JP3036884B2 - How to reinforce optical fiber connections - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for repairing a fusion spliced portion of an optical fiber by repairing a thin film.

[0002]

2. Description of the Related Art FIGS. 4A and 4B are cross-sectional views of an example of the structure of an optical fiber. FIG. 4A shows an optical fiber 1 in which a coating layer 12 such as an ultraviolet curable resin is directly provided on a quartz fiber 11. FIG. 4B shows a hermetic optical fiber 1 'in which a coating layer 13 of carbon or the like is provided on a quartz fiber 11 and a coating layer 12 of an ultraviolet curable resin or the like is provided thereon.

In the fusion splicing of these optical fibers, in the case of the optical fiber 1 shown in FIG. 4A, the coating layer 12 at the tip of the optical fiber 1 is removed, and the end face of the quartz glass 12 is cut. The end faces are butted against each other and welded by arc discharge heat, and are connected (11a) as shown in FIG.
Also, in the hermetic optical fiber 1 'shown in FIG. 4B, after removing the coating layer 12 in the same manner as described above, the carbon coating layer 13 at the cut end is removed by a method such as thermal decomposition. The connection (11a) is made in the same manner as described above (b in FIG. 5).

The connection portion of the optical fiber needs to be reinforced with the quartz fiber and the hermetic fiber after fusion splicing as shown in FIGS. 5A and 5B. As a reinforcing method, there are a method using a reinforcing member and a method of molding an ultraviolet curable resin into a connection portion to reinforce the connecting portion. As for hermetic fibers, it has been proposed to recoat carbon on the portion where the hermetic layer has been removed after fusion (see Japanese Patent Application No. 63-282707).

FIG. 6 is an explanatory view of a reinforcing method using a reinforcing member. In this method, as shown in the drawing, a hot-melt adhesive tube 22 and a tensile member 23 in which a fusion spliced optical fiber 11 is inserted are placed in a heat-shrinkable tube 21 and the heat-shrinkable tube 21 is heated. While shrinking, the hot melt adhesive tube 22 is welded,
This is a method for forming a reinforcing portion of the fusion spliced portion of the optical fiber 11.

FIG. 7 is an explanatory view of a method of reinforcing the ultraviolet curable resin with a mold. In this method, the connection portion is set in a mold immediately after fusion splicing, the ultraviolet curable resin 24 is injected into the mold and molded, and the resin is cured to form a reinforcing portion.

[0007]

The process of fusion splicing an optical fiber includes the steps of removing the coating of the optical fiber, cleaning the end face, fixing the optical fiber to a fusion splicing machine, and aligning and connecting the axes. However, in these steps, fine scratches occur on the surface of the quartz fiber and the hermetic layer. These minute scratches reduce the strength of the fusion spliced portion of the optical fiber. Usually, the original strength of a quartz fiber and a hermetic fiber having a diameter of 125 μm φ is about 7 kg, while the strength of a fusion spliced part is reduced to 1/10, which is 0.7 kg.

[0008] The fusion spliced portion is reinforced by the above-mentioned method in the presence of such a small flaw. However, the effect of preventing a certain amount of external stress (tension, bending) by a reinforcing member or the like is effective. Due to external stresses (tensile, bending, lateral pressure) and temperature changes, the inside of the micro scratches gradually grows due to the strain of the material or the intrusion of moisture, and eventually the connection portion is broken.

[0009]

According to the present invention, there is provided an optical fiber connecting portion for preventing a micro-scratch generated in the above-mentioned fusion splicing operation process and a deterioration of the connecting portion due to external stress, moisture intrusion, etc. to the connecting portion. The feature of the present invention is that the linear expansion coefficient in the solidified state is 5 × 10 ⁻⁷ cm / cm / ° C. and the elastic modulus (Young's modulus) is 4 to The object of the present invention is to include a step of forming a film having a thickness of 0.5 to 10 μm using a resin composition having a characteristic of 7 × 10 ¹⁰ N / m ² and reinforcing the film.

FIGS. 1 and 2 are diagrams showing a state in which a reinforcing layer of a resin composition coating film is formed on a fusion spliced portion of an optical fiber. FIG. 1 shows an example of an optical fiber 1 in which a coating layer 12 is directly provided on a quartz glass 11, and FIG. 2 shows a hermetic in which a coating layer 13 such as carbon is provided on the quartz glass 11 and the coating layer 12 is provided thereon. This is an example of the optical fiber 1 '.
In the drawing, reference numeral 11a denotes a fusion splicing portion, 2 denotes a fusion splicing portion 1.
1a is a resin film layer formed by a coating film of the resin composition applied on 1a.

The above resin composition has a linear expansion coefficient of 5 × 10 ⁻⁷ cm / cm / ° C. and an elastic modulus of 4 to 7 × 10 5 in a solidified state.
A material having a characteristic of ¹⁰ N / m ² is used. As a typical example, an organic silicon compound is used. Its properties are a one-part clear liquid with a viscosity of 5 to 10 cp, a specific gravity of 0.9 to 1.0, and a solid content of 20%.

