JPH05249354A - Running water preventive type optical fiber cable - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a stable running prevention property for a long period of time without adversely affecting the optical fiber. A structure in which a plurality of optical fibers are arranged on the outer circumference of a tension member, a tape winding layer is formed on the outer circumference of the optical fiber, and a sheath is coated on the outer side of the optical fibers, wherein the tape winding layer has water. The polyacrylic acid powder uniformly absorbs the polyacrylic acid powder, which gels by absorbing the water and exudes from the tape winding layer to seal the peripheral voids.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water running prevention type optical fiber cable.

[0002]

2. Description of the Related Art In order to prevent water transmission of a metal general communication cable, a method of continuously or intermittently filling a cable with a petram jelly, a polybutene mixture, and a powder that swells in water is used. ..

[0003]

A similar method is being adopted in an optical fiber cable which has been put into practical use in recent years and has a short history, but the following problem occurs in the optical fiber cable.

(1) In the case of a jelly mixture, the jelly is generally injected from above the aggregate at high temperature and high pressure, but in this case, high temperature and high pressure are also applied to the optical fiber, which causes microbending or loss of the fiber. It is difficult to avoid the increase. Further, the jelly constrains the optical fiber in the longitudinal direction of the cable, but it is difficult to control the constrained condition as a whole.

(2) In the case of powder, a method of blowing the powder into the cable at the time of assembly is generally adopted, but it is difficult to make the powder uniformly exist in the cable for a long period of time. That is, the powder may move or be unevenly distributed in the cable due to the inclination or vibration of the cable, and it may not be useful when necessary.

In view of such a situation, the present invention has an object to provide an optical fiber cable having a stable running-preventing characteristic for a long period of time without adversely affecting the optical fiber.

[0007]

DISCLOSURE OF THE INVENTION The gist of the present invention is to provide a polyacrylic acid which acts on a tape winding layer to form a gel by absorbing water and to exude from the tape winding layer to seal a peripheral void. The powder is contained uniformly.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a running-prevention type optical fiber cable of the present invention will be described below with reference to the drawings.

1 is a tension member such as a steel wire,
The outer periphery is covered with a buffer layer 7 (for example, polyethylene). Four optical fibers 2 and intervening cords 3 are arranged outside the buffer layer 7, and the intervening cords 3 are appropriately arranged in the gap between the optical fibers 2.

A tape winding layer 4 is formed on the outer circumferences of the optical fiber 2 and the interposing cord 3, an aluminum-polyethylene laminate tape 5 is wound on the outside of the tape winding layer 4, and a sheath 6 is covered on the outside thereof. ing.

The tape winding layer 4 is a polyacrylic acid powder, which is a substance that acts as a gel by absorbing water and exudes to the periphery to seal a gap in the surrounding sheath 6 and prevent water running. Are uniformly contained and formed.

The intervening cord 3 plays a role of a spacer for keeping the optical fiber 2 in a fixed position for performing cabling and a cushion for preventing stress on the optical fiber 2 when water does not enter. Fulfill The tape winding layer 4 functions as a cushion as well as a heat insulating function.

When water penetrates into the cable, the substance contained in the tape winding layer 4 becomes a gel in a very short time and exudes from the tape winding layer 4 into the cable. It fills the remaining gaps and its viscosity prevents running water.

The tape is formed of a material that allows the above substance in gel form to pass therethrough.

[0015]

EFFECTS OF THE INVENTION Since the running-prevention type optical fiber cable of the present invention is constructed as described above, it is easy to manufacture without the step of injecting powder or jelly. And the substance that absorbs water and prevents running water is contained in the tape itself of the tape winding layer, and through this, the distribution in the cable is always kept uniform, so the powder is not It does not move or become unevenly distributed in the sheath as in the case of filling the same, and it does not cause microbending loss in the optical fiber by applying high temperature and high pressure as in the case of injecting jelly. Further, unlike the case of using the conventional powder-containing tape, the optical fiber is not pressed by swelling to cause microbending.

Further, according to the present invention, since a polyacrylic acid powder having a high water absorption ratio and a high water absorption coefficient and thermal stability of viscosity is adopted as a substance which absorbs water to form a gel, The running length of water due to water ingress into the fiber cable can be kept short, and the polyacrylic acid powder is a substance that is not decomposed by microorganisms contained in the water that has infiltrated into the optical fiber cable. It has an excellent effect that the waterproof effect can be exerted for a long period of time without adversely affecting.

That is, when considering the environment in which the cable is laid, it is the actual situation that the water actually infiltrating into the optical fiber cable is not pure water but innumerable microorganisms such as bacteria. If the substance that absorbs water and turns into a gel is a natural polymer such as carboxymethyl cellulose, the substance will start to be decomposed by microorganisms, and 2-3 days after flooding, the substance in the optical fiber cable Oxygen and nitrogen are reduced and hydrogen is generated. When hydrogen is generated in the cable, hydrogen diffuses inside the optical fiber core wire, causing optical absorption loss of hydrogen and optical absorption loss of the OH group formed by the combination of hydrogen and the dopant in the optical fiber. Although the transmission characteristics of the optical fiber are significantly deteriorated, according to the present invention, since the substance that becomes a gel by absorbing water is polyacrylic acid powder, hydrogen is not decomposed by microorganisms and hydrogen is not decomposed. Since it does not occur, it is possible to prevent a remarkable deterioration of the transmission characteristics of the optical fiber.

Further, the natural polymer which has become a gel by absorbing water due to water immersion into the optical fiber cable rapidly loses its water retention property because its viscosity rapidly decreases due to the decomposition of microorganisms. The function of the water stop dam that had been done is deteriorated, and the inundation progresses with the passage of time to extend the running water length, but according to the present invention,
Since the substance that absorbs water and turns into a gel is polyacrylic acid powder, it is not decomposed by microorganisms and retains water retention, so that the running water length can be maintained for a long period of time.

As described above, according to the present invention, there is an excellent effect that a stable running-preventing property can be obtained for a long period of time without adversely affecting the optical fiber.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a running-prevention type optical fiber cable of the present invention.

[Explanation of symbols]

 1 Tension member 2 Optical fiber 3 Intervening string 4 Tape winding layer 6 Sheath 7 Buffer layer

Claims (1)

[Claims] 1. A tape winding layer comprising a plurality of optical fibers arranged on the outer circumference of a tension member, a tape winding layer formed on the outer circumference of the optical fiber, and a sheath covering the outside of the tape winding layer. , A water-prevention type optical fiber, characterized in that it uniformly contains polyacrylic acid powder that gels by absorbing water and exudes from the tape winding layer to seal the surrounding voids. cable.