Contention arises in optical packet/burst switching systems when multiple incoming optical packets contend for the same output wavelength channel at the same time. The most popular approach for contention resolution is the use of wavelength converters. For economical reasons, it is cost-effective to share wavelength converters as opposed to dedicating a converter for each outgoing wavelength channel. This talk describes four shared wavelength conversion architectures to be used in asynchronous optical packet/burst switches with variable-sized optical packets, namely Shared-Per-Link (SPL), Shared-Per-Node (SPN), Shared-Per-Input-Wavelength (SPIW), and Shared-Per-Output-Wavelength (SPOW). Exact (in the case of SPL) and approximate (SPN, SPIW, and SPOW) analytical models are developed for performance analysis of such architectures in the case of Poisson packet arrivals and exponential optical packet lengths. The main tools that we use are Markov chains, block-tridiagonal LU factorizations, and fixed-point iterations to cope with the curse of dimensionality arising in large systems. Based on our findings, we provide guidelines for architecture selection and for dimensioning converters.

Nail Akar received the B.S. degree from Middle East Technical University, Ankara, Turkey, in 1987 and M.S. and Ph.D. degrees from Bilkent University, Ankara, Turkey, in 1989 and 1994, respectively, all in electrical and electronics engineering. From 1994 to 1996, he was a visiting scholar and a visiting assistant professor in the Computer Science Telecommunications program at the University of Missouri, Kansas City. He joined the Technology Planning and Integration group at Long Distance Division, Sprint, Overland Park, Kansas, in 1996, where he held a senior member of technical staff position from 1999 to 2000. Since 2000, he has been with Bilkent University, currently as an associate professor. Throughout the first half of 2010, he is conducting research on performance evaluation of telecommunication networks and queueing systems at the School of Computing and Engineering, University of Missouri , Kansas City as a Fulbright visiting research scholar. He has recently been active in the European Union funded network of excellence project BONE (Building the Future Optical Network in Europe) with his work on optical packet/burst switching. His current research interests include performance analysis of computer and communication networks, optical networks, queueing systems, traffic control and resource allocation.