JPS62196611A - Non-metallic optical cable - Google Patents

Abstract

PURPOSE:To make it possible to bend a cable having <=300mm radius and to guarantee sufficient reliability even if a non-metallic optical cable is dipped into water by using a specific FRP excellent in the breaking life of bending stress. CONSTITUTION:In the non-metallic optical cable using glass fiber plastic (FRP) obtained by reinforcing thermosetting plastic by glass fiber as a tensile strength substance, the FRP satisfies the conditions of the shown inequality. The deterioration of the intensity of glass fibers will be generated when component substances of the glass fiber are soluble in water and cracks grow. Thereby, it is preferable to use water-insoluble glass fiber, e.g. a glass fiber reducing the contents of element such as Ca, B and Na which are easily soluble in water. Thus, the FRP for non-metallic optical cable tensile strength substance capable of being laid on a position to be easily dipped into water in a manhole or the like can be obtained.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a non-metallic optical cable, and more particularly to a non-metallic optical cable whose cable constituent material does not contain any metal. It relates to non-metallic optical cables that use glass fiber reinforced plastic (hereinafter referred to as FRP), which has excellent breaking life.

[Technical background of the invention]

Cables installed near power lines, electric railways, etc. should be installed with metal objects in their construction materials in order to avoid being affected by the interference electromagnetic fields emitted by the cables. Non-metal optical cables are important for ensuring the safety of people.
Since its constituent materials do not include a metal sheath that does not allow moisture to pass through, the inside of a non-metallic optical cable installed in a location that is likely to be submerged in water may reach a state of 100% humidity. Therefore, in order to realize a highly reliable non-metallic optical cable, it is necessary to ensure the reliability of each constituent material under conditions of 100% humidity.

Glass fiber reinforced plastic, or FRP, is used. However, in a humid environment, the strength of the glass fibers that make up FRP rapidly deteriorates, as well as the adhesive strength between the glass fiber and thermosetting resin and the strength of the thermosetting preform, making FRP more likely to break. There are drawbacks. For this reason, in locations prone to water submergence, steel wires are used as tension members, and optical cables that are maintained through glass have the disadvantage that they can only be bent at a larger radius than optical cables that are maintained through glass.

For example, a non-metallic optical cable in which 24 optical fibers are layered around an FRP requires a 5IIIIIIφ FRP to withstand the tension during installation, but the permissible bending radius of this non-metallic optical cable is 400 mm.
vw (For how to determine the allowable bending radius, see “Method for estimating the lifespan of FRP used in optical cables,” IEICE Theory (B), J68-B, 9
．． PP, 1081-1082: Kuwabara, Mansui, and Koga are in a situation where such non-metallic optical cables cannot be applied because they require the use of cables.

(Summary of the Invention) The present invention has been made in view of the above points, and has discovered an FRP with excellent rupture life against bending stress.
The purpose is to provide a non-metallic optical cable to which P is applied.

Therefore, the non-metal optical cable according to the present invention is a non-metal optical cable that uses glass fiber plastic in which a thermosetting plastic is reinforced with glass fiber as a tensile strength member, and is characterized in that the glass fiber reinforced plastic satisfies the following formula (al). There is.

0.0017 ≧ 1-exp (-1xlO'
(1.7xios/l o ) ') -・--1-
−−・・−−−−−−−・−・−・ (a) (Formula ia above), t and − are the curvature of the glass fiber reinforced plastic in constant temperature and humidity at 20°C and 100% humidity. (The scale parameters and shape parameters of the Weibull distribution obtained by measuring the time until breakage after being left bent at a radius of 300 ++v+ are shown) According to the non-metallic optical cable according to the present invention, the thermosetting plastic has the above formula. (By satisfying al,
It becomes possible to bend the cable with a radius smaller than 300 mm, and there is an advantage that it is possible to realize a non-metallic optical cable that can ensure sufficient reliability even when submerged in water. - [Detailed Description of the Invention] Fig. 1 shows a method of a bending fatigue test for evaluating rupture life against bending stress.

The test is performed by leaving FRP in water with a bending curvature as shown in Figure 1 (a) and measuring the time until it breaks as shown in Figure 1 (011). It is.

An example of this test is shown in FIG. Figure 2 shows the time until FRP breaks plotted on Weibull probability paper, where the horizontal axis is the failure time (1) and the vertical axis is the cumulative failure probability (
FX100'). Also, 11 is humidity,
H=100% indicates immersion in water. T.
is the water temperature, μ is the maximum strain rate applied to the FRP due to bending (hereinafter simply referred to as bending strain rate), and the relationship shown in equation (1) holds true with the radius of curvature.

