JPH06258558A - Spacer for carrying optical fiber - Google Patents

Abstract

PURPOSE:To make it possible to obtain the spacer for carrying optical fibers having an excellent low-temp. characteristic and compression resistance by constituting the synthetic resin for the spacer for carrying optical fibers a mixture composed of polybtyrene terephthalate(PBT) and polycarobonate(PC) set in a mixing ratio to a specific range and thereby to make the high density of the optical fiber cable to be realized. CONSTITUTION:In the spacer 1 for carrying optical fibers made of a synthetic resin provided with grooves 2a for housing optical fibers or optical fiber ribbons 5, the synthetic resin is constituted of the mixture composed of the PBT and the PC. The mixing ratio of the PBT and the PC is specified to the 7/3 to 3/7 range. The low-temp. embrittlement temp. is >=-30 deg.C and the low-temp. characteristis is no longer satisfied if the PBC/PC exceeds 7/3. The characteristics by an environmental stress crack test degrade if the PBT/PC exceeds 3/7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spacer for carrying an optical fiber, and more particularly to a technique for improving the compression resistance of the spacer.

[0002]

2. Description of the Related Art Optical fibers used in the field of telecommunications are used when a large number of optical fibers are assembled into a cable and a single optical fiber or an optical fiber tape is carried by a spacer. . At present, such an optical fiber carrying spacer is mainly formed of a high-density polyethylene (hereinafter abbreviated as HDPE) resin, but the places where the optical fiber is used are also widely used in submarine cables. .

By the way, when the optical fiber is used for a submarine cable, the spacer carrying the optical fiber is also required to withstand a large water pressure. Therefore, conventionally, a structure has been adopted in which the optical fiber or the optical fiber tape core wire is housed in the groove of the spacer, and then a plurality of layers of reinforcing material such as metal tape are wound thereon and the sheath is covered over the reinforcing material. It had been. The submarine cable having such a structure has the drawbacks that the diameter is large and the weight per unit length is heavy from the structure described above. Therefore, weight reduction is required, but in order to achieve weight reduction, There was a technical problem described below.

[0004]

That is, as described above, the resin for forming the spacer is mainly HDPE.
Although a resin is used, this HDPE resin is a resin that has well-balanced mechanical properties at low temperatures, processability, economical efficiency, etc. as a spacer for supporting an optical fiber.
Due to its low compressive strength, it is necessary to provide a thick reinforcement layer for submarine cables that require compression resistance. As a result, it is difficult to reduce the weight of the submarine cable, and the bending rigidity also increases, so it is extremely laid. Was getting difficult.

In addition, even when a large number of optical fibers or optical fiber tape core wires are carried and the density is increased, there is a drawback that the shape of the groove is collapsed if the rib thickness is extremely thin, which is a design problem. The degree of freedom was limited. Further, in addition to this, the disadvantage of HDPE resin is that it cannot be used at high temperature because its heat distortion temperature is as low as 80 ° C. Since the volumetric shrinkage rate at the time of molding is large, it is difficult to design the die of the extrusion molding machine, and the dimensional accuracy cannot be obtained with a complicated sectional shape.

[0006] The heat shrinkage is large, and even if the tension member is introduced, microbending is caused in the optical fiber when the adhesiveness to the resin of the main body is insufficient.
The raw material contains a lot of gel, and the thermal stability is poor,
If it is manufactured continuously, decomposed products are generated and the dimensional accuracy of the groove is reduced. Further, the surface roughness of the groove is large, which may lead to an increase in transmission loss of the optical fiber.

On the other hand, the use of the optical fiber cable will be expanded to the subscriber system in the future, but at that time, the diameter of the optical fiber cable is made smaller than that of the cable currently used because of easiness of laying work and economical efficiency. Higher density is required. for that reason,
For example, JP-A-4-143710 and JP-A-4-1-1.
No. 82608, No. 4-77109, No. 4-220612, No. 4-372916, No. 5-19151, No. 4-143.
Various spacers and cables are proposed in Japanese Patent Application Laid-Open No. 710, Japanese Patent Application Laid-Open No. 4-182608, and the like.

