JP2574555Y2 - Connection structure between optical waveguide and optical fiber - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure between an optical waveguide and an optical fiber, which can connect an optical waveguide used for branching / merging, multiplexing / demultiplexing, and switching light in optical communication to an optical fiber with low loss. is there.

[0002]

2. Description of the Related Art Conventionally, to connect an optical fiber to an input / output portion of an optical waveguide, a Butt-type optical fiber is directly fixed at its lowest loss position by directly abutting both end faces. The Joint method is used. This method is simple because it is a method of positioning by simple butting, but has the following disadvantages.

The cross-sectional shape of a core of an optical fiber is usually circular, and the cross-sectional shape of a core of an optical waveguide is rectangular. Therefore, when both are connected, a connection loss occurs because the shapes of both do not match at the connection portion.

Since the cross-sectional shapes of both cores do not match, and the cross-sectional size of both cores is on the order of microns, when connecting both cores while directly measuring the power of light, the optimum connection position of both cores Even if it deviates slightly from the above, the intensity of the light power at this time is not so different from the intensity at the peak value. That is, the peak value is not clear, which makes it difficult to accurately align the light power with the peak.

The above problem does not occur if the shapes of both cores are matched, but it is difficult to make the core of the optical waveguide circular.

[0006] For the above reasons, the loss at the connection between the optical fiber and the optical waveguide becomes large, and it is difficult to use a large number of optical waveguides connected in series by the optical fiber due to the increase in the loss.

The present invention has been made in view of the above points, and provides a low-loss connection structure between an optical waveguide and an optical fiber.

[0008]

In order to solve the above-mentioned problems, the present invention provides a core 21 of an optical waveguide 20 having a different sectional shape.
Waveguide 20 connecting the core 11 of the optical fiber 10 to the optical waveguide 20
And in the connection structure of the optical fiber 10, the light phi
The bar 10 is tensioned at both ends and pulled.
The outer periphery of the clad 13 is heated and pressed for a predetermined distance.
And the sectional shape of the core 11 inside the optical fiber 10
The shape is almost the same as the cross-sectional shape of the core 20 of the optical waveguide 20
With the same shape as the end face of the optical fiber 10
Deformed part 1 formed over a predetermined distance from
5 were provided.

[0009]

As described above, since the cross-sectional shape of the core 21 of the optical waveguide 20 and the cross-sectional shape of the core 11 of the optical fiber 10 are made substantially equal to each other, the two are connected. For this reason, low-loss connection is possible.

Particularly, in the present invention, since the cross-sectional shape of the core 11 of the optical fiber 10 is formed so as to match the optical waveguide core 21 over a predetermined distance from the end face, the core 11 is introduced into the deformed core 11 in the optical fiber 10. In particular, in the case of a single mode fiber, the reflected light is introduced into the optical waveguide core 21 after the wave thereof almost completely matches the mode field diameter of the optical waveguide core and becomes stable. Can be performed efficiently.

Since the cross-sectional shapes of the cores 11 and 21 are substantially the same, the core 11 of the optical fiber 10 and the optical waveguide 2
When the connection position of the 0 core 21 deviates from the optimum position (ie, the peak position of the light power), the difference between the light power at that time and the light power at the peak position is clearly obtained.
For this reason, alignment of both becomes easy.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing a connection portion between an optical waveguide and an optical fiber according to the present embodiment. As shown in the drawing, in the present invention, a fiber deforming portion 15 is provided at the end of the optical fiber 10 and the fiber deforming portion 15 is provided.
The configuration is such that the cross-sectional shape of the core 11 is made to match the cross-sectional shape of the core 21 of the optical waveguide 20 and the matched cores 11 and 21 are connected to each other. Hereinafter, each component will be described in detail.

As shown in FIG. 1, the optical waveguide 20 includes a clad layer 23 provided on a substrate 25 with a buffer layer 27 interposed therebetween, and a core 21 provided at a predetermined position.
The cross-sectional shape of the core 21 is square.

2A and 2B are views showing the vicinity of the end of the optical fiber 10, wherein FIG. 2A is a side view, FIG. 2B is a sectional view taken along line AA of FIG. FIG. 3C is a cross-sectional view taken along the line BB of FIG. As shown in FIG. 1, the optical fiber 10 is configured by providing an optical fiber deforming portion 15 at an end of a normal optical fiber. That is, a normal optical fiber portion is configured by providing a circular core 11 inside a circular clad 13 as shown in FIG. 2B, and an optical fiber deformed portion 15 is shown in FIG. As described above, both the core 11 and the clad 13 are formed in a square shape, that is, so as to substantially match the shape of the core 21 of the optical waveguide 20 shown in FIG. Although the single mode optical fiber is used as the optical fiber 10, another mode such as a multi mode may be used.

FIG. 3 is a view showing a method of providing the optical fiber 10 with the fiber deforming section 15. As shown in FIG. First, as shown in FIG. 1A, a holding angle 30 which is bent at a right angle and provided with a heating part h near the corner is prepared, and the optical fiber 10 is installed at the corner. Then, the optical fiber 10 is heated to about 1200 to 1500 ° C. by the heating by the heating unit h and softened. A flame, electric means, or the like is used as a heating source.

Next, as shown in FIGS. 2B and 2C, the softened optical fiber 10 is pressed by the right forming plate 31 and the upper forming plate 33, and the outer periphery of the optical fiber 10 is formed into a square shape. . As a result, the core 11 and the cladding 13 are formed in a substantially square shape as shown in FIG. At this time, in order to prevent an increase in loss due to microbending, it is preferable to pull both sides of the optical fiber 10 to be molded with a slight tension. FIG. 1D is a side view showing the optical fiber 10 formed as described above.

