JPS59168408A - Method for connecting optical fiber by fusion - Google Patents

Abstract

PURPOSE:To reduce the variation in temperature with time and to improve the strength of the connection part by fusion of an optical fiber by providing a subordinate burner in addition to a main burner so as to make the spatial temperature gradient of a heating area gentle and lowering gradually the heating temperature before gas flaming is stopped. CONSTITUTION:The subordinate burners 5 and 5' are provided on both sides of the main burner 3; the temperature distribution when bare fibers 2 and 2' of coated fibers 1 and 1' becomes gentle and the temperature gradient becomes small, so thermal stress is reduced. Further, when the burner flaming is stopped, the burners are put away from the fibers, and in another way, the gas flows of the main and subordinate burners are decreased gradually to lower the temperature of the entire heating area gradually; and then the flaming is stopped to reduce strain and stress due to temperature variation with time, thereby obtaining large effect. Thus, the strain and stress generated in the fibers are reduced to improve the strength of the connection part.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for fusion splicing original fibers, and more particularly to a method for fusion splicing original fibers with high strength.

Conventionally, in the acid layer connection method using gas flame, after removing the M covering, the original fibers whose end faces have been shaped by cutting are notched together, and the vicinity of the butted ends is heated and melted with gas flame to perform fusion splicing. Complete. FIG. 1 is an explanatory diagram of a conventional optical fiber fusion splicing method, in which 1 and 1' are coated fiber cores, 2° and 2' are bare fibers with the rupture removed, 8 is a gas burner, and 4 is a flame splicer. be. According to the conventional fusion splicing method, the strength of the spliced portion is about 0.6 kg, which is low compared to the average fiber strength of 5 kg or more.

The reason for this is thought to be that since the fiber is rapidly cooled immediately after the gas flame is stopped, cracks are generated on the fiber surface due to thermal stress caused by the temperature difference between the heated part and the other parts.

This is because the breakage of the optical fiber connection does not occur at the center of heating, but is concentrated at a location approximately 4 to 5 mm outside the center, and the temperature gradient is at its maximum in this area. It is estimated that

As described above, the conventional connection method has a drawback in terms of reliability because the strength of the connection portion is reduced.

In order to solve the conventional drawbacks, the present invention provides an auxiliary burner in addition to the main burner so that the spatial temperature gradient in the heating region is gentle, and gradually increases the heating temperature before stopping the gas flame. By reducing the temperature change over time, the purpose is to reduce the strength of the optical fiber fusion splice. The major difference from the conventional method is that auxiliary burners are installed on both sides of the main burner, and this effect makes the temperature distribution gentler when heating the fiber.
Since the temperature gradient becomes smaller, thermal stress can be reduced. FIG. 8 shows the temperature distribution according to the conventional method and the temperature distribution according to the burner according to the present invention, where A is the temperature distribution according to the embodiment of the present invention and B is the temperature distribution according to the conventional method.

Comparing the temperature distributions of the two, the temperature distribution in the case of the present invention changes more gently than in the case of the conventional method. In the conventional method, the temperature gradient is maximum at a position approximately 4 to 5 am away from the heating center, and the fracture position when performing a strength test is also at the same position. Furthermore, when the burner diameter was changed in a similar experiment, the fracture position and the maximum temperature gradient position coincided. From this, it is considered that the cause of the strength deterioration in the conventional method is that stress strain occurs due to temperature gradient, which causes fine racks to occur on the fiber surface. Therefore, if the temperature gradient can be reduced, the stress strain caused by this can also be alleviated.

In the embodiment of the present invention, temperature changes are alleviated by heating the position where the temperature suddenly drops in the conventional method using a sub-burner, so that stress strain can be reduced more than in the conventional method.

Furthermore, in addition to the above-mentioned improvements, when the burner flame is stopped, the temperature of the entire heating area can be gradually lowered by moving the burner away from the fiber or by constantly reducing the gas flow rate of the main burner and sub-burner. If the flame is lowered and then the flame is stopped, the stress strain caused by temporal temperature changes can be reduced, which increases the effect. The fiber joint strength can be improved by about 1.5 times using the conventional method.

As explained above, in the original fiber fusion splicing method of the present invention, when fusion splicing optical fibers, the shape of the burner used for heating is structured to alleviate the gradient of temperature distribution, thereby stressing the fibers. Since strain is alleviated, there is an advantage that the strength of the connection portion can be improved.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the conventional optical fiber fusion splicing method, Figure 2
The figure is a perspective view of one embodiment of the present invention, and FIG. 8 is a temperature distribution diagram of the fiber heating section. 1.1'...Coated fiber, 2,2'...Bare fiber, 3...Heating burner (king burner), 4...
・Gas flame, 5.5'...auxiliary burner. Patent applicant Nippon Telegraph Telecommunications Corporation Figure 3

Claims (1)

[Claims] After removing the damage from the 11 pairs of optical fibers to be connected and shaping the end faces, they are butted against each other, heated by a gas flame, and both fibers in a molten state are pushed further, and then the gas flame is stopped. In the optical fiber shoulder connection method, a gas flame burner structure is used in which a main burner is placed at medium heat and a sub-burner having a weaker firepower than the main burner is placed outside the main burner, and when the gas flame is stopped, the heating temperature is gradually lowered. ,after that,
An original fiber fusion splicing method characterized by stopping a gas flame. In the optical fiber fusion splicing method according to claim 1, as a method for gradually lowering the heating temperature, the gas flame burner is kept away from the fiber, and then the gas flame is stopped. Characteristic optical fiber fusion splicing method. & In the optical fiber fusion splicing method according to claim 1, as a method for gradually lowering the heating temperature, the gas flow rate of the main burner and the sub burner is gradually reduced, and then the gas flame is stopped. An optical fiber fusion splicing method characterized by: