Transparent optical packet switching: the European ACTS KEOPS project approach

Abstract

This paper reviews the work carried out under the European ACTS KEOPS (KEys to Optical Packet Switching) project, centering on the definition, development and assessment of optical packet switching and routing networks capable of providing transparency to the payload bit rate. The adopted approach uses optical packets of fixed duration with low bit rate headers to facilitate processing at the network/node interfaces. The paper concentrates on the networking concepts developed in the KEOPS project through a description of the implementation issues pertinent to optical packet switching nodes and network/node interfacing blocks, and consideration of the network functionalities provided within the optical packet layer. The implementation, from necessity, relies on advanced optoelectronic components specifically developed within the project, which are also briefly described.

Parallel desynchronized block matching: A feasible scheduling algorithm for the input-buffered wavelength-routed switch

“…For this purpose, a fiber delay line of a sufficient length is used at every input port. TWC devices with tuning times on the order of nanoseconds have been demonstrated [9]. Scheduling algorithms on the order of tens of nanoseconds would lead to short fiber delays (or even no delays at all).…”

“…On the other hand, the hardware complexity of the IBWR architecture is much lower than the one for the output buffered proposals. Table I illustrates the cost side of this complexity vs. performance trade-off, for three prominent OPS output buffered architectures: the KEOPS switch [9], the Output-Buffered Wavelength-Routed switch [3] and the space switch [8]. The comparison involves switch fabrics of N input and output fibers, n wavelengths per fiber and M buffer positions.…”

“…The major benefits and interest of the IBWR architecture lay in the lower cost and better scalability of its hardware, when compared to OPS architectures capable of emulating output buffering [3][8] [9]. These are switch fabrics for which delay allocation is only constrained by the (unavoidable) output fiber contention.…”

Architectures and Buffering for All-Optical Packet-Switched Cross-Connects

“…The synchronisation of optical packets can be done using switchable delay lines for the coarse synchronisation, and wavelength converters with dispersive fibre for the fine synchronisation. This complex functionality has not been demonstrated without electronic control [38,39].…”

Enhanced Parallel Iterative Schedulers for IBWR Optical Packet Switches

“…The scheduler assigns output wavelengths to the packets when they leave the switch, according to the round-robin criterion. Remark: Other OPS architectures, with higher hardware costs and less scalable than IBWR, emulate output buffering (OB) [6] [7] (the only factor limiting packet delay assignment is output fiber contention).…”