JPH02235005A - Production of optical coupler - Google Patents

Abstract

PURPOSE:To allow the reduction in the size of the optical coupler obtd. by curving the coating removed parts of two pieces of optical fibers at a suitable curvature in the direction where these parts are brought near to each other to cause a point contact and stretching these parts while the contact point is welded by heating. CONSTITUTION:The coating removed parts 12 and 22 of the optical fibers 10, 20 are inserted between pins 71 to 73, 81 to 83 on stretching bases 70, 80 and are disposed in parallel. The parts 12, 22 are so guided by suitable jigs as to curve in the directions where these parts are brought near to each other; in addition, the base 80 is brought near to the base 70 to bring both 12, 22 into point contact with each other. The contact point is heated in this state from both sides by gas burners 91 and 12 and is thereby welded. While the welded part is heated by the burners 91, 92, the base 80 is moved gently apart from the base 70 to stretch the welded part in the axial direction. The optical coupler which is drastically shortened in the length of the coating removed parts 12, 22 at a desired coupling ratio is obtd. in such a manner.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention. relates to a method of manufacturing an optical coupler in which two optical fibers are coupled.

``Prior art J'' Fused drawing method, polishing method, and etching method are known as methods for manufacturing an optical coupler that combines two optical fibers, but the manufacturing method is relatively simple. For this reason, the fusion drawing method is generally used.There are several methods for the fusion drawing method, but among them, the fusion drawing method using parallel alignment has the advantage of being able to obtain an optical coupler with less light loss. This fusion-stretching method using parallel alignment has been widely used since the 12th
Covering 5 over a sufficient length as shown in the figure.
Two optical fibers 50 and 6 with 1 and 61 removed
0 to the clamps 77, 87 and holder 78.8, respectively.
The clamps 77 and 87 are closed while applying appropriate tension to the optical fibers 50 and 60, respectively.
The stripped parts 52 and 62 of 0 and 60 are brought into line contact in the area between the clamps 77.87, and the stripped parts 52 and 62 are gripped inside the clamps 77 and 87 by the holders 78 and 88, and then stripped. The center of the parallel alignment region between the clamps 77 and 87 of the portions 52 and 62 is heated and fused by gas burners 91 and 92, and then the stretching table 80 is heated while the fused portion of the coated portions 52 and 62 is heated by the gas burners 91 and 92. By moving away from the stretching table 70, the fused portion of the coated removed portions 52 and 62 is stretched in the axial direction. ``Problems to be Solved by the Invention'' However, the conventional fusion-drawing method using parallel alignment described above involves bringing the coat-removed portions 52 and 62 of the two optical fibers 50 and 60 into line contact, and heat-fusion and heat-drawing. Therefore, sufficient length is required for the coating removal parts 52 and 62, which increases the size of the optical coupler obtained as a single component, which is disadvantageous in that it hinders the miniaturization of various devices in which the optical coupler is incorporated. .

Specifically, in the conventional fusion stretching method using parallel alignment, the coating removed portions 52 and 6 before stretching are
The actual length of the cladding fusion region 2 is about 2 mm, but the clamp 77.87 of the cladding removed portions 52 and 62
In practice, approximately 8 mm is required as the length of the parallel alignment head region between the two, and in order to avoid giving unreasonable curvature to the optical fibers 50 and 60, the length from one end of the sheathing removed portion 52.62 to the clamp 77, and coating removal portion 52.
Since the length from the other end of 62 to the clamp 87 needs to be at least about 6 mm, the length of the coated removed portions 52 and 62 before stretching is at least 20 mm.
The length of the optical coupler obtained as a single part is determined by the length of the optical coupler obtained as a single component, and the dimension of the optical coupler obtained will greatly exceed 20 mm.

Accordingly, the present invention provides a method for manufacturing an optical coupler using a fusion-drawing method, in which the dimensions of the resulting optical coupler can be made significantly smaller than in the case of a conventional fusion-drawing method using parallel alignment. The performance of the optical coupler produced is completely the same as that of the conventional fusion-stretching method using parallel alignment.

"Means for Solving the Problem" In the invention as claimed in claim 1, the coated portions of two optical fibers are arranged in parallel with appropriate tension applied to each, and then the two optical fibers are Curve the removed parts of the parts with an appropriate curvature in the direction of approaching each other and bring them into point contact.
Next, the contact point is heated and fused, and then the fused portion is stretched in the axial direction while being heated. The invention of claim 2 is a case in which the two optical fibers are linear polarization-maintaining optical fibers each having a stress applying part in the cladding, and in the invention of claim 2, the two linear polarization-maintaining optical fibers are The removed portions of the two linear polarization-maintaining optical fibers are placed parallel to each other with their respective principal axes of birefringence set and an appropriate tension applied. They are curved with an appropriate curvature in the direction of approach to bring them into point contact, then the contact points are heated and fused, and then the fused portion is stretched in the axial direction while being heated.

