JPS60216317A - Heat-resisting optical fiber unit - Google Patents

Abstract

PURPOSE:To obtain sufficient heat resistance to the repetition of high temperatures or a momentary abnormally high temperature by storing plural optical fibers with a protection coating loosely in a heat-resisting pipe, and providing a protection layer of fiber-reinforced thermosetting plastic around the pipe. CONSTITUTION:Plural optical fibers 2 with a protective coating are stored in the heat-resisting pipe 10 so that a gap 11 is left in it, and the protection layer 5 made of fiber-reinforced thermosetting plastic is arranged outside of the pipe. The plural optical fibers 2 are bundles and the buffer protection layer 3 is formed of silicone rubber or fluororubber in one body to obtain a coated bundle 4 which has a nearly circular section. The pipe 10 is formed by impregnating a paper tape, etc., with thermosetting plastic and then setting the plastic. The gap of the bundle 4 and pipe 10 is so determined that D>=1.04d, where (d) is the external diameter of the bundle 4 and D is the internal diameter of the pipe 10. Consequently, even when this unit is exposed repeatedly at high temperatures in windless summertime or a momentary abnormally high temperature of about 400 deg.C due to, for example, a thunderbolt, there is no cracking generated in the protection layer 5 and this unit is usable for OPGW (optical composite overhead earth-wire), etc.

Description

[Detailed Description of the Invention] [Technical Field] The present invention significantly improves heat resistance, especially in optical fiber units used in optical composite overhead ground wires (hereinafter referred to as 0PGW), which require high strength and high heat resistance. The present invention relates to a heat-resistant optical fiber unit that has been improved.

[Prior art]

In recent years, so-called OPCW, which has an optical fiber unit built into or attached to the overhead ground wire that is installed between power transmission towers, has become widely used for communication between power plants and substations. Ta. By the way, this 0PGW
Due to the nature of its use, the optical fiber unit used for this purpose must not only have high strength to withstand vibrations from wind and other factors, but also must have excellent heat resistance.

Incidentally, the typical thermal environmental conditions under which 0 PGW occurs are, first of all, midsummer, when there is no wind, and at the same time, the maximum current is flowing through the power transmission line.

At this time, the induced current flowing in the overhead ground wire reaches its maximum, and it is said that, for example, in a power transmission network of about 500,000 KV, the temperature of the entire 0PGW will rise to about 150°C.

Second, when a ground fault occurs due to lightning, a flash current flows through the overhead ground wire, and a high temperature state of about 1100° C. occurs instantaneously before the circuit breaker operates. In this way, 0PGW is in an environment where it is repeatedly exposed to temperatures of approximately 150° C., which is expected to last for several hours in the worst case, and to abnormally high temperatures of approximately 400° C., albeit instantaneously. Therefore, the optical fiber unit built into or attached to the overhead ground wire must be able to withstand the above environment. Now, as a heat-resistant optical fiber unit for opGw used in such an environment, the one shown in FIG. 3 has been widely known. This heat-resistant optical fiber unit 1 is made by twisting together a plurality of optical fibers 2 each having a protective coating such as silicone rubber, which is integrally coated with a buffer protection layer made of silicone rubber or the like and having a roughly circular cross section. A covered aggregate is formed, and a protective layer 5 made of fiber-reinforced thermosetting plastic made of epoxy resin containing glass fiber or the like is provided on the outside of the covered aggregate. However, the fifth
When the conventional heat-resistant optical fiber unit 1 shown in the figure is repeatedly subjected to the above-mentioned high temperature, a rack 6 is gradually formed in the outer protective layer 5 as shown in FIG. It is known that the mechanical strength of the heat-resistant optical fiber unit 1 is significantly reduced as a result.

The reason for this is that the coefficient of thermal expansion of the inner buffer protective layer is greater than that of the outer protective layer 5, so when the heat-resistant optical fiber unit 1 is exposed to high temperatures, the outer protective layer 5 As a result, stress due to thermal expansion of the inner buffer protection layer 5 acts in the direction of the arrow in FIG. Therefore, if it is repeatedly exposed to high temperatures, it will be subjected to the above-mentioned stress repeatedly, and as a result, the weak parts of the outer protective layer 5 will become fatigued and cracks 6 will occur.

