JP2999609B2 - Carbon coated optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber having a surface coated with carbon for the purpose of improving water resistance and hydrogen resistance, and more particularly to a colored structure thereof.

[0002]

2. Description of the Related Art Quartz glass-based optical fibers have the problem that transmission loss gradually increases when they come into contact with hydrogen gas or water for a long time. Therefore, hydrocarbons and chlorine-containing hydrocarbons are thermally decomposed and carbon A so-called hermetic-coated optical fiber in which a coating layer is formed and subjected to water resistance and hydrogen resistance treatment has been proposed.

In the case where a large number of optical fibers are converged to form a cable, a colored coating layer is generally provided on the optical fiber for identification of a core. However, when the above-mentioned carbon-coated optical fiber is simply covered with a colored coat layer, the carbon coat layer serving as an underlayer is usually black, so that the black color of the layer interferes with the color of the colored coat layer thereon, There was a problem that a desired surface hue could not be obtained.

[0004]

According to the present invention, in an optical fiber having a black carbon coat layer, a colored layer of a desired color can be formed without being affected by the color of the carbon coat layer serving as an underlayer. It is an object to provide an optical fiber core structure.

[0005]

According to the present invention, there is provided a carbon-coated optical fiber core wire comprising: a white coat layer for hiding the carbon coat color serving as a base layer on an optical fiber having a carbon coat layer on a surface thereof; And a colored coating layer colored in a desired color.

[0006]

When a colored coating layer is simply provided on a carbon coating layer, the underlying color of the carbon coating layer is superimposed on the colored coating layer and the surface visual hue changes from the original colored coating color. Has a white coat layer, which can also be referred to as a color shielding layer of the underlayer, so that the original color of the colored coat layer can be used as the surface hue without being affected by the carbon coat layer.

[0007]

FIG. 1 is a sectional view showing an embodiment of the present invention. In the figure, an optical fiber core 1 has a carbon coat layer 2 coated on the surface of a silica glass-based optical fiber 10 composed of a core and a clad for improving water resistance and hydrogen resistance, and a normally transparent layer provided thereon. Primary coat layer 3, white coat layer 4 for hiding the underlying color,
And a colored coating layer 5 having a desired color for identification of the cords.

As the optical fiber 10, various silica glass optical fibers made of pure quartz or doped quartz can be used. The carbon coat layer 2 may be formed by various conventionally known materials and methods. Particularly preferred embodiments of the carbon coat layer 2 will be described later.

Since the white coat layer 4 is provided for the purpose of concealing the black color of the carbon coat layer as the underlayer so that the black color is not exposed, when the carbon coat layer 2 is covered only with the white coat layer 4, It is desirable that the surface hue be as pure white as possible. However, in the present invention, a slight gray color due to polymerization of the underlying black layer is acceptable. A preferable surface color tone of the white coat layer 4 in a coated state is “JIS Z 8721
The brightness specified in the “three attributes of color” is 7 or more, and particularly preferably 8.5 or more.

As a method for forming the white coat layer 4, for example, a method of applying a white ink obtained by adding a white coloring material such as titanium oxide to an ultraviolet curable resin such as urethane acrylate or epoxy acrylate, or a polyolefin resin such as polyethylene Alternatively, a method of extruding and coating a base resin such as a fluororesin such as PFA, FEP or ETFE mixed with a white coloring material such as titanium oxide may be used. Further, the thickness of the white coat layer 4 is about 1 to 50 μm, preferably about 2 to 10 μm in consideration of the minimum thickness for providing the hidden color effect and the fact that the outer diameter of the optical fiber core is not significantly increased. Appropriate.

As the colored coating layer 5, a material and a forming method which are conventionally generally used for identification of a cord can be applied as they are. For example, there is a method of applying a coloring material in which an organic pigment of a desired color is added to an ultraviolet curable resin such as urethane acrylate or epoxy acrylate. Its thickness is suitably about 3 to 15 μm.

In a preferred embodiment of the carbon coat layer 2, a halogenated hydrocarbon gas or a mixed gas of a halogenated hydrocarbon and a hydrocarbon is used as a carbon coat forming gas, and the gas is drawn from an optical fiber preform. Immediately after that, a carbon coat layer is deposited on the surface of the optical fiber by being thermally decomposed by the residual heat of the optical fiber itself. Since the carbon coat layer formed by such a method can be a dense coating layer, an optical fiber core having such a layer is excellent in water resistance and hydrogen resistance, which is the original purpose, and is a conventional general purpose. With the conventional carbon coat forming method, it is possible to obtain an optical fiber core having excellent mechanical strength, particularly tensile strength, which tends to decrease.

