JP2002255590A - Colored optical fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a colored optical fiber which never generates blister even immersed in water especially in warm water for a long period of time, and in which optical transmission loss is never increased. SOLUTION: The constitution of the colored optical fiber is that a naked optical fiber 11 is laminated with coating layers 12 and 13 to form an elementary optical fiber 30, which is coated with a coloring layer 14 to form the colored optical fiber 40, and the Young's modulus of the coloring layer 14 is made larger than that of the outermost laminated layer 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colored optical fiber used for an optical cable, and more particularly to a colored optical fiber having excellent water resistance to hot water.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 3, a plurality of optical fiber wires 10 are arranged in parallel to form a tape material 5 as shown in FIG.
A tape fiber integrated into a tape shape is formed by a slot 6 of a spacer having a tension member 8 provided at the center.
The optical fiber cable is provided in a state where a plurality of sheets are placed in a stacked state, and a protective tape or a sheath 7 is provided on the outside thereof, or as shown in FIG. A plurality of optical fiber wires 10 are buried at equal intervals around the tension member 8 and an outer layer thereof is provided with a resin coating layer such as a reinforcing layer, a waterproof layer, and a protective sheath, and is used as an optical fiber unit. ing.

[0003] As shown in Figs. 3 and 4, an optical fiber 10 used for these optical fibers mainly has a role of a buffer layer on the outer periphery of the bare optical fiber 1 composed of a core and a clad, against side pressure and the like. And a secondary coating layer (secondary layer) 3 for preventing damage from the outside.

A plurality of optical fiber wires 10 in such an optical fiber cable or an optical fiber unit are used as colored optical fibers 20 provided with colored layers 4 of different colors so as to be distinguished from each other. I have.

As the coloring layer 4, an ultraviolet curable resin to which a coloring agent is mainly added is widely used.

[0006]

However, when the colored optical fiber 20 is exposed to water for a long period of time when water or the like enters the above-mentioned optical fiber for some reason and is exposed to water (steam),
Penetrates the resin coating layer of the optical fiber, between the glass layer (bare optical fiber) 1 and the primary coating layer 2 or between the primary coating layer 2
And the secondary coating layer 3, causing peeling at portions where the adhesion between the layers is relatively weak, and causing water to accumulate at the peeled portions and cause blisters.

[0007] Such deformation by the blister gives a lateral pressure to the glass layer (bare optical fiber) 1 to cause non-uniform microbends in the longitudinal direction, thereby increasing optical transmission loss.

In this regard, Japanese Patent Application Laid-Open No. 9-5587 discloses an optical fiber that can suppress blisters generated between a glass layer and a primary coating layer.
Japanese Patent No. 31723 discloses an optical fiber that can suppress the occurrence of blisters between the secondary coating layer and the coloring layer.

However, the generation of blisters is not limited to only between the layers 2, 3, and 4, but the occurrence of blisters
3 and 4, especially in the primary coating layer 2;
As in the case of an optical fiber strand disclosed in Japanese Patent Application Laid-Open No. 5587/1993, it is possible to increase the adhesion between the glass layer 1 and the primary coating layer 2 or to use an optical fiber core disclosed in Japanese Patent Application Laid-Open No. As described above, the blister generated in each of the layers 2, 3, and 4 cannot be prevented only by increasing the adhesion between the secondary coating layer 3 and the coloring layer 4.

Particularly, in the case of the colored optical fiber 20, there is a problem that light transmission loss increases when blisters are generated in the primary coating layer 2.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a colored optical fiber which does not generate blisters and does not increase optical transmission loss even when immersed in water, especially in warm water for a long time. To provide.

[0012]

According to a first aspect of the present invention, a colored layer is provided on the outer periphery of a bare optical fiber in which a plurality of coating layers are laminated on the outer periphery of the bare optical fiber. In the colored optical fiber, the Young's modulus of the colored layer is higher than the Young's modulus of the outermost layer in the coating layer.

According to a second aspect of the present invention, the ratio of the Young's modulus of the colored layer to the Young's modulus of the outermost layer in the coating layer is larger than 1 and smaller than 3.

According to a third aspect of the present invention, the plurality of coating layers and the coloring layers are formed such that the Young's modulus is sequentially increased from the inside to the outside.

According to a fourth aspect of the present invention, in a colored optical fiber in which a colored layer is provided on an outer periphery of an optical fiber in which a plurality of coating layers are laminated on the outer periphery of a bare optical fiber, a glass transition temperature of the colored layer is provided. Is higher than the glass transition temperature of the outermost layer in the coating layer.

