JPH07306329A - Method for reinforcing fusion-spliced part of carbon-coated optical fiber - Google Patents

Abstract

PURPOSE:To provided a method for reinforcing a fusion-spliced part of carbon- coated optical fibers with which the assurance of the reliability equiv., in terms of characteristics, to the reliability of the carbon-coated optical fibers prior to fusion splicing is possible. CONSTITUTION:This method is provided with a stage for forming the carbon- coated fusion splicing part 6, then applying specified tensile load on this carbon- coated fusion-splicing part 6 and a stage for measuring the carbon coat thickness of the carbon-coated fusion-splicing part 6 to discriminate whether the carbon- coated fusion-splicing part 6 is defective or non-defective. Then, the carbon- coated fusion-splicing part 6 is provided with a resin coating after the carbon- coated fusion-splicing part 6 is discriminated to be defective or non-defective and, therefore, both of the initial strength and the hermetic characteristic are assured and eventually the long-term reliability of the characteristics of the carbon-coated optical fiber 1 is surely warranted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reinforcing a fusion spliced portion of an optical fiber which has a coating layer of carbon or the like on the outer periphery of a bare optical fiber and a resin coating portion provided on the coating layer. It is a thing.

[0002]

2. Description of the Related Art In recent years, the stability of optical fiber transmission characteristics,
In addition, high-quality optical fibers having improved long-term reliability of mechanical strength have been developed. One of such optical fibers,
As shown in FIG. 1, there is a carbon-coated optical fiber 1 that has, for example, a carbon coat 3 on the outer circumference of a bare optical fiber 2 and a coating portion 4 made of an ultraviolet curable resin or the like provided thereon. This carbon coated optical fiber 1 is a bare optical fiber 2
Since the carbon coat 3 is provided on the outer periphery of the fiber, the carbon coat optical fiber 1 has a great effect in preventing changes in chemical properties and deterioration of mechanical strength.

In order to use such a carbon-coated optical fiber 1 in an optical cable for a long distance, it is necessary to connect the same as a normal optical fiber to make it longer. The optical fiber is generally connected by fusion splicing, and the carbon-coated optical fiber 1 having the carbon coat 3 is also most reliable by fusion splicing.

[0004]

By the way, in the above-mentioned fusion splicing of the carbon-coated optical fiber 1, the carbon coat 3 disappears due to the heat of arc discharge at the time of fusion. Therefore, the carbon coating 3 after fusion-splicing. Is being regenerated. However, if the regenerated carbon coat 3 does not have a sufficient hermetic function (strength fatigue coefficient), there is a problem that the same reliability as before fusion, for example, strength reliability cannot be guaranteed.

An object of the present invention is to solve the above problems and to provide a method of reinforcing a fusion spliced portion of a carbon-coated optical fiber which can guarantee the same reliability as before fusion in various characteristics.

[0006]

In order to achieve the above object, the present invention has the following means. The method for reinforcing a fusion spliced portion of a carbon-coated optical fiber according to claim 1 of the present invention is to remove the carbon coat at the end of the carbon-coated optical fiber, and fusion-splice the carbon-coated optical fibers from which the carbon coat is removed. Then, the carbon-coated fusion-bonded portion of the fusion-bonded carbon-coated optical fiber is recoated with a carbon coat to form a carbon-coated fusion-bonded portion, and then a constant tensile load is applied to the carbon-coated fusion-bonded portion. A step and a step of measuring the carbon coat thickness of the carbon-coat fusion-bonded portion are provided to determine the quality of the carbon-coat fusion-bonded portion, and a resin coating portion is provided on the outer periphery of the carbon-coat fusion-bonded portion. It is characterized in that the fusion-spliced portion is reinforced by the above.

According to a second aspect of the present invention, in the method for reinforcing a fusion spliced portion of a carbon-coated optical fiber, the step of applying a constant tensile load to the fusion-spliced portion of the carbon coating is performed before the step of measuring the thickness of the carbon coating. It is characterized in that

According to a third aspect of the present invention, in the method for reinforcing the fusion spliced portion of the carbon-coated optical fiber, the carbon coat thickness of the carbon-coated fusion spliced portion is measured by measuring the electric resistance value, and the electric resistance value is It is characterized in that those having an electric resistance value smaller than that of the original carbon-coated optical fiber are regarded as good.