Such an organosilicon compound is applied with feathers on the fusion spliced portion. Immerse the connection in the solution.
The solution is sprayed onto the connection. It is possible to easily perform a thin film coating by such a method. Organosilicon compounds have strong adhesiveness especially to inorganic substances such as metals, glass, and ceramics. When heated, the solvent evaporates, and solids form a cured film. Is integrated with the optical fiber with a characteristic of 5 × 10 ⁻⁷ cm / cm / ° C.

By forming a coating of an organosilicon compound on the fusion spliced portion of the optical fiber, the coating 2 of the organosilicon compound is embedded in the micro scratches A present on the surface of the quartz glass 11 as shown in FIG. Thus, the surface of the quartz glass 11 becomes smooth. Then, by heat-curing this, the solvent component of the organic silicon compound evaporates, and a solid content remains. This solid has a characteristic of a linear expansion coefficient of 5 × 10 ⁻⁷ cm / cm / ° C., which is equivalent to the linear expansion coefficient of glass, and is adhered and integrated with quartz glass. Equally stretches and inhibits wound growth. The coating has an elastic modulus of 4 to 7 × 10 ¹⁰ N / m ^2, which is larger than that of glass. I do.

[0014]

EXAMPLE The present invention was implemented by a method of dipping a fusion spliced part of an optical fiber shown in FIGS. 5A and 5B in an organic silicon compound. First, fine dust and oily components adhering to the fusion spliced portion are removed by washing, and the spliced portion is immersed in an organic silicon compound and slowly taken out. Then, air dry for about 1 minute. Thereby, the organic silicon compound film is formed uniformly by the surface tension. Thereafter, the connection is heated and dried to cure the organosilicon compound. The relationship between time and temperature for curing is as shown in FIG.

[0015] As described above, the organic silicon compound is thermally cured, so that the surface of the quartz glass is 5 × 10 ⁻⁷ cm / c.
An integrated film was formed with a linear expansion coefficient of m / ° C. The organosilicon compound used had a viscosity of 5 cp and a coating thickness of about 1 μm. Further, the tensile strength at break of the fusion spliced portion after the coating is formed is 2 kg (normally 0.7 kg), and the long-term reliability of the spliced portion is significantly improved.

As described above, after the fusion spliced portion of the optical fiber is reinforced, a reinforcing member as shown in FIG. 6 is used, or as shown in FIG. Is the same as before.

[0017]

As described above, according to the method for reinforcing an optical fiber connection portion of the present invention, the micro-scratches and cracks generated in the fusion splicing step of an optical fiber are cured while the resin composition is embedded therein. In addition, since the surfaces are integrated in a smooth state, strength deterioration due to a flaw in the fusion spliced portion is eliminated, and the strength of the spliced portion is significantly improved. In addition, since the fine flaws generated on the surface of the quartz glass or the hermetic layer at the fusion spliced portion are covered with a resin composition film such as an organic silicon compound, the growth of the flaw due to invasion of water or the like can be prevented. The long-term reliability of the department is improved.

[Brief description of the drawings]

FIG. 1 is a view showing a state in which a resin coating layer is formed on a fusion spliced portion of a quartz fiber.

FIG. 2 is a view showing a state in which a resin coating layer is formed on a fusion spliced portion of a hermetic fiber.

FIG. 3 is an explanatory diagram of an operation by forming a resin coating layer on a fusion spliced portion.

FIG. 4 is a cross-sectional view of an example of the structure of an optical fiber.
Is a quartz fiber, and (b) is a hermetic fiber.

5A and 5B are explanatory views of a fusion splicing part of an optical fiber. FIG. 5A shows a quartz fiber, and FIG. 5B shows a hermetic fiber.

FIG. 6 is an explanatory diagram of a method of reinforcing a fusion spliced portion using a strength member.

FIG. 7 is an explanatory diagram of a method of reinforcing a fusion spliced portion with a mold of an ultraviolet curable resin.

FIG. 8 is a diagram showing the relationship between time and temperature during heat curing of an organosilicon compound.

[Explanation of symbols]

1 quartz fiber 1 'hermetic fiber
DESCRIPTION OF SYMBOLS 11 Quartz glass 12 Coating layer 13 Hermetic layer 2 Resin coating layer

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Keiji Osaka 1-chome, Taya-cho, Sakae-ku, Yokohama, Kanagawa Prefecture Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Nobuyuki Yoshizawa 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Japan (56) References JP-A-58-216215 (JP, A) JP-A-58-125006 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B 6 / 255

Claims (1)

(57) [Claims] An optical fiber has a linear expansion coefficient of 5 × 10 ⁻⁷ cm / cm / ° C. and an elastic modulus (Young's modulus) of 4 to 7 × 10 ¹⁰ N / m ² in a solidified state on a fusion spliced portion of an optical fiber. A method for reinforcing an optical fiber connection portion, comprising a step of forming a film having a film pressure of 0.5 to 10 μm using a resin composition having the following characteristics and reinforcing the film.