JPS60122904A - Connecting method of optical fiber - Google Patents

Abstract

PURPOSE:To form a connecting part having a long life by removing a part of a metallic coat of two or more metallic coat optical fibers, welding an exposed part, and thereafter, enclosing the welded part and the exposed part in a metallic vacuum sealed vessel. CONSTITUTION:Metallic coat layers 3, 4 of two metallic coat optical fibers 1, 2 are removed, exposed parts 5, 6 are axially matched and butted, heated and melted, and a welded part 7 is formed. These exposed parts 5, 6 and the welded part 7 are enclosed in a metallic vacuum sealed vessel 8, air is exhausted through an exhaust port 13, and a vacuum space 14 is formed. According to such a constitution, the welded part 7 is completely isolated from the open air atmosphere, its deterioration caused by an invasion of moisture, etc. is prevented, and the connecting part having a long life and a high reliability can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Technical Field The present invention relates to a method for connecting optical fibers used in optical communications, and more particularly, to a method for connecting metal-coated optical fibers in which fiber wires are coated with metal.

Prior art and its problems In an optical f# link system, optical fibers are connected at various locations. For this optical fiber connection,
For example, there are connections between optical fiber terminals during the installation of transmission lines, and connections between intermediate portions of optical fibers during the manufacture of optical fiber couplers, which are frequently used in optical waveguide circuits.

One of the conventional and widely used methods for connecting such optical fibers is to heat-fuse the fiber strands together by means of electrical discharge, etc., and then cover the fused portion with resin. Also, there is a method of reinforcing the material using a cover tube or the like. This connection method improves the mechanical strength of the fused area by reinforcing the fused area, which has deteriorated due to foreign matter or moisture attached during heat fusion, with resin or a cover tube. It is intended to protect from

However, at the connection part i of the optical fiber formed in this way, moisture contained in the reinforcing resin and the part where the reinforcing resin, the cover tube, the coating layer of the optical fiber, etc. overlap, may enter. Moisture accelerates deterioration of the optical fiber tension and fused portion, resulting in a short service life.

■, Purpose of the invention This invention was made in view of the above circumstances.

An object of the present invention is to provide a method for connecting optical fibers that can form a connection with a long waiting life.

■, Specific configuration of the invention Hereinafter, the present invention will be described in detail with reference to the drawings.

Figures 1 to 5 show an example of the optical fiber/< connection method of the present invention in the order of steps. First, prepare two metal coated optical fibers/<1,2.

These metal coated optical fibers (metal coats 1 and 2) 7
It is formed of metals such as 13,4t'i, fluminilum, nickel, copper, and indium, or multiple layers of these metals. And these metal coated optical fibers 1.2
As shown in FIG.
．． 4 is removed and the exposed portion 5 where the fiber wire is exposed
．． 6 is formed.

The metal coating layer 3.4 is removed by a chemical method using acid, alkali, etc., or by an electrochemical method such as electrochemical method. Further, the length of the exposed portion 5.6 may be relatively short, and is usually about 0.5 to I Cm. This is because the metal coat layers 3 and 4Fi have high heat resistance, and there is no risk of deterioration even at high temperatures during fusing of the exposed portions 5 and 6 in the subsequent process.

Next, align the axes of the 7-eye wire in the exposed portion 5.6.

The fused portion 7 is formed by heating and melting this portion, and then abutting each other as shown in FIG. 2. For heating and melting, arc discharge, carbon dioxide laser, oxyhydrogen flame, etc. shown in FIG. 2 are used.

The fused portion 7 thus formed is enclosed in a metal vacuum-sealed container (hereinafter abbreviated as container) 8 as shown in FIG. This container 8, container body 9 and lid 10
Grooves 11, 11 extending in the depth direction are formed on both sides of the container body 9 in the longitudinal direction. In addition, on both longitudinal edges of the lid body 10,
A protrusion 12.12 is provided which fits into this groove 11.11.

The bottom of the groove 11 and the tip of the protruding piece 12 are each formed into a semicircular recess so that a hole having a shape substantially equal to the cross section of the metal-coated optical fiber 1.2 is formed when these are fitted together. 1
1m and 12a are formed. In addition, on the lid lO,
A hollow cylindrical exhaust port 13 used for exhaust, which will be described later, is provided in a protruding manner.

Metal coated optical fiber 1.2# fused as above
i. In such a container body 9, the fused part 7 and the exposed part 5 are attached.
．． 6 is located inside the container body 9, and the portions covered with the metal coating layer 3.4 are the recesses 11a and l1m of the groove 11.11.
It is installed so that it fits into the Thereafter, as shown in FIG. 3, the lid 10 is fitted into the container body 9, and
and the lid body 10 are hermetically joined by brazing, welding, soldering, or other suitable means. Further, the holes formed by the four parts 11a and 12aK on the longitudinal side surface of the container 8 are hermetically sealed by brazing, soldering, or the like.

