JP2787138B2 - Submarine optical cable - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multicore undersea optical cable.

[Prior art] Submarine optical cables can economically transmit a large amount of information over long distances, have higher secrecy than communication satellite systems, and are not affected by weather. It is going to be widely used for lines. FIG.
FIG. 8B shows an enlarged cross section of an optical fiber unit of a conventional example of a submarine optical cable used in the waters near Japan. A maximum of 12 optical fiber core wires 22 having an outer diameter of 0.4 mm are assembled around a central steel wire 21 located at the center of the cable (the figure is an example of a six-core structure), and these are filled with a buffer layer 23. An optical fiber unit 20 having an outer diameter of 2 to 3 mm is formed by applying the coating layer 24. Then, in order to protect the optical fiber unit 20 from external force such as seawater pressure, an inner-layer butt-molded pressure-resistant tube 25 and a steel wire 26 as a strength member are sequentially applied to the periphery thereof, and further welded to prevent moisture permeation into the inside. A molded pressure tube 27 is provided. Adjacent steel wires
The gap between 26 and the gap between the optical unit 20 and the inner-layer butt-molded pressure-resistant tube 25 are filled with resin to prevent water running in the cable. Further, a polyethylene 28 is provided on the outer periphery as a jacket. The outer diameter of the entire cable is 24 mm. Currently, submarine optical cables used in various countries around the world have a structure in which one optical fiber unit housed in a pressure-resistant tube is arranged at the center of the cable, which is common to the above-described conventional example.

[Problems to be Solved by the Invention] The number of optical fibers housed in the conventional submarine optical cable as described above is 12 at the maximum. On the other hand, the number of optical cables used in land-based trunk lines is several tens or more. For this reason, when connecting a land optical cable and a submarine optical cable, it is necessary to connect a plurality of expensive submarine optical cables to one land optical cable. Appearance is desired.

However, if several tens of optical fibers are to be stored in a single optical fiber unit located at the center of the cable as in the conventional submarine optical cable structure, an ultra-large aggregate that can collect many optical fiber cores is required. In addition, there arises a problem that identification and separation of the optical fiber become difficult. In addition, manufacturing a long unit having a length of 10 km by assembling a large number of expensive and fragile optical fibers at one time involves a great risk of manufacturing itself. Further, if the outer diameter of the pressure-resistant tube is increased in proportion to the outer diameter of the optical fiber unit, the outer diameter and weight of the cable increase, and it becomes difficult to manufacture a long cable. For these reasons, it has been difficult to realize a multicore submarine optical cable.

An object of the present invention is to provide a multicore submarine optical cable that can be manufactured in a long length.

[Means for Solving the Problems] In order to achieve the above-mentioned object, a submarine optical cable according to the present invention includes a plurality of optical fiber core wires arranged around a support covered with a soft resin, A plurality of optical fiber units having a circular cross section having a silicon resin layer, a soft resin layer, and a hard resin layer sequentially provided around the plurality of optical fiber cores, and provided around the plurality of optical fiber units. An optical fiber aggregate having a circular cross section including a resin coating layer, and a pressure-resistant tube structure accommodating the optical fiber aggregate, which are arranged on the circumference in the cross section and twisted at a twist pitch of 300 mm or less. A steel wire having a first diameter of less than or equal to the first diameter of the steel wire and each of which is arranged between each of the first diameter steel wires and twisted at a twist pitch of 300 mm or less. Diameter smaller than the first diameter Having the same number of steel wires as the first diameter steel wire, and a copper tape welded pressure-resistant tube provided on the outer periphery of the first diameter steel wire and the second diameter steel wire, The first diameter steel pipe and the second diameter steel pipe;
A pressure-resistant pipe structure in which a resin is filled in a gap around a steel pipe having a diameter of, and a polyethylene jacket provided around the pressure-resistant pipe structure.

[Operation] In the present invention, 1) the optical fiber unit is largely twisted to form an optical fiber unit aggregate, and 2) the steel wires gathered around the optical fiber unit aggregate compete with each other to achieve a small diameter and sufficient diameter. A pressure tube having a high lateral pressure strength is constructed.

