JPS5893016A - Reinforcing member for connected part of optical fiber - Google Patents

Abstract

PURPOSE:To fix a tension-resistant matter around a bare fiber part evenly and close without virtually causing any expanding contracting force due to the temperature change and to increase the strength of an optical fiber at its connected part, by using the glass having a coefficient of heat expansion approximately equal to that of the optical fiber to the tension-resistant matter and at the same time using numbers of said tension-resistant matters of different lengths. CONSTITUTION:Numbers of glass tension-resistant matters 8' are put between the tubes 7 and 7' of different diameters made of a heat melting adhesive such as EVA, etc. These matters 8' are then put into a heat shirinkable tube 9 made of polyethylene. Thus a reinforcing member is obtained. A core wire of an optical fiber is previously put through the tube 7, and the reinforcing member is shifted to the connected part of the optical fiber after the fiber is melt-stuck and connected. Then the tube 9 is heated up from outside. Thus the tubes 7 and 7' are melted, and the tube 9 shrinks to complete the reinforcement.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reinforcing member for protecting a fusion splice of an optical fiber.

Conventionally, as this type of reinforcing member, one having a structure as shown in FIG. 1 has been used. In Fig. 1, 1 is a heat-shrinkable tube made of polyethylene, and 2 is a hot-melt adhesive (
For example, the tube is made of EVA, ethylene-vinyl acetate), and 3 is a tensile strength member made of metal (for example, a stainless steel rod).

In order to reinforce the connection using this reinforcing member, first insert the fiber core (outer diameter Q, 9 mmφ) into the hot-melt adhesive tube 2 (inner diameter approximately 1.5 to 2.Q mmφ). A bare fiber with the coating removed (e.g. 125 μm in diameter)
After fusion splicing is performed by butting φ) against each other, a reinforcing member is moved to the joint and is heated and shrunk to protect the joint.

FIG. 2 is an explanatory diagram schematically showing the structure of a fusion spliced part after heat shrinkage reinforcement, where 4 is a connected bare fiber, 5 is a fusion splice point of the bare fiber 4, and 6 is an optical fiber. It is the core wire. 2' is a hot-melt adhesive that is melted and filled into the heat-shrinkable tube 1.

In this conventional reinforcing member, the tensile strength member 6 is made of metal and has a larger coefficient of thermal expansion than fiber, so that force is applied to the fiber portion due to temperature changes. In addition, the shape of the reinforcing member after shrinking is as shown in Fig. 2, and the bare fiber 4
The distance between the tension member 3 and the tension member 3 is large, and the role of the tension member cannot be fully fulfilled. Furthermore, there is a drawback that the bare fiber portion may be fixed in a bent state.

In order to eliminate these drawbacks, the present invention uses glass having a coefficient of thermal expansion comparable to that of optical fibers as the tensile strength body, and uses a large number of tensile strength bodies of different lengths. This is what I did.

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 6 schematically shows the structure of an embodiment of the reinforcing member of the present invention, in which (a) is a front view, and (b) is a front view.
It is a sectional view taken along line A-A' of FIG. In the figure, reference numeral 77' denotes a base plate made of hot-melt adhesive, 8 and 8' are glass tensile strength members, and 9 is a heat-shrinkable base. The length of the hot-melt adhesive chip 7' and the tensile strength member 8' is shorter than the length of the fused bare fiber welded part (for example, 60 mm), and the length of the hot-melt adhesive chip 7' and the tensile strength member 8' The length is longer than the length of the bare fiber fused portion.

A procedure for reinforcing the optical fiber connection using the above-mentioned reinforcing member will be explained. First, between the tubes 7 and 7' of different thickness made of hot-melt adhesive such as EVA or nylon, a glass tensile strength body (glass rod diameter is, for example, 0.2 to 0.5
Insert a large number of tubes (mmφ) 8'; furthermore, insert a tensile strength member (glass rod, diameter: 1.Q to 2.Qmmφ) into this tube.
) 8 is inserted into a heat-shrinkable tube 9 made of, for example, polyethylene (thickness is, for example, less than 1 mm) to prepare a reinforcing member of the present invention. Next 9, reinforcing member (total length is about 60mm, for example)
The optical fiber is preliminarily passed through a hot-melt adhesive chip 7 (the inner diameter is the size that the optical fiber will pass through, e.g. 1.0 to 2.0 mmφ), and the fiber is fused. After the connection is made, the reinforcing member is moved to the connection part and heated from the outside of the heat-shrinkable tube 9. By heating, the hot-melt adhesive (cheaps 7, 7') melts, and the heat-shrinkable tube 9 contracts, completing the reinforcement. The thickness of the hot-melt adhesive chips 7, 7' is selected so as to be sufficient to fill the inside of the heat-shrinkable chip 9 after heat-melting.

