JP2002372654A - Optical fiber ribbon - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control increase in the transmission loss of each optical fiber to no more than a specified value when an optical fiber ribbon is immersed in warm water at 60 deg.C for two weeks. SOLUTION: In order to prevent peeling on the interface between the colored optical fibers 15 and an integrating layer 4 both constituting the optical fiber ribbon, the maximum thickness of the color layer 14 of the colored optical fiber 15 is controlled to <=10 μm. As for the colored resin constituting the colored layer 14, a resin having high transmitting property for UV rays is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber ribbon used for an optical fiber cable or the like.

[0002]

2. Description of the Related Art As shown in FIG. 2, an optical fiber ribbon is coated with an ultraviolet curable resin to which a coloring agent is added on a 250 μm optical fiber 1 and cured to form a colored layer 2.
A plurality of colored optical fiber strands 3 provided with
Book) having a structure in which the layers are arranged side by side in parallel and collectively covered with an integrated layer 4 made of an ultraviolet curable resin or the like;
It is widely used as a component of an optical unit of an optical fiber cable.

[0003] Incidentally, as one item of the characteristic evaluation test of such an optical fiber ribbon, 2 pieces of hot water at 60 ° C are heated.
There is a severe one that immerses continuously for a week and measures the amount of change (increase) in the transmission loss of each of the colored optical fiber wires 3, 3,. In this characteristic evaluation test, the colored optical fiber 3
Of the transmission loss of the specified value of 0.25 dB (wavelength 1.5
It was found that there was an optical fiber ribbon exceeding 5 μm).

When the cause of this phenomenon was investigated, it was found that the interface between the colored layer 2 and the integrated layer 4 of the colored optical fiber 3 and the secondary layer made of the ultraviolet curable resin of the colored layer 2 and the optical fiber 1 were used. Delamination occurs at the interface with the coating layer or at the interface between the bare optical fiber of the optical fiber 1 and the primary coating layer made of an ultraviolet-curable resin or the like. It became clear that the transmission loss of 1 ... increased.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-described delamination even if the optical fiber ribbon is immersed in hot water at 60 ° C. for two weeks.
The purpose of the present invention is to keep the amount of increase in transmission loss of the optical fiber caused by the delamination within a specified value.

[0006]

This problem is solved by setting the maximum thickness of the colored layer of the colored optical fiber which forms the optical fiber ribbon to 10 μm or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
FIG. 1 shows an example of a colored optical fiber strand constituting the optical fiber ribbon of the present invention. Reference numeral 11 in the figure
Indicates an optical fiber bare wire. This bare optical fiber 11 is
It has an outer diameter of 125 μm.
A primary coating layer 12, a secondary coating layer 13, and a coloring layer 14 are sequentially coated on 1 to form a coloring optical fiber 15.

The primary coating layer 12 has a cured Young's modulus of 5
A soft UV-curable resin having a thickness of 10 kg / mm ² or less is applied on the bare optical fiber 11 and cured.
４０40 μm. The secondary coating layer 13 is formed by applying and curing a hard UV-curable resin having a Young's modulus of 20 to 200 kg / mm ² after curing on the primary coating layer 12, and has a thickness of 20 to 40 μm. I have. The coloring layer 14 is formed by applying and curing an ultraviolet curable resin to which coloring agents of various colors are added on the secondary coating layer 13.
Its maximum thickness is 10 μm or less.

Here, the reason why the colored layer 14 is defined by its maximum thickness is that the thickness of the colored layer 14 is not always uniform, and as shown in FIG. 1, it is actually deviated in its circumferential direction and its longitudinal direction. This is because the above-described problem can be solved by setting the maximum thickness to 10 μm or less in many cases. The average thickness of the coloring layer 14 is 5 to 10 μm.
m, but is not limited to this.

In order to make the maximum thickness of the coloring layer 14 equal to or less than 10 μm, the diameter of the opening of the coating die is adjusted at the time of coating the ultraviolet curable resin to be the coloring layer 14, and the optical fiber entering the coating die is adjusted. This is possible by minimizing the unevenness of the wires and preventing uneven thickness. It is also preferable to select a coloring agent having a high ultraviolet transmittance as the coloring agent used for the coloring layer 14 so that the curing of the coloring layer 14 by the ultraviolet ray is more completely performed.

A plurality of such colored optical fiber strands 15 are arranged in parallel and adjacent to each other in the same manner as in the prior art. It is cured to form the optical fiber ribbon of the present invention.

In such an optical fiber tape, the above-mentioned delamination is prevented and the increase in transmission loss is suppressed for the following reasons. That is, if the thickness of the coloring layer 14 is too large, the primary coating layer 12 of the optical fiber 15
When a tensile stress acts on the substrate and the adhesion between the bare optical fiber 11 and the primary coating layer 12 is reduced by immersion in warm water, delamination occurs at this interface.

If the colored layer 14 is too thick, the colored layer 1
4, the ultraviolet rays during curing did not sufficiently reach the lower layer portion (inner portion), the lower layer portion failed to cure, and the interface between the colored layer 14 and the secondary coating layer 13 was peeled off when immersed in warm water to generate blisters. I do. Further, it has been clarified that peeling at the interface between the coloring layer 14 and the integrated layer 4 occurs when the coloring layer 14 is thick. Therefore, by defining the maximum thickness of the colored layer 14 to be 10 μm or less, the above-described delamination can be prevented, and the increase in the transmission loss of the optical fiber 11 can be suppressed to a slight level. .

A specific example will be described below. An ultraviolet curable resin is applied on the bare optical fiber having an outer diameter of 125 μm, and cured to provide a primary coating layer and a secondary coating layer to obtain an optical fiber element having an outer diameter of 250 μm. Is applied and cured to form a colored layer, and has an average outer diameter of 260
A colored optical fiber of μm was used. During the coating of the colored layer, its maximum thickness and average thickness were variously changed.

Next, four colored optical fiber cores were prepared by a conventional method using four colored optical fiber strands and an ultraviolet curing resin as an integrated layer. The four-core optical fiber ribbon was immersed in hot water at 60 ° C. for two weeks continuously, and the amount of transmission loss before and after immersion (measurement wavelength 1.
55 μm, average value of 4 cores) was measured. Table 1 shows the results. In the evaluation of Table 1, the case where the transmission loss increase amount is less than 0.25 dB is represented by ○, the range of 0.25 to 0.3 dB is represented by Δ, and
Those exceeding 3 dB were represented by x.

[0016]

[Table 1]

From the results in Table 1, it is clear that if the maximum thickness of the colored layer of the colored optical fiber is 10 μm or less, the transmission loss increase of the optical fiber can be reduced to 0.25 dB or less.

[0018]

As described above, in the optical fiber ribbon of the present invention, the maximum thickness of the colored layer of the colored optical fiber constituting the optical fiber tape is set to 10 μm or less. Even when subjected to a severe test in which the tape core wire is immersed in hot water at 60 ° C. for two weeks, the increase in the transmission loss of the optical fiber can be reduced to 0.25 dB or less.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a colored optical fiber used for an optical fiber ribbon of the present invention.

FIG. 2 is a schematic sectional view showing an example of an optical fiber ribbon according to the present invention.

[Explanation of symbols]

14: colored layer, 15: colored optical fiber, 4: integrated layer

Claims (1)

[Claims] 1. An optical fiber ribbon comprising a plurality of colored optical fiber strands each having a colored layer coated on an optical fiber strand, and being collectively covered with an integrated layer, wherein the maximum thickness of the colored layer is An optical fiber ribbon having a length of 10 μm or less.