Protection-against-collision optical packet network

An optically transparent packet network controlled by a simple medium access circuit is presented. The system, based on frequency division multiplexing and tunable transmitters, has no internal blocking and is optically self-routing. It provides internal collision-free traffic by allowing access to the network only if the addressed channel (output port) is available. A packet denied access to the network is reflected back to its input port, which is thus informed of the packet status. Therefore, the traffic is not bogged down by acknowledgments between input and output ports. To achieve this result, each input of the network is controlled by a protection-against-collision (PAC) circuit located at a central hub. The PAC circuit uses the packet for probing the energy present in the addressed channel. The resulting signal controls an optical switch connecting the input port to the network. Thus, full optical connectivity is provided between ports controlled by electrical signals derived from simple optical power measurements