JPH05323161A - Glass fiber for optical transmission - Google Patents

Abstract

PURPOSE:To provide a thin film-coated optical fiber having the almost same light transmission characteristics and fiber strength as a conventional coated optical fiber and to realize high-density optical fiber. CONSTITUTION:This glass fiber for optical transmission has a UV-curing resin coating layer around a glass fiber 1 for optical transmission. The outermost layer 3 consists of such resin satisfying [elongation (%)/Young's modulus (kg/mm<2>)]>=0.2 and is formed to have <=200mum diameter. More preferably, the Young's modulus of the outermost layer 3 is >=100kg/mm<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmission glass fiber used for optical communication, and particularly to an optical transmission glass fiber having excellent optical transmission characteristics and fiber strength, particularly a thin-walled optical transmission glass fiber (coating diameter). : 200 μm or less). In particular, the present invention relates to improvement of coating resin in resin-coated optical fibers.

[0002]

2. Description of the Related Art A glass fiber for optical transmission (optical glass fiber) has a problem in maintaining mechanical characteristics and optical transmission characteristics in the as-drawn state. And the like.

As the material, an ultraviolet curable resin (hereinafter referred to as UV resin) is generally used from the viewpoint of productivity. The coating generally has a two-layer structure, and a relatively soft buffer layer (coating diameter: about 200 μmφ, as an inner layer,
Young's modulus: about 0.1 to 0.2 kg / mm ² ) is provided, and a hard protective layer (coating diameter: about 250 μm) is provided on the outer periphery thereof.
φ, Young's modulus: 30 to 100 kg / mm ² ).

By the way, in recent years, in order to promote the opticalization of telephone networks, it is necessary to further increase the density of cables. In a tape slot type cable in which a plurality of UV resin-coated optical fibers are bundled in parallel and a tape-shaped optical glass fiber combined by a common UV resin coating is assembled, the conventional fiber coating outer diameter (about 250 μmφ) remains unchanged. There is no limit to increasing the density of the coating, and thinning of the coating (coating diameter of the outermost layer of 200 μmφ or less) is being promoted.

However, as a coating material for the outermost layer, the conventional U
In a thin-coated optical fiber (Coating outer diameter of 200 μmφ or less) using V resin (Young's modulus: 30 to 100 kg / mm ² ), the lateral pressure resistance is extremely lowered due to the thinness of the coating layer.

Therefore, a thin-walled coated optical fiber (coated outer diameter 2
In the case of 00 μmφ or less), the UV resin used for the outermost layer has an ultra-high Young's modulus in order to improve lateral pressure characteristics. As a result, the lateral pressure resistance characteristic equivalent to that of the conventional coated optical fiber (coated outer diameter of about 250 μmφ) is maintained. It should be noted that the lateral pressure characteristic referred to here is a series of characteristics in which a slight bending occurs in the fiber when the outside (lateral pressure) is applied to the fiber, and as a result, the optical transmission loss increases.

[0007]

However, a thin-walled optical fiber whose outermost layer is coated with a UV resin having an ultra-high Young's modulus (100 kg / mm ² or more) (outer diameter of 200 μm)
In the following), the optical transmission characteristics are deteriorated and the screening rupture strength is reduced. This is because the UV resin used for the outermost layer has a high Young's modulus and the elongation property is extremely small (about 6%).

The scratches on the surface of the coating are apt to be cracks due to bending stress, the outermost layer coating is buckled, and non-uniform strain is given to the glass portion, deteriorating the optical transmission characteristics. Further, the growth of the cracks easily breaks during screening. It is believed that.

Here, the screening is a test for guaranteeing the minimum strength in the longitudinal direction by applying a constant tension to the entire length of the fiber. Elongation is the percentage of the ratio of the elongation between the gauge points of the test piece to the original gauge point distance before the test piece breaks in the tensile test.

