JPH08146246A - Optical fiber type coupler and its production - Google Patents

Abstract

PURPOSE: To provide an optical fiber type coupler which is inexpensive and has high strength and high performance and a process for producing this coupler. CONSTITUTION: This optical fiber type coupler 1 is formed by tightly and sideways adhering plural optical fibers 2 and fusion stretching the tightly and sideways adhered parts under heating. The plural optical fibers 2 are eccentric core optical fibers 2 which are square in section and in which the cores 5 of the square optical fibers are arranged eccentrically to the tightly and sideways adhered parts. Then, the coupling parts are fusion stretched under heating in the state that the cores exist in the extreme proximity to each other and, therefore, the shorter stretching distance is necessitated. Since the tapered parts are shortened and the diameter of the neck part is increased, the mechanical strength of the coupling part is increased and the reliability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical coupler used in fields such as optical communication and optical measurement, and more particularly to an optical fiber type coupler.

[0002]

2. Description of the Related Art Conventionally, an optical fiber type coupler is manufactured by heating and drawing an optical fiber (circular clad central core optical fiber) having a circular cross section and a core portion at the center thereof.

FIG. 8 shows a conventional optical fiber type coupler, in which two ordinary optical fibers (circular clad center core optical fibers) 11 are arranged in parallel and closely contacted, and the outer periphery of the contacted part is heated. While being fused, it is stretched while being integrally formed. 12 is the optical fiber 1
It is a core located at the center of 1. This optical fiber type coupler has a structure in which the outer diameter thereof is tapered toward the center of the joint portion 13 which is fused and extended from both ends of the optical fiber 11 and is integrated. With the structure of the fusion portion 13 which is fused, stretched and integrated, it is possible to form an equal splitter for equally splitting the light incident on one optical fiber 11 or an optical demultiplexer having wavelength selectivity.

[0004]

However, in the conventional optical fiber type coupler, a large excess loss often occurs due to a defect in its manufacture. Further, since the fused and stretched joint portion becomes thin, it is likely to be broken and requires careful handling. As described above, the conventional optical fiber type coupler has not been satisfactory in terms of price and performance because of difficulty in manufacturing.

In view of the above points, various improvements have been proposed. For example, Japanese Patent Laid-Open No. 62-87910 discloses a manufacturing method for drawing an eccentric base material in which a core is eccentric.
Further, Japanese Patent Laid-Open No. 61-208011 discloses a method in which the clad in the portion to be melt-integrated is partially processed into a flat surface and the flat surfaces are made to face each other and closely adhere to each other to perform melt-integration. The former is not preferable because it is fused and integrated over the entire length of the optical fiber. This is because it is more convenient to connect the optical fiber to both ends of the coupler, as in the conventional optical fiber type coupler shown in FIG. The latter requires high-precision processing when processing the clad into a flat surface, but it is difficult in practice and the mechanical strength of the processed portion deteriorates and the dimensional accuracy is poor. Therefore, it is extremely difficult to manufacture a high strength, low loss coupler that is melt-integrated with good reproducibility.

An object of the present invention is to solve the above-mentioned drawbacks of the conventional optical fiber type coupler, and to provide an inexpensive optical fiber type coupler having high mechanical strength and a manufacturing method thereof.

[0007]

The present invention has the following means in order to solve the above problems.

The optical fiber type coupler according to claim 1 of the present invention is an optical fiber type coupler in which a plurality of optical fibers are contacted and spliced together, and the contacted and spliced portion is heat fused and stretched. Is an eccentric core optical fiber in which the cross section is rectangular and the cores of the rectangular optical fibers are eccentric to the portions where they are in close contact with each other.

According to a second aspect of the present invention, in the method of manufacturing an optical fiber type coupler, an eccentric core optical fiber having a square cross section, and a plurality of optical fibers whose cores are eccentric to one side are arranged so that the cores are close to each other. It is characterized in that the parts are brought into intimate contact with each other, and the portions in intimate contact are heat-fused and stretched to be integrated.

According to a third aspect of the present invention, in the method of manufacturing an optical fiber type coupler, an eccentric core optical fiber having a square cross section and at least three or more eccentric core optical fibers whose cores are eccentric at a vertex angle. The cores are closely contacted so that the cores are close to each other, and the closely contacted portions are heat-fused and stretched to be integrated.

