JPH0668570B2 - Optical fiber core - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an optical fiber core wire having an improved secondary coating layer.

(Technical Background of the Invention) FIG. 7 shows a conventional optical fiber core wire 1, which is provided with an optical fiber element wire 2 obtained by melting and spinning a preform rod. The optical fiber strand 2 is covered with a primary coat 3 for protecting the optical fiber strand 2 from scratches and the outside air after spinning, and a buffer coat 4 for improving transmission characteristics is provided thereon. It is covered. The primary coat 3 and the buffer coat 4 are referred to as a primary coating layer 5, and are made of a thermosetting resin such as silicone resin. Then, a secondary coating layer 6 is provided on the primary coating layer 5 in order to prevent the optical fiber element wire 2 from being broken or its transmission characteristics being deteriorated due to an external force, a temperature change, or the like. . The secondary coating layer 6 is formed of a thermoplastic resin such as polyamide resin or high density polyethylene (hereinafter referred to as HDPE).

(Problems of Background Art) By the way, in the optical fiber core wire having the secondary coating layer 6 made of a polyamide resin, the coefficient of linear expansion of the polyamide resin is about 11.4 × 10 ⁻⁵ [° C. ⁻¹ ] which is relatively high. Since it is large, microbending occurs at about −20 ° C. and transmission loss increases. Therefore, conventionally, when the optical fiber core wire 1 is formed into a cable, for example, a steel wire or a glass fiber reinforced plastic rod having a small linear expansion coefficient is used as a tension member, and the optical fiber core wire 1 is attached to the tension member. Winding, optical fiber strand 2
The shrinkage stress generated due to the difference in linear expansion coefficient between the secondary coating layer 6 and the secondary coating layer 6 is absorbed. However, this also increases the transmission loss of the optical fiber core at -40 ° C or higher.

In addition, in the optical fiber core wire 1 having the secondary coating layer 6 made of polyamide resin, 100% of the polyamide resin is used.
Since the heat shrinkage amount at 24 ° C. for 24 hours is about 1.33%, the secondary coating layer 6 shrinks due to the residual strain during processing and the progress of crystallization in a high temperature atmosphere, and the transmission loss occurs at about 60 ° C. Will increase. Therefore, when an optical fiber cable is manufactured using the optical fiber core wire 1 having the secondary coating layer 6 made of polyamide resin, the usable temperature range is limited to about -40 ° C to 60 ° C.

Furthermore, the Young's modulus of polyamide resin is 127 kg at 25 ° C.
/ Mm ^2, 165kg / mm ² at -20 ° C., also the yield stress is because 4.15 kg / mm ^2, the rigidity ratio is relatively small, and therefore, an optical fiber having a secondary coating layer 6 made of a polyamide resin In the core wire, lateral pressure causes a significant increase in transmission loss.

Next, HDPE has a linear expansion coefficient and a heat shrinkage of 16.
3 × 10 ⁻⁵ [° C. ⁻¹ ] and 3.0%, and Young's modulus and yield point stress are 87 kg / mm ² and 2.24 kg.
Since it is as small as / mm ² , the operating temperature range is further limited in the optical fiber core wire having the secondary coating layer made of HDPE,
Moreover, lateral pressure greatly increases the transmission loss.

Recently, an optical fiber core wire having a glass fiber reinforced plastic having a large rigidity, a small linear expansion coefficient and a small heat shrinkage amount as a secondary coating layer has been proposed, but this glass fiber reinforced plastic is a thermosetting resin. Therefore, the optical fiber element wire cannot be extrusion-coated, which causes a problem in manufacturing and is very expensive. Further, when the strength is improved by using the glass fiber reinforced plastic, the thickness of the secondary coating layer needs to be secured to some extent, so that the outer diameter of the optical fiber core becomes large.

(Object of the Invention) An object of the present invention is to provide an optical fiber core wire having a secondary coating layer that has a small diameter, a large rigidity, a small linear expansion coefficient and a small heat shrinkage, and is easy to manufacture. Especially.

