Method of making a glass body having a graded refractive index profile

Claim 2

Method of producing an optical fiber, the method comprising (a) providing a porous body that comprises a dopant-containing region having a central portion and a peripheral portion, this dopant distribution in the porous body to be referred to as the initial dopant distribution; (b) heating the porous body such that the porous body is consolidated into a glass body, to be referred to as the intermediate glass body, the intermediate glass body having a refractive index profile; (c) making a preform by a process that comprises adding glass material to the intermediate glass body; and (d) drawing an optical fiber from the preform; wherein (e) the porous body has, during at least part of step (b), a radially non-uniform porosity and consequently a radially non-uniform density, with the density in the central portion of the dopant-containing region being higher than in the peripheral portion thereof; and wherein (f) step (b) further comprises heating the porous body to a temperature and for a time such that substantial densification of the porous body occurs, the porous body being contacted during at least part of this time with a halogen-containing atmosphere such that a part of the dopant is removed from the porous body such that a dopant distribution results that differs substantially from the initial dopant distribution, such that the refractive index profile in the intermediate glass body is a substantially Gaussian profile.

Claim 3

Method of claim 1, wherein the provided porous body has a radially non-uniform density.

Claim 4

Method of claim 1, wherein the dopant comprises germania, and wherein the provided porous body is a porous high-silica body having a radially non-uniform density.

Claim 5

Method of claim 3, wherein the heating of the porous body comprises maintaining the porous body at a densification temperature in the range from about 1250° C. to less than about 1350° C., and wherein the atmosphere comprises chlorine and oxygen such that, at least during a substantial portion of the time the porous body is maintained at the densification temperature, the ratio (vol. % chlorine) 2 /(vol. % oxygen) is greater than about 5 vol. %.

Claim 6

Method of claim 1, wherein step (c) comprises adhering porous material to the intermediate glass body, and consolidating the porous material such that the preform results.

Claim 7

Method of claim 1, wherein, prior to step (b), the radial distribution of the dopant in the porous body is substantially constant.

Claim 8

Method of claim 1, wherein the optical fiber is dispersion shifted single mode fiber having a loss at 1.55 μm of less than 1 db/km.

Claim 9

Method of producing an optical fiber having a substantially Gaussian index profile, the method comprising (a) providing a porous high silica body that comprises a GeO 2 -containing region having a central portion and a peripheral portion, this GeO 2 distribution in the porous body to be referred to as the initial GeO 2 distribution; (b) heating the porous body such that the porous body is consolidated into a glass body, to be referred to as the intermediate glass body, the intermediate glass body having a refractive index profile; (c) making a preform from the intermediate glass body by a process that comprises adhering porous glass material to the intermediate glass body, and consolidating the porous material such that the preform results; and (d) drawing an optical fiber from the preform; wherein (e) the provided porous body has a radially non-uniform porosity and consequently a radially non-uniform density, with the density in the central portion of the GeO 2 -containing region being higher than in the peripheral portion thereof and wherein, (f) step (b) comprises heating the porous body to a temperature and for a time such that substantial densification of the porous body occurs, the porous body being contacted during at least part of this time with a chlorine-containing atmosphere such that a part of the GeO 2 is removed from the porous body, such that the resulting GeO 2 distribution differs substantially from the initial GeO 2 distribution and being such that the intermediate glass body has a substantially Gaussian index profile.

Claim 10

Method of producing an optical fiber having a substantially Gaussian index profile, the method comprising (a) providing a porous high silica body that comprises a GeO 2 -containing region having a central portion and a peripheral portion, this GeO 2 distribution in the porous body to be referred to as the initial GeO 2 distribution; (b) heating the porous body such that the porous body is consolidated into a glass body, to be referred to as the intermediate glass body, the intermediate glass body having a refractive index profile; (c) making a preform from the intermediate glass body by a process that comprises adhering porous glass material to the intermediate glass body, and consolidating the porous material such that the preform results; and (d) drawing an optical fiber from the preform; wherein (e) the provided porous body has a radially non-uniform porosity and consequently a radially non-uniform density, with the density in the central portion of the GeO 2 -containing region being higher than in the peripheral portion thereof and wherein, (f) step (b) comprises heating the porous body to a temperature and for a time such that substantial densification of the porous body occurs, the porous body being contacted during at least part of this time with a chlorine-containing atmosphere such that a part of the GeO 2 is removed from the porous body, such that the resulting GeO 2 distribution differs substantially from the initial GeO 2 distribution and being such that the intermediate glass body has a substantially Gaussian index profile.