μ= (d/2R) xlOO−・−・−・−−1−
-------・-(l) In the above formula (1), d is FR
It is the diameter of P.

As is clear from Figure 2, the cumulative failure probability of FRP is expressed as a straight line on Weibull probability paper, regardless of the bending strain rate.
The probability of breakage F of FRP of length L at time t is expressed by the following equation (2) from the above-mentioned "Method for estimating the lifespan of FRP used in optical cables."

F=1−exp(L(t/l6)”
-.---(2) In equation (2), 0 is the shape parameter of the Weibull distribution, and to is the scale parameter of the Weibull distribution.

The Weibull distribution is InIn(11/F)-m(Int-In
to) --(denoted by 31, the left side is Y, In
When t is set as χ, the formula %formula %(4) becomes a straight line.

Therefore, - and to are Y=O=InIn
(1-1/F) and the value of (InIn(1)
-1/F ) = 0, (1-1/F )
-e, F=0.632), which can be determined using equation (3) from the slope of the straight line in FIG. 2 (which can be directly determined from the graph).

The probability of failure of FRP used for the tensile strength body of a non-metallic optical cable can be determined by conducting a fatigue test by varying the bending strain rate and water temperature, as shown in Figure 2, and from the change tendency of the Weibull distribution.
Under the environment where the optical cable is installed (average temperature 20℃,
This can be determined by finding the shape and scale parameters of the Weibull distribution at a humidity of 100 parameters and a radius of curvature of 300 am.

The reliability required for optical cables has increased to 100% in 20 years.
Since the failure probability per Km is 1.7 Xl0-3 or less, it is necessary to make the fracture probability of FRP less than this value.

Equation (2) can be rewritten as follows.

0.0017 ≧ 1-exp (I Xl05(
1.7xtoli/to) ”)------
−−・−・−(a) (However, t□, +w is the time until breakage when glass fiber reinforced plastic is left bent with a radius of curvature of 30011+11 in a constant temperature and humidity environment of 20°C and 100% humidity. (shows the scale and shape parameters of the Weibull distribution obtained by measuring the
In order to realize FRP for non-metallic optical fiber cables that can be installed in places that are easily submerged in water, such as inside manholes, it is necessary to use highly reliable glass fibers and thermosetting plastics that satisfy the above formula (a). Will be using it.

The strength deterioration of glass fibers occurs because the constituent substances of the glass melt into water and cracks grow.

Therefore, it is preferable to use glass fibers that are difficult to dissolve in water. For example, it is desirable to have a low content of elements such as Ca and B%Na, which are easily dissolved in water.

This occurs because part of the resin composition melts in the solution, and when the aqueous solution becomes high temperature, internal defects grow due to the heat. Since these decreases are generally accelerated in high-temperature aqueous solutions, it is desirable that the properties of the resin remain stable even in high-temperature aqueous solutions. Therefore, Ca, B% N
We made various types of FRP using glass fiber with low water solubility such as a, and FRP with high heat resistance, and conducted bending fatigue tests.
The probability of breakage was calculated. The structure of the manufactured FRP is shown in Table 1. In Table 1, Sample No. 1 is the current commercially available FRP product, and Sample No. 2 is FRP in which the resin of the current commercially available product was changed to a resin with high heat resistance. We have found that novolac vinyl ester is the most suitable resin from the viewpoint of properties.

Sample No. 3 is made of glass fiber [E
This is FRP in which glass (JIS-R3412) is replaced with highly reliable glass fiber (hereinafter referred to as T-glass). E
The chemical composition and properties of the glass and T-glass are shown in Table 2 below.

As shown in Table 1, Table 2, and Table 2, T glass is easy to melt in water.C
It is a glass fiber with little strength deterioration due to its low content of as B % K and Na. Furthermore, since T glass has a higher tensile modulus than E glass, if FRPs with the same glass content are produced, FRPs using T glass will have a higher modulus of elasticity than those using E glass.

Table 3 shows the characteristics of the manufactured FRP.

The tensile strength, tensile modulus, bending strength, bending modulus, coefficient of linear expansion, and specific gravity of FRP strongly depend on the properties of glass fiber, so T glass has higher strength and lower specific gravity compared to E glass. The FRP of sample [3] using
It has a high elastic modulus and low specific gravity compared to . In addition, since sample (2) uses the same E glass as the current commercial product, it exhibits the same characteristics as the current commercial product.

