Direct determination of main fibre Bragg grating parameters using OLCR

Optical low coherence reflectometry (OLCR) is applied to the characterisation of homogeneous Bragg gratings written in single-mode optical fibres with a UV laser. This technique allows for the measurement of the spatial distribution of the field reflection coefficient within the fibre with a spatial resolution of 9 µm in the fibre material. A grating with a high spatial definition has been measured and its length precisely determined. The amplitude of the index modulation was then obtained by the absolute signal level just after the entrance of the grating on the calibrated OLCR spectrum. Thus, this method gives a direct information of the main fibre Bragg grating parameters, the length and the index modulation.