JP2001051169A - Optical cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-weight optical cable capable of reducing a cross sectional area and improving the flexibility. SOLUTION: This optical cable consists of units 3 respectively manufactured by laminating a plurality of tape-shaped optical fiber cores 1, and forming an unit coating layer 2 made of a cushioning material around the laminated body, and not having a tensile strength body. One unit is located on the center, and a plurality of units are stranded up with inclusions 4 around the central unit to form a cable core. A cover winding 5 is applied onto the cable core, and then an envelope 6 is formed thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical cable containing a plurality of optical fiber ribbons, and more particularly to a multicore optical cable laid in a pipeline.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 8-160266 discloses an optical cable containing a tape-shaped optical fiber.
The structure described in “Sumitomo Electric” No. 148, pp. 1-5 is generally used.

FIG. 11 is a sectional view of an example of such an optical cable. In the figure, 1 is a tape-shaped optical fiber core,
1 is a slot rod, 12 is a tensile member, 13 is a slot, 14 is a presser winding, and 15 is a jacket.

In this optical cable, a tensile member 12 made of a steel stranded wire or the like is disposed at the center of a slot rod 11 made of plastic, and an optical fiber core, for example, is inserted into a slot 13 formed on the outer periphery of the slot rod 11. The configuration is such that the optical fiber ribbon 1 can be accommodated.
A holding roll 14 is wound around the outer periphery of the slot rod 11 containing the optical fiber, and a jacket 15 such as polyethylene is provided thereon.

When an optical cable is laid, a frictional force proportional to the weight of the optical cable is generated. In order to resist the frictional force, the optical cable is laid with a large tension. In order to withstand the tension at the time of laying, an optical cable is provided with a tensile strength member. The material used as the tensile strength member is steel wire or glass FRP for the purpose of withstanding the tension, but the tensile strength member has a high density. Is a factor that increases the weight of the optical cable, which leads to an increase in the weight, and as a result, a vicious cycle occurs in which the frictional force is further increased and the strength member is increased, and the weight of the optical cable is very heavy and the rigidity is increased. A phenomenon was occurring.

A slot type optical cable, which is a standard structure of a conventional multicore optical cable, has a structure in which a tape-shaped optical fiber is accommodated in a slot (groove) formed on the surface of a plastic slot rod. Since the slot is a structure for protecting the inner optical fiber ribbon from external force, the slot is required to have a high strength, and a dense plastic such as polyethylene is used. On the other hand, since the slot type optical cable is provided with a slot for accommodating the optical fiber core wire on the outer periphery of the slot rod, the number of optical fibers accommodated increases,
Many slots are required, and the outer diameter of the slot rod increases. The central portion of the multi-core optical cable is a lump of plastic constituting the slot rod, and the vicinity of the outer periphery close to the jacket is a rib of a slot made of a material having excellent strength. As a result, the weight of the optical cable increases,
Flexibility is impaired because the bending moment increases,
There is a problem.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an optical cable which can be reduced in cross-sectional area, has high flexibility, and is lightweight. .

[0008]

According to the first aspect of the present invention, there is provided an optical cable comprising a cable core formed by twisting a plurality of optical units, and having a jacket on the outer periphery of the cable core. The optical unit is composed of a laminated body in which a plurality of tape-shaped optical fiber cores are laminated, and a unit coating layer made of a buffer material applied to the outer periphery of the laminated body,
Further, the optical unit has no tensile strength member.

According to a second aspect of the present invention, in the optical cable according to the first aspect, the outer circumference of the tape-shaped optical fiber core is made of an ultraviolet curable resin, and the unit coating layer is made of foamed polyethylene. It is assumed that.

