JPS6224206A - Waterproof optical fiber tube unit - Google Patents

Abstract

PURPOSE:To improve the connecting work efficiency and producibility by sticking a water absorbing material to the inner wall of a tube and interposing a waterproof resin or a water absorbing material between optical fiber tapes in the tube. CONSTITUTION:A waterproof resin 2 is filled into the gaps between optical fiber tapes 1a, 1b, 1c, 1d and a water absorbing nonwoven fabric 5 is stuck to the inner wall of a tube of polyethylene 4 lined with an Al tape 3. Since the fabric 5 is easily stuck to the Al tape 3, a tube unit having a water absorbing nonwoven fabric stuck to the inner wall can be easily formed. A waterproof resin having low viscosity selected among conventional waterproof resins for a waterproof cable such as petroleum resins and jellylike compounds is suitable for use as the waterproof resin 2. The water absorbing nonwoven fabric 5 is made of a water absorbing cellulosic material. In the dry state, the fabric 5 is fibrous and nonsticky, but when the fabric 5 absorbs water, it swells and fills the space in the tube.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is a method of manufacturing a plurality of optical fiber tapes in which a plurality of coated optical fibers are arranged in a tape shape and a protective coating is integrally provided around the fibers. The present invention relates to the structure of an optical fiber tube unit that is loosely housed inside the optical fiber tube unit and has a waterproof effect.

(Prior art) Optical fibers have many excellent features.
: Promising as a new transmission medium. However, recent research has revealed that when water enters the inside of an optical cable, a loss peak occurs at a specific wavelength in the transmission characteristics of the optical fiber (Naoya Uchida, et al.;
” Infrared Loss Increase
ina 5ilica 0ptical fiber
due to Chemical ReacLion
of Hydrogen” 9th EC0C, 1983
Year). There is also a report that the mechanical strength of optical fibers deteriorates due to the presence of water (Shigeki Sakaguchi et al., “Fatigue characteristics of quartz glass for optical fibers”, Telecommunications Research Institute, research and study of transmission and mechanical properties. Maintain tree research practical application report,
VOL, 32. Fh12.1983). For these reasons, waterproof optical cables have been developed in which waterproof resin is filled inside the optical cables.

Conventionally, as a structure of a high-density multi-core optical cable, a structure in which optical fiber tapes in which multiple fiber cores are coated in a tape shape is assembled (Y, Koyamada et al, +" A
study on high density option
ical cables with great m
any fibers”30th IWC5, p, 24
4.1981) was proposed. The structural unit of this cable has a structure in which a plurality of optical fiber tapes are loosely housed in a tube and protected. In order to make this type of unit waterproof, it is possible to fill the unit with waterproof resin such as sherry. FIG. 5 is a cross-sectional view showing the structure of a conventional waterproof resin-filled LAP tube unit, with la, lb, and lc.

1d is an optical fiber tape, 2 is a waterproof resin, 3 is an aluminum tape, and 4 is a polyethylene. Optical fiber tape l inside a tube consisting of aluminum tape 3 and polyethylene 4
Waterproof resin 2 to cover a, lb, lc, ld
is filled.

As a waterproof function, it is required that water does not enter the inside of the cable when water pressure is applied to the cross section of the cable. As this evaluation means, for example, the following waterproof test conditions are used.

That is, the length of the optical fiber tube unit is 110 a.
m as a sample, strip off the tube at both ends by 5 am, and then trim the optical fiber tape at this end with scissors to create a sample with a length of 100 cm. Place this sample horizontally and insert it in the longitudinal direction of the tube at room temperature. Initial water head height 120
When water pressure No. 3 is applied, no water is observed to flow out from the other end even 24 hours after the start of measurement.

The structure of the waterproof tube unit shown in Fig. 5 satisfies the conditions of the waterproof test due to the water-stopping effect of the filled resin, but when the unit is placed in a low temperature condition, the filled resin solidifies at low temperatures. This has the disadvantage that lateral pressure is applied to the optical fiber, increasing transmission loss. In addition, when connecting fibers, when connecting optical cables, waterproof resin is applied around the optical fiber tape, so it does not stick to the tape and requires wiping to remove the stickiness. The drawbacks were that the performance deteriorated and construction costs increased.

Furthermore, when manufacturing the unit, it is difficult to mold the tube while filling it with waterproof resin, resulting in lower productivity and higher costs for the optical cable.

