ABSTRACT
This work presents a new sequential UV-writing procedure for fabricating long fiber Bragg grating (FBG) devices. To real-time accurately align the position of every exposed FBG section prior to UV exposure, a single-period reference fiber grating with strong refractive index modulation is probed by applying an interferometric side-diffraction method to measure the grating phase as the position reference. In this way the overlapped FBG sections can be connected section-by-section without obvious phase errors, even when the written index-modulation is weak.
ABSTRACT
We propose a flexible method for fabricating complex fiber grating structures based on sequential writing for fiber gratings with polarization control of the UV source beam. Pure apodized as well as arbitrary phase-shifted fiber Bragg gratings (FBGs) can be fabricated in a single scan. Experimental examples of raised-cos2 apodized and dispersionless FBG filters are given to demonstrate the feasibility of this method.