JPH05297240A - Star coupler and its manufacture - Google Patents

Abstract

PURPOSE:To provide a star coupler with its tapered part strength increased and establish a method of easily manufacturing such couplers by forming a tapered part on a part of a multi-core fiber cable consisting of optical fibers which are embedded in glass, and making photo-coupling of these optical fibers with each other. CONSTITUTION:A star coupler 1 is composed of a core 2, optical fibers 4 each having a core 2 and clad 3, and glass 5 as a support. Each each of this star coupler is formed in multi-core fiber where the optical fibers 4 are embedded in the glass support 5, and in the middle thereof a tapered part 6 is formed. The tapered part 6 is formed by ductilely stretching this multi-core fiber under heating, or by simultaneously applying a twine. This type of star coupler has a greater dia. in the stretched part than a conventional star coupler of melt attaching elongation type, so that it is stable against external force, and further because of this structure in which the whole tapered part is embedded in glass, there is no risk of changing the optical characteristics even though external force is applied to the star coupler, which is thus stable in mechanical and optical terms.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a star coupler for distributing, merging or wavelength multiplexing / demultiplexing light and a method for manufacturing the same.

[0002]

2. Description of the Related Art A star coupler is an optical component which has a function of emitting light to each of n output terminals when light is input to any one of m input terminals. There are various types of star couplers, and the most mass-produced one is the fusion stretch type star coupler. This fusion-stretch type star coupler, after putting a plurality of optical fibers together,
A suitable heat source, for example, a combustion gas burner such as an oxyhydrogen flame burner is used for heating and fusion, and then the film is stretched by stretching in the longitudinal direction. As a result, the core of the fiber in the stretched portion is thinned and a tapered portion is formed. Since the cores approach each other in the tapered portion, electromagnetic coupling occurs between the propagation modes of these cores, and the cores act as a star coupler.

[0003]

However, in the production of the above fusion-stretched star coupler, it is difficult to uniformly fuse many fibers, so that it is difficult to stabilize the fusion-stretching conditions. Its production requires a high degree of skill. Further, since the tapered portion of the star coupler manufactured by the above method is thinned by stretching, it has a drawback of being inferior in impact resistance and requires a reinforcing step. The present invention has been made in view of the above circumstances, and provides a star coupler in which the strength of a tapered portion is improved and a method for easily manufacturing the star coupler.

[0004]

A star coupler of the present invention comprises a plurality of optical fibers each having a core and a clad, wherein a taper portion is formed in a part of a multi-core fiber arranged in glass. The above problem is solved by adopting a configuration in which optical coupling is performed between fibers.

Further, as a method of manufacturing a star coupler, a plurality of optical fiber preforms having a core portion and a clad portion are bundled and arranged in a through hole of a glass tube and drawn to form a multicore fiber. Then, the cut portion was heated and stretched, or twisted at the same time as the stretching to form the tapered portion, which was a means for solving the above problems.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 shows an embodiment of a star coupler according to the present invention. This star coupler 1 comprises a plurality of (seven) optical fibers 4 having a core 2 and a clad 3, and a supporting glass body 5. It is configured. Both ends of the star coupler are arranged in the supporting glass body 5 and the optical fiber 4
It is a multi-core fiber with ... arranged,
A taper portion 6 is formed in the middle portion.

Like the ordinary optical fiber, each of the optical fibers 4 is provided with a core 2 having a high refractive index made of, for example, germanium oxide-doped quartz and a clad 3 having a low refractive index and made of quartz around the core 2. It is a thing. The optical fibers 4 may have the same structure or different structures. Also, the outer diameter of the optical fibers 4, that is, the core interval of the multi-core fiber is 125 μm.
m is a general specification. In addition, the supporting glass body 5
Although the material of the glass is not particularly limited, for example, quartz glass or the like can be used. One of the optical fibers 4 is located substantially in the center of the supporting glass body 5, and the six optical fibers are evenly arranged around and in contact with the optical fiber 4 therein. It is arranged in an aligned state. Also in the taper portion 6, although the diameters of the optical fibers 4 are reduced, this aligned state is maintained.

The taper portion 6 is formed by a method in which a multi-core fiber is stretched under heating, or a twist is applied at the same time as stretching, and the optical fibers 4 forming the multi-core fiber are narrowed so that the cores approach each other. However, optical coupling occurs. Therefore, an n × n type star coupler is formed by n optical fibers.

Since such a star coupler has a larger diameter at the stretched portion than a normal fusion-stretching type star coupler, it is stable against external force, and the entire tapered portion is embedded in the glass. Even if an external force acts on the star coupler, the optical characteristics do not change, and it is mechanically and optically stable.

Next, a method for manufacturing the star coupler of the present invention will be described. 2 to 5 are views showing an embodiment of the method of the present invention. In FIG. 2, reference numeral 7 is an optical fiber preform. The optical fiber preform 7 has a high-refractive-index core portion 8 made of, for example, germanium-doped quartz, and a cladding portion 9 made of quartz around the core portion 8. The optical fiber base material 7 may be an optical fiber base material used for ordinary communication, and a single mode type or a multimode type GI type may be used depending on the application. Further, the optical fiber preforms 7 may all be the same or different. The diameter of the optical fiber preform 7 is preferably about 5 to 20 mm. Hereinafter, the number of the optical fiber preforms 7 ... Used in this embodiment is indicated as n.