[0013] In general, an optical fiber cable for which identification of the optical fiber is required is an optical fiber cable in which a large number of optical fibers are bundled. The color of the optical fiber is important because of its easiness of identification. Thus, the structure of the present invention, in which the color of the colored coat layer is not visually changed by the color of the underlying carbon coat layer, is particularly useful. The characteristics required for the optical fiber core wire used in such applications include not only water resistance and hydrogen resistance, but also excellent mechanical strength that can withstand the stress generated during cable laying or drum winding / unwinding, particularly Tensile strength. Therefore, in the optical fiber core wire of the present invention, the carbon coat layer of the above embodiment is preferable.

In the method of forming a carbon coat layer in the preferred embodiment, as the halogenated hydrocarbon used, an aliphatic or aromatic hydrocarbon having one or more halogen atoms such as chloro or bromo is used. Specifically, dichloromethane, dibromomethane, trichloromethane, tribromomethane and the like can be suitably used. Alternatively, a mixture of a hydrocarbon such as methane, ethane, propane, and butane, for example, in an amount of 50 to 200 parts by volume with respect to 100 parts by volume of the halogenated hydrocarbon can be suitably used.

An optical fiber is usually manufactured by drawing from a preform heated to 2000 ° C. or higher. Immediately after the drawing, the fiber has a considerable residual heat (about 1000 to 1700 ° C.). The forming gas is thermally decomposed to form a carbon coat layer. The thickness of the carbon coat layer is 300 to 1000 angstroms,
Preferably it is 400 to 600 angstroms.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG. Example An optical fiber preform having a B- and F-doped quartz glass cladding layer on a Ge-doped quartz glass core was placed in a drawing furnace at 2200 ° C. and a linear velocity of 250 m / min, and an outer diameter of 125 μm.
The optical fiber 10 was drawn. Next, the obtained optical fiber 10 was immediately and continuously passed through a quartz glass reaction tube (1 m in length) installed under a drawing furnace, and a carbon coat layer 2 was formed on the surface of the optical fiber. The carbon coat layer 2 is formed by a gas supply port provided in the reaction tube.
Then, a mixed gas of 600 cc / min of dichloromethane gas as a gas for forming a carbon coat layer and 600 cc / min of argon gas as a rare gas was continuously supplied. The thermal decomposition temperature was 1550 ° C., and the thickness of the carbon coat layer 2 thus obtained was 500 Å. An ultraviolet-curable resin liquid was applied thereon and then cured to form a transparent primary coat layer 3 having a thickness of 60 μm.

Thereafter, a white ink formed by adding titanium oxide as a white colorant to urethane acrylate was applied on the primary coat layer 3 to form a white coat layer 4 having a thickness of 4 μm. Further, a color ink formed by adding seven types of color pigments of red, blue, yellow, green, peach, brown, and white to urethane acrylate is applied to each sample, and a colored coating layer having a thickness of 6 μm is formed. 5 was obtained, and optical fibers of seven colors were obtained.

In order to confirm the degree of change in the surface tone of the seven color samples thus obtained, the seven color samples were visually compared with the sample surface colors. As a result, no color difference between the color samples and the color samples was recognized in any of the color samples.

COMPARATIVE EXAMPLE Optical fiber core samples of the above seven colors were produced in the same manner as in the above example, except that the formed white coat layer 4 was not provided. When the surface color of the comparative example product was compared with each color sample in the same manner as above, a color difference (particularly, yellow, peach, and white discolored) considered to be caused by interference of the black color of the carbon coat layer 2 was observed.

[0020]

According to the carbon-coated optical fiber core of the present invention as described above, the color of the carbon-coated layer provided for improving the water resistance and hydrogen resistance of the optical fiber is changed by the color of the core on the surface. Since the white coat layer is provided between these layers so as not to interfere with the color of the colored coat layer for identification, the original color of the colored coat layer can be used as the surface color of the optical fiber. Therefore, the present invention has excellent effects, for example, even when a multi-color optical fiber core is formed into a cable, the core discriminating property is not impaired in a connection operation or the like.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a carbon coated optical fiber core according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber core wire 10 Optical fiber 2 Carbon coat layer 3 Primary coat layer 4 White coat layer 5 Colored coat layer

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Hiroyuki Tanaka 4-3 Ikejiri, Itami-shi, Hyogo Examiner, Itami Works, Mitsubishi Electric Wire & Cable Co., Ltd. Satoshi Fukuda (58) Field surveyed (Int.Cl. ⁷ , DB (Name) G02B 6/44

Claims (1)

(57) [Claims] 1. An optical fiber having a carbon coat layer on its surface is provided with a white coat layer, which serves as a base layer, for hiding the carbon coat color, and a colored coat layer colored in a desired color. A carbon coated optical fiber core, characterized in that: