JPS6045209A - Connecting method of optical fiber - Google Patents

Abstract

PURPOSE:To minimize an optical loss of an optical fiber, and to execute easily a permanent connection by using a volatile liquid, rotating a core of a single mode optical fiber, matching the axis, and thereafter, welding by heat the volatilized end face. CONSTITUTION:A fiber strand 11 is engaged into a V-groove of a clamp base 2, and held by a clamp. Each finely moving base 4-6 is matched by adjusting and moving finely fine moving knobs 4a-6a, respectively, observing a terminal of each strand 11. After the matching, ethyl alcohol is supplied into a matching agent holder 12 from a matching agent tank by a pressure pump. The alcohol can recognize visually a core of the strand 11 by an almost equal refractive index. After coincidence of the center lines of cores 11a of each strand 11, the holder 12 is moved, and when the butt part of the strand 11 is melted by an electric discharge between a pair of discharge electrodes 7, 7 after the alcohol has volatilized, its outside circumference and the core 11a coincide exactly and each strand 11 is connected permanently.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for connecting optical fibers in which the eccentric cores of optical fibers are aligned and the end faces of each optical fiber are thermally fused.

(Technical background of the invention and its problems) According to recent optical fiber manufacturing technology, an optical fiber with an extremely small amount of core eccentricity can be obtained. Therefore, in the case of multimode fibers, the fibers can be connected to each other with very small connection loss simply by aligning the central axes of the fibers and heat-sealing each end face.

On the other hand, in a single mode optical fiber, since the core diameter is significantly smaller than the fiber diameter, simply aligning the central axes of the fibers will cause the central axes of the cores to deviate greatly from each other, for example, as shown in equation 71. The connection loss will increase significantly due to the axis misalignment of m.

Therefore, in single mode optical fiber, conventionally,
Core alignment is performed using a transmission power monitoring method that monitors the output power of the fiber terminal, but this method requires multiple operators because the fiber connection position and the fiber monitoring position are far apart. It is very uneconomical because it requires a lot of equipment.

In addition, matching oil with a refractive index almost equal to that of glass is used at the fiber butting part to remove Fresnel reflections on the fiber end face, and the axes are aligned while directly observing the core. The oil method cannot be used for heat fusion splicing.

Furthermore, a method of aligning the core by heat-sealing each end face of the fiber and bending the connection point has been considered, but this method makes it extremely difficult to return the core to a straight line afterwards. Moreover, if the connection point is curved, external stress due to thermal changes etc. will be concentrated at this connection point.

(Object of the Invention) An object of the present invention is to provide an optical fiber connecting method that can easily align the cores of single mode optical fibers and thermally fuse the fibers together with a simple device configuration. be.

(Summary of the Invention) The present invention uses a volatile liquid as a matching agent to align the cores of a single-mode optical fiber by rotating the optical fiber while observing the core position. After that, the end face of the optical fiber is thermally fused.

(Example of the invention) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 and 2 show a heat fusion splicing device 1 used in the splicing method of the present invention. This heat fusion splicing device 1
The fiber clamp stand 2 has a groove 2a, and the clamp stand 2 is connected to a base 3'' with a V groove 2 in the horizontal and vertical directions.
Y-axis fine movement table 4 for fine movement in the extension direction of a
, an X-axis fine movement table 5, a Z-axis fine movement table 6, and a pair of discharge electrodes 77 arranged oppositely between the clamp table 2. Each fine movement table 4 to 6 has a fine movement knob 4a to 6a, respectively. are doing.

The above device configuration is the same as the conventional connection device.

