Abstract

It is now established that the long term mechanical reliability of fused silica optical fiber can be determined by surface etching of the fiber that results in roughness that acts as a source of strength degrading defects.^1,2 This suggests that suppression of surface dissolution should have a beneficial effect on fiber reliability. In previous work^3,4 this was achieved by incorporating in the coating colloidal silica particles which then, presumably, dissolve preferentially due to their higher solubility and reactivity and so protect the fiber sacrificially. It was found that the static fatigue lifetime could be increased by up to a factor of 30 in liquid water by just 0.75 wt% of colloidal silica. However, this first such fiber exhibited two undesirable properties due to the crudity of the preparation techniques; there was large scatter in the fatigue data and the tensile strength showed a low strength mode. This paper shows that, by careful production of the coating, the disadvantages of the earlier fiber can be avoided, and that even more dramatic improvements in lifetime can be achieved. It is also shown that the coating additive is effective in vapor as well as liquid aqueous environments.

© 1993 Optical Society of America