JP3065967B2 - Optical fiber composite underwater long body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber composite underwater elongate body such as a power cable, a water pipe, or the like laid on a water bottom that combines optical fibers.

[0002]

2. Description of the Related Art Conventionally, an optical fiber composite submarine power cable, for example, has a metal sheath of a power cable provided with a plastic sheath made of polyethylene or the like provided with a spiral or longitudinal groove on an outer periphery thereof, and is provided in the groove. An optical fiber unit containing an optical fiber is stored in a metal pipe, and an iron wire sheath is applied to the outside of the plastic sheath, or the optical fiber unit is spirally or SZ-twisted on the outer periphery of the metal sheath of the power cable. It has been configured such that a plastic sheath such as polyethylene is provided thereon, and a steel wire sheath is provided on the outside thereof. As still another example, an optical fiber is arranged in a gap between wires of an iron wire sheath applied on a plastic sheath.

[0003]

However, in the above-described optical fiber composite submarine power cable, the optical fiber unit buckles as the cable is bent. This buckling is fatal for an optical fiber,
So-called microbends reduce the transmission characteristics of the optical fiber. Further, the structure in which the optical fiber unit is disposed in the gap between the strands of the iron sheath has a problem that the optical fiber unit is crushed by the sheath iron wire.

[0004]

SUMMARY OF THE INVENTION The present invention provides an optical fiber composite underwater elongated body which solves the above-mentioned problems.
The first characteristic is that an optical fiber is housed in a metal pipe provided with a coating layer of a plastic material having a melting point higher than that of the plastic sheath material inside a plastic sheath provided on a long body such as a power cable and a water pipe. The optical fiber unit and the spacer are arranged in a tightly wound manner, and the outer surface thereof is provided with an iron wire sheath. The plastic sheath material is polyethylene, and the plastic material of the coating layer on the outer periphery of the optical fiber unit is polypropylene, polybutene, nylon. in the optical fiber composite underwater long body with <br/> in emissions.

A second feature of the present invention is that the elongated body is a power cable, and a plastic coating layer having a melting point higher than that of the plastic sheath material is provided on the outer periphery of a plastic sheath provided on the power cable. The optical fiber unit containing the optical fiber inside the metal pipe and the spacer are arranged closely and the outside is iron wire-coated,
The plastic coating layer around the optical fiber unit is semiconductive.

A third feature of the present invention is that, in the optical fiber composite underwater elongated body having the second feature, a metal tape layer is provided on the outside where the optical fiber unit and the spacer are closely arranged, and furthermore, It has an iron wire exterior.

A fourth feature of the present invention is that in the optical fiber composite underwater elongated body having any one of the first to third features, the outer diameter of the spacer is larger than the outer diameter of the optical fiber unit. .

Generally, an optical fiber has a low mechanical strength, and buckling is fatal. Local bending, so-called microbending, significantly reduces the transmission characteristics of the optical fiber. Therefore, the inventors of the present application have conducted various studies in order to find a structure that can be most easily combined with a power cable or a plastic water pipe and that does not impair the mechanical characteristics and transmission characteristics of the optical fiber.

Outer diameter of about 1.0mm with optical fiber inside
30 metal pipes of φ are spirally wound at a pitch of 80 × (7 to 12) times on the lead sheath of a power cable with an outer diameter of about 70 mmφ, and a polyethylene sheath is applied on it, and 70 mm in that state When the optical fiber and the metal sheath were examined by reciprocating bending 20 times with a radius of × 20 = 1400 mm, several to ten or more pieces were found to be damaged. From this, it was found that the main cause was that the buckling strength of the metal pipe was low, that is, the rigidity was low.

[0010] Therefore, a polyethylene coating layer is provided on the outer periphery to reinforce the metal pipe. If the thickness of the polyethylene coating layer is too large, the outer diameter of the cable becomes too large, and when a polyethylene sheath is provided on the arrangement layer of the optical fiber unit, the step of the optical fiber unit appears on the outside, which is not preferable. , 0.5 ~
1.0 mm, and the outer diameter of the optical fiber unit was selected to be 2 to 3 mmφ. Further, as shown in FIGS. 6 (a) to 6 (d), only the optical fiber unit (3) is wound, and the optical fiber unit (3) and the nylon string spacer (4) are wound together. A prototype with a polyethylene sheath was fabricated.

