Patent ID: 10427969

Abstract:
An optical fiber manufacturing method includes: melting and drawing an optical fiber preform to form a glass fiber; cooling the glass fiber while inserting the glass fiber into a tubular slow-cooling device from an inlet end toward an outlet end thereof; and lowering an inner wall temperature of the slow-cooling device below a temperature of the glass fiber and providing a pressure gradient in which a pressure increases in a direction from the inlet end toward the outlet end inside the slow-cooling device when cooling the glass fiber, wherein the average pressure change dP/dL in a moving direction of the glass fiber inside the slow-cooling device satisfies the following Formula (1) when the tube inner diameter of the slow-cooling device is defined as D [m] and the length of an internal space of the slow-cooling device in the moving direction of the glass fiber is defined as L [m]. (πD2/4)×dP/dL≤0.03  (1)