JP2000155243A - Optical fiber single conductor and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical fiber single conductor which has good temp. characteristics and high strength against pressure on the side face at normal temp. and which can suppress in crease in the loss due to pressure on the side face. SOLUTION: A soft layer of a UV-curing resin coating 2 and a hard layer of UV-curing resin coating 3 are applied on an optical fiber 1 to constitute a coated optical fiber wire 6 having about 250 μm outer diameter. Then a thermoplastic resin coating 5 is applied on the coated optical fiber wire 6 to constitute an optical fiber single conductor 7 having about 500 μm outer diameter. The Young's modulus of the thermoplastic resin coating 5 at normal temp. is >=0.1 GPa. The surface roughness of the face of the thermoplastic resin coating 5 to the coated optical fiber wire 6, namely, of the inner surface of the coating 5 is <=0.5 μm arithmetic average roughness Ra.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single optical fiber and a method for manufacturing the same.

[0002]

2. Description of the Related Art A single optical fiber is processed into an optical cable or an optical cord, and is particularly used in a communication station or a premises where a wiring operation is repeatedly performed. Used for wiring in

Conventionally, various types of single-core optical fiber have been proposed. However, since a large number of optical cords are gathered in the above-mentioned places, the wiring space is narrow and complicated. The optical cables and optical cords used are required to be thin and flexible, and the jackets of the optical cords and optical cables have become thinner and more flexible. In addition, as an optical fiber single-core fiber, a small-diameter optical fiber single-core fiber having an outer diameter of 500 μm has been developed which does not cause a loss change due to a change in ambient temperature even when housed in such a small-diameter optical cord or optical cable. Have been.

As an example of such an optical fiber single fiber,
There is an optical fiber single core wire described in JP-A-10-115736. This single-core optical fiber is obtained by coating an optical fiber having an outer diameter of 250 μm with a jacket made of a thermoplastic resin to have an outer diameter of 500 μm.

On the other hand, as described above, since the single-core optical fiber used for the above-described purpose other than the temperature characteristic is used in a place where the wiring operation is repeated, after the cable is laid, other communication paths are installed. Wiring operations such as changing and changing are frequently performed, and the optical cord or optical cable containing the single optical fiber is stepped on in the trough, and the lateral pressure is applied when the optical cord is laid under another cable There are many dangers.

However, the prior art single-core optical fiber has a Young's modulus of -60 ° C. at −20 ° C. in order to suppress the deterioration (increase in loss) of transmission characteristics at low temperatures of transmission loss.
A resin having a weight of kgf / mm ² (0.59 GPa) or less is used as a jacket. As an example of the resin, an ultraviolet curable resin such as urethane acrylate is cited. In the prior art invention, by reducing the Young's modulus of the jacket, the shrinkage stress of the jacket when placed at low temperature is reduced,
As a result, the strain applied to the optical fiber is reduced to prevent an increase in transmission loss at low temperatures. That is, as for the Young's modulus, the upper limit is specified as described in “Resin of 60 kg / mm ² or less”, and it is disclosed that the Young's modulus is low, that is, a soft resin is used. I have. For this reason, the Young's modulus of the jacket at the normal use temperature must be reduced.

[0007] The inventors have found that several commercially available
When a resin having a Young's modulus of 60 kgf / mm ² (0.59 GPa) or less at 20 ° C. was examined, the Young's modulus at 20 ° C. was 0.08 GPa or less. For this reason, the strength of the single-core optical fiber (comparative example 5 to be described later) with respect to the lateral pressure at room temperature is low, and when the lateral pressure is applied by stepping on the wiring operation, a remarkable increase in loss occurs. The work was complicated and required skill.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has an excellent temperature characteristic, a high strength against lateral pressure at room temperature, and a reduction in loss with respect to lateral pressure. It is an object of the present invention to provide an optical fiber single fiber having a structure capable of performing the above-mentioned, and a method for manufacturing the same.

[0009]

According to the first aspect of the present invention, a thermoplastic resin is concentrically extruded and coated around an optical fiber coated with an ultraviolet curable resin having an outer diameter of about 250 μm. An optical fiber single-core wire having an outer diameter of approximately 500 μm, wherein the thermoplastic resin has a Young's modulus at room temperature of 0.1 GPa or more, and the optical fiber in the thermoplastic resin coating layer of the single-core optical fiber; The surface roughness of the surface in contact with the strand is 0.5 μm in arithmetic average roughness Ra.
m or less.

The invention according to claim 2 has an outer diameter of about 250 μm.
m, a thermoplastic resin is extruded concentrically around an optical fiber coated with an ultraviolet curable resin to form an outer layer coating, and a method for producing an optical fiber single core wire having an outer diameter of about 500 μm. The optical fiber is heated to 200 ° C. or more immediately before extruding and coating the thermoplastic resin.

