JPS6247008A - Optical fiber unit - Google Patents

Abstract

PURPOSE:To lessen the microbending of the title unit, and to reduce the increase of the transmission loss of the title unit, even if a temperature and a lateral pressure change by using an UV curable silicon as a filling layers, and by specifying the Young's modulus of the 1st and 2nd fillers respectively. CONSTITUTION:The UV curable silicon 3 is filled the space of the optical fibers 2a-2f. The 1st filling layer 4 of composed of an UV curable urethane resin filled with the UV curable silicon 3 having a low Young's modulus of, for example, 7kg/mm<2> which covers an outer surface of the cable conductor assemble of the optical fiber. The 2nd filling layer 5 is composed of an UV curable epoxy resin having a high Young's modulus of for example, 40kg/mm<2> which covers as mentioned above. The nylon layer which usually covers an optical fiber as the 2nd coatings for improving the peeling property of between the UV curable urethane resin and the optical fiber may be omitted. If the UV curable urethane resin having the high Young's modulus of 30-70kg/mm<2> is used as the 2nd filling layer 5, the increase of the transmission loss unit against the temp. and the lateral pressure of the title unit are greatly reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical fiber unit 7), and particularly to an optical fiber unit useful as a communication line of a submarine optical cable.

[Conventional technology]

Submarine optical cables, which are used as a means of long-distance communication, usually have an optical fiber/< unit, which is a unit made of multiple optical fibers, arranged in the center in order to transmit a large amount of information.

FIG. 7(a) shows an example of the cross-sectional structure of such a conventional optical fiber unit, where 10 is a central tensile strength wire (steel wire) placed in the center.

It is coated with an ultraviolet (UV) curable urethane resin layer 10a. 20a, 20b, 20c.

20d, 20e, and 20f are optical fibers twisted around the outer circumference of the In4 wire 10, and these optical fibers 20h to 20
Each f has an optical fiber /'/core wire 2 as a protection 1 active coating.
A UV-cured urethane resin layer 22° and a UV-cured epoxy resin layer 23. It is then coated with a nylon layer 24. The gaps between the optical fibers 20a to 20f are filled with a unit filler material 30 made of UV-curable urethane resin.

Note that the inner layer side 30a of the unit filler 30 is made of a UV-cured urethane resin having a low Young's modulus, and the outer peripheral side 30b is made of a UV-curable urethane resin having a high Young's modulus.

[Problem that the invention seeks to solve]

In such an optical fiber unit, the optical fibers 20a to 20f are protected by the three layers of protective coating, and the entire optical fiber unit is protected by the filler material 30, but it also has the following drawbacks. It will be done.

(1) In the manufacturing process of optical fibers 20a to 20f,
Coating with thermosetting resin or UV curing resin and coating with nylon are separate processes, which increases costs.
The diameter of f becomes large, and as a result, the diameter of the entire unit also becomes large, making it unsuitable for high-density assembly.

(2) When the optical fibers 20a to 20f are twisted on the outer surface of the central tensile strength wire 10 coated with UV-curable urethane resin, the tensile strength wire may be coated due to the influence of heat during the twisting or post-processing. The UV-cured urethane resin used in the tensile strength wire becomes soft, and as a result, the optical fibers twisted onto the outer surface of the tensile strength wire tend to bite, causing waviness in the optical fiber core, and as a result, increases in loss due to microbending are likely to occur.

Therefore, as a solution to the above-mentioned problems (1) and (2), a secondary coating of optical fibers 20a to 20f twisted on the outer surface of the central tensile strength line 10 as shown in FIG. 7(b) is used. Outer diameter 0.4ma+ without the nylon layer 24
A structure in which optical fibers are twisted together has been proposed, but
UV curing urethane resin or UV curing epoxy resin which is the primary coating layer of the optical fiber and UV filling the voids.
Since the cured urethane resin adheres, there is a problem in that the optical fibers cannot be easily separated when the unit is disassembled for terminal work or the like.

The present invention was made in order to solve these problems, and was made for the purpose of providing an optical fiber unit with low transmission loss and easy terminal work.

