Research on an optical fiber low-coherence interferometric sensing system with dual-interferometry

A novel optical fiber low-coherence interferometric sensing system, which is suitable for absolute remote measurement and is endowed with a dual-interferometer as receiving interferometer, is presented. The system includes a sensing interferometer and a receiving interferometer. The sensing interferometer is used for being embedded in the remote measured field for sensing the measurand. And the receiving interferometer, which is connected to the sensing interferometer with fiber link, multiplexes a low-coherence interferometer with a high-coherence interferometer by employing fiber Bragg gratings as in-fiber reflective mirrors. The amplitude of the measurand is determined by the low-coherence interferometry while the value of the measurand is measured by the high-coherence interferometry. A feedback loop is designed to stabilize the receiving interferometer by reducing the influences resulting from environmental disturbances. The measurement range is 6 mm and the measurement resolution is less than 1 nm.