Because of the very high optical fiber's capacity, prompt and unambiguous fiber cut detection is mandatory to guarantee carriers' network survivability. In this matter, the monitoring-cycle and the monitoring-trail mechanisms have been proposed in the recent literature. In this paper, we propose the innovative concept of monitoring-tree that enables to reduce considerably the monitoring cost while keeping unambiguous single fiber cut detection and localization. We propose an ILP formulation aiming at mapping a monitoring-tree onto a mesh topology. Applied to real networks, we show that our approach outperforms its counterparts.