JPS59160114A - Melt sticking and connecting method of optical fiber - Google Patents

Abstract

PURPOSE:To enable a reduction in thermal stress and to improve the strength in the junction of fibers in the stage of melt sticking and connecting the fibers by increasing the distance between the central axis of the fibers and the central axis of discharge electrodes prior to the termination of discharge. CONSTITUTION:The position of an electrode 3 at the point of the time when electric discharge is started is within the same plane as the central axis of optical fibers 2 opposing to each other. The position of the electrode 3 is thereafter moved in a (y)-axis direction. The temp. in a discharge path 4 is highest in the central part and drops on the outside of the path 4. The heating temp. of the fibers drops when the displacement between the fiber axis 2 and the central axis of the electrode 3 is increased. If the moving speed of the electrode 3 is reduced during this time, the abrupt fluctutation in the fiber temp. is prevented and the thermal stress by local heating is decreased.

Description

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

Conventionally, in the fusion splicing method using electrical discharge heating, after the coating of the optical fiber is removed, the end faces are fitted by Q-cutting, and they are butted against each other, and the vicinity of the butted ends of both optical fibers is IJed by electrical discharge. [I i45γf't'ja!;j
L/ is used for fusion splicing.

Figure 1 shows the arrangement relationship between the optical fiber and the radiation electrode when connected using the conventional method.
Reference numerals 2 and 2' are the fibers from which the coating has been removed, 3 and 3' are the discharge electrodes, and 4 is the discharge region.

Figure 2 (a) and Figure 2 (bl are diagrams showing the voltage δ and fiber heating temperature in a time series model in the connection work process, respectively. T1 is the discharge start time, T2
indicates the discharge end time. The fiber heating degree rapidly drops from the discharge end time T2 and returns to the room dry state.

According to the conventional fusion splicing method described above, the splicing strength is about 0.6 IC9 degrees, which is very low, and there are some drawbacks that are not desirable in terms of reliability.

In order to solve the conventional drawbacks, the present invention aims to solve the problems of the conventional fibers by adjusting the distance between the central axis of the optical fibers and the central axis of the discharge load immediately before stopping the heating caused by the electric discharge. The purpose is to provide an original fiber fusion splicing method that improves the strength of the fusion spliced portion of optical fibers by about twice that of the conventional method.

FIG. 3 shows the relative positional relationship between the optical fiber and the electrode during the optical fiber connection process according to the present invention. The electrode position at the time when the emission 1χ starts is in the same plane as the central axis of the opposing optical fiber, as shown in FIG. 3(a).

Thereafter, the positions of the electrodes and poles are moved in the y-axis direction from time T1'. The layout at this time is as shown in Figure 3 (bl).

Figures 4(a) and 4(b) show a time-series model diagram of the voltage at this time and the temperature (temperature) due to the fiber application.
Since the position of the electrode is moved from ', the fiber heating temperature gradually decreases and reaches approximately room temperature slightly after time T2.

This reason is based on the following facts.

Figure 5 (aJ indicates the distance d from the discharge center, Figure 5 (
+) J indicates the fiber heating temperature distribution within the discharge path.

The temperature within the discharge path is highest at the center and decreases at the outside of the discharge path. Therefore, as the displacement between the fiber axis and the center axis of the main discharge pole increases, the fiber heating temperature also decreases.

At this time, the moving paper of the electrode is 1 degree and the heating temperature is 2000 degrees.
If the electrode movement speed during this period is slowed down, rapid fluctuations in the fiber temperature can be prevented2. Because it is rapidly cooled, it is thought that cracks occur due to thermal stress caused by the temperature difference between the heated part and other parts, and the strength decreases.This is because a single break in the optical fiber connection occurs at the center of the discharge. It is estimated experimentally that the discharge occurs concentrated at a location approximately 0.5 mm outside the center.In the connection according to the present invention, the position of the discharge electrode is moved away from the fiber center axis from the middle of the discharge. Because of the upper phase, the temperature of the fiber decreases more slowly than with traditional splices.

Therefore, it becomes possible to reduce the thermal stress caused by local heating and to equalize the temperature.

What about thermal stress in the longitudinal direction of the fiber? The stress caused by the M degree gradient and the temperature difference within the fiber cross section can be considered. In the latter case, when the fiber is cooled in a very short period of time, considering heat transfer, the temperature on the outside of the fiber, that is, the surface of the fiber decreases first, and then the temperature inside the fiber decreases after a certain time delay. Therefore, a temperature gradient also occurs in the radial direction of the fiber during the same time G.

Especially in the case of the present invention, gradually temperature? By lowering the fiber diameter, the thermal stress generated in the fiber radial direction Q can be reduced.

Since experimental studies were conducted based on the present invention, the strength was approximately twice as strong as that of the conventional method.

As explained above, the method of the present invention (according to which, in the fusion splicing of optical fibers, by increasing the distance between the fiber center axis and the center axis of the main discharge pole in a curve that thickens the discharge) Since the fiber can be slowly cooled and thermal stress can be reduced, there is an advantage that the strength of the joint can be improved.

[Brief explanation of drawings]

Figure 1 is a perspective view showing the arrangement of the original fiber and the discharge main pole in conventional fusion splicing, Figure 2 (aJ), (b) is a time-series model diagram of the voltage and heating temperature during the splicing process, 3(a) and (b) are perspective views showing the arrangement of optical fibers and discharge electrodes in one embodiment of the present invention, and FIG. 4(a)
1, (bl is a time-series model diagram of voltage and heating temperature in one embodiment of the present invention, FIG. 5 (aJ is a diagram showing the distance d from the discharge center, and FIG. 1, 1'---7 Ibar core wire 2, 2'---one bare fiber 8, 8'---one discharge electrode 4-m-discharge area. T+ 'T2 (BQ question) Figure 3 (a) (b)

Claims (1)

[Claims] L. Remove the coating of the optical fibers, abut the connecting ends of the bare optical fibers against each other, and heat the connected ends of the bare optical fibers by preliminary discharge. In an optical fiber fusion splicing method, the optical fibers are moved, the two optical fibers in a molten state are bonded together by the heating of the main discharge, and the one optical fiber is further pushed into the other optical fiber, and then the entire discharge is stopped. , the stopping surface of the total discharge + m tt, the direction G in which the central axis of the discharge electrode and the central axis of both fibers move away from each other, the grain spacing of the discharge electrode or the fiber fixing base is changed, and then the total discharge is stopped. Characteristic optical fiber fusion splicing method.