JPH048403Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Background and Purpose of the Invention] The present invention relates to an improvement of a so-called optical cable with a gas dam, which retains gas in order to ensure the reliability of the optical line.

It is widely known in the industry that when fiber core wire is drawn, countless minute scratches are created on the glass surface, and the scratches described above can grow and reach a certain size depending on the environmental conditions of use. This will lead to destruction of the glass. Furthermore, glass is sensitive to moisture, and if moisture is present in the surrounding area while stress is applied to the glass, its lifespan will be shortened. Therefore, after the optical fiber is installed, if moisture is present around the fiber core, which is subjected to bending stress, the reliability of the optical path will be impaired.

In order to eliminate the effects of moisture on the fiber core and ensure the reliability of the optical line, inert gas is pumped into the optical cable to retain the gas.
A so-called optical cable with a gas dam is known.

Here, a typical structural example of conventionally proposed optical cables with gas dams will be explained based on FIG. 3. In FIG. 3, 1 is an optical cable, 2 is a fiber core wire, and 3 is the optical cable A tension member 4 is connected to the end of the optical cable 1 and is a housing, 5 is a sealing tape that seals the connection between the end of the optical cable 1 and the housing 4, and 6 is a gas pipe installed inside the housing 4. Shows gas pipe 6
Gas is fed into the optical cable 1 through the optical cable 1.
Reference numeral 7 denotes a fiber alignment tool attached to the casing 4; 8 a resin filled in the casing 4; inside the casing 4, the fiber core wires 2 are aligned by the fiber alignment tool 7; The airtightness inside is maintained by resin 8.

In the above configuration, the fiber aligner 7 is embedded in the resin 8 with the fiber cores 2 separated one by one. As mentioned above, by embedding the fiber cores 2 in the resin 8 in a state in which each fiber is isolated by the fiber aligner 7, it is easier to bury the fiber cores 2 in the resin 8 in a state where they are separated from each other by the fiber aligner 7, compared to the case where a large number of fiber cores 2 are buried in the resin 8 at once. , the resin 8 is made to spread around each core wire 2 well, and the remaining air bubbles in the resin 8 are reduced. That is, if air bubbles remain in the resin 8 filled in the housing 4, the resin 8
The resin 8 expands and contracts due to temperature changes after it has hardened, and when bending stress is applied to the fiber core 2 in this state, large deformation occurs in the area where the bubbles are present, causing the fiber core to deform. 2 is bent excessively to increase the transmission loss of the optical line. Also,
If the state in which excessive bending stress is applied to the fiber core wire 2 continues for a long period of time, it may cause the core wire 2 to break.

There are two methods for filling the resin 8 into the housing 4: vacuum injection and pressurized injection. It is important to minimize residual air bubbles within the resin 8 as much as possible.

However, as shown in FIG. 4, the conventionally proposed fiber alignment tool 7 for the optical cable 1 with a gas dam has a hole 7a through which the fiber core 2 passes through a plate-shaped member molded from a metal or plastic material. Since the structure is adopted, the housing 4
When filling the resin 8 into the interior, the contact area between the plate-shaped fiber aligner 7 and the injected resin 8, as well as the fiber aligner 7 and the discharged air, is relatively large, and the passage of the injected resin 8 and the discharged air is prevented. This is not done quickly, and the exchange of air and resin 8 is insufficient, so that a relatively large number of air bubbles must remain in the resin 8.

The present invention was developed as a result of studies to solve the problems of the conventional technology described above, and its purpose is to seal the casing, which is the gas dam part of an optical cable with a gas dam, that is, the terminal part of the optical cable. Within the connected casing, there are almost no air bubbles left in the resin filled in the casing, and therefore there is no significant expansion or contraction phenomenon in the resin even when the temperature changes after the resin hardens. An improved optical cable with a gas dam that does not cause excessive local bending strain to the fiber core even when bending stress is applied to the fiber core, and has excellent transmission characteristics and durability of the optical line. It is something that tries to provide.