As shown in FIG. 2, the glass tube 10 is of a cylindrical type having a circular through hole 11 formed in its longitudinal direction. The material of the glass of the glass tube 10 is not particularly limited, but quartz glass or the like can be used.
The shape of the through hole 11 is not particularly limited, but the size of the through hole is as shown in FIG.
It is preferable that the gap between the aggregate 10 and the through-hole 11 is set to 1 to 2 mm when the aggregates are inserted in a bundle. Further, the wall thickness of the glass tube 8 is from the viewpoint of obtaining a star coupler having a desired finished outer diameter.
It is appropriately selected in consideration of the balance with the diameter of the optical fiber preform 7.

Next, as shown in FIG. 2, the glass tube 10
Into the through-hole 11 of the optical fiber preform 7, n aggregates are bundled and inserted to form an aggregate 12. At this time, it is preferable to dispose one optical fiber preform 7 serving as an input terminal at the time of completion in the center and evenly dispose the remaining optical fiber preforms 7 around the central optical fiber preform 7. ..

Next, the assembly 12 is attached to a drawing furnace (not shown), and the tip of the assembly 12 is locally heated by a heating device (not shown) and drawn into a fiber shape, which has n cores. The multi-core fiber 13 is manufactured (FIG. 3A). In this step, the long multicore fiber 13 is manufactured. At this time, the core interval (fiber diameter) can be freely selected, but as a general specification, it is preferable to set the core interval to 125 μm. The outer diameter of the multi-core fiber 13 is
It is preferable to set it in the range of 0.25 to 5 mm.

Next, the multicore fiber 11 thus produced is cut into an appropriate length of about several cm (FIG. 3B), and the center of the cut multicore fiber 11 is
As shown in FIG. 4, while being heated by a heating means such as the oxyhydrogen gas burner 14, the taper portion 6 is formed by pulling in the longitudinal direction and stretching the heated portion to form the star coupler 1. Further, twisting may be applied at the same time when the heated portion is stretched.

In this heating and drawing operation, an optical fiber is connected to one end of each of the n optical fibers 4 forming the multi-core fiber 11 (not shown), and one optical fiber at the center of the other side is connected. When the light is incident on the output side, the output light intensity of the n optical fibers connected to the output side is monitored, the coupling degree is calculated from the output light intensity from the n output side optical fibers, and the appropriate coupling is obtained. It is desirable to adjust the amount of stretching so that the same degree (power of n cores) can be obtained.

The star coupler 1 produced in this way
Is inserted into the reinforcing pipe 15 made of SUS or the like,
After polishing both ends, it is put into practical use.

[0017]

As described above, in the star coupler of the present invention, a plurality of optical fibers each having a core and a clad are formed by forming a taper portion in a part of a multi-core fiber arranged in glass. Optical coupling is performed between the optical fibers.

Therefore, since the fused stretched portion can be embedded in the supporting glass body having a low refractive index, the optical characteristics do not change even when an external force acts on the coupler, and the stability is extremely excellent.

The method of manufacturing the star coupler of the present invention is
A plurality of optical fiber preforms having a core part and a clad part,
A tapered portion is formed by arranging them in a through hole of a glass tube in a bundle, drawing them to form a multi-core fiber, and then heat-drawing a part of the multi-core fiber, or applying twist at the same time as the drawing. It is a thing.

Therefore, a star coupler can be obtained by heating and drawing one multi-core fiber, which is easier to handle and easier in operation than the conventional method of fusion-drawing a plurality of fibers. In addition, since the tapered portion is protected by the supporting glass body at the stage of heating and stretching, the subsequent reinforcing step is not necessary, and by simply selecting the shape of the glass tube, it is possible to easily increase the outer diameter and mechanical strength. A large star coupler can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a star coupler of the present invention.

FIG. 2 is a diagram for explaining one embodiment of a method for manufacturing a star coupler according to the present invention, and is a schematic perspective view of a step of inserting an optical fiber preform into a glass tube.

FIG. 3 is a diagram for explaining one example of a method for manufacturing a star coupler according to the present invention, and is a schematic side view showing a step of manufacturing a multi-core fiber by drawing and cutting.

FIG. 4 is a diagram for explaining an example of the method for manufacturing a star coupler according to the present invention, and is a perspective view showing a drawing process of a multi-core fiber.

FIG. 5 is a diagram for explaining one embodiment of the method for manufacturing a star coupler according to the present invention, and is a schematic perspective view showing a polishing step.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Star coupler, 2 ... Core, 3 ... Clad, 4 ... Optical fiber 5 ... Support glass body, 6 ... Tapered part, 7 ... Optical fiber base material, 8 ... Core part 9 ... Clad part, 10 ... Glass tube, 11 … Through holes, 13
… Multi-core fiber 14… Gas burner

Claims (3)

[Claims] 1. A plurality of optical fibers having a core and a clad, wherein a taper portion is formed in a part of a multi-core fiber arranged in glass, and optical coupling is performed between the optical fibers. Star coupler to do. 2. A plurality of optical fiber preforms each having a core part and a clad part are bundled and arranged in a through hole of a glass tube, and these are drawn to form a multicore fiber. A method for producing a star coupler, which comprises heating and stretching a part. 3. The method for producing a star coupler according to claim 2, wherein twisting is applied simultaneously with the stretching.