JPS62136613A - Optical fiber cable - Google Patents

Abstract

PURPOSE:To reduce a decrease in the coefficient of liner expansion of a sheath material and the release of residual strain and to stabilize transmission characteristics against temperature variation by forming a sheath structure by incorporating specific cut fiber in a specific high polymer material. CONSTITUTION:An optical fiber cable is formed of an optical fiber 1, a high- strength fiber for reinforcement or buffer layer 2, the high polymer material 3, and cut fiber 4 incorporated in the high polymer material. The cut fiber 4 uses glass fiber, ceramic fiber, carbon fiber, aramide fiber, etc., suitably and its elastic modulus is >=4,000kgf/mm<2>. The upper limit of the content percentage depends upon the kind of fiber, but preferably <=70% when the elastic modulus is low, e.g. 4,000kgf/mm<2>. The length of the fiber is preferably <=20mm. Further, the contained fiber is oriented in the direction of extrusion during the extrusion molding of the high polymer material. Thus, transmission characteristics is stabilized against temperature variation.

Description

[Detailed Description of the Invention] [Summary of the Invention] The sheath, which is the outer covering of the original fiber cable, is made of a polymer material containing high elastic fibers, so that it can withstand high and low temperatures in the length direction of the original cable. An original fiber cable that can reduce thermal expansion and contraction caused by thermal fluctuations, maintain the stable transmission characteristics of the original fiber, and improve the mechanical properties of the original fiber cable.

[Industrial application field]

TECHNICAL FIELD The present invention relates to original fiber cables, and in particular to improvements in the sheath structure of the outer jacket of optical fiber cables.

[Conventional technology]

FIG. 3 shows an example of the cross-sectional structure of this type of conventional original fiber cable. 1 is the original fiber, 2 is a reinforcing high-strength fiber or a buffer layer, and 3 is a polymeric material constituting the outer jacket. Conventionally, nylon was used as the jacket material for fiber cables intended for non-metallic purposes.

Thermoplastic resins such as polyethylene and vinyl chloride are used. In addition, when heat resistance is required, fluororesins such as fluorinated ethylene/fluorinated polypropylene copolymer (hereinafter referred to as FEP) and polytetrafluoroethylene bar 7 /I/ ;lr O-furkyl vinyl ether can be used. polymer (hereinafter referred to as PFA) or polyamideimide (hereinafter referred to as FAI).

Polyethersulfone (hereinafter referred to as PES), polyphenylsulfone (hereinafter referred to as PPS), polyimide (hereinafter referred to as PPS),
A heat-resistant resin such as PI (hereinafter referred to as PI) is used.

The melting points of these fluororesins are 275°C for FEP, 310°C for PFA, and 290°C for pps, a heat-resistant resin.
The glass transition points of PAl, PES, and PI, which do not have a clear melting point, are 275°C, 230°C, and 310°C, respectively, and when used as the outer jacket structure of the original fiber cable, from the viewpoint of reliability, FDP has a temperature of 200°C. °C, PFA
It can be used at 260°C. Also, PPS is 170
~200℃, 2 each for PAI, PES, and PI
It can be used at 30°C, 170'C, and 270°C.

[Problem that the invention seeks to solve]

In conventional original fiber cables that use the above-mentioned heat-resistant resin as the jacket material, when the jacket is extruded from the heat-resistant resin used, the molding temperature at which the jacket is drawn from the extrusion port is high, so Due to rapid cooling at room temperature, the fiber solidifies with molecules oriented in the length direction of the original fiber cable, so residual strain tends to remain during extrusion. Therefore, when subjected to a long-term heat cycle or exposed to high temperatures continuously, the residual strain is released and the outer sheath made of the heat-resistant resin used shrinks significantly, especially in the length direction. cause.

For example, FEP shrinks by 2% due to long-term exposure to high temperatures, PFA shrinks by about 3 inches, pps shrinks by about 1%, FAI shrinks by about 1.8 inches, and PES shrinks by about 2%. , PI has been found to cause about 3% contraction. The effect of this shrinkage on the original fiber cable becomes more noticeable by performing a heat cycle.

FIG. 4 is an example showing the temperature characteristics of the original fiber cable, showing the influence of shrinkage on the original fiber cable when fluororesin is used as the jacket material.

That is, the structure of the conventional original fiber cable whose cross-sectional structure is shown in Figure 3 is that FEP is used as the polymer material of the outer jacket part.
An example of heat cycling the original fiber cable in the temperature range from -65°C to +150°C is shown below. As is clear from FIG. 4, as the number of cycles increases, transmission loss increases on the low temperature side. This phenomenon is
On the high temperature side, the shrinkage strain of the resin in the outer covering part is released and it contracts, but the thermal expansion of the resin itself is canceled out, and the shrinkage of the resin as a whole is suppressed, and the effect on the transmission characteristics is small.

[Problem that the invention seeks to solve]

As is clear from the temperature characteristics of conventional original fiber cables, the resin that forms the jacket after passing through the high temperature side contracts due to the release of residual strain, and on the low temperature side, this contraction is caused by the heat of the resin itself. This is added to the shrinkage, and the amount of shrinkage increases. Therefore, microbending loss mainly due to contraction in the length direction is imparted to the original fiber, resulting in an increase in transmission loss. This increase in transmission loss converges to a constant value as residual distortion is released. Therefore, these resins as jacket materials have a large influence on transmission characteristics due to residual strain, making it impossible to obtain stable transmission characteristics against temperature fluctuations.Furthermore, due to this shrinkage, the end of the original fiber cable There was a problem in that the protrusion of the original fiber caused an adverse effect.

