Absolute strain measurement using an in-fibre-Bragg-grating-based Fabry-Perot sensor

A novel method for achieving both large dynamic range and high resolution for static strain measurement is proposed and demonstrated. This method is based on the combination of two in-fibre Bragg gratings (FBG) and an all-fibre Fabry-Perot interferometric sensor (FFPI) formed by the two FBGs. The FFPI is used to carry out high-resolution strain measurement via phase detection of the interferometric signal while the wavelength shift of the two FBGs forming the FFPI is used for determining the fringe number of the interferometric signal.