Abstract

Optical packets should allow to increase the efficiency of optical networks because their smaller granularity compared to optical circuits improves the use of the optical resources. However, optical circuit can already take advantage of forward error correcting codes (FEC) like the one defined in the ITU-T G.975 standard.¹ FECs allow to design systems at a lower optical signal-to-noise ratio (OSNR) and hence either to increase the performance (e.g.: propagation distance or number of wavelengths) or to use cheaper components. Hence, to be competitive, optical packets will also require FEC. However, because of their short duration optical packets may require a dedicated FEC. We will only consider fixed-duration (or time-slotted) optical packets which are best suited to avoid high logical packet loss rate due to packet contention in optical switching matrices.² In the following, we will first present the constraints for the choice of an FEC for optical packet. We then consider the main classes of FEC and we will show that Reed-Solomon FEC are among the best suited for optical packets. We finally show how to choose the correct parameters of the Reed-Solomon FEC. Among the conclusions, we show that the standard RS(255, 239) according to G.975 is not convenient for short optical packets.

© 2002 Optical Society of America