An edge data center (EDC) network infrastructure is required to flexibly deliver massive bandwidth and ultralow latency for a 5G edge cloud. Existing electrical-switching-based infrastructure, however, has been shown incapable of meeting such requirements. In this paper, we present an EDC network architecture and prototype testbed, referred to as the intelligence-defined optical tunnel network system (OPTUNS). OPTUNS consists of a set of optical switching subsystems that operate collectively to facilitate packet transport through logical wavelength-based optical tunnels. These optical tunnels are governed by a software-defined-networking-based intelligent tunnel control system, in a proactive manner. As such, optical tunnels are always made available whenever needed. In essence, OPTUNS boasts several crucial features, including high scalability, massive wavelength reuse (yielding high bandwidth), proactive optical tunnel control (yielding ultralow latency), and fault tolerance. We have built an OPTUNS testbed, including 30 optical switching subsystem prototypes, that interconnect a total of 25 racks (400 servers). Benchmarking results show that OPTUNS achieves 82.6% power saving compared with electrical spine-leaf networks. Further, our NetPipe-based experimental results show that OPTUNS invariably achieves mean and p99 end-to-end latencies of less than 17 μs, regardless of traffic load and locality.