That is, according to the method of reinforcing the fusion spliced portion of the carbon-coated optical fiber of the present invention, heat CV is applied to the surface of the fusion spliced portion.
After the carbon coat is regenerated by the method D or the like, a constant tensile load is applied to remove the low strength portion. Next, the carbon coat thickness of the carbon coat fusion spliced portion is indirectly obtained by, for example, measuring the electric resistance value, and the carbon coat thickness is thinner than the other parts of the carbon coat optical fiber, that is, the electric resistance value is Excludes large ones. For the carbon-coat fusion spliced part that does not pass this screening, the carbon-coat is recoated again. In this screening, it is more effective to measure the carbon coat thickness, for example, to measure the electric resistance after applying a tensile load, in order to guarantee the reliability.

[0010]

In the reinforcing method of the fusion spliced portion of the carbon-coated optical fiber according to claims 1 to 3 of the present invention, the method described above is used after the fusion-spliced portion of the carbon-coated optical fiber is recoated with the carbon coat. A step of applying a tensile load to the fusion splicing part, and measuring the carbon coat thickness of that part,
Specifically, since the process of measuring the electrical resistance value is provided to judge the quality of the fusion spliced part, it is possible to guarantee both the initial strength and the hermetic characteristics (fatigue), and eventually the characteristics such as the optical fiber strength. The long-term reliability of can be surely guaranteed.

According to a second aspect of the present invention, in the method for reinforcing the fusion spliced portion of the carbon-coated optical fiber, the step of applying a constant tensile load to the fusion-spliced portion of the re-coated carbon-coated optical fiber is performed by the carbon coating thickness. Since it is carried out before the step of measuring, the one whose hermetic function is deteriorated due to the damage of the re-carbon coat occurring in the step of applying the tensile load can be excluded in the subsequent step of measuring the carbon coat thickness.

According to a third aspect of the present invention, in the method for reinforcing the fusion spliced portion of the carbon-coated optical fiber, the carbon coat thickness of the carbon-coated fusion spliced portion is measured by measuring the electric resistance value, and the electric resistance is measured. By setting the value that is smaller than the electric resistance value of the original carbon-coated optical fiber as good, it is possible to select the one that has better hermetic characteristics (strength fatigue coefficient) than the original carbon-coated optical fiber.

[0013]

EXAMPLES The present invention will be described in detail below with reference to examples. The same parts as those of the conventional one are designated by the same reference numerals and detailed description thereof will be omitted. The method for reinforcing the fusion spliced portion of the optical fiber according to the present invention is to be spliced first.
The carbon coating 3 is exposed by removing the resin coating portions 4 from the ends of the carbon coating optical fibers 1 and 1 of the book. The end surface of the carbon-coated optical fiber 1 from which the covering portion 4 has been removed is cut to prepare the tip. Normally, the exposed length of the carbon coat 3 is set to about 15 mm. The carbon coated optical fibers 1 and 1 are set in an optical fiber fusion splicing device (not shown), and a voltage is applied to the discharge electrode to generate an arc.
3 is pyrolyzed and removed. The removal length of the carbon coat 3 is made uniform to about 5 mm. After that, the two optical fibers 1 and 1 are set again in a fusion-splicing state, a voltage is applied to the discharge electrode to generate an arc, and the two optical fibers 1 and 1 are fusion-spliced. Since these procedures are similar to the conventional fusion splicing of carbon-coated optical fibers, detailed description will be omitted.

The carbon-coated optical fiber 1 used in the present invention had a carbon coating thickness of 50 nm and a carbon coating electrical resistance value of 20 kΩ / cm was used as a sample. Incidentally, the smaller the electric resistance value of the carbon coat 3, the higher the density of carbon and the thicker the thickness, and therefore the better the hermetic characteristics (strength fatigue coefficient). In the case of the carbon coat 3 synthesized on the surface of the bare fiber 2 by the thermal CVD method at the time of drawing, when the electric resistance value is less than 25 kΩ / cm, the fatigue coefficient n value is almost 100 or more, so that the strength fatigue hardly occurs. Is known and is used as an evaluation standard for hermetic properties.