According to the above configuration, the colored layer uniformly disperses and alleviates internal stress caused by distortion or the like generated in the secondary coating layer due to intrusion of water. Thereby, blisters do not occur in portions where the adhesion between the layers is relatively weak or in the primary coating layer, and the light transmission loss does not increase even when exposed to water for a long time.

[0017]

Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a cross-sectional view of a colored optical fiber according to the present invention.

As shown in FIG. 1, a colored optical fiber 40 according to the present invention includes a primary coating layer (primary layer) 12 having a role of a buffer layer mainly against lateral pressure and the like on the outer periphery of an optical fiber bare wire 11. Next, a coloring layer 14 is provided on the outer periphery of the optical fiber 30 having a structure coated with a secondary coating layer (secondary layer) 13 for preventing damage from the outside.

The coloring layer 14 is formed of an ultraviolet curable resin to which a coloring agent has been added.

The primary coating layer 12 and the secondary coating layer 13 provided on the bare optical fiber 11 of the present invention are not particularly limited, but an ultraviolet curable resin composition is mainly used.

Examples of the UV-curable resin composition include urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and silicon (meth) acrylate.

The primary coating layer 12 mainly has a Young's modulus of 0.1.
The secondary coating layer 13 having a Young's modulus of 5 to 10 MPa is used for the secondary coating layer 13.

The composition of the colored layer 14 is not particularly limited. For example, ultraviolet rays such as urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate, and silicon (meth) acrylate can be used. A cured resin composition to which a pigment, a dye, or the like is added as a colorant can be used.

The fact that the Young's modulus of the colored layer 14 is higher than the Young's modulus of the secondary coating layer 13 means that the primary coating layer 12 has a very low Young's modulus and is provided on the bare optical fiber 11. This is because the coating layers 12, 13, and 14 are arranged such that the Young's modulus increases from the inside toward the outside.

If the ratio of the Young's modulus of the colored layer 14 to the secondary coating layer 13 is set to be larger than 1 and smaller than 3, if the ratio is smaller than 1, the coating layer will be distorted when immersed in hot water at 60 ° C. This is because the internal stress is transmitted non-uniformly, peeling occurs at a portion where the adhesion between the layers is weak, and blisters are easily generated. On the other hand, if the Young's modulus ratio is larger than 3, that is, if the Young's modulus difference is too large, the stress caused by curing shrinkage or the like of the coating layer having a large Young's modulus is large, and there is a problem that the initial light transmission loss increases. is there.

The fact that the glass transition temperature of the coloring layer 14 is higher than the glass transition temperature of the secondary coating layer 13 means that the coating layers 12, 13, 1 on the bare optical fiber 11 are similar to the Young's modulus.
This is because the glass transition temperature increases from the inside to the outside of No. 4.

This alleviates uneven transmission of internal stress caused by distortion of each coating layer when immersed in 60 ° C. hot water or the like, and prevents peeling of portions with weak adhesion between each layer and generation of blisters. Can be suppressed.

When the colored optical fiber 40 is used for an optical fiber cable, as shown in FIG. To form 5
In the state of being stacked in a step, it is accommodated in a slot of a spacer provided with a tension member at the center, and a protective tape or a sheath is provided outside the slot.

When used for an optical fiber unit, six colored optical fibers are embedded in a thermoplastic resin at equal intervals around a tension member provided at the center, and a reinforcing layer and a waterproof layer are provided on the outer layer. And a resin coating layer such as a protective sheath.

Next, the water resistance of the present invention and the prior art will be described.

First, as Examples 1 and 2 of the present invention and Comparative Example 1 of the prior art, a colored optical fiber in which the ratio of the Young's modulus of the primary coating layer, the secondary coating layer, and the colored layer is as shown in Table 1 A, B, and C were prepared, and further, Example 3,
As Comparative Example 4 and Comparative Example 2 of the prior art, colored optical fibers D, E, and F in which the glass transition temperatures of the primary coating layer, the secondary coating layer, and the coloring layer were as shown in Table 2 were produced.

The Young's modulus and the glass transition temperature in Tables 1 and 2 were measured by preparing sheets. Sheet thickness is 100 ± 5
μm, and irradiation amount of 100 under nitrogen atmosphere.
A sheet cured at 0 mJ / cm ² was used. The Young's modulus is a condition based on JIS K7100.
This is a value obtained by extrapolating a 2.5% elongation point from an SS curve obtained at a pulling speed of 1 mm / min using a No. 2 dumbbell piece compliant with K7113. The glass transition temperature was determined from the tan δ peak value using a dynamic viscoelasticity measurement device.

