JPH04214508A - Method for weld connecting optical fiber - Google Patents

Abstract

PURPOSE:To reduce strain which is caused when optical fibers with deviation of cores are fused. CONSTITUTION:The end surfaces of optical fibers 1a, 1b to be connected are relatively rotated to each other to make the deviated centers of the cores 11a, 11b face each other in one side on the end surfaces. After the distance in the perpendicular direction to the fiber axis between the cores is minimized to a2, both axes of the cores are once aligned and then the axis for the outer diameter is shifted to compensate deviation of the outer diameter axis due to surface tension during melting. Then, arc discharge is started for fusing.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of fusion splicing optical fibers by arc discharge, and more particularly to a method of fusion splicing single mode optical fibers with eccentric cores.

0002

2. Description of the Related Art With the spread of communication transmission lines using optical fibers, optical fiber connection technology has also progressed. Optical fiber splicing requires low splice loss and high mechanical strength of the spliced part, so fusion splicing is mainly used to splice the optical fibers by melting them using the heat of air discharge. It is being In particular, in the case of a single-mode optical fiber, since the core diameter is small, alignment based on the cladding outer diameter does not provide a sufficiently low loss, so it is necessary to align the core with high precision.

[0003] As a method for aligning the core axis, a direct core viewing method is mainly used, in which light is irradiated onto the optical fiber from the side, and when the light passes through the optical fiber, the core and cladding are aligned. A core direct-view type optical fiber fusion splicer has been developed, which uses a TV camera to observe bright and dark images created by the lens effect of the difference in refractive index, and uses image processing technology to detect and align the core position.

By the way, in the case of an optical fiber whose core is eccentric, fusion splicing is performed with the outer diameter axes of the optical fibers 1a and 1b shifted and the cores 11a and 11b aligned, as shown in FIG. 3(A). Then, due to the surface tension of the molten glass, the outer diameter axis moves in a direction that reduces the outer diameter deviation, and as shown in FIG. Connection loss increases.

Therefore, after the core axis alignment is completed as shown in FIG. 4(a), the amount by which the outer diameter shaft returns due to surface tension is predicted in advance and the outer diameter shaft is shifted by that amount, as shown in FIG. 4(b). The method used is to hold the material and then fuse it.

According to this method, after fusion, the outer diameter axis moves and the cores 11a and 11b are almost aligned as shown in FIG. 4(c), so that the connection loss is reduced.

[0007]

However, in the optical fiber fusion splicing method as described above, distortion occurs in the core splicing portion during fusion due to the movement of the core due to movement of the outer diameter axis during fusion. This distortion causes a problem of increased connection loss.

[0008]

[Means for Solving the Problems] The present invention has been made to solve the above problems, and when connecting optical fibers, by rotating the clamp shaft that fixes both optical fibers, After aligning the cores by relatively rotating the end faces of the optical fibers and aligning the eccentric directions of the cores of both optical fibers, the outer diameter is adjusted in advance to account for the amount of core movement due to surface tension. This is a method of fusion splicing by shifting the axis and performing arc discharge.

[0009]

[Operation] The above-mentioned distortion increases as the movement of the outer diameter axis increases, so the distortion increases as the amount of displacement of the outer diameter axis increases. This amount of shift increases as the eccentricity of the core of the optical fiber increases and as the distance between the axes of both cores increases. Of course, optical fibers are manufactured with care taken to minimize core eccentricity, but the smaller the distance between the axes of both cores during connection, the smaller the amount of displacement of the outer diameter axes.

[0010] Therefore, by aligning the eccentric directions of the cores of both optical fibers to be connected as described above, the distance between the core axes of both is reduced, so the amount of deviation of the outer diameter axes set in advance is reduced. I can do it. That is, since the movement of the outer diameter axis due to melting of the optical fiber is reduced, the distortion of the core that occurs is reduced, and therefore the splice loss due to distortion can be reduced.

[0011]

Embodiments Hereinafter, embodiments of the optical fiber fusion splicing method of the present invention will be described.

FIG. 1 is a schematic diagram of a core direct-view type optical fiber fusion splicer used in the example. In the same figure, 1a
, 1b are two optical fibers to be connected, which are linearly butted together with a predetermined interval. 2 is a fusion splicing device main body, 2a and 2b are clamp parts that hold optical fibers,
3 is a control device, and 4 is a control code.

Illumination light from the light source 5 is reflected by a mirror 6 near the abutting portion of the optical fibers and enters the TV camera 7. Reference numerals 8a and 8b denote discharge electrodes, which are disposed facing each other toward the abutting portion of the optical fibers. 9 is a TV monitor, and 10 is a CPU.

FIG. 2 is a sectional view showing the positional relationship between optical fibers on both sides when optical fibers whose cores are eccentric with respect to the outer diameter are spliced using the above fusion splicing apparatus.

In the figure, 1a and 1b are optical fibers to be connected, and 11a and 11b are eccentric cores. First, as shown in (A), when the optical fibers 1a and 1b are butted together and observed on the TV monitor 9, the cores 11a and 1
Assume that the distance between the axes of 1b is a1. Next, by relatively rotating the clamp parts 2a and 2b, the ends of the optical fibers 1a and 1b are rotated as shown in (b), so that the eccentric directions of both cores are made to coincide with each other, as shown in (c). As shown, the distance between the core axes of both optical fibers is reduced to a2. These operations can be automatically adjusted by image processing while being observed on the TV monitor 9.

Thereafter, the cores are aligned as shown in FIG. 4 and fusion spliced in the conventional manner.

[0017]

[Effects of the Invention] According to the optical fiber fusion splicing method of the present invention, by matching the directions of eccentricity of both optical fibers whose cores are eccentric, the eccentricity is substantially reduced. The movement of the outer diameter shaft is reduced, and the generation of strain during core fusion can be suppressed, so that connection loss due to strain can be reduced. As described above, the fusion splicing method of the present invention is particularly effective for single mode optical fibers.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a core direct-view type optical fiber fusion splicer.

FIG. 2 is a cross-sectional view showing the positional relationship of optical fibers in the fusion splicing method of the present invention.

FIG. 3 is a cross-sectional view showing the positional relationship of optical fibers in a conventional fusion splicing method.

FIG. 4 is a cross-sectional view showing the positional relationship of optical fibers in a conventional fusion splicing method.

[Explanation of symbols]

1a, 1b Optical fiber 2　Fusion splicing device main body 2a, 2b Clamp part 7 TV camera 11a, 11b core

Claims (1)

[Claims] [Claim 1] A method for fusion splicing optical fibers using a direct-to-core optical fiber fusion splicing device using arc discharge, in which the end faces of both optical fibers are relatively rotated around their outer diameter axes. After adjusting the eccentricity of the cores at the end faces of both optical fibers and aligning the cores, the outer diameter axis is shifted in advance to account for the amount of movement of the core due to surface tension, and then arc discharge is performed to fuse the fibers. 1. A method for fusion splicing optical fibers, characterized by splicing them.