JPS612111A - Optical cable - Google Patents

Abstract

PURPOSE:To improve characteristics of resistance to forcible drawing against squeezing and to prevent increase of light transmission loss by filling the spaces among the core of an optical cable and optical fibers with a thermosetting or UV curing resin to form one body. CONSTITUTION:The spaces among the core 1 of the optical cable and each optical fiber 2 are filled with a thermobosetting or UV curing resin having an elasticity of 0.1-3kg/mm.<2> to bond them into one body. As a result, although the cable is forcibly drawn against squeezing during installation, disturbance of the interwisted arrangement of the optical fibers due to the movement of jelly is prevented and good resistance characteristics against squeeze drawing are obtained, thus permitting increase of light transmission loss and intrusion of water to be effectively prevented by filling the spaces with the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to optical cables used for optical communications and the like.

Conventional technology and its disadvantages Conventionally, as an example of an optical cable, multiple optical fibers are twisted together around a central body, and one or more optical units are arranged in a sheath, which are made by providing a buffer layer such as PP yarn on top of the twisted optical fibers. It is widely used because its transmission characteristics and other characteristics are stable.

However, optical cables with this type of structure are susceptible to water intrusion due to external damage, etc., if the strength of the optical fiber has deteriorated, or if there is metal such as aluminum inside the optical cable. Metals corrode due to moisture, hydrogen gas is generated along with this corrosion, and this hydrogen gas increases the transmission loss of the optical fiber. For this reason, it is very important to prevent water from coming into contact with the optical unit in the optical cable, and one way to do this is to fill the gap between the optical unit's buffer layer and sheath with jewelry. be. In such a cable, the jelly is preferable because it prevents water from entering the optical unit and maintains its original stable characteristics, but it has the disadvantage of poor resistance to straining.

In other words, when an optical cable with this structure is squeezed during installation, the jewelery inside the sheath moves as it is squeezed.
It enters the part where the optical fibers of the optical unit are twisted together. For this reason, as shown in FIG.
However, as shown in FIG. 6, the twisting of the optical fibers 2 is disturbed and bent irregularly, resulting in an increase in transmission loss.

Purpose of the Invention The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide an optical cable having good resistance to stress, which is formed by filling a gap between an optical unit and a sheath with jewelry. That is.

Structure of the Invention The optical cable of the present invention includes one or more optical units in which optical fibers are twisted around a central body and a buffer layer is provided thereon, and a gap in the sheath is filled with jewelry. The central body and the optical fiber are integrated using a thermosetting resin or an ultraviolet curing resin.

Detailed configuration and its effect FIG. 1 shows an example of the optical cable of the present invention.
Reference numeral 1 in the figure is a central body. Around this central body 1 there are 8
The optical fibers 2... are twisted together to form a stranded wire. The twisted wires are integrated with the resin layer 3. That is, the gaps between the center body 1 and each optical fiber 2... and the gaps between each optical fiber 2... are filled with resin, and these gaps are completely filled with resin, and the center body 1 and each optical fiber 2... are filled with resin. The fibers 2 and the fibers 2 of each party are bonded and fixed together.

This resin layer 3 is made of thermosetting resin or ultraviolet curing resin. In order for the resin to penetrate well into the pores of the twisting, a thermosetting resin or an ultraviolet curable resin that is in a low viscosity liquid state before solidification is used. In the method of coating by melt extruding thermoplastic resin, each fiber 2... can be consolidated, but the optical fiber 2...
The molten resin does not penetrate into the gap between ・ and the center body 1,
A void remains along the central body 1. If this void remains, there is a problem that when water enters, the water will run in the longitudinal direction of the cable using this void as a passageway.As thermosetting resins, epoxy resin, unsaturated polyester resin, A polyurethane resin or the like is used, and as the ultraviolet curable resin, an epoxy-acrylate type, an unsaturated polyester type, an epoxyurethane-acrylate type, etc. are used. In particular, ultraviolet curable resins are desirable because they can be cured in a few seconds to more than ten seconds, so they can speed up production.

If α is less than 1, the resin is too soft and the resin layer 3 cannot resist the movement of the jelly when the optical cable is subjected to straining, and the arrangement of the optical fibers 2 is sufficiently prevented from being disturbed. I can't. In addition, if it exceeds 3 or more, the resin will be too hard and will lose its flexibility, weakening the effect of twisting the optical fibers 2, etc., and furthermore, the shrinkage force that occurs when the resin hardens will cause transmission loss. There is a risk that it will increase.

