JP3523996B2 - Fiber optic cable - 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 cable having a structure in which a tape-shaped optical fiber core wire is housed in a cylindrical space.

[0002]

2. Description of the Related Art As one of the methods for realizing a multi-fiber optical fiber cable, a tape-shaped optical fiber core wire is used which is formed by aligning and coating optical fibers to form a tape. By stacking a plurality of the tape-shaped optical fiber core wires, a multi-fiber optical fiber cable can be easily constructed. However, merely laminating a plurality of tape-shaped optical fiber core wires is easily affected by an external force, and the microbend loss increases. As a countermeasure against this, for example, in the optical fiber cable described in Japanese Patent Laid-Open No. 8-278432, a structure in which a plurality of tape-shaped optical fiber core wires are housed in a metal tube is adopted.

However, in the conventional structure in which only the tape-shaped optical fiber core wire is directly housed in the cylindrical space, the optical fiber core wire located at the end of the tape-shaped optical fiber core wire is the inner wall of the metal cylinder. There is a problem that the transmission loss is likely to increase due to the lateral pressure from Therefore, to prevent lateral pressure from acting on the tape-shaped optical fiber core, enlarge the cylindrical space, or limit the number of cores and the number of laminated tape-shaped optical fiber cores stored in the cylindrical space. There was a fiber cable design problem.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an optical fiber which can efficiently accommodate a tape-shaped optical fiber core wire in a cylindrical space and has good loss characteristics. It is intended to provide a cable.

[0005]

According to a first aspect of the present invention, a plurality of tape-shaped optical fiber cores are laminated, a cushioning filler is arranged around the cores, and a plastic material containing a tension member is used. An optical fiber cable having a structure housed in a formed cylindrical space, wherein the space factor of the cushioning filler in the space excluding the tape-shaped optical fiber core in the cylindrical space is In addition to 10 to 50%, the cushioning filler is formed by stacking tape-shaped optical fiber core wires and twisting them in one direction or while reversing the direction.

According to a second aspect of the present invention, in the optical fiber cable according to the first aspect, the plurality of tape-shaped optical fiber core wires are made of one kind or a combination of four kinds or more and 12 kinds or less. It is characterized by becoming.

The invention described in claim 3 is the optical fiber cable according to claim 1 or 2, wherein the cushioning filler is a yarn or a fiber bundle.

According to a fourth aspect of the present invention, in the optical fiber cable according to any one of the first to third aspects, the cushioning filler has a water absorbing property. Is.

[0009]

[0010]

[0011]

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An outline of an optical fiber cable of the present invention will be described. The basic configuration is to stack multiple tape-shaped optical fiber cores, place a cushioning filler around them at an appropriate space factor, and then place the inside of a cylindrical member made of metal or plastic. It is stored in a cylindrical space. In this way, the cylindrical member itself accommodating the tape-shaped optical fiber core wire may be used as the jacket to form an optical fiber cable, or the cylindrical member may be covered to form the optical fiber cable. Further, as described above, the cylindrical member accommodating the tape-shaped optical fiber core wire may be used as a constituent element of the optical fiber cable, and a plurality of these cable elements may be assembled to form an optical fiber cable by applying a jacket. . Such cable elements are also referred to herein as fiber optic cables.

Here, the space factor of the cushioning filler arranged around a plurality of tape-shaped optical fiber cores in the cylindrical space will be defined. The inner diameter of the cylindrical member is 2
r, the total cross-sectional area of the tape-shaped optical fiber core is A, and the total cross-sectional area of the cushioning filler is B, the space factor S (%)
Is represented by S = (B / (πr ² −A)) × 100. Here, as the cushioning filler,
When a fibrous material whose thickness is expressed in denier is used, the total cross-sectional area B (cm ² ) of the cushioning filler is
Is represented by B = (denier number × total number) / 900,000 × specific gravity of cushioning filler).

