Abstract: Tunnel convergence deformation is the key points of monitoring，serves as a critical indicator of the interaction
between surrounding rock and supporting structures, directly reflecting rock mass stability and the mechanical performance of the support system. Accurate and real-time monitoring of this deformation is essential, especially under the complex geological conditions. However, conventional monitoring techniques, which primarily rely on manual measurements and simple instruments, often fall short in precision and continuity. Distributed optical fiber sensing technology, with its advantages such as long distance, good durability, strong anti-interference ability and the ability to achieve real-time monitoring, provides a new technical means for the precise monitoring of tunnel convergence deformation. This study presents a novel method for distributed fiber optic sensingbased monitoring of tunnel circumferential convergence, incorporating an optimized cable deployment strategy and a strain-todisplacement inversion algorithm. Laboratory model tests were conducted to validate the feasibility and accuracy of the proposed approach. The results demonstrate that the method can effectively identify deformation zones and assess the overall stress distribution based on strain profile analysis. The use of a dual-cable layout minimizes computational assumptions and enables direct conversion of strain data into point displacements, offering high efficiency and reliable accuracy. The monitoring accuracy is primarily influenced by the design and installation quality of the sensing setup. Enhancements in device stability, reduction of optical loss, and improved fixation techniques are shown to further increase measurement precision. The findings provide a novel approach for refined monitoring of tunnel deformation under complex geological conditions. 

Key words: tunnel monitoring, convergence deformation, distributed fiber optic sensing technology, inversion model;
experimental study