JPH02263742A - Production of metal-coated optical fiber - Google Patents

Abstract

PURPOSE:To obtain the metal-coated optical fiber from which the metal coating layer is hardly released and having a small initial loss by forming a metallic coat on the quartz-glass optional fiber provided with a carbon coating layer as the outermost layer by electroplating. CONSTITUTION:An optical fiber preform 1 is introduced into a drawing furnace 2 and drawn to obtain an optical fiber consisting of a core 10 and a clad 11. The optical fiber is introduced into a reaction furnace 3 set directly after the drawing furnace 2 to form an amorphous carbon coating layer 12 on its surface, and a carbon-coated optical fiber 4 is obtained. The carbon-coated optical fiber 4 is wound on a bobbin, etc., laid over a feeder 5 and supplied. The fiber is guided by a guide roller 6, etc., and passes through an electrolytic cell 8. A DC current is applied between the carbon coating layer 12 and a platinum electrode 9 by a battery 16 to form a metal coating layer 13 on the optical fiber 4, and the desired metal-coated optical fiber 20 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method of manufacturing a metal coated optical fiber.

[Prior art]

For example, when transmitting information using optical fibers in high-temperature locations such as atomic couplants and chemical plants, the optical fibers used are ordinary silica glass optical fibers coated with metal to improve heat resistance. In many cases, those designed to achieve this are applied.

One known metal-coated optical fiber of this type is one in which a metal coating layer made of, for example, aluminum is provided on the optical fiber.
-207).

By the way, taking the above-mentioned method of manufacturing an aluminum-coated optical fiber as an example, the optical fiber after being drawn is passed through a molten aluminum bath, and an aluminum coating layer is formed by a method called a so-called deimping method.

However, since the aluminum coating layer formed by this dipping method has weak adhesion to the optical fiber, it easily peels off from the optical fiber when the optical fiber is bent with a small bending radius.

In addition, after coating with molten aluminum and cooling and solidifying it, the coefficient of linear expansion of the silica glass optical fiber becomes 0.4.
Xl0-'/'C, whereas that of aluminum is 29XIO-6/'C, which is about 70 times that of the optical fiber, so the shrinkage of the aluminum NN causes the internal optical fiber to micro-bend. As a result, there was also the problem that initial transmission loss (hereinafter referred to as initial loss) increased. Incidentally, this problem is not limited to the case of an aluminum coating layer, but exists to a greater or lesser extent when a metal coating layer is formed by a dipping method.

[Purpose of the invention]

In view of the above problems, an object of the present invention is to provide a method for obtaining a metal-coated optical fiber in which the metal coating layer is difficult to peel off from the optical fiber and in which the initial loss is small.

[Purpose of the invention]

In order to achieve the above object, the present invention is characterized in that a metal coating layer is formed by electroplating on a quartz glass optical fiber having a carbon coating layer as the outermost layer.

[Embodiments of the invention]

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

1 and 2 show an embodiment of the method of the present invention. As these figures show, in the present invention, first, an optical fiber preform 1 is introduced into a drawing furnace 2 by a normal method, and is drawn at a drawing tension of 20 g and a drawing speed of 300 m for 7 minutes, for example. The optical fiber is made up of a core 10 and a cladding 11, and then introduced into a reactor 3 installed immediately after the drawing furnace 2, and an amorphous carbon coating layer 12 of about 500 layers is coated on its surface. An optical fiber 4 with a carbon coating layer having an outer diameter of 125 μm was obtained. Incidentally, when the resistance of this carbon coating layer was measured, it was approximately 10.07 cm.

In forming the carbon coating layer 12 on the optical fiber, a hydrocarbon gas such as C, ll□ is flowed into the reactor 3 together with an inert gas such as He, and this is heated several times in the reactor 3. It can be formed by heating it to 100"C. Of course, it can be formed by other methods as well.

After forming the carbon coating layer 12 in this manner, the carbon coating layer-coated optical fiber 4 is wound around a bobbin or the like (not shown).

Next, this bobbin is hung on the supply device 5 as shown in FIG.
While supplying the carbon at a rate of 0 m/min, the carbon coating layer 12 (this A voltage of 4.5 V is applied between the platinum electrode 9 (positive electrode in this case) placed at the bottom of the electrolytic cell 8 (negative electrode in this case).
Approximately 30% of the DC voltage is applied and the so-called electroplating method
A μl-thick metal coating layer 13 made of copper was formed on the optical fiber 4.

Figure 3 shows the metal coated optical fiber 2 obtained in this way.
FIG.

In the metal coated optical fiber 20 obtained in this way,
The metal coating layer 13 is strongly adhered to the carbon coating layer 12 by Coulomb force through the carbon coating layer 12 which has a high adhesion force to the optical fiber, and as a result, the metal coating layer 20 is attached to a mandrel with a diameter of 15 mm. Even when the metal coating layer 13 was bent along the same direction, no peeling of the metal coating layer 13 was observed.

In addition, this metal coated optical fiber 20 was heated at 700°C for 24 hours.
When the metal coating layer 13 was subjected to a heat resistance test, oxidation was visually observed in the metal coating layer 13, but there was no problem in light transmission characteristics.

In addition, when the initial loss of this metal-coated optical fiber 20 was investigated, there was almost no difference compared to a normal optical fiber.

Incidentally, in the above embodiments, only the case where a copper film is used as the metal coating layer 13 is described, or a film of aluminum, chromium, silver, gold, zinc, tin, etc. is formed on the carbon coating layer 12 by electroplating. Any material that can be formed may be used, and what is formed depends on the metal-coated optical fiber 20.
If necessary, a multilayer metal coating layer 13 made of different metals may be formed.In this case, the electrode on the optical fiber side may be the carbon coating layer 12 or the lower metal coating layer 13. A covering layer 13 is used.

Furthermore, in the above embodiment, the step of forming the carbon coating layer 12 on the optical fiber and the step of forming the metal coating layer 13 on the carbon coating N12 are performed in separate steps, but naturally they are performed in tandem. You can go.

[Effects of the Invention] As described above, according to the method of the present invention, it is possible to obtain a metal-coated optical fiber that is difficult to peel off and has less initial loss.

[Brief explanation of drawings]

FIGS. 1 and 2 are schematic diagrams showing an example of the method for manufacturing a metal-coated optical fiber of the present invention, and FIG. 3 is a cross-sectional view showing an example of a metal-coated optical fiber obtained by the method of the present invention. It is. 1 - Optical fiber base material 3 - Reactor 4 - Optical fiber with carbon coating layer 7 - Copper sulfate aqueous solution 8 - Electrolytic cell 12
~Force-Bonn coating layer 13~Metal coating layer 20~Metal coated optical fiber

Claims (1)

[Claims] A method for manufacturing a metal-coated optical fiber, comprising forming a metal coating layer by electroplating on a quartz glass optical fiber having a carbon coating layer as the outermost layer.