[0010]

FIG. 1 is a view for explaining an example of an embodiment of an optical cable according to the present invention. FIG. 1 (A) is a sectional view of the optical cable, and FIG. 1 (B) is a tape-like optical fiber. It is sectional drawing of an example of a core wire. In the figure, 1 is a tape-shaped optical fiber core, 1a is an optical fiber core, 1b is a tape coating,
2 is a unit coating layer, 3 is a unit, 4 is an inclusion, 5 is a press winding, and 6 is a jacket.

The tape-shaped optical fiber core 1 is shown in FIG.
As shown in FIG. 2, a plurality of optical fiber core wires 1a each having a protective coating applied to a glass fiber are arranged side by side and integrated with a tape coating 1b. In an embodiment of the present invention, the diameter 12
Four optical fiber core wires 1a having an outer diameter of 250 μm with a protective coating made of an ultraviolet-curable resin on a 5 μm glass fiber were integrated into a tape shape by a tape coating 1b using an ultraviolet-curable resin. Things. But,
The present invention is not limited to this specific example, and the material of the protective coating and the tape coating is not limited to the above-described materials, and any appropriate material can be used. Also, the number of optical fiber cores 1a to be integrated is not limited to four, and an appropriate number of tape-like optical fiber cores can be used.

As shown in FIG. 1A, a plurality of tape-shaped optical fibers 1 are laminated, and a unit coating layer 2 made of a buffer material is applied around the laminated body to form a unit 3. It is configured. The unit has no strength members. Then, one unit is arranged at the center, and a plurality of units are twisted around this unit to form a cable core. In the figure, all units 3 have the same outer diameter, and seven units 3 are twisted to form a cable core. However, the configuration of the unit 3 may be arbitrary, and the number of optical fibers and the outer diameter of the optical fiber in the unit 3 may not be the same in all of the plurality of units. As the unit coating layer 2 made of a buffer material,
It is desirable to provide an elastic body having an elastic modulus of 1 kg / mm ² or more and 10 kg / mm ² or less with a thickness of 0.1 mm or more, and the material may be a heat-resistant material such as silicone resin, foamed polyethylene, or soft vinyl chloride. It can be selected from plastic resins and the like. Further, the unit coating layer 2 may be formed by extruding and coating the periphery of the laminated body of the tape-shaped optical fiber core wires 1 or may be formed by winding a ribbon-shaped material.

In one example of the present invention, an optical cable is formed by twisting together a plurality of units 3 together with an intervening member 4, winding a holding roll 5, and applying a jacket 6 thereon. The inclusions 4 are provided to make the outer shape easy to be substantially circular, and a string-like or fiber-like thing is suitable. The inclusion 4 is not always required. The jacket 6 is formed by extrusion coating using a thermoplastic resin such as PE (polyethylene) or PVC (vinyl chloride).

In the optical cable according to the present invention, an optical cable containing optical fibers at a high density can be constructed by assembling a plurality of units each having a plurality of tape-shaped optical fiber cores laminated and coated with a unit. Further, a unit coating layer 2 made of a buffer material is formed on the outer periphery of the unit 3.
Has an effect of protecting the optical fiber from an external force (side pressure) received at a contact point with the jacket or another unit. If the elastic modulus is 10 kg / mm ² or less, the cushioning property is sufficient. Further, by setting the elastic modulus to 1 kg / mm ² or more, it is possible to prevent the unit coating layer 2 from being broken during the manufacturing process and during use. The thickness of the unit coating layer 2 is set at 0. 0 to maintain cushioning and mechanical strength.
It is desirable that it be 1 mm or more.

By packing such units densely, by disposing the optical fiber in a portion which has been a plastic rod in the prior art, the number of optical fibers accommodated per cable cross-sectional area can be increased. . Further, instead of the slot portion made of the conventional plastic material, a unit 3 which can be individually shifted is twisted and has a low elastic modulus unit coating layer 2.
Since the gaps between the units covered by the above are dispersed, an optical cable which is lightweight, has extremely high flexibility, and is easy to lay can be obtained. Furthermore, as compared with optical cables having the same number of cores of other structures, even in a structure accommodating a number of cores of several tens or more, the optical cable of the present invention can have a small cross-sectional area and a small installation space for the optical cable. . Furthermore, since it is flexible and lightweight, it is suitable for ordinary traction laying and also suitable for a method of laying in a pipeline by airflow.