Then, the optical fiber 10 molded as described above is cut at the center as shown in FIG. 1E, whereby two optical fibers 10 used in the present invention are completed.

Next, the connection of the optical fiber 10 to the optical waveguide 20 uses the Butt-Joint method. That is, as shown in FIG. 1, the end face of the optical fiber 10 is
Is directly connected to the end face of the core 21 at the position of the maximum efficiency. At this time, the cross-sectional shape of the core 11 of the optical fiber 10 and the core 21 of the optical waveguide 20 at this connection portion
Have almost the same cross-sectional shape, so that the connection loss is small. Also, in this case, since the shapes of the cores 11 and 21 are almost the same, a slight difference in the optical power is obtained even if the cores 11 and 21 are slightly deviated from the optimum connection position. Become. The optical fiber 10 and the optical waveguide 20 are connected and fixed using an adhesive, heat fusion by electric discharge, or the like.

In the present invention, the optical fiber 10
The cross-sectional shape of the core 11 was formed over a predetermined distance from its end face (that is, by the length of the optical fiber deformed portion 15) so as to match the cross-sectional shape of the core 21 of the optical waveguide 20. For this reason, the light introduced from the portion of the core 11 having the circular cross section to the portion of the core 11 deformed into the square cross section is
After the wave is in a stable state, it is introduced into the core 21 of the optical waveguide 20, so that the two can be connected efficiently. That is, the light immediately after being introduced from the circular cross-section to the square cross-section of the core 11, especially in the case of a single-mode fiber, has a different mode field diameter, so that the wave is not stable. For this reason, if the portion of the core 11 deformed into a square cross section is not provided with a predetermined length, and this is connected to the core 21 of the optical waveguide 20 immediately after the deformation, the radiation does not match the mode field diameter of the optical waveguide core and is radiated. The loss of light at the connection part increases.

FIG. 4 is a perspective view showing an example of a support structure for the optical fiber 10. As shown in FIG. As shown in the figure, the optical fiber deformed portion 15 at the end of the optical fiber 10 is supported by a support member 60. Here, since the outer periphery of the optical fiber deformed portion 15 is formed in a square shape over a predetermined length, one center of the upper surface of the support member 60 is formed.
Only by providing the rectangular groove 61, the end of the optical fiber 10 can be easily supported. Then, this state is directly joined to the end face of the optical waveguide 20 to perform alignment,
Fix both. The use of such a support member 60 makes it easier and more reliable to connect and fix the two than in the case where only the optical fiber 10 is directly connected to the optical waveguide 20.

FIG. 5 is a sectional view of an optical fiber deformed portion according to another embodiment of the present invention. As shown in FIG. 3A, the cross section of the core 11 'of the optical fiber 10' may be formed in a rectangular shape, and as shown in FIG. 3B, the cross section of the core 11 "of the optical fiber 10" is formed. It may be formed in a semicircular shape. The point is that if the shape matches the shape of the core of the optical waveguide to which these optical fibers 10 'and 10 "are connected,
It may be formed into any shape. When the core shape is formed in a semicircular shape, an arc shape is used for the holding angle 30 or the forming plates 31, 33 shown in FIG.

It is desirable that the refractive indices of the core of the optical fiber and the core of the optical waveguide be substantially the same.

[0023]

As described in detail above, according to the connection structure between an optical waveguide and an optical fiber according to the present invention, the following excellent effects are obtained.

Since the cross-sectional shape of the core of the optical waveguide and the cross-sectional shape of the core of the optical fiber are substantially equal, and there is no mismatch in shape, low-loss connection is possible.

In particular, in the present invention, since the cross-sectional shape of the core of the optical fiber is formed so as to match the cross-sectional shape of the core of the optical waveguide over a predetermined distance from the end face,
The light introduced into the portion of the core deformed in the optical fiber is introduced into the core of the optical waveguide after the wave is stabilized, and the two can be connected efficiently.

Since the cross-sectional shapes of the core of the optical fiber and the core of the optical waveguide substantially coincide with each other, if the connection position between the two cores deviates from the optimal position (ie, the peak position of the light power), the light power at that time and Since the difference from the light power at the peak position clearly appears, the alignment of the two becomes easy.

The optical fiber and the optical waveguide are made of a normal Butt.
Since the connection can be fixed by the t-Joint method, the connection operation is easy.

The present invention can be applied to any optical waveguide core having a cross-sectional shape, and is versatile.

Since the connection between the optical fiber and the optical waveguide can be performed with low loss, a large number of optical waveguides can be connected in series by the optical fiber.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a connection portion between an optical waveguide and an optical fiber according to an embodiment of the present invention.

FIG. 2 is a diagram showing the vicinity of an end of the optical fiber 10,
FIG. 1A is a side view, and FIG. 1B is AA of FIG.
FIG. 2C is a sectional view taken along line BB of FIG. 2A.

FIG. 3 is a diagram illustrating a method of forming a fiber deformed portion 15 in the optical fiber 10.

FIG. 4 is a perspective view showing an example of a support structure of the optical fiber 10.

FIG. 5 is a sectional view of an optical fiber deformed portion according to another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 optical fiber 11 core 13 clad 20 optical waveguide 21 core

Claims (1)

(57) [Scope of request for utility model registration] In a connection structure of an optical waveguide and an optical fiber for connecting a core of the optical waveguide and a core of the optical fiber having different cross sections, the optical fiber is pulled by applying tension to both ends.
The outer circumference of the clad is heated and pressed
By changing the cross-sectional shape of the core inside the optical fiber
The part that has almost the same cross-sectional shape as the core of the optical waveguide
A certain distance from the end face of the optical fiber with the same shape
A connection structure between an optical waveguide and an optical fiber, wherein a fiber deformed portion formed by the above method is provided .