JPH01284805A - Fusion splicing method for optical fiber - Google Patents

Abstract

PURPOSE:To straighten the bend of a fusion splicing part and to improve the mechanical strength by bringing a pair of optical fibers to fusion splicing, and thereafter, heading and softening said optical fibers in an arc discharge, while applying tensile force. CONSTITUTION:In an optical fiber fusion splicing device, a tension mechanism part 18 is provided, and one optical fiber is led into the center part of a fiber supporting part through a cylindrical guide 28, the vicinity of the tip is inserted and held between a pedestal 30 and a clamper 32, and the other is also inserted and held in the same way. After a pair of optical fibers thereof 1, 2 have been brought to fusion splicing by a discharge electrode, one clamper is released and while applying tensile force by the tension mechanism 18, the optical fibers are heated by an arc discharge and by softening the connecting part, the bend is straightened. In this regard, the reason why the arc discharge is used is because the discharge time, etc., are optimized and the given heating value can be set with high reproducibility.

Description

[Detailed Description of the Invention] Summary Regarding a method for fusion splicing optical fibers, the purpose is to fusion splice a pair of optical fibers by bringing their end faces into contact with each other during arc discharge, with the aim of improving the mechanical strength of the fusion splice. After that, while applying a tensile force to the optical fiber from both sides of the fusion splice, the fusion splice or its vicinity is heated and softened in an arc discharge, and the light at or near the fusion splice is softened. It is configured to correct the bending of the fiber.

Industrial applications The present invention relates to a method for fusion splicing optical fibers.

In the field of optical communication or optical transmission that uses optical fibers as optical transmission lines, it is necessary to connect optical fibers to each other in order to install optical transmission lines over long distances. The most common method for permanently connecting optical fibers is a fusion splicing method in which the fiber end faces are brought into contact with each other during high-temperature arc discharge. What is required when implementing this method is that the mechanical strength of the fusion splice and its vicinity is equal to the mechanical strength of other parts, assuming that the loss at the fusion splice does not increase. There should be no significant deterioration in comparison.

BACKGROUND OF THE INVENTION FIG. 8 is a diagram for explaining a conventional fusion splicing method for optical fibers. An optical fiber 94 from which the coating 92 has been partially removed and an optical fiber 98 from which the coating 96 has also been removed are movably supported on the same axis, and their end surfaces are connected between the conical tips of the discharge electrodes 100 and 102. They are brought into contact during the arc discharge that occurs to perform fusion splicing. According to this connection method, since no inclusions such as adhesive are present in the connection portion, it is said that connection with low connection loss and high stability is possible.

Problems to be Solved by the Invention FIG. 9 is a diagram showing a specific state of an optical fiber end face prior to fusion splicing in a conventional method.

In the same figure (a), the end faces of optical fibers 104° and 106 supported coaxially are not necessarily 106° due to polishing precision problems.
It is not perpendicular to the axis as shown by a, but is inclined to the same axis as shown by 104a. In the same figure (b), due to accuracy problems of the optical fiber support mechanism, the shaft 108a of the supported optical fiber 108, 110 is
, 110a are shown inclined to each other. Figure (C) shows that when the cores 112a and 114a of butted optical fibers 112° and 114 are arranged coaxially to reduce loss, since the cores are generally eccentric due to problems in optical fiber manufacturing technology. , shows a state in which a step is formed at the abutting portion. Therefore, when fusion splicing is performed in each of the above states, the fusion splice 116 may be bent, as shown in FIG. 10(a), or the same rI! J(b)
As shown in FIG. 2, bends sometimes occurred at two places on both sides of the fusion splice 116.

On the other hand, when polishing the end face of an optical fiber prior to fusion splicing, the end of the optical fiber is supported by a suitable chuck member, and the end is polished with diamond powder or the like together with the chuck member. A large number of minute scratches are generated on the side surface near the end face of the fusion splice, and as shown in FIG. 11, these scratches remain in the unsoftened portions as shown by 118 on both sides of the fusion splice 1160 even after fusion splicing, as shown in FIG. .