A specific example of the optical cable described with reference to FIG. 1 will be described. In a specific example, a plurality of units 3 in which a plurality of tape-shaped optical fiber cores 1 are stacked and a unit coating layer 2 is applied are bundled. Optical fiber ribbon 1
Has a surface coated with calcium carbonate. The application of calcium carbonate makes it difficult for the tape-shaped optical fiber cores to adhere to each other. Therefore, when the optical cable is bent, a difference in wire length occurs between adjacent tape-shaped optical fiber cores, resulting in a tape-shaped optical fiber core. The wire is less likely to be kinked, and an increase in transmission loss due to sharp bending distortion can be suppressed. In this specific example, the unit coating layer 2 is formed by foaming 50% of thermoplastic resin polyethylene, and the thickness of the laminated body of the tape-shaped optical fiber core 1 is 0.2 mm even at the portion where the coating thickness is minimum. So that the coating was circular. Unit 3 with seven bundled together with inclusions 4
On top of each other, as a holding roll 5, a thickness of 0.1 m
m, and a 1.5 mm-thick foamed polyethylene was coated thereon as a jacket 6.

In order to reduce the diameter and weight of the cable of the present invention, and to compare the occupancy of the optical fiber with the conventional cable, a conventional optical cable having the structure described with reference to FIG. 11 was used as a comparative example. In this comparative example, a steel twisted wire tensile strength member 12 is disposed at the center of a polyethylene slot rod 11, and a plurality of tape-shaped optical fiber core wires 1 are accommodated in a slot 13. A plastic tape having a thickness of 0.1 mm is wound on the slot rod 11 as a holding roll 14, and a polyethylene tape having a thickness of 1.5 mm is coated thereon.

FIG. 2 shows the results of comparing the specifications of the optical cable having the structure of the present invention with the optical cable having the conventional structure of the comparative example described with reference to FIG. As for the tape-shaped optical fiber cores, all the optical cables having 300 or less cores use four tape-shaped optical fiber cores, and those having 400 or more cores use eight tape-shaped optical fiber cores. The thickness of each of the tape-shaped optical fibers is 0.3 mm.

The optical cable having the structure of the present invention has an outer diameter reduced by about 25% and a mass reduced by 50% or more as compared with the optical cable having the conventional structure. Approximately 2
As a result, the diameter and weight have been greatly reduced, and the occupancy rate of the optical fiber has been increased. For this reason, in the case of the pressure feeding method in which an optical cable is laid in a pipeline by the power of compressed air,
Since the pumping characteristic is proportional to the outer diameter / mass ratio of the optical cable, the pumping performance of the optical cable of the present invention structure is improved by about 25% as compared with the optical cable of the conventional structure.

For this reason, in the case of the construction method in which the optical cable is laid in the pipeline by pulling the end of the optical cable, the optical cable having the conventional structure grips the steel stranded wire of the tensile strength member and pulls the optical cable.
However, in the optical cable having the structure of the present invention, since the mass of the optical cable itself is small, even if the friction coefficient between the pipeline and the jacket of the optical cable is greatly estimated to be 0.5, the breakage probability of the optical fiber is low. By pulling the optical fiber core directly with a low pulling force equivalent to 0.3%, installation of about 1 km
It can be laid in a series length.

In an optical cable laid in an underground conduit, water in the conduit may enter the optical cable from a closure or an optical cable jacket. However, the water-absorbing polymer or the water-absorbing polymer may be introduced into the optical cable. By inserting a covered plastic string or the like, water can be prevented from being transmitted into the optical cable. In the optical cable described with reference to FIG. 1, the above-described plastic string may be used as the inclusion 4.

