JPH02162307A - Waterproof type optical fiber cable - Google Patents

Abstract

PURPOSE:To stop the water infiltering the inside of the cable at an extremely short distance by providing highly water absorption layers on the outer peripheries of coated optical fibers and on the outer periphery of a central tension member as well. CONSTITUTION:A highly water absorption resin having 200 times water absorptivity is extruded and applied to 150mum thickness on the outer periphery thin wire 1 of 0.6mm diameter consisting of fiber reinforced plastic (FRP) and thereafter 6, pieces of the coated optical fibers 3 of 0.9mm outside diameter formed by successively provid ing the primary covering of a silicone resin and the secondary covering of a polyamide resin on the bare quartz optical fiber of a G1 type having 50mum core diameter and 125mum clad diameter are disposed around the thin FRP wire 1 having the above- mentioned coating layer 2 while the fibers are twisted together. A tape consisting of sodium polyacrylate which is the water absorption resin is lap wound around the coated optical fibers 3 to form a retaining winding layer 4 and further, a polyethylene jacket 5 is extrusion-coated thereon to obtain the optical fiber cable having 7.1mm outside diameter. The water is stopped at the extremely short distance in this way and is substantially prevented from running off in the longitudinal direction when the water infilters the inside of the cable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to an optical fiber cable that is prevented from entering water from the outside and from running water along its length.

(Prior Art) Generally, when water enters an optical fiber cable, microvent loss may occur due to freezing of the water. For this reason, optical two-eye cables have traditionally been filled with high-pressure gas in order to prevent water from entering the cable and running along its length. A gas maintenance method is used to prevent water from entering by ejecting gas from there. However, this method has the disadvantage of being costly because it requires a system for constantly monitoring gas pressure and gas supply equipment.

It is also equipped with an intervening pair (metal core wire) that transmits signals from a pressure sensor that detects a drop in gas pressure, and is equipped with an outer sheath made of polyethylene-laminated aluminum (LAP) to withstand gas pressure. , metal materials are used for the cable construction materials, and therefore their use is restricted in areas with strong induction, such as near high-voltage power lines or electric railways, as high voltages are induced in the metal materials, and they cannot be used easily from power lines or lightning. Another problem was that the feature of optical fiber cables, which is not affected by electromagnetic induction, was not fully utilized.

Furthermore, cables have been known in which the gaps within the cable are filled with a jelly-like mixture to prevent water from entering or running, but with this type of cable, it is difficult to fill the jelly-like mixture, and the mixture is Since it is viscous and tends to adhere to other parts, there is a problem that the workability of cable manufacturing, inspection, connection, etc. is extremely poor.

Furthermore, recently, waterproof optical fiber cables have been developed that use tape-like or yarn-like highly water-absorbent materials as the presser wrap or intervening material. In this case, there was a problem in that water running several tens of centimeters was seen around the tension member where no water absorbing material was placed.

(Problem to be solved by the invention) As described above, in the conventional gas pressure utilization method, it is necessary to maintain a system and gas supply equipment to constantly monitor the gas pressure, which is costly and requires the use of metal as the constituent material. There is a problem of induction disturbance because it requires the use of a sherry filling method, and the workability of the sherry filling method is extremely poor.Furthermore, the method of using highly water-absorbent materials in the form of tape or yarn is even less effective. The problem was that it was insufficient.

The present invention was made to solve such conventional problems, and even if water were to flood through the outer sheath, almost no water would run in the length direction, and since it has a non-metallic structure, there are no restrictions on where it can be used. The purpose is to provide a waterproof optical fiber cable with good workability.

[Structure of the Invention] (Means for Solving the Problems) The waterproof optical fiber cable of the present invention includes a coating layer of super absorbent resin provided around the outer periphery of a non-metal tension member, and a plurality of optical fiber core wires arranged around the coating layer. In addition, the present invention is characterized in that a pressing layer of highly water-absorbent tape and a plastic jacket are provided in this order on the outside of the optical fiber core.

As the non-metallic tension member used in the present invention, a thin fiber reinforced plastic (FRP) wire, a rod made of hard plastic, or a bundle of Kevlar (trade name of polyaramid fiber manufactured by DuPont, USA) can be used. In particular, a thin wire made of FRP is suitable.

In the present invention, the superabsorbent resin coated on the outer periphery of the tension member is a polymer that absorbs several tens to hundreds of times its own weight of water and swells into a gel to have a water-retaining function.

All known superabsorbent resins can be used, but polyacrylate-based resins such as sodium polyacrylate, etc. have a high water absorption rate and are stable against heat and microbial corrosion. Isovar-based, vinyl acetate-
It is desirable to use a synthetic polymer-based water absorbing resin such as an acrylic acid copolymer system.

In the present invention, it is desirable that the superabsorbent resin layer be provided on the non-metal tension member by extrusion coating. When the superabsorbent resin layer is formed by an extrusion coating method, the forming operation is easy and a layer having a cushioning function for the outer optical fiber core can be obtained.

