JPS6265005A - Heat resistant and low temperature resistant optical fiber cable - Google Patents

Abstract

PURPOSE:To obtain an optical fiber cable having a transmission characteristic stable against temp. fluctuation and highly stable mechanical characteristics by making lap winding of heat resistant resin tapes and heating and welding or adhering the superposed parts to form a tube shape. CONSTITUTION:Tensile fibers such as glass fibers are arranged to enclose the optical fiber 1 and the heat resistant resin tapes 31, 32 are wound thereon. A polytetrafluoroethylene is used for the tapes. Inside layers 31 are lap-wound and outside layers 31 are also lap-wound. The superposed parts thereof are heated and welded. As a result, the strength deterioration of the tensile fibers 2 by the effect of a high temp. is prevented by the heat insulating effect of the inside layers 3, by which the heat resistant and low temp. resistant optical fiber cable having the high strength is obtd. The heat resistant resin tapes may be adhered to each other by a polyimide adhesive agent.

Description

[Detailed Description of the Invention] [Summary of the Invention] The sheath structure serving as the outer sheath of an optical fiber cable is formed by overlapping heat-resistant resin tapes, and the overlapping portions of the overlapping windings are bonded or heat-sealed to form a chain shape. A heat-resistant and low-temperature resistant optical fiber cable that has stable transmission characteristics as an optical fiber even at high and low temperatures, and has mechanical properties as an optical fiber cable.

[Industrial application field]

The present invention relates to a heat-resistant and low-temperature resistant optical fiber cable, and particularly to an improvement in the jacket structure of an optical fiber cable that requires both heat and low-temperature resistance properties.

[Conventional technology]

FIG. 5 shows an example of the cross-sectional structure of a conventional optical 71 ipakable. 1 is optical fiber and 2 is tensile strength fiber.

j? As a general theory or a general theory or a parable of the term 1. As a material for forming the jacket of an optical fiber cable made of metal and intended for heat resistance, for example, a heat-resistant resin 4 with heat resistance is used. Heat-resistant fluororesin is used. Examples of heat-resistant fluororesins include fluorinated ethylene/fluorinated polypropylene copolymers (hereinafter referred to as FEP) and polytetrafluoroethylene/perfluoroalkyl vinyl ether copolymers (hereinafter referred to as PFA) as sheath materials for optical fiber cables. )and so on. The melting point of these fluororesins is 275°C for FEP and 310°C for PFA.
In terms of reliability, FEP has a heat resistance temperature of 1506C to 200'C.

For PFA, the temperature is 2008C to 260°C.

[Problem that the invention seeks to solve]

In optical fiber cables that use fluororesin such as FEP or PFA as a sheath material, extrusion molding of the fluororesin is difficult, and the molding temperature is high and residual strain tends to remain during extrusion. Therefore, when heat cycles are performed over a long period of time or when exposed to high temperatures continuously, the residual strain is released and the fluororesin contracts. For example, results have been obtained that FEP shrinks by about 2% when heated for a long time, and PFA shrinks by about 3cm. The influence of this shrinkage on the optical fiber cable becomes more noticeable by performing a heat cycle.

FIG. 6 shows the temperature characteristics of an optical fiber cable showing the influence on the optical fiber cable due to contraction of the fluororesin as a sheath material. That is, in the structure of the conventional optical fiber cable whose cross-sectional structure is shown in Fig. 5, F is used as the sheath part.
Regarding optical fiber cable using EP, (-65
When heat cycles are performed in the temperature range (°C→+150°C), transmission loss increases on the low temperature side as the number of cycles increases.

This phenomenon occurs on the high temperature side when the shrinkage strain of the resin in the sheath part is released and it contracts, but this cancels out the thermal expansion of the resin itself, suppressing the shrinkage of the resin as a whole, and having little effect on the transmission characteristics. However, the resin that has passed through the high temperature side contracts due to the release of residual strain, and on the low temperature side, this contraction is added to the thermal contraction of the resin itself, increasing the amount of shrinkage. Therefore, microbending loss is imparted to the optical fiber, resulting in an increase in transmission loss. This increase in transmission loss reaches saturation as residual distortion is released.