"Function" In the manufacturing method of the invention of claims 1 and 2 which takes the above method, the contact points of the coated parts of two optical fibers are heated and fused, and the fused part is heated and stretched. ,
An optical coupler is obtained in which the claddings of the two optical fibers are fused at the center of the removed portion, and the core diameter is smaller than the original diameter. Further, in the manufacturing method of the invention of claim 2, in particular, the birefringent principal axis direction of each of the two linear polarization maintaining optical fibers is set before the coated removed portions of the two linear polarization maintaining optical fibers are brought into point contact. An optical coupler can be obtained in which the birefringence principal axes of the linear polarization-maintaining optical fiber have a desired relationship.

Then, the coated parts of the two optical fibers are curved with an appropriate curvature in a direction that brings them closer to each other so that they make point contact.
The length of the removed portion of the two optical fibers can be significantly shorter than when using the conventional fusion drawing method using parallel alignment, and the dimensions of the optical coupler obtained as a single component can be reduced compared to when using the conventional parallel alignment method. The size can be significantly reduced compared to the case using the fusion drawing method.

In addition, since the cladding fusion region is formed by heating and fusing the points where the coating removed portions of two optical fibers are in contact with each other, this is the same as the conventional fusion drawing method using parallel alignment, so that light 111 is lost. The performance of the optical coupler obtained is completely the same as that of the conventional fusion-stretching method using parallel alignment.

"Example" FIGS. 1 to 3 show each step in an example of the manufacturing method of the invention according to claim 1.

First, as shown in FIG.
0 and 20 in bins 71-73 and 81-83, respectively.
and a holder 75.85, and placed over two stretching tables 70.80 arranged at a predetermined distance from each other,
Connect each stripped portion 12 and 22 to a pin 71.7.
2ma and Hi7B 1. 8 2 questions and bin 72.73
The optical fibers 10 and 20 are placed in parallel between each other and the pins 82 and 83 are inserted, and appropriate tension is applied to the optical fibers 10 and 20, respectively.
2 at one end and the other end.

Next, the coating removed portions 12 and 22 are removed using a suitable jig.
As shown in FIG. 2, the coating removal portion l2 and 22 are symmetrically curved with an appropriate curvature in a direction toward each other to bring them into point contact, and the stretching table 80 is temporarily fixed at the point contact position. Next, as shown in FIG. 2, the contact points of the coated removed portions 12 and 22 are heated from both sides by gas burners 91 and 92 to fuse them.

Next, as shown in FIG.
The stretching table 80 is gently moved away from the stretching table 70 while the fused portions of the coated portions 12 and 22 are heated from both sides by gas burners 91 and 92, and the fused portions of the coating removed portions 12 and 22 are stretched in the axial direction. The coupling ratio of the optical coupler obtained as a single component changes depending on the amount of stretching of the fused portion of the optical fibers 10 and 20. The amount of emitted light at the other end is measured to determine the coupling ratio, and the stretching is terminated when the coupling ratio reaches the desired coupling ratio.

In this way, an optical coupler having a desired coupling ratio is obtained in which the claddings of the two optical fibers 10 and 20 are fused at the center of the coated removed portions 12 and 22, and the core diameter is smaller than the original diameter.

Then, as shown in FIG.
The length of the matching area between the holders 75 and 85 of the covered removed parts 12 and 22 is determined by the conventional method shown in FIG. It can be significantly shorter than the length of the parallel alignment region in the fusion stretching method using parallel alignment, and the length from one end of the coating removed portion 12.22 to the holder 75 and the length of the coating removed portion 1
2. Since the length from the other end of 22 to the holder 85 may be very small, the portion l of the coating removed before stretching is
The lengths of 2 and 22 can be significantly shortened compared to the conventional fusion drawing method using parallel alignment, and specifically, the lengths of 2 and 22 can be reduced to 10 m, which is about half that of the conventional fusion drawing method using parallel alignment. Even if the length of the optical coupler is added to this, the dimensions of the optical coupler obtained as a single component are approximately 20 m.
It can be made extremely small, within mm.

4 to 7 show each step in an example of the manufacturing method of the invention according to claim 2. The linear polarization maintaining optical fibers 30 and 40 in this case are
As shown in FIG. 8, cladding 33 and 43, respectively.
It has a pair of stress applying parts 3 5.3 6 and 4 5.4 6 at positions sandwiching the cores 34 and 44 inside,
The coating 31 of the linear polarization maintaining optical fibers 30 and 40
and 41 are removed over the required length, respectively.

