A cooperation control between Look-ahead Buffer and Loop-back Buffer in two-stage variable optical packet Switch

Programmable variable delay lines have been developed, so as to delay packets in variable durations by combining several lengths of FDLs in optical packet switch. In practice, two-stage switch with this programmable variable delay lines has been proposed. This switch has two buffers. One is the programmable variable delay lines (look-ahead buffer). The other is the fixed FDLs that re-input a packet from the output to the input (loop-back buffer). The switch can foresee following packets and avoid contentions effectively by using two buffers. However, existing studies only focus on the look-ahead buffer and intelligent usage of the loop-back buffer is actually out of concern. In this paper, a packet transfer scheduling method in the two-stage switch is proposed. The proposed method controls both the look-ahead buffer and the loop-back buffer cooperatively and improves the utilization of the switching process. The proposed method uses the loop-back buffer systematically and distributes traffics in the whole switch. The effectiveness of the proposed method is evaluated through simulation experiments.