Next, in the optical cable of the present invention described with reference to FIG. 1, the presence or absence of twisting of the unit when the units are twisted will be described.

FIG. 3 shows a case where twisting is performed, and FIG. 4 shows a case where twisting is not performed. In each case, a cross-sectional view showing only the cable core portion in the optical cable of FIG. It is an enlarged view inside. In the figure, the same parts as those in FIG.

In an optical cable twisted with a twist, as shown in FIG. 3A, the laminated body of the tape-shaped optical fiber cores 1 is twisted in the same direction in all units 3. I have. On the other hand, in each unit 3, the outer shape of the laminated body of the tape-shaped optical fiber cores 1 is substantially rectangular, whereas the outer shape of the unit coating layer 2 is substantially circular. As described above, the thickness of the unit coating layer 2 is
And a thin portion t exists. However, in an optical cable having a twist, portions close to the thin portion t do not come into contact with each other between adjacent units.
When the pressing force acts on the tape-shaped optical fiber core 1 in the adjacent unit, the thickness of the unit coating layer 2 between the tape-shaped optical fiber cores can be made sufficiently large. .

On the other hand, in an optical cable twisted without twisting, as shown in FIG.
The laminated body of the tape-shaped optical fiber cores 1 is twisted so as to face radially with respect to the unit arranged at the center. Then, as shown in FIG.
Between the adjacent units, the portions close to the thin portion t come into contact with each other, and when a pressing force acts on the unit 3, the thickness of the unit coating layer 2 between the tape-shaped optical fibers in the adjacent unit is reduced. Due to the thinness, the pressing force applied to the tape-shaped optical fiber core wire 1 is large, which may increase the loss. Therefore, it is desirable that the tape-shaped optical fiber core wire in the unit is not twisted, and a plurality of units are twisted and assembled.

Two types of 1000-core optical cables, an optical cable twisted with twisting and an optical cable twisted without twisting, are trial-produced, and the optical fiber cable is gripped by holding the tape-shaped optical fiber core of the optical cable. 300kg tension equivalent to about 0.3% elongation strain
(Corresponding to the own weight of the optical cable of 1 km), the transmission loss characteristics in a state where the optical cable was pulled were measured.

FIG. 5 shows the measurement results. The type of the optical fiber is an SM core, and the measurement wavelength is in a 1.55 μm band. The twist pitch of the unit assembly is 200mm, 400mm, 80
It is performed with four types of 0 mm and 1600 mm.

Without the twisting, the thinnest parts of the unit may hit each other, and the maximum value of the transmission loss exceeds the commonly used standard of 0.28 dB / km. It can be seen that the fiber is adversely affected. Referring to FIG. 5, if the twist pitch is increased, the transmission loss is expected to be within the standard even in a structure without twisting. However, when the twist pitch is increased, a bend having a small radius of curvature is added to the optical cable. In such a case, a wire length difference occurs between the units, which may cause distortion in the optical fiber core wire. Therefore, it is desirable that the twist pitch be suppressed to 1600 mm.

With respect to the take-out property of the tape-shaped optical fiber core from the unit, if the tape-shaped optical fiber core and the coating of the unit have a low adhesion, the tape-shaped optical fiber core is taken out from the unit. Further, it is not necessary to carefully remove the coating residue of the unit adhered to the tape-shaped optical fiber core.

Therefore, in FIG.
As a trial, a thermoplastic resin or a silicone resin different from the outermost layer of the tape-shaped optical fiber core 1 was used, and it was not necessary to carefully remove the coating residue of the unit adhered to the tape-shaped optical fiber core. That was confirmed. Further, even with the same resin, the problem could be solved by providing a silicone-based lubricant between the tape-shaped optical fiber core wire 1 and the unit coating layer 2 as a different peeling layer.

