Method of and device for optical fibre grating fabrication

Abstract From the Canadian patent

An optical fibre is sequentially submitted to a first and a second exposure to the grating writing radiation. The first exposure is performed by positioning the fibre in proximity of a phase mask so as to expose the, same fibre to a radiation of which the intensity is spatially modulated by the interference fringes generated by the phase mask itself. The second exposure is performed with the fibre spaced apart from the phase mask in the propagation direction of the writing radiation by a sufficient distance in order the radiation incident on the fibre is substantially defined by the first diffraction orders generated by the phase mask in a situation in which there is basically no reciprocal …