JPS6210404B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas dam structure for an optical fiber cable.

FIG. 1 shows an example of a sealed termination part of a conventional optical stub cable, in which an end plate 2 is connected and fixed on a cable jacket 1, and optical fiber cores 3 are aligned with a alignment plate 4. The wire alignment plate 4 is connected to a metal pipe 5 and a support rod 6 and fixed to the end plate 2. An intervening core wire (plastic insulated copper core wire) 7 and a gas pipe 8 are housed inside the metal pipe 5. The space created by the end plate 2 and the termination sleeve 9 is filled with a thermosetting resin 10 such as epoxy resin or polyurethane resin, and the outer peripheral surfaces of the optical fiber core 3, the interposed core wire 7, and the gas pipe 8 are filled. The thermosetting resin 10
An airtight interface is obtained. Furthermore, for airtightness along the cable jacket, if the cable jacket is a plastic jacket, a tape made of aluminum laminated with a heat-melt adhesive is fused onto the cable jacket 1 with the aluminum side 11 facing outward. Adhesion with the thermosetting resin 10 is obtained by, for example,

Such conventional sealed terminations have metal pipes and support rods inside the thermosetting resin, as well as metal cutting points and protrusions, so the thermosetting resin deteriorates during heat cycles. Cracks sometimes occurred in the resin due to the difference in linear expansion coefficient between the resin and the metal. In addition, the resin often peels off at the adhesive interface between the termination sleeve or the inner surface of the metal pipe and the resin, resulting in poor airtight reliability.

FIG. 2 shows an example of a gas dam part of a conventional optical fiber cable.The cable jacket 1 is stripped off to expose the optical fiber core 3, the intervening core wire 7, and the tension member 12.
For 2, after cutting in the middle, metal sleeve 1
3, the tension member 12 is connected to improve airtightness. Further, the surface of the cable jacket 1 is made airtight by covering the entire dam part with the case 14 and connecting it to the cable jacket 1 using the same method as shown in FIG.

Next, a thermosetting resin 10 such as epoxy resin or polyurethane resin was filled to form a gas dam part.

Like the termination section, this gas dam section also has metal cuts and protrusions within the thermosetting resin, and cracks often occur in the resin due to heat cycles.

On the other hand, it is necessary to avoid uneven stress as much as possible on the optical fiber core, which is susceptible to mechanical stress. However, in the conventional structure, the optical fiber core has curved parts, which are encapsulated in the resin. As a result,
When the entire gas dam section was subjected to heat cycling, unequal forces were generated on the optical fiber cores, resulting in a detrimental increase in optical transmission losses.

In order to eliminate these drawbacks, the present invention uses a thermosetting resin component having through holes with inner diameters larger than those of the cable core wire, copper core wire, and gas pipe, respectively. A thermosetting resin is injected into the gap through the core wire and the gas pipe to form an airtight block, and the airtight block and the termination sleeve form a gas dam part that forms an airtight part using an O-ring. The present invention will be explained in detail below with reference to the drawings.

FIG. 3 is a longitudinal sectional view of an embodiment of a gas dam portion of an optical fiber cable. 4A and 4B are a detailed longitudinal sectional view and a plan view, respectively, of the epoxy resin component shown in FIG. 3. In Fig. 3, 1 is a cable jacket, 3 is an optical fiber core wire, 7 is a plastic-coated copper core wire, 15 is a gas pipe, 16 is an epoxy resin part, 16-1 is a large diameter part of a through hole, 16-2 17 is an injected epoxy resin, 18 is a soft polyurethane resin, 19 is an airtight block in which a cable core wire etc. is adhesively fixed in the through hole of an epoxy resin part, 20 is a support rod, and 21 is a small diameter part of the through hole. End plate, 21-1 is bolt, 21-2 is O-ring, 2
2 is an airtight block housing tube, 23 is a termination sleeve,
23-1 is an O-ring, and 23-2 is a termination sleeve protrusion.

The gas dam structure shown in FIG. 3 is assembled as described below. A cylindrical body made of thermosetting resin such as epoxy resin is connected to a plurality of optical fiber core wires 3, a plurality of copper core wires 7 and a gas pipe 15.
(only one hole in the center) is molded into a part 16 having through holes with an inner diameter slightly larger than the outer diameter of each hole. First, the copper core wire 7 is inserted into the hole other than the outermost hole, and the gas pipe 15 is inserted into the center hole. Then, epoxy resin 17 is injected into the gap around the copper core wire and the gas pipe to integrate them. Thereafter, the optical fiber core wire is passed through a through hole in the outer peripheral part of the component 16 and pulled out to the outside, and a soft polyurethane resin 18 is injected into the space around the fiber to integrate it. Through the above steps, the airtight block 19 is formed. At the stage of creating this airtight block 19, in order to smoothly inject the injected epoxy resin 17 and the injected soft polyurethane resin 18 and to prevent them from flowing out to the lower part, the through holes are made with a large diameter 16-1 (injection side) and a small diameter 16-2. It consists of two stages (on the outflow prevention side). The airtight block 19 is housed in a metal cylindrical tube 22 fixed to an end plate 21 by a support rod 20, and is not bonded to the metal cylindrical tube 22 to avoid the influence of heat. The end plate 21 is connected and fixed to the cable jacket (plastic jacket) 1 by a polyethylene molding method, a method using a hot melt adhesive and a heat shrink tube, etc., and an airtight part is formed along the cable jacket. The termination sleeve 23 is fixed to the end plate 21 by a plurality of bolts 21-1, and is fixed to the end plate 21 by an O-ring 21-2.
Airtightness between the terminal sleeve 23 and the termination sleeve 23 is obtained. Further, an O-ring 23-1 provides airtightness between the airtight block 19 and the inner surface of the termination sleeve 23. Further, the termination sleeve 23 has a protrusion 23-2,
This projection 23-2 prevents the airtight block 19 from protruding due to internal pressure.