[0008] If the compression resistance of the spacer itself can be improved, it is expected that the submarine cable will also adopt the spacer shape as disclosed in the above publication. However, when the HDPE resin is used as the material for forming the spacer, it cannot be applied to such an application. Therefore, the present inventors have examined various characteristics required for the resin for the spacer.

As a result, it was concluded that low temperature embrittlement temperature and compression resistance are very important for the spacer resin. The reason why the low temperature embrittlement temperature is important is that the environment temperature of the cable is laid in the temperature range of -40 ° C to + 70 ° C, or is used for a long time while being bent. This is because it is necessary to secure high performance.

Further, the reason why the compression resistance is important is that, for example, if the cable is stepped on during the laying work or is laid under a heavy object, a lateral pressure is applied to the cable. Do not leave damage to the optical fiber contained within. That is, even if compressive deformation occurs, it is necessary to restore the original state if the load is removed.

Further, when the cable is passed through the existing pipe, bending stress and tensile stress are applied. Even in such a state, the transmission characteristics of the cable should not be deteriorated. The amount of stress applied depends on the cable specifications, but in the case of a subscriber system, it is 250k as a cable.
It is required that there is no significant increase in transmission loss under a load of g / 50 mm, and in order to meet such a demand, it is necessary to secure the compression resistance performance of the spacer within a predetermined range.

The present invention has been made in view of the above circumstances, and the purpose thereof is to achieve the conventional H
An object of the present invention is to provide a spacer for supporting an optical fiber that solves the problem of the spacer made of DPE resin and has both compression resistance and use environment characteristics.

[0013]

In order to achieve the above object, the present invention provides an optical fiber carrying spacer made of synthetic resin, which is provided with a groove for accommodating an optical fiber or an optical fiber tape. Composed of a mixture of polybutylene terephthalate and polycarbonate,
The mixing ratio of the polybutylene terephthalate and the polycarbonate is set within the range of 7/3 to 3/7.

In this case, the reason why the mixing ratio of polybutylene terephthalate and polycarbonate is set within the range of 7/3 to 3/7 is that when PBT / PC exceeds 7/3, the low temperature embrittlement temperature is-. When the temperature becomes 30 ° C. or higher, the low temperature characteristics cannot be satisfied, and when PBT / PC exceeds 3/7, the characteristics due to the environmental stress cracking test deteriorate, so the above range must be satisfied.

[0015]

According to the spacer for carrying an optical fiber having the above structure, the resin for forming the spacer is composed of a mixture of polybutylene terephthalate (hereinafter abbreviated as PBT) and polycarbonate (hereinafter abbreviated as PC). Therefore, as is clear from the operation and effect of the examples to be described later, if the spacer has the same diameter as that of the conventional spacer made of HDPE resin, about twice the compressive strength can be obtained. Further, if the compressive strength is the same, the rib thickness of the spacer can be reduced, which enables the diameter of the cable to be reduced and the cross-section ratio of the groove portion in the spacer cross-section to be increased. Become.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. Example 1 (PBT / PC = 5/5) FIG. 1 shows Example 1 of the spacer for carrying an optical fiber according to the present invention. The spacer for supporting an optical fiber shown in the figure is provided with an optical fiber or an optical fiber which is integrally formed of synthetic resin and is provided at substantially equal angular intervals on the outer periphery of the main body 1 when the main body 1 is extrusion molded. It has five grooves 2a to 2e for accommodating the core wire, and a tensile strength wire 3 made of KFRP (aramid fiber reinforced synthetic resin) is arranged at the center of the main body 1.

The grooves 2a to 2e are formed on the main body 1 at a predetermined pitch.
Each of the grooves 2a to 2e is formed in a spiral shape that circulates around, and is defined in a substantially concave shape by ribs 4a to 4e having a substantially fan-shaped cross section. Such an optical fiber carrying spacer was experimentally manufactured under the following conditions. As the synthetic resin of the main body portion 1, a mixed resin (PBT / PC polymer alloy, manufactured by Teijin Ltd., trade name, H7500N) having a PBT / PC mixing ratio of 5/5 is used.
The width of the grooves 2a to 2e was set to 2.7 mm, the depth of the grooves 2a to 2e was set to 2.8 mm, and the pitch was set to 500 mm.

