Fiber optic cable is one of the more important components of the material, to improve the life of the cable, the fundamental thing is to improve the life of the fiber. Factors affecting the service life of the optical fiber are: microcracks and the presence of the surface of the fiber to expand; atmosphere water and water vapor molecules to the surface of the fiber etching; remaining cable laying down unreasonable long-term effects of stress and the like.
For the above reason, such silica glass-based optical fiber decreases mechanical strength, attenuation increases gradually, so that after a fiber break, the service life of the cable termination.
Since there will always be a micro-cracks on the fiber surface, slow crack growth occurs in the atmosphere, so that cracks continue to expand, so that mechanical strength of the optical fiber is gradually reduced. For example, after a three-year slow change in a 125 μm diameter quartz fiber, the tensile strength of the fiber is reduced from 180 kpsi (equivalent to 1530 g tensile strength) to 60 kpsi (equivalent to 510 g tensile strength).
The principle of the optical fiber's mechanical strength reduction caused by this slow change is that when there are micro-cracks (or defects) on the surface of the optical fiber, they will not break immediately when subjected to external stress. fiber will break. When the quartz fiber receives a constant stress that is less than the critical value, the surface crack will slowly expand, so that the crack reaches the critical value of fracture, which is the process of fiber mechanical strength degradation. The degradation of the mechanical strength of quartz fiber is caused by the combined effect of the stresses and the erosion of water and water vapor molecules in the atmospheric environment.