[Summary of the invention] In order to achieve the above object, the present invention provides a gas pipe for feeding gas into an optical cable within a housing that is sealingly connected to the end of the optical cable, and a fiber core in the housing. An optical cable with a gas dam has a structure in which a fiber aligner for aligning the wires is attached and a resin is filled in the housing to keep the inside of the housing airtight. The present invention is characterized in that it is equipped with a fiber aligning tool configured as shown in FIG.

[Example] Hereinafter, the present invention will be explained based on an example of FIGS. 1 and 2. In FIG. 1, the same reference numerals as those of the conventional optical cable with gas dam shown in FIG. 3 indicate the same parts, i.e. 1 is an optical cable, 2 is a fiber core wire, 3 is a tension member of the optical cable 1, 4 is a housing connected to the terminal part of the optical cable 1,
5 is a sealing tape that seals the connection between the end of the optical cable 1 and the casing 4; 6 is a gas pipe installed inside the casing 4; 7 is a fiber alignment tool attached to the casing 4; 8 is the casing 4. In the present invention, the fiber alignment tool 7 is
As shown in the figure, the gist is a mesh structure formed from metal or plastic material.

Therefore, according to the present invention having the above configuration, when filling the resin 8 into the housing 4, the fiber aligning tool 7 having a mesh structure and the injected resin 8, as well as the fiber aligning tool 7 and the discharged air are connected. The contact area is small, so that the injected resin 8 and the discharged air can pass quickly, the resin 8 and air can be exchanged smoothly, and there are almost no air bubbles remaining in the resin 8. As a result, even with temperature changes after the resin 8 is cured, there is no significant expansion or contraction phenomenon in the resin 8, and even if bending stress is applied to the fiber core 2, the core wire 2 will It does not cause excessive local bending distortion.

Note that there are two ways to attach the fiber aligner 7 to the housing 4, such as attaching the aligner 7 directly to the inner wall of the housing 4, or using the tension member 3. Even in such cases, if the fiber alignment tool 7 is immersed in the resin liquid immediately before filling the resin 8 into the housing 4 and then the fiber alignment tool 7 is quickly attached to the housing 4, air bubbles can be prevented from adhering to the fiber alignment tool 7. can be prevented even more effectively.

[Effects of the invention] The invention is as described above, and as is clear from the explanation of the illustrated embodiments, according to the invention, sealing is applied to the casing that is the gas dam part of the optical cable with gas dam, that is, the terminal part of the optical cable. Within the connected casing, almost no air bubbles remain in the resin filled in the casing, even when the temperature changes after the resin hardens. The transmission characteristics and durability of the optical line are such that the resin does not exhibit large expansion and contraction phenomena, and even if bending stress is applied to the fiber core, localized excessive bending strain will not occur in the fiber core. It is possible to obtain an optical cable with an improved gas dam that has excellent properties.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional side view showing an embodiment of the optical cable with gas dam according to the present invention, Fig. 2 is a front view of the fiber aligner indicated by 7 in Fig. 1, and Fig. 3 is a conventional gas dam. FIG. 4 is a longitudinal sectional side view of the optical cable, and is a front view of the fiber aligner shown at 7 in FIG. 3. 1... Optical cable, 2... Fiber core wire, 3...
...Tension member, 4...Housing, 5...Sealing tape, 6...Gas pipe, 7...Fiber aligner, 8...Resin.

Claims (1)

[Scope of utility model registration request] A gas pipe for feeding gas into the optical cable is installed inside a housing that is sealingly connected to the terminal part of the optical cable, and a fiber alignment tool for aligning the fiber cores is attached to the housing, and the housing is further equipped with a fiber alignment tool for aligning the fiber core wires. An optical cable with a gas dam having a structure in which the inside of the body is filled with a resin for keeping the inside of the housing airtight, characterized in that a fiber aligner made of a mesh member is installed inside the housing. Optical cable with gas dam.