In the thermal fusion splicing device 1 according to the present invention, ZIkl+
A rotation mechanism 8 is provided on the fine movement table 6. This mechanism 8
As shown in FIGS. 2 to 4, the Z-axis fine movement table 6 is arranged concentrically around the clamp table 2 with the V-groove 2a as the center.
As shown in FIG. It includes a projection 10b having a dovetail cross-section, and a fan-shaped rotating plate IO to which the iob is slidably fitted. A coarse rotation knob 10a and a fine rotation knob 10c for sliding the rotation plate 10 are attached to the rotation plate 10, respectively. A clamp stand 2 is fixed to the upper surface of the rotating plate lO. Therefore, when the coarse and fine rotation knobs 10a and 10c are operated to slide the rotation plate 10 along the circumferential surface of the substrate 9, the clamp table 2 rotates and moves around the V-groove 2a.

Incidentally, on the rotary plate IO of the clamp stand 2, there is a fiber wire 11.11 of the single mode optical fiber to be connected, and at the opposite position there is a clamp 2b for grasping the secondary coat to the optical fiber. 2C is installed.

As shown in FIG. 1, a matching agent holder 12 is disposed at the connection position for connecting the fiber strands 11.11, that is, in the middle of the clamp stand 2.2. This matching agent holder 12 is made of a transparent container made of glass.
As shown in the figure, it has an opening 12a that opens on the - side,
The fiber wire 11.11 is inserted through this opening 12a.
is taken in and out of it. A matching agent tank 14 is connected to the back wall of the matching agent holder 12 via a feed pipe 13. This matching agent tank 14 is filled with ethyl alcohol 15 as a matching agent, and this ethyl alcohol 15 is supplied to a pressure pump 16.
The matching agent is supplied into the matching agent holder 12 via the feed pipe 13.

Next, the connection method of the present invention will be explained together with the operation of the heat fusion splicing device.

First, the fiber wires 11 and 11 are respectively inserted into the V-groove 2a, and each fiber wire 11 is secured with the clamps 2b and 2c.
and the secondary coat are fixed to the clamp stand 2.

Next, while observing the end of each fiber strand 11 from above using a microscope 17 (see FIG. 7), each fine movement stage 4 to 6 is adjusted by adjusting the fine movement knobs 4a to 6a to finely move each fiber strand. are aligned based on their outer diameters.

After each fiber strand 11 is aligned, ethyl alcohol 15 is supplied into the matching agent holder 12 from a matching agent tank 14 via a feeding pipe 13 by a pressure pump 16. Since this ethyl alcohol 15 has a refractive index almost equal to that of glass, when observed from above with a microscope, the core 11a of each fiber wire 11 can be seen in FIG.
As shown in a), it can be visually recognized.

By the way, in the fiber strand 11 shown in FIG. 7(a), if the line connecting the heated uneven thickness part and the minimum uneven thickness part of the cladding is the eccentric direction of the core 11a, and the observation direction from the microscope 17 is the line of sight direction. , as shown in FIG. 7(b), by making the eccentric direction orthogonal to the line of sight direction, not only can the position of the core 11a be reliably observed, but also each core 11a can be positioned with the eccentricity of the core 11a being the largest. can.

Therefore, in the method of the present invention, next, the coarse rotation knob 10a is operated to coarsely move the rotation plate 10, and at the same time, the fine rotation knob 10b is operated.
is operated to slightly move the rotary plate 10, thereby rotating and displacing each clamp table 2 around the V-groove 2a, and rotating each fiber strand 11a so that its eccentric direction is perpendicular to the viewing direction. Note that since the substrate 9 is provided with a notch 9a, if the rotary plate 10 is slid to some extent, it will come off from the substrate 9. However, as shown in FIG. 1, the heat fusion splicing device 1 is equipped with two fine rotation mechanisms 8, so the relative rotation angle of the clamp table 2.2 is 360 degrees or more. Therefore, it is possible to fully adjust the rotation of the fiber strands 11.11.

