Development of fiber optic extensometers

A new displacement monitoring system based on low coherence interferometry using standard telecommunication fibers is presented. The measuring system is especially developed for the needs and conditions encountered in the field of civil engineering. The system features a precision of 10 mu m to 100 mu m (depending on the sensor type) over a measuring length up to 100 m, an operational range of 70 mm, stability over long periods (at least two years) and insensitivity to ageing of the fiber and connector losses. The results of laboratory and field tests show that fiber optic extensometers are promising tools for the long term monitoring and survey of civil engineering structures.