JPS5924815A - Connecting method of optical fibers by arc welding - Google Patents

Abstract

PURPOSE:To improve the strength in the juncture of optical fibers to be connected by arc welding and to decrease light loss by heating the end parts of the optical fibers to the m.p. thereof or below, and cleaning the fibers by removing the org. materials and moisture sticking on the surfaces thereof then arc welding the end parts. CONSTITUTION:The optical fibers 2 having optical fiber cores 1 to be connected by arc welding are set in a V-groove 4, and the forward end parts thereof are heated to the m.p. of the optical fiber glass or below by a heater 6 for preliminary heating. The org. materials remaining on the surfaces of the fibers 2 without stripping, for example, coatings, etc. are removed and moisture is removed as well to clean the surfaces. The predischarge by electrodes 3 is effected for a short time of about 0.2sec, whereafter main discharge is effected for about 5sec to connect the end parts by melt sticking. The impurities are thus thoroughly removed from the melt-stuck parts by the preheating, and the end faces to be connected are shaped by the predischarge, whereby the joining strength is remarkably improved and the light loss by the connection is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for fusion splicing optical fibers that improves the strength of the fusion splice, which is a particular problem in the fusion splicing of optical fibers.

Technical Background The strength of the connection made by fusion splicing of optical fibers is approximately 500
g, which is the strength of a typical optical fiber core of 1710
It is in a very low strength state as below. One of the reasons for the low strength of this fusion splice is that impurities present near the fusion splice, such as the primary coating of the optical fiber, invade the surface of the optical fiber when the surface of the optical fiber is melted. However, microscopic scratches may occur on the glass surface of the optical fiber, and these microscopic scratches may grow.

Prior Art and Problems A conventional optical fiber fusion splicing method and its implementation are shown in FIG. 1 is an optical fiber core, 2 is an optical fiber, 6 is a frost, a pole, 4 is a V-groove, and 5 is an optical fiber core clamp portion. Optical 7 IPA core wire 1 is nutted into V-groove 4, and the end face of optical fiber 2 to be fusion spliced.
Thereafter, during the main discharge for about 5 seconds, the end surfaces of the optical fibers 2 are pressed against each other in a state in which they are melted to a certain extent to perform fusion splicing. The role of the preliminary discharge in this conventional method is to shape the end face of the optical fiber 2 and to remove impurities such as the primary coating and dust attached to the end face.
j If the radiation time is long, the end face of optical fiber 2 will be completely Y6.
Otherwise, the connection loss will actually increase.
Currently, the pre-discharge time is limited to 0.2 seconds, which is very short compared to the main discharge time. However, with such a short pre-a1j discharge time,
If impurities that cannot be removed remain and adhere to the surface of the optical fiber 2, this impurity will not remain in the optical fiber spliced portion that is melted during fusion splicing, and this remaining impurity will cause the optical fiber 2 to become fused. This will reduce the strength of the optical fiber connection, since it will not be the starting point of the crank when it breaks.

In fact, if the end of the optical fiber 2 is cleaned in advance with sulfuric acid for 4 to 5 minutes to sufficiently remove impurities such as organic compounds adhering to the surface before fusion splicing, the fusion splicing of the optical fiber 2 is possible. The strength of the part becomes about izy, which is about twice the normal strength. This proves that the cleanliness of the glass surface of the optical fiber 2 during fusion splicing is closely related to the strength of the fusion splice. In this way, conventional light-
In the fusion splicing method of 7-aipa, it was difficult to avoid the drawback that the strength of the huj joint was generally extremely reduced.

The purpose of the present invention is to first heat the ends of optical fibers to be fusion spliced at a temperature below the melting point of the optical fiber glass, and then fusion splice Mt, thereby increasing the strength of the fusion splice. An object of the present invention is to provide an improved optical fiber fusion splicing method. The following figure shows the theory ψJ.

Embodiment FIG. 2 shows an optical fiber fusion splicing method and its configuration according to the present invention. The same symbols as in Figure F1 indicate the same parts. Misfire r
The feature of ILL that is different from the conventional one is that the vicinity of the single spliced portion of the optical fiber is heated to a constant temperature υ by a preheating heater 6 before fusion splicing. In one embodiment of the invention,
After heating the surface temperature of the optical fiber 2 to about 200° C. for about 15 seconds, pre-heating is performed for 0.2 seconds as in the conventional method, and then live-heating is performed for 5 seconds to fusion bond. I did it. The strength of the fusion spliced portion at this time was: J1.2Kl.

Here, the major difference between the preheating of the present invention and the conventional predischarge is that the former's preheating is at a temperature below the melting point of the optical fiber glass and takes much longer than the main process. The preliminary discharge is performed at a temperature higher than the melting point of the optical fiber glass, and the time required for the preliminary discharge is extremely shorter than the time required for the main discharge. Furthermore, in terms of contents, the preheating of the present invention can be used to remove organic matter adhering to the surface of the optical fiber, such as removal of a secondary coating, or removal of residues of a buffer layer called a buffer layer, etc. The purpose is to remove. These coatings are removed by heating, and depending on the type of coating, high-temperature heating of 200°C or higher may be necessary, but in any case, heating is not done above the melting point of the optical fiber glass. . On the other hand, the main purpose of preliminary discharge is to shape the optical fiber connection end face, and therefore the temperature needs to be higher than the melting point of the optical fiber glass.

As described above, the preheating according to the present invention is extremely effective as a method for improving the strength of optical fiber fusion joints. Furthermore, if water is adsorbed on glass, its strength tends to decrease, but by heating it before the glass is attached, water existing on the glass surface can be removed and the strength of the optical fiber fusion spliced part can be increased. It plays an important role in improvement.

The present invention can be applied to both single-core optical fibers and multi-core optical fibers, and can also be applied to the connection of optical fibers with a secondary coating.
It is necessary to clean the vicinity of the fusion splice in advance.''A joint can be applied in either case.

Also, as a device to carry out misfire j? , u
It is not limited to automatic interlocking with IF and J for splicing and splicing, but it is also possible to have a configuration that includes a series of manual steps for first preheating with a heater 2 and then fusion splicing. Needless to say.

Effects of the Invention As described above, according to the present invention, the fusion spliced portion of an optical fiber is heated in advance to a temperature below the melting point of the optical fiber, the adhering coating on the surface of the optical fiber is removed, and moisture is removed. The glass surface of the optical fiber fusion splicing part is cleaned by removing the glass surface before fusion splicing, so it is 1 to 1! The strength of the connecting portion can be significantly improved, and the effect is great.

[Brief explanation of drawings]

Fig. 1 shows a conventional optical fiber fusion splicing method and its configuration, and Fig. 2 shows an optical fiber fusion splicing method and its configuration according to the present invention. ...optical fiber, 6.
...Electrode, 4...V groove, 5...Optical fiber core clamp section, 6...Heater for preheating. Special V1/Applicant: Sumitomo 10. Ki Kogyo Co., Ltd. (1 other person)
Representative Patent Attorney Tamamushi 5th Department Figure 1 Figure 2 Continued from Page 1 0 Inventor Osamu Kawata 162 Shirakata Shirane, Tokai Village, Naka District, Ibaraki Prefecture Ibaraki Telecommunications Research Institute, Nippon Telegraph and Telephone Public Corporation 0 Filed People Nippon Telegraph and Telephone Public Corporation

Claims (1)

[Claims] A method for splicing optical fibers with 1 to 11 splices, characterized in that the ends of the optical fibers to be fusion spliced are heated in advance to a temperature below the melting point of the optical fibers, and then fusion spliced 1. Fiber fusion splicing method.