By assembling the optical fiber units to form an optical fiber unit assembly, it becomes possible to easily manufacture an optical fiber unit having a water running prevention function comprising a large number of optical fibers of about 50 cores. In addition, since each optical fiber unit is composed of about 12 optical fibers, a large-scale collective device is not particularly required, and no special manufacturing equipment is required. In addition, after manufacturing fragile optical fibers and manufacturing individual optical fiber units, the risk of damaging the optical fibers is significantly reduced, so that the optical fiber unit aggregate containing a large number of optical fibers can be easily separated. Can be manufactured, and manufacturing risk can be reduced.

Furthermore, the inner layer is composed of a large-diameter steel wire, and the outer layer is composed of a circumscribed circle formed by the inner-layer steel wire and a thin-diameter steel wire having an outer diameter in contact with an adjacent inner-layer steel wire. By competing steel wires, it is possible to construct a pressure tube with sufficient lateral pressure strength even without an inner layer pressure tube, and to increase the storage area of the optical fiber unit in the pressure tube by the amount that the inner layer pressure tube can be omitted. Is now possible. As a result, it is not necessary to increase the outer diameter of the pressure-resistant tube, and it is possible to realize a multicore submarine optical fiber cable without increasing the outer diameter of the cable as compared with a conventional submarine optical cable, and to manufacture a long-length optical fiber cable.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1A shows a cross section of an embodiment of the submarine optical cable according to the present invention, and FIG. 1B shows an enlarged cross section of the optical fiber unit. In the present embodiment, a maximum of 12 optical fiber core wires 22 having a diameter of 0.25 mm are assembled around a support 30 made of a steel wire 30A whose surface is coated with a resin 30B having a low Young's modulus, which is located at the center of the cable. It is covered with silicon resin 22A. An optical fiber unit having an outer diameter of 2.2 mm is provided with a buffer layer 23A around the silicone resin 22A and a coating layer 24A around the buffer layer 23A.
20 are formed. And this optical fiber unit
20 are grouped around a center support 31 made of a steel wire 31A whose surface is coated with a resin 31B having a low Young's modulus. The gap between the optical fiber units is filled with a buffer layer 23B, and a coating layer 24B is further provided to form an optical fiber unit assembly 32 having an outer diameter of 5.5 mm.

Next, a pressure-resistant tube for accommodating the optical fiber unit and protecting the optical fiber unit from external force such as seawater pressure will be described. As the strength member, the inner layer is composed of a thick steel wire 26A, the outer layer is composed of a circumscribed circle of the inner steel wire 26A and a thin steel wire 26B of an outer diameter so as to contact adjacent inner steel wires 26B. And compose a tubular body. In this embodiment, there are ten inner-layer steel wires 26A and ten outer-layer steel wires 26B, which are twisted at a pitch of 270 mm. In the cross section, the ten inner-layer steel wires 26A circumscribe a circle slightly larger than the outer diameter of the optical fiber unit assembly 32, for example, a circle of 5.55 mm. A welded pressure-resistant tube 27 is provided around the steel wires 26A and 26B to prevent moisture permeation into the inside, and thus a pressure-resistant tube is configured. The optical fiber unit assembly 32 is housed in the pressure tube, and the gap between the welded pressure tube 27, the steel wires 26A, 26B and the coating layer 24 is filled with resin to prevent water running in the cable. Further, the outer periphery of the welded pressure-resistant tube 27 is provided with three layers of polyethylene 28A, 28B and 28C as a core coating, an intermediate jacket and a jacket, respectively. However, the intermediate jacket may be omitted depending on the use environment of the cable.

Table 1 shows the materials used and the dimensions of the embodiment shown in FIG.
The UV resin in the table indicates an ultraviolet curable resin. Buffer layer 23
A, the Young's modulus of the UV urethane used in 23B is 4 kg / mm ² approximately, the Young's modulus of the UV urethane using the coating layer 24A, the 24B is 35 kg / mm ²
It is about. A soft resin is used for the buffer layer that is in direct contact with the optical fiber core and the optical fiber unit, so as to reduce the stress acting on the optical fiber. In this embodiment, the optical fiber
Although four optical fiber units each having twelve cores are assembled, the present invention is not limited to this number.

