JPH04222261A - Water-absorbing and waterproof optical fiber cable - Google Patents

Abstract

PURPOSE:To provide a water-absorbing tape whose substrate is dissolved in water to begin the absorption of the water immediately when the tape contacts with the water, and a water proof type optical fiber cable employing the water- absorbing tape to form a pressing wound layer. CONSTITUTION:A water-absorbing tape produced by coating the surface of a water-soluble nonwoven fabric with a highly water-absorbing resin absorbing water at a volume rate of >=10cc per 1g of the resin, and a waterproof optical fiber cable wound with the water-absorbing tape so as to form a pressing wound layer. Even when a water tree is produced in a space between an outer layer and the pressing wound layer, the water tree is extremely short, because the water-soluble nonwoven fabric is immediately dissolved in the water to begin the absorption of the water.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to improvements in water-absorbing tapes and waterproof optical fiber cables, and in particular, water-absorbing tapes that have a high waterproofing effect against water intrusion (water running) between the outer cover and the pressure wrapping layer. and regarding fiber optic cables.

0002

BACKGROUND OF THE INVENTION Conventionally, as cables intended for waterproofing, there have been known gas-maintained cables in which gas is allowed to flow inside the cables and jelly-filled cables in which the cables are filled with jelly. Among these, gas maintenance type cables require gas supply equipment, gas pressure management equipment, etc., and have the disadvantage that maintenance is difficult and expensive. On the other hand, jelly-filled cables have the advantage of being maintenance-free, but have the disadvantage of poor workability because sticky jelly must be removed during connection work.

[0003] In view of the above-mentioned situation, a waterproof optical fiber cable using a water-absorbing tape as a wrapping layer has recently been proposed as a cable that is maintenance-free and has good workability. In this cable, when water enters the cable, the water-absorbing tape swells and acts as a water-stop dam to prevent water from running. Conventionally, water-absorbing tapes have been made by coating a highly water-absorbent resin on a base material made of a nonwoven fabric made of a water-insoluble synthetic resin such as polyester. Since such water-absorbing tapes are hygroscopic, for example, the water-absorbing surface is covered with a water-soluble film as in JP-A-1-225010, or a filler is added to the water-absorbing layer as in JP-A-2-33116. A method has been adopted to improve hygroscopicity. When this water-absorbing tape is used as a wrapping layer for optical fiber cables, superabsorbent resin is usually used as the base material, taking into consideration the workability of extruding the outer sheath and the removal of the outer sheath during connection work. It is coated on one side, and this coated side is wound toward the spacer side, that is, toward the inside of the cable, to form a pressure winding layer.

0004

[Problems to be Solved by the Invention] As mentioned above, in conventional water-absorbing tapes and waterproof optical fiber cables, a super-absorbent resin is coated on one side of a base material made of water-insoluble nonwoven fabric, and this coated surface was wound toward the spacer side to form a pressure winding layer. In such optical fiber cables, if the gap between the outer sheath and the pressure wrap layer is maintained properly, water will not run between them, and when removing the outer sheath during connection work, for example, 40 cm of outer layer several tens of kgf
It can be pulled out with just the right amount of force. However, there are problems in that skill is required to set the extrusion conditions to maintain an appropriate gap between the outer sheath and the pressing layer, and the extrusion conditions also differ for different cable sizes. Therefore, if the gap between the outer sheath and the pressing layer is too large, water will run between them, and since the surface coated with the superabsorbent resin is on the spacer side, water absorption will be slow and the water will run through the gap. A problem arose in that the water distance became significantly longer.

An object of the present invention is to provide a water-absorbing tape and an optical fiber cable that can extremely shorten the water running distance without paying special consideration to extrusion conditions, which were difficult to set in conventional waterproof optical fiber cables. There is.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the water-absorbing tape of the present invention is one in which a water-soluble nonwoven fabric is coated with a super absorbent resin that absorbs 10 cc or more of water per 1 g. The waterproof optical fiber cable of the invention is characterized in that this water-absorbing tape is used as a pressure wrapping layer having a water-absorbing function.

[0007]

[Operation] Since the water-absorbing tape of the present invention has a water-soluble non-woven fabric coated with a highly water-absorbing resin, when the tape comes into contact with water, the non-woven fabric quickly melts and water absorption begins. In addition, in the case of the optical fiber cable of the present invention using this water-absorbing tape as a pressure wrapping layer, even if the surface coated with super absorbent resin is on the spacer side and water runs through the gap between the outer sheath and the pressure wrapping layer. Since the nonwoven fabric serving as the base material quickly unravels and water absorption begins immediately, the water running length can be extremely short.