In this way, if the eccentric direction of the core 11a of each fiber wire 11, 11 is made orthogonal to the viewing direction, each core 11a, 11
a can be positioned with the greatest degree of eccentricity. On the other hand, each fiber wire 11 itself is inserted into the V-groove 2a, and aligned with an accuracy of about 10 gm by each fine movement table 4 to 6.
That is, positioning has been performed. As a result, the center axes of the cores 11a, 11a almost coincide with each other due to the above-mentioned positioning by rotation of each core 11a of each fiber strand 11. Therefore, after that, the matching agent holder 12 is moved, and after the ethyl alcohol 15 adhering to the circumferential surface of each fiber wire 11 is volatilized, each fiber wire 11 is caused to discharge between the pair of discharge electrodes 7.7. When the abutting portions of the fibers 11 are melted, the outer periphery and core 11a of each fiber strand 11 are precisely aligned and permanently connected.

If the ethyl alcohol 15 in the matching agent holder 12 evaporates during alignment of the core 11a, this volatile matter is supplied by the pump 16 to ensure a constant amount of ethyl alcohol 15 in the matching agent holder 12 at all times. Do it like this.

In the above example, water in addition to ethyl alcohol 15,
Other alcohols can be used as the matching agent, but any other liquid can be used as long as it evaporates after an appropriate period of time or evaporates when heated and does not affect the fibers by chemical changes.

(Effects of the Invention) According to the present invention, the optical fibers are rotated to align their axes while observing the core position in a volatile liquid, and after the liquid volatilizes, the optical fibers are thermally fused to each other. Even a single mode optical fiber having a core can be connected by aligning the outer periphery and the core. Further, the optical fibers can be easily connected by simply adding a simple mechanism for rotating the optical fibers to the conventional device. Therefore, single-mode optical fibers can be easily and permanently connected while minimizing optical loss without increasing the scale of the device or increasing the number of devices.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the heat fusion splicing device used in the connection method according to the present invention, Fig. 2 is a side view of the same, Figs. 3 and 4 are front and side views of the rotation mechanism, and Fig. 5. is a partially enlarged view of FIG. 4, FIG. 6 is a perspective view showing the matching agent holder and the matching agent supply mechanism, and FIGS. 7(a) and (b) are explanatory views showing the relationship between the eccentric direction and the viewing direction. be. 1-----1 thermal fusion splicing device, 2-----clamp stand, 2a---"-V groove, 3-1----base, 4-----1-Y Axis fine movement table, 5-------X-axis fine movement table, 6-------Z-axis fine movement table, 8----One rotation mechanism, 9---One-board, 10-- -m- Rotating plate, 11-11--Fiber wire, 11a--m-core, 12----Matching agent holder, 14-11--Matching agent tank, 15----- Ethyl alcohol. Figure 3, Figure 4, Figure 5j4 Figure 6, Figure 7 Procedures Amendment C A) Indication of N-1 case 1982 Patent Application No. 152943 2 Name of the invention Method for connecting optical fibers 3 Relationship with the case of the person making the amendment Patent Applicant 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki City (225) Showa Electric Wire and Cable Co., Ltd. Representative: Minoru Yu 4th Director 2-1 Oda Sakae, Kawasaki-ku, Kawasaki City Drawing No. 1 No. 1 subject to amendment No. 6 dated November 29, 1988. Contents of amendment No. 7 Fig. 7 of the drawings is corrected as shown in the attached sheet. Above (a-2 Fig. 7 (b)

Claims (1)

[Claims] 1. A connection method in which each end face of a pair of single-mode optical fibers to be connected is thermally fused after aligning the respective cores, the method comprising: The axes of each core are aligned by rotating the pair of optical fibers while observing the position of each core in a volatile liquid as a matting agent, and after the volatile liquid has evaporated, each end face is thermally melted. A method for connecting optical fibers, characterized by: 2. The method for connecting optical fibers according to claim 1, wherein the volatile liquid is water, ethyl alcohol, or another liquid that evaporates after an appropriate period of time. 3. The optical fiber according to claim 1, wherein the pair of optical fibers are rotated until the eccentric direction of each core is orthogonal to the viewing direction to align the axes of each core. How to connect.