JPH0444723B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical fiber unit mainly used for submarine cables.

[Prior art]

Figure 1 shows a cross section of a conventional optical fiber unit for submarine cables. As shown in FIG. 1, the conventional optical fiber core 5 has a soft primary coating layer 3 around the optical fiber 2 and a hard secondary coating layer 4 which is colored for identification. A plurality of optical fibers are assembled around a center line 1 of a body, etc., and then a buffer layer 6 is integrally coated on the center line 1 and the aggregate of a plurality of optical fibers 5 so that the cross section becomes approximately circular. A hard protective coating layer 7 is provided on the outside of the buffer layer 6.

Generally, optical fiber units for submarine cables are
Used under much harsher conditions than those used under normal conditions. Therefore, in the conventional optical fiber unit shown in FIG. 1, when the outer diameter of the optical fiber core 5 is small, that is, when the primary coating layer 3 and the secondary coating layer 4 are thin, When subjected to lateral pressure, bending, etc., an increase in transmission loss occurs due to rubbing between adjacent optical fiber core wires 5 or rubbing against the center line 1. In order to prevent the increase in the transmission loss, the thickness of the primary coating layer 3 and the secondary coating layer 4 may be increased, but in this case, the outer diameter of the optical fiber core 5 increases, causing the following problems. arise.

For optical fiber units used for submarine cables, there is a strict upper limit on the outer diameter of the unit due to cost and consistency with other cable components, that is, the outer diameter of the protective coating layer 7 in Figure 1. There is a lower limit value for the outer diameter of the wire 1 due to tensile strength, temperature characteristics, or electrical resistance when the center wire 1 is used as a signal line or power supply line. If the outer diameter of the unit has an upper limit and the center line 1 has a lower limit, the space between the center line 1 and the protective coating layer 7 in FIG. 1 will be limited. Therefore, when a predetermined number of optical fiber cores 5 with larger outer diameters are housed in this limited space, the thickness of the buffer layer 6 naturally becomes thinner, and the buffer layer 6 resists lateral pressure, bending, etc. This will reduce the buffering effect and increase the transmission loss. By the way, secondary coating layer 4
The optical fiber core wires 5 having outer diameters of 0.4 mm and 0.6 mm after being subjected to the above are assembled with the center line 1 having an outer diameter of 0.4 mm, and the latter with the center line 1 having an outer diameter of 0.6 mm.
Each of them was coated with the same buffer layer 6 so that its outer diameter was 2.1 mm, and the protective coating layer 7 was provided so that its outer diameter was 2.5 mm. When we tested the lateral pressure resistance and bending resistance characteristics of these two types of optical fiber units, we found that the protective effect of the fiber coating itself was greater in the optical fiber core diameter 0.6 mm than in the outer diameter 0.4 mm fiber. Regardless, as the buffer layer 6 became thinner, the buffering effect of the buffer layer 6 decreased, resulting in a large increase in transmission loss due to lateral pressure and bending of the entire optical fiber unit.

As mentioned above, in the case of conventional optical fiber units for submarine cables, there is a limit to the improvement of transmission characteristics even if the diameter of the optical fiber is made thinner, and conversely, making it thicker leads to an increase in transmission loss. I was holding on to something.

[Purpose of the invention]

In view of the above problems, in the present invention, the diameter of the optical fiber core is increased to prevent an increase in transmission loss due to rubbing between the optical fiber cores or rubbing against the center line. An object of the present invention is to provide an optical fiber unit that does not reduce its buffering effect.

[Structure of the invention]

In order to achieve the above object, the optical fiber unit of the present invention has a center line and a group of optical fibers gathered around the center line.
Starting from the inside of the optical fiber, apply a soft primary optical coating layer,
a plurality of coated optical fibers having a secondary coating layer harder than the primary coating layer and having a coating layer softer than the secondary coating layer as the outermost layer; and an outermost layer of the coated optical fibers. a buffer layer made of the same material as the soft coating layer and integrally covering the aggregate of the plurality of optical fiber core wires and the center line with a substantially circular cross section; and a protective coating layer provided outside the buffer layer. It has the following.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a cross-sectional view of an embodiment of the optical fiber core according to the present invention. As shown in FIG. 2, a soft primary coating layer 3 and a hard secondary coating layer 4 are applied to the optical fiber 2 from the inside, and the outermost layer is a soft tertiary coating layer 10.
The optical fiber core wire 11 is obtained by coating the optical fiber. FIG. 3 shows an embodiment of an optical fiber unit according to the present invention using the optical fiber core 11 described above. As shown in FIG. 3, the optical fiber unit of the present invention has a plurality of optical fiber core wires 11 arranged around a center line 1, which is a tensile strength body such as a steel wire, or a signal line or a power supply line. A buffer layer 6 is provided to integrally cover the center line 1 and the aggregate of the plurality of optical fiber cores 11, and a hard protective coating 7 is provided on the outside of the buffer layer 6. . Here, the buffer layer 6 is formed of the same material as the tertiary coating layer 10, which is the outermost layer of the optical fiber core 11.

