Low-coherence strain monitoring system using an optimised triple-wavelength combination source and chirped Bragg grating-based Fabry-Perot sensor

Full text: This paper reports on the development of an optical fibre strain monitoring system based on low-coherence interferometry. We employ a novel type of Fabry-Perot sensing element, fabricated by writing sets of superimposed chirped Bragg gratings. The tandem configuration uses a Fabry-Perot as the sensor interferometer and an all-fibre Michelson as receiver interferometer. High-accuracy absolute measurements of slowly varying strains are possible due to the triple-wave-length combination source and rapid scanning with a PZT phase modulator. Maximum strains of up to 15,000 microstrain, limited by the strength of the fibre in the grating regions, are possible with this sensor