According to a third aspect of the present invention, the outer diameter is approximately 250 μm.
m, a thermoplastic resin is extruded concentrically around an optical fiber coated with an ultraviolet curable resin to form an outer layer coating, and a method for producing an optical fiber single core wire having an outer diameter of about 500 μm. The optical fiber is vacuum-dried in a heated state, and then extruded and coated with the thermoplastic resin.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have studied an optical fiber single-core wire using a thermoplastic resin having a high Young's modulus as a sheath, and found that an increase in loss at a low temperature occurs only in the shrinkage stress of the jacket. Instead, it was found that the stress was generated as a result of discontinuously applied to the optical fiber, and that the cause of the discontinuous stress was due to irregularities on the inner surface of the thermoplastic resin in contact with the optical fiber.

FIG. 1 shows a first optical fiber single fiber of the present invention.
FIG. 3 is a cross-sectional view for describing the configuration of the embodiment. In the figure, 1 is an optical fiber, 2 is a soft ultraviolet curing resin coating, 3 is a hard ultraviolet curing resin coating, 5 is a thermoplastic resin coating, 6 is an optical fiber, and 7 is an optical fiber single core. Line.

An optical fiber 1 is coated with a soft ultraviolet curing resin coating 2 and a hard ultraviolet curing resin coating 3 concentrically on the optical fiber 1 and has an outer diameter of about 250 μm. 6 are constituted. This optical fiber 6
Is coated concentrically with a thermoplastic resin coating 5 to form an optical fiber single core wire 7 having an outer diameter of approximately 500 μm. The Young's modulus of the thermoplastic resin coating 5 at room temperature is
It is 0.1 GPa or more. The surface of the thermoplastic resin coating 5 that is in contact with the optical fiber 6, that is, the inner surface has a surface roughness of 0.5 μm or less in terms of arithmetic average roughness Ra.

By setting the Young's modulus of the thermoplastic resin coating 5 at room temperature to 0.1 GPa or more, it is possible to suppress an increase in loss in lateral pressure characteristics and obtain good mechanical characteristics. The surface roughness of the surface of the thermoplastic resin coating 5 in contact with the optical fiber 6 is calculated as an arithmetic mean roughness Ra of 0.1.
When the thickness is 5 μm or less, it is possible to suppress an increase in transmission loss at a low temperature even though the thermoplastic resin coating 5 having a large Young's modulus is applied.

FIG. 2 shows the second embodiment of the optical fiber single fiber of the present invention.
FIG. 3 is a cross-sectional view for describing the configuration of the embodiment. In the figure, the same parts as those in FIG. 4 is a coloring layer. In this embodiment, the optical fiber 6 is obtained by applying the colored layer 4 on the optical fiber 6 of the first embodiment. Although the colored layer 4 is a thin layer, the outer diameter of the optical fiber 6 to which the colored layer 4 is applied is also approximately 250 μm. The thermoplastic resin coating 5 is the same as the thermoplastic resin coating 5 of the first embodiment.
Can exhibit the same characteristics as those of the single optical fiber 7 of the first embodiment.

As described above, by suppressing the surface roughness of the inner surface of the thermoplastic resin-coated optical fiber in contact with the optical fiber, the transmission loss of the optical fiber at a low temperature can be reduced by 0.10.
It succeeded in making it equal to or less than dB / km. In other words, the inventors have found that the roughness of the inner surface of the thermoplastic resin is caused by volatile components such as moisture contained in the coating material of the optical fiber being volatilized during the coating of the thermoplastic resin. Was. Based on the investigation of the cause, a manufacturing method capable of reducing the surface roughness by coating the surface of the optical fiber with a thermoplastic resin while removing volatile components from the surface has been developed.

FIG. 3 is a schematic diagram of a manufacturing apparatus for explaining a first embodiment of the method for manufacturing a single optical fiber of the present invention. In the drawing, 6 is an optical fiber, 7 is a single optical fiber, 11 is an optical fiber supply reel, 1
2 is a heater, 13 is an extruder, 14 is a crosshead, 1
5 is a cooling water tank and 16 is a take-up reel.

The optical fiber 6 covered with an ultraviolet curable resin having an outer diameter of about 250 μm is continuously supplied from an optical fiber supply reel 11 and heated by a heater 12. The heating temperature is 200 ° C. or higher. By this heating, volatile components in the coating material of the optical fiber 6 are removed. In this state, the cross-head 14 covers the thermoplastic resin extruded from the extruder 13. Thereafter, the optical fiber single core wire 7 cooled and cooled in the cooling water tank 15 is wound around a take-up reel 16.

