Impact of wavelength assignment strategies on hybrid WDM network planning

Most studies carried out in the field of RWA in WDM networks assume an ideal optical medium. However, throughout its route an optical signal undergoes many transmission impairments introduced by long-haul optical components. In all-optical WDM networks, where no electrical 3R regeneration is performed at intermediate nodes, transmission impairments accumulate and may result in high BER values at the receiver's side. Hybrid WDM networks use sparse regeneration to overcome transmission impairments. Such networks achieve performance measures close to those obtained by fully opaque networks at a much lesser cost. In previous work, we addressed the problem of hybrid WDM network design by proposing a tool for routing, wavelength assignment and regenerator placement so that the physical constraints are taken into account. A standard First-Fit scheme is performed for the wavelength assignment problem. In recent work, we proposed a QoT-aware wavelength assignment strategy that considerably improves the performance achieved by our tool. In this paper, we propose a new wavelength assignment strategy called Best-BER-Fit. The Best-BER-Fit strategy chooses the first available wavelength that guarantees the quality of transmission required to establish the lightpath. The studied strategy is compared to the First-Fit and Min-BER-Fit strategies in terms of the number of required regenerators.