Humidity and temperature-dependence of the interfacial shear strength between the glass fiber and primary coating in double-coated optical fibers

The dependence of the interfacial shear strength between the glass fiber and primary coating in double-coated optical fibers on humidity and temperature is experimentally investigated. The interfacial shear strength is determined from the mechanical stripping force. The effect of humidity on the interfacial shear strength is governed by the diffusion of water vapor through the polymeric coatings to the interface between the glass fiber and primary coating. After several days, the diffusion of water vapor reaches a steady state. The degradation of the interfacial shear strength is unrelated to the total amount of water vapor in the polymeric coatings, does depend on the amount of water vapor on the glass/polymer interface. Consequently, the degradation of interfacial shear strength caused by the humidity is proportional to the squared cube-root of the water vapor pressure. Results of this study demonstrate that the relationship between the fiber strength and the humidity resembles that between the interfacial shear strength and the humidity.