[0011]

According to the optical fiber type coupler of claim 1 of the present invention, a plurality of optical fibers are closely contacted and spliced, and the portion that has been tightly contacted is heat fused and drawn. Since the plurality of optical fibers are prismatic in cross section, and the cores of the prismatic optical fibers are eccentric core optical fibers which are eccentric to the portions where they are intimately attached to each other, the coupling portion is in a state where the cores are closest to each other. Since it is heat-fused and stretched, the efficiency of branching and coupling of light is the best. Also,
The joint is heated and fusion-stretched with the cores closest to each other, so the stretching distance is short, and the taper is short and the neck diameter is large, so the mechanical strength of the joint is strong and reliability is high. improves. Further, since the positions of the eccentric cores can be easily confirmed when the cores of the prismatic optical fibers are closely attached to each other, the coupler can be manufactured with good reproducibility and by simple stretching.

In the method of manufacturing an optical fiber type coupler according to claim 2 or 3 of the present invention, an eccentric core optical fiber having a square cross section, and a plurality of optical fibers whose cores are eccentric to one side or one apex angle are used. The cores are closely attached so that they are close to each other, and the closely attached portions are heat-fused and stretched to be integrated, so that the joint portion can be heat-fused and stretched in a state where the cores are closest to each other. The efficiency of branching and joining is the best. In addition, the joint part can be heat fusion stretched in the state where the cores are closest to each other, so that the stretching distance can be short, and the taper portion is short and the neck diameter is large, so the mechanical strength of the joint portion is large and the reliability is high. improves. Furthermore, when the cores of prismatic optical fibers are closely attached to each other, the positions of the eccentric cores can be easily confirmed, so that the cores can face each other easily with high dimensional accuracy, reproducibility, and simple stretching to produce a coupler. Will also be cheaper.

[0013]

The present invention will be described below in detail with reference to examples. (Embodiment 1) FIG. 1 shows an embodiment of an optical fiber type coupler of the present invention. The optical fiber type coupler 1 of the present embodiment is one in which two prismatic clad eccentric core optical fibers 2 are contacted and spliced, and the contacted and contacted portion is heat fusion stretched to form a coupling portion 3. In the two rectangular clad eccentric core optical fibers 2, the clad 4 has a square cross section as shown in FIG. 2, and the core 5 is eccentric on one side thereof. The eccentric cores 5 face each other and are closely attached to each other, and the portions that are closely attached are heat-fused and stretched to form the joint portion 3.

The optical fiber type coupler 1 having the above construction is shown in FIG.
It is formed as shown in (a) to (d). FIG.
In (a) to (d), for example, as the clad eccentric core optical fiber 2, the clad 4 is a square having a side of 125 μm, and the center of the core 5 having a mode field diameter of 9.5 μm is located at a distance of 25 μm from the nearest side of the outer circumference. A prismatic clad eccentric core optical fiber 2 is used. A part of the coating 6 on the outer periphery of the above-mentioned two rectangular clad eccentric core optical fibers 2 is removed [FIG. 3 (a)], and the eccentric cores 5 with their coating removal portions 7 face each other in the closest state. In this way, they are aligned in parallel and closely attached [FIG. 3 (b)] and fixed to a stretching stage (not shown). The gas burner 9 is brought close to the intermediate portion of the coating removal portion 7 to locally fuse it (FIG. 3C).

After fusion of the closely contacted portions, the heating temperature is lowered to extend the fused portion of the rectangular clad eccentric core optical fiber 2 to form the coupling portion 8 and the extension is performed at an appropriate branching ratio. Stop [Fig. 3 (d)]. The excess loss of the obtained optical fiber type coupler 1 was 0.1 dB or less. The stretched length at this time was 27 mm, and the neck diameter that was the minimum diameter of the joint portion 8 was 100 μm.

Although an example of a square clad eccentric core optical fiber having a square cross section as the square clad is shown here, the square clad eccentric core optical fiber having a regular hexagonal cross section shown in FIG. 4 similarly has high mechanical strength and low optical strength. A loss coupler could be manufactured.

In the above embodiments, the square clad eccentric core optical fiber having a square cross section and the regular hexagonal square clad eccentric core optical fiber have been described as the square clad. In the present example, the square clad eccentric core optical fiber has a square cross section and a regular hexagon. The cross section is not limited to the one having a cross section, and any polygonal shape such as a 3, 4, 5, 6, 7, or 8 octagonal clad may be used as long as the core is eccentric along the side direction.

