Abstract: A resin fiber formation nozzle 20 of the present invention is a nozzle configured to discharge a molten resin material into a fiber shape. The nozzle 20 includes: the internal flow path 21; an inlet 22 that allows the resin material to flow into the internal flow path 21; and an outlet 23 that allows the resin material to be discharged from the internal flow path 21 to an outside of the nozzle 20. The internal flow path 21 is shaped such that a diameter of the internal flow path 21 decreases continuously, in a section from a position A 5 mm upstream in the internal flow path 21 from the outlet 23 to a position B of the outlet 23, from the position A toward the position B.

Abstract: The present invention provides a fiber manufacturing method suitable for reducing the variation in outer diameter. The fiber manufacturing method of an embodiment of the present invention includes: discharging a softened linear body 1 through a nozzle 10; and winding the linear body 1 so that the linear body 1 passes through a cooling portion 20 supplied with a cooling fluid 50, thereby obtaining a fiber 5. The cooling portion 20 has a filter 40 configured to rectify the cooling fluid 50. The cooling fluid 50 in the cooling portion 20 has a temperature that is substantially constant in a moving direction of the linear body 1. According to the fiber manufacturing method of the embodiment, an index M determined by the following equation (I) is 1.52 or less.

Abstract: The present invention provides an apparatus for manufacturing a plastic optical fiber suitable for adjusting a plastic optical fiber to be uniform in size while inhibiting the entry of a metal that causes an increase in transmission loss of the plastic optical fiber. The apparatus for manufacturing a plastic optical fiber of the present invention is provided with an extruding device and a gear pump. The extruding device has a containing portion that contains a resin composition, and introduces a gas into the containing portion to extrude the resin composition from the containing portion by means of the gas. The gear pump adjusts a flow rate of the resin composition extruded from the extruding device.