JPH0564324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical fiber cable with a gas dam, which has an optical fiber tape core formed by arranging a plurality of optical fibers in a plane and applying a coating.

[Prior art]

In preparation for the approaching highly information-oriented society, in recent years there has been a rapid switch from conventional copper conductor cables to optical fiber cables, which have many features such as large transmission capacity, small diameter, and light weight.
By the way, even in this optical fiber cable,
Like conventional copper conductor cables, gas-maintained fiber optic cables with gas dams have been developed. As shown in Figure 1, first, the outer sheath 2 of the cable 1
was stripped to a required length at the dam forming part to expose a plurality of optical fiber cores 3, and then the tensile strength member 4 provided to improve the tensile properties of the cable 1 was once cut within the dam forming part. After that, they are connected again using the tensile strength body sleeve 5. The reason for this is to prevent gas paths occurring along the tensile strength member 4. Next, the coefficient of linear expansion in the dam forming part is made the same as that of the optical fiber to prevent gas leakage due to thermal expansion.
In order to prevent increased transmission loss due to microbends that occur in optical fibers, glass fiber reinforced plastic (hereinafter referred to as
A batten 7 supporting a rod 6 made of (referred to as FRP) is attached to the A end of the dam forming part, and the other end B is used to integrate the dam forming part into a junction box following the dam forming part. Attach the flange 8 to be used. Thereafter, the rods 6 made of FRP are placed in a cage shape so as to span the batten 7 and the flange 8 so as to wrap around the optical fiber core 3 in the dam forming part, and both ends are fixed to the batten 7 and the flange 8. Further, one end of the tensile strength member 4 is fixed to the flange 8, and adhesive tape 10 is wrapped on the outer sheath 2 on the A end side of the cable 1 to form a dam portion made of urethane resin or the like so as to cover the dam forming portion. The gas dam part 12 is formed by filling the filling material 11. In such an optical fiber cable with a gas dam, if the optical fiber core 3 is a single core optical fiber core consisting of a single optical fiber coated with several layers, its airtightness may be affected. No problems arose. However, in recent years, optical fiber cables have spread rapidly, and even high-density optical fiber cables, so-called optical fiber cables for subscribers, have appeared. When using the conventional dam formation method described above, it has been found that there is a problem with gas tightness. By the way, as shown in Fig. 2, this high-density optical fiber cable for subscribers consists of a plurality of optical fiber wires 15 coated with a buffer layer made of silicone or the like around the optical fibers. An optical fiber tape core wire formed by arranging optical fibers 15 in parallel to form an assembly, and extrusion coating the assembly with a thermoplastic resin such as nylon or an ultraviolet curable resin such as an acrylic compound as a coating 16. A plurality of pieces 17 are assembled together and then an outer cover is provided. This type of cable is also called a high-density optical fiber cable because it contains more optical fibers than a cable with the same outer diameter that is a collection of single optical fibers. Suitable for subscriber optical fiber cables that house optical fibers. Now, like this, the optical fiber tape core wire 17
A first optical fiber cable 1 having a
When the gas dam part 12 as shown in the figure is provided and the cable is filled with gas, the gap 1 formed by the optical fiber bare wire 15 and the coating 16 in FIG.
8, or alternatively, the interface 19 where the optical fiber strands 15 are in contact with each other or the optical fiber strand 15 and the coating 1
Gas leaks through the interface 20 where the optical fibers 6 and 6 are in contact, and it is necessary to take measures to prevent gas leakage within the optical fiber, which has not been a problem with conventional single-core optical fibers. I'm getting old. The measures that have been taken to date to deal with this problem are to first integrally coat the assembly of optical fibers 15 in FIG.
6 is applied to prevent gas leakage from the gap 18 and the interfaces 19 and 20 over the entire length of the optical fiber tape core 17 in the longitudinal direction. However, this method involves a great deal of waste in that it involves applying a treatment that is only necessary for the dam forming part over the entire length of the cable, and as mentioned above, it requires integrating silicone resin etc. into the aggregate of the optical fiber wires 15. Due to the coating, for example, an increase in transmission loss due to micro bends due to non-uniform coating thickness etc. is observed, and there are many problems in the manufacturing method. Also,
As another countermeasure, there is an attempt to eliminate the internal gas path by compressing the optical fiber ribbon 17 shown in FIG. However, this compression force inevitably increases the transmission loss of the optical fiber, and even this method cannot hope to solve the problem. As mentioned above, in the case of optical fiber cables with gas dams having optical fiber tape cores, gas leaks through the optical fiber tape cores, so conventional methods cannot be used to create optical fiber cables with gas dams that have excellent gas-tightness. can't get it.

