The inherent imprecision that appears in the data involved in real-world problems can have different natures: random,subjective, vague, etc. If the goal is to tackle the problem at hand without altering its inherent nature, what seems more desirable is to consider the approach that fits the best to the origin of the imprecision, either stochastic, interval-based or fuzzy. Among these possibilities, the imprecision considered in this paper when designing WDM networks is not random but linguistical and therefore vague (for instance, “the demand will be large”). Although vague information appears in this real-world application, to the best of our knowledge, this is the first work that considers this nature of imprecision when designing WDM networks. Other imprecision natures are out of the scope of this paper.