In the carbon-coated optical fiber 1 which has been fusion-spliced by arc discharge in the above procedure, as shown in FIG. 2, about 5 mm of the carbon-coating 3 has disappeared at the fusion-splicing portion 5, so that The fusion-spliced part 5 was heated by a carbon dioxide gas laser (not shown), and while flowing acetylene gas diluted with nitrogen, the carbon coat 3A was regenerated by the thermal CVD method. The carbon coated fusion spliced portion 6 thus obtained is subjected to a screening test based on the following strengths and electric resistance values, and then the resin is coated and the coating portion 4A is regenerated to reinforce the fusion spliced portion.

(Screening Test 1) After the carbon coat 3A is regenerated on the connection portion 5 fusion-spliced by the above procedure, 2.
A tensile load of 2 GPa was applied to the carbon coat fusion splicing part 6, and the carbon coat thickness was measured, specifically the electrical resistance was measured for those that passed the tensile test, and the resistance value was 20.
Fifty carbon-coated optical fiber fusion-bonded portion samples were obtained in which only the carbon-coated fusion-bonded portion 6 of less than kΩ / cm was reinforced with a resin and the coating portion 4A was applied.

(Screening test 2) After the carbon coat 3A is regenerated on the connecting portion 5 fusion-bonded by the above procedure, 2.
A tensile load of 2 GPa was applied to the carbon-coated fusion splicing part 6, and the electrical resistance was measured for those that passed the tensile test. The electrical resistance value was larger than that of the carbon-coated optical fiber 1 and less than 40 kΩ / cm. Fifty carbon-coated optical fiber fusion-spliced portion samples were obtained in which the carbon-coated fusion-spliced portion was reinforced with a resin and the coating portion 4A was applied.

(Screening test 3) The electrical resistance of the carbon-coated fusion-bonded portion 6 obtained by regenerating the carbon-coat 3A on the connection portion 5 fusion-bonded by the above procedure was measured, and the resistance of the carbon-coated fusion material was less than 20 kΩ / cm. A carbon having a tensile load of 2.2 GPa applied to the connecting portion of the carbon-coated optical fiber 1 with respect to the connecting / connecting portion 6 and a resin which has passed the tensile test and is reinforced with resin to provide the coating portion 4A. Fifty coated optical fiber fusion splicing portion samples were obtained.

(Screening test 4) The electrical resistance of the carbon-coated fusion-bonded portion 6 in which the carbon-coat 3A was regenerated on the connection portion 5 fusion-bonded by the above procedure was measured, and the resistance of the carbon-coated fusion-bonded portion 6 was less than 20 kΩ / cm. Fifty carbon-coated optical fiber fusion splicing portion samples in which the coating portion 4A was reinforced with resin to the splicing portion 6 were obtained.

[0020]

[Comparative Example] The carbon-coated fusion-bonded portion 6 obtained by regenerating the carbon-coat 3A on the fusion-bonded connecting portion 5 according to the above-mentioned procedure was subjected to resin reinforcement for the coating portion to be subjected to neither electric resistance measurement nor tensile test. Fifty carbon-coated optical fiber fusion spliced part samples subjected to 4A were obtained.

Using each of the samples of screening test 1 to screening test 4 and the comparative example, the carbon coated optical fiber fusion spliced portion 6 was immersed in water so that a tensile load of 1.5 GP was applied to the carbon coated optical fiber fusion spliced portion sample.
It was left for a long time in the state of being loaded with a and examined for breakage. The test results are shown in Table 1.

[0022]

[Table 1]

In the screening test 1, no breakage was observed at all, and it can be seen that very high reliability could be guaranteed by the reinforcing method of the fusion spliced part of the carbon-coated optical fiber of the present invention.

In the screening test 2, since the electric resistance value of the carbon coat 3A is set to be larger than that of the other portions, it is impossible to select whether the hermetic function is sufficient or not, and the fracture is caused due to deterioration with time as time passes. You can see that it is moving forward.

In the screening test 3, since the tensile test was carried out later, the damage of the carbon coat 3A caused by the tensile test deteriorated the hermetic function and the portion could not be removed. Was given.

In the screening test 4, since the tensile test is not performed and the strength-deteriorated portion of the fusion spliced portion 5 and the carbon coat 3A is not removed, many of them are set at the time of a long-term test or within a very short time. Is broken, and no break is seen after passing through it.

