Preparation of halogen-doped silica is described. The preparation includes doping silica with high halogen concentration and sintering halogen-doped silica to a closed-pore state in a gas-phase environment that has a low partial pressure of impermeable gases. Impermeable gases are difficult to remove from halogen-doped fiber preforms and lead to defects in optical fibers drawn from the preforms. A low partial pressure of impermeable gases in the sintering environment leads to a low concentration of impermeable gases and a low density of gas-phase voids in densified halogen-doped silica. Preforms with fewer defects result.

A color-stable, antimicrobial glass powder obtained by partial ion exchange at a temperature of 300° C. to 350° C. and an exchange time of 1 to 120 minutes, is formed of a mixture of porous glass particles having micropores and macropores made of borosilicate glass continuously foamed by extrusion having a Fe.sub.2O.sub.3 content <0.2 wt %, in which the obtained glass foam is subsequently comminuted by dry grinding to average particle sizes of 1.0 to 8.0 μm. The mixture includes color stabilizers containing 0.1% to 0.2% of ammonium ions and antimicrobial metal ions from dissolved metal salts, wherein the metal ions may be silver and/or zinc and/or copper ions. A method for the production of a color-stable, antimicrobial glass powder and applications for using the color-stable, antimicrobial glass powder are also provided.

A co-doped optical fiber is provided having an attenuation of less than about 0.17 dB/km at a wavelength of 1550 nm. The fiber includes a core in the fiber having a graded refractive index profile with an alpha of greater than 5. The fiber also includes a cladding in the fiber that surrounds the core addition, the core includes silica that is co-doped with two or more halogens.

Preparation of halogen-doped silica is described. The preparation includes doping silica with high halogen concentration and sintering halogen-doped silica to a closed-pore state in a gas-phase environment that has a low partial pressure of impermeable gases. Impermeable gases are difficult to remove from halogen-doped fiber preforms and lead to defects in optical fibers drawn from the preforms. A low partial pressure of impermeable gases in the sintering environment leads to a low concentration of impermeable gases and a low density of gas-phase voids in densified halogen-doped silica. Preforms with fewer defects result.

A color-stable, antimicrobial glass powder obtained by partial ion exchange at a temperature of 300 C. to 350 C. and an exchange time of 1 to 120 minutes, is formed of a mixture of porous glass particles having micropores and macropores made of borosilicate glass continuously foamed by extrusion having a Fe.sub.2O.sub.3 content <0.2 wt %, in which the obtained glass foam is subsequently comminuted by dry grinding to average particle sizes of 1.0 to 8.0 m. The mixture includes color stabilizers containing 0.1% to 0.2% of ammonium ions and antimicrobial metal ions from dissolved metal salts, wherein the metal ions may be silver and/or zinc and/or copper ions. A method for the production of a color-stable, antimicrobial glass powder and applications for using the color-stable, antimicrobial glass powder are also provided.

A co-doped optical fiber is provided having an attenuation of less than about 0.17 dB/km at a wavelength of 1550 nm. The fiber includes a core in the fiber having a graded refractive index profile with an alpha of greater than 5. The fiber also includes a cladding in the fiber that surrounds the core addition, the core includes silica that is co-doped with two or more halogens.

According to embodiments, an optical fiber may include a core portion comprising an outer radius r.sub.C and a maximum relative refractive index .sub.Cmax. A cladding may surround the core portion and include a low-index trench and an outer cladding. The low index trench may surround the core portion and includes an outer radius r.sub.T and relative refractive index .sub.T. The outer cladding may surround and be in direct contact with the low-index trench. The outer cladding may be formed from silica-based glass comprising greater than 1.0 wt. % bromine and has a relative refractive index .sub.OC, wherein .sub.Cmax>.sub.OC>.sub.T. The optical fiber may have a cable cutoff of less than or equal to 1530 nm. An attenuation of the optical fiber may be less than or equal to 0.185 dB/km at a wavelength of 1550 nm.

According to embodiments, an optical fiber may include a core portion comprising an outer radius r.sub.C and a maximum relative refractive index .sub.Cmax. A cladding may surround the core portion and include a low-index trench and an outer cladding. The low index trench may surround the core portion and includes an outer radius r.sub.T and relative refractive index .sub.T. The outer cladding may surround and be in direct contact with the low-index trench. The outer cladding may be formed from silica-based glass comprising greater than 1.0 wt. % bromine and has a relative refractive index .sub.OC, wherein .sub.cmas>.sub.OC>.sub.T. The optical fiber may have a cable cutoff of less than or equal to 1530 nm. An attenuation of the optical fiber may be less than or equal to 0.185 dB/km at a wavelength of 1550 nm.