Fracture and abrasion resistance tests for optical fiber coatings

The properties of the optical fiber buffer coating play a critical role in the strength and handleability of optical fibers. Tests have been developed to measure a coating's resistance to mechanical damage. Two such tests are described here. The indentation rupture test involves indenting coated fiber with diamond pyramids and measuring the load at which the pyramid punctures the coating. Finite element analysis is used to determine the strain energy absorbed by plastic deformation of the coating. The toughness of the outer coating layer and the toughness of the inner coating/glass interface can be determined from the crack dimensions produced during rupture of the coating. Strength after mechanical abrasion is a procedure wherein a hollow tube of coating is removed from an optical fiber and subsequently bombarded with an abrasive grit. The effects of the abrasion event are measured by a tensile test of the tube. Results for both tests are obtained for two coating systems. The validity of the tests for measuring coating properties is discussed.