(Summary of the Invention) According to the present invention, a secondary coating layer is provided on a primary coating layer of an optical fiber element by using a polyamide resin containing 10 to 40% by weight of potassium titanate or a thermoplastic resin made of high-density polyethylene. It is characterized by that.

As the potassium titanate, fibrous potassium hexatitanate (K ₂ O.6TiO ₂ ) was used, and the potassium hexatitanate fiber was added to the polyamide resin and the HDPE at different filling amounts to obtain the secondary Using the coating material as a sample, the Young's modulus in tension with respect to the filling amount of potassium hexatitanate fiber (tensile speed 5 mm / min), linear expansion coefficient {(TMA);
-30 ° C to 30 ° C} and the amount of heat shrinkage (100 ° C, 24 hours) were measured, and the results shown in Figs. 4, 5, and 6 were obtained. That is, in the secondary coating material made of polyamide resin, as shown in (A) in the figure, the Young's modulus increases as the filling amount of potassium hexatitanate fiber increases, and the linear expansion coefficient and the heat shrinkage amount decrease. is doing. When 15 wt% and 30 wt% of potassium hexatitanate fiber is filled, Young's modulus is about 3 times and about 4 times, coefficient of linear expansion is about 1/3 and about 1/5, and heating is performed. Shrinkage is about 1
It has changed to / 4 and about 1/20. The secondary coating material made of HDPE also changed in the same manner as shown by (B) in the figure, and when the potassium hexatitanate fiber was filled at 15% by weight and 30% by weight, the Young's modulus was about 1. 4 times and about 1.8
The coefficient of linear expansion has changed to about 7/8 and about 5/8, and the amount of heat shrinkage has changed to about 2.2 / 3 and about 2/3.

Therefore, by using a polyamide resin containing potassium titanate or high-density polyethylene as a coating material, an optical fiber core wire having a large rigidity and a secondary coating layer having a small linear expansion coefficient and a small heat shrinkage amount can be obtained. be able to. Therefore, even if lateral pressure is applied to the optical fiber core, the transmission loss hardly increases, and even if the optical fiber core is placed in a place where the temperature changes drastically, the transmission loss does not increase.

Embodiments of the Invention Embodiments of the present invention will be described in detail below with reference to the drawings.

Example 1 FIGS. 1A and 1B show optical fiber core wires 7 and 8 according to the present invention, respectively. These optical fiber core wires 7 and 8 are equipped with a graded index type quartz optical fiber element wire 2 obtained by melting and spinning a preform rod. These optical fiber strands 2 and 2 are composed of a core having a diameter of 50 μm and a clad having a diameter of 125 μm. A primary coat 3 and a buffer coat 4 are extrusion-coated on the respective optical fiber strands 2, 2. The primary coat 3 and the buffer coat 4 are made of silicone resin, and the thickness thereof is set so that the outer diameter of the buffer coat 4 is 400 μm, and the primary coating layer 5 is formed. The secondary coating layers 9 and 10 are extrusion-coated on the primary coating layers 5 and 5, respectively. The secondary coating layer 9 of the one optical fiber core wire 7 is made of potassium hexatitanate fiber 1
It is formed from a polyamide resin filled with 5% by weight. In addition, the secondary coating layer 10 of the other optical fiber core wire 8
Is formed of a polyamide resin filled with 30% by weight of potassium hexatitanate fiber. Both secondary coating layers 9
Nos. 10 and 10 are extrusion-coated so that each has an outer diameter of 0.9 mm.

Comparative Example In the optical fiber core wire of the embodiment shown in FIG. 1 above, the secondary coating layer was formed only from polyamide resin.

Now, in order to investigate the low-temperature transmission characteristics of both the optical fiber cores 7 and 8 of the above-mentioned example and the optical fiber cores of the comparative example, these optical fiber cores are placed at a temperature of 20 ° C. for 5 hours. Each time the temperature was lowered by 10 ° C., the increase in transmission loss of each optical fiber core wire was measured in the temperature range from 0 ° C. to −50 ° C. An LED with a wavelength of 860 nm and an optical power meter were used for the measurement. The measurement results are shown in Table 1.