In such an optical fiber unit, the outer diameter of the optical fiber core 11 is thicker, that is, the thickness of the protective coating layer is larger than that of the conventional optical fiber core 5 shown in FIG.
Since the thickness is increased by the thickness of the soft tertiary coating layer 10, which is the outermost layer, it is possible to prevent an increase in transmission loss caused by rubbing between the optical fiber core wires 11 due to lateral pressure or bending, or rubbing against the center wire 1. In addition, since the soft tertiary coating layer 10, which is the outermost layer, works together with the buffer layer 6 to exhibit a buffering effect, the outer diameter of the optical fiber 11 is increased by 10 minutes of the soft tertiary coating layer, which is the outermost layer. Buffer layer 6 due to summer
Although the thickness of the buffer becomes thinner, the buffering effect does not decrease and the transmission loss does not increase. In addition, since the material of the soft tertiary coating layer 10, which is the outermost layer, and the material of the buffer layer 6 are the same, the two are almost integrated, making it easier to exert the buffering effect.

Furthermore, the soft tertiary coating layer 10 which is the outermost layer
Coloring for fiber identification has the following effects.

Since optical fiber units for submarine cables are generally used in harsh environments, they are required to have higher reliability than those used under normal conditions. Therefore, in order to ensure this reliability, a screening test, which is a type of sieving test, is performed using a tension larger than usual. In the case of the optical fiber core 5 of the conventional optical fiber unit shown in FIG. 1, the hard secondary coating layer 4 is colored, and the screening test described above is carried out immediately after the hard secondary coating layer 4 is applied. was. This is because immediately after the soft primary coating layer 3 is applied, the coating is soft and the cross section may be deformed in the screening test. However, when a screening test was performed after applying the colored hard secondary coating layer 4, the amount of optical fiber core 5 that was screened out was different for each color, so it was natural that the optical fiber cores for each color were good products. Variations occur in the amount of 5. In this case, since there is no flexibility between the different color optical fiber cores 5, some colors may be lacking or some may be surplus. As a result, anything that is left over is wasted, and even if there is only a small amount of something that is missing, it has to be remade, which disrupts the manufacturing process and significantly impairs production efficiency. However, in the optical fiber core wire 11 according to the present invention, if the outermost soft tertiary coating layer 10 is colored and the hard secondary coating layer 4 is left uncolored, the hard secondary coating layer 4 can be applied as in the conventional case. Immediately after, a screening test is performed, and only those that pass the test are coated with the next outermost colored soft tertiary coating layer 10, and the amount of each colored optical fiber core 11 can be controlled to avoid wastage or shortage. It is possible to prevent a decrease in production efficiency due to

Here, a specific example will be shown.

<Example> Optical fiber: outer diameter 0.125 mm Primary coating layer: outer diameter 0.25 mm, silicone acrylate (Young's modulus 0.3 Kg/mm ² ) Secondary coating layer: outer diameter 0.4 mm, epoxy acrylate (Young's modulus 40 Kg/mm ² ) Tertiary coating layer: outer diameter 0.6 mm, urethane acrylate (Young's modulus 1 Kg/mm ² ) Center line: outer diameter 0.6 mm, steel wire Six optical fiber core wires are gathered around one center line, buffer layer : The above aggregate is integrally coated with outer diameter 2.1 mm, urethane acrylate (Young's modulus 0.3 Kg/mm ² ) Protective coating layer: outer diameter 2.5 mm, epoxy acrylate (Young's modulus 40 Kg/mm ² ) Result: Tertiary coating layer Transmission loss was significantly reduced compared to the conventional one.

〔Effect of the invention〕

As described above, according to the present invention, by increasing the optical fiber core diameter, it is possible to prevent an increase in transmission loss due to rubbing between the optical fiber core wires or rubbing against the center wire, and by increasing the core wire diameter. Nevertheless, the buffering effect of the buffer layer is not impaired.
Furthermore, since the outermost layer of the optical fiber core and the buffer layer are formed of the same material, they are almost integrated, so that the buffering effect is more easily exerted. In other words, it is possible to obtain an optical fiber unit with less increase in transmission loss due to lateral pressure or bending. In addition,
If the outermost soft coating layer is colored for identification, it is possible to prevent wastage of the optical fiber core and improve production efficiency.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional optical fiber unit for submarine cables, FIG. 2 is a cross-sectional view of an embodiment of an optical fiber core according to the present invention, and FIG. 3 is a cross-sectional view of an optical fiber unit of the present invention. FIG. 3 is a cross-sectional view showing an example. DESCRIPTION OF SYMBOLS 1... Center line, 2... Optical fiber, 3... Soft primary coating layer, 4... Hard secondary coating layer, 6... Buffer layer, 10
... Soft tertiary coating layer, 11... Optical fiber core wire.

Claims (1)

[Claims] 1. An optical fiber having a center line, a soft primary coating layer gathered around the center line in order from the inside, and a secondary coating layer harder than the primary coating layer; A plurality of coated optical fibers each having an outer layer having a coating layer softer than the secondary coating layer, and a plurality of coated optical fibers made of the same material as the soft coating layer that is the outermost layer of the coated optical fiber. An optical fiber unit comprising: a buffer layer that integrally covers a collection of center lines with a substantially circular cross section; and a protective coating layer provided outside the buffer layer. 2. Claim 1, wherein the outermost coating layer of the optical fiber core wire is colored.
The optical fiber unit described in Section 1.