A bending test was performed on such a product, and after disassembly and examination, the following facts were found.

A part of the polyethylene coating layer of the optical fiber unit is not melted or deformed at the extrusion temperature of the polyethylene sheath (in general, polyethylene is extrusion-coated at a melting point of 120 to 130 ° C. at 200 ° C. or outside), and the polyethylene sheath layer is deformed. Yes,
It turns out that it is not an effective reinforcement.

FIGS. 6 (c) and 6 (d), which have relatively little effect as described above.
Was good, but still some optical fiber units
The buckling phenomenon was observed in (3), and it was found that reinforcement was insufficient and rigidity was insufficient to obtain a stable product during mass production.

FIG. 6 (a) and FIG.
(C) In the tightly wound state as in (d), it was found that the optical fiber unit (3) moved uniformly with respect to bending in the tightly wound state, and local buckling was less likely to occur.

No abnormality was observed in the nylon string spacer (4).

From these results, the coating layer on the metal pipe of the optical fiber unit has a higher melting point than polyethylene as the plastic sheath of the power cable,
It has been concluded that it is most preferable to use a plastic material having high rigidity. In FIGS. 6A to 6D, a nylon coating layer is used instead of the polyethylene coating layer on the metal pipe of the optical fiber unit (3). And conducted a similar experiment.

As a result, it was found that any of the structures shown in FIGS. 6A to 6D was satisfactory. Dare to see the difference between (a) to (d), that (c) and (d) are also excellent, and when the lateral pressure and crushing of the cable were performed, (c) and (d) Was also found to be excellent. Furthermore, to obtain a material other than nylon, polybutene, the same results as Nylon was conducted similar experiment with the polypropylene emissions.

Thereafter, an iron wire sheath was provided on the polyethylene sheath, and a bending test similar to that described above was performed. However, the above conclusion did not change.

On the basis of the above results, experiments were also conducted on a case where the optical fiber unit was wound on a polyethylene sheath of a power cable. In this case, FIG.
6 (c) and (d), in which a nylon string spacer was appropriately added to the optical fiber unit at the same time as the loose winding shown in FIG. Close winding is preferred if iron wire sheathing is applied on top of it, because the external force from the iron wire does not depend on it, and the optical fiber unit does not bend or move locally, so local abnormalities are less likely to occur and it is preferable. Was done.

In FIG. 6C, when the diameter of the optical fiber unit is 2 to 4 mm, the outer diameter of the nylon string spacer is 1 to 2 mm.
mm to 3-6 mm. Also, in the same figure (d), both the optical fiber unit and the nylon string spacer are 2-4.
mm and the same outer diameter. The winding pitch is lower diameter x (7
~ 12 times). On top of this, a rolled layer of polypropylene yarn, a single iron wire armor (iron wire outer diameter 8 mmφ), and a serving layer of polypropylene yarn were applied as seats, which are the same as existing submarine cable technology.

When such a cable was reciprocated 20 times with a radius of 20 times the outer diameter of the outer sheath of the iron wire, and the degree of damage to the optical fiber unit was investigated, all the structures were all sound. As expected, close winding was more stable as expected.

After that, when the optical fiber unit was subjected to lateral pressure and crushing, and the proof stress of the optical fiber unit was examined, the nylon fiber spacer was better in FIG. 6 (c) than in FIG. Since the pressure is shared between the optical fiber units, it has been found that the structure (c) is preferable in the case where the proof strength of the optical fiber unit is strong and the side pressure is large. On the other hand, when side pressure performance is not required, the optical fiber unit and nylon string spacer
It is easier to manufacture with the same diameter as in (d),
In addition, productivity can be improved because the number of windings can be reduced even a little.

Further, none of nylon, polybutene and polypropylene as the plastic coating layer of the optical fiber unit was affected by the paint applied on the outermost layer of the polypropylene yarn serving layer.