When the space factor of this cushioning filler and the characteristics of the optical fiber cable were examined, the following facts were found. Since the cushioning filler acts as an elastic buffer layer between the tape-shaped optical fiber core and the inner wall of the cylindrical member, the space factor is increased when the transmission loss at room temperature is taken into consideration. Better. Specifically, 10%
The above is preferable. In the low temperature state, the metal or plastic that is the constituent material of the cylindrical member contracts, and the bending of the tape-shaped optical fiber core wire in the width direction increases the transmission loss. In order to suppress the increase of the transmission loss, it is necessary to set the space factor to 50% or less and sufficiently secure the space in which the tape-shaped optical fiber core wire can move.

As a result of such consideration, the space factor is 10 to 50%.
As described above, by arranging the cushioning filler around the tape-shaped optical fiber core, it is possible to provide an optical fiber cable having good initial loss and loss temperature characteristics.

Incidentally, the tape-shaped optical fiber core wire in the cylindrical space may be loosely accommodated so as to give some meandering.

Hereinafter, a reference example will be described and then an embodiment will be described. FIG. 1 is a sectional view of a first reference example of an optical fiber cable according to the present invention. In the figure, 1 is a tape-shaped optical fiber core wire, 2 is a cushioning filler, and 3 is a cylindrical member. A plurality of tape-shaped optical fiber core wires 1 are laminated, a cushioning filler 2 is arranged around the optical fiber core wires 1, and they are housed in a cylindrical member 3.

In the prototype example based on this reference example, the tape-shaped optical fiber core wire 1 has a thickness of 0.3 mm and a width of 2.1 m.
An eight-fiber tape-shaped optical fiber core wire of m was used, and eight of these were laminated to form an optical fiber cable of 64 fibers. As the cylindrical member 3, a plastic tube having an outer diameter of 6 mm and an inner diameter of 4.8 mm was used. As the cushioning filler 2, a polyester string was used, and various kinds of space factor were produced as trial products within a range of 0 to 80%. A polyester string was vertically attached to the tape-shaped optical fiber core wire 1 and a polyester string was twisted in one direction. The transmission loss and the loss temperature characteristic at a wavelength of 1.55 μm were evaluated for the trial manufactured optical fiber cables having different space factors. Regarding the loss temperature characteristic, the low temperature characteristic was measured, but the measurement condition was −20.
We observed an increase in loss at ℃.

The measurement results are shown in FIG. The transmission loss is 0.25 dB / when the space factor of the cushioning filler is 10% or more.
It is a good level below km. On the other hand, regarding the low-temperature characteristics, the loss increase at -20 ° C was 0.03 dB / km or less, which is the measurement accuracy, in the range where the space factor of the cushioning filler was 50% or less, which was a good characteristic. .

From these results, it was confirmed that the initial transmission loss and the low temperature loss increase characteristics can be improved by setting the space factor of the cushioning filler to 10 to 50%.

Similar trials and evaluations were carried out for other specific examples. That is, outer diameter 5.0 mm, inner diameter 3.8 mm
And an optical fiber cable having an outer diameter of 6.5 mm and an inner diameter of 5.3 mm. As in the case of the outer diameter of 6.0 mm and the inner diameter of 4.8 mm, it was confirmed that the initial transmission loss and the low temperature loss increase characteristics can be improved by setting the space factor of the cushioning filler to 10 to 50%. did it.

In this way, an index for constructing the optical fiber cable with a small diameter can be obtained, which is effective in reducing the manufacturing, transporting, and storing costs.

FIG. 3 is a sectional view of a second reference example of the optical fiber cable of the present invention. In the figure, the same parts as those in FIG. In this reference example,
As the number of cores of the tape-shaped optical fibers to be laminated, different types were combined. In a specific example, three tape-shaped optical fiber cores having 12 cores were laminated in the center, and one tape-shaped optical fiber core having 8 cores and one tape-shaped optical fiber core having 4 cores were laminated above and below the core. The total is 60 hearts.

As described above, also in the optical fiber cable in which the tape-shaped optical fiber cores having different core numbers are combined, the space factor of the cushioning filler 2 is 10 to 50%.
It was confirmed that the initial transmission loss and low temperature loss increase characteristics can be improved by setting to.

FIG. 4 is a sectional view of a third reference example of the optical fiber cable of the present invention. In the figure, the same parts as those in FIG. 4 is a sheath, 5 is a tension member, and 6 is a plastic tube. This reference example is applied to a self-supporting optical fiber cable. The tension member 5 is installed as a support line.

