Exploiting AWG Free Spectral Range Periodicity in Distributed Multicast Architectures

TL;DR

This paper proposes a multi-FSR scheduling algorithm for AWG-based optical switches, demonstrating that exploiting multiple free spectral ranges enhances capacity and reduces blocking, with diminishing returns beyond four FSRs.

Contribution

It introduces a novel multi-FSR scheduling algorithm and an analytical framework for capacity analysis in AWG multicast architectures, addressing capacity bottlenecks.

Findings

Significant capacity improvements with moderate FSR increases

Diminishing returns beyond four FSRs

Cross-layer analysis shows increased bit rate per port

Abstract

Modular optical switch architectures combining wavelength routing based on arrayed waveguide grating (AWG) devices and multicasting based on star couplers hold promise for flexibly addressing the exponentially growing traffic demands in a cost- and power-efficient fashion. In a default switching scenario, an input port of the AWG is connected to an output port via a single wavelength. This can severely limit the capacity between broadcast domains, resulting in interdomain traffic switching bottlenecks. In this paper, we examine the possibility of resolving capacity bottlenecks by exploiting multiple AWG free spectral ranges (FSRs), i.e., setting up multiple parallel connections between each pair of broadcast domains. To this end, we introduce a multi-FSR scheduling algorithm for interconnecting broadcast domains by fairly distributing the wavelength resources among them. We develop a general-purpose analytical framework to study the blocking probabilities in a multistage switching scenario and compare our results with Monte Carlo simulations. Our study points to significant improvements with a moderate increase in the number of FSRs. We show that an FSR count beyond four results in diminishing returns. Furthermore, to investigate the trade-offs between the network- and physical-layer effects, we conduct a cross-layer analysis, taking into account pulse amplitude modulation (PAM) and rate-adaptive forward error correction (FEC). We illustrate how the effective bit rate per port increases with an increase in the number of FSRs. %We also look at the advantages of an impairment-aware scheduling strategy in a multi-FSR switching scenario.