Patent ID: 7484387

Claim:
A method of making an optical fiber having a plurality of voids extending along the fiber axis, comprising the steps of: preparing a preform having a plurality of voids whose cross-sectional areas are uniform along the preform axis, the preform having an initial area fraction of the plurality of voids that is a ratio of a total area of the plurality of voids to cross-sectional area; drawing the optical fiber from the preform with a fiber drawing furnace, the drawing step includes determining a resulting area fraction of the plurality of voids in the drawn optical fiber, the drawing step comprising the sub steps of: measuring the speed at which the preform is supplied, the speed at which the optical fiber is drawn, and the diameter of the optical fiber during the drawing, and calculating the resulting area fraction of the plurality of voids in said drawn optical fiber from the values measured in the measuring step, a preform diameter, and the initial area fraction of the plurality of voids in the preform, wherein the preform diameter and the initial area fraction of the plurality of the voids in the preform are measured before the optical fiber drawing; and performing feedback control of pressure in the plurality of voids, a furnace temperature and a time duration of the fiber in the furnace during the drawing, based on the resulting area fraction.