Distributed resource scheduling in not-aligned optical cell switching

Abstract

Most all-optical switching paradigms assume that different wavelengths are switched independently, which limits scalability. In optical cell switching (OCS), time is divided into time slots of fixed size by time-division multiplexing, and the wavelengths in a time slot are all bundled. Thus, each OCS switch (OCX) has a single switching plane and performs mere time-space switching. In OCS, each OCX requires optical slot synchronizers (OSYNs) at all inputs for the arrival slots to be aligned, so that cells can be simultaneously forwarded. In a recent OCS paradigm -not-aligned OCS-, the OSYNs and the alignment process are no longer required. Cell shifting still takes place inside the OCXs for minimizing the gaps between cells, but it is not necessary to align them to a reference time. Not-aligned OCS has clear advantages over aligned OCS: the total number of fiber delay loops (FDLs) and the hardware cost are reduced, and the number of switching operations is also lower. Moreover, cell arrival time to the switch is not critical, and the network becomes simpler and more flexible. In this paper, we propose a new distributed resource scheduling algorithm for not-aligned OCS networks, which takes connection blocking probability to reasonable values for practical loads.