Dimensioning shared-per-node recirculating fiber delay line buffers in an optical packet switch

Abstract

Optical buffering based on fiber delay lines (FDLs) has been proposed as a means for contention resolution in an optical packet switch. In this article, we propose a queuing model for feedback-type shared-per-node recirculating FDL optical buffers in asynchronous optical switching nodes. In this model, optical packets are allowed to recirculate over FDLs as long as the total number of recirculations is less than a pre-determined limit to meet signal loss requirements. Markov Modulated Poisson Process (MMPP)-based overflow traffic models and fixed-point iterations are employed to provide an approximate analysis procedure to obtain blocking probabilities as a function of various buffer parameters in the system when the packet arrival process at the optical switch is Poisson. The proposed algorithm is numerically efficient and accurate especially in a certain regime identified with relatively long and variably-sized FDLs, making it possible to dimension optical buffers in next-generation optical packet switching systems. © 2013 Elsevier B.V. All rights reserved

Blocking Probability Simulations for FDL Feedback Optical Buffers

“…2), we know that each packet that circulates the loops suffers from transmission losses and optical noise. These are physical layer impairments caused by losses in FDLs, optical switches, and arrayed waveguide gratings (AWGs), amplified spontaneous emission (ASE) noises in optical amplifiers, and crosstalk noises in AWGs [14][15][16]. Wavelength selective optical switches constructed by many tunable wavelength converters (TWCs) and AWGs, for example, generate both ASE and crosstalk noises.…”

“…For a cost-efficient packet switch architecture, a share-per-node optical FB butter configuration has been proposed and has been extensively investigated [8,[14][15], where FDLs are shared among the output ports of a node in a feedback configuration. The shared-per-node configuration utilizes the output buffering strategy in the same way as a shared-per-port optical buffer configuration does, where each output port has its own dedicated buffer.…”

“…Generally speaking, for the FB buffers, there has been insufficient theoretical investigation of both blocking probabilities and delays. Simulations [4,[6][7][8], an approximation for the FB buffer with one FB loop [6], and numerical iterations [12,[14][15] have been performed, but the characteristics of the multi-re-circulation-loop FB buffers with general packet-length distributions have not yet been clarified. Basically, in queueing networks, the existence of feedback loops makes the stochastic processes more complex and difficult to solve [20,21].…”