[0010]

Means for Solving the Problems As a result of various investigations for solving the above problems, the present inventors have found that the physical properties of the coating resin for the outermost layer, particularly [elongation (%) ÷ Young's modulus (kg / mm ² )]. ]
Value greatly affects the optical transmission characteristics, that is, in the case of a thin coated fiber (outer diameter of the coating is 200 μmφ or less), by setting this value to 0.2 or more, good optical transmission characteristics are maintained and screening is performed. It has been found that the strength can be improved, and thereby, the novel glass fiber for optical transmission of the present invention can be reached.

That is, the present invention is: In an optical transmission glass fiber having at least one coating layer made of an ultraviolet curable resin on the outer periphery of the optical transmission glass fiber, the ultraviolet curable resin used as the outermost layer The value of [elongation (%) ÷ Young's modulus (kg / mm ² )] is 0.2 or more, and the coating diameter of the outermost layer is 200 μ.
The glass fiber for optical transmission is characterized in that it is m or less, and the Young's modulus of the outermost coating of the glass fiber for optical transmission is 100 kg / mm ² or more.

The present invention will be described in detail below with reference to the drawings. The glass fiber for optical transmission of the present invention is basically shown in FIG.
The multi-layer structure as shown in, preferably at least a two-layer structure from the viewpoint of thinning. That is, the outermost layer of the glass optical fiber 1 is provided with the protective layer 3 having a specific physical property value of the present invention via the buffer layer 2.

The ultraviolet curable resin constituting the outermost protective coating 3 is an ultraviolet curable resin and is not particularly limited as long as it has the functions of high Young's modulus and high elongation. Epoxy acrylate, urethane acrylate, ester acrylate and the like are desirable because the effects of increasing the Young's modulus and increasing the elongation can be relatively easily obtained. These may be used alone (generally in the form of an oligomer), but may also be used in combination with a photoinitiator or a polyfunctional monomer.

As the buffer layer 2, the ultraviolet curable resin for the outermost layer may be used as appropriate, or a relatively soft coating material such as silicone resin may be used. Of course, if necessary, a layer that is the same as or different from the material for the protective layer or the buffer layer may be further provided. The optical transmission glass fiber of the present invention can be easily manufactured by a conventional optical fiber manufacturing apparatus as shown in FIG.

[0015]

The outermost coating 3 serves as a shell for protecting the glass from external pressure. Therefore, the higher the Young's modulus of the coating 3, the stronger the external pressure (side pressure). However, on the other hand, when the elongation property is small, it is extremely brittle and easily cracked when bent.

It is considered that this causes non-uniformity of the coating surface, strains the glass to deteriorate the optical transmission characteristics, and eventually reduces the fiber strength. This effect is
Since the higher the Young's modulus of the coating resin of the outermost layer is, the more remarkable it is. Therefore, it is necessary to increase the elongation property as the Young's modulus is increased.

In the present invention, as a result of various studies and investigations on the relationship between the Young's modulus of the outermost layer coating material, the elongation characteristics and the optical transmission characteristics, the value of [elongation (%) ÷ Young's modulus (kg / mm ² )] And the optical transmission characteristics were found, and in particular, a combination of Young's modulus and elongation characteristics that optimizes the optical transmission characteristics and the fiber strength in a thin-coated fiber (outer diameter of the coating is 200 μmφ or less) was determined.

By the way, the conventional fiber (coating diameter: 25
(About 0 μmφ), the coating layer is sufficiently thick,
The effect of increasing the Young's modulus of the outermost layer coating was small, and the necessity thereof was not so large. However, the effect of high Young's modulus and high elongation as in the present invention is indispensable only in a thin-walled coated fiber having a thin coating layer (coating outer diameter: 200 μmφ or less).

[0019]

The present invention is illustrated by the examples, which do not limit the scope of the invention. Using the optical fiber manufacturing apparatus shown in FIG. 3, the optical fiber preform 4 is drawn in the drawing furnace 5 to obtain the glass optical fiber 1. After the resin coating is provided on the optical fiber 1 by passing the optical fiber 1 through the resin coating device 6, the ultraviolet ray curable resin coating is cured by the ultraviolet ray irradiation device 9 provided with the ultraviolet ray irradiation lamp 7. A thin optical fiber 1 having the structure shown was obtained.

