Analysis of optical fiber failures under bending and high power

The failure of tightly bent optical fiber under high optical power is observed dynamically with fine time resolution and explained in terms of the behavior of the polymer coating and underlying glass. An abrupt rise in coating temperature stimulates the viscoelastic deformation of the glass. The abrupt bending of the glass is explained by the ability of highly quenched silica to deform at low temperatures. There is no evidence of thermal runaway of the glass core. Coating decomposition is self limiting with no visible flame.