The obtained spacer has an outer diameter D _{1 of the} main body _1.
Is 10.4 mm and the valley diameter D ₂ between the grooves 2a to 2e is 4.4.
mm, the thickness l of the root portions of the ribs 4a to 4e is 0.43.
It was mm. In the spacer thus obtained, as shown in FIG. 2, five optical fiber core wires 5 of 8 cores are housed in the groove 2a, and a compressive load is applied by the method shown in FIG. The transmission loss of the optical fibers (indicated by reference characters A to D in FIG. 2) on both ends of the uppermost optical fiber core wire 5 which is easily affected by is measured. After applying such a compressive load, the load was removed and the dimensional change of the spacer was measured after 3 minutes, but no residual strain was observed.

Example 2 (PBT / PC = 3/7) As a mixed resin for forming the main body 1, a mixed resin having a PBT / PC mixing ratio of 5/5 (PBT / PC polymer alloy, manufactured by Teijin Ltd., 60 parts by weight of product name, H7500) and 40 parts by weight of PC resin (Teijin Kasei Co., Ltd., product name, Panlite K-1300) are mixed to obtain PBT / PC.
An optical fiber spacer having the cross-sectional shape shown in FIG. 1 was prepared under the same conditions as in Example 1 except that a mixture ratio of 3/7 was used.

Various physical property tests were carried out on the obtained spacer in the same manner as in Example 1 to confirm its performance. The results of this test are shown in FIG. Example 3 (PBT / PC = 7/3) As the mixed resin for forming the main body 1, a mixture having a PBT / PC mixing ratio of 3/7 was prepared by the same method as in Example 2, and this mixed resin was prepared. An optical fiber spacer having the cross-sectional shape shown in FIG. 1 was prepared under the same conditions as in Example 1 except that a mixed synthetic resin having a ratio was used.

Various physical property tests were conducted on the obtained spacers in the same manner as in Example 1 to confirm the performance. The results of this test are shown in FIG. Comparative Example 1 (PBT / PC = 8/2) As a mixed resin for forming the main body 1, a mixed resin having a PBT / PC mixing ratio of 5/5 (PBT / PC polymer alloy, manufactured by Teijin Ltd., trade name, H7500N) 40 parts by weight and PBT resin (manufactured by Teijin Limited, trade name, C700
0N) 60 parts by weight was mixed, and an optical fiber spacer having a cross-sectional shape shown in FIG. 1 was prepared under the same conditions as in Example 1 except that a PBT / PC mixture ratio of 8/2 was used. .

Various physical property tests were carried out on the obtained spacer in the same manner as in Example 1 to confirm its performance. The results of this test are shown in FIG. Comparative Example 2 (PBT / PC = 2/8) As a mixed resin for forming the main body 1, a mixed resin having a PBT / PC mixing ratio of 5/5 (PBT / PC polymer alloy, manufactured by Teijin Ltd., trade name, H7500) 40 parts by weight and PC resin (Teijin Kasei Co., Ltd., trade name, Panlite K-1300) 60 parts by weight are mixed to obtain PBT / PC.
An optical fiber spacer having the cross-sectional shape shown in FIG. 1 was prepared under the same conditions as in Example 1 except that a mixture ratio of 8/2 was used.

Various physical property tests were conducted on the obtained spacer in the same manner as in Example 1 to confirm its performance. The results of this test are shown in FIG.

Comparative Example 3 (HDPE) A spacer was prepared in the same manner as in Example 1 except that HDPE resin (trade name: Hizex6300M manufactured by Mitsui Petrochemical Co., Ltd.) was used as the resin for forming the main body 1. Then, a lateral pressure test was performed. The test results are shown in FIG. In addition, in this example, the thickness l of the root portions of the ribs 4a to 4e was 0.4 mm.