In Table 1 above, the increase in transmission loss of the optical fiber core wire of the comparative example is 0.05 dB at -20 ° C and 0.1 dB at -30 ° C.
It is 5 dB and 0.70 dB at -40 ° C. On the other hand, the optical fiber core wire 7 of the present embodiment [FIG. 1 (A)]
The increase in transmission loss was 0.05 dB at -40 ° C and 0.15 dB at -50 ° C. In addition, the increase in transmission loss of the optical fiber core wire 8 [FIG. 1 (B)] of the present embodiment is 0.
It was 05 dB and 0.13 dB at -50 ° C. As described above, the low-temperature transmission characteristics of the optical fiber core wires 7 and 8 of this embodiment are remarkably improved as compared with the conventional one, and it can be understood that the optical fiber core wires 7 and 8 can be sufficiently used even at -50 ° C or higher. Since a polyamide resin filled with potassium hexatitanate fibers was used as the secondary coating layers 9 and 10, the linear expansion coefficient of the secondary coating layers 9 and 10 was small, and microbending hardly occurred even at low temperatures. It is thought that it depends.

Next, the result of examining the high-temperature transmission characteristics of both the optical fiber core wires 7 and 8 of the above-mentioned embodiment and the optical fiber core wires of the comparative example is the second result.
Shown in the table. In this high temperature transmission characteristic test, 60 ° C and 80 ° C
The increase in transmission loss at room temperature (25 ° C.) after standing for 24 hours at each temperature was measured. The same light source and power meter as described above were used for the measurement.

As is apparent from Table 2 above, the increase in transmission loss of the optical fiber core wire of the comparative example is 0.0 when left at 60 ° C.
When left at 5 dB and 80 ° C., it was 0.4 dB. On the other hand, the optical fiber core wires 7 and 8 of the embodiment are 6
The transmission loss did not increase even when left at 0 ° C. and 80 ° C. It is considered that this is because the amount of heat shrinkage of the secondary coating layers 9 and 10 is extremely small, and therefore micro-bending hardly occurs even at high temperature.

Further, Table 3 shows the results of examining the lateral pressure characteristics of both the optical fiber core wires 7 and 8 of the above-mentioned example and the optical fiber core wires of the comparative example. In this lateral pressure characteristic test, each optical fiber core wire is # 3.
The transmission loss increase of each optical fiber core wire when a load (side pressure) of 20 kg / 30 cm × 2 was applied was measured by sandwiching it with 0 sandpaper. For the measurement, the same light source and optical power meter as described above were used.

As is clear from Table 3 above, in the optical fiber core wire of the comparative example, the increase in transmission loss is very large at 0.42 dB. On the other hand, in the optical fiber core wires 7 and 8 of the embodiment, the transmission loss increase is 0.15 dB and 0.08 d.
It is not so big as B.

By the way, a tensile test was conducted on both the optical fiber cores 7 and 8 of the above-mentioned example and the optical fiber cores of the comparative example. Material length is 300mm, number of samples is 20, each pulling speed is 100mm / min.
The test temperature was 22 ° C. and the humidity was 55%. The results of this tensile test are shown in Table 4.

As is clear from Table 4 above, the average value of the breaking load in the optical fiber core wire of the comparative example is 8.1 kg, and the average value of the breaking load in the optical fiber core wires 7 and 8 of this example is 8.40 kg, respectively. And 8.60 kg. It is considered that the difference between the breaking loads of the core wires of Comparative Example and Example of 0.30 kg and 0.50 kg is due to the fact that the secondary coating layers 9 and 10 were reinforced by the potassium hexatitanate fiber. From the test results in Table 4 above, it can be seen that the rigidity of the secondary coating layers 9 and 10 is large. Therefore, the optical fiber core wire 7 of the present embodiment,
Since No. 8 has improved lateral pressure resistance, as shown in Table 3, the increase in transmission loss does not increase so much even when lateral pressure is applied.

