Fibre Bragg gratings fabricated using a wavelength tuneable laser source and a phase mask based interferometer

Arrays of in-fibre Bragg gratings (IFBGs) are increasingly being employed to measure strain in a variety of structures. To maximize the number of IFBGs that can be multiplexed from a broad band source requires accurate control and reproducibility of the Bragg centre wavelength. In this communication we demonstrate that the combination of a phase mask based interferometer and tuneable UV writing wavelength can provide high resolution control over the Bragg centre wavelength. The interferometer is shown to have two regimes of operation, offering a high resolution (0.03 nm) or a large spectral range (51 nm). The technique is compared to previous writing methods and is demonstrated experimentally.