[0008]

Embodiments Here, embodiments of the present invention will be explained with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of the water-absorbing tape according to the present invention. In Figure 1, the water-absorbing tape (1) is
A rubber binder (3) is applied to one surface of the water-soluble nonwoven fabric (2).
) is coated with super absorbent resin (4). Here, examples of the water-soluble nonwoven fabric include cellulose-based fabrics, but the material is not particularly limited. In addition, as a super absorbent resin, 10
It is necessary to have the property of absorbing more than cc of water, and for example, crosslinked sodium polyacrylate is suitable. The polysodium acrylate crosslinked material has excellent water absorption performance such as water absorption speed and water absorption gel strength, and when it is used in an optical fiber cable, there is no risk of increasing transmission loss. Furthermore, it has good bacterial resistance, and there is no fear that microbial corrosion will generate H2 gas and increase transmission loss in the optical fiber.

FIG. 2 is a sectional view showing an embodiment of a waterproof optical fiber cable using the water-absorbing tape of the present invention as a pressure wrapping layer. In FIG. 2, the waterproof optical fiber cable (5) of the present invention has a spacer (7) coated around a tension member (6) made of Kevlar FRP.
) are arranged in the grooves (8), (8), . . . , and optical fiber tape cores (9), (9), . . . are arranged in the grooves (8), (8), . As (10), the water absorbent tape of the present invention is wound with the surface coated with super absorbent resin facing the spacer side, and a jacket (11) is further applied around the tape. At least one tear string (12) made of Kevlar is longitudinally attached between the outer cover and the pressing layer. In addition, a water-absorbing yarn (13) is inserted into the groove where the optical fiber ribbon is not placed.

Next, in order to confirm the effect of the present invention, FIG.
A waterproof property test was conducted using an optical fiber cable with the structure shown below. In this test, a cable was used in which the outer jacket of the cable was extruded more loosely than usual so that the gap between the outer jacket and the hold-down layer, especially the gap around the tear string, was relatively large. The waterproof property tests were conducted using an L-shaped waterproof test that assumed water running from the cable connection or cut surface, and a T-shaped waterproof test that assumed that the cable jacket was torn and water ran from the side of the cable. The L-shaped waterproof test is performed using a 10 m long cable (3
Artificial seawater (33) is injected from one cross section (32) of 1) at room temperature with a water head length of 1 m, and the water travel length is measured 24 hours later. In addition, in the T-shaped waterproof test, as shown in Figure 4, approximately 2.5 cm of the outer sheath of the middle part of the cable (41) is removed to expose the pressure wrapping layer (42), and then the pressure wrapping layer is placed on top of that part. Artificial seawater (
43) was injected into the cable, and the extent to which the water ran through the cable, which was 1.5 m long on one side, was measured after 24 hours. Regarding the above tests, in addition to the examples according to the present invention, optical fibers were fabricated under the same conditions and with the same structure as the optical fiber cables of this example, except that water-insoluble polyester nonwoven fabric was used as the base material of the water-absorbing tape. A cable was used as a comparative example. The results are shown in Table 1.

[0011]

[Table 1]

[0012] As is clear from the results shown in Table 1, the water-absorbing tape according to the present invention and the optical fiber cable using the same can be used even when there is a relatively large gap between the jacket and the wrapping layer, especially around the tear string. It can be seen that it has extremely excellent waterproof properties, and is especially effective against water running from the side of the cable.

[0013]

Effects of the Invention As detailed above, according to the present invention, water-soluble non-woven fabric is used as the base material of the water-absorbing tape, so that in the optical fiber cable using this tape, the running water is absorbed by the super-absorbent resin coating. Even if it occurs on the opposite side, the base material melts quickly and water absorption begins immediately, making it possible to prevent water running over an extremely short distance.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the water-absorbing tape of the present invention.

FIG. 2 is a sectional view showing an embodiment of an optical fiber cable according to the present invention.

FIG. 3 is an explanatory diagram showing an overview of the L-shaped waterproof test.

FIG. 4 is an explanatory diagram showing an overview of the T-shaped waterproof test.

[Explanation of symbols]

2---Water-soluble nonwoven fabric 3---Rubber binder 4---Super absorbent resin 6------Tension member 7------Spacer 8------Groove 9-----Optical fiber tape core wire 10-------press winding layer 11------ Outer covering 12---Tear string 13-----Water-absorbing yarn

Claims (2)

[Claims] 1. A water-absorbing tape comprising a water-soluble nonwoven fabric coated with a superabsorbent resin that absorbs 10 cc or more of water per gram. 2. A waterproof type in which an optical fiber tape core is arranged in a spiral groove provided on the surface of a spacer, a pressure winding layer having a water absorption function is provided around the outer periphery of the spacer, and an outer jacket is further applied. A waterproof optical fiber cable, characterized in that the pressure wrapping layer having a water absorption function is made of the water absorption tape according to claim 1.