After the container 8 is formed airtight in this way, the atmosphere inside the container 8 is removed, and the inside of the container 8 is made into a vacuum space 14 with a gas pressure of 10" lvi1 g or less. The inside of the container 8 is evacuated using a vacuum pump. Then, when the gas pressure inside the container 8 reaches a predetermined value, the exhaust port 13 is heated and sealed while exhausting, and the container Ia8 is sealed.
The connection of the metal coated optical fiber 1.2 is completed. At this time, by placing a getter in the container 8 and heating the container Ia8 from the outside after sealing the exhaust port 13, the residual gas in the container 8 is adsorbed by this getter, and the vacuum level in the container 8 is It is also appropriate to increase the

(9) Specific effects and effects of the invention In such a connection method, the fused portion 7 of the resulting optical fiber is placed in a vacuum space of 14 Vr within the container 8, so the fused portion 7 is isolated from the outside air atmosphere. Completely isolated.

Therefore, the fused portion 7 is not deteriorated by moisture or the like. Furthermore, it is known that when an organic substance is exposed to a vacuum, it gradually decomposes and generates water, carbon dioxide, etc. Since only the silica-based fiber wire 5.6 and a small amount of the metal coating layer 3.4 are present, water, carbon dioxide gas, etc. are not generated in the vacuum space 14 due to the decomposition of organic matter, and therefore, due to these, Since the fused portion 7 and the exposed portion 5.6 are not deteriorated, the optical fiber connection obtained by the method of the present invention has a long life.

In addition, a recess 11 region and a recess 12IL are provided on the longitudinal side wall of the container 8.
When the hole formed by , is sealed by brazing, welding, soldering, etc., the intermediate coating layer 3.4 of the optical fiber 1.2 and the container 8 are joined and integrated at the hole. Even if tensile stress is applied to the optical fiber 1.2, the force is also dispersed to the container 8, so the optical fiber connection obtained by this method has excellent strength.

Furthermore, the connection portion of the optical fiber thus obtained is made of gold [11! Since the welded part 7 is protected by the container 8 and is located in a vacuum space 14 to which no heat is transmitted, it can be used even in a high temperature atmosphere of about 60 o'c.

■0 Other specific configurations of the invention In the above description, the original metal-coated optical fiber 1.
Although the connection between the two terminals is shown as an example, the optical fiber connection method of the present invention can also be used for manufacturing optical fiber couplers such as 1:N type or N:N type used in optical waveguide circuits etc. be able to.

Figures 7 and 8 show couplers obtained by the method of this invention.

The coupler 20 shown in FIG. 7 is a 4:4 type coupler, in which the metal coating layer at the intermediate portion of four metal-coated optical fibers is removed to form an exposed portion, and then the exposed portion is removed. 4:4IJjJ coupler 20
It was obtained by enclosing it in a metal vacuum-sealed container 8 for use.

The coupler 21 shown in FIG. 8 is a 1:4 type coupler, in which the metal coating layers at the end portions of five metal-coated optical fibers are removed to form exposed portions, and then the exposed portions are exposed. This was obtained by fusion joining the parts and then sealing them in a vacuum-sealed metal container 8 for a 1:4 type coupler 21.

In addition, in the above explanation, the method of evacuating the atmosphere inside the metal vacuum-sealed container 8 using the vacuum bomb 1 to make the inside of the container 8 a vacuum has been described, but in order to make the inside of the container 8 a vacuum, (i) Furnace brazing using a vacuum heating furnace may also be used.

To create a vacuum using a vacuum heating furnace, first the fused portion 7 of the metal coated optical fiber 1.2 is placed in a container 8 as shown in FIG. This container is on the 8th floor! The shape of the exhaust port 24 is different from that of the container 8 described above, and is formed by punching a hole in the lid 25.

Then, the container 8 in which the metal-coated optical fiber 1.2 is set is further provided with a brazing material 26 around the exhaust port 24, and a closing material for closing the exhaust port 24 on the brazing material 26. After the body 27 is placed, it is placed in a vacuum furnace. In the vacuum heating furnace in which the container 8 is placed, the inside of the furnace is first evacuated, and then the temperature is gradually raised to a temperature at which the brazing filler metal 26 melts.

