Technique for correcting systematic phase errors during fibre Bragg grating inscription

Abstract

A simple technique for correcting systematic phase errors introduced during the holographic inscription of fibre Bragg gratings is presented. The technique involves characterising the fabrication errors associated with the phase mask and writing medium (i.e. the fibre). This is accomplished by measuring the phase of the coupling coefficient of a weak, uniform ‘trace grating’ written in the fibre. This phase is then used to generate a phase-corrected profile by combining the inverse of the measured phase with the phase of a target grating's profile. The trace grating is then overwritten with the stronger phase-corrected grating. Using this technique, a dual phase-shifted grating has been fabricated successfully and the overall phase error in reduced by a factor of 13.