JPH04255614A - Power photo-composite submarine cable - Google Patents

Abstract

PURPOSE:To improve respective characteristics such as side-pressure-resistant characteristic, bending characteristic, or twisting characteristic by providing, on the side face of PE sheath, a spiral groove whose twisting direction is the same as that of an iron wire armor and in which the relationship between a pitch and a pitch diameter is specified. CONSTITUTION:A spiral groove 23 is provided in the plastic sheath 22 of a power cable 12 in such a way that an optical fiber unit 24 is housed therein. The unit 24 is not fixed by a presser winding 25 so that it moves inside the groove so as to can cel a tensile and a compressive stresses arising in and outside of a neutral plane upon bending. The swirl direction of the groove 23 is designed to be the same as the twist direction of an iron wire armor 34, and the relational equation such as n/m=D/d is designed to be satisfied when the ratio between a twist pitch 'P' and the pitch diameter 'D' of the armor 34 is designated to be 'n' and the ratio between a spiral pitch 'p' and a pitch diameter 'd' of the groove 23 is designated to be 'm'. When a composite cable 10 is twisted, the length of the groove 23 is substantially kept constant, thus no stress is applied to the unit 24 so that a lowering of life and a degradation of transmission loss can be prevented.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a composite submarine cable consisting of a power cable and an optical fiber unit.
In particular, the present invention relates to a power-optical composite submarine cable having a structure in which a layer of spirally wound optical fiber units is provided on the outside of the power cable, and a single layer of iron wire sheathing is further provided on the outside of the power cable.

0002

2. Description of the Related Art FIG. 2 shows an example of a cross section of a conventional composite cable. 10 is the entire composite cable. 12 is a power cable, 14 is its oil passage, 16 is a conductor, 18 is an insulating layer, 20 is a lead sheath, and 22 is a PE sheath. A spirally wound layer of optical fiber units 24 is provided over the power cable 12 . The optical fiber unit may be one in which the optical fiber 26 is housed in a metal pipe 28 and covered with a plastic (PE) sheath 30 (hereinafter referred to as a pipe type), as shown enlarged on the right, or one in which the optical fiber 26 is housed in a metal pipe 28 and covered with a plastic (PE) sheath 30 (hereinafter referred to as a pipe type), or as shown on the left ,
Optical fiber 26 is wrapped around the tension member using UV resin 3.
2 and a plastic (nylon) sheath 3
A type with 0 applied (hereinafter referred to as a set type) is used. 34 is a steel wire exterior (galvanized iron wire, etc.). The layer of optical fiber unit 24 is provided directly below the layer of iron wire sheath 34 .

However, in the case of the above-mentioned single-layered iron wire armored cable, a phenomenon occurs in which it is relatively easy to twist (in the direction in which the iron wire sheath loosens) due to external force such as bending, and when twisted, the cable stretches. As schematically shown in FIG. 3, the composite cable 10 is rotated at an angle θ
If the state shown in (b) is obtained by twisting only
It is extended from L1 to L1. In addition, in FIG. 3, the right end surface of the composite cable 10 is also shown, and it shows that the point A which was right above the end surface in (a) moved as shown in (b) due to twisting. When the composite cable 10 is stretched in this way,
Stress is added to the optical fiber, resulting in a shortened service life and degraded transmission loss.

[0004] In order to solve this problem, the following technology has been proposed (Japanese Patent Application No. 198696/1999).
issue). As schematically shown in FIG. 4, (1) the twisting direction of the optical fiber unit 24 and the twisting direction of the iron wire sheathing 34 are the same, and (2) the twist pitch P and the layer core diameter D of the iron wire sheathing 34 are the same. ratio P
/D is n, and the twist pitch p of the optical fiber unit 24 is
When the ratio p'/d' of ' and layer core diameter d' is m', n/
This means that m'=D/d'. In this way, as described above, even if the cable is stretched due to twisting, the length of the optical fiber unit does not change, and therefore no stress is applied to the optical fiber.

[0005]

[Problem to be Solved by the Invention] However, as described above, when a cable is designed so that n/m'=D/d', the twist pitch p' of the optical unit often becomes large. . Therefore, when the cable is bent,
The stress applied to the light unit increases. In particular, when the cable is arranged spirally on the outside of the power cable as described above, the core diameter d' of the layer becomes large, so when the cable is bent, the optical unit receives a large tensile stress outside the neutral plane. The inside of the vertical plane will be subjected to a large compressive force, which may have a fatal effect on the transmission characteristics of the optical fiber.

[0006]

[Means for Solving the Problems] As shown in FIG. 1, (1) a spiral groove 2 is formed in a plastic sheath 22 of a power cable;
(2) the direction of rotation of the spiral groove 24 is the same as the twisting direction of the iron wire sheath 34; (3) the iron wire sheath 34
The ratio of the twist pitch P to the layer core diameter D is n, and the groove 23
When the ratio of the helical pitch p and the layer core diameter d is m,
A measure is taken to ensure that n/m=D/d.