[Purpose of the invention]

In view of the above problems, an object of the present invention is to provide an optical fiber cable with a gas dam that has excellent gas-tightness in an optical fiber cable having an optical fiber tape core.

[Structure of the invention]

In order to achieve the above object, the optical fiber cable with a gas dam of the present invention is an optical fiber cable having an optical fiber tape core formed by arranging a plurality of optical fibers in parallel in a plane and providing a coating around them. Then, the required length of the outer sheath of the optical fiber cable is peeled off at the dam forming part to expose the optical fiber tape core, and a dam part forming filler is airtightly filled around the optical fiber tape core. In the optical fiber cable with a gas dam that forms a gas dam part, the optical fiber tape core wire in the gas dam part has its coating stripped off to a required length to form an exposed part in which the optical fiber wire is exposed. , and the exposed portion is housed in a sleeve that is longer than the length of the peeled off coating, and a gas-tight filler is injected and solidified into the gap inside the sleeve, and the dam portion forming material is injected and solidified into the gap inside the sleeve. A sealing material is provided across the sleeve and the coating of the optical fiber tape to prevent the filler from entering the gap inside the sleeve.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 3 shows an embodiment of the invention. As shown in FIG. 3, the outer sheath 2 of the optical fiber cable 1 having the optical fiber tape core 17 is peeled off to a required length at the dam forming portion to expose the optical fiber tape core 17. Subsequently, the tensile strength member 4 inserted to improve the tensile properties of the cable 1 is once cut within the dam forming part, and then connected again with the tensile strength member sleeve 5 to prevent the tension member 4 from being easily generated along the tensile strength member 4. Prevent gas pass. Next, the coating 16 made of a thermoplastic resin such as nylon or polyethylene or an acrylic resin such as epoxy acrylate or urethane acrylate on the exposed optical fiber tape core 17 is peeled off to a required length at an appropriate position within the dam forming part. The optical fiber strand 15 is removed to form an exposed portion, and a sleeve 22 longer than the peeled coating 16 is placed over the exposed portion so as to completely cover the exposed portion. In FIG. 3, the dam forming part is located at the end of the optical fiber cable 1, so this sleeve 22
Pass each optical fiber tape core 17 through this sleeve 22 from the B side in FIG. 3, slide the sleeve 22 to the exposed portion, and store the exposed portion. Next, from one end of the sleeve 22, a gas-tight filler 2 made of a thermosetting or additive thermosetting resin is applied to the entire gap inside the sleeve 22.
Inject 3 with a syringe or the like and allow it to solidify. Note that this gas-tight filler 23 may be a room-temperature curing resin, in which case a heating source is not required, and addition-type resins have less change in volume before and after curing than condensation-type resins. Therefore, airtight filling is easy and preferable. Typical examples of this type of material include addition-type thermosetting and room temperature-curing silicone rubbers.
FIG. 4 is a cross-sectional view of the mounting portion of the sleeve 22 showing a state in which the entire gap inside the sleeve 22 is airtightly filled with the gas-tight filler 23. Here, if there is an interface between each optical fiber strand 15 or between the optical fiber strand 15 and the sleeve 22, gas will easily leak, so spaces are provided as shown in FIG. 4 so that the gas-tight filler 23 can easily enter. It is better to Further, as shown in FIG. 5, the exposed portions of a plurality of optical fiber tape cores 17 may be housed in one sleeve 22, or the sleeve 22 may be oval as shown in FIG. Although not shown, it may be circular. However, if the inner diameter of the sleeve 22 is much larger than the outer diameter of the optical fiber tape core 17, not only will the amount of gas-tight filler 23 injected increase, but also the gas will leak from between the sleeve 22 and the optical fiber tape core 17. Since the airtight filler 23 may flow out, the inner diameter of the sleeve 22 is preferably slightly larger than the outer diameter of the optical fiber tape core 17. Now, when the gas-tight filler 23 is airtightly injected into the entire gap inside the sleeve 22 and solidified, as shown in FIG.
A seal 24 is provided over the coating 16 of the optical fiber tape core 17 using an instant adhesive or the like to prevent the dam part forming filler 11 from entering the inside of the sleeve 22. The reason is that when the dam part forming filler 11 enters the inside of the sleeve 22, the filling pressure causes the sleeve 22 and the sleeve 2
Gas-tight filler 23 injected into 2 and fixed
This is to prevent peeling between the two. Each optical fiber tape core 17 is treated in the same way, but at this time, it is better to gradually shift the position at which the coating 16 is removed from each optical fiber tape core 17 in the longitudinal direction as shown in FIG. Good workability. Further, the hardness of the sleeve 22, the gas-tight filler 23, and the dam part forming filler 11 is different from that of the gas-tight filler 23 and the sleeve 22.
The interface between the sleeve 22 and the dam part forming filler 1
In order to improve gas-tightness at the interface with 1, it is better to make the sleeve 22 harder than the gas-tight filler 23, and to make the dam part forming filler 11 harder than the sleeve 22. The reason for this is that each interface is pressed while being physically pressed. still,
The hardness of the gas-tight filler 23 and the dam-forming filler 11 is the value after hardening. However, this does not apply when each interface is to be kept airtight by adhesive force rather than by pressure bonding force. For example, if the outermost layer of the optical fiber wire 15 is made of acrylic resin, and if the gas-tight filler 23 is made of acrylic resin and the dam part forming filler 11 is made of urethane resin, then the sleeve 22 is made of acrylic resin. If a material made of epoxy acrylate or urethane acrylate resin, which adheres to both system resins and urethane resins, is used, they will easily adhere to each other, and the interface between the materials will easily maintain airtightness.

