JPH0643345A - Coated optical fiber - Google Patents

Abstract

PURPOSE:To provide transmission characteristic with low light transmission loss and high stability by providing a coated layer made of UV curing resin whose coefficient of contraction for length size by heating on an optical fiber is specified. CONSTITUTION:A primary layer 2 and a buffer layer 3 are formed on the optical fiber 1 consisting of core with high refractive index and clad with low refractive index, respectively by applying the UV curing resin whose coefficient of contraction for length size by the heating of a curing material is less than 0.5%. As the UV curing resin, for example, urethane acrylate resin, etc., can be used, and the primary layer 2 and the buffer layer 3 can be formed by combining the resin with low Young's modulus and the one with high Young's modulus out of such resin. Thereby, the contraction of a resin coated layer by the heating can be suppressed and stress by the contraction of the optical fiber is scarcely generated. Therefore, the transmission characteristic scarcely increasing the light transmission loss and with high stability can be possesed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber core which causes almost no increase in optical transmission loss due to heating.

[0002]

2. Description of the Related Art In recent years, as a coating material for protecting an optical fiber, an ultraviolet curable resin has been widely used in place of silicone resin or nylon in view of high speed curability. In the optical fiber core wire coated with such a resin, the normal heat cycle characteristic (H
/ C characteristics) is used as a reference to select an ultraviolet curable resin, and a two-layer coating consisting of a combination of a primary layer (primary coating) and a buffer layer (buffer layer) or a secondary layer (secondary coating) is performed. It is being appreciated. The characteristics that are the criteria for selecting the resin include workability such as viscosity and curability, H / C characteristics such as linear expansion coefficient and glass transition point (Tg), water absorption rate and hydrogen generation amount, and Stability such as adhesion to glass constituting an optical fiber, Young's modulus or lateral pressure characteristics, gel fraction, curing shrinkage, or refractive index are known.

[0003]

However, in an optical fiber core wire coated with an ultraviolet curable resin selected on the basis of the above-mentioned characteristics and having a primary layer and a buffer layer formed respectively, a combination of resins is used. Depending on the characteristics, the characteristics may vary or the characteristics may not be sufficient.

Further, in the case of nylon coating, the strain during molding is usually relaxed after molding, so that the light transmission loss may be rather reduced due to heat cycles, etc. Further, conventionally, due to crystallization of resin. Operations such as air cooling are performed to minimize shrinkage, but in optical fiber cores coated with UV-curable resin, the effects of such stress on optical transmission characteristics are mostly considered. Didn't.

The present invention has been made in view of these points, and in an optical fiber core wire provided with a protective coating of an ultraviolet curable resin, the resin is selected on the basis of the dimensional change of the resin after curing, An object of the present invention is to provide a stable optical fiber core wire with a small optical transmission loss.

[0006]

The optical fiber core wire of the present invention has a lengthwise shrinkage factor caused by heating on the optical fiber.
It is characterized in that a coating layer of 0.5% or less of an ultraviolet curable resin is provided.

In the present invention, examples of the ultraviolet curable resin having a dimensional shrinkage of 0.5% or less due to heating, which is coated on the optical fiber, include urethane-acrylate resin. In the present invention, such a resin having a low Young's modulus and a resin having a high Young's modulus are combined to form a primary layer and a buffer layer or a secondary layer, respectively. Here, the shrinkage rate of the UV-curable resin due to heating is limited to 0.5% or less, when the resin with a heat shrinkage rate exceeding 0.5% is coated, the inner optical fiber will be heated by the shrinkage of the cured resin. This is because a large stress is generated, which increases optical transmission loss and is not preferable.

[0008]

In the optical fiber core wire of the present invention, an ultraviolet curable resin having a shrinkage factor of 0.5% or less due to heating of a cured product is provided on an optical fiber composed of a high refractive index core and a low refractive index clad. Since the primary layer, the buffer layer and the like are respectively formed by the coating, the shrinkage of the resin coating layer due to heating is small, and the stress due to the shrinkage hardly occurs in the optical fiber. Therefore, there is almost no increase in optical transmission loss, and stable transmission characteristics are provided.

[0009]

EXAMPLES Examples of the present invention will be described below.

Examples 1 to 4 First, as an ultraviolet curable resin, urethane-acrylate resins having Young's modulus, gel fraction and Tg shown in Table 1 were prepared, and samples of these resins were prepared as follows. . That is, urethane for the primary layer of A and B-
For each of the acrylate resin and the urethane-acrylate resin for the buffer layer of C to E, after forming a coating film having a thickness of 10 to 100 μm, more preferably a thickness corresponding to the coating thickness in the optical fiber core, The coating film was irradiated on a quartz plate with ultraviolet rays at a dose at which the physical properties of the cured product confirmed in advance were saturated and cured to prepare a sheet-shaped sample.

