JPH08220371A - Optical fiber coupler - Google Patents

Abstract

PURPOSE: To obtain high adhesion strength for a wide temp. range and to obtain excellent reliability and durability by using an epoxy adhesive and an acrylate adhesive having different glass transition temp. from that of the epoxy adhesive and subjecting the surface of a glass reinforcing device to silane coupling treatment. CONSTITUTION: Optical fibers 13 of a coupler main body 14 on both sides of the fused and stretched part 15 of the coupler 14 are adhered and fixed to a reinforcing device 11 with two kinds of adhesives 16, 17. The one of the two adhesive is an epoxy adhesive 16, and the other is an acrylate adhesive 17. As for the epoxy adhesive 16, an epoxy adhesive having 40-50 deg.C glass transition temp. is used. As for the acrylate adhesive 17, an acrylate adhesive having >=80 deg.C glass transition temp, preferably 90-150 deg.C, is used. The inner surface of a square groove 12 of the reinforcing member where at least adhesives 16, 17 are applied is subjected to silane coupling treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melt-stretching type optical fiber coupler, which has improved adhesive stability between a coupler body and a reinforcing device.

[0002]

2. Description of the Related Art As an optical coupler, as shown in FIG. 3, two or more optical fibers 1, 1 are spliced together and melt-drawn to form an optical coupling portion 2 to form a coupler body 3.
It is well known that the above is housed in a glass reinforcing device 4 and fixed with an adhesive 5 such as an epoxy adhesive. In this product, the thickness of the melt-stretched portion 2 that becomes the optical coupling portion 2 is extremely thin due to stretching, and the glass surface has mechanically reduced strength. Therefore, the melt-stretched portion 2 must be protected and reinforced. Therefore, it is housed in the glass reinforcing device 4.

In such an optical coupler, stable adhesiveness is maintained in a wide temperature range, and a coefficient of thermal expansion of 100 times or more between the optical fiber 1 and the reinforcing device 4 and the adhesive 5. The stress caused by the difference and the temperature change and the adhesive 5
An important requirement is that the curing shrinkage strain itself does not cause peeling or breakage of the adhesive 5.

Conventionally, quartz glass has been mainly used for the reinforcing device 4 and an epoxy adhesive having a small curing shrinkage has been mainly used for the adhesive 5. However, the linear expansion coefficient of quartz glass is 2 × 10 ^-7 / ° C.
That of the epoxy adhesive is 8 × 10 ⁻⁵ / ° C., there is a very large difference, and there is no change in its characteristics in the use environment of the optical coupler from −40 ° C. to 85 ° C. Are required, and the temperature difference reaches 125 ° C.

For this reason, the optical coupler reinforcer 4 and the adhesive 5
A stress due to a large difference in coefficient of thermal expansion is generated at the interface with and, and there is always a risk of the adhesive 5 peeling off or the adhesive 5 itself breaking (cracking). It will be.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to obtain an optical fiber coupler having high reliability and durability without the risk of being caused by such an adhesive.

[0007]

This problem is solved by using two kinds of adhesives, an epoxy-based adhesive and an epoxy-based adhesive and an acrylate-based adhesive having a different glass transition temperature. This can be solved by subjecting the surface to silane coupling treatment. The difference between the glass transition temperatures of the two adhesives is 30 ° C. or higher, preferably 40 to 10
The temperature is preferably 0 ° C., and the silane coupling treatment is preferably performed using an organic silane compound having an epoxy group at the molecular end.

Hereinafter, the present invention will be described in detail. Figure 1
An example of the coupler of the present invention is shown, and in FIG. 1, reference numeral 11 is a reinforcing device 11 made of quartz glass. This reinforcer 1
Reference numeral 1 denotes a rectangular parallelepiped gutter in which a square groove 12 is formed. Two optical fibers 13, 13 are spliced in the square groove 12 and fused and drawn to form a melt-stretching coupler body 14. The optical fiber portions 13 and 13 of the coupler body 14 are bonded and fixed to the stiffener 11 by two kinds of adhesives 16 and 17 on both sides of the melt extending portion 15 of the coupler body 14.

