Design of delay-line buffers for asynchronous optical packet switched networks

Optical buffering is one major challenge in realizing all-optical packet switching. In this paper we focus on a delay-line buffer architecture, called a Multiple-Input Single-Output (MISO) buffer, which is realized by cascaded fiber delay lines (FDLs). We consider the MISO buffers in a network scenario where the incoming packets are asynchronous and of fixed length. Instead of matching the fixed packet length, the length of basic FDL is adjusted to minimize the packet loss under different scenarios. A novel Markov model is proposed to analyze the performance of our buffering scheme, in terms of packet loss ratio, average packet delay and the output link utilization. Both simulation and analytical results show that the optimal basic FDL length is equal to the fixed packet length under low system load. However, under high system load, the basic FDL length is much smaller than fixed packet length for minimum packet loss. In addition, this paper gives clear guidelines for designing optimal basic FDL lengths under different network scenarios. It is noticeable that this optimal length value is independent of the buffer sizes.