Automatic core-alignment for fusion splicing double-clad fibers

Abstract

In aligning ends of optical fibers, e.g. ends of large mode area double-clad fibers (LMA-DCFs), in a fiber optic fusion splicer the best position of the object plane of the optical system for observing images of the cores of the fiber ends are first determined by maximizing the contrast of the core image, in particular the core image peak in intensity profiles. The alignment process may be performed by adjusting the offset distance between the observed cores in some suitable way, e.g. by using a cascade technique. In e.g. a process for prealigning the fiber ends the self-focusing effect of optical fibers can be used to first determine the best object plane position for observing the self-focusing effect and then the very pre-alignment operation can be performed. This may extend the range of image analysis allowing e.g. that alignment, in particular core alignment, can be performed without requiring direct information showing the position of sides or edges of the claddings in captured pictures.