JPH06167632A - Production of wide-band fiber coupler - Google Patents

Abstract

PURPOSE:To provide a method for production of a wide-band fiber coupler having uniform branching characteristics in an extremely simple way with good reproducibility. CONSTITUTION:An optical fiber 2 having a reduced diameter part 2a and an ordinary optical fiber 2' are fixed at one end. Both fibers are paralleled by intersecting the position at the end of the optical fiber 2 where the diameter is reduced with the optical fiber 2'. Further, the optical fiber 2 is intersected with the optical fiber 2' in the position of another end a' and the both fibers are fixed parallel in this state at the other end. The reduced diameter part 2a comes into perfectly tight contact in the same state with the optical fiber 2' over the entire length thereof at all times over the long straight distance of the intersected parts A, A' at this time. A heating and fusing range B is fused in this state under prescribed heating and fusing conditions and further, the fibers are stretched until a desired branching ratio is obtd., by which the wide-band fiber coupler is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a wideband fiber coupler whose branching ratio is substantially uniform over a wide band.

[0002]

2. Description of the Related Art In recent years, a wavelength division multiplexing communication system utilizing a plurality of wavelengths has been used in an optical communication system. Broadband fiber couplers with reduced wavelength dependence are mainly used in this system. Conventionally, as shown in FIG. 2 (a), this broadband fiber coupler has one optical fiber 21 in which a diameter-reduced portion 21a having a reduced diameter is formed by heating and stretching in advance in the middle portion thereof, and the other fiber is heat-drawn and treated. Not bundled with the normal optical fiber 22, and the reduced diameter portion 21a
The cladding of the optical fiber 22 and the clad of the optical fiber 22 are fused by a heating means 24 such as a burner, and further stretched in the left-right direction to form a coupling portion 23 as shown in FIG. In this way, the diameter-reduced portion 21a is formed in advance, the diameter-reduced portion 21a is fused to another optical fiber 22, and further extended to form the coupling portion 23. As shown in the "wavelength-branching ratio" characteristic diagram, for example, a wavelength of 1.31 μm
The wide-band fiber coupler has a substantially flat branching ratio of 50% at 1.55 μm.

However, when manufactured as shown in FIGS. 2 (a) and 2 (b), a gap is formed between the diameter-reduced portion 21a and the optical fiber 22, so that the diameter-reduced portion 21 is formed by some method.
If a and the optical fiber 22 are not brought into close contact with each other sufficiently, defective fusion tends to occur. Therefore, for example, when bundling the optical fibers 21 and 22, there is also a manufacturing method in which the optical fibers 22 are made to cross each other with a reduced diameter portion 21a so as to be brought into close contact with each other very easily. In the process, the crossing position and the contact state thereof are slightly different due to a slight deviation such as the crossing angle.
Therefore, the heat fusion conditions such as the positional relationship between the intersection and the heating flame are not stable, and it is difficult to uniformly produce the branching ratio characteristics for each product. Further, if they are simply intersected with each other, the contact area is small and sufficient fusion may not be achieved, resulting in poor fusion, resulting in a poor yield.

As described above, the conventional manufacturing method has a problem that it is difficult to manufacture the branching ratio characteristics of the broadband fiber coupler with good reproducibility for each product.

An object of the present invention is to provide a method capable of manufacturing a wideband fiber coupler having a uniform branching ratio characteristic with high reproducibility in order to solve the above-mentioned problems of the prior art.

[0006]

In order to solve the above-mentioned problems of the prior art, the present invention relates to a first optical fiber in which an intermediate portion is heated and drawn by a predetermined length to form a reduced diameter portion. 1
Book or a normal second optical fiber composed of a plurality of fibers is bundled, and the clads of the respective optical fibers are fused and adhered to each other at the contact position between the diameter-reduced portion and the second optical fiber. In a method of manufacturing a broadband fiber coupler in which the fusion-bonding portion is extended in a direction in which both ends of the optical fiber are separated to form a coupling portion, the first ends of the respective optical fibers are aligned and fixed in the first The optical fiber is wound around the second optical fiber only once so as to intersect with the second optical fiber at both end positions of the reduced diameter portion, and each optical fiber is aligned with the other end. Fixed,
A method for manufacturing a broadband fiber coupler in which the fusion and drawing are performed in a state where the diameter-reduced portion having tension applied to both ends and the second optical fiber are in close contact with each other.

[0007]

EXAMPLE An example of the present invention will be described below. Figure 1
(A), (b) and (c) are manufacturing process diagrams for explaining an embodiment of a method for manufacturing a wideband fiber coupler according to the present invention. 1 and 1'are holding jigs, and 2 and 2'have their coatings removed. It is an optical fiber.

The optical fiber 2 has its middle portion heated and softened in advance under a predetermined condition and then stretched by a predetermined length to form a reduced diameter portion 2a. The positions where the diameter of the diameter-reduced portion 2a starts to decrease are the end portions a and a '.

First, as shown in FIG. 1A, one end of the optical fiber 2 and the optical fiber 2'are aligned and fixed in parallel by a holding jig 1.

Next, as shown in FIG. 1B, the optical fiber 2
So as to intersect the optical fiber 2'at the position of one end a, the optical fiber 2 is intersected with the optical fiber 2'from the back side, and both optical fibers 2 and 2'are made substantially parallel while tension is applied. Position the intersection. This intersection is A.

