Photonic Ring and Bus Networks with Reduced Station Hardware

Recent advances in photonic amplification have re-motivated the use of ring and bus topologies in single-hop wavelength division-multiplexed (WDM) networks [1]. The use of WDM offers a significant increase in capacity over traditional single-channel networks. However, the parallel channel nature of these networks tends to complicate both the media access protocols and hardware requirements of the user stations, [1] and [2]. In this paper, four different WDM bus/ring networks are considered. All four have user station hardware designs with various reductions in the number of tapping points, number of transmitters and receivers and their tunability requirements. With each reduction in hardware, protocol complexities and performance reductions are introduced. In all cases, dynamic packet-switched operation is achieved. The designs thus give an indication of the cost/performance tradeoffs which are possible as the amount of hardware is reduced at the user stations. Common to each of the designs is the use of a headend controller which attaches to each WDM channel. Media access is achieved through information provided by the controller. In the more hardware intensive designs, media access is achieved through a mini-slot contention mechanism [3]. The remaining designs rely on a hybrid opto-electronic request/allocation protocol motivated by DCCN [4]. Analytical models are presented which are validated through discrete-event simulations for each design.