We describe a testbed to study both the theoretical aspects and physical implementation issues associated with high-bit-rate, multihop, packet-switched OTDM networks. We have found that using optical time-division-multiplexed (OTDM) techniques can greatly increase the bandwidth of a single-wavelength channel. Ultrafast OTDM networks are excellent candidates for meeting the system requirements for massively parallel processor interconnects, which include low latency, high bandwidth, and immunity to electromagnetic interference. High-bit-rate transparent optical networks (or TONs) for multiprocessor interconnects will be best realized with an OTDM network architecture. To fully use the bandwidth of optical fiber, we spaced the picosecond pulses closely together (about 10 ps) and typically applied a return-to-zero modulation format. While the total capacity of TDM and wavelength division multiplexing (WDM) networks may essentially be the same, TDM systems have better throughput delay performance. They also have faster, single-channel access times for high-data-rate end users such as HDTV video servers, terabyte-media data banks, and supercomputers.