JPS61102613A - Production of tapered optical fiber bundle - Google Patents

Abstract

PURPOSE:To obtain an optical fiber bundle which is small in the variance of the light distributed to each output optical fiber when said bundle is used for an optical distributor by winding an arraying member to the heated part of plural pieces of the bundled optical fibers, heating the bundled fibers and stretching the same. CONSTITUTION:Plural pieces of the optical fibers 11 are bundled and the arraying member 12 is wound to the heating part thereof. The bundle is then heated and stretched. The homogeneous optical fiber having the refractive index smaller than the refractive index of the clad layer of the fibers 11 is preferably used or a Pt wire or Pt alloy wire is preferably used as the member 12. Since the arraying state of the fibers 11 is held by the arraying member (auxiliary fiber) 12 in the above-mentioned manner, the fibers 11 are surely welded even in the case of a large number of the fibers. No torsion is applied to the fibers in the stage of tapering the same and therefore the light is evenly distributed to all the output optical fibers when the tapered optical fiber bundle obtd. in the above-mentioned manner is used for the optical distributor. The auxiliary fiber to be welded in the stage of tapering has no influence on the optical loss and the arraying member consisting of the Pt wire prevents the intrusion of impurities to the optical fiber bundle and is therefore preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a tapered optical fiber bundle used, for example, as an optical distributor for optical fiber communications.

[Technical background of the invention and its problems]

FIG. 2 is an example of an application of a tapered optical fiber bundle. In the diagram showing the optical splitter, 211.
212 is a tapered optical fiber bundle, and 22 connects these optical fiber bundles 211° and 212. It is a mixer rod with a uniform refractive index. The optical operation of this optical distributor is as follows. Now, the optical fiber bundle 21 on the left
1 as the input side, light incident on any optical fiber of this optical fiber bundle 211 is converted from a waveguide mode to a cladding mode at the tapered portion and mixed. Roughly, the light is almost completely mixed by the mixer rod 22 and propagated to the optical fiber bundle 212 on the right side.
The cladding mode is converted into a waveguide mode and uniformly distributed to each optical fiber constituting the tapered optical fiber bundle 212. For example, if optical fiber bundle 211 consists of 0 optical fibers and optical fiber bundle 212 consists of m optical fibers, this optical splitter acts as an nxm optical splitter.

In addition to the above applications, the tapered optical fiber bundle can also be used in 1xn optical splitters, various optical couplers, and the like.

FIG. 3 shows a conventional method of manufacturing a tapered optical fiber bundle constituting such an optical distributor. Figure 3 (a
), a plurality of cleaned optical fibers 31 are bundled in a close-packed state, and a part of them is heated using a heating means such as a burner 32 as shown in FIG. 3(b). This is stretched to form a tapered portion as shown in FIG. 3(C).

The tapered optical fiber bundle thus produced has an integrated structure in which the cladding layers of each optical fiber are fused to each other at the tapered portion.

By the way, in such a conventional method for manufacturing an optical fiber bundle, as the number of optical fibers to be bundled increases, the yield rate of completely fusing each optical fiber at the tapered portion tends to decrease. The number of optical fibers is usually 2 to 100, but if there are, for example, about 30 optical fibers, the yield in which all the optical fibers are fused will be about 20%.

A known method for improving the production yield of tapered optical fiber bundles when the number of optical fibers increases is to pull the optical fiber bundles while twisting them. The manufacturing process is shown in FIG. As shown in FIG. 4(a), a plurality of optical fibers 31 are bundled in a close-packed state, and a part of the optical fibers 31 is heated with a heating means such as a burner 32, as shown in FIG. 4(b). By pulling the bundle of optical fibers 31 while applying twist, a tapered portion is formed as shown in FIG. 4(C). In this case, to ensure high yield,
It is known from experience that the twisting angle needs to be 180 degrees or more.

However, experiments have shown that when a tapered optical fiber bundle obtained through processing with such twisting is used in an optical distributor as shown in Figure 2, the ability to evenly distribute light deteriorates. Recognized as f1. The causes of this are: ■ The way the bundled optical fibers are twisted is different between those located near the center and those located on the outer periphery. ■ When twisting is applied, the alignment of the optical fibers is disrupted, and this is caused by the disruption of alignment. It is conceivable that different bending stresses are applied to each optical fiber, and as a result, the guided mode and cladding mode are not converted and reconverted uniformly.

(Object of the Invention) The present invention aims to improve the above-mentioned drawbacks, and provides a method for manufacturing with high yield a tapered optical fiber bundle with small variations in light distributed to each output optical fiber when applied to an optical distributor. The purpose is to provide.

[Summary of the invention]

The present invention bundles a plurality of optical fibers into a nearly dense state,
The present invention is characterized in that an alignment member is wound around this, and while heating a part of the plurality of optical fibers, the bundle of optical fibers is stretched and processed into a tapered shape while minimizing twisting.

〔Effect of the invention〕

According to the present invention, since the alignment member keeps the bundle of optical fibers more closely aligned, it is possible to increase the success rate of thermal fusion during taper processing, and therefore manufacture a tapered optical fiber bundle. Yield can be increased. Furthermore, since the optical fiber bundle is tapered without twisting, when the tapered optical fiber bundle obtained by the method of the present invention is applied to an optical splitter, the light is evenly distributed to each output optical fiber. You can get the effect of becoming.

