OPTICAL-FIBER STRAIN SENSING FOR STRUCTURAL HEALTH AND LOAD MONITORING

Intra-core Bragg reflection gratings fabricated in communications-grad e optical fibre are increasingly considered as strain-sensing elements in mechanical structures, and considerable experience of single-eleme nt grating design and fabrication has now been accumulated. The effici ent application of the technology to strain monitoring in extended mec hanical structures, however necessitates the development of techniques for implementation of multi-element arrays, possibly incorporating ma ny tens of discrete sensing sites and, in addition to imposing additio nal constraints on grating fabrication technology, necessitates the de velopment of suitable instrumentation schemes for data acquisition and processing. GEC-Marconi Materials Technology Limited, Caswell, UK, ha s been investigating the design, fabrication and structural health mon itoring applications of Bragg fibre gratings for several years. This p aper describes the present status of Bragg grating fabrication technol ogy, including recent studies in both the fabrication and interrogatio n of extended arrays and reports recent experiments in the application of these intrinsically simple and robust components to health monitor ing in representative engineering structures.