In the above-mentioned examples, the potassium hexatitanate fiber is filled in the polyamide resin at a ratio of 15% by weight and 30% by weight, but the filling amount can be changed in the range of 10% by weight to 40% by weight. % Or less, the secondary coating layer 9
Or, the linear expansion coefficient, the heat shrinkage amount and the rigidity of 10 are almost the same as those of the conventional secondary coating layer composed only of polyamide resin, and when it is 40% by weight or more, the extrusion operation of the secondary coating layer becomes difficult. I will end up.

In addition, although the potassium hexatitanate fiber was used in the said Example, the same effect can be obtained even if potassium dititanate fiber, potassium tetratitanate fiber, etc. are used.

Further, since only a thermoplastic resin such as a polyamide resin is filled with potassium titanate, there is an advantage that the secondary coating layer 9 or 10 can be arbitrarily colored.

Example 2 HDPE filled with 15% by weight of potassium hexatitanate,
HDPE filled with 30% by weight of potassium hexatitanate was extrusion-coated on the primary coating layer on the optical fiber strand shown in Example 1, respectively, to thereby provide an optical film having an HDPE secondary coating layer containing 15% by weight of potassium hexatitanate. A fiber core,
An optical fiber core having an HDPE secondary coating layer containing 30% by weight of potassium hexatitanate was obtained.

Each HDPE of these optical fiber core wires has a linear expansion coefficient, a heat shrinkage amount, and a Young's modulus at a filling amount of 15 wt% and 30 wt% as shown in (B) of FIGS. 4 to 6. Have Therefore, these optical fiber cores are HDPE
It can be seen that lateral pressure resistance, low-temperature transmission characteristics, and high-temperature transmission characteristics are superior to those of the optical fiber core wire having the secondary coating layer made of only.

FIG. 2 (A) shows an optical fiber cable according to an application example of the present invention. That is, the optical fiber cable includes a tension member 11 located at the center, and the tension member 11 is made of glass fiber reinforced plastic. Six optical fiber core wires 8 ′ are wound around the circumferential surface of the tension member 11 via intervening cords 12. These optical fiber core wires 8'has the same structure as the optical fiber core wire 8 shown in FIG. 1 (B), and has a secondary coating layer 10 'made of a polyamide resin containing 30% by weight of potassium hexatitanate fiber. is doing. The intervening string 12 is made of polypropylene, quinol or Kevlar (trade name of Du PONT). A press winding 13 is provided on the interposing cord 12 and the optical fiber core wire 8 ′, and an outer cover 14 made of polyethylene is extrusion-coated directly on the press winding 13.

By the way, FIG. 2 (B) shows a conventional optical fiber cable of this type. That is, the tension member 11
A secondary coating layer 1 made only of polyamide resin on the peripheral surface of
An optical fiber core wire 15 having 5a is wound together with the interposition 12, and a cushion layer 16 is provided on the presser winding 13. Then, the presser wrap 1 is provided on the cushion layer 16.
A jacket 14 made of polyethylene is extrusion-coated via 3 '. The cushion layer 16 is made of the same material as the interposing cord 12, absorbs the molding strain of the jacket 14 and the external force applied to the cable itself, and the optical fiber core wire 15 of the conventional structure.
It prevents the lateral pressure from being applied to. The cushion layer 16 is also used as a heat insulating material that prevents the secondary coating layer 15a of the optical fiber core wire 15 from being heated and contracted when the jacket 14 is extruded.