[Embodiments of the invention]

The present invention will be explained in detail below.

FIG. 1 shows the manufacturing process of one embodiment.

First, as shown in FIG. 1(a), a plurality of cleaned optical fibers 11 are bundled in a substantially close-packed state, and an alignment member made of, for example, auxiliary fibers 12 is wound around this. Step 1 where the optical fiber 11 is made of multi-component glass.
In the case of an index type fiber, the auxiliary fiber 12 has a refractive index lower than the refractive index of the cladding layer of the optical fiber 11 and has a softening point almost equal to that of the optical fiber 11.

A homogeneous glass fiber without a core is used. Both ends of this auxiliary fiber 12 are fixed to the bundle of optical fibers 11 mechanically or using an adhesive or wax (hereinafter, as shown in FIG. 1B), a burner 13 or the like is attached. A part of the bundled optical fibers 11 is heated by a heating means, and the optical fibers 11 are stretched and tapered as shown in FIG. 1(C) while minimizing twisting.

According to this embodiment, as a result of maintaining the aligned state of the bundled optical fibers 11 by the auxiliary fibers 12, all the optical fibers are reliably fused even when there are a large number of optical fibers. Further, since no twist is applied during taper processing, when an optical distributor is constructed using the obtained tapered optical fiber bundle, light is evenly distributed to each output optical fiber. Furthermore, in this embodiment, the optical fiber 1 is used as the auxiliary fiber 12.
Since a glass fiber having a refractive index lower than the refractive index of the cladding layer 1 is used, after the taper processing, the auxiliary fiber 12 acts as the cladding layer of the optical fiber bundle. Therefore, there is almost no loss of light due to this auxiliary fiber 12.

It will be clarified based on data that the optical distributor constructed using the tapered optical fiber bundle according to this example has excellent characteristics. FIG. 5 is a histogram of excess loss for all input fiber and output fiber combinations of the optical distributor using the tapered optical fiber bundle obtained in this example. Here, the excess loss refers to the difference between the loss when ideal optical distribution is performed (for example, 3 dB in the case of two distribution) and the actual loss including loss due to other factors. FIG. 6 is a histogram of excess loss of an optical splitter using a tapered optical fiber bundle according to the conventional method explained in FIG. As is clear from comparing the two, the uniformity of light distribution in the optical distributor using the tapered optical fiber bundle according to this example is higher than that in the optical distributor using the tapered optical fiber bundle according to the conventional method. much better than.

The present invention is not limited to the above embodiments.

For example, the number of auxiliary fibers does not need to be one; two or three may be used depending on the number of optical fibers to be bundled. Further, in the above embodiment, an auxiliary fiber, that is, a glass fiber having a lower refractive index than the cladding layer of the fibers constituting the tapered optical fiber bundle is used as the alignment member, and this auxiliary fiber is pulled together during taper processing, and the auxiliary fiber is directly clad in the cladding layer. Although the optical fiber bundle is left as a layer, if the optical fiber bundle is composed of multi-component glass fibers having a low softening point, a Pt wire or a Pt alloy wire, which does not melt when heated, can also be used as the auxiliary fiber. P like this
If a t-wire or a Pt alloy wire is used, unlike other metal wires, it is possible to prevent impurities from entering the optical fiber bundle. Further, in the present invention, the alignment member may be wrapped around not only the entire area of the heating section but also a part of the tapered section. In addition to a burner, a gas discharge, a CO2 gas laser, or the like can be used as the heating means.

[Brief explanation of drawings]

FIGS. 1(a) to (C) are diagrams showing the manufacturing process of a tapered optical fiber bundle according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of the configuration of an optical distributor using a tapered optical fiber bundle. Figure, Figure 3 (
a) to (C) are diagrams showing an example of a manufacturing process for a conventional tapered optical fiber bundle; FIGS. 4(a) to (C) are diagrams showing another example of a manufacturing process for a conventional tapered optical fiber bundle; FIG. 5 is a diagram showing the excess loss histogram of the optical splitter constructed using the optical fiber bundle obtained in the example, and FIG. 6 is a diagram showing the excess loss histogram of the optical distributor constructed using the optical fiber bundle obtained in the example. FIG. 6 is a diagram showing an excess loss histogram of the configured optical splitter. 11... Optical fiber, 12... Auxiliary fiber (alignment member), 13... Burner. Applicant's representative Patent attorney ± 7 Takehiko Suzue Figure 2 Figure 3 Figure 4 Figure 5 8 size illumination (dB) Figure 6

Claims (3)

[Claims] (1) In a method of manufacturing a tapered optical fiber bundle by bundling multiple optical fibers and heating and stretching a part of the fibers, an alignment member is wrapped around the heated portion of the bundled optical fibers and heated. A method for manufacturing a tapered optical fiber bundle, which comprises performing a stretching process. (2) The alignment member is made of an optical fiber, and is made of a homogeneous material whose refractive index is equal to or lower than the refractive index of the cladding layer of the plurality of optical fibers. A method for manufacturing a tapered optical fiber bundle. (3) The method for manufacturing a tapered optical fiber bundle according to claim 1, wherein the alignment member is made of a Pt wire or a Pt alloy wire.