Next, with respect to each of the sheet-shaped samples thus prepared, the shrinkage rate and the weight loss rate of the length dimension due to heating were measured by the following methods. The results of these measurements are shown in Table 1.

<Measurement of heat shrinkage rate> Between chucks (20 mm)
The sheet-shaped sample was sandwiched between and the shrinkage rate (%) due to heating when heated to 70 ° C. was measured using TMA (thermo-mechanical analysis) in a state where tension was applied by a load of 5 g. During heating, the temperature was raised at a rate of 5 ° C / min, the sample was kept at a temperature of 70 ° C, and measurement was performed for 20 hours. However, when the shrinkage was not completed in 20 hours, the time was extended and heating was performed until the shrinkage reached saturation.

<Measurement of heating loss rate> 1 sheet-shaped sample
It was vacuum dried at a temperature of 00 ° C. for 24 hours, weighed before and after heating, and the reduction rate was obtained. The weighing was performed with an accuracy of 0.1 g, and the weight reduction rate was calculated to the order of 0.1%.

[0014]

[Table 1] Next, as shown in FIG. 1, on the single mode type optical fiber 1 having an outer diameter of 125 μm, which is composed of a high refractive index core and a low refractive index clad, the combinations A to A
After coating each urethane-acrylate resin of E, the resin is cured by irradiating ultraviolet rays with an ultraviolet lamp (high pressure mercury lamp), and the primary layer 2 (external diameter after coating)
185 μm) and a buffer layer 3 (outer diameter after coating 240 μm) were respectively formed.

Next, the heat cycle characteristics (H / C characteristics) and the high temperature heating characteristics of the optical fibers of the examples and comparative examples thus obtained were measured as follows. That is, the H / C characteristics are from -40 ℃
Heat cycle at 80 ℃ at a rate of 2 cycles / day, after applying it to the optical fiber core, and then returning it to room temperature.
Increase the optical transmission loss at m for the 10th cycle and 100
Each measurement was made during the first cycle. Regarding the high-temperature heating characteristics, the temperature was raised to room temperature after being left at 60 ° C. and 80 ° C. for 1 month, and the increase in optical transmission loss was measured. The results of these measurements are shown in Table 2.

[0016]

[Table 2] From these measurement results, the UV-curable urethane-acrylate resin (A,
The optical fiber core wire of the embodiment in which the primary layer and the buffer layer are respectively formed by coating (B, C, D) is almost the same even when left at high temperature for a long time or subjected to heat cycle. It was found that the optical transmission loss did not increase and stable transmission characteristics were exhibited. On the other hand, in the optical fiber core wire of the comparative example, since the buffer layer is formed of the urethane-acrylate resin of E having a large heat shrinkage rate, the shrinkage is accelerated by heating for a long time or a heat cycle, and It was found that a contraction stress is generated in the fiber body, which greatly increases the optical transmission loss.

In the above embodiments, the ordinary round optical fiber core wire has been described, but the present invention is not limited to this. That is, even in a tape type core wire having a structure in which a plurality of optical fibers are juxtaposed in parallel and a primary layer and a buffer layer are collectively covered on the outside thereof, ultraviolet rays having a heat shrinkage of 0.5% or less of a cured product The same effect can be obtained by coating with a curable resin. In addition, it is said that similar effects can be obtained by using an ultraviolet curable resin having a heat shrinkage of 0.5% or less even in an optical fiber core wire in which a colored coating layer is formed of an ultraviolet curable resin for coloring. There is no end.

[0018]

As described above, according to the optical fiber core wire of the present invention, the shrinkage of the coating layer due to heating is small and the stress generated in the optical fiber due to the shrinkage is small, so that the optical transmission loss hardly increases due to heating, Shows stable transmission characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of an embodiment of an optical fiber core wire of the present invention.

[Explanation of symbols]

 1 ………… Optical fiber 2 ………… Primary layer 3 ……… Buffer layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshio Ishida, Inventor Yoshio Ishida, 2-1-1, Oda Sakae, Kawasaki-ku, Kanagawa Prefecture No. 1-1 No. 1 Showa Electric Cable Co., Ltd.

Claims (1)

[Claims] 1. An optical fiber core wire comprising an optical fiber and a coating layer of an ultraviolet curable resin having a shrinkage factor of 0.5% or less in a length dimension due to heating.