JPH07913Y2 - Infiltration detection fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an optical fiber capable of detecting the entry of water, and particularly suppresses an increase in transmission loss in a normal state before water immersion. It was done.

<Prior Art> Optical transmission systems using optical fibers have come to be used not only for land relay transmission but also for submarine relay transmission due to the large capacity, long distance, and high reliability.

When applying such an optical transmission system to undersea relay transmission, special consideration must be given to the fact that the optical cable is vulnerable to water in various points, and therefore the structure of the cable itself must have a reliable water resistance. It is necessary to have it. In other words, when water is immersed in an optical cable containing dissimilar metals, hydrogen gas is generated by electrolysis and diffuses into the optical fiber, causing an increase in absorption loss, or this hydrogen gas chemically reacts with the optical fiber. This is because hydroxyl groups are generated, absorption loss is increased, defect growth on the surface of the optical fiber is accelerated, the life of the optical fiber is shortened, and reliability is reduced.

Therefore, it is necessary to devise so that water does not enter the optical cable as much as possible, but on the contrary, if the optical cable is damaged and water invades, it is possible to detect this inundation location and immediately repair the optical cable. It is desirable to keep it.

Conventionally, a gas maintenance system has been used as a device for detecting water ingress in an optical cable, or JP-A-62-28703 or
1987 International Wire and Cable Symposium Prode
The water detection fiber and the like, which are published on pages 284 to 290 of eding, are known.

In the above-mentioned gas maintenance system, the dry air is pressure-fed to the minute gap formed in the optical cable to detect the leak of the dry air when the optical cable is damaged, thereby grasping the damaged state of the optical cable in a certain section. I am trying.

Further, the water immersion detecting fiber disclosed in Japanese Patent Laid-Open No. 62-28703 can be contracted in the lengthwise direction by contacting the optical fiber core wire 1 with water as shown in FIG. The linear body 2 is wound, and the linear body 2 is brought into contact with water and self-contracts in the lengthwise direction. As a result, tension is applied to the optical fiber core wire 1 to increase transmission loss. The increase of the transmission loss is measured by a backscattered light measuring device (not shown) provided on the side of the optical cable 3 where the signal light is emitted, so that the flooded portion is detected.

Meanwhile, 1987 International Wire and Cable Symposium
The infiltration detection fiber, published from page 284 to page 290 of Prodeeding, shows the schematic structure of the fourth part.
As shown in the figure, the optical fiber core wire 6 is spirally wound around the outer circumference of the water absorption expansion layer 5 covering the tensile strength member 4, and the aramid fiber 7 is further arranged on the outer circumference of the optical fiber core wire 6 at a pitch different from the winding pitch of the optical fiber core wire 6. It is a spirally wound layer. Then, due to the water absorption expansion of the water absorption expansion layer 5, the optical fiber core wire 6 is subjected to compressive stress at the intersection 8 with the aramid fiber 7, thereby increasing the transmission loss of the optical fiber core wire 6, and the above-mentioned water immersion detection. Similar to the fiber, the backscattered light measuring device (not shown) provided on the output end side of the signal light of the optical cable 9 is used to detect and detect the flooded portion.

<Problems to be solved by the invention> In the method of judging the inundation of the optical cable by the gas maintenance system, there is only about 20 km of observable section, and it is necessary to install equipment for pumping dry air at certain intervals. Therefore, there is a drawback that equipment cost and the like increase.

In addition, in the conventional water detection fiber shown in FIG.
It is necessary to wind the linear body 2 around the optical fiber core wire 1 with a relatively high tension so that the optical fiber core wire 1 is tensioned by the contraction in the length direction. Similarly, in the conventional water detection fiber shown in FIG. 4, since the water absorption expansion layer 5 has a soft and soft property, it is necessary to press the optical fiber core wire 6 to the outer peripheral surface of the water absorption expansion layer 5, and thus the aramid By overlapping and winding the fiber 7, the optical fiber core wire 6 is actually pushed and bent at the intersection 8. For this reason, the optical fiber cores 1 and 6 are always subjected to minute bending stresses, respectively, and there is a problem that transmission loss based on these is always included.

<Means for Solving the Problems> The water immersion detection fiber according to the present invention comprises an optical fiber, a strength member wound around the optical fiber, and the strength member and the optical fiber which are integrally coated. It is provided with a water reaction product which causes swelling upon contact with water.

