error correction threshold of 3.84×10−3 for all the different transmission scenarios.