This is because if it is less than %, water-soluble components will inevitably be included. In this case, it is of course desirable to use glass containing 100% SiO2, but considering the high cost, glass fibers mixed with 20 to 30% of insoluble Al2O'3 may also be used. Furthermore, a water-soluble component such as MgO may be added in a composition range of 5 to 15%. Further, the tensile strength is preferably 450 Kg/vw2 or more.*If it is less than 450 Kg/++v+2, the strength of the FRP decreases, which is not preferable. Furthermore, the tensile modulus is preferably 8,000 Kg/+u+" or more. If it is less than 8,000 Kg/tava2, the elasticity of FRP may decrease and the allowable bending radius may increase. Furthermore, the specific gravity is 2. It is better if it is 6 or less.2
．． This is because if it exceeds 6, there is a risk that the FRP will become too heavy.

By the way, the T glass mentioned above is SiO* 80-70%,
It has a composition of Alz 0320-30% and Mg 05-15%, and has a tensile strength of 450-550 kg/ss+2. The tensile modulus is 8000-9000 kg/n+n+2, and the specific gravity is 2.4-2.6.

Further, the volume content of glass fiber is preferably 50 to 8
It is preferable that it be 0%. If less than 50%, CaCO3
It is common to add fillers such as fillers, which may worsen the rupture life against bending stress.On the other hand, if it exceeds 80%, it becomes impossible to maintain the longitudinal uniformity of the glass fibers, so it also increases the bending stress. This is because the rupture life of the steel deteriorates.

FIG. 3 shows the FRP bending fatigue test results for samples [1] to [3]. As is clear from the figure, the sample with improved resin [2
] and sample [3] with improved glass fibers have a longer rupture life against bending stress compared to current commercially available products. This shows that a non-metallic optical cable can be realized.

Table 3 Example 1 Figure 4 is a diagram explaining the first example according to the present invention, in which 1 is composed of E glass and novolac vinyl FRP, which corresponds to the FRP of sample [2]. FRP tensile strength body, 2 is plastic sheath, 3 is 2 assembled in layers
There are four optical fiber cores, and 4 is a plastic jacket.

Table 4 shows the characteristic values of this example.

In order to satisfy the allowable tension (the tension at 0.2% elongation is greater than the weight of the cable I Km) to withstand the installation, FRP of 511IIlφ is required, similar to the current commercially available product. At this time, when the allowable bending radius of the current commercially available product is determined from the bending fatigue test, it is 400 mm, which means that it cannot be installed in locations that are easily submerged in water such as inside manholes, but the allowable bending radius of the FRP used at zero time is determined. and 300 mm,
It was found that it is possible to install it inside manholes, etc.

Example 2 FIG. 5 shows a second example according to the present invention, and 5 is an FRP tensile strength body composed of T glass and urethane acrylate vinyl FRP corresponding to sample [3] in Table 3. . The characteristic values of this example are shown in Table 4 below.

In this example, as shown in Table 3, FRP with a higher tensile modulus than the currently commercially available product is used, so FRP with a diameter of 4 nunφ is sufficient to satisfy the allowable tension. The permissible bending radius of this FRP was determined from the bend fatigue test and was 2001, which was sufficient to allow installation in manholes, etc.

In addition, the bending composition of this example is about half that of current commercially available products,
By using the FRP used in this example as a tensile strength member, there is an advantage that a non-metallic optical cable that is easy to bend can be realized.

Example 3 FIG. 6 shows a third example according to the present invention, and 6 is a sample [
This is an FRP tensile strength body made by loosely combining FRPT sheets made of T-glass glass fiber and urethane acrylate vinyl resin corresponding to 3].

Conventional FRP has a low tensile modulus, so the structure of this example could not satisfy the allowable tension, but this structure was made possible by using FRP with a high tensile modulus. The characteristics of this example are shown in Table 4 below. In this example, an FRP tensile strength member with a smaller diameter of 1.6 mtsφ is used than in Example 1, so the allowable bending radius is 80*a+
becomes. In addition, the bending rigidity of this example is the same as that of the current commercially available product.
It is 1/75th of the non-metal optical cable using RP,
The structure of this embodiment has the advantage that it is possible to realize a cable that is very easy to bend.

Table 4 ■ [ [ [ Product for sale, Example 1.2.3, respectively, 7.4 Xl0-7
．． 2.7 Xl0-”, 3.2 Xl0-5.3.2
It was Xl0-5.

That is, since the allowable bending radius of Example 1 is approximately 300 mm, F* corresponds to F in formula (a). ) becomes 1. Moreover, F in Example 2 and Example 3 is close to 0. In any case, the current commercially available products are
Although the formula (al) is not satisfied, Examples 1 to
It can be seen that 3 satisfies the above formula (a).