Here, examples of the tensile strength member include a wire material having excellent physical properties such as tensile strength and being chemically stable, such as aramid fiber or nylon braid. Further, as the material constituting the water reactant, those which bring about a shape change such as volume change upon contact with water, such as Sumika Gel SP520 manufactured by Sumitomo Chemical Co., Ltd. or Aqua Keep 10SH manufactured by Iron and Steel Chemical Co., Ltd. Examples thereof include those obtained by binding the powder and granules with a urethane acrylate-based ultraviolet curable resin, a silicone resin, or a binder such as a block polymer of styrene and butadiene dissolved in an organic solvent.

<Function> Since the water reactant is integrally coated around the optical fiber, when the water reactant swells in the radial direction and the longitudinal direction due to the inundation, the optical fiber also expands in the longitudinal direction accordingly. Become. Here, since the tensile strength member has a greater tensile strength than the optical fiber, the tensile strength member does not extend so much in the longitudinal direction. Therefore, the optical fiber is helically wound around the tensile strength member. As a result, it is determined that there is water infiltration by detecting an increase in transmission loss due to the twist of the optical fiber. Since the strength member and the water reactant are integrally coated, relative displacement does not occur at the boundary portion between the strength member and the water reactant due to swelling of the water reactant.

<Embodiment> As shown in FIG. 1 showing a schematic structure of an embodiment of the water immersion detection fiber according to the present invention, an optical fiber 11 for single mode transmission having an outer diameter of 125 μm is coated with a urethane acrylate-based UV curable resin. It is covered with a layer 12 to form an optical fiber core wire 13 having an outer diameter of 0.4 mm. Around the optical fiber core 13, 2,000 denier aramid fiber is used as the strength member 14.
It is spirally loosely wound so that the radius of curvature is 16.7 mm and the pitch is 11.5 mm, and the water reactant 15 is coated thereon,
The optical cable 16 has an outer diameter of 0.8 mm as a whole. The water reactant 15 has a low Young's modulus (for example,
5kg / mm ² ) urethane acrylate UV curable resin 100
For parts by weight, Sumika Gel SP52 manufactured by Sumitomo Chemical Co., Ltd.
25 parts by weight of 0 is kneaded, and the optical fiber core wire 13 and the strength member 14 are integrally embedded in the water reaction body 15.

When both ends of this optical cable 16 are kept under 1 m in water with a tension of 50 g, the water reactant 15 absorbs water and swells, is bent into an optical fiber, and has a wavelength of 1.55 μm. A transmission loss of 0.3 dB was observed. The transmission loss of the optical fiber core wire 13 itself constituting the optical cable 16 for light having a wavelength of 1.55 μm is 0.20 dB / km, and the transmission loss of the optical cable 16 for light having a wavelength of 1.55 μm in dry air. The transmission loss was 0.21 dB / km.

In the present embodiment, the strength member 14 is completely surrounded by the water reaction material 15 so that the strength of the strength member 14 is as loose as possible on the outer peripheral surface of the optical fiber core 13 and a strong force is not applied to the optical fiber. There is no problem in winding the tensile strength member 14 to such an extent that it is lightly contacted with the outer peripheral surface of the optical fiber core wire 13 so as not to apply a minute bending stress to the core wire 13, and so-called SZ winding is also effective. . In the figure, parts having the same functions as those of the previous embodiment are designated by the same reference numerals.

<Effect of the device> According to the water immersion detection fiber of the present invention, the tensile strength member wound around the optical fiber is integrated with the water reaction product, and this water reaction product is joined to the outer peripheral surface of the optical fiber. Since the tensile strength body does not apply a small bending stress to the optical fiber, it is possible to prevent an increase in transmission loss before water immersion.

[Brief description of drawings]

FIG. 1 is a perspective view showing a part of an embodiment of a water immersion detection fiber according to the present invention, and FIGS. 2 and 3 are perspective views showing an example of a conventional water immersion detection fiber. In the figure, reference numeral 11 is an optical fiber, 12 is a coating layer, 13 is an optical fiber core wire, 14 is a strength member, 15 is a water reaction material, and 16 is an optical cable.

Claims (1)

[Scope of utility model registration request] 1. An optical fiber, a tensile strength member wound around the optical fiber, and a water reaction material which swells in contact with water integrally coated on the tensile strength member and the optical fiber. Infiltration detection fiber with.