Recent advances in WDM technology enable an optical fiber to carry up to 200 wavelengths operating at 40 Gbps each. In such networks, service disruptions caused by network faults (e.g., fiber cut, amplifier dysfunction) may lead to high data losses. Therefore, it is mandatory for a network operator to be able to detect and localize such faults in the lowest possible delays. Fault detection and localization in meshed WDM networks have been deeply investigated in the literature. Numerous schemes, both exact and approximate, have been proposed to achieve fast and accurate failure localization. In this paper, we propose an original Meta-heuristic for Monitoring Trail Assignment (MeMoTA). We show through numerical results that MeMoTA provides monitoring solutions closer to optimal than existing heuristic approaches while ensuring an acceptable scalability.