To determine the relationship between power loss and crack width theoretically in distributed optic-fiber crack detection technology. The classical theoretical model of bend loss was modified by correcting curvature radius in this paper. The application range of classical theoretical model was extended and mechanics-optics coupling theory of distributed optic-fiber crack detection technology was completed. Numerical experiments and model experiments were carried out for 4 cases which involve two fiber types and two angles between fiber and crack. The results show that the thinner the fiber sheath and the smaller the angle between fiber and crack, the higher the sensitivity is. The numerical results are consistent well with experimental results, demonstrating that this modified model is effective and can be used as a theoretical tool for developing the distributed optic-fiber crack detection technology.
