This paper demonstrates that the combination of the optical low-coherence reflectometry and the layer-peeling algorithm is a suitable method to measure the index profile of fiber Bragg gratings. The high sensitivity of this technique permits to detect index modulation amplitude as small as ¦ § ¦ © . The phase of the grating can also be determined accurately and we demonstrate that this measurement permits to retrieve the axial strain distribution for gratings subjected to strain gradient.