First, as shown in FIG.
1 to 83 and a holder 75.85 are provided and placed over two stretching tables 70.80 arranged at a predetermined distance from each other, and the respective uncoated portions 32 and 42 are placed between the bins 71.72 and the bins 81.85. 82 questions and pins 72.73
and the bins 82 and 83, and place them in parallel, and apply appropriate tension to the linear polarization-maintaining optical fibers 30 and 40, respectively. However, at this time, the covering removal parts 32 and 42 are not yet held by the holders 75 and 85. Next, as shown in FIGS. 4 and 9, between the stretching table 70 and the stretching table 80, the coating removed portions 32 and 42 are
A glass plate 93 is applied to the lower side of the cladding 3 described above.
Matching oil 94 having a refractive index equal to 3 and 43 is dropped and filled between the removed portions 32 and 42, and parallel light 95 is irradiated from below, and the above-mentioned stress in the removed portions 32 and 42 is removed using a microscope 96 from above. While observing the application parts 35, 36 and 45, 46, the linear polarization maintaining optical fibers 30 and 40 are rotated around their respective axes with appropriate tension applied as described above. The principal axes of birefringence can be set to be parallel to each other as shown in Figure 9, on the same line as shown in Figure 10, or perpendicular to each other as shown in Figure 11. Set to relationship.

Next, as shown in FIG. 5, the glass plate 93 and matching oil 94 described above are removed, and the holder 7 is removed.
5 and 85 grip the stripped portions 32 and 42 at one and the other end, respectively.

The following is the same as an example of the manufacturing method of the invention of claim 1 described above, that is, first, a suitable jig is used to slightly guide the coating removed portions 32 and 42 so that they curve in a direction toward each other. , and the stretching table 80 is changed to the stretching table 7.
By bringing it closer to a predetermined distance from 0,
As shown in FIG. 6, the coating removed portions 32 and 42 are symmetrically curved with an appropriate curvature in a direction toward each other to bring them into point contact, and the stretching table 80 is temporarily fixed at the point contact position.

Next, as shown in FIG.
The contact points are heated from both sides by gas burners 91 and 92 to fuse them.

Next, as shown in FIG.
The stretching table 80 is gently moved away from the stretching table 70 while heating the fused portions of the two coated portions 32 and 42 from both sides by gas burners 91 and 92, and the fused portions of the coating removed portions 32 and 42 are stretched in the axial direction. At this time, the linear polarization maintaining optical fiber 3
The light enters from one end of the linear polarization maintaining optical fiber 30.
Then, the amount of emitted light at the other end of 40 is measured to determine the coupling ratio, and the stretching is terminated when the coupling ratio becomes the desired coupling ratio.

Thus, the two linear polarization maintaining optical fibers 30 and 4
0 is set in the desired relationship, the claddings of the linear polarization-maintaining optical fibers 30 and 40 are fused at the center of the coated removed portions 32 and 42, and the core diameter is smaller than the original diameter. An optical coupler with a coupling ratio of is obtained.

Then, just like the examples shown in Figures 1 to 3,
The lengths of the coating removal parts 32 and 42 can be significantly shortened, the dimensions of the optical coupler obtained as a single component can be significantly reduced, and the performance of the optical coupler obtained is improved, such as less light loss. is no different from the conventional fusion drawing method using parallel alignment.

"Effects of the Invention" As described above, according to the present invention, the coated portions of two optical fibers are curved with an appropriate curvature in a direction toward each other to bring them into point contact, and the contact points are heated and fused. Since the fused portion is heated and stretched, the dimensions of the optical coupler obtained as a single component can be made significantly smaller than those obtained by the conventional fusion-stretching method using parallel alignment. Various devices incorporating optical couplers, such as optical fiber gyros placed inside the fiber coil, can be significantly miniaturized, and the performance of the resulting optical couplers is completely superior to that achieved by the conventional fusion-stretching method using parallel alignment. does not change.

[Brief explanation of the drawing]

1 to 3 are top views showing each step in an example of the manufacturing method of the invention of claim 1, and FIGS. 4 to 7 are top views showing each step of an example of the manufacturing method of the invention of claim 2. Fig. 8 is a cross-sectional view showing an example of a linear polarization-maintaining optical fiber, and Figs. 9 to 11 show examples of setting the birefringence principal axis direction of two linear polarization-maintaining optical fibers. The cross-sectional view, Figure 12, is
It is a top view which shows the process in the conventional fusion drawing method by parallel alignment.

Claims (2)

[Claims] (1) Place the removed portions of two optical fibers in parallel with each other under appropriate tension, and then bend the removed portions of the two optical fibers with an appropriate curvature in a direction that brings them closer to each other. A method for manufacturing an optical coupler, comprising: bringing the contact points into point contact, then heating and fusing the contact points, and then stretching the fused portion in the axial direction while heating it. (2) The removed portions of two linear polarization-maintaining optical fibers, each having a stress-applying portion in the cladding, are arranged in parallel with their principal birefringence axes set and an appropriate tension applied to each. Next, the coated removed portions of the two linear polarization-maintaining optical fibers are curved with an appropriate curvature in a direction toward each other to bring them into point contact, and then the contact points are heated and fused. A method for manufacturing an optical coupler in which the fused portion is stretched in the axial direction while being heated.