Analysis of the failure characteristics of the optical fiber coating in fiber optic microbend sensors

A laboratory testing and engineering modeling analyses was conducted to study the damage caused on the optical fiber coating by the contact between the optical fiber and deformer. The study also determined the effect of this damage on the performance of microbend sensors. A testing method was designed, developed and implemented to determine the load and displacement magnitudes that caused optical fiber glass-coating debonding as well as coating fracture on the multimode optical fiber.; Hertzian and finite element models of the fiber-deformer system were developed to study the failure modes of the coating and predict the stresses that produced failure. Loads and system displacements predicted by finite element models were found to be in good agreement with load and displacement values observed during the experimental analyses. However, Hertzian models could not represent accurately the fiber-deformer system behavior.; It was found that optical fiber coating physical damage caused by contact, such as coating delamination and fracture does not affect the recovery of the light transmissivity properties of the optical fiber. After coating failure, contact between deformer and glass (core and cladding) occurred, resulting in noticeably greater light transmissivity losses. Viscoelastic effects were found to influence the behavior of the fiber-deformer system. It was also found that glass-coating debonding and coating fracture during a load-unload cycle are major causes of variability and error during microbend sensor calibration.