Fibre Optic Bragg Grating Sensors

The Swinburne FigFab (fiber Bragg grating fabrication) facility uses a standard phase mask exposure technique. This approach is recognised as one of the most effective methods for inscribing Bragg gratings in photosensitive fibre and has seen extensive commercial use. The method uses a phase mask to generate the spatial modulation of the UV writing beam inside the fibre core which results in a periodic change of the refractive index of the fibre core material.

At the moment we are developing an additional laboratory system which allows us to write Bragg gratings with means of holographic interferometry. Instead of the pitch of the phase mask in this method the inscribed Bragg grating wavelength is dependent on the angle between the fibre and the two superimposed UV laser beams (see figure). For this method a high temporal coherence of the laser is crucial.