In the comparative example, not only the breakage occurs at the initial stage of setting but also the breakage progresses with the passage of time, and it is understood that the reliability is not guaranteed at all.

Compared with the comparative example, the screening tests 1 to
In each of the screening tests 3, the number of breakages was small, and the effect in terms of reliability assurance was recognized, but the screening test 1 in particular shows the best results. In addition, although the electrical resistance value of the carbon coat thickness is measured in the above-mentioned examples, for example, as described in JP-A-4-363612, the carbon-coated fusion spliced portion is irradiated with the measurement light. Alternatively, the carbon coat thickness may be obtained by measuring the intensity of transmitted light that passes through the fusion spliced portion.
Further, a method of irradiating the fusion-spliced portion with microwaves and measuring the carbon coat thickness from the intensity of the reflected waves can also be applied.

[0028]

As described above, the claims 1 to 3 of the present invention are as follows.
According to the method for reinforcing the fusion spliced portion of the carbon-coated optical fiber of No. 3, after the carbon coating is recoated on the fusion-spliced portion of the carbon-coated optical fiber that has been fusion-spliced, the step of applying a tensile load and the carbon coating thickness The process of measuring
Specifically, by providing a step of measuring the electric resistance value of the fusion-bonded portion and determining the quality of the fusion-bonded portion, both the initial strength and the hermetic characteristics (fatigue) can be guaranteed,
As a result, long-term reliability such as optical fiber strength can be surely guaranteed.

According to the method of reinforcing a fusion spliced portion of a carbon-coated optical fiber according to a second aspect of the present invention, the step of applying a constant tensile load to the fusion-spliced portion of the recoated carbon-coated optical fiber is performed by carbon. Since the process is performed before the step of measuring the coat thickness, it is possible to eliminate the one whose hermetic function is deteriorated due to the damage of the re-carbon coat occurring in the step of applying the tensile load in the subsequent step of measuring the carbon coat thickness.

According to the method for reinforcing a fusion spliced portion of a carbon-coated optical fiber according to a third aspect of the present invention, the carbon coat thickness of the carbon-coated fusion spliced portion is measured by measuring the electric resistance value, and the electric resistance is measured. By setting the value that is smaller than the electric resistance value of the original carbon-coated optical fiber as good, it is possible to select the one that has better hermetic characteristics (strength fatigue coefficient) than the original carbon-coated optical fiber.

[Brief description of drawings]

FIG. 1 is a side view of a carbon-coated optical fiber which is a target of the present invention.

FIG. 2 is a side view of a fusion splicing portion of a carbon-coated optical fiber which is a target of the present invention.

[Explanation of symbols]

 1 Carbon Coated Optical Fiber 2 Naked Optical Fiber 3, 3A Carbon Coat 4, 4A Coated Part 5 Fusion Spliced Part 6 Carbon Coated Fusion Spliced Part

Claims (3)

[Claims] 1. A carbon-coated optical fiber having a carbon coat at the end thereof removed, and the carbon-coated optical fibers from which the carbon coat has been removed are fusion-spliced together, and the fusion-spliced portion of the fusion-bonded carbon-coated optical fiber is After re-coating the carbon coat to form the carbon coat fusion splicing part, a step of applying a constant tensile load to the carbon coat fusion splicing part, and measuring the carbon coat thickness at the carbon coat fusion splicing part A carbon coat characterized by providing a step for determining the quality of the carbon-coated fusion-bonded portion and providing a resin coating portion on the outer periphery of the carbon-coated fusion-bonded portion to reinforce the fusion-bonded portion. Reinforcing method for fusion spliced part of optical fiber. 2. The fusion splicing of a carbon-coated optical fiber according to claim 1, wherein the step of applying a constant tensile load to the carbon-coated fusion splicing portion is performed before the step of measuring the carbon coating thickness. Part reinforcement method. 3. The carbon coat thickness of the carbon coat fusion spliced portion is measured by measuring the electric resistance value, and the one having an electric resistance value smaller than the electric resistance value of the original carbon coated optical fiber is regarded as good. The method for reinforcing a fusion spliced portion of a carbon-coated optical fiber according to claim 1 or 2, wherein