The polygon may be a regular polygon, but the length of each side may be different. In such an optical fiber, since the eccentric part where the core is eccentric and the eccentric part can be closely contacted via the surface, it is possible to fuse the both optical fibers with good reproducibility, and therefore the coupler can be easily manufactured and the manufacturing cost can be reduced. .

(Embodiment 2) FIG. 5 shows another embodiment of the optical fiber type coupler of the present invention. The optical fiber type coupler 1A of the present embodiment is a three-branch coupler, and the regular hexagonal prismatic clad eccentric core optical fiber 2A shown in FIG. 6 is used as the three prismatic clad eccentric core optical fibers 2A.
As shown in FIG. 6, in the three prismatic clad eccentric core optical fibers 2A, the clad 4 has a regular hexagonal shape, and the core 5 is eccentric at its one apex angle. The eccentric cores 5 are closely contacted to each other so as to be close to each other, and the contacted and contacted portions are heat-fused and stretched to form the joint 3A.

The above optical fiber type coupler 1A is the first embodiment.
In the same manner as above, it can be formed as shown in FIGS. A part of the coating 6A on the outer periphery of the above three clad eccentric core optical fibers 2A is removed [FIG. 7 (a)], and the cores 5A eccentric to the coating removal portion 7A are closest to each other. In such a state, they are aligned in parallel so as to face each other, and are closely contacted and attached [Fig. 7 (b)] and fixed to a stretching stage (not shown). The gas burner 9 is brought close to the intermediate portion of the coating removal portion 7A to locally heat-bond it (FIG. 7C). When the parts that are closely attached are fused,
Square clad eccentric core optical fiber 2 with low heating temperature
The fused portion A is stretched to form the joint portion 8A, and the stretching is stopped at an appropriate branching ratio [FIG. 7 (d)]. In this way, a three-branch optical fiber type coupler 1A is formed.

In the above embodiments, the regular clad eccentric core optical fiber having a regular hexagonal shape is described as the rectangular clad.
The polygonal clad is not limited to the polygonal shape, and may be a polygonal polygon such as a three-, four-, and five-sided clad, and the core may be eccentric along the direction of the apex angle. By doing so, a coupler having 6 branches can be formed in the case of a regular triangle, and a coupler having 4 branches can be formed in the case of a square. Further, in the case of five branches, the core can be formed of a polygon having an eccentric angle of 72 °.

As described above, the polygon may be a regular polygon, but the sides may have different lengths. In such an optical fiber, the eccentric parts whose cores are eccentric can be closely attached,
The optical fibers can be fused with good reproducibility, and therefore the coupler can be easily manufactured and the manufacturing cost can be reduced.

In each of the above embodiments, the eccentricity amount is not particularly limited, but if the eccentricity amount is large, the neck diameter of the taper portion of the coupler becomes large, which is preferable, but there is a drawback that light leakage in the optical fiber portion becomes large. . When the amount of eccentricity is small, light leakage at the optical fiber portion is small, but the neck portion becomes thin, which is not preferable. Therefore, the amount of eccentricity may be determined if necessary.

The optical fiber clad is made of pure silica or silica containing at least one dopant for controlling the refractive index such as B, F, P and Ge, and the core is made of pure silica or Ge, P, Ti and Al. Silica containing at least one dopant for controlling the refractive index is used.

Any heating means such as a microburner or a microheater is appropriately selected and used for heating in the method of manufacturing each of the optical fiber type couplers.

Since each of the above optical fiber type coupler manufacturing methods uses an optical fiber having a uniform length, there is no need for an additional step of flattening a part of the fiber before the coupler is manufactured, and the optical fiber machine by flattening is used. Does not cause deterioration of the mechanical strength.

Since the optical fiber can be easily manufactured by heating and drawing a preform having a shape similar to that of the desired optical fiber, there is no disadvantage in using an optical fiber having a rectangular cross section and an eccentric core.

Since the dimensional accuracy of the optical fiber is good over the entire length, an optical fiber type coupler with good reproducibility, low loss and high strength can be used as compared with the conventional method of flattening a part of the optical fiber, which is difficult in dimensional accuracy. Can be manufactured.

