The traffic volume processed within the datacenter increases exponentially. In a typical datacenter, top-of-rack (ToR) switches connected to servers are interconnected via multi-stage electrical switches. The electrical switches require power-consuming optical-to-electrical and electrical-to-optical conversion. To resolve the problem, a single optical switch needs to be introduced to offload large-capacity flows. The optical switch in the datacenter must have a large number of input/output ports to support many ToR switches. The combination of delivery-and-coupling (DC) switches and wavelength-routing (WR) switches comprised of 1xN non-cyclic arrayed-waveguide gratings (AWGs) can attain high-port-count switches. To further increase the port count, the system loss must be reduced or higher-power transmitters must be used. To overcome this difficulty, we propose novel optical-switch architecture in which nxN uniform-loss and cyclic-frequency (ULCF) AWGs are utilized for the WR-switch part, where the system loss can be reduced by the factor of n. To confirm the effectiveness of our proposal, 12x48 ULCF AWGs were newly fabricated with planar-lightwave-circuit (PLC) technology. Part of a 1,536x1,536 optical switch was constructed, and good transmission performance was experimentally confirmed by bit-error-ratio measurements in 96-wavelength 32-Gbaud DP-QPSK signals in the full C-band. The throughput was 153.6 Tbps.