A collision-avoidance WDM optical star network

Wavelength-Division Multiplexing (WDM) offers the potential to support many concurrent transmissions on a single optical fiber. However, for multiuser packet communications with unpredictable user demands (e.g., in a local or metropolitan area network), the coordination and control of access to the WDM channels is difficult. With tunable transmitters and fixed-tuned receivers, the Protection-Against-Collision (PAC) circuit solves this media access problem by allowing a packet access to the network only if the destination channel is available. In geographically-distributed applications the maximum achievable throughput (normalized to the transmission rate) is typically between 0.4 and 0.5 per channel. In a centralized switch, the (normalized) maximum achievable throughput can approach 0.8 per channel.