Abstract: The stepped optical fiber has a core glass member and a surrounding cladding glass member. It has a high numerical aperture (NA)?0.50. The core glass member preferably has a zinc-containing composition including, in % by weight, SiO2, 42 to 53; ZnO, 16 to 38; PbO, 1 to 20; Na2O, <14; K2O, <12; with a sum of ZnO and PbO?30 and a sum of Na2O and K2O is ?2. The cladding glass composition, which is compatible with this core glass, includes, in percent by weight, SiO2, 60 to 72; B2O3, <20; Al2O3, <10; Na2O, <18; and K2O, <15. The resulting optical fiber has low attenuation, very neutral color transmission and low manufacturing costs. Other cladding glass compositions resulted in considerably poorer properties with too much crystallization at the core glass boundary layer. Environmentally-friendly, lead-free embodiments of the core glass were also prepared having even lower aperture values of ?0.48.

Abstract: The stepped optical fiber has a core glass member and a surrounding cladding glass member. It has a high numerical aperture (NA)?0.50. The core glass member preferably has a zinc-containing composition including, in % by weight, SiO2, 42 to 53; ZnO, 16 to 38; PbO, 1 to 20; Na2O, <14; K2O, <12; with a sum of ZnO and PbO?30 and a sum of Na2O and K2O is ?2. The cladding glass composition, which is compatible with this core glass, includes, in percent by weight, SiO2, 60 to 72; B2O3, <20; Al2O3, <10; Na2O, <18; and K2O, <15. The resulting optical fiber has low attenuation, very neutral color transmission and low manufacturing costs. Other cladding glass compositions resulted in considerably poorer properties with too much crystallization at the core glass boundary layer. Environmentally-friendly, lead-free embodiments of the core glass were also prepared having even lower aperture values of ?0.48.

Abstract: A transparent or translucent inorganic material, especially a glass-ceramic and/or composite material, is provided with a low average thermal longitudinal expansion coefficient, .alpha., of from -1.times.10.sup.-6 K.sup.-1 to +2.times.10.sup.-6 K.sup.-1 in the temperature range of -50.degree.-700.degree. C., with the following composition (in weight percent):Li.sub.2 O, 2.5-6.0; Na.sub.2 O, 0-4.0; K.sub.2 O, 0-4.0; Na.sub.2 O+K.sub.2 O, 0.2-4.0; MgO, 0-3.0; ZnO, 0-3.0; BaO, 0-3.5; CaO, 0-1.0; SrO, 0-1.0; Al.sub.2 O.sub.3, 18-28; SiO.sub.2, 50-70; TiO.sub.2, 1.0-7.0; ZrO.sub.2, 0-3.5; TiO.sub.2 +ZrO.sub.2, 1.0-7.0; and P.sub.2 O.sub.5, 0-8.0,optionally with coloring components (in weight percent):V.sub.2 O.sub.5, 0-2.0; Cr.sub.2 O.sub.3, 0-2.0; MnO, 0-2.0; Fe.sub.2 O.sub.3, 0-2.0; CoO, 0-2.0; and NiO, 0-2.0,optionally, conventional refining agents, such as As.sub.2 O.sub.3, Sb.sub.2 O.sub.3, NaCl, and Ce.sub.2 O.sub.

Abstract: Glass composition ranges are described which permit the introduction of laser activators into fluorphosphate glass with exceptionally high fluorine content while forming glasses of high crystallization stability and permitting the realization of large melt volumes. The high fluorine content imparts to the glasses an exceptionally low nonlinear refractive index n.sub.2 down to O,4 .times.10.sup.-13 esu.

Abstract: A glass when in the form of an optical fiber having an optical loss of not more than 150 dB/km, high transparency, a high numerical aperture, and a high flexural strength, said glass being especially suitable for optical fibers and consisting essentially of:SiO.sub.2 : 65 - 75 mol-%; (38 - 46% by weight);R.sub.2 o: 4 - 17 mol-%; (4 - 13% by weight);PbO: 16 - 25 mol-%; (42 - 55% by weight); wherein R.sub.2 O is Na.sub.2 O, K.sub.2 O or Cs.sub.2 O or mixtures thereof, preferably not more than 3.0 mol % Na.sub.2 O, and with the provision that the molar ratio of SiO.sub.2 : PbO is 2.5 - 4.0.

Abstract: Arsenic pentoxide glasses characterized by containing 8 - 60 wt.% arsenic pentoxide and correspondingly 92 - 40 wt.% polyvalent metal fluorides exhibit improved processing characteristics while maintaining outstanding optical properties when prepared from a formula containing at least 0.5% of at least one member selected from the group consisting of bromides, chlorides, sulfates and metal oxides.