Embodiment 4 FIG. 7 shows the fourth embodiment of the present invention, in which 9 is FRP.
The optical unit 7 is an ester tensile strength body made of T-glass glass fiber and urethane acrylate diameter vinyl ester, which corresponds to sample [3] in Table 3, and has optical fiber core wires 3 gathered around a unit center member 8. Table 5 below shows the characteristic values of this example. In Table 5, the resistance of the current commercial product is the characteristic when the current commercial product is used as the ester tensile strength body 7.

As shown in Table 5, FRP using T-glass as the glass fiber is used as the tensile strength member, compared to the case where the current commercial product is used as the tensile strength member.

When used, both the allowable bending radius and bending rigidity are small, and by using the FRP used in this example as a tensile strength member, a unit 7 type non-metallic optical cable with a small allowable bending radius and easy bending can be realized.

In the above embodiment, FR for non-metallic optical cable tensile strength body is used.
FRP using novolak vinyl ester resin as P and T glass as glass fiber
However, by using both, a non-metallic optical cable with an even smaller bending radius can be realized.

Table 5 [Effects of the Invention] As explained above, the allowable bending radius of the FRP tensile strength member of a non-metallic optical cable determined from a bending fatigue test is 30
FRP with a thickness of 0 mm or less, specifically FR using novolak vinyl ester with good heat resistance as a thermosetting resin
By using FRP or FRP using both as a tensile strength member of a non-metallic optical cable, a non-metallic optical cable that can be installed in locations that are easily submerged in water, such as existing manholes, can be realized.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the method of bending fatigue test of FRP,
FIG. 2 is a diagram showing the results of a bending fatigue test of FRP. Figure 3 is a diagram showing the results of bending fatigue tests for samples (1) to (3);
4 is a cross-sectional view of the first embodiment of the present invention, FIG. 5 is a cross-sectional view of the second embodiment of the present invention, FIG. 6 is a cross-sectional view of the third embodiment of the present invention, and FIG. The figure is a sectional view of a fourth embodiment according to the present invention. 1... FRP tensile strength body made of E-glass glass fiber and novolac vinyl ester, 2... Plastic sheath, 3... 24 assembled around the FRP tensile strength body
Shinkou fiber core, 4...Plastic jacket, 5...
・FRP tensile strength body made of T-glass glass fiber and urethane acrylate vinyl ester, 6...FRP tensile strength body made of T-glass glass fiber and FRPT book made of urethane acrylate vinyl ester, 7.
...FRP tensile strength body made of T-glass glass fiber and urethane acrylate vinyl ester, 8...FRP
Unit center member, 9...An optical unit in which optical fiber core wires are gathered around the FRP unit center member. Applicant's representative: Masaki Amemiya Figure 1 FRP
ur) q 3 ``3 FRp171yyRosx Shunkokusen B Aoma (hour) Figure 4 Figure 5 Figure 6 Figure 7 Procedure amendment '-J' (帥暉佃1年4月4日1、、、んCommissioner of the Patent Office Michibe Uga1, Indication of the case, Patent Application No. 039828 of 19852, Name of the invention, non-metallic optical cable3, Person making the amendment Relationship to the case Patent applicant address: 1-chome Uchisaiwai-cho, Chiyoda-ku, Tokyo No. 1 No. 6 Name (first name, fH (422) Nippon Telegraph and Telephone Corporation 4, agent 102 Tochi 03-264-3566 (Shipping date: Showa year, month, day) 7. Contents (1) Specification page 8 Line 15 “105 seconds” is changed to “10
Corrected to ``5 hours''.

Claims (3)

[Claims] (1) A non-metallic optical cable using glass fiber plastic, which is a thermosetting plastic reinforced with glass fiber, as a tensile strength member, wherein the glass fiber-reinforced plastic satisfies the following formula (a). 0.0017≧1-exp{-1×10^5(1.7×
10^5/t_0)^m}......(a) (In the above formula (a), t_0 and m are glass fiber reinforced plastics bent with a radius of curvature of 300 mm at a constant temperature and humidity of 20°C and 100% humidity. (The scale parameters and shape parameters of the Weibull distribution obtained by leaving the specimen in the same state and measuring the time until rupture) (2) The glass fiber used in the glass fiber reinforced plastic contains 60% or more of SiO_2, has a tensile strength of 450 kg/mm^2 or more, and has a tensile modulus of 8000 kg.
2. The non-metallic optical cable according to claim 1, wherein the non-metallic optical cable has a specific gravity of 2.6 or less and a specific gravity of 2.6 or less. (3) The non-metallic optical cable according to claim 1 or 2, wherein the thermosetting plastic used for the glass fiber reinforced plastic is novolac vinyl ester.