FIG. 4 schematically shows the structure of the fusion splice after completion of reinforcement according to the present invention, in which (a) is a side view and (b) is a sectional view taken along B-B' in (a). It is. The tensile strength member 8′ is
It is secured closely around the bare fiber 4 by shrinking the outer heat-shrinkable chip 9.

In this embodiment, the number of tensile strength members 8 and 8' is four each, but the number of tensile strength members is not limited to this.

FIG. 5 is an explanatory diagram of the positional relationship between the bare fiber and the tensile strength body. If the diameter of the circle 10 formed by the tensile strength member 8' shown in the figure is set to be slightly larger than the diameter of the fiber core, the tensile strength member will more evenly rotate the bare fiber (fused portion). Fixed. The combination of the number and diameter of the tensile strength members 8' that satisfies this condition is arbitrary. Furthermore, although this embodiment shows the case where the tensile strength member 8' is made of one layer, it is also possible to make it multi-layered.

As explained above, according to the present invention, since glass having a small coefficient of linear expansion comparable to that of an optical fiber is used as the tensile strength member, expansion and contraction forces due to temperature changes are hardly generated. In addition, since a large number of tensile strength members are used and the length of the tensile strength members shorter than the length of the bare fiber part (fused part) is inserted inside the tube, the tensile strength members are placed around the bare fiber part. Since the fibers can be fixed uniformly and close to each other, the fibers are not bent when the heat-shrinkable cheap fibers are contracted, and the strength of the fused portion can be increased. Further, since glass is an insulator, it is possible to easily heat it from within by embedding a heating element such as a nichrome wire inside the glass or wrapping it around the glass.

[Brief explanation of drawings]

Fig. 1 is a front view of a conventional reinforcing member, Fig. 2 is a structural explanatory diagram of a conventional fusion spliced part after reinforcement, and Fig. 6 is a reinforcing member of the present invention, and Fig. 5 (a) is a front view. Figure, (b) is A- of (a)
A' sectional view and FIG. 4 schematically show the structure of the fusion splice after completion of reinforcement according to the present invention, where (a) is a side view and (b) is a side view of (a). B' sectional view and FIG. 5 are explanatory views of the positional relationship between the bare fiber and the tensile strength body. 1...Heat shrinkable Cheap 2...Heat melt adhesive Chee-Pro...Tensile strength body 4...Bare fiber 5...
・Bare fiber fusion splicing point 6...Optical fiber core wire 7.7'...Heat-melt adhesive cheap 8.8'...Tensile strength body 9...Heat-shrink cheap cheap patent application Person Nippon Telegraph and Telephone Public Corporation Patent Attorney Junnosuke Nakamura 1'1 Figure? Figure 2 1' Figure 3 ↑ Figure 4 (Q) Only Figures 1-5 n

Claims (2)

[Claims] (1) A reinforcing member that protects the optical fiber splicing part, including the fusion splicing part where the bare fiber is fused and spliced by removing a predetermined length of the coating of the optical fiber core wire, is attached to the heat-shrinkable tube and the above-mentioned reinforcing member. An optical fiber comprising a heat-melting adhesive inserted into a heat-shrinkable tube and a tensile strength member, the tensile strength member being made of glass having a coefficient of thermal expansion comparable to that of the optical fiber. Connection reinforcement member. (2) A large number of tensile strength members that are longer than the length of the fused part are arranged around a number of tensile strength members that are shorter than the length of the fused part, and a cheapo made of hot melt adhesive and a heat shrink tube are arranged. The optical fiber connecting portion reinforcing member according to claim 1, characterized in that the reinforcing member for the optical fiber connection portion is arranged in advance between.