On the other hand, the optical fiber cable of the present invention shown in FIG. 2 (A) has a Young's modulus about four times that of the conventional one,
The secondary coating layer 1 has a heat shrinkage of about 1/20 of that of the conventional one.
Since the optical fiber core wire 8'containing 0'is used, the cushion layer 16 is not necessary, and therefore the jacket 14 is directly provided on the presser winding 13 as described above. Therefore, the outer diameter of the cable can be reduced, and the cushion layer 16 and the presser winding 13 are not required.
The material cost is low and the optical fiber cable can be provided at low cost. Further, when the cushion layer 16 is used as in the conventional case, the cushion layer 16 itself contracts due to the influence of the heat received during the extrusion of the jacket 14 and the heat in the high temperature atmosphere,
Lateral pressure is applied to the optical fiber core wire 15. However, since the cushion layer 16 is not used in the optical fiber cable of the present invention, such a problem does not occur, and therefore, the lateral pressure by the cushion layer 16 does not increase the transmission loss.

FIG. 3 (A) shows an example in which the present invention is applied to a unit type optical fiber cable. That is, in this optical fiber cable, a plurality of optical units 17 are wound around the circumferential surface of the tension member 11 together with the intervening quads 12 'and the gas pipes 18, and an outer cover made of polyvinyl chloride is provided on them with a press winding 13'. The object 14 'is extrusion coated. Each optical unit 17 has a small diameter tension member 11
It consists of six optical fiber core wires 8'wound around the peripheral surface of a and a presser winding 13a wound on these optical fiber core wires 8 '. Each optical fiber core wire 8'has a secondary coating layer 10 'made of a polyamide resin containing 30% by weight of potassium hexatitanate fiber.

For comparison, FIG. 3 (B) shows a conventional optical fiber cable of this type. That is, since the conventional optical fiber cable of this type uses the optical fiber core wire 15 having the secondary coating layer 15a made of only polyamide resin,
A cushion layer 16 'is provided on these optical fiber core wires 15 via a presser winding 13a.
Another presser winding 13b is provided on 6 ', which constitutes an optical unit 17'.

(Effect of the Invention) According to the present invention, since the secondary coating layer is formed from a polyamide resin containing potassium titanate or a thermoplastic resin made of high-density polyethylene, the production is easy, and the wall thickness is not increased. Even though it has rigidity, an optical fiber core wire having a secondary coating layer having a small coefficient of linear expansion and a small amount of heat shrinkage can be obtained. Therefore, when the optical fiber core wire of the present invention is used, an optical fiber cable having excellent lateral pressure resistance and temperature resistance can be manufactured. Further, when the optical fiber cable is manufactured using the optical fiber core wire of the present invention, the cushion layer is not necessary, so that not only can the diameter of the optical fiber cable be reduced, but also the material cost can be reduced. Very economical.

[Brief description of drawings]

1 (A) and 1 (B) are perspective views showing an optical fiber core wire according to the present invention, and FIGS. 2 (A) and 3 (A) are optical fiber core wires of FIG. 1 (B). 2B and 3B are cross-sectional views showing a conventional optical fiber cable, respectively, and FIGS. 4 to 6 are Young's modulus and linear expansion. FIG. 7 is a characteristic view showing the relationship between the coefficient and the heat shrinkage amount and the potassium hexatitanate fiber filling amount, and FIG. 7 is a perspective view showing a conventional optical fiber core wire. 1, 7, 8 ... Optical fiber core wire, 8 ', 15 ... 〃 2 ... Optical fiber element wire, 5 ... Primary coating layer, 9, 10, 10' ... Secondary coating layer.

Continuation of front page (56) Reference JP-A-60-170809 (JP, A) JP-A-60-107607 (JP, A) JP-A-60-107608 (JP, A)

Claims (2)

[Claims] 1. An optical fiber core wire in which a primary coating layer and a secondary coating layer are provided in this order on an optical fiber element wire, wherein the secondary coating layer contains potassium titanate in an amount of 10 to 40.
An optical fiber core wire, which is a thermoplastic resin composed of a polyamide resin or high-density polyethylene that is contained in a weight percentage. 2. The optical fiber core wire according to claim 1, wherein the potassium titanate is fibrous.