JPH08313767A - Heat resistant optical fiber - Google Patents

Abstract

PURPOSE: To obtain a heat resistant optical fiber having satisfactory hydrogen resistance and reliability over a long period of time. CONSTITUTION: A hermetic coat 1b of amorphous carbon is formed on a glass fiber 1a and a plastic coat 1c is formed on the coat 1b by coating the coat 1b with a UV-curing resin and curing the resin with UV to obtain the objective coated optical fiber 1. Thermosetting silicone resin may be used as the material of the plastic coat 1c. The coated optical fiber 1 is put in a metallic tube 2. A waterproof mixture and/or a hydrogen absorbent may be put in the space in the tube 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant optical fiber which maintains stable characteristics in a high temperature environment for a long period of time.

[0002]

2. Description of the Related Art An optical fiber core wire is usually coated with plastic. However, since the plastic material that covers the optical fiber core wire is easily denatured by heat, it is necessary to use it in a high temperature environment for a long time. , The minimum heat resistant resin such as silicon is used as the coating. However, such an optical fiber is not excellent in mechanical properties and is difficult to use as a single body, so that an optical fiber inserted into a metal tube or the like is generally used. When it is inserted into the metal tube in this way, it is possible to prevent the fiber from breaking and the transmission characteristics from deteriorating due to the thermal deterioration of the coated plastic, but to prevent the transmission loss due to the generation of a minute amount of hydrogen generated from the thermal decomposition of the plastic. There was a problem that the deterioration could not be prevented.

Therefore, a heat-resistant optical fiber having a structure in which an optical fiber coated with plastic is coated on an optical fiber having a hermetic coating is inserted into a metal tube is disclosed in, for example, Japanese Patent Laid-Open No. 3-110508. Known by. In this heat-resistant optical fiber, hydrocarbons are pyrolyzed, an amorphous carbon film is formed on the outer surface of a silica glass fiber element wire, and a polyimide resin film with good heat resistance is provided on the amorphous carbon film. The one used below. The carbon film has a high strength reduction preventing effect and also improves hydrogen resistance.

However, the polyimide resin film is formed by applying a solution containing polyamic acid and drying and curing it in an electric furnace at 500 ° C., which means that the scale of the apparatus for forming the film becomes large. There was a problem.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and in a heat resistant optical fiber used at about 200 ° or less, a heat resistant optical fiber having good hydrogen resistance and long-term reliability is provided. It is intended to be provided.

[0006]

According to a first aspect of the present invention, there is provided a structure in which an optical fiber coated with a plastic having an optical fiber coated with a hermetic coating is inserted into a metal tube. In the heat resistant optical fiber, the plastic coating is an ultraviolet curable resin.

In a second aspect of the present invention, in a heat-resistant optical fiber having a structure in which an optical fiber coated with a plastic coating on an optical fiber having a hermetic property is inserted into a metal tube, the plastic coating is provided. It is characterized by being a thermosetting silicone resin.

According to a third aspect of the present invention, in the heat resistant optical fiber according to the first or second aspect, a waterproof admixture is put in the metal tube.

According to a fourth aspect of the invention, the heat-resistant optical fiber according to the first or second aspect is characterized in that a hydrogen absorbing agent is put in the metal tube.

According to a fifth aspect of the invention, the heat resistant optical fiber according to the first or second aspect is characterized in that a waterproof admixture and a hydrogen absorbing agent are put in the metal tube.

According to a sixth aspect of the invention, in the heat-resistant optical fiber according to the fifth aspect, jelly is used as a waterproof admixture, and a hydrogen absorbent is mixed in the jelly. .

According to a seventh aspect of the invention, in the heat resistant optical fiber according to any one of the first to sixth aspects, a plurality of the optical fiber core wires are inserted. .

According to an eighth aspect of the present invention, in the heat-resistant optical fiber according to any one of the first to seventh aspects, the optical fiber core is a tape core type. is there.

According to a ninth aspect of the invention, in the heat resistant optical fiber according to any one of the first to eighth aspects, the hermetic coating is carbon. .

[0015]

According to the invention described in claim 1, in a heat-resistant optical fiber having a structure in which an optical fiber coated with plastic coating on an optical fiber having hermetic properties is inserted into a metal tube, the plastic coating is , An ultraviolet curable resin. Therefore, when the metal tube is exposed to a high temperature for a long period of time, a small amount of hydrogen, which causes an increase in the loss of the optical fiber, is generated, but the hermetic coating prevents hydrogen from entering the glass fiber portion. The excellent characteristics of the optical fiber with a metal tube can be maintained for a long time. And, since the plastic coating which has sufficient heat resistance at 200 ° or less and which is also used in the general optical fiber core wire is used, it can be coated by a conventional device.