At least the adhesive 1 of the reinforcing device 11
Silane coupling treatment is applied to the inner surface of the square groove 12 to which Nos. 6 and 17 are applied. The silane coupling treatment here is an organic silane coupling agent having an epoxy group at the molecular end, for example, γ-glycidoxypropyltrimethylsilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyl. A method in which a solution in which triethoxysilane or the like is dissolved in water, alcohol, a water-alcohol mixed solution or the like is applied to the reinforcing device 11 and dried is used. By this silane coupling treatment, a very thin silane coupling agent thin film having a thickness of 10 to 100 nm is formed on the surface of the reinforcing device 11.

As the two kinds of adhesives, one is an epoxy adhesive 16 and the other is an acrylate adhesive 17. The epoxy adhesive 16 having a glass transition temperature (Tg) of 40 to 50 ° C. is used.
For example, bisphenol A type having a temperature range of 50 ° C. is used.

Further, the glass transition temperature of the acrylate adhesive 17 is 80 ° C. or higher, preferably 90.
Those having a temperature of up to 150 ° C. are used, and specifically, UV-curable or thermosetting epoxy acrylate-based or urethane acrylate-based ones having a glass transition temperature in the above range are used. The difference in glass transition temperature between the two adhesives 16 and 17 is 30 ° C. or higher, preferably 40 to 10
The combination is 0 ° C.

Further, the epoxy adhesive 16 having a low glass transition temperature is applied to the coupler body 14 at a position close to the melt extending portion 15, and the acrylate adhesive 17 having a high glass transition temperature is applied to the epoxy adhesive 16. Adjacent to the position far from the melt drawing portion 15, a part of the optical fiber 13,
The coating 13a of 13 is applied so as to be in contact with the portion where the coatings 13a and 13a are present. The reinforcing device 11 in which the coupler body 14 is housed is covered with an upper lid (not shown) and is fixed with an adhesive or the like to form an optical fiber coupler.

In the optical fiber coupler having such a structure, since the surface of the glass reinforcing device 11 is subjected to silane coupling treatment, the adhesiveness between the two kinds of adhesives 16 and 17 and the reinforcing device 11 is improved. The adhesives 16 and 17 are remarkably improved, and the adhesives 16 and 17 are also strengthened by the large stress generated by the difference in the coefficient of thermal expansion between the adhesives 16 and 17 and the reinforcing device 11.
It does not come off. Further, since two kinds of adhesives, that is, an acrylate adhesive 17 having a high glass transition temperature and an epoxy adhesive 16 having a low glass transition temperature are used, even when exposed to a low temperature environment of about -40 ° C, Even if it is placed at a high temperature of around + 85 ° C, either one of the adhesives sufficiently exhibits its function, and a high adhesive force can be secured in a wide temperature range.

Further, since the two kinds of adhesives 16 and 17 having different glass transition temperatures are used, when the temperature exceeds a certain temperature, the epoxy adhesive 16 having a lower glass transition temperature is softened and changes in temperature. Correspondingly generated stress at the interface will be relaxed here, and the stress at the interface can be reduced. For this reason, the adhesives 16 and 17 themselves are not cracked or peeled off at the interface, stable and high adhesive strength can be secured in a wide temperature range, and durability and reliability are improved.

FIG. 2 shows another example of the optical fiber coupler of the present invention. In this example, two kinds of acrylate adhesive 17 having a high glass transition temperature and epoxy adhesive 16 having a low glass transition temperature are used. This is different from the previous example in that the adhesive of (3) is alternately applied to three places and the coupler body 14 is adhered and fixed to the reinforcing device 11. Coupler body 14
The epoxy adhesive 16 having a low glass transition temperature is provided at a position close to the melt-stretched portion 15 of the
Acrylate-based adhesive 17 having a high glass transition temperature apart from the above, and epoxy-based adhesive 16 having a low glass transition temperature at a position farthest from the melt-stretched portion 15 in contact therewith.
Has been applied. Even with this, the same effects as those of the previous example can be obtained.