[Means for solving problems]

In order to solve the conventional problems, the present invention composites cut fibers of high elastic modulus fibers as an outer sheath material forming the sheath of the original fiber cable, and especially in the length direction due to the pull-down effect during extrusion molding. By obtaining a fiber orientation of
It is characterized by suppressing shrinkage in the length direction due to external thermal fluctuations when used as a cable.

[Effect]

The present invention achieves linear expansion compared to the physical properties of resin by making the structure of the outer plate that forms the sheath of the original fiber cable into a structure in which cut fibers are contained in a polymer material. Since the coefficient is reduced and the compressive strength is improved, there is less expansion and contraction in response to temperature fluctuations, and the optical fiber is less likely to cause microbends. Furthermore, the release of residual strain generated during extrusion molding can be reduced, and the material has stable transmission characteristics against heat cycles. Furthermore, the original fiber cable has mechanical properties such as crush resistance and abrasion resistance that are superior to conventional cables.

Examples will be described below based on the drawings.

〔Example〕

FIGS. 1A and 1B are structural diagrams showing the cross section and structure of the original fiber cable of the present invention. 1 is an original fiber, 2 is a reinforcing high-strength fiber or a buffer layer, 3 is a polymer material, and 4 is a cut fiber contained in the polymer material 3.

In this embodiment, as the cut fibers 4 contained in the polymer material 3, glass fibers, ceramic fibers, carbon fibers, aramid fibers, etc. are used. In this example, short fiber kumquats with a fiber length of 500 μm are used, but the fiber length and content may be selected depending on the purpose of use. For example, if the fiber length is long relative to the sheath thickness or the fiber content is high, the fibers will protrude and deteriorate mechanical properties such as abrasion and bending. Selected according to purpose of use. Further, if the purpose is to improve mechanical properties in addition to simply suppressing shrinkage of the resin caused by release of residual strain, it is necessary to increase the fiber content. Generally, as the content increases, the amount of wear and coefficient of thermal expansion decrease and the compressive strength increases, but as the content increases, it no longer plays the role of the outer sheath of the original fiber cable. The upper limit of this content varies depending on the type of fiber, but it has a low elastic modulus (for example, 4000 k
For fibers with gf/mm2), 70% or less is appropriate. Furthermore, the fiber length depends on the thickness of the base and the capacity of the extrusion molding apparatus, and in this example, it was concluded that 20 mm or less is appropriate.

Furthermore, as a major effect of the present invention, during extrusion molding,
As shown in FIG. 2, it has been observed that the fibers are oriented in the direction in which the resin is extruded, as indicated by the arrow. The same reference numerals as in FIG. 1 indicate the same parts.

5 represents a die, and 10 represents an optical fiber cable. The fibers contained in the resin are oriented in the axial direction of the original fiber cable. As a result, the residual strain generated during extrusion molding is released, the resin is prevented from shrinking, and the shrinkage strain is alleviated in minute portions, so that it does not appear as a shrinkage change in the length direction as a whole. Therefore, a stable sheath structure with a small amount of expansion and contraction against temperature fluctuations is obtained, and the original fiber can also ensure stable transmission characteristics. Furthermore, mechanical properties such as pressure resistance and wear resistance are superior to conventional products.

〔Effect of the invention〕

As described above, the original fiber cable of the present invention has a sheath structure containing cut fibers in a polymer material, so that it is possible to reduce the linear expansion coefficient of the sheath material and the release of residual strain, and to reduce the release of residual strain.・Even in the face of repeated temperature fluctuations, stable transmission characteristics as the original fiber are ensured, and improvements in mechanical properties are also ensured, and the effect is remarkable.

[Brief explanation of drawings]

Figures 1A and B are structural diagrams showing the cross section and structure of the original fiber cable of the present invention. Figure 2 is an explanatory diagram of the orientation of cut fibers during extrusion molding of the original fiber cable of the present invention. Figure 3 is the conventional original fiber cable. Figure 4, a cross-sectional structural diagram of a fiber cable, shows the temperature and reaction characteristics of a conventional original fiber cable. 1...Original fiber 2...High strength fiber for reinforcement or buffer layer 3...Polymer material 4...Cut fiber contained in polymer material 5...Dice 10...Original fiber cable patent Applicant Sumitomo Electric Industries Co., Ltd. Representative Patent Attorney Hisashi Tama Mushi 5 Part A 3 Structure of the fiber group in this defense 2 Part 1 Figure 4 Cut at the time of instep formation! ! IA male orientation explanation 2nd row 2
figure

Claims (4)

[Claims] (1) In an optical fiber cable in which a sheath is applied to the outer periphery of an assembly of single or multi-fiber optical fibers and a buffer layer or tension member if necessary, the sheath has an elastic modulus of 4000 kgf/mm^2 An optical fiber cable having a structure made of a polymeric material containing the above-mentioned fiber materials. (2) The polymer material is Made of material with a heat distortion temperature of 130℃ or higher An optical fiber cable according to claim 1. (3) The above-mentioned fiber material is a cut fiber having a fiber length of 20 mm or less and made of one type or a combination of one or more types selected from the fiber material group of glass fiber, ceramic fiber, carbon fiber, and aramid fiber. The optical fiber cable according to item 1. (4) The optical fiber cable according to claim 1, wherein the polymer material has a volume ratio of 70% or less of the fiber material contained therein.