For the inner layer (buffer layer) 2, a UV-curable urethane acrylate resin having a Young's modulus of 0.10 kg / mm ² at room temperature was commonly used, and the coating outer diameter was 150 μmφ. On the other hand, for the outer layer (protective layer) 3, various UV-curable urethane acrylate resins having different Young's moduli and elongation characteristics as shown in Table 1 were used to finish the coating outer diameter to 180 μmφ.

The lateral pressure characteristics and optical transmission characteristics of each coated optical fiber were investigated. The results are shown in Table 1. The characteristics of the conventional coated optical fiber (coating outer diameter 250 μm) are also shown.

[0022]

[Table 1]

Note) * 1) Flat plate lateral pressure test: increase in transmission loss at a load of 50 kg; expressed by Δα (1.55 μm). * 2) Optical transmission characteristics (1.55μ in the bobbin winding state)
m). * 3) Number of breaks per 100 km in 700 g screening test. * 4) Young's modulus and elongation are measured according to JIS method .

Further, FIG. 1 shows the relationship between [elongation (%) / Young's modulus (kg / mm ² )] of the outermost layer coating resin of the coated optical fibers A to F shown in Table 1 and the optical transmission characteristics. Show. From this result, the [elongation (%) of the coating resin used for the outermost layer
It was found that when the value of ÷ Young's modulus (kg / mm ² )] is 0.2 or more, a thin-coated optical fiber equivalent to the conventional fiber in optical transmission characteristics and fiber strength can be obtained.

In the above description, the case where each of the inner layer and the outer layer is one layer has been described as an example. However, in the coated optical fiber having at least one layer of ultraviolet curable resin coating on the outer circumference of the fiber, the present invention is the outermost layer. [Elongation (%) ÷
If the value of Young's modulus (kg / mm ² )] is within the limit range of the present invention, similar effects can be obtained.

[0026]

As described above, according to the present invention, a thin-walled coated optical fiber (coated outer diameter of 200 μm) capable of maintaining almost the same optical transmission characteristics and fiber strength as the conventional coated optical fiber.
mφ or less), which is very effective for increasing the density of optical cables.

[Brief description of drawings]

FIG. 1 shows the [elongation (%)] of the outermost layer coating resin used in the present invention.
÷ Young's modulus (kg / mm ² )] and the optical transmission characteristics.

FIG. 2 is a cross-sectional view of an example of a resin-coated optical fiber of the present invention.

FIG. 3 is a schematic view showing an outline of an optical fiber manufacturing apparatus used for manufacturing the optical transmission fiber of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass optical fiber 2 Buffer layer 3 Protective layer (outermost layer) 4 Optical fiber base material 5 Drawing furnace 6 Resin coating device 7 Ultraviolet irradiation lamp 8 Cylindrical body 9 Ultraviolet irradiation device 10 Reflecting mirror 11 Resin coating optical fiber 12 Winding Machine

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Juya Tsunoda 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Wataru Katsurajima 1-tani, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Denki Kogyo Co., Ltd. Yokohama Works (72) Inventor Hiroo Matsuda 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Denki Kogyo Co., Ltd. Yokohama Works (72) Inventor Shigeru Tomita 1-1-1 Uchisaiwai-cho, Chiyoda-ku, Tokyo No. 6 Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A glass fiber for optical transmission comprising at least one coating layer made of an ultraviolet curable resin on the outer circumference of the glass fiber for optical transmission, wherein the elongation (% (% ) ÷ Young's modulus (kg / m
m ² )] is 0.2 or more, and the coating diameter of the outermost layer is 200 μm or less, a glass fiber for optical transmission. 2. The glass fiber for optical transmission according to claim 1, wherein the outermost coating of the glass fiber for optical transmission has a Young's modulus of 100 kg / mm ² or more.