Berceli Tibor

Kozlovszky Miklós

University of Szeged

Optical delay buffer optimization in packet switched opticalnetworkMiklós Kozlovszky and Tibor BerceliNowadays the delay sizing and optimization within all-optical networks is one of the mostcrucial points in the field of optical network communication. The information in al-optical net-works is transformed to light and transmitted with the help of optical waves. We are currentlyinvestigating optical buffers that could meet the requirements of high speed/low latency com-munication within these networks. The information in such systems is traveling with the speedof light, but in the active nodes it is very likely experiencing delay, due traffic congestion, pathswitching or just because of hardware processing time. During delay in the network node, theinformation can not be stored and restored easily as we can do in „normal” electrical networks.During operation, light signal can not be stopped, and the electrical-optical (OEO) conversiontakes huge amount of time comparing with the communication speed in such networks. As aresult, the information should remain in form of optical waves all the time. To artificially in-troduce delay for the information in the network node we could use optical delay buffers. Wecan define the optical buffer as a device with both its input and output data streams in opticalformat without optical-electrical-optical conversion.In the first section of the paper we give a short overview how to introduce time delaysin the network nodes, what kind of optical delay elements are available and what are theirbasic characteristics. After that we focus on one widely used solution, namely the usage of thesimple and cost effective optical delay line. The simplest implementation of an optical delayline is introducing a physical distance, such as a length of optical fiber, or free space. Althoughsimple this implementation suffers from two drawbacks; significant tenability is difficult toachieve, and long time-delays require large physical distances. In the paper we will describefully the basic symptoms of the usage of optical delay lines.In the next section we compare the „normal” electrical delay buffers to optical delay buffers.Show the differences in latency and throughput and usable buffer sizes. With the help our in-vestigation we introduce and build up an optical delay buffer model which can help hardwaremanufacturer to make accurate sizing and optimization of the optical buffer according to thesystem needs. According to our theoretical approach and simulations we optimize multistageoptical delay line structures, to handle delay problems with multiple in/output channels. Inthe next section we give formal description and functional model of the proposed optical delaybuffer.We have carried out various simulations with network simulation software, to analyze theproposed delay buffer model and to make the functional analysis of such system. To searchfor the highest throughput, and minimize latency during network communication, we haveworked with single and multistage optical delay buffer simulations as well. The major topicsinvestigated include: latency evolution during single and multistage buffer usage, optimalbuffer sizes for different data communication speed and variable packet sizes. In the last sectionof the paper we discuss the performance results of simulations and draw conclusions on ouroptical delay buffer model.Keywords: all-optical network, optical delay line, modeling, optical buffer66

Optical delay buffer optimization in packet switched optical network : [abstract]

http://acta.bibl.u-szeged.hu/59867/1/cscs_2006_066.pdf

Optical delay buffer optimization in packet switched optical network

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