Furthermore, in the present invention, the superabsorbent tape to be wrapped around the outer periphery of the optical fiber is made by adhering the powder of the aforementioned synthetic polymer-based superabsorbent resin to the surface of the base tape or yarn using an appropriate binder. However, from the viewpoint of water absorption rate and water absorption rate, it is preferable to use a tape to which superabsorbent resin powder is attached. It is desirable to do so.

In addition, to form a pressing layer of these tapes, it is possible to apply them vertically, but it is better to wrap a part of the tape in the width direction, in particular, because it is more densely wound. Are suitable.

(Function) In the optical fiber cable of the present invention, the highly water-absorbent tape wound around the outer circumference of the optical fiber core instantly absorbs water and swells as soon as water enters, and gels to form a water-stop dam. , the water running distance in the length direction is extremely short.

In addition, a coating layer of super absorbent resin is provided around the outer circumference of the tension member, and this layer also absorbs water and expands to fill the gaps in the cable, so water running along the outer circumference of the tension member is completely prevented. Prevented.

Furthermore, when a synthetic polymer-based superabsorbent resin is used as the superabsorbent material constituting these tapes and coating layers, it is not only thermally stable but also decomposed by microorganisms and released into the atmosphere such as hydrogen gas. will not occur. Therefore, good transmission characteristics and water-stopping properties are maintained over a long period of time.

Furthermore, it is easy to manufacture and connect, and does not require special equipment for management or repair.

(Example) Examples of the present invention will be described below.

As shown in the drawings, a thin wire 1 made of FRP with a diameter of 0.6 mm is coated with Plaue Sole 1-0, which has a water absorption rate of 200 times.
2BOH (trade name of super absorbent resin manufactured by Mitsubishi Yuka Co., Ltd.)
After extrusion coating to a thickness of 150 μm, a primary coating of silicone resin and a secondary coating of polyamide resin are applied around the FRP thin wire having the coating layer 2 on the Gl type quartz optical fiber bare wire with a core diameter of 50 μm and a cladding diameter of 125 μm. Optical fiber core wire 3 with an outer diameter of 0.9n+m, which is formed by sequentially providing a coating and a coating.
The six strands were arranged by twisting them together. Next, around the optical fiber core wire 3, C5-1 manufactured by Nippon Vilene Co., Ltd.
5Y (water absorbent resin; sodium polyacrylate, thickness 0.3
5111il) to form a pressing layer 4,
Further, a polyethylene jacket 5 was extrusion coated thereon to produce an optical fiber cable with an outer diameter of 7.1 mm.

For comparison, there is also an extruded coating layer of Purawet on the outer periphery.
An optical fiber cable was manufactured in exactly the same manner as in the example except that an FRP wire with a diameter of 0.9+ nm was used instead of the FRP thin wire provided with.

Next, the optical fiber cables obtained in Examples and Comparative Examples were tested for waterproofness by the method shown below.

In other words, ion-exchanged water colored with red ink was used to create a water head length of 1 m on the cross section of an optical fiber cable sample.
water pressure (0.1 atm) was applied, and the water travel (immersion) length was measured 24 hours later.

The measurement results were as follows.

As is clear from this result, the optical fiber cable of this example has a shorter running length than the cable of the comparative example, and water running in the length direction is effectively prevented.

Furthermore, when we investigated the variation in optical transmission loss by applying lateral pressure, bending, tension, etc., the optical fiber cable of the example showed characteristics that were equal to or better than those of the optical fiber cable of the comparative example.

[Effects of the Invention] As explained above, in the optical fiber cable of the present invention, a highly water-absorbing layer is provided not only on the outer periphery of the optical fiber core wire but also on the outer periphery of the central tension member. When water enters the pipe, the water stops within an extremely short distance and almost no water travels in the length direction, and the bending material from the outside is not decomposed by microorganisms and generates hydrogen gas, so the transmission characteristics are improved. Excellent long-term reliability. Furthermore, since no metal is used as a constituent material and the device has a non-metal structure, it is not subject to electromagnetic induction from power lines, lightning, etc., and there are no restrictions on where it can be used. Furthermore, workability during manufacturing, connection, etc. is good.

[Brief explanation of the drawing]

The drawing is a cross-sectional view showing an optical fiber cable obtained in an example of the present invention. DESCRIPTION OF SYMBOLS 1... FRP thin wire, 2... Extruded coating layer of super absorbent resin, 3... Optical fiber core wire, 4... Pressing layer of super absorbent tape, 5... Polyethylene outer covering

Claims (1)

[Claims] (1) A coating layer of super absorbent resin is provided around the outer periphery of the non-metal tension member, and a plurality of optical fiber cores are arranged around the coating layer, and a pressing layer of super absorbent tape is placed on the outside of the optical fiber core. A waterproof optical fiber cable characterized by being sequentially provided with a plastic outer sheath.