In this way, in the conventional heat-resistant optical fiber unit for 0PGW, if it is repeatedly exposed to the above-mentioned high temperatures,
The protective layer made of fiber-reinforced thermosetting plastic is torn.
As a result, there is a problem that the mechanical strength necessary for 0PGW is lost.

[Purpose of the invention]

In view of the above-mentioned problems, the purpose of the present invention is to reduce the risk of repeated exposure to extremely high temperatures of approximately 150°C, which are expected to last for several hours in the worst case, during midsummer periods of no wind, and to abnormally high temperatures of instantaneous qoo°C, which occur during lightning ground faults. Another object of the present invention is to provide a heat-resistant optical fiber unit that has excellent heat resistance so that the protective layer made of fiber-reinforced thermosetting plastic will not tear.

[Structure of the invention]

In order to achieve the above object, the heat-resistant optical fiber unit of the present invention includes a plurality of optical fibers having a protective coating, a heat-resistant pipe that accommodates the plurality of optical fibers with a gap, and a heat-resistant optical fiber unit of the pipe. It is characterized by comprising a protective layer made of fiber-reinforced thermosetting plastic provided on the outside.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the heat-resistant optical fiber unit of the present invention.

As shown in FIG. 1, first, a plurality of optical fibers 2 having a protective coating such as silicone rubber are twisted together, and a buffer protection layer 5 made of silicone rubber or fluorine rubber is integrally applied thereto, and the cross section is approximately circular. The material is coated to form a coated aggregate. When a plurality of optical fibers 2 are twisted together, an intervening string or the like is twisted together as appropriate,
The twisted cross section may be circular. Now, the covered assembly 4 formed in this way is made by bonding, for example, a thermosetting plastic such as an epoxy resin or fest with excellent heat resistance to a heat-resistant tape such as paper tape, Manila hemp tape, or aromatic polyamide fiber nonwoven fabric. The tape is coated or impregnated in advance as an agent, and the tape is rolled into a pipe shape, and then heat is applied to harden the thermosetting plastic and stored in a heat-resistant pipe 10 with voids 11. be done. And this heat resistant pipe 1
A protective layer 5 made of a fiber-reinforced thermosetting plastic such as an epoxy resin containing elongated heat-resistant reinforcing fibers such as glass fibers, carbon fibers, or aromatic polyamide fibers is provided on the outside of the 0. Here, the void 11 preferably has a void amount that occurs when D≧1.0 I+ 6, where the outer diameter of the covered assembly 11 to be accommodated is d1 and the inner diameter of the pipe 10 is D. This was obtained as a result of the inventors conducting various tests such as heat cycle tests. In addition, when the cross section of the covered assembly 4 is not circular, the equivalent diameter may be calculated from the cross-sectional area, and the inner diameter of the pipe 10 may be determined so that D≧1.046.

In the heat-resistant optical fiber unit thus formed,
One method for storing the covered assembly in the heat-resistant pipe 10 will be explained with reference to FIG.

As shown in FIG.
The supply 17 is passed through a nipple 16 whose outer diameter is equal to the inner diameter of the heat-resistant pipe 10, and is guided to a winder (not shown) in the direction of the arrow in the figure.
．． 17. For example, 1g of paper tape, Il
l! Apply liquid phenol to the adhesive side of the paper tape 18.18. The pheno is applied to the adhesive side of the tape 18.18 using a rotating roll 20.20, a part of which is submerged below the liquid surface of a liquid tank 19.19 that stores liquid pheno. But then paper tape ill! , I
II! into the nipple 16 and the paper tape 18.
18 is rolled into a pipe shape on the nipple 16 by the frictional force generated by the rotation of the belt 22 rotating in the direction of the arrow by the drive rotating rolls 21, 21, and the sheets of paper to be wrapped with the applied liquid pheno are adhered to each other. Subsequently, the liquid phenol is heated and hardened by the heater 23, and the paper pipe is wound up by a winding machine together with the coated assembly housed inside with a gap. In addition, as mentioned above, paper tape Ill! , 1g is hardened by heat-cured phenol, so it is quite hard even though it is a paper pipe.Therefore, the outside of this pipe 10 is protected by fiber-reinforced thermosetting plastic. Even if layer 5 is provided, due to the radial pressure generated at that time,
This pipe 10 will not be crushed.