〔Example〕

FIG. 1 shows the cross-sectional structure of an optical fiber unit showing an embodiment of the present invention, where ■ is a center tensile strength wire whose surface is plated with lead, such as a steel wire, and 2a to 2f are the center tensile wires. An optical fiber wound around the outside of the tensile strength line l,
As mentioned above, it is coated with a UV-curable urethane resin or a UV-curable epoxy resin.

Reference numeral 3 indicates UV-curable silicon filled in the voids of the optical fibers 2a to 2f, and 4 indicates UV-curable silicon 3.
5 is the same <UV
High Young's modulus made of cured epoxy resin, e.g. 40 K
The second solid layer consists of g/mm2.

The optical fiber unit of the present invention is different from the conventional optical fiber (Fig. 7) in that it has a UV-curable urethane resin coated as a unit filler and an optical fiber! [The nylon layer 24, which was applied as a secondary coating to the optical fiber to improve properties, is omitted.

Therefore, the outer diameter of the optical fibers 2a to 2f is approximately Q, 4 m.
m, the outer diameter of the central tensile strength line 1 is as small as 0.45 m111.

The adhesion between the central tensile strength line 1 and the optical fibers 2a to 2f is UV
Although it depends on the hardening type silicone 3, the magnitude of this adhesion is 25 kg/ff1ffi when the central tensile strength wire 1 is galvanized, according to experiments, and when the central tensile strength wire 10 is coated with the conventional central tensile strength wire 10. There is almost no difference from the conventional UV-curable urethane resin, and there is no risk of misalignment between the central tensile strength line 1 and the optical fibers 2a to 2f.

Incidentally, it was confirmed through experiments that the adhesion force was reduced to 9 g/++m in the case where the outer surface of the central tensile strength line l was plated with copper, and was 17 g/mm in the case without plating.

In addition, if the UV-curable resin used as a filler is silicone, it has good releasability from the UV-curable urethane resin or U-cured epoxy resin, which is the primary coating layer of the optical fiber, so the light When the fibers 2a to 2f are pulled out, it becomes easy to separate them one by one, and the terminal work becomes easier.

Further, as the first solid layer 4, a UV-curable urethane resin with a low Young's modulus of 1 to 10 kg/111Q+2 is used, and as the second solid layer 5, a UV-curable urethane resin with a high Young's modulus is used.
30-70 kg/m of hardening urethane resin
When +a2 is used, the increase in transmission loss with respect to temperature and lateral pressure is the smallest, as shown in the experimental data described later.

Generally, the first UV-cured resin with a low Young's modulus relieves the shrinkage stress due to temperature changes, and the second
This UV-cured resin with a high Young's modulus reduces optical fiber transmission loss due to lateral pressure.

Figures 2 (a) and (b) are the first. and a second enriched layer 4,
This is a graph showing the tendency of the maximum transmission loss f+l'i when temperature and lateral pressure are changed with respect to Young's modulus E (Kg/mm2) of
60°), and dotted line B shows the tendency for transmission loss to increase due to changes in lateral pressure when the temperature is kept constant. As can be understood from this figure, the first solid layer 4 and the second solid layer 5 have a Young's modulus E of 1 to 1 OKg/mm2. and 30-70
There is almost no increase in transmission loss between Kg/mm2.

FIGS. 3(a) and 3(b) are the same as those shown in FIG. Second enrichment layer 4,
The ratio P of the outer diameter dimension Di, D2 of 5 and the twisted diameter Do of the core wire
1 and P2 indicate the tendency for transmission loss to increase due to temperature characteristics and changes in lateral pressure, where solid line A indicates a tendency for transmission loss to increase due to temperature change, and dotted line B indicates a tendency for transmission loss to increase with changes in lateral pressure. It shows.

From this figure, it can be seen that the increasing trend of transmission loss is the first. Although it is understood that it also depends on the outer diameter dimensions of the second solid layers 4 and 5, in the case of the first solid layer 4, D+ /Do is 1.2 to 1.
5, the increase in transmission loss is the smallest, and the second
It has been found that the increase in transmission loss is reduced when the dimension of the solid layer 5 is in the range of D2/Do from 1.5 to 2.