Hereinafter, a concrete example will be shown to clarify the action and effect. (Example) A single mode optical fiber is used, and a branching ratio at a wavelength of 1.3 μm is 1: 1 in a 2 × 2 type (3d
The melt-stretched optical fiber coupler body of B) was manufactured by a conventional method. On the other hand, a round groove type silica glass reinforcing device having a length of 48 mm was prepared. A circular groove having a semicircular cross section, a width of 1 mm, and a depth of 1 mm is formed in this reinforcing device, and the outer diameter is 3 mm. After degreasing and cleaning this reinforcer, γ-
About 2% by weight of glycidoxypropyltrimethoxysilane
It was dipped in the aqueous solution at room temperature for about 2 minutes and then dried in an oven at 70 ° C. for silane coupling treatment.

Further, a general-purpose bisphenol A type epoxy adhesive (normal temperature curing type, glass transition temperature about 50 ° C., hereinafter referred to as adhesive A) and an ultraviolet curing type epoxy acrylate type adhesive (glass transition temperature 100 ° C. or higher, Two kinds of adhesives (hereinafter referred to as adhesive B) are prepared. Next, the above-mentioned coupler main body was housed in the round groove of the reinforcing device, and the coupler main body was adhered and fixed in the following three types on both sides thereof. Group I ... Adhesives A and B are used for adhesion and fixing. However, as for the application of the adhesive, as shown in FIG. 2, the adhesive B, the adhesive A, and the adhesive B were separately applied from the side close to the melt-stretched portion. Coating length is 3mm and 4 respectively
mm and 3 mm. Group II: Adhesive B only adhered and fixed. The coating length was 10 mm. Group III: Adhesive A only adhered and fixed. The coating length was 10 mm. Group IV: Made in the same manner as Group I except that the silane coupling treatment was not applied to the stiffener.

With respect to each of these four groups, the number of samples was set to 15, and finally, an upper lid was covered to make it airtight to manufacture four types of couplers. After performing a heat cycle test (40 cycles as one cycle of 6 hours) at −40 ° C. to + 85 ° C. on each of 10 samples of these sample groups, the characteristics were obtained, and the results shown in Table 1 were obtained.

[0019]

[Table 1]

Further, a low temperature heat shock test was conducted on another five samples of each of these sample groups. The test condition is that the sample placed in a room at 20 ° C is -50 ° C within 1 second.
It is dipped in dry ice-ethanol and rapidly cooled. Table 2 shows the results. The denominator of the fraction showing the results in Table 2 indicates the total number of samples, and the numerator indicates the number of samples in which peeling or cracking occurred.

[0021]

[Table 2]

From the above results, it is understood that the sample group I of the present invention exhibits excellent characteristics.

[0023]

As described above, the optical fiber coupler of the present invention uses the epoxy adhesive and the acrylate adhesive having different glass transition temperatures, and the surface of the glass reinforcing device is subjected to the silane coupling treatment. In addition, since the coupler body is adhered and fixed, a high adhesive force can be secured over a wide temperature range, and reliability and durability can be enhanced.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of an optical fiber coupler of the present invention.

FIG. 2 is a perspective view showing another example of the optical fiber coupler of the present invention.

FIG. 3 is a perspective view showing a conventional coupler.

[Explanation of symbols]

11 ... Reinforcing device, 12 ... Groove, 13 ... Optical fiber, 14 ... Coupler body, 16 ... Epoxy adhesive, 17 ... Acrylate adhesive

Front page continuation (72) Inventor Noboru Kawakami 1440 Rokuzaki, Sakura City, Chiba Fujikura Co., Ltd.Sakura Plant (72) Inventor Nobuyuki Misono 1440 Rokuzaki, Sakura City, Chiba Fujikura Sakura Plant, Inc.

Claims (3)

[Claims] 1. A melt-stretching type optical fiber coupler body is fixed and housed in a glass reinforcing device using an epoxy adhesive and the epoxy adhesive and an acrylate adhesive having a different glass transition temperature. An optical fiber coupler in which the surface of the glass reinforcing device is subjected to silane coupling treatment. 2. The optical fiber coupler according to claim 1, wherein the difference in glass transition temperature is 30 ° C. or more. 3. The optical fiber coupler according to claim 1, wherein the silane coupling treatment is performed by using an organic silane compound having an epoxy group at a molecular end.