FIG. 4 is a schematic configuration diagram of a manufacturing apparatus for explaining a second embodiment of the method for manufacturing a single optical fiber of the present invention. In the drawing, 6 is an optical fiber, 7 is a single optical fiber, 11 is an optical fiber supply reel, 1
4 is a crosshead, 16 is a take-up reel, 17 is a resin tank, and 18 is a vacuum dryer.

The optical fiber 6 coated with an ultraviolet curable resin having an outer diameter of about 250 μm is dried by a vacuum dryer 18 to remove volatile components before coating with a thermoplastic resin. Drying in the vacuum dryer 18 is performed in a heated state, but in an example, before extrusion, -23 mmH
g and heated to 60 ° C. and dried for 8 hours. Optical fiber wire supply reel 11 taken out from vacuum dryer 18
Is set, and the optical fiber 6 is covered with the thermoplastic resin extruded from the resin tank 17 by the crosshead 14,
The single optical fiber 7 is wound by a winding reel 16.

The effect of heating the optical fiber and vacuum drying on the surface roughness of the inner surface of the thermoplastic resin coating was examined. Heat treatment is 2
00 ° C, 2 seconds, vacuum drying process, vacuum evacuation 20 ~ 2
Although it is 5 mmHg, in the example, it is -23 mmHg and 6 mmHg.
Heated to 0 ° C. and performed for 8 hours. The surface roughness of the inner surface of the thermoplastic resin coating is determined by separating the thermoplastic resin coating and the optical fiber strand from the single optical fiber, and calculating the arithmetic average roughness Ra in the axial direction along the inner surface of the thermoplastic resin coating. Was measured. The experimental results are shown in FIG. In comparison with a comparative example in which neither heat treatment nor vacuum drying treatment was performed, Example 1 in which vacuum drying treatment was performed, Example 2 in which heat treatment was performed, and Example 3 in which both treatments were performed, all had surface roughness. You can see that it is small and smooth.

FIG. 6 shows the measurement results of the prototype optical fiber single fiber. The Young's modulus was determined as a secant Young's modulus from a stress generated in an elongation state of 2.5% according to a plastic tensile test method JIS K7113-1995. The surface roughness of the inner surface of the coating was represented by the arithmetic average roughness Ra when the cut-off value was 0.8 mm and the evaluation length was 4 mm according to JIS B0601-1994. The lateral pressure characteristics were obtained by applying a load of 50 kg to a 100 mm section of a single fiber optical fiber having a light source having a wavelength of 1.55 μm at one end and a light receiver at the other end, before and after the load was applied. The ratio of the amount of light transmitted was measured. Low-temperature transmission loss has a wavelength of 1.55 at one end.
A 1-km long optical fiber single wire with a light source of μm and a photodetector connected to the other end is held as a bundle of about 85 cm in a circumference for 8 hours in a -20 ° C. constant temperature bath, and the transmission loss during this time is measured.
The maximum value of the transmission loss was measured.

The prototype optical fiber single fiber has a diameter of 125
This is an optical fiber obtained by coating a soft glass layer and a hard layer of an ultraviolet curable resin on a quartz glass optical fiber having a thickness of μm, and further covering the sheath. The coating of the optical fiber is a UV-cured urethane acrylate resin, and the soft layer and the hard layer have a Young's modulus of 1 MPa and 0.7 GPa, respectively, and a coating outer diameter of 0.20 mm and 0.25 mm, respectively. If necessary, a colored layer of a UV-curable urethane acrylate resin having a Young's modulus of 1 GPa may be further provided on the hard layer. However, in the prototype example, the colored layer is not provided.

In Examples 4 to 6, the Young's modulus at room temperature was 0.1 G
Pa or more, and the lateral pressure characteristics are good. Comparative Example 1 having a small room temperature Young's modulus has poor lateral pressure characteristics. Regarding the surface roughness of the inner surface of the jacket, in Examples 4 to 6 and Comparative Examples 1 and 4 in which Ra was 0.5 μm or less, the transmission characteristics at low temperatures were good. Is not good in transmission characteristics. In particular, in Comparative Example 2 where Ra is large, it can be seen that the initial transmission characteristics are deteriorated.

