JPS6138913A - Armored submarine optical cable - Google Patents

Abstract

PURPOSE:To improve the reliability of the titled cable by forming a hard steel wire with the twisting pitch of 21-40 times as long as twice the distance from the center of the cable and an armored iron wire with the twisting pitch of 12- 16 times as long as twice the distance from the center of the cable. CONSTITUTION:The hard steel wire 3 to be a tensile strength body is formed with the twisting pitch of 21-40 times as long as twice the distance from the center of the cable and the armored iron wire 7 is formed with the twisting pitch 12-16 times as long as twice the distance from the center of the cable. When the value of P0/D0 is limited within the range of 12<=(P0/D0)<=16, the ratio of partial charge of tension to the tensile strength body 3 of the submarine optical cable is about 20% the whole load. When the value of P1/D1 is set up within the range of 21-40, the P0/D0 value of the armored iron wire 7 can be suppressed to 0.5% expansion or less against 12-16 times the using load and cable winding and production can be attained easily, so that the reliability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an armored submarine optical cable that is armored with iron wire.

[Background technology and its problems]

As shown in Fig. 1, a submarine optical cable is constructed by providing a metallic pressure-resistant layer 2 to protect an optical fiber unit 1, laminating a tensile strength member 3 made of a plurality of twisted hard steel wires such as piano wire, and further Covered with metal tube 4 and covered with polyethylene (
PE) An insulating layer is formed by the outer cover 5.

Such submarine optical cables are usually used for deep sea applications, but when installed on the coast or in shallow seas, they are prone to damage from rocks and ship anchors.

In addition, to protect against cutting by trawls etc.
Exterior iron wires 7 are twisted together via an internal seat 6 to form an exterior submarine optical cable.

By the way, submarine optical cables are generally required to have a structure that can withstand the tensile forces that are applied during cable installation and salvage, and that does not deteriorate the transmission loss of the optical fiber due to elongation strain. In the case of the above-mentioned armored submarine optical cable, a problem arises as to how to determine the ratio of the tensile force borne by the internally provided tensile strength member 3 and the armored iron wire 7.

Regarding this point, Japanese Patent Publication No. 56-6801 has already disclosed an armored submarine cable that optimizes the sharing ratio of the pulling force, but this invention has the following problems.

(2) The above invention is an embodiment of an armored submarine optical cable using a coaxial cable as a communication path, and cannot be directly applied to an armored submarine optical cable using an optical fiber as a communication path. This is because an armored submarine optical cable has a circular pressure-resistant layer 2 and an optical fiber unit 1 inside the internal tensile strength member 3, and unlike a coaxial cable, there is no insulating layer or external conductor, and the jacket outer diameter is around 20 mmφ. It has a thin structure. Due to these differences, the rigidity of the cable core increases, and if the twisting pitch of the armored wire becomes P/D of 20 or more, the cable will be stretched during coiling when the coil diameter is 5 to 2.0 m, which is normally wound. The cable cannot be wound smoothly and sometimes the cable may lift up and cause damage.

■ In the above invention, the design tension of the cable reaches its maximum value when the twist pitch of the armored wire is a certain value, but considering the cable structure, in the armored submarine optical cable, the internal tensile strength member 3
In the case of an armored submarine optical cable, it is necessary to limit the pitch of the internal tensile strength wires, since the characteristics of the entire armored submarine cable can only be obtained by specifying the twist pitch of the wires.

[Purpose of the invention]

This invention was made in view of the actual situation,
The purpose of the present invention is to provide an armored submarine optical cable in which the design stresses of the armored iron wire and internal tensile strength members are determined to optimize the handling and manufacturing of the armored submarine optical cable.

〔Example〕

Hereinafter, a second embodiment of the armored submarine optical cable of the present invention will be described.
This will be explained with a diagram.

In this figure, as in Fig. 1, 1 is an optical fiber unit, 2 is a pressure-resistant layer with an outer diameter of 7 mmφ, and 3 is a plurality of hard steel wires (outer Diameter 1
．． 698mmφ), 4 is a metal tube, 5 is a PE jacket (outer diameter 22mmφ), 6 is an internal seat, 7
8 is an exterior iron wire with an outer diameter of 6 mmφ twisted at a predetermined P/D as described later, and 8 is an outer covering.

In this invention, first, the twist pitch P0 of the armored iron wire 7,
The ratio Po/Do of the distance Do from the center of the cable to the center of the armored iron wire 7 was set as shown below.

The PoZDo value indicates that the cable will not be washed away by ocean currents,
Considering that it is difficult to be cut by a ship's anchor or trawl net, etc., but considering that the coil can be removed in a wire storage tank of at least 5 mφ in handling, the rule of thumb is P. /D
It is considered appropriate that o is at most 16 or less. On the other hand, P
It is appropriate that the minimum o/D o value is 12 or more in view of the elongation characteristics and rotation characteristics of the cable.