Therefore, these resins used as sheath materials have a large influence on transmission characteristics due to residual strain, making it impossible to obtain stable transmission characteristics with respect to temperature. Moreover, due to this shrinkage, at the end of the optical fiber cable, There is a problem in that the protrusion of the optical fiber may cause adverse effects.

In addition, some resins that have heat resistance but high melt viscosity require a molding process in which the powder is compressed at room temperature, then heated above the melting point and fired (paste extrusion method). Are known.). Examples of resins used in this process include polytetrafluoroethylene (hereinafter referred to as PTFE. It is not possible to use resins such as those mentioned above, since the material of which the pull is constructed is exposed to excessive pressure and temperature.

In addition, if the sheath structure of an optical fiber cable is only made of overlapping layers of heat-resistant resin tape, it will be susceptible to abrasion and the heat-resistant flank tape will peel off and break. Therefore, conventionally, it cannot be used as a sheath material.

[Means for solving problems]

In order to solve the conventional problems, the outer sheath forming the sheath of the optical fiber cable is constructed by overlapping heat-resistant resin tapes, and the electrically conductive parts of the overlapping heat-resistant resin tapes are bonded or heat-fused. It is characterized by a tube-like structure.

[Effect]

The present invention forms a sheath of an optical fiber cable, and glues or heat-seals the overlapping portions of the overlapping windings to form a tube, thereby making it possible to use thermoplastic heat-resistant resin, which is originally difficult to extrude, and extrusion molding into an optical fiber. Even resins such as heat-resistant resins that cannot be processed into a tape can be molded into a tape shape and used as a sheath material, making it possible to use resins that have higher heat resistance than conventional ones. In addition, even when heated, the residual strain remaining in the heat-resistant resin tape is caused by the overlapping 9 parts of the heat-resistant resin tape that act to cancel each other's shrinkage, as shown in Figure 5. Reduce impact.

In addition, since the heat-resistant resin tape has a tube shape in which the overlapping layers are glued or heat-fused, the optical fiber cable has excellent mechanical properties such as wear resistance. Examples will be described below based on the drawings.

〔Example〕

FIG. 1 is a cross-sectional structure of an embodiment of the heat-resistant and low-temperature resistant optical fiber cable of the present invention, and FIG. 2 is an explanatory diagram of the structure of the heat-resistant and low-temperature resistant optical fiber cable of the embodiment of the present invention shown in FIG. 1
2 is the optical fiber, 2 is the tensile strength fiber, and 31.32 is the first and second layer heat-resistant resin tape of the two-layer structure that forms the sheath of the optical fiber cable. The overlapping state of the resin tape 31 1fAt- is shown.

In this embodiment, aramid fibers are arranged as the tensile strength fibers 2 by longitudinally splicing, twisting, or braiding, but if it is desired to maintain strength even at high temperatures, glass fibers, ceramic fibers, etc. may be used.

In addition, in this embodiment, the sheath is formed with a two-layer structure of heat-resistant resin tapes 51 and 52, and the first layer of heat-resistant resin tape 5 is the inner layer.
No. 1 is the IT, and only the second heat-resistant resin tape 32 of the outer layer has a structure in which the overlapping portions of the overlapping windings are heat-sealed.

The structure of this embodiment is just an example, and the structure may vary depending on the purpose of use.For example, the heat-resistant resin tape may have only one layer, or may have multiple layers of two or more layers. You can follow the layers. In the case of a multi-layered structure of heat-resistant resin tape, the inner layer is effective in providing insulation when the outer layer of heat-resistant resin tape is heat-fused and preventing the release of residual strain caused by heating from reaching the optical fiber. be.

In response to this effect, in this embodiment, the heat-resistant resin tape 31.
PTFII t″ is used as 32, and the outer 2 of the two-layer structure
Only the 1Uth heat-resistant resin tape 52 was heat-sealed at the overlapping portions. As a result, due to the heat insulating effect of the inner first layer heat-resistant resin tape 51, the tensile strength fibers 2 were not affected by strength deterioration due to high temperatures, making it possible to realize a high-strength heat-resistant and low-temperature optical fiber cable.

Alternatively, heat-resistant resin tapes may be bonded together using a heat-resistant adhesive instead of heat-sealing.

As the adhesive, a polyimide adhesive or the like can be used.