As described above, the Young's modulus at room temperature is 0.1 G
By using a thermoplastic resin larger than Pa, it was possible to obtain an optical fiber single fiber having good mechanical characteristics with a loss increase of 0.10 dB or less in the lateral pressure characteristics according to the measurement method described above. This lateral pressure characteristic measures the increase in loss when a static lateral pressure is applied, but it corresponds well to the instantaneous increase in transmission loss when stepping on actual construction or when construction equipment is caught. In this test, the loss increase was 0.1
It is empirically known that if it exceeds 0 dB, the bit error rate indicating the transmission quality greatly increases, instantaneous disconnection of the transmission line occurs, and disturbance of the communication signal occurs.

In the examples, as the thermoplastic resin,
The case where PVC (vinyl chloride) and nylon are used is shown. However, when flame-retardant polyethylene or fluorine resin having a higher molding temperature is used, the problem of the inner surface roughness due to volatile components is more serious, and Great effect.

In addition, a single-core optical fiber having an outer diameter of approximately 500 μm using an optical fiber having an outer diameter of approximately 250 μm is not suitable for connection with a tape-shaped optical fiber due to pitch consistency. It is advantageous.

[0029]

As is apparent from the above description, according to the first aspect of the present invention, the thermoplastic resin coated around the optical fiber has a Young's modulus of 0.1 G at room temperature.
When the surface roughness is equal to or greater than Pa, the surface roughness of the surface of the thermoplastic resin coating layer that comes into contact with the optical fiber strand is 0.
When the thickness is 5 μm or less, it is possible to obtain a single optical fiber having good lateral pressure characteristics and good transmission characteristics at low temperatures.

According to the second aspect of the present invention, the volatile components from the optical fiber can be volatilized by preheating before the coating, and the inner surface of the thermoplastic resin coating can be prevented.

According to the third aspect of the present invention, the volatile components from the optical fiber can be volatilized in advance by a vacuum drying process, and the inner surface of the thermoplastic resin coating can be prevented from being roughened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining the configuration of a first embodiment of an optical fiber single fiber according to the present invention.

FIG. 2 is a cross-sectional view for explaining a configuration of a second embodiment of the optical fiber single fiber of the present invention.

FIG. 3 is a schematic configuration diagram of a manufacturing apparatus for explaining a first embodiment of the method for manufacturing a single optical fiber of the present invention.

FIG. 4 is a schematic configuration diagram of a manufacturing apparatus for explaining a second embodiment of the method for manufacturing an optical fiber single fiber of the present invention.

FIG. 5 is an explanatory diagram of an experimental result.

FIG. 6 is an explanatory diagram of a measurement result of a prototype optical fiber single fiber.

[Explanation of symbols]

Reference numeral 1 denotes an optical fiber, 2 denotes a soft ultraviolet-curable resin coating, and 3 denotes a soft layer.
... hard UV-curable resin coating, 4 ... colored layer, 5 ... thermoplastic resin coating, 6 ... optical fiber wire, 7 ... optical fiber single core wire, 11 ... optical fiber wire supply reel, 12 ... heater, 13: Extruder, 14: Crosshead, 15: Cooling water tank, 16: Take-up reel, 17: Resin tank, 18: Vacuum dryer.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masayoshi Yamano 1-term Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa F-term in Yokohama Works, Sumitomo Electric Industries, Ltd. 2H050 BA02 BA17 BA19 BB03S BB07Q BB07R BB08S BB09S BB10S BB14Q BB14R BB17Q BB17R BB31S BB33Q BB33R BB35S BD02 BD07 4G060 AA02 AA03 AC01 AC04 AD26 CB09 CB22

Claims (3)

[Claims] 1. An optical fiber monofilament having an outer diameter of about 500 μm, wherein a thermoplastic resin is extruded and coated concentrically around an optical fiber wire coated with an ultraviolet curable resin having an outer diameter of about 250 μm. The Young's modulus at room temperature of the thermoplastic resin is 0.1 GPa or more, and the surface roughness of the surface of the single-core optical fiber in contact with the optical fiber in the coating layer of the thermoplastic resin is an arithmetic average. Roughness Ra
A single-core optical fiber having a thickness of 0.5 μm or less. 2. An optical fiber having an outer diameter of about 500 μm, wherein an outer layer coating is formed by extruding and coating a thermoplastic resin concentrically around an optical fiber coated with an ultraviolet curable resin having an outer diameter of about 250 μm. A method for producing a single fiber optical fiber, wherein the optical fiber is heated to 200 ° C. or higher immediately before extruding and coating the thermoplastic resin. 3. A light having an outer diameter of approximately 500 μm by extruding a thermoplastic resin concentrically around an optical fiber coated with an ultraviolet curable resin having an outer diameter of approximately 250 μm to form an outer layer coating. A method for producing a single fiber optical fiber, wherein after vacuum drying the optical fiber in a heated state,
A method for manufacturing a single optical fiber, comprising extruding and coating the thermoplastic resin.