JPH03145014A - Optical fiber complex aerial earth wire - Google Patents

Abstract

PURPOSE:To prevent an optical fiber from the influence of a short-circuit current, by applying a carbon membrane with a specific scope of axial resistance value to the optical fiber as the primary coverage. CONSTITUTION:A single mode optical fiber 6 is covered with a carbon membrane 7 having the axial resistance less than 5-40KOMEGA/cm as the primary coverage, and a heat curing silicone resin 8 is used as the secondary coverage. Such an element wires 9 are collected around a a linear FRP 10 in a spiral form, and pressure-winding it with a polyimide tape 11 to form an optical fiber unit 1. The optical fiber units 1 are housed in an aluminum spacer 2 furnishing grooves 3, an aluminum tape is welded and sunk to form an aluminum pipe, and 12 aluminum-covered steel wires 5 are collected around the aluminum pipe in a spiral form. Consequently, an increase of transmission loss caused by hydrogen and a breakdown by the extension strain can be reduced, and no coverage breakdown owing to a short-circuit current is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical fiber composite overhead ground wire, which is an overhead ground wire containing an optical fiber therein.

(Prior Art) Optical fibers are housed in an overhead ground wire to construct an optical communication system using the optical fibers.

For example, the optical fiber composite overhead ground wire described in Japanese Utility Model Application Publication No. 60-156617 uses a spacer having a spiral groove on the outer periphery and a metal coating covering the outer periphery of the metal spacer to provide an optical fiber accommodating portion. An optical fiber composite overhead ground wire is described, which is constructed by accommodating an optical fiber in the groove and arranging the optical fiber at the center of a stranded conductor.

The optical fibers housed in such optical fiber composite overhead ground wires are constantly exposed to 0.2% elongation strain during the overhead line, and elongation strain is further added due to temperature fluctuations, wind, etc. The optical fibers in the optical fiber composite overhead ground wire are subjected to severe conditions. These elongational strains reduce the strength of the optical fiber and may even break the optical fiber, limiting the life of the optical fiber composite overhead ground wire.

Furthermore, in an optical fiber composite overhead ground wire in which an optical fiber is housed in a metal tube, hydrogen is generated due to the reaction between the metal and moisture in the atmosphere, causing an increase in transmission loss. International Wire &
Cable Symposium Process
edings 1987, pp. 241-244, describes applying a hermetic coating to an optical fiber, but from the standpoint of strength and chemical protection, applying a carbon thin film as the coating material is considered. .

However, since the carbon thin film is electrically conductive, if a large current flows through the metal conductor part of the optical fiber composite overhead ground wire due to a short circuit accident, the current flowing between the metal conductors will be transferred to the carbon thin film, which is the primary coating of the optical fiber. There was a problem in that the optical fiber's coating was destroyed as a result.

(Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned circumstances, and provides an optical fiber composite overhead ground wire using an optical fiber coated with a carbon thin film that is not affected by short circuit current. The purpose is to

(Means for Solving the Problems) The present invention provides an optical fiber composite overhead ground wire in which an optical fiber accommodating portion that accommodates an optical fiber is provided in the center of a twisted conductor wire, in which the optical fiber has an axial resistance value The optical fiber is characterized in that it is primarily coated with a carbon thin film having a resistance of 5 to 40 Ω/cm or less.

(Function) FIG. 2 is a sectional view of an optical fiber composite overhead ground wire used in an experiment to explain the present invention in detail.

In the figure, 21 is an optical fiber, 22 is an aluminum spacer, 23
24 is a groove, 24 is a metal coating, and 25 is an aluminum coated steel wire.

The shunt current was measured using the apparatus shown in FIG. 3
1 is a power supply, 32 is the optical fiber composite overhead ground wire shown in FIG. 2, 33 is an optical fiber whose secondary coating at the current measurement part is removed to expose a thin carbon film, and 34 is an ammeter.