In the optical fiber cable of FIG. 4A, the sheath 4 connecting the cable core portion and the tension member is also used as a cylindrical member of the cable core portion. The sheath 4 is formed by extrusion coating of plastic. The space factor of the cushioning filler 2 is set within the range of 10 to 50% as described above.

In the optical fiber cable shown in FIG. 4B, the cylindrical member has a two-layer structure of a plastic tube 6 and a sheath 4. Also in this reference example, the space factor of the cushioning filler 2 is set within the range of 10 to 50%.

FIG. 5 is a sectional view of a fourth reference example of the optical fiber cable of the present invention. In the figure, the same parts as those in FIG. 7 is a press roll,
8 is a tube and 9 is a tension member. In this reference example, as the cushioning filler 2 arranged around the laminated optical fiber core wires 1, a fibrous or string-like linear body is used, and a press winding 7 is applied thereon. , And stored in a sheath 8 which is a cylindrical member. The inner diameter of the sheath 8 is made larger than the outer diameter of the press winding 7 to provide a space for securing a space factor. The press winding 7 may be loosened to have a space factor. The tube 8 is formed by extruding plastic. The cushioning filler 2 was vertically attached.

In a specific example, the tape-shaped optical fiber core wire is
Eight pieces of 8 cores were laminated. The cushioning filler 2 is
A polyester string was used, and the press-winding 7 was a non-woven tape having a thickness of 0.1 mm. The tube 8 is formed by extrusion molding of polyethylene and has an inner diameter of 4.8 m.
m, the outer diameter is 8.0 mm.

FIG. 6 is a sectional view of the first embodiment of the optical fiber cable of the present invention. In the figure, parts similar to those in FIG. In this embodiment, the cushioning filler 2 is made of the same material as in the fourth reference example, but twisted in one direction around the laminated tape-shaped optical fiber cores.

FIG. 7 is a sectional view of a second embodiment of the optical fiber cable of the present invention. In the figure, parts similar to those in FIG. In this embodiment, the cushioning filler 2 is made of the same material as that of the fourth reference example, but is an SZ twist in which the twist directions alternate around the laminated tape-shaped optical fiber cores. In the specific example, the twisting direction was changed by about 3 to 4 turns.

In the fourth reference example and the trial production examples of the optical fiber cables of the first and second examples, the space factor of the cushioning filler was set to 20%, but in both cases the initial transmission loss and The low temperature loss increase characteristic at -20 ° C was good.

The bending characteristics of the fourth reference example and the prototypes of the optical fiber cables of the first and second examples were evaluated. When bent to a small diameter of 100 mm, no change in transmission characteristics was observed in the first and second examples, but 0.06 dB / in the fourth reference example.
A transmission loss of km has occurred. This is because in the first and second embodiments, the cushioning filler 2 is twisted so that the laminated tape-shaped optical fiber cores can be prevented from protruding from the cushioning filler, and the lateral pressure can be suppressed. It is considered that the increase in transmission loss due to the transmission was difficult to occur. Furthermore, in the first embodiment, the tube 8
When the press-wrapping 7 is removed, the cushioning filler 2 does not enter into the gaps between the laminated tape-shaped optical fiber cores 1 and the like, and the cushioning filler 2 can be easily removed, which is excellent in handling workability. It could be confirmed. Also, the fourth
In the reference example and the second embodiment, when the tube 8 and the press winding 7 are removed at the terminal, the cushioning filler 2 is separated without winding around the laminated tape-shaped optical fiber core wire 1. In particular, the workability is good when the long tape-shaped optical fiber core wire is taken out at the terminal.

In the third embodiment, a water absorbing yarn is used as the cushioning filler 2 in the first embodiment. Similar to the first embodiment, the initial transmission loss and the low temperature loss increase characteristic at −20 ° C. were good, and further, the cable was extended in the horizontal state, and the middle portion was opened to inject water. It has a water length of only 5 m and has good characteristics as an optical fiber cable that is buried outdoors or underground where there is a possibility of flooding.

