JPH06309943A - Optical fiber cable - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent hydrogen gas from being generated due to corrosion when the hollow iron wire into which the optical fiber of the optical fiber-containing cable is inserted through the cracks, etc., and increase in transmission loss of the optical fiber. To do. [Structure] Optical fiber 2 of optical fiber cable 10
8 is inserted in the hollow iron wire 18A
0 is connected and a pressurizing medium is enclosed in the hollow iron wire 18A. When water is about to be generated in the hollow iron wire 18A through a crack or the like, the pressurized medium in the hollow iron wire 18A is jetted through the crack to reliably prevent the water from entering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber-containing cable in which an optical fiber for a detection line or the like is provided in a cable body such as a submarine power cable or a submarine water pipe.

[0002]

2. Description of the Related Art Submarine cables in a broad sense, such as submarine power cables or submarine water pipes, transmit optical signals in order to control equipment connected to the submarine cables and to transmit temperature, pressure and other information. It houses an optical fiber for transmission (for example, see Japanese Patent Application No. 1-39898). This type of optical fiber is used for hollow iron wires that are part of the iron wire armor that protects the cable body, hollow iron wires that are installed inside the iron wire armor, and hollow iron wires that are part of the tension member. Has been inserted.

[0003]

When this type of submarine cable is long, the hollow iron wire is jointed in the factory, but the joint portion of the hollow iron wire, which was overlooked in the inspection in the factory, is a minor one. If the crack expands due to stress after the submarine cable is laid, or if a hole is formed in the hollow iron wire due to external damage or the like, seawater may enter the inside of the hollow iron wire. When the hollow iron wire is flooded in this way, hydrogen gas is generated due to the corrosive action on the inner surface of the hollow iron wire, and the hydrogen gas increases the transmission loss of the optical fiber in the hollow iron wire.

[0004] In order to repair the submarine cable in order to eliminate such inundation, a repair ship is required.
A large repair cost is required, and it is difficult to detect a crack occurrence point of the hollow iron wire or a minor crack.

It is an object of the present invention to provide an optical fiber-containing cable which avoids the above-mentioned drawbacks and can surely prevent the occurrence of water immersion in the hollow iron wire into which the optical fiber is inserted.

[0006]

In order to solve the above problems, the present invention provides an optical fiber in which an optical fiber is inserted into a hollow iron wire provided along a cable body such as a power cable or a water pipe. It is an object of the present invention to provide an optical fiber-containing cable, which is characterized in that it is provided with a pressurized medium supply source that is connected to the hollow iron wire and that encapsulates the pressurized medium in the hollow iron wire.

[0007]

When the pressurized medium supply source is connected to the hollow iron wire and the pressurized medium is enclosed in the hollow iron wire as described above, cracks in the hollow iron wire expand and attempt to be flooded. The pressurized medium in the hollow iron wire is surely prevented by being ejected through this crack. It should be noted that when the pressurized medium is ejected from the hollow iron wire, the indication of the pressure gauge of the pressurized medium supply source is lowered, so that it is confirmed that the hollow iron wire is cracked to cause water infiltration.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2 which show an optical fiber cable 10 according to the present invention.
Although it is shown that it is an iron wire armored electric power cable laid on the seabed 12, this optical fiber-containing cable is a long body such as a submarine water pipe in addition to the power cable, and is an optical fiber for control or transmission inside. It is used in the broad sense that the fiber is housed.

This optical fiber cable 10 is shown in FIG.
As shown in FIG.
And an iron wire armor 20 including a plurality of iron wires 18 twisted on the cable body 14 via a seat 16, and the cable body 14 includes a conductor 22 and an insulation provided on the conductor 22. The object 24 and the lead cover 26 provided on the insulator 24.

In the embodiment shown in FIG. 2A, the optical fiber 28 is inserted in the hollow iron wire 18A among the plurality of iron wires 18 constituting this iron wire armor. Note that, as shown in the figure, instead of one hollow iron wire, a plurality of hollow iron wires 18A may be provided at intervals in the circumferential direction, and the optical fiber 28 may be inserted into each hollow iron wire 18A. Also, FIG.
In the example of (B), the optical fiber 28 is made of the iron wire armor 20.
It is inserted in a dedicated hollow iron wire 19 provided alongside the inside of the. In the following description, the case where the optical fiber 28 is inserted into the hollow iron wire 18A which is a part of the iron wire armor of FIG. 2A is described, but the same is true when the optical fiber 28 is inserted into the dedicated hollow iron wire 19. The present invention is applied.