FIG. 2 shows a loss-wavelength characteristic of the cable of the present embodiment, and FIG. 3 shows a change in optical loss in each manufacturing process. Single length 5k
m cable was manufactured, the loss wavelength characteristics of the single mode optical fiber for a wavelength of 1.3 μm were measured, and the change in loss at a wavelength of 1.3 μm between processes was obtained. 2 and 3, it can be seen that the increase in loss due to the microbend does not occur not only in the used wavelengths of 1.3 μm and 1.55 μm but also in the longer wavelength region. It was confirmed that this cable structure can realize a low loss multi-fiber submarine optical cable. In addition, 1000 m of this cable was put in a high-pressure vessel, and water pressure of 500 atm was applied from one terminal, and the time required for water running in the cable to be discharged from the other terminal was measured. It was not observed, and it was confirmed that it had a sufficient water running prevention function.

FIG. 4 shows the results of the lateral pressure test of the pressure-resistant tube of the cable of the present embodiment. In the experiment, the pressure tube was compressed with a parallel flat plate using a static compression tester, and changes in the load and the outer diameter of the pressure tube were measured. In the figure,
The black circles show the measurement results of the pressure resistance structure of the cable of the present invention.
On the other hand, open circles are the measurement results of the conventional pressure-resistant structure used for comparison. In this conventional structure, 16 steel wires with an outer diameter of 1.240 mm are assembled in the inner layer so that a unit with the same outer diameter (5.5 mm) as the unit of the present invention can be housed, and an outer diameter of 1.755 mm
16 steel wires are assembled and a 0.6 mm thick copper tape is butt-welded to form a pressure-resistant tube with an outer diameter of 11.8 mm. A submarine optical cable laying device, such as a drum engine or a linear engine, installed on the laying ship applies a lateral pressure of about 100 kg / cm to the cable. The pressure-resistant tube needs a lateral pressure strength enough to protect the optical fiber unit from such a lateral pressure. As shown in FIG. 4, the withstand voltage structure of the present invention can satisfy the required withstand voltage. In comparison with this, it can be seen that the conventional pressure-resistant structure is significantly inferior in lateral pressure resistance. This difference is due to the difference in the number of steel wires. In this embodiment, the number of lines of the inner layer is 10, whereas the number of the conventional pressure-resistant tubes is 16. When the outer diameter of the unit in which the pressure-resistant tube can be stored is constant, the wire diameter becomes thinner as the number of wires increases, and when a lateral pressure acts on the pressure-resistant tube, the steel wire is easily dropped. Therefore, the anti-lateral pressure is deteriorated.

FIG. 5 shows the calculation results of the effect of the number of steel wires on the lateral pressure resistance characteristics. As shown in Fig. 6, the calculation was performed by assembling n steel wires with a twist pitch of 300 mm to accommodate a unit with an inner diameter of 5.5 mm, and applying a side pressure of 100 kg / cm to a pressure-resistant tube model with a 0.6 mm-thick copper pipe. The amount of elongation strain and the change in the outer diameter generated in the pressure-resistant tube when acted was determined by elasticity calculation. Naturally, as the number of steel wires increases, the diameter of the steel wire decreases.
It can be seen that when the number of copper wires shown on the horizontal axis becomes 12 or more, the strain increases rapidly. When the strain amount is about 0.3% or more, plastic strain remains in the pipe made of a copper material, and there is a possibility that a loss increase caused by a compressive force acting on the internal optical fiber unit may remain. As in the present invention, the number of steel wires is 10
It is understood that the anti-lateral pressure characteristics are satisfied only when the content is less than the above. However, from the viewpoint of flexibility, the number of steel wires is preferably 6 or more, more preferably 8 or more. The number of steel wires can be reduced as the outer diameter of the optical fiber unit assembly is smaller. As shown in FIG. 8, in the conventional submarine optical cable, the maximum number of optical fibers was 12 or less, so that the outer diameter of the unit could be reduced to about 3 mm or less. Therefore, the inner pressure tube of the butt was provided between the steel wire layer and the unit, and the two-layer pressure tube of the inner layer and the outer layer was able to satisfy the lateral pressure characteristics. However, as the outer diameter of the unit becomes larger, providing an inner pressure tube increases the outer diameter of the cable,
Long-life, which is one of the important characteristics of submarine cables, and economic efficiency are impaired.