Furthermore, it is necessary to connect the optical fiber type coupler of the present invention to an optical fiber having a circular center section (normal optical fiber). In that case, the optical fiber used in the optical fiber type coupler of the present invention is used. Since it can be easily processed into a connector by inserting it into a ferrule of an ordinary optical connector with a round cross-section, adhesively fixing it, and mechanically polishing the outer periphery of the ferrule centering on the core (centering process with a ferrule), this also poses a problem. Absent.

[0030]

As described above, according to the optical fiber type coupler of the first aspect of the present invention, a plurality of optical fibers are adhered and contacted, and the contacted and adhered portions are heat fusion-stretched. An optical fiber type coupler, wherein the plurality of optical fibers are prismatic in cross section, and the cores of the prismatic optical fibers are eccentric core optical fibers that are eccentric to the portions intimately contacted with each other. Since the cores are heated, fused and stretched in the closest position, the efficiency of light branching and coupling is the best.

Further, since the joint portion is heat-fused and stretched in the state where the cores are closest to each other, the stretching distance is short, and the taper portion is short and the neck diameter is large, so that the mechanical strength of the joint portion is high. Strengthens and improves reliability.

Further, since the positions of the eccentric cores can be easily confirmed when the cores of the rectangular optical fibers are closely attached to each other, the coupler can be manufactured with good reproducibility and by simple drawing.

In the method of manufacturing an optical fiber type coupler according to claim 2 or 3 of the present invention, an eccentric core optical fiber having a square cross section, and a plurality of optical fibers whose cores are eccentric to one side or one apex angle are used. The cores are closely attached so that they are close to each other, and the closely attached portions are heat-fused and stretched to be integrated, so that the joint portion can be heat-fused and stretched in a state where the cores are closest to each other. The efficiency of branching and joining is the best. In addition, since the fusion joint can be heat fusion stretched in the state where the cores are closest to each other, the stretching distance can be short, and the taper portion is short and the neck diameter is large, so the mechanical strength of the joint portion is strong and the reliability is high. improves.

Further, in this case, since the positions of the eccentric cores can be easily confirmed when the cores of the rectangular optical fibers are closely attached to each other, the cores can be easily opposed to each other with good dimensional accuracy and with good reproducibility and simple drawing. The coupler can be manufactured and the manufacturing cost is reduced.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of an optical fiber type coupler of the present invention.

FIG. 2 is a cross-sectional view showing an example of a prismatic clad eccentric core optical fiber used in the optical fiber type coupler of FIG.

3A to 3D are explanatory views of one manufacturing method of the optical fiber type coupler of FIG.

FIG. 4 is a cross-sectional view showing another example of a prismatic clad eccentric core optical fiber used in the optical fiber type coupler of FIG.

FIG. 5 is a front view showing another embodiment of the optical fiber type coupler of the present invention.

6 is a sectional view showing an example of a prismatic clad eccentric core optical fiber used in the optical fiber type coupler of FIG.

7A to 7D are explanatory views of one manufacturing method of the optical fiber type coupler of FIG.

FIG. 8 is a front view showing an example of a conventional optical fiber type coupler.

[Explanation of symbols]

 1 Optical Fiber Type Coupler 1A Optical Fiber Type Coupler 2 Square Clad Eccentric Core Optical Fiber 2A Square Clad Eccentric Core Optical Fiber 3 Coupling Section 4 Cladding 5 Core 6 Coating 7 Coating Removal Section 8 Coupling Section 9 Burner

Claims (3)

[Claims] 1. An optical fiber type coupler in which a plurality of optical fibers are closely attached, and the portions that are intimately attached are heated and fused and stretched, wherein the plurality of optical fibers have a rectangular cross section, and Is an eccentric core optical fiber in which the cores of the optical fiber are eccentric to the portions intimately contacting each other. 2. An eccentric core optical fiber having a rectangular cross section, and a plurality of eccentric core optical fibers whose cores are eccentric to one side are closely attached to each other so that the cores are close to each other, and the closely attached portion is heated. A method for producing an optical fiber type coupler, characterized by comprising fusion-drawing and unifying. 3. An eccentric core optical fiber having a rectangular cross section, and at least three or more eccentric core optical fibers whose cores are eccentric to each other at a vertical angle are closely attached to each other so that the cores are close to each other. A method of manufacturing an optical fiber type coupler, characterized in that the spliced portion is heated, fused and stretched to be integrated.