After the molten brazing filler metal 26 is uniformly distributed around the exhaust port 24 and thereby fills the gap between the closure body 27 and the lid body 25, the vacuum heating furnace is cooled to room temperature. In this manner, the inside of the container 23 is evacuated and sealed, thereby completing the optical fiber connection.

The optical fiber connection section thus obtained is placed in the container 8.
r! on the inner wall of the optical fiber 1.2, the exposed part 5.6 of the optical fiber 1.2, etc. to 5
11 is released and removed when the temperature inside the furnace is increased, so that the vacuum inside the container 8 is improved.

I'11. Example [Actual Example 1] Two graded aluminum-coated optical fibers each having an outer diameter of 175 μm and consisting of a fiber wire having an outer diameter of 125 μm and a core diameter of 50 μm coated with aluminum were prepared. The aluminum coat layer at the end of each of these aluminum coated optical fibers was removed over a length of 10 mm to form an exposed portion. Removal of the aluminum coat layer was performed by electrolysis in a sodium hydroxide solution. After aligning the axes of these two Hikari 7 Eyepa terminals, they were fused together using arc broadcasting. This fused portion was placed in a container 81C shown in FIG. 6, as shown in FIG.

This container is made of aluminum and has a length of 40mm, a width of 4111Rs, a depth of 4mm, the depth of the groove 11 is 2Fm, and the hollow cylindrical exhaust port 13 has an inner diameter of 3Fm. They are formed in order of 20 and 20 heights. The container body and the lid were joined together and the hole through which the optical fiber was inserted was closed by soldering. Next, the inside of the container was evacuated using a vacuum pump, and then the exhaust port was sealed.

The degree of vacuum inside the container was 10″″+*Hg.

The strength of the optical fiber connection obtained in this way is a
For edict, ambient temperature 20℃, 40℃, 60℃1
When a tensile strength test was conducted at 80°C, the average was 3) C1? The elasticity above was obtained. This strength allows ordinary organic coated optical fibers to be coated with conventionally most popular resins.
It is approximately twice as strong as a case connected by a connection method that protects the connection part with a cover tube or the like. From this, it was confirmed that a high-strength connection can be obtained using the connection method of the present invention.

[Example] Eight graded aluminum-coated optical fibers each having an outer diameter of 175 μm and having an outer diameter of 125 μm and a core diameter of 8 μm coated with aluminum were prepared. −
The aluminum coat layer at the end of each of the eight aluminum coated optical fibers was removed to form an exposed portion. These exposed portions were each melted and stretched, and then fused. After that, it was sealed in an aluminum vacuum-sealed container, and the 4:4
A type optical fiber coupler was obtained. At this time, solder was used to hermetically seal the container. Further, the degree of vacuum inside the container was 10 −4 Hg.

Place this coupler in a thermostatic oven and set the humidity of the thermostatic oven to 100%.
TtJ1, and the temperature was changed to -20℃ and 150℃ every 2 hours.
A cycle environment test was conducted for one month in which the temperature was changed to ℃. When comparing the transmission loss before and after the test, no increase in loss was observed, and the coupler obtained by the method of this invention
It has been confirmed that the connection part does not deteriorate due to changes in atmospheric moisture or ambient temperature, and has a long lifespan.

ν11 Effects of the Invention The method for connecting optical fibers of the present invention involves removing a part of the metal coating layer of two or more metal coated optical fibers, and fusing the exposed parts from which the metal coating layer has been removed to each other. After forming the fused part, the fused part and the exposed part are sealed in a vacuum-sealed container, so the fused part and the exposed part are completely isolated from the outside atmosphere by the vacuum space inside the container. protected. Therefore, these parts will not be deteriorated by the intrusion of moisture, etc., and the resulting optical fiber connection will have a long life and high reliability.

[Brief explanation of the drawing]

1 to 5 are explanatory diagrams showing an example of the connection method of the present invention in the order of steps, FIG. 6 is a perspective view showing an example of a container used in the connection method of the present invention, and FIGS. 7 and 8 9 is a schematic configuration diagram showing an example of an optical fiber coupler produced by the connection method of the present invention, and FIG. 9 is a sectional view for explaining another example of the connection method of the present invention. 1.2...Metal coated Hikari 7 Aino (,3,4...
...Metal coat station, 5.6...Exposed part, 7...
... fusion part, 8 ... metal vacuum-tight resistant AT container).

Claims (1)

[Claims] After removing a part of the metal coating layer of two or more metal coated optical fibers and fusing the exposed parts from which the metal coating layer has been removed to each other to form a fused part, and a method for connecting an optical fiber, characterized in that the exposed portion is encapsulated in a gold lIw vacuum-sealed container.