JPH03255412A - Reinforcing method for optical fiber coupler - Google Patents

Abstract

PURPOSE:To perform the reinforcing process in a short time and to easily insert an optical fiber through a reinforcing case by using a reinforcing case which has a hot melt adhesive arranged on both sides of a through part of a protective member and has the outside peripheral surface coated with a thermally contractible tube. CONSTITUTION:The reinforcing case has a hot melt adhesive 3 arranged on both sides of the through hole in the center of a protective member 2 and has the outside peripheral surface coated with a thermally contractible tube 4. That is, the thermally contractible tube 4 in the vicinity of the through part is thermally contracted to fix the protective member 2 in the reinforcing case. Consequently, an optical fiber for optical fiber coupler is easily inserted through the reinforcing case without moving the protective member 2. Since the hot melt adhesive 3 is used as the adhesive with which an optical fiber coupler is fixed to the protective member 2, it is fused and solidified by temperature. Thus, the work time of fixing to the protective member in the coupler producing process is shortened, and the work in the reinforcing process is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for reinforcing an optical fiber coupler by heating, fusing, and stretching a plurality of optical fibers.

(Prior Art) Conventionally, in an optical fiber coupler, a fused and stretched optical fiber coupler body is usually fixed to a fixing member having a coefficient of linear expansion comparable to that of a quartz optical fiber.

As the fixing member, a plate-shaped member or the like is used, for example, as described in Japanese Utility Model Application Publication No. 64-24308, and an adhesive is used as the fixing method.

Epoxy adhesives or ultraviolet (UV) curing adhesives have been used as conventional adhesives for fixing couplers.

The problem with the conventional technique of fixing using adhesive is that, first, after the optical fiber is fused and drawn, the quartz case is brought close to the fused and drawn fiber, and adhesive is applied to both ends of the quartz case. Since this method uses a method of integrating the optical fiber with the optical fiber, it requires the work of applying adhesive.Secondly, the time required to cure the adhesive is 15 minutes even if it is fast.
Thirdly, after fixing it to the plate-shaped protective member,
Another point is that it is necessary to protect it from outside air such as humidity. When using an ultraviolet curable adhesive, there is also the problem that expensive equipment such as an ultraviolet light source is required.

Therefore, the present inventors developed a method using a hot-melt adhesive. As shown in Figure 2 (A), this protection is achieved by combining a quartz base material 1 with a semicircular cross section that is a partial quartz cylinder, and a quartz member 2 that has a half-cylindrical shape that is made by dividing a quartz cylinder into two. As shown in FIG. 2(B),
A reinforcing case is made by covering a vibrator-shaped heat-melting adhesive 3a and a heat-shrinkable tube (for example, SUMITUBE (registered trademark) manufactured by Sumitomo Electric Industries, Ltd.) 4 thereon.

A method for fixing an optical fiber coupler to this reinforcing case will be explained.

Before clamping the optical fiber to be fused and stretched into the optical fiber coupler manufacturing equipment, insert the optical fiber through the reinforcing case, and leave the reinforcing case in a position away from the fusion and stretching section where it will not be heated. .

After the fusing and stretching processes are completed and an optical fiber coupler with the desired characteristics is obtained, the reinforcing case is moved to the position of the coupler body, and the vicinity of both ends of the reinforcing case is heated to bond the hot-melt adhesive. At the same time, the heat-shrinkable tube is shrunk to fix both ends of the coupler body.

This method allows the protective material such as quartz to move within the reinforcing case, so the optical fiber (before being made into a coupler)
It is difficult to insert the quartz member 2 in the half-cylindrical shape, and it is difficult to install the half-cylindrical quartz member 2 in a fixed position.

Further, as shown in FIG. 2(D), since the external appearance is not cylindrical and has unevenness, there is a problem that it is difficult to store as an optical component and the external appearance is not good.

Due to heating, the heat-melting adhesive 3b may protrude from both sides of the heat-shrinkable tube, and in such a case, the appearance becomes even worse.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned problems, and it is possible to perform the reinforcing process in the manufacturing process of optical fiber couplers in a short time, and also to The object of the present invention is to provide an optical fiber coupler that facilitates the work of inserting a fiber and has an excellent appearance.

(Means for Solving the Problems) In the first aspect of the present invention, in a method for reinforcing an optical fiber coupler, a hot-melt adhesive is disposed on both sides of the through-hole of a protective member having a through-hole in the center. Although the outer periphery was covered with a heat-shrinkable tube, the reinforcing case was made by heat-shrinking the heat-shrinkable tube near the penetration part.
Heating the reinforcing case with the optical fiber coupler inserted so that the coupler main body is located in the penetration part,
The present invention is characterized in that the optical fiber coupler is fixed to the reinforcing case by heat bonding. Further, the second invention is based on the first invention.
The reinforcing case according to the invention is characterized in that the outer peripheral cross-sectional area of the penetration portion of the protective member is made equal to the cross-sectional area of the protective member and the hot-melt adhesive on both sides thereof.

Compared to the length of the heat-shrinkable tube, the total length of the heat-melt adhesive and the through-hole can be made shorter.

As the hot-melt adhesive, an ethylene copolymer resin such as ethylene vinyl acetate can be used.

As the hot melt adhesive, a low melting point metal such as solder can be used.

Wax can be used as the hot-melt adhesive.

(Function) First, the reason why the protection member of the optical fiber coupler of the present invention is provided with a penetrating portion will be explained. An optical fiber coupler constructed by fusion-stretching two optical fibers has a piconical shape with a tapered diameter at the center due to the stretching. In this case, the core diameter is also thinner at the same ratio as the cladding diameter. When the core portion becomes thinner, the light propagating through such an optical fiber coupler has a smaller ability to be confined in the core, and thus the light spreads significantly outside the core. The refractive index difference between the core and cladding is 0.3%,
Normal 1.3μ with core diameter 8μm and cladding diameter 125μm
When a coupler is manufactured using an m-band single mode optical fiber, light spreads over the entire cladding in a portion where the cladding diameter is approximately 30 μm. In the case of such an optical fiber coupler, if the fused portion is dumbbell-shaped, the refractive index of the surrounding medium must be lower than that of the cladding of the optical fiber at the minimum diameter portion. If there is an air layer around it, since the refractive index of the air is lower than the refractive index of the cladding, light can be propagated using the cladding as the core and the air layer as the cladding. In the present invention, by providing the through hole in the fixing member of the optical fiber coupler, it is possible to secure an air layer around the minimum diameter portion of the coupler.

A reinforcing case is a protective member that has a penetration in the center, with hot-melt adhesive placed on both sides of the penetration, and a heat-shrinkable tube covering its outer periphery. By heat-shrinking the sex tube, the protective member can be fixed within the reinforcing case. Therefore, the protective member does not move within the shrink tube, and it becomes easier to pass the optical fiber for manufacturing the optical fiber coupler main body through the reinforcing case.

In addition, by making the outer peripheral cross-sectional area of the penetration part of the protective member equal to the cross-sectional area of the protective member and hot-melt adhesive on both sides of the reinforcing case, when the hot-melt adhesive is heated and melted, the The cross-sectional area of the portion becomes equal to the outer peripheral cross-sectional area of the penetration portion of the protection member, and the outer diameter of the optical fiber coupler becomes equal.

Next, by using a heat-melting adhesive as the adhesive for fixing the optical fiber coupler to the protective member, it can be melted or solidified depending on the temperature, and bonding can be achieved. The solidification time depends on the heating method, but around 2 minutes is sufficient.
The solidification time is short compared to about 155 minutes for epoxy resin adhesives.

Furthermore, by placing the adhesive on the fixing member in advance, the optical fiber coupler does not require an adhesive application process.

(Example) FIG. 1 is a perspective view showing the interior of a reinforcing case for explaining an example of the present invention. In the figure, 1 is a quartz base material with a semicircular cross section, 2 is a quartz member with a half-cylindrical shape, and 3
4 is a heat-melting adhesive, and 4 is a heat-shrinkable tube. A quartz base material 1 with a semicircular cross section and a quartz member 2 with a half-cylindrical shape,
After inserting it into the heat-shrinkable tube 4 in advance, a predetermined length of tubular heat-melt adhesive 3 is inserted from both sides of the shrinkable tube, and only the central part is heated to close the heat-shrinkable tube 4. The quartz base material 1 having a semicircular cross section and the quartz member 2 having a half cylindrical shape are fixed to the center of the heat shrinkable tube 4 by shrinking.

The sum of the cross-sectional area of the hot-melt adhesive and the cross-sectional area of the quartz base material having a semicircular cross section is made approximately equal to the cross-sectional area determined by the outer periphery of the penetrating portion. As a result, the structure of the entire case when heat bonded becomes cylindrical, resulting in a beautiful appearance.

The length of the heat-shrinkable tube is longer than the length of the quartz base material having a semicircular cross section, and also longer than the sum of the lengths of the quartz member having a half-cylindrical shape and the heat-melting adhesive.

Thereby, the heat-shrinkable tube can stop the flow of the hot-melt adhesive and prevent the hot-melt adhesive from leaking to the outside of the reinforcing case during heat-bonding and fixing.

For the purpose of confirming the effects of the present invention, a reinforced case with the following structure was created.

A heat-shrinkable tube with a length of 56 mm, a thickness of 0.1 mm, and an outer diameter of 5 mm, a quartz substrate with a semicircular cross section of 50 mm in length, a radius of 1.75 mm, and a cross-sectional area of 4.8 mm, and an outer diameter of 3. 5m
m, length 25mm, wall thickness 0゜2mm, cross-sectional area 4.8mm
2 half-cylindrical quartz member, outer diameter 4.5 mm, inner diameter 2
．． It has a cross-sectional area of 5.4 rrim2, which is a cylinder with a length of 5 mm and a length of 12 mm cut in half, and is made of quartz with a semicircular cross section on a heat-shrinkable tube using a heat-melt adhesive made of EVA (ethylene vinyl acetate). Insert the base material and the quartz member with a half-cylindrical shape, and heat the 20 mm of the center part with a 180°C heater to shrink it. It was fixed in the center of the shrinkable tube. Next, hot-melt adhesive was inserted from both sides to create a reinforced case with the structure shown in FIG. 1.

When an optical fiber coupler was inserted through this and heated and fixed, the overall appearance became almost cylindrical. The length of the heat-shrinkable tube is preferably increased by about 3 to 5 mm on both sides, and as in the above-mentioned example, even with a length of 3 mm, the extrusion of the hot-melt adhesive could be suppressed.

(Effects of the Invention) As is clear from the above description, according to the present invention, by using a hot-melt adhesive, the time required for fixing the coupler to the protective member in the coupler manufacturing process can be significantly shortened. can. Further, since the adhesive does not solidify during holding or other handling, the coupler manufacturing apparatus can be simplified.

In addition, since the protective member is fixed with a heat-shrinkable tube, the work in the reinforcing process is greatly facilitated, and by specifying the cross-sectional area of the heat-melt adhesive, it is possible to provide an optical fiber coupler that has a good appearance and is easy to store. effective.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the interior of a reinforcing case for explaining an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a reinforcing method previously proposed by the present inventors. . DESCRIPTION OF SYMBOLS 1... Quartz base material with semicircular cross section, 2... Quartz member with half-split cylindrical shape, 3... Heat-melt adhesive, 4... Heat-shrinkable tube.

Claims (2)

[Claims] (1) Although a heat-melting adhesive is placed on both sides of the penetration part of a protective member having a penetration part in the center, and a heat-shrinkable tube is placed over the outer periphery of the protection member, the heat shrinkage near the penetration part The optical fiber coupler is inserted into the reinforcing case made by heat-shrinking the tube so that the coupler main body is located in the penetration part, and the reinforcing case is heated to fix the optical fiber coupler to the reinforcing case by heat bonding. A method for reinforcing an optical fiber coupler, characterized by: (2) According to claim (1), the reinforcing case is a reinforcing case in which the outer circumferential cross-sectional area of the penetration portion of the protective member is equal to the cross-sectional area of the protective member and hot-melt adhesive on both sides thereof. How to reinforce optical fiber couplers.