PHASE MASK DESIGN AND PHASE MASK FOR WRITING OPTICAL FIBRE BRAGG GRATINGS

摘要

The present invention is directed to a system and method for designingefficient multi-channel FBG gratings using a pre-compensated phase mask fordiffracting light for side-writing the grating on an optical fiber core. Adesired phase function of the FBG is generated, specifically tailored to aneffective spacing between the phase mask and the optical fiber core. From thephase function a phase mask is pre-compensated to offset diffraction effectsassociated with each longitudinal position of the FBG receiving light from twocorresponding longitudinal positions of the phase mask substantiallysymmetrically spaced longitudinally relative to each particular longitudinalposition of the FBG. The two corresponding longitudinal positions of the phasemask are spaced longitudinally from each other by a spacing determined by theeffective spacing between the phase mask and fiber core and by the first orderdiffraction angle of light through the phase mask. The design involves Fouriertransformation and optimisation process steps for binory phase gratings.