In addition, the data in FIGS. 3(a) and (b) indicate that the Young's modulus E of the solid layer 4 is 7 Kg/mm2, and the Young's modulus E of the solid layer 5 is 7 Kg/mm2.
40 Kg/mm2.

FIG. 4 shows an optical fiber unit 7 showing another embodiment of the present invention.
), and as in Figure 1, l is a galvanized central tensile strength wire with an outer diameter of 1.2 mm, and 2a to 2 are 12 optical fibers twisted together, as described above. U
It is coated with a V-curing resin and has an outer diameter of approximately 0.4 mm. 3 is UV curing silicone, 4.5 has a Young's modulus of 7 Kg/mm2 and 40 Kg/m2, respectively.
They are solid layers of UV-curable resin having a diameter of 2.6 mm and 3.2 mm, respectively.

The lateral pressure to be applied for the above test is as shown in Fig. 5. The optical fiber unit (P) is folded back with a 100 mm base plate Sl-, and a light emitting source LED and a power meter PM are connected to both ends of the optical fiber unit (1-). One weight W of a 20 kg stent is added from L of plate A in a range of 0 to 200 kg to determine the change in transmission loss.

In addition, the temperature 4ν characteristic is the change in transmission loss when the optical fiber unit P is stored in a thermostatic chamber and the temperature is changed from ~30 to 60 degrees as shown in Figure 6. , the increase in transmission loss at this time is extremely small as shown by the dashed line.

〔Effect of the invention〕

As explained above, the optical fiber unit of the present invention uses UV-curable silicone as a filler, and the Young's modulus of the first solid layer is 1 to L OKg/mm.
2. Young's modulus of the second solid layer is 20 to 70 kg/
By setting it to mm2, it is possible to exhibit the effect that there is little microbending and that there is little increase in transmission loss due to fluctuations in temperature and lateral pressure. In addition, since it becomes easier to separate the collected optical fibers, it becomes easier to carry out the unloading work at the terminal, and since there is less influence of lateral pressure, it has the effect of improving the bending strength when used in submarine optical cables.

[Brief explanation of the drawing]

FIG. 1 shows an optical fiber unit 7) showing an embodiment of the present invention.
2(a) and (b) are graphs showing the Young's modulus of the first and second solid layers and the increasing tendency of transmission loss corresponding to temperature changes and lateral pressure changes, and FIG. 3(a) , (b) is the ratio PI of the diameter of the solid layer and the diameter of the four twisted optical fibers.
, P2, and a graph showing an increasing tendency of transmission loss corresponding to changes in temperature and lateral pressure. FIG. 4 is a cross-sectional view of a fiber unit showing another embodiment of the present invention. FIG. A schematic diagram of the experiment, FIG. 6 is a graph showing the heat cycle of temperature change, and FIG. 7(a). (b) is a sectional view showing a conventional optical fiber unit. In the figure, 1 is the center tensile strength line, 20a to 209. is an optical fiber, 3 is a UV-curable silicone, and 4.5 is the first one. The second enrichment layer is shown. t+m (G) 2nd p, -D+/D. (Q) 3rd (b) Figure P2 = 02/D. (b) Figure S' Rod 57 No. 6 g (b) Figure 7 Hand Itouri Neichi 11 %N> (Voluntary) Showa 60
October 18,

Claims (2)

[Claims] (1) A plurality of optical fibers coated with an ultraviolet curable resin are directly twisted on the outer surface of a central tensile strength wire that is galvanized, and the central tensile strength wire and the plurality of optical fibers are The voids and the voids between the plurality of optical fibers are filled with ultraviolet curable silicone resin to form an optical fiber wire assembly with a circular cross section, and the outer periphery of the optical fiber wire assembly has a Young's modulus of 1 to 1. 10Kg/mm
An optical fiber unit characterized in that it is coated with an ultraviolet curable resin as the first and second solid layers of 30 to 70 kg/mm2. (2) the outer diameters of the first and second solid layers are respectively 1.2 to 1.5 times the outer diameter of the optical fiber line assembly;
and 1.5 to 2.0 times, the optical fiber unit according to claim (1).