When all the above-mentioned processes for the optical fiber tape core 17 are completed as described above, the coefficient of linear expansion in the dam forming part is made the same as that of the optical fiber to prevent gas leakage due to thermal expansion and increase in transmission loss due to microbending. A batten 7 supporting a cage-shaped FRP rod 6 provided in the dam forming part is attached to the A end of the dam forming part, and a flange 8 is attached to the other end B end. Thereafter, the FRP rods 6 are arranged in a cage shape so as to wrap around the optical fiber tape core 17 in the dam forming part, and both ends are fixed to the batten 7 and flange 8. Furthermore, after fixing one end of the tensile strength member 4 to the flange 8, adhesive is applied to the outer sheath 2 on the A end side of the cable 1 to improve adhesion with the dam part forming filler 11.
A dam forming filler 1 made of urethane resin or the like is wrapped around an adhesive tape 10 to cover the dam forming part.
1 to form a gas dam part 12.

[Specific examples of the invention]

Here, one specific example of the present invention will be shown. First, the outer diameter
An optical fiber 15 having an outer diameter of 300 μm is obtained by coating a 125 μm optical fiber with silicone resin. Five of these optical fiber wires 15 are arranged in parallel as shown in Fig. 2, coated with nylon coating 16, and
1.6mm, 0.45mm thick optical fiber tape core 17
form. Such optical fiber tape core 1
A gas dam portion 12 was formed on an optical fiber cable including 100 fiber optic cables. The materials used at this time are as follows.