Also, for the part where the heat-resistant resin tape is overlapped,
The following effects can be expected. That is, in FIG. 3, for example, when heat shrinkage occurs in the overlapped layer i3 of the heat-resistant resin cheese 31, However, in the overlapping portion 5, the directions in which the contractile forces act are opposite to each other as shown by the arrows, so that they have the effect of canceling each other out. The same consideration can be given to thermal expansion, so that the sheath structure is stable against temperature fluctuations, and the optical fiber can also ensure stable transmission characteristics.

FIG. 4 shows the temperature characteristics of the heat-resistant and low-temperature optical fiber cable of this example. In this example, PTFIB is used as the heat-resistant resin tape, and it has a two-layer structure of FTFB.
The overlapping portions of the FIB spirally wound layers were heat-fused. In FIG. 4, three cycles of -65°CM + 260°CO temperature cycles were performed, and reproducible temperature characteristics were obtained in all five cycles. Furthermore, the increase in transmission loss was suppressed to less than 10 dB, confirming low loss and stable transmission characteristics.

Furthermore, by heat-sealing or adhering the overlapping portions of the heat-resistant resin tapes, the outermost layer has a tubular shape and has excellent mechanical properties such as abrasion resistance. At this time, it is best to make the overlapped part of the heat-resistant resin tape 310@ to be heat-fused or bonded as shown schematically in FIG. By adhesion or adhesion, the step of the heat-resistant resin tape is eliminated and its mechanical properties are improved.

〔Effect of the invention〕

As described above, the heat-resistant and low-temperature resistant optical fiber cable of the present invention has a sheath structure in which a heat-resistant resin tape is wrapped in layers, and the overlapping portions of the layers are heat-fused or bonded to form a tube-like structure. By expanding the types of heat-resistant resin that can be used as a sheath material, it has characteristics that exceed the conventional heat-resistant temperature, and it also has stable transmission characteristics as an optical fiber, even against repeated temperature fluctuations at low and high temperatures.
Furthermore, high reliability in mechanical properties is ensured, and the effect is remarkable.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional structure of a heat-resistant and low-temperature resistant optical fiber cable of the present invention, Fig. 2 is an explanatory diagram of the structure of a heat-resistant and low-temperature resistant optical fiber cable of the present invention, and Fig. 3 is a cross-sectional structure of a heat-resistant resin tape wrapped in layers and the tape. 4 shows the temperature characteristics of the heat-resistant and low-temperature resistant optical fiber cable of the present invention, FIG. 5 shows the cross-sectional structure of a conventional optical fiber cable, and FIG. 6 shows the temperature characteristics of the conventional optical fiber cable. DESCRIPTION OF SYMBOLS 1... Optical fiber, 2... Tensile fiber, 3... 1st fold of heat-resistant resin tape overlapping, 31.5
2...Heat-resistant resin tape, 4...Heat-resistant resin patent applicant Sumitomo Electric Industries Co., Ltd. agent Patent attorney Hisashi Tamamushi Part 5 Cross-sectional structure of heat-resistant and low-temperature resistant optical fiber cable of the present invention
1 Fig. Structure explanation of the heat-resistant and low-temperature resistant optical fiber cable of the present invention Whistle 2 Fig. jt Cross-sectional structure of overlapping thermal resin tape and explanation of tape shrinkage Fig. 3 Temperature (°C) of the heat-resistant and low-temperature resistant optical fiber cable of the present invention Temperature characteristics
Figure 4 Cross-sectional structure of conventional optical fiber cable Figure 5 Temperature characteristics of conventional optical fiber cable Figure 6

Claims (2)

[Claims] (1) In an optical fiber cable in which a jacket is applied to the outer periphery of an assembly of single-core or multi-core optical fibers in which tensile strength fibers are vertically attached, twisted, or arranged by braiding, the jacket is A heat-resistant and low-temperature optical fiber cable comprising a heat-resistant and low-temperature-resistant optical fiber cable made of overlapping windings of heat-resistant resin tape, and having a structure in which the overlapping portions of the windings of the heat-resistant resin tape are bonded or heat-sealed. (2) The outer sheath is made of one or more layers of heat-resistant resin tape, and the overlapping portion of the outermost layer of the heat-resistant resin tape has an adhesive or heat-sealed structure. A heat-resistant and low-temperature resistant optical fiber cable according to claim 1.