In this way, this gas dam accommodates the optical fiber core wire 3 in the through holes 16-1 and 16-2 of the epoxy resin component 16, so thermosetting resin is injected into the through holes to straighten the optical fiber core wire. It is possible to maintain the current level, and the increase in losses can be improved. Also, optical fiber core 3
Since it is placed at the outermost periphery of the epoxy resin, the effects of heat shrinkage can be reduced. In this case, since the soft polyurethane resin 18 is injected into the gap around the optical fiber, the influence of the hard epoxy resin can be further alleviated. Furthermore, since there is no metal inclusion in the resin that would prevent the resin from expanding and contracting due to temperature changes, and the airtight block 19 is not restrained by the metal cylindrical tube 22 or the termination sleeve 23, it is airtight even when subjected to heat cycles. The block 19 can expand and contract freely, thus avoiding the cracks that occur in conventional dams.

As explained above, the gas dam structure of the optical fiber cable of the present invention uses a thermosetting resin component such as an epoxy resin having a through hole with an inner diameter larger than the outer diameter of the optical fiber core, copper core wire, and gas pipe. The core wires and gas pipes are hardened with epoxy resin in the center of the dam, and the optical fibers are placed and glued with soft polyurethane resin around the outer periphery of the thermosetting resin parts to form an airtight block. A sleeve is a structure whose airtightness is ensured by an O-ring. In this way, the main component of this gas dam is an airtight block that houses cylindrical objects such as cable cores and gas pipes in a straight line.Furthermore, this airtight block is not fixed by adhesive or tightening to the metal fittings in which it is housed. Even when subjected to heat cycles, there is no risk of cracks occurring in the airtight block, making it a highly reliable gas dam.

Furthermore, since the optical fiber core wire is arranged in a straight line around the outer periphery of the thermosetting resin component and is covered with a soft polyurethane resin, the influence on optical transmission loss is extremely small. In this way, a gas dam made of excellent resin can be provided.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a sealed termination portion of a conventional optical stub cable, FIG. 2 is a cross-sectional view of a gas dam portion of a conventional optical fiber cable, and FIG. 3 is a cross-sectional view of a gas dam portion of an optical fiber cable of the present invention. FIG. 4 is a longitudinal cross-sectional view of the embodiment, showing the epoxy resin part used in FIG. 3, A is a detailed longitudinal cross-sectional view thereof, and B is a plan view thereof. DESCRIPTION OF SYMBOLS 1...Cable jacket, 2...End plate, 3...Optical fiber core, 4...Wire arrangement board, 5...Metal pipe, 6...Support rod, 7...Interposed core wire (plastic insulated copper core wire), 8... Gas pipe, 9... Termination sleeve, 10... Thermosetting resin, 11... Aluminum surface of laminate tape, 12... Tension member, 13... Metal sleeve, 14... ...Dam case, 15...Gas pipe, 16...Epoxy resin parts, 16-1...Thick diameter part of through hole, 16-2
...Small diameter part of through hole, 17...Epoxy resin, 1
8... Soft polyurethane resin, 19... Airtight block, 20... Support rod, 21... End plate, 21-
1... Bolt, 21-2... O-ring, 22...
Airtight block housing tube, 23... Termination sleeve, 2
3-1... O-ring, 23-2... Termination sleeve protrusion.

Claims (1)

[Claims] 1. A through hole is formed by arranging in series a hole with an inner diameter slightly larger than the outer diameter of each of the optical fiber core wire, copper core wire, and gas pipe, and a hole with an inner diameter approximately equal to the outer diameter, and the through hole is oriented in the axial direction. Using a plurality of cylindrical parts made only of thermosetting resin, optical fiber core wires, copper core wires, and gas pipes were inserted into the respective through holes, and thermosetting resin was injected and fixed into the gaps around them. forming an airtight block,
The hermetic block is housed in a termination sleeve connected to the end plate which is hermetically fixed to the cable jacket.
A gas dam structure for an optical fiber cable, characterized in that the inner surface of the termination sleeve and the airtight block tube are kept airtight by an O-ring.