Here, we will consider the elongation of optical fiber, which is the most important characteristic of armored submarine optical cables.

Considering that the elongation when an armored submarine optical cable is pulled is almost the same as the elongation of the inner optical fiber, the elongation of the optical fiber under a certain tension is the difference between the outer steel wire 7 and the tensile strength member 3 of the inner submarine optical fiber. It is determined by the tension sharing between.

This tension sharing has a correlation between the P0/Do value of the armored iron wire 7 and the Pi/Di value of the tensile strength member 3 of the submarine optical cable. . /D.

This value has a large effect, especially when using this value as mentioned above,
If it is limited to a narrow range of 12≦Po/Do≦16, the tension sharing ratio of the tensile strength member 3 of the submarine optical cable can be at most about 20% of the total load, as shown by the experimental values in Fig. 3. Are known.

On the other hand, the underwater weight of the armored submarine optical cable is approximately 3 to 4 tan/Km as shown in the figure, and considering that the applicable water depth of the armored submarine optical cable is 1000 m or less,
Laying an armored submarine optical cable.

The working load applied during repair is approximately 15 tons.
It is estimated that the following.

However, α is the margin for the fluctuating load (3 tons). Figure 4 is a graph of the tension and cable elongation measured by changing the Pi/Di value of the tensile strength member 3 for the submarine optical cable without sheathing. (The breaking load of this cable is about 9 to 10 tons).

From this figure, taking into account that the design requirement for normal submarine optical cables is to suppress the elongation of the optical fiber to 0.5% or less, curve A, which shows the case where the P i / D + value is 21, has approximately 3 tons is optical fiber 0.5%
This corresponds to elongation, and if the Pi/Di value is 27, approximately 3.8 tons from curve B will produce an elongation of 0.5%. Similarly, if the Pi/Di value is set to 37, 5 from curve C.
Even if ton is the same Pi/Di value, if the tensile strength line is a two-layer structure described later, it can be seen from the curve that the tension increases somewhat.

Therefore, if the exterior iron wire 7 is applied as described above, the maximum
In order for the tensile strength member 3 to bear 20% of the working load of 5 tons, that is, a tension of 3 tons, P i / D
It is required that i be at least 21 or more.

Furthermore, considering that the tensile strength member 3 is wound onto a drum (diameter 1 m) during production, it is appropriate to set the upper limit of the P i /D + value to 40 or less in order to prevent laughter.

Therefore, from the above explanation, the Pi/Di value is 21 to 40.
When set to the range of , the Po/Do value of the exterior iron wire 7 is 12.
An armored submarine optical cable that can hold the elongation to 0.5% or less for the working load in the case of ~16, and also solves problems in cable handling (winding into a storage tank) and manufacturing. be able to.

FIG. 5 shows another embodiment of the armored submarine optical cable of the present invention, in which the same parts as in FIG. 2 are given the same reference numerals. 3A and 3B are tensile strength bodies with a two-layer structure,
The Pi/Di value is in the range of 27-40.

〔Effect of the invention〕

As described above, the present invention sets the P/D of the armored iron wire and the tensile strength member of the armored submarine optical cable so that problems do not arise in terms of actual handling and manufacturing, and that the optical fiber is resistant to tensile force. Since it is set within a range that can be sufficiently protected, it has the effect that a highly reliable armored submarine optical cable can be constructed.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the structure of a submarine optical cable, Fig. 2 is a cross-sectional view of the armored submarine optical cable of the present invention with a predetermined P/D value, and Fig. 3 is the tension when the armored submarine optical cable is pulled. Figure 4 is a measurement graph showing the relationship between tension and elongation using the Pi/Di value as a parameter for an unarmored submarine optical cable, and Figure 5 is a graph of the armored submarine optical cable with a two-layer tensile strength structure. FIG. In the figure, 1 is an optical fiber unit, 2 is a pressure layer, 3 is a tensile strength member, 4 is a metal tube, 5 is a PE jacket, 6 is an internal seat, and 7 is an exterior iron wire. Figure 1 Figure 2 Figure 3 - Total tension (ton) - Tension (ton)

Claims (2)

[Claims] (1) An armored submarine optical cable in which a tensile strength body is formed by twisting hard steel wires around the outer periphery of a pressure-resistant layer that protects an optical fiber unit, which is then covered with a metal tube and a polyethylene jacket, and is then armored with armored iron wire. , the hard steel wire is 21 to 2 times the distance from the center of the cable.
An armored submarine optical cable characterized in that the twisting pitch is 40 times, and the twisting pitch of the armored iron wire is 12 to 16 times twice the distance from the center of the cable. (2) The armored submarine optical cable according to claim (1), wherein the tensile strength member is formed of two-layer twisted hard steel wire.