Packet scheduling in optical FIFO buffers

Recent advances in optical technology show the possibility of building all-optical buffers in the near future. These buffers are usually composed of a number of fiber delay lines (FDLs) and optical switches. Incoming packets are stored for a limited time by going through optical delay lines. Optical switches transfer these packets among different delay lines, or send them towards the output line if a packet is to leave the system. As a direct consequence of using optical technology, one of the major constraints in this setting is that the size of switch needs to be small. In this paper, we show the feasibility of constructing a FIFO queue of size N by using only O(log N) 2x2 switches. A simple scheduling algorithm that achieves this bound is developed. The proposed structure provides an efficient way of storing optical packets using a minimal number of delay lines and switches.