Further, in the cable having this structure, seawater or the like reaches the optical fiber unit through the iron wire sheath. The resistance to this is the highest performance of polyethylene in the past,
Has been shown to be no problem, it was confirmed that at least prolonged water immersion elongation due, in breaking force reduction test is good nylon, polybutene, and also a polypropylene emissions. However, polyethylene may be preferable to nylon in the vicinity of the surface of seawater due to the effects of ultraviolet rays, repeated wetting by seawater, and repeated dryness. In such a case, it is preferable that the nylon string spacer and the coating layer of the optical fiber unit are further coated with polyethylene of about 0.5 to 2.0 mm outside the nylon.

In both of the two structures described above, the winding method of the optical fiber unit and the nylon string is the same as the spiral winding or the SZ twist, but the essence of the winding is the same. Winding is preferred.

[0026]

1 is a cross-sectional view of one embodiment of an optical fiber composite submarine power cable according to the present invention.

In the drawing, (1) is a power cable core,
(2) is a metal sheath of a power cable such as a lead sheath, and (3) is an optical fiber unit tightly wound around the outer periphery of the metal sheath (2) together with a plastic spacer (4) such as a nylon string spacer. (5) is a holding tape, (6) is a plastic sheath made of polyethylene or the like, (7) is an iron wire sheath,
(8) is a serving layer such as a polypropylene yarn.

The optical fiber unit (3) has a polyethylene sheath on its outer periphery as shown in FIG.
The optical fiber (32) is housed in a metal pipe (31) such as a stainless steel pipe having a coating layer (33) such as a material having a higher melting point than (6), for example, nylon, polybutene, or polypropylene. .

FIG. 3 is a cross-sectional view of another embodiment of the optical fiber composite submarine power cable according to the present invention. In this specific example, a plastic sheath (6) such as polyethylene is provided on the metal sheath (2) of the power cable, and the optical fiber unit (3) shown in FIG. It is wound. On top of this, a holding tape (5), an iron wire sheath (7), a serving layer (8) and the like are provided.

FIG. 4 is a cross-sectional view of a specific example of the optical fiber composite submarine water pipe according to the present invention. As in the case of the power cable, an optical fiber unit (3) is tightly wound with a plastic spacer (4) such as a nylon string on the outer periphery of a water pipe (10) composed of a polyethylene pipe or the like,
On top of this, a presser winding tape (5), a plastic sheath (11) of polyethylene or the like are provided, and an iron wire sheath (7), a serving layer (8) and the like are applied.

FIG. 5 is a cross-sectional view of still another embodiment of the optical fiber composite submarine power cable according to the present invention. This specific example has the same structure as the specific example of FIG. 3 except that a metal layer such as a copper tape, an iron tape, a stainless steel tape or the like is provided on the winding layer of the optical fiber unit (3) and the plastic spacer (4). A tape layer (9) is provided.

In the case of a submarine power cable, for example, when a switch on land is operated, a switching surge occurs. Also, when a lightning strike occurs on an overhead power line connected to both ends of the submarine power cable, a lightning impulse enters the submarine power cable (these are collectively called surges).

When a surge enters a conductor and a metal sheath of a submarine power cable, a large potential may be generated on a metal body wound in the longitudinal direction of the cable outside the conductor. In the case of submarine power cables, these metal bodies are usually grounded at both ends and the potential is zero, but the longer the cable is, the larger the potential is generated in proportion to it, and the further away from the ground point, the larger the potential is generated The possibilities increase. In the case of the armored wire, such potential is not generated because it is uniformly grounded in seawater. However, in the case of the optical fiber unit according to the present invention, which is protected by plastic to prevent corrosion by seawater, a large electric potential is generated as the distance from the ground point at both ends increases, as described above. Breakage may occur, and seawater may enter the inside, corroding the metal pipe, or damaging the optical fiber with electrical breakdown energy.