According to the second aspect of the present invention, in the heat-resistant optical fiber having a structure in which the optical fiber coated with the plastic coating on the hermetically coated optical fiber is inserted into the metal tube, the plastic coating is provided. , A thermosetting silicone resin. Therefore, since the hermetic coating prevents hydrogen from penetrating into the glass fiber portion, the excellent characteristics of the optical fiber with a metal tube can be maintained for a long period of time. And, since it has sufficient heat resistance at 200 ° or less and uses a plastic coating which is also used in general optical fiber core wires,
It can be coated with conventional equipment.

According to the third aspect of the invention, since the waterproof admixture is put in the metal tube, it is possible to suppress the generation of hydrogen by reacting moisture or water with the metal tube.

According to the fourth aspect of the invention, since the hydrogen absorbent is put in the metal tube, the hydrogen partial pressure does not rise, and it is possible to prevent the infiltration of hydrogen into the optical fiber.

According to the invention described in claim 5, since the waterproof admixture and the hydrogen absorbent are put in the metal tube, it is possible to suppress the generation of hydrogen by the reaction of water or water with the metal tube. At the same time, the hydrogen partial pressure of the generated hydrogen does not rise, and it is possible to prevent the infiltration of hydrogen into the optical fiber.

According to the sixth aspect of the present invention, since jelly is used as the waterproof admixture and the hydrogen absorbent is mixed in the jelly, the waterproof admixture jelly and the hydrogen absorbing material 3 are made uniform. Can be mixed with each other, and both can be put into the metal tube 2 at once.

According to the seventh aspect of the invention, since a plurality of optical fiber core wires are inserted, the utilization efficiency of the internal space of the metal tube is improved.

According to the eighth aspect of the invention, since the optical fiber core wire is of the tape core wire type, the utilization efficiency of the internal space of the metal tube is improved, and a plurality of optical fiber core wires are put together. It is easy to handle and can be put in.

According to the invention of claim 9, since the hermetic coating is carbon,
Good adhesion to optical fiber and difficult to peel off.

[0024]

1 is an explanatory view of a first embodiment of the present invention, and FIG. 1 (A) is a sectional view of a heat-resistant optical fiber.
(B) is a cross-sectional view of an optical fiber core wire. In the figure, 1 is an optical fiber core wire, 1a is a glass fiber portion, 1b is a hermetic coating, 1c is a plastic coating, and 2 is a metal tube. As the glass fiber portion 1a, a silica glass fiber, a multi-component glass fiber, or the like is used.

The optical fiber core wire 1 will be described first with reference to FIG. In this optical fiber core wire 1, a glass fiber portion 1a is formed with a hermetic coat 1b which is an amorphous carbon coating similar to that of the above-mentioned conventional technique.
An ultraviolet curable resin is applied thereon and cured by ultraviolet rays to form a plastic coating 1c.

The carbon coating has good adhesion to the glass fiber portion 1a and is difficult to peel off. The coating film made of the ultraviolet curable resin has sufficient heat resistance at 200 ° or less and is a plastic coating that is also used in general optical fiber core wires, and thus can be coated with a conventional device.

A thermosetting silicone resin may be used in place of the ultraviolet curable resin, and has sufficient heat resistance at 200 ° or less. And since it is also a common plastic coating, it can be coated with conventional equipment.

The optical fiber core wire 1 described with reference to FIG. 1B is put in a metal tube 2 of stainless steel, titanium, aluminum or the like in FIG. 1A. The inner diameter of the illustrated metal tube 2 is sufficiently larger than the outer diameter of the optical fiber core wire 1, but may be substantially the same. Metal tube 2
Although dry air may be sent into the inner space to prevent water from entering, a waterproof mixture such as jelly may be put in at least a part of the dry air to absorb water or water.

When a heat-resistant optical fiber having a structure in which an optical fiber core wire is inserted into a metal tube is exposed to high temperature for a long time, a small amount of hydrogen, which causes increase in loss of the optical fiber, is generated. As a result, invasion of hydrogen into the glass fiber portion 1a is prevented, so that the excellent characteristics of the heat-resistant optical fiber having the above-described structure can be maintained for a long period of time. Then, the waterproof admixture can prevent the moisture in the cable and the invaded water from reacting with the metal tube to generate hydrogen.

FIG. 2 is a sectional view for explaining the second embodiment of the present invention. The same parts as those in FIG. 3 is a hydrogen absorbing material. This example is
The hydrogen absorbing material 3 is put in at least a part of the space inside the metal tube 2.

When the hydrogen absorbent is added, the partial pressure of hydrogen does not rise and the infiltration of hydrogen into the optical fiber is prevented. In addition,
Even the optical fiber without the hermetic coat 1b has a function of reducing the infiltration of hydrogen. Hermetic coat 1
It is more effective when b is included. Hydrogen absorber 3
At the same time, in this embodiment as well, a waterproof mixture such as jelly may be put in the space inside the metal tube 2. When the hydrogen absorbing material 3 is mixed in the jelly, the jelly, which is a waterproof mixture, and the hydrogen absorbing material 3 can be evenly mixed, and both can be put in the metal tube 2 at once.

