Patent ID: 6374641
Filing Date: 2002-04-23
Classification: C03B,C03C,G02B

Abstract:
A method for making a continuous-clad filament including a core and a cladding adjacent said core region, comprising the steps of:a) providing a core cullet feedstock having a particle diameter between about 100-5,000 &mgr;m and a known melting point; b) providing a rigid cladding structure having a softening point higher than the melting point of said core feedstock, wherein said cladding has a composition that is chemically compatible with said core; c) introducing said cullet into said cladding structure; d) heating an end of said core containing cladding structure in a furnace to near the softening point of said cladding; and e) drawing said core containing cladding into a continuous clad filament; wherein the core cullet is a glass having a composition consisting essentially, in mole %, of: SiO20-90GeO20-90Na2O0-25Li2O0-10K2O0-25Rb2O0-25Cs2O0-25Al2O35-40Ga2O35-40RE2(1)O30-40RE2(2)O30-1â€‚Er2O30.001-5â€ƒâ€ƒâ€‰Yb2O30-5â€‚PbO0-15RO0-20ZnO0-10ZrO20-2â€‚TiO20-2â€‚Nb2O50-10Ta2O50-10P2O50-5â€‚B2O30-15As2O30-10Sb2O30-20Na2Cl20-10Bi2O3â€ƒâ€‚â€‰0-5, andup to 15 weight % fluorine in the form of at least one of a fluorinated component of the glass composition and a batch constituent selected from a group consisting of at least one of AlF3, REF3, NH5F2, NaF, Na2SiF6, Na3AlF6, whereRE(1) is at least one of Y, La, Gd, and Lu; RE(2) is at least one of Ce, Pr, Nd, Sm, Eu, Th, Dy, Ho, and Tm; R is at least one of Ba, Ca, Mg, and Sr; (SiO2+GeO2) is in the range (40-90); and (Al2O3+Ga2O3)>(RO+â€œalkâ€ 2O+RE2O3) where â€œalkâ€  is at least one of Li, Na, K, Cs, and Rb.