FIG. 6A is a sectional view of one unit. In the figure, the same parts as those in FIG. In the unit having this structure, a combination of the material of the outermost layer of the tape-shaped optical fiber core 1 and the material of the unit coating layer 2 and the presence or absence of a release layer were experimentally produced.
The adhesion of the coating residue when the tape-shaped optical fiber was removed from the unit was examined.

FIG. 7 shows the results of the investigation on the adhesion of the coating residue. If the prototype number is No. 1 to No. In the optical cable of No. 3, since the material of the outermost layer of the tape-shaped optical fiber and the material of the unit coating layer were made different, the residue of the unit coating did not adhere to any of them. On the other hand, in No. 5, in which the material of the outermost layer of the tape-shaped optical fiber core and the material of the unit coating layer were the same resin, the residue of the unit coating was remarkably adhered. In some cases, the coating of the core wire itself was peeled off.
However, no. As shown in FIG. 4, in the structure in which the lubricant is applied to the tape-shaped optical fiber core wire, the coating residue is not attached.

Further, in the structure in which the unit covering layer is provided by winding the laminate of the tape-shaped optical fiber cores, it is easy to take out the tape-shaped optical fiber cores. In addition, this tape winding structure is such that when a tape-shaped optical fiber core is laminated, plastic inclusions are added, and the tape is wound thereon, and the unit coating layer is formed in a substantially circular cross section. The cross-sectional shape of the applied unit can be easily rounded, the units can be easily assembled, and this is preferable for transmission loss characteristics.

FIG. 8 shows the result of a test on the take-out property of the optical fiber ribbon. No. 6-No. 1
No. 1 is No. 1 described in FIG. 1 to No. Structure 3 is a case where foamed polyethylene is used as the unit coating layer, and the foaming ratio is changed. No. 12-N
o. Reference numeral 15 denotes a structure in which a depression 7 is provided in a part of the unit coating layer 2 as shown in FIG. 6B, and the size of the depression is changed. The material of the unit coating layer 2 is polyethylene. I have.

No. 6-No. As you can see from 11,
The higher the foaming ratio, the better the tape-shaped optical fiber core wire can be taken out, but the foaming ratio is preferably 10% or more,
It is more preferably at least 20%. However, the foaming rate is 8
If it exceeds 0%, the coating may be unintentionally broken, so that the foaming ratio is desirably 80% or less.

Also, if the size of the depression on the coating is about 0.5 mm into which the nail can be inserted, the coating can be torn.
The result that the deeper the dent was, the easier it was to tear.

The cable jacket will be described. Regarding the removability of the cable sheath, since the optical cable structure of the present invention is not protected by the slot, the tape-like optical fiber core inside the cable is accidentally cut when the cable sheath is torn. Can be considered.

FIG. 9 is a cross-sectional view for explaining the structure of the cable jacket which makes it easier to remove the jacket. In the figure, 8
Is the inside of the cable, 9a is the inner layer of the jacket, 9b is the outer layer of the jacket, 10a is the inner layer of the jacket, and 10b is the outer layer of the jacket.
Regarding the structure of the cable interior 8, the cable core of the present invention described above is used, and it is needless to say that a plurality of units as described with reference to FIG.

Each of the jackets shown in FIGS. 9A and 9B has a two-layer structure. In FIG. 9A, the inner layer 9a of the jacket is shown.
Is a material having a Young's modulus higher than that of the outer layer 9b of the jacket. In a specific example, the Young's modulus of the inner layer 9a of the jacket was 50 kg / mm ^2, and the Young's modulus of the outer layer 9b of the jacket was 20 kg / mm ² . In FIG. 9B, the color of the inner layer 10a of the jacket is different from the color of the outer layer 10b of the jacket.

An optical cable having the above-mentioned structure was manufactured as a trial, and a test for tearing the outer sheath was performed on a single-layer optical cable manufactured as a trial as a comparative example. The test content is
The operation was performed by five workers, in which the sheath of ten 100-fiber optical cables was cut off with a sheath cutter in 30 minutes. The results are shown in FIG.