(Problems to be Solved by the Invention) An object of the present invention is to provide a waterproof optical fiber tube unit with excellent transmission characteristics, good connection workability and manufacturability, and excellent waterproof function.

(Means for Solving the Problems) The present invention involves attaching a water-absorbing material to the inner wall of the tube of an optical fiber tube unit, and applying a waterproof resin to the gaps between the optical fiber tapes in the tube, or interpose a synthetic material.

Note that the water-absorbing material refers to a chemical fiber that turns into a gel and swells when it absorbs water.

In order to eliminate the drawbacks of conventional waterproof resin-filled tube units, it is conceivable to use water-absorbing fibers that are easy to work with. This fiber is non-stick, so no wiping is necessary. However, when the fibers are inserted into the tube in the same manner as fiber optic tape, micro-bent occurs in the optical fiber within the tube, resulting in increased losses during the cabling process.

Therefore, in the present invention, fibers are attached to the inner surface of the tube. Furthermore, since fibers alone cannot prevent water from passing between the optical fiber tapes, waterproof resin was filled in between the fibers, or a material that absorbs water and swells was interposed between the fibers.

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention, in which 1a+ 1b+ 1c+ ld are optical fiber tapes;
2 is a waterproof resin, 3 is an aluminum tape, 4 is polyethylene, and 5 is a nonwoven fabric made of water-absorbing fibers. The gaps between the optical fiber tapes la, lb, lc, and la are filled with waterproof resin 2, and a water-absorbing nonwoven fabric 5 is glued to the inner wall of a tube made of aluminum tape 3 and polyethylene 4. Note that since the water-absorbing non-woven fabric can be easily attached to aluminum tape, a tube unit with the water-absorbing non-woven fabric attached to the inner wall can be easily molded. As the waterproof resin 2, among those conventionally used for waterproof cables, such as petroleum-based oil materials and sherry-like compounds, those with low viscosity are suitable.

The water-absorbing non-woven fabric 5 is made of a cellulose-based water-absorbing material, and in a dry state it is simply fibrous and does not stick to the hands, but when it absorbs water it swells and fills the inside of the tube.

In order to evaluate the characteristics of the waterproof optical fiber tube unit of the present invention, FIG. 2(a) is used for comparison.

Two types of optical fiber units shown in (b) were prototyped.

FIG. 2(a) is a sectional view showing the structure of a LAP tube unit with a water-absorbing nonwoven fabric, 1a+tb.

lc, ld are optical fiber tapes, 3 is aluminum tape,
4 is polyethylene, and 5 is a water-absorbing nonwoven fabric. A water-absorbing nonwoven fabric 5 is attached to the inner wall of a LAP tube consisting of 3°4, and optical fiber tapes la, lb are placed inside it.
, lc, and ld are loosely housed. Note that nothing was applied between the four optical fiber tapes in the tube unit.

FIG. 2(b) is roughly the same as FIG. 2(a), except that the water absorbent fibers 6 are optical fiber tapes la, lb, lc, l.
It has a structure in which it is inserted into the tube so that it is aligned with d.

As a result of trial production, no change in loss due to manufacturing was observed in the optical fiber tube unit of the present invention (Fig. 1) and the optical fiber tube unit of Fig. 2 (a), but the optical fiber tube unit of the present invention (Fig.
In the optical fiber tube unit b), an increase in optical loss was observed. This is because the water absorbent fibers 6 are in a movable state within the tube, so the optical fiber tapes la, lb, lc,
It is thought that ld was slightly bent, causing an increase in loss. Therefore, this unit has manufacturing problems.

Optical fiber unit of the present invention (Fig. 1) and Fig. 2 (a)
After applying water pressure to the optical fiber unit under the conditions of the waterproof test described above, the unit was disassembled and the internal water running length was measured. Figure 3 shows the results. Looking at this result,
In the LAP tube unit with a structure in which only water-absorbing nonwoven fabric was pasted, the water running length was 100 cm, that is, 3 out of 5 ice cubes had water flowing out from the end of the unit. On the other hand, it can be seen that the LAP tube unit of the present invention, which has a structure in which a waterproof resin is applied between the optical fiber tapes in addition to the water-absorbing nonwoven fabric, has a water running length of 20 cm or less and has an excellent water-stopping effect. The difference between these two has made the following clear.