This optical fiber cable 10 is shown in FIG.
As shown in FIG. 3, the hollow iron wire 18A (or 19), which is held by the iron wire holding tool 30 at the end portion 10a rising from seawater and in which the optical fiber 28 is inserted, is the branch piece 3
It is pulled into 2. As shown in FIG. 3, the branch piece 32 includes a T-shaped tube 34 into which the open end 18a of the hollow iron wire 18A is inserted and communicates with the hollow end of the hollow iron wire 18A through the open end 18a, and the T-shaped tube 34. A protective sleeve 36, which is disposed inside and through which the optical fiber 28 extending from the open end portion 18a of the hollow iron wire 18A penetrates, and a T-shaped tube 34
And a nipple 38 attached to the branch pipe portion 34A.

A packing 40 and a sealing member 42 are disposed between the inside of the T-shaped tube 34 and the hollow iron wire 18A, and the packing 40 and the sealing member 42 are T-shaped.
It is fastened by a cap nut 44 screwed to one end of the character tube 34. Similarly, a packing 40 ′ and a sealing member 42 ′ are disposed between the inside of the T-shaped tube 34 and the protective sleeve 36, and these packing 40 ′ and sealing member 42 ′ are attached to the other end of the T-shaped tube 34. It is tightened by the screwed cap nut 44 '. The nipple 38 is tightened by a cap nut 46 screwed to the end of the branch pipe portion 34A of the T-shaped pipe 34.

The optical fiber 28 extending through the protective sleeve 36 and out of the T-tube 34 is connected to an optical fiber termination box 48, and the nipple 38 is a pressurized medium such as air, inert gas or insulating oil. Is connected to a pressurized medium supply source 50. In the illustrated embodiment, the pressurized medium source 5
0 is the oil layer 54 and the air layer 5 in which the air cell 52 is embedded.
6 and a pressure compensation tank 58 having an air cell 5
2 is connected to the nipple 38 via a conduit 62 with a valve 60. The conduit 62 has a valve 64 which pressurizes and supplies an auxiliary pressurizing medium before the valve 60, and the pressure compensating tank 58.
When the pressure is reduced, the valve 64 is opened to continuously supply the auxiliary pressurizing medium (air). In FIG. 1, reference numeral 66 is a pressure gauge for monitoring the pressure of the air layer 56,
Further, reference numeral 68 is a liquid level gauge for monitoring the liquid level of the oil layer 54.

Next, the optical fiber-containing cable 1 of the present invention
As shown in FIG. 1, the optical fiber-containing cable 10 is laid on the seabed 12 as shown in FIG.
0a is retained by an iron wire retainer 30 as shown in the drawing, and the cable body 14 at this end 10a is connected to a device (not shown) on the ground side, and an optical fiber 28 is inserted into the hollow iron wire 18A. Are drawn into the branch piece 32.

In this branch piece 32, as shown in FIG. 3, an end of the hollow iron wire 18A is opened, and an optical fiber 28 penetrating through a protective sleeve 36 is led out. This optical fiber 28 is an optical fiber. It is introduced into the termination box 48.
The branch pipe portion 34 </ b> A of the branch piece 32 has the pressurized medium supply source 5
Connected to 0. As shown in FIG. 2, when the optical fiber cable 10 has a plurality of hollow iron wires 18A, a plurality of branch pieces 32 corresponding to each hollow iron wire 18A.
The branch pipe portion 34A is connected to one pressurized medium supply source 50 via a common header (not shown).

Accordingly, from the pressurized medium source 50 to the conduit 6
2. The pressurized medium such as air supplied to the T-shaped tube 34 of the branch piece 32 through the branch tube portion 34A of the branch piece 32 is
This pressurized medium is filled in the hollow iron wire 18A of the iron wire armor 20 that is supplied to the hollow iron wire 18A that opens inside the T-shaped tube 34 and that surrounds the optical fiber cable 10. The pressure of the pressurizing medium is set to be higher than the pressure in water in which the optical fiber cable 10 is laid.

Pressure compensation tank 58 of pressurized medium supply 50
Is pressure-compensated by the air cell 52 and the air layer 56, so that the hollow iron wire 18 in the optical fiber cable 10 is
Even if the pressure of the pressurized medium in A changes due to a temperature change or the like, this pressure change is surely absorbed by the pressure compensation tank 58.

When a crack occurs at the point Lk in FIG. 1 of the hollow iron wire 18A of the optical fiber cable 10, the hollow iron wire 18A is filled with the pressurizing medium set to a pressure higher than the surrounding water pressure. Since water is ejected through the cracks, water does not enter the hollow iron wire 18A through the cracks.

When the pressurizing medium in the hollow iron wire 18A is jetted, the filling pressure of the pressurizing medium tends to decrease, but the valve 64 opens upon detection of this by a pressure switch (not shown). The pressurized medium is continuously replenished into the hollow iron wire 18A, so that the hollow iron wire 18A is continuously prevented from being flooded.

In addition to the occurrence of cracks, the water leaks into the hollow iron wire 18A when holes are formed due to external damage to the hollow iron wire 18A, but this is also prevented by jetting and replenishing the pressurized medium. It Since the pressure in the air cell 52 decreases, the indication value of the liquid level gauge 68 also decreases, and the pressure of the air layer 56 also decreases and the indication value of the pressure gauge 64 decreases, so that the hollow iron wire 18A fails. Is detected.

The pressure medium supply source 50 is preferably connected to the hollow iron wire 18A at both ends of the optical fiber-containing cable 10, but the cable 10 is relatively short, and only one of the pressure medium supply sources 50 has a predetermined length. If the pressurized medium of pressure can be filled, the pressurized medium supply source 50 may be connected to only one end of the hollow iron wire 18A and the other end may be closed. Also,
As described above, as the pressurizing medium, oil, an inert gas such as N ₂ can be used, but considering the economical efficiency,
Air is the most preferred.

[0022]

According to the present invention, as described above, the pressurizing medium supply source is connected to the hollow iron wire in which the optical fiber of the optical fiber-containing cable is inserted, and the pressurizing medium is enclosed in the hollow iron wire. Therefore, when a hole is created due to expansion of cracks and the like in the hollow iron wire, external damage, etc., and water is about to be generated, the pressurized medium inside the hollow iron wire can be sprayed through these cracks, holes, etc. to prevent water from entering the area reliably. There is a real benefit.

[Brief description of drawings]

FIG. 1 is a system diagram of a cable with an optical fiber according to the present invention.

2 is a schematic cross-sectional view of an example in which an optical fiber is inserted into a part of an iron wire armor, and FIG. 2B shows an inside of the iron wire armor. It is a partially expanded sectional view of another example in which the optical fiber is inserted into the hollow iron wire provided along with.

FIG. 3 is an enlarged sectional view of a branch piece used in the present invention.

[Explanation of symbols]

 10 Cable with Optical Fiber 10a End 12 Seabed 14 Cable Body 16 Seating 18 Iron Wire 18A Hollow Iron Wire 18a Open End 19 Hollow Iron Wire 20 Iron Wire Armor 22 Conductor 24 Insulator 26 Lead Cover 28 Optical Fiber 30 Iron Wire Detainer 32 Branch Piece 34 T-shaped tube 34A Branch pipe part 36 Protective sleeve 38 Nipple 40 Packing 40 'Packing 42 Sealing member 42' Sealing member 44 Cap nut 44 'Cap nut 46 Cap nut 48 Fiber optic termination box 50 Pressurizing medium supply source 52 Air Cell 54 Oil layer 56 Air layer 58 Pressure compensation tank 60 Valve 62 Conduit 64 Valve 66 Pressure gauge 68 Liquid level gauge

Claims (1)

[Claims] 1. An optical fiber-containing cable in which an optical fiber is inserted into a hollow iron wire provided along a cable main body such as an electric power cable or a water pipe, and the cable is connected to the hollow iron wire and added to the hollow iron wire. An optical fiber cable, comprising a pressurized medium supply source for enclosing a pressurized medium.