Γ Gas airtight filler 23; Thermosetting silicone rubber (20℃ at 80℃~90℃
Hardness Shore A40~50 after heating for 1 minute) Γ sleeve 22; Stripping length of optical fiber tape core 16
Sleeve length is 90mm compared to 50mm, rectangular sleeve cross-sectional dimensions outer diameter/inner diameter (length 0.9/0.6 x width 2.5/2.0) Made of vinyl acetate alcohol.

Filler for forming Γ dam part: Polyurethane foam The optical fiber cable with gas dam according to the present invention using the above material was subjected to a heat cycle test at -30°C to 70°C 2 cycles/day. The results showed that after 100 cycles, there was no change even when a gas pressure of 1 Kg/cm ² was applied at 20°C. Incidentally, in the conventional method, when a gas pressure of 1 kg/cm ² is applied at 20° C., gas immediately passes through the optical fiber tape core 17 .

In this way, in the present invention, within the dam forming part, the coating of the optical fiber tape core is peeled off by several centimeters to form an exposed part, and after covering that part with a sleeve, the sleeve is inserted into the gap inside the sleeve. Since the gas-tight filler is injected and solidified, this part acts as a dam in each optical fiber tape. Therefore, gas leakage through the inside of the optical fiber tape, which has been a problem in the past, can be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to obtain an optical fiber cable with a gas dam having excellent gas-tightness in an optical fiber cable having an optical fiber tape core.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a conventional optical fiber cable with a gas dam, FIG. 2 is a cross-sectional view of an optical fiber ribbon according to the present invention, and FIG. 3 is an embodiment of the optical fiber cable with a gas dam of the present invention. FIG. 4, FIG. 5, and FIG. 6 are enlarged cross-sectional views showing one embodiment and another embodiment of the part covered with a sleeve in FIG. 3, and FIG. FIG. 3 is an enlarged view of a portion of the sleeve cut parallel to the tape surface of the optical fiber tape. DESCRIPTION OF SYMBOLS 1... Optical fiber cable, 11... Filler for dam part formation, 12... Gas dam part, 15... Optical fiber wire, 16... Coating, 17... Optical fiber tape core wire,
22... Sleeve, 23... Gas-tight filler, 24
…sticker.

Claims (1)

[Scope of Claims] 1. An optical fiber cable having an optical fiber tape core formed by arranging a plurality of optical fibers in parallel in a plane and providing a coating around the fibers,
The required length of the outer sheath of the optical fiber cable is peeled off at the dam forming part to expose the optical fiber tape core, and a dam part forming filler is airtightly filled around the optical fiber tape core to form a gas dam. In the optical fiber cable with a gas dam forming a gas dam part, the optical fiber tape core wire in the gas dam part has an exposed part in which a required length of the coating is stripped off to expose the optical fiber wire, and The exposed portion is housed in a sleeve that is longer than the length of the peeled off coating, and a gas-tight filler is injected and solidified into the gap inside the sleeve, and the dam portion-forming filler is injected and solidified into the gap inside the sleeve. An optical fiber cable with a gas dam, characterized in that a sealing material is provided across the sleeve and the coating of the optical fiber tape core to prevent gas from entering a gap inside the sleeve. 2. The optical fiber cable with a gas dam according to claim 1, wherein exposed portions of a plurality of optical fiber tape cores are housed in one sleeve. 3. The optical fiber cable with a gas dam according to claim 1, wherein the gas-tight filler is a thermosetting silicone resin or a room temperature curing silicone resin. 4. The optical fiber with a gas dam according to claim 1 or 3, wherein the gas-tight filler is an addition type thermosetting silicone resin or an addition type room temperature curing silicone resin. cable.