That is, as shown in FIG.
A large number of grooves 23 are spirally provided on the side surface of the optical fiber unit 23, and an optical fiber unit 24 is accommodated in each groove. The length of the optical fiber unit 24 and the length of the groove 23 are approximately equal. 25 is a presser winder. The relationship between the groove 23 and the iron wire sheath 34 is as described above. Note that this relationship is the same as the relationship between the optical fiber unit 24 and the iron wire sheath 34 in the conventional example (FIG. 2). Note that the layer core diameter d of the groove 23
is the diameter of a circle passing approximately through the center of the groove 23.

[0008]

[Function] (1) By housing the optical fiber unit 24 in the groove 23, the lateral pressure of the iron wire sheath 34 is not applied to the optical fiber unit 24. (2) Furthermore, by arranging the optical fiber unit 24 in the groove 23, it is no longer directly pressed by the presser winding 25, so that when the optical fiber unit 24 is bent, the optical fiber unit 24
4 can be easily moved within the groove 23, so that the tensile and compressive stresses applied to the optical fiber unit 24 outside and inside the neutral plane cancel each other out. (3) The turning direction of the groove 23 and the twisting direction of the iron wire sheath 34 are the same, and the twist pitch P and layer core diameter D of the iron wire sheath 34,
In addition, by setting the relationship between the helical pitch p of the groove 23 and the layer core diameter d as n/m=D/d (however, p/d=m, P/D=n), it is possible to Therefore, there is almost no change in the length of the groove 23. Therefore, the length of the optical fiber unit 24 housed in the optical fiber unit 3 also hardly changes.

[0009]

[Example] As the optical fiber unit 24, a pipe type (on the right side of Fig. 2) and an aggregate type (on the left side of Fig. 2) were used.
A product of the present invention having the structure shown in FIG. 2 and a conventional product having the structure shown in FIG. In addition, - Layer core diameter D of iron wire sheathing 34 = 1600 mm - Iron wire sheathing 3
4, twist pitch P = 120 mm, layer core diameter d of groove 23 = 1
00 mm - Helical pitch p of the groove 23 = 1110 mm - Core diameter d' of the optical fiber unit 24 = 100 mm - Twisting pitch p' of the optical fiber unit 24 = 1110 mm.

0010

[Table 1] From this table, it can be seen that the bending properties of the products of the present invention are significantly improved.

[0011]

Effects of the Invention (1) By housing the optical fiber unit in the groove, the lateral pressure of the iron wire exterior is not applied to the optical fiber unit. Therefore, there is no need for an optical fiber unit with particularly excellent lateral pressure resistance. (2) Furthermore, by arranging the optical fiber unit in the groove, it is no longer directly pressed down by the presser and winding, and when it is bent, the optical fiber unit can easily move within the groove. The tensile stress and compressive stress applied to the optical fiber unit on the outside and inside of the plane cancel each other out. Therefore, bending properties are improved. (3) The turning direction of the groove and the twisting direction of the iron wire sheath are the same, and the relationship between the twist pitch P and layer core diameter D of the iron wire sheath, and the relationship between the helical pitch p of the groove and the layer core diameter d is n/ m
=D/d (where p/d=m, P/D=n), there is almost no change in the length of the groove before and after twisting. Therefore, the length of the optical fiber unit housed in the groove also hardly changes. Therefore, the composite cable has excellent twisting characteristics.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a cross section in an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a cross section in a conventional example.

FIG. 3 is an explanatory diagram showing that in the case of a single-layered iron wire armored cable, when the cable is twisted, the cable stretches due to the action of the iron wire.

FIG. 4 is an explanatory diagram of a conventional composite cable before and after twisting.

[Explanation of symbols]

10: Composite cable 12: Power cable 14: Oil passage
16: Cable conductor 18: Cable insulation layer 20:
Lead sheath 22: Plastic sheath 23: Spiral groove 24: Optical fiber unit 26: Optical fiber 28:
Metal pipe 30: Sheath 34: Iron wire exterior

Claims (1)

[Claims] 1. A power-optical composite submarine cable comprising a spirally wound layer of optical fiber units provided on the outside of the power cable and a single layer of iron wire sheathing provided on the outside thereof, wherein the optical fiber unit is connected to the power cable. It is accommodated in a spiral groove provided in the sheath and whose turning direction is the same as the twisting direction of the iron wire sheath; and the ratio of the twist pitch P of the iron wire sheath to the layer core diameter D is n; When the ratio of the helical pitch p of the groove to the layer core diameter d is m, n/
A power/optical composite submarine cable designed so that m=D/d