Scheduling algorithms for shared fiber-delay-line optical packet switches - Part I: The single-stage case

Soung Y. Liew, Gang Hu, H. Jonathan Chao

Research output: Contribution to journalArticlepeer-review


In all-optical packet switching, packets may arrive at an optical switch in an uncoordinated fashion. When contention occurs, fiber delay lines (FDLs) are needed to delay (buffer) the packets that have lost the contention to some future time slots for the desired output ports. There have been several optical-buffered switch architectures and FDL assignment algorithms proposed in the literature. However, most of them either have high implementation complexity or fail to schedule in advance departure time for the delayed packets. This paper studies the packet scheduling algorithms for the single-stage shared-FDL optical packet switch. Three new FDL assignment algorithms are proposed, namely sequential FDL assignment (SEFA), multicell FDL assignment (MUFA), and parallel iterative FDL assignment (PIFA) algorithms for the switch. The proposed algorithms can make FDLs and output-port reservation so as to schedule departure time for packets. Owing to FDL and/or output-port conflicts, the packets that fail to be scheduled are discarded before entering the switch so that they do not occupy any FDL resources. It is shown by simulation that with these algorithms, the optical-buffered switch can achieve a loss rate of ∼ 10-7 even at the load of 0.9. These algorithms are extended to the three-stage Clos-network optical packet switches in the companion paper.

Original languageEnglish (US)
Pages (from-to)1586-1600
Number of pages15
JournalJournal of Lightwave Technology
Issue number4
StatePublished - Apr 2005


  • All-optical network
  • Fiber delay line (FDL)
  • Optical packet switching
  • Scheduling algorithm

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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