As mentioned above, the heat-resistant optical fiber unit of the present invention, which is constructed as described above, can be used at high temperatures of approximately 150°C that are expected to last for several hours at the worst time of midsummer, or during lightning-induced ground faults. Even if it is repeatedly exposed to abnormally high temperatures of approximately 100°C, the coated assembly containing multiple optical fibers is housed in a heat-resistant pipe with gaps, so
Even if this covered assembly thermally expands, it will not press the outer protective layer made of fiber-reinforced thermosetting plastic from the inside. The force due to thermal expansion is absorbed by the voids, and as a result, the protective layer does not crack or tear in the longitudinal direction, and its mechanical strength is not impaired.

〔Concrete example〕

In a specific example of the present invention, first, seven optical fins (with an outer diameter of 30 μm) coated with silicone rubber or the like are twisted together, silicone rubber is coated and baked so that the cross section becomes approximately circular, and a buffer protection layer is formed. A coated aggregate with an outer diameter of about 0.9 mm is obtained.While supplying this,
thin-walled metal) tube (inner diameter 0.95 mm, outer diameter 1.2 +
At the same time, an epoxy resin prepreg (semi-cured resin) is attached to two sheets of aromatic polyamide Nomex tape with a thickness of 25 μm on the outside of the nipple. The contacting sides are coated and impregnated, and wound with the seam positions shifted by A pitch. Then, the prepreg is heated at 120 to 180°C using a heater to completely cure the prepreg, and the inner diameter is 1.
．． Form a pipe with a diameter of 20 mm and an outer diameter of approximately 128 mm. After forming the pipe that houses the covered assembly with a void inside, the pipe is finally coated with a protective material made of a thermosetting resin containing long glass fibers, such as epoxy unsaturated polyester, on the outside of the pipe. A heat-resistant optical fiber unit having an outer diameter of about 23 mm was obtained by forming layers.

〔Effect of the invention〕

As described above, according to the present invention, even if the fibers are repeatedly exposed to a high temperature of about 150°C, which is expected at the worst time, and an instantaneous abnormal high temperature of about 1100°C, which is caused by a lightning ground fault, in windless conditions in midsummer, A heat-resistant optical fiber unit with excellent heat resistance can be obtained without cracking the protective layer made of reinforced thermosetting plastic.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the heat-resistant optical fiber unit of the present invention, and FIG. 2 is a schematic diagram showing an embodiment of the method for manufacturing the heat-resistant optical fiber unit of the present invention shown in FIG.
FIG. 5 is a cross-sectional view showing a conventional heat-resistant optical fiber unit, and FIG. 5 is an explanatory diagram for explaining the problems of the conventional heat-resistant optical fiber unit 71. DESCRIPTION OF SYMBOLS 1...Heat-resistant optical fiber unit, 2...Optical fiber, U...Buffer protection layer, 11...Coated assembly, 5
...protective layer, 6...crack, 10...pipe,
11...Gap, 16...Nipple, 21...Drive rotating roll Fig. 1 0 Fig. 3 Hill Fig. 4

Claims (3)

[Claims] (1) Protection consisting of a plurality of optical fibers with a protective coating, a heat-resistant pipe that accommodates the plurality of optical fibers with gaps, and a fiber-reinforced thermosetting plastic provided on the outside of the pipe. A heat-resistant optical fiber unit characterized by comprising layers. (2) The plurality of optical fibers are a covered assembly with a roughly circular cross section, in which a buffer protection layer made of silicone rubber or fluorine rubber is integrally applied to the optical fibers assembled together. A heat-resistant optical fiber unit according to claim 1, characterized in that: (3) The heat-resistant pipe is made of paper tape, manila hemp tape, or aromatic polyamide fiber nonwoven fabric, and a thermosetting plastic made by coating or impregnating the tape or nonwoven fabric, and the thermosetting plastic is heat-cured. A heat-resistant optical fiber unit according to claim 1 or 2, characterized in that: ()0 When the outer diameter of the coated aggregate is d and the inner diameter of the heat-resistant pipe is D, a gap is formed between the coated aggregate and the heat-resistant pipe with D≧1.0116. A heat-resistant optical fiber unit according to any one of claims 1 to 3, characterized in that: