JPS60122755A - Coating method of optical fiber - Google Patents

Abstract

PURPOSE:To perform coating to an optical fiber while preventing sticking of foam thereto by passing a bare optical fiber after drawing through a vessel contg. a liquid resin then passing the fiber through a reduced pressure atmosphere connected to the outlet thereof thereby sticking thoroughly the liquid resin compsn. on the fiber. CONSTITUTION:A bar-shaped glass base material 1 for an optical fiber is heated and drawn in a heating furnace 2 and a bare optical fiber 3 after drawing is passed through a vessel 4 contg. a liquid resin then the fiber is passed through the reduced pressure atmosphere 6 in an enclosure 10 provided with a pressure reducing device connected to the outlet thereof. The liquid resin compsn. 5 in the vessel 4 is positively drawn out of the outlet and is coated thoroughly on the fiber 3 to suppress sticking of the foam. The liquid resin compsn. coated in the above-mentioned way is cured by a heating and curing device 8 by which the coated optical fiber 9 having a high mechanical characteristic and reliability is obtd.

Description

[Detailed description of the invention] [Background and purpose of the invention] The present invention relates to a method of coating an optical fiber.

Optical fiber is obtained by heating a rod-shaped glass base material in a heating furnace and drawing it, but it is fragile as it is, and furthermore, micro cracks on the surface tend to expand and grow in the air, so it is difficult to use a resin composition. It is put into practical use by coating the outer periphery of an optical fiber after it has been drawn.

The coating method currently widely used is to apply the resin composition to the optical fiber by placing the liquid resin composition in a container and inserting the drawn optical fiber into the container over medium heat. It is.

This method allows coating the optical fiber at the same time as drawing it.
Moreover, since no unreasonable stress is applied to the optical fiber, it is suitable for industrial use.
Although this is an excellent method, when attempting to increase the drawing speed, that is, the coating speed, a phenomenon occurs in which the resin composition does not sufficiently adhere to the surface of the optical fiber and air bubbles adhere to the surface of the optical fiber.

In this way, when air bubbles are attached to the surface of the optical fiber, optical 7 no. The mechanical properties of the fibers are quite poor, and the intended purpose of the coating cannot be achieved.

According to the studies of the present inventors, it is thought that the cause of this is that the liquid resin composition around the optical fiber cannot sufficiently follow the insertion and movement speed of the optical fiber, and the difference in movement speed becomes too large. .

In view of this situation, the present invention has been developed to suppress the formation of bubbles on the optical fiber surface as described above, to ensure sufficient adhesion of the resin composition, and to improve the mechanical properties and reliability of the optical fiber. An object of the present invention is to provide a method for coating an optical fiber.

[Summary of the Invention] The present invention involves heating and drawing a rod-shaped glass base material for optical fiber in a heating furnace, passing the drawn bare optical fiber through a container containing a liquid resin composition, and directly connecting it to the outlet of the liquid resin storage container. The method is characterized by exposing the bare optical fiber to a reduced pressure atmosphere, thereby sufficiently applying the liquid resin composition to the bare optical fiber, and then curing the liquid resin composition applied to the optical fiber using a heat curing device or the like.

[Embodiment] The structure of the present invention will be specifically explained with reference to the drawings without showing an embodiment.

In the figure, reference numeral 1 denotes a rod-shaped glass base material, which has a structure that includes all optically necessary cores, cladding, etc. as constituent elements of an optical fiber.

This rod-shaped glass preform 1 is heated and drawn in a heating furnace 2, and the drawn bare optical fiber 3 is passed through a container 4 containing a liquid resin composition 5.

The enclosure 1 covers the outlet part of the liquid resin composition storage container 4.
0, the atmosphere inside the enclosure 10 is reduced in pressure by the pressure reducing device 7, and the liquid resin composition 5 stored in the container 4 is actively drawn out from the outlet.

As a result, the liquid resin composition 5 is sufficiently applied to the bare optical fiber 3 that has passed through the liquid resin composition 5.

Thereafter, the liquid resin composition applied to the optical fiber is cured by the heat curing device 8.

9 is a resin-coated optical fiber.

In this way, by providing the reduced pressure atmosphere 6 directly connected to the outlet of the liquid resin composition storage container 4, the moving speed of the liquid resin composition 5 is increased, and the difference with the insertion speed of the optical fiber is significantly reduced. As a result, it was possible to suppress the formation of bubbles on the surface of the optical fiber.

[Effects of the Invention] With the optical fiber coating method of the present invention as explained above, since a reduced pressure atmosphere is provided directly to the outlet of the liquid resin composition storage container, the moving speed of the liquid resin composition can be reduced. This makes it possible to sufficiently adhere the liquid resin composition to the optical fiber and prevent the adhesion of air bubbles.

As a result, the mechanical properties and reliability of the optical fiber are significantly improved.

[Brief explanation of drawings]

The figure is an explanatory diagram showing one embodiment of the present invention. 1: Glass base material, 2: Heating furnace, 3: Bare optical fiber, 4:
container, 5: liquid resin composition, 5: reduced pressure atmosphere, 7: pressure reduction device, 8: heat curing device, 9: coated optical fiber, 10:
Surrounding body.

Claims (1)

[Claims] A glass preform 1 for optical fiber is heated and drawn in a heating furnace 2, and the bare optical fiber 3 after drawing is passed through a liquid resin storage container 4, and then passed through a reduced pressure atmosphere 6 connected to the outlet of the liquid resin storage container 4, whereby the bare optical fiber 3 is drawn. A method for coating an optical fiber, comprising applying a liquid resin composition 5 to an optical fiber 3, and then curing the liquid resin composition applied to the optical fiber.