In each of the above-described embodiments, the tape-shaped optical fiber core wire is formed by straightly laminating,
The laminated tape-shaped optical fiber cores may be twisted at an appropriate pitch and a cushioning filler may be arranged around the twisted optical fibers.
When a twist is applied to the laminated tape-shaped optical fiber cores, the length of the optical fiber becomes uniform when the optical fiber cable is bent, so that excellent performance in transmission characteristics and reliability can be exhibited.

As the cushioning filler, in addition to the above-mentioned polyester strings, polypropylene yarn, cotton fiber bundles, porous fibers, and other linear bodies having an appropriate elasticity and cross-sectional area can be used. Further, when the press winding is applied to the outside of the cushioning filler as in the first and second embodiments, the material of the press winding is not limited to the nonwoven fabric, but a string-shaped material or a tape-shaped material. Can be used.

As the material of the cylindrical member, polyester, nylon, or other suitable plastic material can be used in addition to polyethylene. Also, it is not limited to plastic materials, but stainless steel,
Metallic materials such as aluminum and copper can also be used. Furthermore, the cylindrical member may be made of a plurality of layers of materials selected from these materials. It should be noted that the cylindrical member does not mean a geometrical cylindrical shape, but a third cylindrical member.
As in the reference example described above, a shape in which a connecting portion with a support wire is added is included, and any shape may be used as long as a substantially cylindrical space is formed inside.

[0038]

As is apparent from the above description, according to the present invention, a plurality of tape-shaped optical fiber cores are laminated and a cushioning filler is provided around the cores, and the space factor is 10%.
By arranging at 50% and accommodating in the cylindrical space, it is possible to obtain an optical fiber cable having a good initial transmission loss and a loss increasing characteristic at low temperature. Further, the cushioning filler is formed by laminating the tape-shaped optical fiber cores and then twisting the tape-shaped optical fiber cores in one direction or in the opposite direction. It is possible to obtain an optical fiber cable which can be prevented from protruding and in which an increase in transmission loss due to lateral pressure does not easily occur. It is particularly effective when applied to aerial optical fiber cables and underground optical fiber cables.

[Brief description of drawings]

FIG. 1 is a sectional view of a first reference example of an optical fiber cable according to the present invention.

FIG. 2 is a diagram showing the measurement results of a prototype example.

FIG. 3 is a cross-sectional view of a second reference example of the optical fiber cable of the present invention.

FIG. 4 is a cross-sectional view of a third reference example of the optical fiber cable of the present invention.

FIG. 5 is a cross-sectional view of a fourth reference example of the optical fiber cable of the present invention.

FIG. 6 is a cross-sectional view of the first embodiment of the optical fiber cable of the present invention.

FIG. 7 is a sectional view of a second embodiment of the optical fiber cable of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Tape-shaped optical fiber core wire, 2 ... Cushioning filler, 3 ... Cylindrical member, 4 ... Sheath, 5 ... Tension member, 6 ... Plastic tube, 7 ... Press winding, 8 ... Tube, 9 ... Tension member.

Front page continuation (72) Inventor Yoshiyuki Suetsugu 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Hideyuki Iwata 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nihon Telegraph Telephone Corporation (56) Reference JP-A-11-38292 (JP, A) JP-A-58-150905 (JP, A) JP-A-62-24206 (JP, A) JP-A-2-183208 (JP , A) Actual Kaihei 4-28609 (JP, U) Actual Kaihei 1-157307 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 6/44 361

Claims (4)

(57) [Claims] 1. A structure in which a plurality of tape-shaped optical fiber cores are laminated, a cushioning filler is arranged around the cores, and the cores are housed in a cylindrical space formed of a plastic material containing a tension member. In the optical fiber cable, the space factor of the cushioning filler in the space excluding the tape-shaped optical fiber core in the cylindrical space is 10 to 50%,
An optical fiber cable, wherein the cushioning filler is formed by laminating tape-shaped optical fiber core wires and twisting the same in one direction or while reversing the direction. 2. The optical fiber cable according to claim 1, wherein the plurality of tape-shaped optical fiber core wires are made of one kind or a combination of four kinds or more and 12 kinds or less. 3. The optical fiber cable according to claim 1, wherein the cushioning filler is a yarn or a fiber bundle. 4. The optical fiber cable according to any one of claims 1 to 3, wherein the cushioning filler has a water absorbing property.