Reconstructing arbitrary strain distributions within fiber gratings by time–frequency signal analysis

We apply time-frequency signal-analysis techniques to recover arbitrary distributions of axial strain along a fiber grating from its reflection spectral response. The proposed method permits accurate strain reconstruction with no restrictions on the applied strain profile or on the grating length. We demonstrate the validity and accuracy of the technique by reconstructing the strain field in a fiber grating with a nonmonotonic strain profile, which includes all the following: a constant strain section, high gradient variations, and strain discontinuities.