Recently, it seems that countermeasures have been taken based on the idea that the cause of the decrease in mechanical strength of fusion splices is residual thermal stress. The current situation is that mechanical strength is reduced by bends and surface flaws near the fusion splice. For reference, FIG. 12 shows the relationship between tensile strength and bending angle (the angle formed by the axes of fusion-spliced optical fibers).

The tensile strength significantly decreases as the bending angle increases.

The present invention was created in view of such technical problems, and its main purpose is to improve the mechanical strength of the fusion splice and its vicinity by correcting the bending.

Means to solve problems FIG. 1 is a diagram showing the principle of the present invention.

First, as shown in FIG. 5A, a pair of optical fibers 1.2 are fusion-spliced by bringing their end faces into contact with each other during arc discharge.

Next, as shown in FIG. 3(b), the fusion splice 3 or its vicinity is heated by arc discharge while applying a tensile force to the optical fiber 1.2 from both sides of the fusion splice 3. The bending of the optical fiber 1.2 at or near the fusion splicing portion 3 is corrected by softening the optical fiber 1.2.

It should be noted that the shape of the bend of the optical fiber shown in FIGS.

Effect: According to the method of the present invention, the bent portion is softened by applying a tensile force to the optical fiber, so the bent portion is plastically deformed by the action of the tensile force, and the bend is corrected. be done. The reason why arc discharge is used to heat the fusion splice or its vicinity is as follows. In other words, if the bent part is heated too much and becomes extremely soft, the diameter of this part will decrease significantly in relation to the tensile force.
If heating is insufficient and softening is insufficient, plastic deformation will be incomplete and good straightening cannot be achieved, so it is necessary to input an appropriate amount of heat, but arc discharge Accordingly, the optimum amount of input heat can be set with good reproducibility based on the discharge conditions such as the discharge time.

For example, when heating with a burner, it is clear that it is extremely difficult to set the amount of heat input to the portion where the bend occurs.

Example Embodiments of the present invention will be described below based on the drawings.

FIG. 2 is a front view (a) and a side view of an optical fiber fusion splicing apparatus that can be used to implement the present invention. This fusion splicing device includes a fiber support portion 12 for supporting a pair of optical fibers to be fusion spliced in a facing manner, and a discharge electrode for generating an arc discharge in the opposing portion of the optical fibers. The electrode support part 14 is attached to the fiber support part 12 via a shaft 16 so as to be openable and closable. 18
20 is a tensile force applying means for applying a tensile force after fusion splicing via one of the supported optical fibers, and 20 is a means for moving the supported discharge electrode in the y-axis direction perpendicular to the plane of the paper in FIG. 22 is an X-axis micrometer for moving the discharge electrode in the X-axis direction in the horizontal direction in the drawing, and 24 is a microscope for observing the opposing parts of the optical fibers.

FIG. 3 is a plan view of the fiber support section 12 when the electrode support section 14 is opened. One optical fiber is introduced to the center of the fiber support section 12 via a cylindrical guide 28, and the vicinity of its tip is held between a pedestal 30 and a clamper 32. Similarly, the other optical fiber is connected to the guide 34.
It is introduced into the center via the pedestal 36 and the clamper 38 in the vicinity of its tip.

Figure 4 shows the electrode support 14 when the microscope 24 is removed.
FIG. A y-glaze table 42 is movable in the y-axis direction with respect to the main frame 40, and its position is determined by the y-axis micrometer 20. 4
6 is an X that is movable in the X-axis direction with respect to the y-axis table 42.
This is an axis table, and its positioning is performed by an X-axis micrometer 22. 50.52 is the X-axis table 46
A discharge electrode 54 is fixed to a microscope mounting portion in which a hole 56 into which the microscope 24 can be mounted is formed. The tips of the discharge electrodes 50, 52 are formed into a conical shape, so that an arc discharge can be generated by applying an appropriate potential difference between the two electrodes. When the electrode support part 14 is closed with respect to the fiber support part 12, the entire structure is such that the discharge electrodes 50, 52 face the opposing parts of the optical fibers.

