Performance limitations of multiwavelength interoffice ring networks

Summary form only given. SONET technology has made high speed self-healing ring architectures practical and economical for interoffice network applications. Self-healing ring networks using electronic add-drop multiplexers (SONET ADMs) are limited in capacity to about 10 Gb/s by the electronics. Elrefaie (1993) proposed a multiwavelength interoffice ring architecture for high capacity transport applications. Two types of multiwavelength ring have been proposed: one uses two fibers and the automatic protection switching capability of standard uni-directional SONET ADMs; the other uses four fibers together with a new capability for automatic protection using optical switching and uni-directional SONET ADMs. Both can be designed to be consistent with present SONET standards, allowing graceful upgrades from electronic SONET rings to multiwavelength SONET rings. In multiwavelength interoffice ring networks, WDM signals traverse a cascade of erbium-doped fiber amplifiers (EDFAs), each followed by optical drop-and-insert multiplexers. The amplifiers´ non-flat gain spectra impose size and capacity limits that depend on the network types and the specific drop-and-insert arrangements of the network. Also, WDM signals pass through a number of concatenated optical filters which leads to network performance degradations due to laser and filter passband misalignments arising from device imperfections and temperature variations. The paper evaluates the accumulation of performance degradations in multiwavelength interoffice ring networks. The author also suggests several techniques to overcome performance degradations of multiwavelength networks.