Patent ID: 6131415
Filing Date: 2000-10-17
Classification: C03B,C03C,G02B,Y02P

Abstract:
A method for making a singlemode optical fiber having low loss at 1385 nanometers (nm) including the following steps:forming a glass rod by soot deposition, said rod comprising a cylindrical core having a diameter (d) surrounded by a layer of deposited cladding material having a diameter (D), wherein D/d<7.5;dehydrating the glass rod in a chlorine- or fluorine-containing atmosphere at a temperature, which is less than 1300.degree. C. in order to reduce the concentration of hydroxyl ions to a level that is less than about 0.8 parts per billion by weight;consolidating the glass rod at a temperature, which is greater than 1400.degree. C.;providing a hollow cylindrical tube having an inside diameter that is slightly larger than the outside diameter of the glass rod, said tube being made from glass having a concentration of hydroxyl ions that is less than 200 parts per million by weight;placing a substantial portion of the glass rod into the hollow tube; andexposing the tube to a heat source that moves longitudinally relative to said tube and rod, wherein the heat from the source causes the tube to collapse inwardly upon said rod forming a glass preform; anddrawing a glass fiber from the glass preform, said fiber having a transmission loss that is less than 0.33 dB per kilometer at 1385 nm.