Abstract: The invention provides a low cost method of manufacturing high capacity preforms by chemical vapor deposition. More particularly, there is described a method of manufacturing an optical fiber preform, which method comprises the steps of providing a substrate tube of silica doped with sufficient chlorine to obtain an OH concentration of less than 100 ppb and doped with sufficient fluorine proportional to the chlorine doping to obtain a refractive index that is lower than that of a natural silica, depositing inner cladding and an optical core inside the substrate tube, collapsing the substrate tube to form a primary preform, and depositing outer cladding of said natural silica on the resulting primary preform. The invention is applicable to manufacturing optical fibers.

Abstract: A method of cooling an optical fiber while it is being drawn through contact with at least one cooling fluid in at least one cooling area, wherein said method is such that fast cooling, i.e. cooling that is faster than cooling in the surrounding air, is followed by slow cooling, i.e. cooling slower than cooling in the surrounding air, the temperature of the fiber in an intermediate area between the two cooling areas lying in the range 1200° C. to 1700° C. in the case of silica glass fibers.

Abstract: The invention provides a low cost method of manufacturing high capacity preforms by chemical vapor deposition. More particularly, there is described a method of manufacturing an optical fiber preform, which method comprises the steps of providing a substrate tube of silica doped with sufficient chlorine to obtain an OH concentration of less than 100 ppb and doped with sufficient fluorine proportional to the chlorine doping to obtain a refractive index that is lower than that of a natural silica, depositing inner cladding and an optical core inside the substrate tube, collapsing the substrate tube to form a primary preform, and depositing outer cladding of said natural silica on the resulting primary preform. The invention is applicable to manufacturing optical fibers.

Abstract: A method of cooling an optical fiber while it is being drawn through contact with at least one cooling fluid in at least one cooling area, wherein said method is such that fast cooling, i.e. cooling that is faster than cooling in the surrounding air, is followed by slow cooling, i.e. cooling slower than cooling in the surrounding air, the temperature of the fiber in an intermediate area between the two cooling areas lying in the range 1200° C. to 1700° C. in the case of silica glass fibers.