A case in which fusion splicing is performed using the fusion splicing apparatus having the above configuration will be explained with reference to FIG. Pedestal 30 and clamper 3
The optical fiber 60 supported by the pedestal 36 and the optical fiber 64 supported by the clamper 38 via the coating 58 are coaxially movably facing each other, and are arranged between the discharge electrodes 50 and 52. Fusion splicing is achieved by butting these end faces together during an arc discharge. In addition, in the figure, in order to ensure the clarity of the drawing, the axes of the discharge electrodes 50 and 52 are shown rotated from their actual positions by 90'' with respect to the axis of the optical fiber ( The same applies to FIG. 6).The fusion splice formed in this way or its vicinity is bent for the reason explained in FIG. 9 or because the optical fibers are pressed against each other from both sides. A method for correcting this bending will be explained with reference to Fig. 6. First, one optical fiber 60 is left supported by the pedestal 30 and the clamper 32, and the clamper 38 is released for the other optical fiber 64, and this light is The side of the fiber 64 opposite to the fusion spliced portion is connected to a tensile force applying means 18.The tensile force applying means 18 is composed of, for example, a pulley 68 and a weight 70. 66 and its vicinity from both sides. Then, the discharge electrodes 50 and 52 are moved to the part where the bend occurs in the X-axis direction to perform arc discharge.
By repeating this process multiple times at the necessary locations, all bends occurring at the fusion splice and its vicinity can be corrected. In this case, if the part irradiated by the arc discharge softens too much, the diameter of that part will decrease and the connection loss will increase, so discharge conditions such as discharge time and application should be adjusted to avoid such inconvenience. It is desirable to set a tensile force.

In this embodiment, a constant load is applied to obtain a constant tensile force, but it is also possible to use the elasticity of the optical fiber itself to displace one optical fiber in the extending direction. Alternatively, the bending may be corrected while moving the discharge electrode at a constant speed in the axial direction (X-axis direction) of the optical fiber. In this way, the surface layer in the vicinity of the fusion splice is softened over the entire range, so that not only the bend is corrected, but also surface flaws can be almost completely eliminated.

FIG. 7 is a diagram showing a modification of the shape of the tip of the discharge electrode. As shown in the figure (a), a flat surface 72 perpendicular to the axis is formed on the tip 74 of the discharge electrode, or a flat surface 76 is formed on the tip 80 as shown in FIG. Furthermore, a conical depression 78 is formed in this flat surface 76. When a discharge electrode with such a tip shape is used, the point of arc discharge moves irregularly, so the spatial range of arc discharge is expanded, and multiple arc discharges or Arc discharge operation becomes unnecessary.

Effects of the Invention As detailed above, according to the present invention, it is possible to improve the mechanical strength by correcting the bending of the optical fiber at or near the fusion splice. Furthermore, since surface flaws are also removed in the portion where the bend has been corrected, this greatly contributes to improving the mechanical strength of the fusion spliced portion and its vicinity.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle of the present invention, Figs. 2 to 4 are diagrams showing an optical fiber fusion splicing device that can be used to implement the present invention, and Fig. 5 is a fusion splicing device using the same device. FIG. 6 is an explanatory diagram when correcting a bend using the same device. FIG. 7 is a diagram showing a modified example of the shape of the tip of the discharge electrode. FIG. 8 is a diagram showing a modification of the shape of the tip of the discharge electrode. Diagrams for explanation, Figures 9 to 1
FIG. 2 is a diagram for explaining the problems of the prior art. 1.2.60.64... Optical fiber, 18... Tensile force applying means, 50.52... Discharge electrode.

Claims (1)

[Claims] After a pair of optical fibers (1, 2) are fusion spliced by bringing their end faces into contact with each other during arc discharge, the optical fibers (1, 2) are spliced from both sides of this fusion splice (3). )
The optical fibers (1, 2) at or near the fusion splice part (3) are heated and softened during arc discharge while applying a tensile force to the fusion splice part (3) or the vicinity thereof.
A method for fusion splicing optical fibers, characterized in that the bending of the optical fibers is corrected.