Abstract: An optically active device comprising an optical fiber, a light source and an optical device is disclosed. The optical fiber comprises a core made of an optical functioning glass doped with Pr.sup.3+ as an active ion and transmits light at a first wavelength. The light source generates excitation light at a second wavelength shorter than the first wavelength. The optical device directs the excitation light from the light source into the optical fiber. Then, Pr.sup.3+ in the core of the optical fiber is stimulated to emit light at the second wavelength. As a result, an optical function such as optical amplification can be effected at the second wavelength.

Abstract: There is provided a method of producing a protective metal coated or covered superconducting ceramic wire by applying a finely pulverized protective metal-dispersed polymeric resin onto the surface of a glass wire in amorphous state of metal oxides capable of being converted into superconductive ceramic, heating the wire to remove the polymeric resin therefrom to obtain the wire having a metal powder coating thereon, and heat-treating the wire to become superconductive. The coating is easily conducted without damaging the excellent productivity of the so-called melt-quenching and preform wire-drawing process for producing a superconducting ceramic wire.

Abstract: A superconducting ceramic wire is produced by melting a superconducting ceramic-forming metal oxide composition, and quenching the melt into a glass which is then formed into a preform of thin plate. The preform is soften and wire-drawn without causing crystallization in a furnace into a flexible elongated thin tape having a thickness of e.g. 40 to 60 .mu.m. The tape is heat-treated for crystallization to obtain the superconducting wire. The disclosure mentions mainly Bi Bi-Sr-Ca-Cu-O superconducting systems.

Abstract: A superconducting ceramic wire is prepared from a superconducting ceramic-forming oxide composition by melting, the composition and quenching the melt to form a dense glass, which is soften and wire-drawn in a furnace. The resulting wire is heat-treated to form crystals and made into a superconducting ceramic wire. The wire has a flexibility and remarkable superconductivity which can further be improved by applying pressure to be made more dense and repeating the heat-treatment.