As a countermeasure, as shown in FIG. 2 , the plastic coating layer (33) of the optical fiber unit (3) is made semiconductive, and the surge induction potential is extended over the entire length of the metal pipe of the optical fiber unit (3). (31) → Plastic coating layer (3
3) → Make sure that surge voltage does not rise by escaping into seawater.

In order to ensure this effect, as shown in FIG. 5, a semiconductive plastic coating layer is used.
By providing a metal tape layer (9) directly in contact with the outside of the arrangement layer of the optical fiber unit (3) provided with (33), the plastic coating layer of the optical fiber unit (3) is provided.
The ground resistance between (33) and seawater can be reduced, which is very preferable.

[0036]

As described above, according to the optical fiber composite submarine long body of the present invention, it is possible to prevent buckling of the optical fiber unit caused by bending of a cable or a water pipe, etc. Stable performance can be maintained over a period.

Further, in the submarine power cable, by making the plastic coating layer of the optical fiber unit a semiconductive layer, it is possible to prevent an abnormal induced potential caused by intrusion surge from being generated in the metal pipe of the optical fiber unit. The effect of the optical fiber which is not affected by such a potential can be utilized as it is.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of an optical fiber composite submarine power cable according to the present invention.

FIG. 2 is a cross-sectional view of a specific example of an optical fiber unit according to the present invention.

FIG. 3 is a cross-sectional view of another embodiment of the optical fiber composite submarine power cable according to the present invention.

FIG. 4 is a cross-sectional view of a specific example of an optical fiber composite water bottom water pipe according to the present invention.

FIG. 5 is a cross-sectional view of still another embodiment of the optical fiber composite submarine power cable according to the present invention.

FIGS. 6A to 6D are explanatory diagrams of experiments on the arrangement of optical fiber units.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Power cable core 2 Metal sheath 3 Optical fiber unit 31 Metal pipe 32 Optical fiber 33 Plastic coating layer 4 Plastic spacer 5 Holding tape 6
Plastic sheath 7 Iron wire sheath 8 Serving layer 9 Metal tape layer 10 Plastic water pipe 11 Plastic sheath

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyuki Amagai 1-3-1 Shimaya, Konohana-ku, Osaka-shi Sumitomo Electric Industries, Ltd. Osaka Works (72) Inventor Masayoshi Yamaguchi 1-1-1, Shimaya, Konohana-ku, Osaka-shi No. 3 Sumitomo Electric Industries, Ltd. Osaka Works (72) Inventor Hiroyuki Kimura 1-3-1, Shimaya, Konohana-ku, Osaka City Sumitomo Electric Industries, Ltd. Osaka Works (56) References JP-A-59-29305 (JP, A) JP-A-63-205623 (JP, A) JP-A-63-38220 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01B 11/22 G02B 6/44 366

Claims (4)

(57) [Claims] 1. An optical fiber in which an optical fiber is housed in a metal pipe having a coating layer of a plastic material having a melting point higher than that of the plastic sheath material inside a plastic sheath provided on a long body such as an electric power cable and a water pipe. arranging the units and spacers tightly wound, it is subjected to iron wire sheathing on the outside, a the plastic sheath material is polyethylene, is a plastic material of the coating layer on an optical fiber unit periphery polypropylene, polybutene, with nylon An optical fiber composite underwater elongated body characterized by the above-mentioned. 2. The optical fiber according to claim 1, wherein the elongate body is a power cable, and an optical fiber is provided inside a metal pipe having a coating layer of a plastic material having a melting point higher than that of the plastic sheath material on the outer periphery of a plastic sheath provided on the power cable. An optical fiber composite water bottom, wherein the optical fiber unit and the spacer are closely arranged, and an outer surface thereof is coated with an iron wire, and a plastic coating layer around the optical fiber unit is semiconductive. Long body. 3. An optical fiber composite underwater elongate according to claim 2, wherein a metal tape layer is provided on the outside where the optical fiber unit and the spacer are closely arranged, and an iron wire sheath is further provided on the outside thereof. body. 4. The optical fiber composite underwater elongated body according to claim 1, wherein the outer diameter of the spacer is larger than the outer diameter of the optical fiber unit.