Abstract: An image fiber preform for use in an image fiber according to the present invention includes a plurality of optical fiber strands, each optical fiber strand including a silica glass core which contains a dopant for increasing a refractive index of the core and a silica glass cladding surrounding the silica glass core, the silica glass cladding containing a fluorine dopant for decreasing a refractive index of the cladding, the cladding having an outer peripheral surface, and a quartz tube in which the optical fibers are closely arranged, wherein the cladding has a concentration of the fluorine dopant which decreases radially outward toward the outer peripheral surface of the cladding. in the present invention, an image fiber prepared from the image fiber preform and fabrication processes for the image fiber preform and the image fiber are provided.

Abstract: Near uniform optical amplification is achieved in a lightwave transmission system in which a plurality of short lengths of rare earth doped silica-based fibers and a corresponding plurality of long lengths of substantially undoped silica-based fibers are interleaved to form a fiber span having alternating sections of compensated (moderate gain) and uncompensated lightwave transmission media. Pumping of the amplifying fiber sections is performed remotely from either end of the fiber span. Bidirectional pumping, that is, pumping from each end of the fiber span, enhances the uniformity of the optical amplification for signals over the entire span. Amplifying fiber section lengths are variable in substantially inverse proportion to dopant concentration within the particular section.

Abstract: Disclosed is apparatus comprising an optically pumped optical gain device that comprises a rare earth (RE)-doped planar waveguide with non-uniform dopant distribution in the core of the waveguide. The RE ions are advantageously distributed such that the ions are concentrated in a core region in which the mode intensity of both signal radiation and pump radiation is relatively high. In preferred embodiments of a single mode planar waveguide according to the invention the RE ions are substantially concentrated in the central core region. A method of making the disclosed apparatus is also disclosed. The method involves implantation of RE ions into the core region.