That is, when water entered the former unit (FIG. 2(a)), the area around the four optical fiber tapes absorbed water and swelled. It is filled with water-absorbing nonwoven fabric and is completely watertight. However, since the swollen nonwoven fabric does not enter the gaps between loosely housed optical fiber tapes, gaps along the axial direction remain.

Therefore, water runs through the gap due to capillary action, and it can be said that a sufficient effect cannot be obtained only with the water-absorbing nonwoven fabric on the inner wall of the tube. On the other hand, in the LAP tube unit of the present invention (FIG. 1), water-stopping measures are taken between the optical fiber tapes using waterproof resin, so water running as described above does not occur.

FIG. 4 is a sectional view showing the structure of another embodiment of the present invention, where la, 1b+ 1c+ ld are optical fiber tapes,
3 is an aluminum tape, 4 is polyethylene, 5 is a water absorbent nonwoven fabric, and 7a, 7b, and 7c are water absorbent nonwoven fabric films. Film-like water-absorbing nonwoven fabrics 7a, 7b, 7 are placed in the gaps of the optical fiber tape 1a+lbt Ic, ld.
c is sandwiched in the longitudinal direction, and these are loosely housed in a LAP tube made of aluminum tape 3 and polyethylene 4 with a water-absorbing nonwoven fabric 5 on the inner wall. With this structure, when water enters, water running between the optical fiber tapes due to capillary action can be sufficiently suppressed by swelling of the water-absorbing nonwoven fabric film between the optical fibers 1.

When the optical fiber tube unit shown in FIG. 4 was subjected to a waterproof property test, good results were obtained similar to the test results of the embodiment of the present invention shown in FIG.

Also, losses are incurred during the manufacturing of this optical fiber unit.
□No change was observed. Compared to the structure in which fibers are inserted throughout the tube as shown in Figure 2 (b), this method uses a film-like water-absorbing material only between the optical fiber tapes, which prevents random bending of the fibers. It is considered that this did not occur.

By using the tube unit with water-absorbing nonwoven fabric shown in FIGS. 1 and 4, the disadvantages of the tube unit shown in FIG. 5, namely increased loss at low temperatures and deterioration of workability and manufacturability, can be improved. Ta.

Note that the present invention is not limited to tube units using LAP, but can also be applied to tube units of the same structure using other materials such as nylon, polyethylene, etc.

(Effects of the Invention) As explained above, compared to conventional waterproof optical fiber tube units, the waterproof optical fiber tube unit of the present invention does not use waterproof resin or uses a small amount of waterproof resin. This has the advantage of being able to suppress an increase in loss at low temperatures due to solidification of the resin. Further, for the same reason, there is an advantage that the optical cable connection workability and unit manufacturability can be improved.

Even with the waterproof optical fiber tube unit of the present invention, which has a structure in which waterproof resin is applied between the optical fiber tapes, it is necessary to wipe off the resin, but the amount is much smaller than in a structure in which the tube is completely filled, so it is easier to do. can be significantly improved. The waterproof properties are good due to water-stopping measures taken between the optical fiber tapes within the unit.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the structure of one embodiment of the present invention, and Figures 2 (a) and (b) are a LAP tube unit with a water-absorbing nonwoven fabric and an optical fiber tape fabricated as a prototype for comparison of characteristics. 3 is a cross-sectional view showing the structure of the attached LAP tube unit; FIG. 3 is a view showing the test results of the waterproof properties of the LAP tube unit with a water-absorbing nonwoven fabric and the LAP tube unit of the present invention; FIG. FIG. 5 is a sectional view showing the structure of a conventional waterproof resin-filled LAP tube unit. LA, LB, LC, LD...Optical fiber tape 2...Waterproof resin 3...Aluminum tape 4.
...Polyethylene 5...Water-absorbing nonwoven fabric 6...
Water-absorbent fiber 7...Water-absorbent nonwoven film

Claims (1)

[Claims] 1. In an optical fiber tube unit in which a plurality of coated optical fibers are arranged adjacently in a tape shape and a plurality of optical fiber tapes formed by applying a plastic coating to the periphery are stacked and loosely housed inside a tube. , a material that absorbs water and swells is pasted on the inner wall of the tube, and the gap between the stacked optical fiber tapes is filled with waterproof resin, or a material that absorbs water and swells is interposed. A waterproof optical fiber tube unit characterized by: