JPH07140347A - Production of multibranch type optical coupler - Google Patents

Abstract

PURPOSE:To provide the process for easily producing the multibranch type optical coupler featuring decreased variations in a branching ratio, a small size and high mechanical strength. CONSTITUTION:A glass rod 11 to be made into a supporting body formed with a central through-hole 12a and peripheral through-holes 12b... is prepd. and the ends of optical fibers 13... from which coatings at the ends are removed are inserted into these through-holes 12.... Two pieces of the optical fibers 13 are inserted into the central through-hole 12a from its both ends toward the center and are butted against each other in the central part. One piece of the optical fiber 13 is inserted into each peripheral through-hole 12b from its one end toward the other end. The glass rod and the optical fibers are then heated to fuse the glass rod 11 and the optical fibers 13 and are further fusion stretched. Halved glass rods formed by halving the glass rods in its longitudinal direction may be used as well as the glass rod 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multi-branch type optical coupler used for the purpose of branching an optical signal in optical fiber communication, an optical measuring system and the like.

[0002]

2. Description of the Related Art A multi-branch type optical coupler has recently been particularly in demand as the optical fiber communication network is expanded to subscriber systems and optical cable televisions are put into practical use.

There are roughly two types of methods for manufacturing such a multi-branch type optical fiber coupler. One is a method of constructing a multi-branch type optical fiber coupler by connecting a plurality of 2 × 2 type or 1 × 2 type branch optical fiber couplers which are generally manufactured at present in a serial direction. A × 8 type branch optical fiber coupler has a structure as shown in FIG. Here, seven 1 × 2 type couplers 1 ... Are used, and fusion splicing 2 ... The 1 × 2 type coupler 1 is currently mass-produced, and is relatively inexpensive and has excellent characteristics. Therefore, it is an advantage that a high-performance multi-branch type optical fiber coupler can be easily manufactured by using these optical fiber couplers 1. However, in this type, since it has a large number of optical fiber couplers 1 ... And connection points 2 ..., the structure is complicated and downsizing is difficult. Further, since fusion splicing with a large number of optical fiber couplers 1 is required, it takes time and effort to store in a narrow space, and as the number of branches increases, the number of fusion splicing steps also increases, resulting in a significant increase in manufacturing cost. The problem is that it is lost.

Another manufacturing method is a method of manufacturing a multi-branching type optical fiber coupler by fusing and extending a plurality of optical fibers at once. This method is simpler than the above-described method of connecting a plurality of optical fiber couplers because the coupler is manufactured by one fusion drawing, and is an excellent method for miniaturization and reduction of manufacturing cost. Can be said. The manufacturing methods reported so far are described below.

FIG. 9 shows a method of producing a coupler by simply bundling a plurality of optical fibers 3 ... However, when the number of the optical fibers 3 increases, it is difficult to bundle them properly, and there is a drawback that the light is likely to be branched unevenly. FIG. 10 shows a method in which a plurality of optical fibers 3 ... Are arranged around a support rod 4 made of glass or the like and fusion fusion drawing is performed. The cores of the optical fibers 3 are arranged in a ring shape, and there is theoretically a coupling length such that the light incident from one optical fiber 3 is evenly emitted to all the optical fibers 3 ... Compared with, there is an advantage that it is easy to reduce the variation in the amount of light branched to the optical fibers 3 on the output side. Further, since the fusion-bonded extending portion includes the supporting rod 4, it is thick and advantageous in strength. However, a certain number of optical fibers 3 are required to be arranged in a ring shape, the arrangement of the optical fibers 3 is very time-consuming, and a device is required for mass production.

FIG. 11 shows a method in which a plurality of optical fibers 3 ... Are inserted into a glass thin tube 5 and the optical fibers are fused and drawn together with the glass tube 5. This method has the advantage that the arrangement of the optical fibers is easier than the method shown in FIG. However, in order to prevent variations in the amount of branched light, it is necessary that the positional relationship among the optical fibers in the glass tube 5 be kept uniform. Further, in order for the fusion between the fibers in the glass tube 5 to be performed uniformly, the gap in the glass tube 5 must be small. The number of optical fibers 3 satisfying these conditions is limited and, for example, the glass tube 5 is used.
It is known that there are seven optical fibers 3 ... The drawback of this method is that there are many restrictions on the manufacturing conditions.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for easily and inexpensively manufacturing a multi-branching optical coupler which is small in size, has a small variation in branching ratio, and has high mechanical strength. .

[0008]

The object of the present invention is to form a plurality of holes regularly along the longitudinal direction of a glass rod to be a support, and insert a plurality of optical fibers into these holes, respectively. A method of manufacturing a multi-branch optical coupler in which a rod is heated and melt-stretched, and one of the plurality of optical fibers that passes through and passes through a support is used as the support. In each of the plurality of optical fibers that do not pass through or pass through the support, the ends of the two optical fibers are abutted inside each of the glass rods. The end portion of one optical fiber is inserted into the hole from one end of the glass rod serving as the support, and then the glass rod serving as the support is heated and melt-stretched, or the glass rod serving as the support is used. Rule multiple holes along the length A method for producing a multi-branched optical coupler in which a plurality of optical fibers are respectively inserted into these holes, and the glass rod is heated and melt-stretched, and the glass rod serving as a support is cut in two minutes in the longitudinal direction. Then, insert one end of one optical fiber into the hole of each of the divided half-divided glass rods from its one end to the other end, and then insert the other end of each half-divided glass rod into each hole. This is solved by a method in which the optical fibers are brought into contact with each other so that they are in contact with each other, and these half-divided glass rods are fusion-spliced together, and then these are heated and melt-drawn.

An embodiment of the present invention will be described below in detail with reference to the drawings. 1 to 3 show a first example of the manufacturing method of the present invention. First, as shown in FIG. 1, a glass rod 11 serving as a support is prepared. It has several through holes 1
2 ... perforated. The glass rod 11 is made of high-purity quartz glass and has a diameter of about 1 mm and a length of about 30 mm.
A cylindrical one having a diameter of about mm, for example, a quartz glass rod obtained by the VAD method or the like, having a through hole formed by machining, and then heat-stretched to have a predetermined outer diameter and a through hole diameter, etc. Is used. The refractive index of the quartz glass of the glass rod 11 is the same as the refractive index of the cladding of the optical fiber described later. Regarding the composition of the quartz glass, boron or fluorine may be added in addition to pure quartz.

A plurality of through holes 12 are regularly formed along the longitudinal direction of the glass rod 11. In the example of FIG.
One central through hole 12a is formed on the central axis of the glass rod 11, and six peripheral through holes 12b ... Are formed at equal intervals on the same circumference centered on the central axis. The diameters of the through holes 12 are the same and are slightly larger than the outer diameter of the bare optical fiber, for example, about 130 μm.

Next, a plurality of single-mode type optical fibers 13 are prepared, the coating of the end portions thereof is removed, and the end portions are bare wires. Then, as shown in FIG. 2, the ends of the optical fibers 13 are inserted into the through holes 12 of the glass rod 11 serving as a support. At this time, the inside of the through holes 12 ... And the end portion of the optical fiber 13 are thoroughly washed. Then, of the through-holes 12 of the glass rod 11, the central through-hole 12a has end portions of the two optical fibers 13, 13 from both ends of the glass rod 11 toward the center of the central through-hole 12a. The optical fiber 1 at the center of the central through hole 12a.
It is arranged so that the end faces of 3, 13 are butted against each other.

On the other hand, an end of one optical fiber 13 is inserted from one end of the glass rod 11 toward the other end into each of the peripheral through holes 12b. At this time, the optical fiber 13 may be inserted so that the end face of the inserted optical fiber 13 almost reaches the opening on the other end side from the center of the peripheral through hole 12b. Thus, as shown in FIG. 3, one optical fiber 13 penetrates through the central through hole 12a of the glass rod 11 and is inserted into the peripheral through hole 12b ... Is obtained by inserting one optical fiber 13 without penetrating from one end thereof.

Next, the glass rod 11 in this state is fixed by clamps or the like at both ends thereof, and the central portion thereof is heated by an oxyhydrogen flame to insert the optical fibers 13 ... And the glass rod 11.
The target multi-branched optical coupler is obtained by fusing and melting and further heating and stretching the glass rod 11.
During this melt drawing, light is incident from one end of the optical fiber 13 inserted into the central through hole 12a, and the amount of light emitted from each of the fibers 13 extending from the central through hole 12a and the peripheral through holes 12b on the other end is measured. By adjusting the stretching amount while controlling the binding ratio (branching ratio).

According to such a manufacturing method, the plurality of through holes 1
Since the same number of optical fibers 13 ... Are inserted into the glass rod 11 serving as a support on which 2 ... Is formed in a one-to-one correspondence and the melt drawing is performed, the respective optical fibers 13 ... Thus, the multi-branch type optical coupler with a small variation in the branching ratio can be obtained. Further, since the through-holes 12 ... Can be formed at any position of the glass rod 11, a product having a high degree of freedom can be manufactured. Furthermore, dust and the like do not adhere to the surface of the optical fiber 13 when the glass rod 11 is melt-stretched, and this does not cause adverse effects such as increased loss. Further, since the glass rod 11 is provided, the mechanical strength of the joint portion is increased, and the mechanical strength can be further increased by increasing the diameter of the glass rod 11. In addition, since the coating of the optical fiber 13 is removed only at the end portion, the manufacturing is easier than the conventional manufacturing method using the coating whose coating is removed in the middle, and the productivity is improved. Is improved.

4 to 6 show a second example of the present invention. In this example, the glass rod 11 serving as a support
As shown in FIG. 4, eight peripheral through holes 12b ... Are formed on the same circumference at equal intervals, and no central through hole exists. Then, as shown in FIG. 5, the glass rods 1 are inserted into the peripheral through holes 12b ...
Two optical fibers 13 from both ends of 1 toward the center,
Insert the end portions of 13 and arrange them so that the end portions thereof abut each other at substantially the central portion of the peripheral through hole 12b, and the state shown in FIG. 6 is obtained. In this state, the glass rod 11 is heated as in the previous example. Then, they are fused and melt-stretched.

FIG. 7 shows a third example of the present invention. In this example, a glass rod 11 in which a plurality of through holes 12b ... Is formed is halved in the longitudinal direction.
Prepare 14. Then, in each of the through holes 12a ...
The end portion of the optical fiber 13 is inserted, and the end portion of the optical fiber 13 is arranged at a position facing the opening portion on the other end side.

Next, the two half-divided glass rods 1 in this state
4 and 14 are positioned and aligned so that the end faces of the optical fibers 13 which are not extended are in contact with each other and the end faces of the respective optical fibers 13 ... After fusion-splicing into one, they are melt-stretched to form a multi-branched optical coupler.

(Example) Peripheral through hole 12 having a diameter of 130 μm
A glass rod 11 having an outer diameter of 1.0 mm and a length of 30 mm, in which six b ... Are formed on a circle having a diameter of 0.5 mm at equal intervals, was prepared. On the other hand, the single mode optical fibers 13 ...
This was prepared and the coating on one end of each was removed to form a bare wire end having a length of 17 mm and a diameter of 125 μm. Then, after thoroughly cleaning the end portions of the fibers 13 ... And the glass rod 11, the end portions of the respective optical fibers 13 are inserted from both end sides of the respective peripheral through holes 12b. I made it so that both end faces abut.

Then, the central portion of the glass rod 11 in this state was heated to about 1500 to 1600 ° C. with an oxyhydrogen flame to fuse the optical fiber 13 to the glass rod 11 and then melt-stretched. When the stretching amount is 21 mm, the stretching is stopped,
After cooling, a 6 × 6 type multi-branched optical coupler was obtained. The branching ratio between the terminals of this product was measured, and the variation in the branching ratio was determined to be within ± 7%.

[0020]

As described above, according to the method of manufacturing a multi-branching type optical coupler of the present invention, an optical fiber is inserted into a glass rod having a plurality of holes, and the glass fiber is melt-stretched. Since the positional relationship of each optical fiber is maintained as designed, it is possible to manufacture a multi-branch optical coupler with a small variation in branching ratio. Moreover, since holes can be formed in the glass rod at arbitrary positions, it is possible to obtain a glass rod having a high degree of freedom in design. In addition, since a glass rod is present in the stretched portion, one having high mechanical strength can be obtained. Further, since the optical fiber with the coating on the end removed is inserted into the hole, the manufacturing is easier and the productivity is improved as compared with the conventional optical fiber with the coating on the middle part removed and used. The effect of is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first example of the present invention.

FIG. 2 is a sectional view showing a first example of the present invention.

FIG. 3 is a perspective view showing a first example of the present invention.

FIG. 4 is a perspective view showing a second example of the present invention.

FIG. 5 is a cross-sectional view showing a second example of the present invention.

FIG. 6 is a perspective view showing a second example of the present invention.

FIG. 7 is a perspective view showing a second example of the present invention.

FIG. 8 is a configuration diagram showing an example of a conventional multi-branching coupler.

FIG. 9 is a perspective view showing an example of a conventional manufacturing method.

FIG. 10 is a perspective view showing another example of a conventional manufacturing method.

FIG. 11 is a perspective view showing another example of a conventional manufacturing method.

[Explanation of symbols]

11 ... Glass rod, 12 ... Through hole, 12a ... Central through hole,
12b ... Peripheral through-hole, 13 ... Optical fiber, 14 ... Half glass rod

Claims (4)

[Claims] 1. A plurality of holes are regularly formed in a glass rod as a support along the longitudinal direction, a plurality of optical fibers are inserted into these holes, and the glass rod is heated and melt-stretched. A method of manufacturing a multi-branch type optical coupler, of the above-mentioned plurality of optical fibers, which penetrates and passes through a support, the end portions of the two optical fibers are formed from the both ends of the glass rod serving as the support to the holes. The ends of these two optical fibers are abutted inside the glass rod, and one of the plurality of optical fibers that does not penetrate or pass through the support is the end of one optical fiber. Is inserted into the hole from one end of a glass rod serving as a support, and then the glass rod serving as a support is heated and melt-stretched, thereby producing a multi-branched optical coupler. 2. A glass rod serving as a support is regularly formed with a plurality of holes along its longitudinal direction, a plurality of optical fibers are inserted into these holes, and the glass rod is heated and melt-stretched. A method of manufacturing a multi-branch type optical coupler, in which a glass rod as a support is divided into
Insert the end of one optical fiber into the divided hole of each half-divided glass rod from one end to the other end. Then, each optical fiber projects the other end of each half-divided glass rod. A method for producing a multi-branching type optical coupler, which comprises bringing these half-divided glass rods into fusion contact with each other by bringing them into contact with each other and then heating and melting and stretching them. 3. A multi-branch type optical coupler manufactured by the manufacturing method according to claim 1. 4. A multi-branching type optical coupler manufactured by the manufacturing method according to claim 2.