[0034]

[Table 1]

[0035]

[Table 2]

Each of the colored optical fibers A to F having a diameter of 1000 m in the form of a bundle having a diameter of 300 mm is immersed in warm water at 60 ° C. It was measured.

Further, tape fibers were prepared using the colored optical fibers A to F, immersed in warm water at 60 ° C., and the change of the light transmission loss was measured every days after immersion.

The results of these measurements are shown in FIGS. 5 and 6, with the immersion days (days) plotted on the horizontal axis and the loss increase (dB / km) on the vertical axis.

FIG. 5 shows the change in the transmission loss of the colored optical fiber when immersed in 60 ° C. hot water, and FIG. 6 shows the change in the transmission loss of the colored optical fiber in the tape fiber when immersed in 60 ° C. hot water.

In FIGS. 5 and 6, lines connecting black circles indicate changes in A, lines connecting black squares indicate changes in B, and lines connecting black triangles indicate changes in C. A line connecting white circles indicates a change in D, and a line connecting white squares indicates E.
, And the line connecting the white triangles indicates the change in F.

As shown in FIG. 5, the colored optical fibers A, B, D, and E according to the embodiment of the present invention hardly increase the optical transmission loss even after 30 days from immersion in warm water.
The C and F colored optical fibers, which are comparative examples of the prior art, gradually increase in optical transmission loss after immersion in warm water.
The optical transmission loss increased from 15 dB / km to 0.2 dB / km.

From this fact, when the primary and secondary coating layers of the colored optical fiber and the colored layer are arranged in such a manner that the Young's modulus and the glass transition temperature are increased in this order, the optical transmission loss when immersed in 60 ° C. hot water is increased. It can be seen that it can be suppressed.

As shown in FIG. 6, the colored optical fibers of Examples A, B, D, and E of the present invention were immersed in warm water for 30 days even if the colored optical fibers in the tape fiber were used. Even though the optical transmission loss hardly increases,
The C and F colored optical fibers, which are comparative examples of the prior art, gradually increase in optical transmission loss after being immersed in warm water.
The optical transmission loss increased from 12 dB / km to 0.15 dB / km.

From this, it is understood that when the primary and secondary coating layers of the colored optical fiber in the tape fiber and the colored layer are arranged in such a manner that the Young's modulus and the glass transition temperature are increased in this order, the 6
It can be seen that an increase in optical transmission loss when immersed in hot water at 0 ° C. is suppressed.

[0045]

In summary, according to the present invention, it is possible to provide a colored optical fiber which does not generate blisters even when immersed in water, especially in warm water for a long period of time, and does not increase light transmission loss.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a colored optical fiber according to the present invention.

FIG. 2 is a cross-sectional view of a tape fiber using the colored optical fiber of FIG.

FIG. 3 is a cross-sectional view of an optical fiber cable using a colored optical fiber.

FIG. 4 is a cross-sectional view of an optical fiber unit using a colored optical fiber.

FIG. 5 is a diagram showing a change in transmission loss of a colored optical fiber when immersed in hot water at 60 ° C.

FIG. 6 is a diagram showing a change in transmission loss of a colored optical fiber in a tape fiber when immersed in hot water at 60 ° C.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 bare optical fiber (glass layer) 12 primary coating layer (primary layer) 13 secondary coating layer (secondary layer) 14 colored layer 30 optical fiber strand 40 colored optical fiber

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Claims (4)

[Claims] 1. A colored optical fiber in which a colored layer is provided on the outer circumference of an optical fiber in which a plurality of coating layers are laminated on the outer circumference of a bare optical fiber, wherein the colored layer has a Young's modulus in the coated layer. A colored optical fiber having a Young's modulus higher than that of the outermost layer. 2. The colored optical fiber according to claim 1, wherein the ratio of the Young's modulus of the colored layer to the Young's modulus of the outermost layer in the coating layer is greater than 1 and less than 3. 3. The colored optical fiber according to claim 1, wherein the plurality of coating layers and the colored layer are sequentially formed with a higher Young's modulus from the inside to the outside. 4. In a colored optical fiber in which a colored layer is provided on the outer circumference of an optical fiber in which a plurality of coating layers are laminated on the outer circumference of a bare optical fiber, the glass transition temperature of the colored layer is lower than that of the coated layer. A colored optical fiber having a glass transition temperature higher than the glass transition temperature of the outermost layer.