In the case of the single-layer jacket structure of the comparative example, there was no damage to the tape-shaped optical fiber core wire, but two of them failed to cut to the unit coating inside the optical cable. On the other hand, in the case of a two-layer structure,
The optical cable A and the optical cable B did not damage the unit coating inside the optical cable as well as the tape-shaped optical fiber. As described above, the removal property of the optical cable jacket is improved, and the work of removing the jacket is facilitated in the intermediate branch where the jacket must be cut without damaging the inside of the optical cable. The outer layer is not limited to the two-layer structure. The outer layer has a three-layer or more outer layer structure. The inner layer has a larger Young's modulus than the outer layer, or has a different color. You may. Of course, both the Young's modulus and the color may be changed.

[0042]

As is apparent from the above description, according to the present invention, a plurality of tape-shaped optical fiber cores are laminated and unit-coated to form a close-packed structure. The outer diameter of the optical cable is kept low, and the weight of the optical cable can be reduced. Therefore, when sending the optical cable of the present invention into a pipeline laid underground or the like by the force of compressed air or when pulling and laying it, a long section optical cable can be laid with low pressure and low pulling force. Further, since the optical cable has a small diameter, the number of optical cables accommodated can be increased when a plurality of optical cables are laid in a pipeline. Further, by using a buffer material as the unit coating, it is possible to prevent the transmission loss of the optical fiber from increasing.

[Brief description of the drawings]

FIG. 1 is a view for explaining an example of an embodiment of an optical cable according to the present invention, and FIG.
FIG. 1B is a cross-sectional view of an example of the optical fiber ribbon.

FIG. 2 is an explanatory diagram showing a result of comparing specifications of an optical cable having a structure of the present invention and an optical cable having a conventional structure.

FIG. 3 is a cross-sectional view of a portion of a cable core when the optical cable of FIG. 1 is twisted with twisting and an enlarged view in a circle shown by a broken line.

FIG. 4 is a cross-sectional view of a portion of a cable core when the optical cable of FIG. 1 is twisted without being twisted, and an enlarged view in a circle shown by a broken line.

FIG. 5 is an explanatory diagram illustrating the results of measuring transmission loss characteristics of an optical cable twisted with twisting and an optical cable twisted without twisting.

FIG. 6 is a cross-sectional view for explaining an embodiment of an optical cable unit according to the present invention.

FIG. 7 is an explanatory diagram of a property of taking out a tape-shaped optical fiber core from a unit in the optical cable of the present invention.

FIG. 8 is an explanatory view of the result of a test on the take-out property of a tape-shaped optical fiber core.

FIG. 9 is a cross-sectional view illustrating a structure of a cable jacket that facilitates removal of the jacket.

FIG. 10 is an explanatory diagram of a result of a test for tearing a jacket.

FIG. 11 is a sectional view of an example of a conventional optical cable.

[Explanation of symbols]

1 ... tape-shaped optical fiber core, 1a ... optical fiber core,
1b: Tape coating, 2: Unit coating layer, 3: Unit, 4: Inclusion, 5: Holding coil, 6: Jacket, 7: Depression, 8: Inside of cable, 9a: Inner layer of jacket, 9b: Jacket Outer layer, 10a ... inner layer of the jacket, 10b ... outer layer of the jacket.

Claims (2)

[Claims] 1. An optical cable comprising a cable core formed by twisting a plurality of optical units, and comprising a jacket on the outer periphery of the cable core, wherein the optical unit comprises a plurality of tape-shaped optical fiber cores. An optical cable, comprising: a laminated body obtained by laminating the above; and a unit covering layer made of a buffer material applied to the outer periphery of the laminated body, and wherein the optical unit does not have a tensile member. 2. The optical cable according to claim 1, wherein the outer periphery of the tape-shaped optical fiber core is made of an ultraviolet curable resin, and the unit coating layer is made of foamed polyethylene.