The measurement of the shunt current is performed by connecting a power source 31 to an aluminum-coated steel wire 25 of an optical fiber composite overhead ground wire in which optical fibers coated with carbon thin films having different axial resistance values are housed in grooves 23 of an aluminum spacer 22. A current was applied and the current flowing through the carbon coating of the optical fiber was measured with an ammeter 34. Q
FIG. 4 shows the results of measuring the shunt current to the carbon thin film when a current of [KA] was passed through the optical fiber composite overhead ground wire. From FIG. 4, it can be seen that no shunt current occurs when the axial electrical resistance of the carbon thin film is less than 5 KΩ/cml. After the experiment, the optical fiber composite overhead ground wire was disassembled and the appearance of the optical fiber was investigated.The optical fiber composite overhead ground wire was coated with a carbon thin film with an axial electrical resistance of 5 [KΩ/cm] or less. If you store it in
When a current flows through the metal conductor of the optical fiber composite overhead ground wire,
It has become clear that the shunt current causes damage to the coating.

Further, when a tensile test of optical fibers similar to those described above was conducted, a decrease in strength was observed in optical fibers having an axial electrical resistance of 40 [KΩ/cm] or more. From this, it can be seen that the primary coating of an optical fiber should have an axial resistance value of 5.
It was found that it is desirable that the resistance is 40 Ω/cm or more and 40 Ω/cm or less.

(Embodiment) FIG. 1(A) shows a cross section of an optical fiber composite overhead ground wire for explaining an embodiment of the present invention. In the figure,
1 is an optical fiber unit, 2 is an aluminum spacer, 3 is a groove, 4 is a metal coating, and 5 is an aluminum coated steel wire.

FIG. 1(C) shows a cross section of the optical fiber.

Core diameter 9μm, refractive index difference 0.3% Cladding diameter 125μm
A carbon thin film 7 is attached to the single mode optical fiber 6 of
The electrical resistance in the axial direction is approximately 10 [KΩ].
/cm], a thermosetting silicone resin 8 was applied as a secondary coating, and the outer diameter was 0.4 μm.

FIG. 1(B) shows the above-mentioned strands 9 gathered in a spiral around a linear FRPIO with an outer diameter of 0°4 μm and a thickness of 2.5 μm.
This is an optical fiber unit that is tightly wound with a polyimide tape 11 having a width of 6 μm.

As shown in FIG. 1(A), the groove diameter is l.

It was housed in an aluminum spacer 2 having three 38 mm grooves and a maximum outer diameter of 3.8 mm, and aluminum tape was welded and sinked thereto to provide an aluminum vibe with an outer diameter of 5.05 mm. Twelve aluminum-coated steel wires 5 having an outer diameter of 1.75 mm were collected in a spiral shape.

The optical fiber composite overhead ground wire according to this example was heated at 200°C.
An accelerated test was conducted to evaluate the increase in loss due to hydrogen, but no increase in loss was measured. The result of measuring the n value, which is the fatigue index of the wire, is n=2
00, which is about 10 times the value of an optical fiber without carbon coating. This revealed that the carbon-coated optical fiber has a sufficient rupture life even when exposed to elongation strain.

(Effects of the Invention) As is clear from the above description, according to the present invention, increases in transmission loss due to hydrogen and breakage due to elongation strain can be significantly reduced, and optical fibers that do not cause coating breakdown due to short circuit current can be This has the effect of providing a fiber composite overhead ground wire.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical fiber composite overhead ground wire and a bare wire for explaining one embodiment of the present invention, and FIGS. 2 to 4 are for explaining the present invention in detail. , Figure 2 is a cross-sectional view of the optical fiber composite overhead ground wire used in the measurement, and Figure 3 is a cross-sectional view of the optical fiber composite overhead ground wire used in the measurement.
The figure is a schematic diagram of the measuring device, and FIG. 4 is a graph of the measurement results. DESCRIPTION OF SYMBOLS 1... Optical fiber unit, 2... Aluminum spacer, 3... Groove, 4... Metal coating, 5... Aluminum coated steel wire.

Claims (1)

[Claims] In an optical fiber composite overhead ground wire in which an optical fiber housing part containing an optical fiber is provided in the center of a twisted conductor wire, the optical fiber is primarily coated with a carbon thin film having an axial resistance value of 5 to 40 KΩ/cm. An optical fiber composite overhead ground wire characterized by being an optical fiber.