JPH02287409A - Method for connecting optical fiber - Google Patents

Abstract

PURPOSE:To remove primary coating layers without damaging fiber bodies and to allow thermal welding with high reliability by etching away the primary coating layers, then connecting the end faces of the juncture of the two fibers to each other by the thermal welding. CONSTITUTION:The primary coating layers are etched away and the end faces of the juncture of the two fibers are connected by the thermal welding. Namely, the front end part of the optical fiber 1 coated with a functional thin film 1f consisting of, for example, amorphous carbon is disposed between discharge electrodes 3a and 3b and after the inside of a chamber 2 is evacuated, gaseous O2 is introduced into the chamber and a high-frequency voltage is impressed between the discharge electrodes 3a and 3b to form a plasma discharge electrode A. The thin film of the amorphous carbon is then removed and the optical fiber body is exposed. The butted part of both end faces of the obtained optical fixes are thermally welded to connect the fibers. The primary coating layers 1f can be removed in this way without entailing the troubles, such as the thermal influence on the optical fiber bodies or fusion cutting thereof. The stability and reliability of the thermal welding state at the time of the connection are thus enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for connecting optical fibers, and more specifically,
The present invention relates to a method for removing a primary coating layer formed on the surfaces of mutually connected portions without damaging the fiber body when optical fibers are connected to each other.

(Prior Art) An optical fiber consists of a fiber main body consisting of a core and a cladding, a primary coating layer formed by coating the surface of the fiber body, and a second coating layer formed on the primary coating layer made of a material such as nylon. It is generally composed of a subsequent coating layer.

Here, the primary coating layer is a protective film to prevent the occurrence of surface defects on the fiber body, and at the same time improves the mechanical properties such as flexibility of the optical fiber and improves reliability during long-term use. It has the function of imparting sex. Conventionally, this 1
Silicone resin is often used as the material for the next coating layer.

By the way, when connecting optical fibers to each other, first, the above-mentioned secondary coating layer is peeled off using a wire stripper used for removing the coating of metal conductor cable wires to expose the primary coating layer, and then the primary coating layer is exposed. This primary coating layer is removed by repeatedly squeezing it with gauze soaked in a solvent such as alcohol, and then the mutual end faces of the optical fiber bodies are butted against each other with an axis alignment, and the connection portion is bonded by arc discharge. A method of heat fusion is used.

However, although such a method is possible when the adhesion between the primary coating layer and the optical fiber body is low, it is virtually impossible when the primary coating layer is tightly adhered to the optical fiber body. It is. Moreover, this method has the disadvantage of damaging the surface of the optical fiber body, resulting in a significant reduction in the strength of the optical fiber.

On the other hand, recently, in order to improve the reliability of optical fibers during long-term use, high melting point metals such as W and Mo; amorphous carbon; method, gas phase chemical reaction method (C
Attempts have been made to form functional thin films with a thickness on the order of several thousand layers using film forming techniques such as VD (VD method).

Such functional thin films are dense and have high mechanical strength.
In addition, since it is firmly attached to the optical fiber body, it not only increases the mechanical strength of the optical fiber, but also effectively protects the optical fiber from various atmospheres with different characteristics, increasing its durability. It exhibits an extremely superior function in terms of increasing long-term reliability during use.

(Issue to be Solved by the Invention 1ll) However, since the above-mentioned functional thin film is tightly adhered to the surface of the optical fiber body, it is very difficult to remove it.

It is also possible to connect the optical fibers directly to each other by thermal fusion without removing this functional thin film, but in that case, the optical fiber body (quartz glass) and the functional thin film described above may be connected. A stable and highly reliable fused state cannot be obtained due to differences in physical properties (for example, differences in melting points) between Therefore, in order to remove these thin films, it is necessary to input a large amount of thermal energy into the joint of the optical fiber, but if the input energy is not precisely adjusted, the optical fiber may be damaged as a result. This may lead to melting or deterioration due to heat.

Furthermore, during thermal fusion, part of the functional thin film may segregate as impurities at the connection portion, resulting in a decrease in strength and an increase in optical loss in the connected optical fibers.

The above functionality Tll1l! To remove lI,
For example, this method is sometimes carried out by placing an optical fiber in an arc discharge area and removing it at the high temperature generated there. This will inevitably lead to other inconveniences.

As described above, in the case of optical fibers having a functional thin film as the primary coating layer, it is extremely difficult to remove the primary coating layer prior to splicing, and there is no effective method to remove the primary coating layer without adversely affecting the optical fiber. is unknown to date.

The present invention solves the above-mentioned problems, removes the tightly adherent functional thin film extremely smoothly without any thermal effect on the optical fiber body, and generates stable and reliable heat. The purpose of this invention is to provide an optical fiber connection method that enables fusion splicing.

(Means for Solving the Problems) In order to achieve the above-mentioned object, in the present invention, the primary coating layer formed on the surface of the connecting portion of optical fibers to be connected is removed by etching, and then the mutually connecting A method for connecting optical fibers is provided, which is characterized in that the end faces of the optical fibers are connected by thermal fusion.

Although the method of the present invention can be applied to conventional optical fibers whose primary coating layer is silicone resin, it is extremely effective when applied to optical fibers whose primary coating layer is the functional thin film described above. be.

Etching removal is performed by placing the part where the optical fiber is to be connected in a chamber, creating a gas atmosphere in the chamber that is corrosive to the material of the functional thin film, and corroding the functional thin film with the gas. . At this time, it is effective to bring the gas atmosphere into a plasma discharge state because the etching removal effect is significantly improved.

For example, if the functional thin film is made of amorphous carbon,
It is sufficient to set an Ot atmosphere as the gas atmosphere and to form a plasma discharge state.
In the case of using iC, an N F s atmosphere may be set as the gas atmosphere to form a plasma discharge state.

After removing the functional thin film, the respective optical fiber bodies may be butt-aligned and axially aligned in accordance with a conventional method, and the portions thereof may be heat-sealed.

(Embodiment of the Invention) As shown in FIG. 1, the secondary coating layer 1a of silicone resin was removed at a length of about 10 cm from the tip of the connecting portion of the optical fiber 1. The optical fiber body 1b has a core lc and a cladding l
The surface is coated with a functional film of amorphous carbon having a thickness of approximately 1000 mm.

This optical fiber 1 was airtightly housed in a chamber 2 divided into two via a backing 2a.

In the chamber 2, two discharge electrodes 3a, 3b facing each other with a predetermined interval are arranged, and each discharge electrode 3a, 3
b are each connected to a high frequency power source 4.4, so that plasma can be generated between the two poles.

A rotary pump 5 is connected to the chamber 2 so that the pressure inside the chamber 2 can be reduced to a predetermined pressure.

In addition, a 0□ gas cylinder 6 is installed in the chamber 2,
From here, it flows through the mass flow controller 7! 1
The regulated O gas is allowed to flow into the chamber 2.

After the tip of the optical fiber 1 is disposed between the discharge electrodes 3a and 3b, the rotary pump 5 is activated to exhaust the chamber 2, and the 02 gas cylinder 6 is opened to adjust the mass flow controller 7. By doing so, 0□ gas is introduced into the chamber 2, and the inside of the chamber 2 becomes Q.
, l Torr.

In this state, a high frequency power of 50 W is applied between the discharge electrodes 3a and 3b.
(13,56 MH,) was introduced to form a plasma discharge region A, which was maintained for 100 seconds. The thin film of amorphous carbon was removed at a rate of about 10 people/sec, exposing the optical fiber body.

Since the tip of the obtained optical fiber was exposed to the plasma, that part was cut again (Figure 3). In this way, the amorphous carbon thin film at the tip was removed. The axes of both end faces of the optical fiber 1.1 were aligned and abutted against each other, and the abutted portions were connected by heat fusion (FIG. 4).

When a strength test was conducted on the formed connection portion, no decrease in strength was observed. Also,
There was no optical loss and no deterioration in functionality as an optical fiber occurred.

Example 2 An amorphous SiC thin film was removed using the apparatus shown in FIG. That is, the tip of the optical fiber l is hermetically inserted into the chamber 2, and the cylinder 8a is inserted into the chamber 2.
Cl1Fs gas from cylinder 8b, N2 gas from cylinder 8b,
C1F by adjusting each mass flow controller 9a, 9b.

The gas was diluted to 1% and introduced. The gas introduced and used was processed by a scrubber 11 via a blower 10.

In this state, the heater 12 provided in the chamber 2 was activated to heat the inside of the chamber 2 to about 100''C.

After about 40 seconds, the amorphous SiC thin film 1f was completely removed.

No adverse effects were observed on the optical fibers after treatment, and no deterioration in their functionality was observed even after they were connected as shown in FIG.

(Effects of the Invention) As is clear from the above explanation, according to the method of the present invention, even a functional thin film that is tightly adhered to the optical fiber body can be subjected to high-temperature treatment like conventional arc discharge. It can be removed extremely easily at low temperatures without causing any inconveniences such as thermal effects on the optical fiber body or melting. Further, since no deterioration or the like of the optical fiber body occurs, the thermal fusion state at the time of connection is stable and highly reliable.

The method of the present invention is particularly applicable to removing thin films of various ceramics and metals that are the primary coating layer of the optical fiber body when connecting fluoride fibers, which have been studied as infrared fibers in recent years. It is valid. The reason for this is that all types of infrared fibers are subject to severe high-temperature deterioration.

4,

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the connecting tip of an optical fiber, FIG. 2 is a schematic diagram of an apparatus for carrying out an embodiment of the present invention, and FIG. 3 is a perspective view showing the tip after being etched and removed. , FIG. 4 is a perspective view showing a state in which optical fibers are connected to each other, and FIG. 5 is a schematic diagram of an apparatus for carrying out another embodiment of the present invention. 1... Optical fiber, la... secondary coating layer, lb...
- Optical fiber body, 1c...core, ld...cladding, le. 1f...Functional information 1ll (primary coating layer), 2...Chamber, 2a...Backing, 3a, 3b...Discharge electrode, 4...High frequency power supply, 5...Rotary pump, 6 ...0! Gas cylinder, 7...Mass flow controller, 8a...Cff1FS gas cylinder, 8b...
・N, gas cylinder, 9a+9b...mass flow controller, lO...blower, 11...scrubber, 1
2... Heater.

Claims (3)

[Claims] (1) A method for connecting optical fibers, which comprises etching away the primary coating layer formed on the surfaces of the connecting portions of the optical fibers to be connected, and then thermally fusing the end surfaces of the connecting portions to connect them. . (2) The method for connecting optical fibers according to claim 1, wherein the first coating layer is removed by etching in a plasma discharge region. (3) The method for connecting optical fibers according to claim 1 or 2, wherein the primary coating layer is a thin film of any one of high melting point metal, amorphous carbon, and ceramics.