Distributed sensing with OFDR and its application to structural health monitoring

Optical fiber sensors are promised candidates as sensor elements in structural health monitoring (SHM). Especially fiber-optic distributed strain sensors that return a strain value as a function of linear position along an optical fiber have been attractive for people in the field of SHM. We have developed a distributed strain sensing system using long-length fiber Bragg gratings (FBGs), based on optical frequency domain reflectometry (OFDR). We employ long-length FBGs whose length is about 100 mm and the sensing region, in other words the gauge length, can be expanded up to more than 1 m by serially-cascaded long-length FBGs. This sensing system has the high spatial resolution of less than 1 mm. In this paper the distributed sensing system with OFDR and its application to SHM are described.