FIG. 7 shows the effect of the steel wire twist pitch on the lateral pressure characteristics. The number of steel wires is 10, and the other calculation conditions are the same as in FIG. It is understood that the distortion can be reduced to the allowable limit of 0.3% or less by setting the twist pitch shown on the horizontal axis to 300 mm or less. In FIG. 1 which is an embodiment of the present invention, the reason why the outer steel wire layer is provided in contact with the gap between the inner steel wire layers is that the competition between the steel wires is enhanced to prevent the shape loss, and the pressure-resistant pipe This is in order to increase the breakdown voltage. Also,
Since this structure has a 53 mm ² as the cross-sectional area of the steel wire, can be secured more than 10 tons as a cable break tension, laying into the deep sea, it is possible to sufficiently withstand huge tension applied to the cable in the repatriation . Further, the cable of the present invention is made of a material which has been used as a submarine optical cable, such as steel wire, copper pipe, urethane resin, polyethylene, etc., and even if it is used for a long period of time, hydrogen is generated from the material used and light loss occurs. Therefore, it is possible to configure a submarine transmission line with extremely long-term reliability without the risk that the number of submarine transmissions increases.
In this cable, a dummy fiber can be used as necessary, or a dummy unit such as a polyethylene rod can be used instead of the 12-core optical unit.

[Effects of the Invention] As described above, according to the present invention, a multi-fiber fiber having about 48 fibers can be unitized without deteriorating optical fiber characteristics such as low loss and wide band. Further, it is possible to realize a pressure-resistant tube capable of protecting the optical unit from a huge lateral pressure and tension acting upon the installation and a high water pressure acting for a long time under a severe environment under the seabed. The cable of the present invention has a function of preventing water running, there is no risk of loss increase due to hydrogen, furthermore, it is possible to manufacture long lengths up to several tens of kilometers, and there is a small risk of failure such as fiber breakage during manufacturing. It is possible to provide an undersea optical cable that can satisfy the required conditions, is practical and reliable, and is economical.

[Brief description of the drawings]

1A is a sectional view of an embodiment of the present invention, FIG. 1B is an enlarged sectional view of an optical fiber unit, FIG. 2 is a loss-wavelength characteristic diagram of the embodiment of the present invention, and FIG. FIG. 4 is a diagram showing a change in loss in the process, FIG. 4 is a diagram of the lateral pressure resistance, FIG. 5 is a diagram showing the relationship between the lateral pressure resistance and the number of steel wires, FIG. 6 is a cross-sectional view of a cable model for calculating the lateral pressure. FIG. 7 is a diagram showing the relationship between the lateral pressure resistance and the twist pitch. FIGS. 8A and 8B are a cross-sectional view of a conventional example and an enlarged cross-sectional view of an optical fiber unit. 20: Optical fiber unit, 21: Central steel wire, 22: Optical fiber core wire, 23A, 23B: Buffer layer, 24A, 24B ... Coating layer, 25: Inner layer butt-molded pressure-resistant tube, 26A, 26B ... steel wire, 27 ... welded pressure-resistant tube, 28, 28A, 28B, 28C ... polyethylene coating, 30 ... support, 31 ... center support, 32 ... optical fiber unit assembly.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-222214 (JP, A) JP-A-61-97607 (JP, A) JP-A-61-75310 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) G02B 6/44 366

Claims (1)

(57) [Claims] 1. A plurality of optical fiber cores arranged around a support covered with a soft resin, and a silicon resin layer sequentially provided around the plurality of optical fiber cores. A plurality of optical fiber units each having a circular cross section having a resin layer and a hard resin layer, and an optical fiber aggregate having a circular cross section including a resin coating layer provided around the plurality of optical fiber units; Pressure-resistant tube structure for housing
It is arranged on the circumference in the cross section, twist pitch 300 mm
A steel wire having a first diameter of 10 or less twisted below, and a twist pitch of 300 mm arranged outside each of the first diameter steel wires and between each of the first diameter steel wires. A steel wire having a diameter smaller than the first diameter and having the same number as the steel wire of the first diameter and the outer circumference of the steel wire of the first diameter and the steel wire of the second diameter, which are twisted below. A pressure-resistant pipe structure having a welded pressure-resistant pipe made of copper tape, wherein a resin is filled in gaps around the first diameter steel pipe and the second diameter steel pipe; A submarine optical cable having a polyethylene jacket provided around the periphery.