Further, from this state, as shown in FIG. 1C, the optical fiber 2 is intersected with the front side of the optical fiber 2'at the position of the end portion a ', that is, the optical fiber 2 is changed to the optical fiber 2'. With one winding, tension is applied in the same manner as described above to make the other ends of both optical fibers 2 and 2'parallel to each other, and the intersection is positioned. Then, in this state, the pressing jig 1'fixes the other ends of the optical fibers 2 and 2 '. This intersection is A '
And

After the optical fibers 2 and 2'are fixed by the pressing jig 1 ', the clads of both fibers are subjected to a predetermined condition in the heat fusion range B where the thinning portion 2a is in close contact with the optical fiber 2'. The movable means (not shown) fused by heating means (not shown) such as an oxyhydrogen burner, and the holding jigs 1 and 1'are respectively fixed, are holding jigs 1 and 1 '.
Is moved in a direction away from each other, the fused portions of the optical fibers 2 and 2'are drawn at a constant speed, and when the predetermined branching ratio is obtained, the drawing is stopped to complete the broadband fiber coupler.

After aligning and fixing one end in this manner, the optical fiber 2 is moved to another optical fiber at the position of the end portion a of the diameter-reduced portion 2a having a predetermined length and a predetermined shape formed under a predetermined heating and drawing condition. The fiber 2 ′ is positioned at the intersection and the intersection A so that the two fibers are substantially parallel to each other, and the optical fiber 2 ′ is crossed again at the position of the other end a ′ in the winding direction of the optical fiber 2. When the intersection A'is positioned, the thinning portion 2a is always completely adhered to the optical fiber 2'in its entire length over a long straight line distance from the intersection A to the intersection A '. Therefore, it is an extremely easy contact work process, and the same contact state can always be obtained.
In addition, since a long heat-fusing range B is obtained in which the diameter-reduced portion 2a is completely adhered to the entire length, stable and good fusion can be performed with good reproducibility under predetermined heat-fusing conditions.
As a result, the broadband fiber coupler shown in FIG. 3 has a stable branching ratio characteristic and can be manufactured with good reproducibility. In addition, since stable and good fusion can be performed and fusion defects can be reduced, the yield can be improved. Further, since the completed wide-band fiber coupler is fixed in a state where one optical fiber is wound around another optical fiber, the optical fibers at both ends have the same arrangement, which is easy to use.

In the above embodiment, the first optical fiber having the reduced diameter portion is wound around the ordinary second optical fiber once, but the present invention is not limited to this. Alternatively, on the contrary, the ordinary second optical fiber may be wound around the first optical fiber having the reduced diameter portion.

Although the above embodiment relates to a 2 × 2 coupler using two optical fibers, the present invention is not limited to this. Therefore, even if three or more optical fibers are used, the diameter-reduced portion is formed in advance in one first optical fiber, and this is combined with the ordinary second optical fiber bundled with a plurality of fibers. By closely adhering, fusing, and stretching as in the above-described embodiment, a broadband fiber coupler composed of three or more optical fibers with stable branching ratio characteristics can be manufactured with good reproducibility and yield.

[0016]

As described above, according to the method of manufacturing a wideband fiber coupler of the present invention, a predetermined thinning portion is formed.
A first optical fiber and a normal second optical fiber composed of one or a plurality of optical fibers, one end of which is aligned and fixed, and the first optical fiber has two positions at both ends of the reduced diameter portion. Since the second optical fiber is wound around the second optical fiber once and crossed, the thinning portion of the first optical fiber extends its entire length with respect to the second optical fiber over a long straight line distance between the crossing portions. It is possible to obtain a long and heat-bonded area which is always completely adhered in the same state.

As described above, according to the present invention, it is possible to always obtain the same close contact state between the diameter-reduced portion and the second optical fiber. The conversion section and the second optical fiber are always fused under the same condition. Therefore, according to the present invention, a broadband fiber coupler having a stable branching ratio characteristic can be manufactured with good reproducibility by an extremely simple contact method. Further, according to the present invention, a long heat fusion range can be obtained, so that defective fusion can be reduced and yield can be improved.

[Brief description of drawings]

1A, 1B, and 1C are manufacturing process diagrams illustrating an embodiment of a method for manufacturing a wideband fiber coupler according to the present invention.

2A and 2B are manufacturing process diagrams of a conventional wideband fiber coupler.

FIG. 3 is a “wavelength-branch ratio” characteristic diagram of a broadband fiber coupler.

[Explanation of symbols]

 1, 1'Holding jig 2, 2'Optical fiber 2a Diameter reduction part a, a'End part A, A'intersection part B Heating fusion range

Claims (1)

[Claims] 1. A first optical fiber in which an intermediate portion is heated and drawn by a predetermined length to form a reduced diameter portion, and an ordinary second optical fiber composed of one or a plurality of optical fibers is provided. When bundled, the clads of the optical fibers are fused together at the close contact position between the diameter-reduced portion and the second optical fiber, and the fused portions are further extended in a direction in which both ends of each optical fiber are separated from each other. In the method for manufacturing a wideband fiber coupler in which a coupling portion is formed, the first optical fiber and the second optical fiber are aligned with and fixed to one end of the optical fiber with respect to the second optical fiber. Is wound only once so as to intersect with the second optical fiber at both end positions of the optical fiber, and the optical fibers are aligned and fixed at the other end, and tension is applied to the both ends. The fusion in the state of close contact with the second optical fiber And manufacturing method of a broadband fiber coupler characterized in that the stretching is performed.