Figure 2 shows the relationship between the elastic modulus of the resin forming the resin layer 3 and the amount of increase in transmission loss when forming this resin layer 3 to form an optical cable. It can be seen that the amount of increase in transmission loss due to cables increases. Moreover, FIG. 3 shows the relationship between the elastic modulus of the resin and the amount of increase in transmission loss when the optical cable having the resin layer 3 is squeezed. When the elastic modulus of the resin is 0.1 or less, It is recognized that the transmission loss tends to increase when it is strained. Therefore, the resin constituting the resin layer 3 is a thermosetting resin or an ultraviolet curing resin, and its elastic modulus is 0,
It can be seen that those in the range of 1 to 3 are desirable.

Then, on this resin layer 3, as shown in FIG.
A buffer layer 4 made of yarn or the like is provided to form an optical unit 5. The optical unit 5 is then covered with a sheath 6, and the gap in the buffer layer 4 of the optical unit 5 is filled with jewelry to form the optical cable of the present invention.

In such an optical cable, even if it is subjected to straining during handling, each optical fiber 2 of the optical unit 5 is bonded with the resin layer 3, so that the optical fibers 2...・Each optical fiber 2 is not pushed in between.
... will not be disturbed in the twisted arrangement, and as a result, the transmission characteristics will not deteriorate. Liar, resin layer 3
has a certain degree of flexibility, so each optical fiber 2 of the optical unit 5 is allowed to move to a certain extent, and the effect of twisting the optical fibers 2 is not impaired. . Furthermore, since the gaps between the central body 1 and each optical fiber 2 are also filled with resin, there is no possibility that this portion becomes a passage for water.

Other Specific Structure FIG. 4 shows another example of the optical cable of the present invention. The optical cable of this example consists of six optical fibers 2 twisted together around a central body 1, hardened with a resin layer 3, and two and four optical units 5 each having a buffer layer 4 formed thereon. The intervening quad 7 and the tension member 8 are twisted together and covered with a sheath 6. In this case, the gaps between each optical unit 5.5 and the intervening quads 7 and the sheath 6 and the gaps in the buffer layers 4 of the optical units 5, 5 are filled with jewelry. Even with the optical cable of this example, the same effects as in the previous example can be obtained.

As described in detail, the optical cable of the present invention has one or more optical units formed by twisting optical fibers around a central body and providing a buffer layer thereon in a sheath, and fills the voids in the sheath. Since the optical fiber and the center body of the optical cable filled with jewelery are integrated using thermosetting resin or ultraviolet curing resin, even if the optical cable is squeezed, the movement of the jewelery will cause The twisted arrangement of the optical fibers is not disturbed and transmission loss does not increase. Further, since the gap between the center body and the optical fiber is also filled with resin, this part does not become a passage for water. Furthermore, when the elastic modulus of the resin is t-0, 1 to 3, the resin has appropriate flexibility, does not impair the twisting effect of optical fibers, and can be easily integrated with the resin. There is no accompanying increase in transmission loss of the optical fiber.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing an example of the optical cable of the present invention, Fig. 2 is a graph showing the relationship between the elastic modulus of the resin and the increase in transmission loss due to cable formation, and Fig. 3 is a graph showing the relationship between the elastic modulus of the resin and the increase in transmission loss due to straining. A graph showing the relationship with the amount of increase in transmission loss, FIG. 4 is a cross-sectional view showing another example of the optical cable of the present invention, and FIGS. 5 and 6 illustrate disturbances in the twisted arrangement of optical fibers due to laddering FIG. 5 is a perspective view showing the state before the ladder is applied, and FIG. 6 is a perspective view showing the state after the ladder is applied. 1...Central body, 2...Optical fiber, 3...
...Resin layer, 4...Buffer i, 5...Light unit, 6...Sheath. Figure 1 Figure 4 Figure 2-1M11? M11 Small%J ((kg/mm21$3Fig.

Claims (2)

[Claims] (1) In an optical cable in which one or more optical units made of optical fibers twisted around a central body and a buffer layer provided thereon are disposed inside a sheath, and a gap in the sheath is filled with jewelery, the above-mentioned center An optical cable characterized in that a body and an optical fiber are integrated using a thermosetting resin or an ultraviolet curable resin. (2) The optical cable according to claim 1, wherein the resin has an elastic modulus of 0.1 to 3 kg/mm^2.