As the hydrogen absorbing material, for example, molybdenum trioxide and a mixture of one or more of palladium acetate, palladium acetylacetonate, palladium hydroxide, palladium chloride and chloroplatinic acid can be used. .

FIG. 3 is a sectional view for explaining the third embodiment of the present invention. The same parts as those in FIG. In this embodiment, a plurality of, for example, two optical fiber core wires 1 shown in FIG. Efficiency is improved. Also in this embodiment, the waterproof admixture and / or the hydrogen absorbing material 3 is provided in the space inside the metal tube 2.
May be included.

FIG. 4 is a sectional view for explaining the fourth embodiment of the present invention. The same parts as those in FIG. Reference numeral 4 is an optical fiber tape, 4a is a glass fiber portion, 4b is a hermetic coating, and 4c is a plastic coating. In this embodiment, a plurality of cores, for example, a four-core optical fiber type optical fiber tape 4 is placed in a space inside the metal tube 2. This optical fiber tape 4
Shows a plurality of glass fiber portions 4a each having a hermetic coat 4b and a common plastic coating 4c.

The glass fiber portion 4a and the hermetic coat 4b are respectively described with reference to FIG. 1B, and the glass fiber portion 1a and the hermetic coat 1 are described.
It is the same as that of b, and the material and application method of the plastic coating 4c are the same as those of the plastic coating 1c described with reference to FIG. It is also possible to arrange a plurality of the optical fiber core wires 1 shown in FIG. 1 (B) and apply tape coating with plastic again to form an optical fiber tape. However, by the above-mentioned method, the tape coating with the plastic can be performed once.

Since it is the tape core type, the utilization efficiency of the internal space of the metal tube 2 is improved, and a plurality of glass fibers can be put together, so that it is easy to handle.

Also in this embodiment, the waterproof admixture and / or the hydrogen absorbing material 3 may be put in at least a part of the space in the metal tube 2, and a plurality of optical fiber tapes 4 may be put.

In the first embodiment described with reference to FIG. 1, the test results of a specific example in which stainless is used as the material of the metal tube 2 and carbon is used as the hermetic coat 1b will be described. Using a metal tube and an optical fiber of exactly the same size, a comparative experiment with a conventional type without hermetic coating was conducted. In the measurement period of 1 month and at the measurement wavelength of 1.55 μm, the conventional type shows an increase in loss of 0.1 dB / km, whereas the specific example of the present invention having the hermetic coat does not show an increase in loss and It was possible to confirm the loss increase reduction effect of the invention.

[0039]

As is clear from the above description, according to the present invention, the heat-resistant optical fiber used at about 200 ° or less has the effect of excellent hydrogen resistance and long-term reliability. Since the transmission characteristics in a high temperature environment are extremely stable, it can be installed in, for example, geothermal power generation, concrete during heat generation during curing, power cables, and the like.
It is effective to perform optical communication independently, or to perform communication in combination with conventional wired telecommunication, or to use as an optical fiber for various sensors.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.
FIG. 1A is a sectional view of a heat-resistant optical fiber, and FIG. 1B is a sectional view of an optical fiber core wire.

FIG. 2 is a cross-sectional view illustrating a second embodiment of the present invention.

FIG. 3 is a sectional view illustrating a third embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a fourth embodiment of the present invention.

[Explanation of symbols]

1 ... Optical fiber core wire, 1a ... Glass fiber part, 1b ...
Hermetic coating, 1c ... Plastic coating, 2 ... Metal tube, 3 ... Hydrogen absorbing material, 4 ... Optical fiber tape, 4a ...
Glass fiber part, 4b ... Hermetic coat, 4c ...
Plastic coating.

Claims (9)

[Claims] 1. In a heat-resistant optical fiber having a structure in which an optical fiber coated with a hermetic coating and an optical fiber core coated with a plastic is inserted in a metal tube, the plastic coating is an ultraviolet curable resin. Heat resistant optical fiber characterized by. 2. A heat-resistant optical fiber having a structure in which an optical fiber coated with a plastic having a hermetic coating is inserted into a metal tube, and the plastic coating is a thermosetting silicone resin. A heat-resistant optical fiber characterized in that 3. The heat resistant optical fiber according to claim 1, wherein a waterproof admixture is put in the metal tube. 4. The heat-resistant optical fiber according to claim 1, wherein the metal tube contains a hydrogen absorbing agent. 5. The heat resistant optical fiber according to claim 1, wherein a waterproof admixture and a hydrogen absorbent are put in the metal tube. 6. The heat resistant optical fiber according to claim 5, wherein jelly is used as the waterproof admixture, and a hydrogen absorbent is mixed in the jelly. 7. The heat resistant optical fiber according to claim 1, wherein a plurality of the optical fiber core wires are inserted. 8. The heat resistant optical fiber according to claim 1, wherein the optical fiber core is a tape core type. 9. The heat resistant optical fiber according to claim 1, wherein the hermetic coating is carbon.