Optical packet switches that scale to thousands of input/output ports might find their application in next-generation datacenters (DCs). They will allow interconnecting the servers of a DC in a flat topology, providing higher bandwidth and lower latency in comparison with currently applied electronic switches. Using a simple analytic model that allows computing end-to-end latency and throughput, we show that optical interconnects that employ a centralized (electronic) controller cannot scale to thousands of ports while providing end-to-end latencies below $1\mathbf{\mu }\mathrm{s}$ and high throughput. We therefore investigate architectures with highly distributed control. We present a strictly non-blocking wavelength division multiplexing architecture with contention resolution based on wavelength conversion. We study the packet loss probability of such architecture for different implementations of the contention resolution functionality. Furthermore, we show that the proposed architecture, applied in a short link with flow control, provides submicrosecond end-to-end latencies and allows high load operation, while scaling over a thousand ports.