JPS6332741B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coating the outer peripheral surface of an optical fiber used as an optical transmission line with a metal layer.

Optical fibers used as optical transmission lines are made by heating and softening the optical fiber base material and drawing it into a thin diameter.The outer peripheral surface of the optical fiber is then coated with a polymeric material as a protective layer, and the outer peripheral surface of the optical fiber is scratched. Reinforcement has been implemented to prevent this from occurring. However, the coating layer made of the above-mentioned polymeric material may deteriorate if it is exposed to tensile stress over a long period of time, which may cause the optical fiber's mechanical strength to deteriorate. Then there are some inconveniences. Therefore, instead of the coating layer made of the polymeric material, the outer peripheral surface of the optical fiber is made of aluminum (Al), which does not cause the above-mentioned disadvantages.
Alternatively, a metal-coated optical fiber coated with a metal such as tin (Sn) is well known. To obtain such a metal-coated optical fiber, conventionally, as shown in FIG. 1, an optical fiber base material 1 is heated and melted in a heating furnace 2, drawn into a small diameter optical fiber 3, and wound around a drum 6. At this time, in the extraction route of the optical fiber 3,
As shown in the figure, a crucible 4 made of, for example, brass with good workability, that is, a crucible 4 equipped with an outlet pipe 5 having a molten metal outlet 10 so as to protrude from the side, is arranged, and inside the crucible 4, for example, Filled with metal coating material 8 made of aluminum (Al) or the like,
The crucible 4 is heated by the heater 7 to melt the metal coating material 8, and the optical fiber 3 is inserted into the molten metal portion 9 that protrudes semispherically from the outlet 10 of the outlet tube 5 due to surface tension or the like. A method has been used in which a metal coating is applied. However, as mentioned above, when the metal coating crucible 4 is made of metal, there is a problem that the molten metal in the metal crucible 4 reacts with the metal crucible 4 and changes in quality, so that a high quality metal coating optical fiber cannot be obtained. There was an inconvenience that it was said that it was difficult to get rid of.

The present invention has been made in order to solve the above-mentioned conventional problems, and has an insertion hole in the center through which the optical fiber passes, in the drawing path of the optical fiber spun by a drawing means, and the outer circumference of the optical fiber is coated. A metal layer is formed on the outer circumferential surface of the optical fiber by arranging a material tube made of a metal material to form a layer, and sequentially melting the lower end of the material tube by heating means and pulling out the optical fiber from the insertion hole. A method of coating an optical fiber with metal is provided.

Embodiments of the metal coating method according to the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a sectional view showing an embodiment of the optical fiber metal coating apparatus according to the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

As shown in the figure, an optical fiber base material 1 is inserted into a heating furnace 2, heated and softened, and stretched, and an optical fiber drawing path is drawn into a small diameter optical fiber 3.
A small diameter insertion hole 22 through which the optical fiber 3 passes through the center
A holding arm 2 that can move up and down a material tube 21 made of a metal material that becomes the outer peripheral coating layer of the optical fiber.
4 so that the optical fiber 3 that has been drawn passes through the center insertion hole 22 of the material cylinder 21. The metal coating material tube 21 is made of a metal that has a melting point lower than the softening point of glass and has good adhesion to the optical fiber 3. For example, aluminum (Al), tin (Sn), etc. are molded into the above-mentioned cylindrical shape. Next, the lower end 23 of the material cylinder 21, through which the optical fiber 3 is inserted, is sent into the metal heating furnace 25, and the lower end 23 is constantly held at the melting part of the metal heating furnace to sequentially melt the material. If the metal is brought into enveloping contact with the outer periphery of the optical fiber 3 at that location, and the optical fiber 3 is pulled out downward and wound onto the winding drum 6, the metal will continue to form on the outer periphery of the drawn optical fiber 3. This makes it possible to apply metal coating almost uniformly.
The thickness of the metal coating can be controlled to a desired thickness by adjusting the thickness of the metal coating material cylinder 4 and the feeding speed into the furnace 7. In addition, in this coating method, from the lower part of the heating furnace 2 for spinning, the metal coating material cylinder 4 and its heating furnace 7 are
It is preferable to place the area including the molten metal under a clean nitrogen gas atmosphere, for example, to prevent slag and the like from forming in the molten metal.

As is clear from the above description, according to the metal coating method of the present invention, the lower end of the material cylinder made of the metal material that becomes the outer peripheral coating layer is Since the metal coating is applied to the outer circumferential surface of the optical fiber by directly heating and melting the metal, it has the advantage that the metal does not change in quality and a high quality metal coated optical fiber can be easily obtained.

[Brief explanation of the drawing]

FIG. 1 is an apparatus diagram for explaining a conventional optical fiber metal coating method, and FIG. 2 is a schematic sectional view of an apparatus used in an embodiment of the optical fiber metal coating method according to the present invention. In the figure, 3 is an optical fiber, 21 is a metal coating material tube, 22 is an optical fiber insertion hole of the metal coating material tube 21, 23 is a lower end of the metal coating material tube, 24 is a holding arm, and 25 is a heating furnace. .

Claims (1)

[Claims] 1. A material cylinder made of a metal material, which has an insertion hole in the center through which the optical fiber passes, and which itself serves as the outer peripheral coating layer of the optical fiber, is vertically disposed on the drawing path of the optical fiber spun by the drawing means. , characterized in that the lower end of the material cylinder is constantly held in a melting region of a metal heating furnace to sequentially melt the material and at the same time pull out the optical fiber from the insertion hole to coat the outer peripheral surface of the optical fiber with a metal layer. A method for coating optical fiber with metal.