Comparative Example 4 (HDPE) A spacer was prepared in the same manner as in Example 1 except that HDPE resin (trade name: Hizex6300M manufactured by Mitsui Petrochemical Co., Ltd.) was used as the resin for forming the main body 1. Then, a lateral pressure test was performed. The test results are shown in FIG. In addition, in this example, the thickness 1 of the root portions of the ribs 4a to 4e was 0.9 mm.

Here, the conditions of the tests conducted in the above-mentioned examples and comparative examples will be described. Compression test and measurement of transmission loss increase due to lateral pressure 8 in one of the grooves 2a to 2e of the spacer having a length of 100 mm.
The optical fiber tape core wire 5 of the core is stored in 5 stages, and this is shown in FIG.
The strain amount (unit: mm) when a load of 500 kg was applied, and the strain amount when the load was removed (strain after unloading, unit: mm) were measured by sandwiching the load cell as shown in FIG.

The measurement of the transmission loss is such that when a load of 500 kg is applied, it is easily affected by the compressive load A, B,
The optical fibers at the portions C and D (see FIG. 2) were measured while compressing the transmission loss increase Δα at the wavelength of 1.5 μm, and evaluated by the maximum value at each measurement point.

Low temperature embrittlement temperature It was performed in accordance with JIS K-7216. Surface Roughness Using a measuring instrument Surfcom 475A manufactured by Tokyo Seimitsu Co., Ltd., the bottom and side surfaces of the grooves 2a to 2e were measured with a cutoff length of 0.8 mm, and the centerline average roughness Ra was evaluated. Environmental stress crack test As in conformity with JIS K 6760, a spacer was bent to a radius of curvature of 100 mm in a 10% aqueous solution of a nonionic surfactant (Lion Co., Ltd., trade name Liponox NC-400F). In the state, it was immersed at 50 ° C. for 500 hours, and the presence or absence of cracks on the surface of the spacer was visually confirmed.

In the above embodiment, the optical fiber ribbon 5 is stored in the grooves 2a to 2e. However, the optical fibers can be directly stored in the grooves 2a to 2e. Further, in the above-mentioned embodiment, the case where the present invention is applied to the spacer for carrying an optical fiber in which the plurality of spiral grooves 2a to 2e are integrally formed in the main body 1 is illustrated, but the present invention is not limited to this. There is no limitation. For example, JP-A-4-143710 and JP-A-4-182608.
Japanese Patent Laid-Open No. 4-77109, Japanese Patent Laid-Open No. 4-22
No. 0612, JP-A-4-372916, JP-A-5-19151, JP-A-4-143710, JP-A-4-182608, and other spacers provided with optical fiber storage grooves. It can also be applied to cables.

[0030]

As is apparent from the test results shown in FIG. 4, it is composed of a mixture of polybutylene terephthalate and polycarbonate, and the mixing ratio of polybutylene terephthalate and polycarbonate is within the range of 7/3 to 3/7. It was found that the synthetic resin optical fiber carrying spacer according to the present invention set in (4) is excellent in low temperature characteristics and compression resistance, and such a spacer is suitable as a submarine optical fiber cable. In addition, the density of the optical fiber cable can be increased more than ever before.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an optical fiber carrying spacer according to the present invention.

FIG. 2 is an explanatory view showing a state in which an optical fiber tape core wire is housed in a groove of a spacer shown in FIG.

FIG. 3 is an explanatory diagram of a test state of a compressive load test of a spacer for carrying an optical fiber.

FIG. 4 is a chart showing the results of various physical property tests of Examples of the present invention and Comparative Examples.

[Explanation of symbols]

 1 Main Body 2a-2e Groove 3 Tensile Strength Wire 4a-4e Rib

Claims (1)

[Claims] 1. A synthetic resin optical fiber carrying spacer provided with a groove for accommodating an optical fiber or an optical fiber tape, wherein the synthetic resin is composed of a mixture of polybutylene terephthalate and polycarbonate. The mixing ratio of terephthalate and polycarbonate is 7 /
An optical fiber carrying spacer characterized by being set within a range of 3 to 3/7.