Gain Equalization versus Electrical Regeneration Tradeoffs in Hybrid WDM Networks

The evolution of optical network devices such as optical cross-connects and optical amplifiers has provided a huge increase in the transmission capacity of optical links. However, this evolution also brings problems such as the large power imbalance arising with the transmission of several wavelengths that imposes a severe degradation to the optical signal. Recent research work shows how to adapt all-optical (transparent) WDM networks to cope with transmission impairments induced by long-haul optical components on long spans. Since no electrical 3R regeneration is performed at intermediate nodes in a transparent network, transmission impairments accumulate along the signal route and may result in high BER values at the receiver´s side. Since they provide sparse regeneration, hybrid WDM networks are considered as a promising solution to overcome the transmission impairments and achieve performance measures close to those obtained by fully opaque networks at a much lesser cost. In previous work, we addressed the design of hybrid WDM network and proposed a novel tool for routing, wavelength assignment, and regenerator placement so that the quality of transmission is guaranteed. Up to now, we did not consider any in-line gain equalization scheme, i.e. dynamic gain equalizers are only deployed at the network nodes. In this paper, we investigate the impact of deploying in-line dynamic gain equalizers in terms of the number of required regenerators to meet QoT and in terms of cost tradeoff. We also propose a novel wavelength assignment strategy that takes into account the quality of transmission.