Optical fiber having an expanded mode field diameter and method of expanding the mode field diameter of an optical fiber

摘要

The present invention is directed to a generally small mode field diameter (MFD) optical fiber having a core bounded by a cladding, a cleaved end, and an expanded mode field diameter. The expanded mode field diameter is formed by thermally diffusing one or more dopants in the core of the small mode field diameter optical fiber using a highly localized heat source. The resulting adiabatic taper has an expanded mode field diameter that is optimized for connection to another optical fiber having a larger mode field diameter. The adiabatic taper is formed in the smaller MFD optical fiber by aligning and abutting the cleaved ends of two fibers having different mode field diameter to form a splice seam. The splice seam is offset a predetermined distance from the center of the region heated by a heat source to splice the fibers and expand the mode field diameters. As the mode field diameters expand, the splice loss across the splice is monitored. When the splice loss is at or sufficiently close to a target loss, heating is terminated, and the spliced optical fiber is cleaved where the mode field diameter of the smaller MFD fiber portion of the spliced optical fiber is optically expanded to match the mode field diameter of another optical fiber.