In this paper, the potential benefit of migrating from static to dynamic operation of WDM optical networks is quantified (in terms of wavelength requirements) for shared mesh protection schemes under single-cable failure scenarios. The static network cost (wavelength requirements) is quantified by applying a variation of the heuristic proposed in . The dynamic network cost is quantified by extending the mathematical dimensioning method proposed in  and modifying the simulation method proposed in . Results show that fault-tolerant (FT) networks without wavelength conversion benefit from dynamic operation only at low traffic loads (< 0.4). Wavelength-convertible FT dynamic networks instead require a significantly lower total number of wavelengths than the FT static networks in a wide range of traffic loads (< 0.7). Even more, the savings achieved by the dynamic operation (with respect to the static approach) when fault-tolerance capability is provided are much more significant than when such capability is not considered. We expect these results will help network operators to better understand and design future dynamic optical networks.