JPH0618730A - Branching/multiplexing optical waveguide circuit - Google Patents

Abstract

PURPOSE:To obtain the branching/multiplexing optical waveguide circuit in which a dimension deviation for manufacture is scarcely generated, and a branch loss is scarcely generated. CONSTITUTION:This circuit is provided with a wedge structure member 12 which has width being below width W21 of an input waveguide 11, is inserted into branch parts 11a, 11b, allows the input waveguide 11 to branch, and whose tip is flattened, tapered waveguides 13, 14 which are connected to a branch waveguide which becomes thinner than the width W21 of the input waveguide 11 by the wedge structure member 12, and widened to width of the input waveguide 11, and circular arc-like waveguides 15, 16 which are connected to the tapered waveguides 13, 14 and have a prescribed curvature R.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention divides a waveguide in a clad on a substrate to form a plurality of branch waveguides.
The present invention relates to a combined optical waveguide circuit.

[0002]

2. Description of the Related Art Optical fiber communication requires various optical parts in addition to an optical fiber, a light receiving element, a light emitting element and the like. There is a branching / multiplexing optical waveguide circuit in the optical parts. It is a circuit that splits or multiplexes light by branching the waveguide (core) in the clad on the substrate to form multiple branching waveguides. is there.

FIG. 4 is an explanatory diagram for explaining the concept of a conventional branching / multiplexing optical waveguide circuit. Note that the clad and the substrate are omitted for simplification of description.

In the figure, the waveguide of the branching / multiplexing optical waveguide circuit is a tapered waveguide (core widths W ₁₁ and W ₁₂ , where W
₁₂ = 2 × W ₁₁ ) The input waveguide 2 having the core width W ₁₁ is connected to one end (the narrower one) of 1 and the core width W is connected to the other end (the wider one).
It is formed by connecting arcuate branch waveguides 3 and 4 having the same core width W ₁₃ as ₁₁ and having a predetermined radius of curvature R.

When light is input from the input waveguide 1 of this branching / multiplexing optical waveguide circuit waveguide, it is branched into branching waveguides 3 and 4.
It is supposed to be output from. In addition, the branch waveguide 3,
When light is simultaneously input from the optical waveguides 4, the light is multiplexed and output from the input waveguide 1.

[0006]

However, in the conventional branching / multiplexing optical waveguide circuit described above, the width of the wedge-shaped tip formed by the branching waveguide at the time of manufacture is not zero but is branched. The loss will increase. In addition, there is a problem that the branching waveguide near the branching point is likely to be asymmetrical and the branching ratio is unbalanced.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a branching / multiplexing optical waveguide circuit having a small manufacturing dimensional error and a small branching loss.

[0008]

In order to achieve the above object, the present invention provides a branching / multiplexing optical waveguide circuit for branching an input waveguide in a clad on a substrate to form a plurality of branching waveguides. A wedge structure member having a width equal to or less than the width of the waveguide, which is inserted into the input waveguide and branches the input waveguide to form a branch waveguide, and a wedge structure member having a flat tip, A tapered waveguide that is connected to the branched portion of each narrowed input waveguide and expands to the width of the input waveguide,
And an arcuate waveguide connected to the tapered waveguide and having a predetermined curvature.

[0009]

According to the above structure, the input waveguide is branched by the wedge-shaped structure, and the flat portion is provided at the tip of the wedge structure member, which eliminates the microfabrication of the waveguide in manufacturing and reduces the dimensional error. Since the wave front of the incident light entering from the waveguide is inclined in the branching direction by the wedge structure member, branching loss is suppressed.

[0010]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an explanatory view for explaining the concept of one embodiment of the branching / multiplexing optical waveguide circuit of the present invention, in which the tip of the wedge structure member is flat and has a width shorter than the width of the wedge structure member. The case where the part is formed will be described. Note that the clad and the substrate are omitted for simplicity of explanation (the substrate is made of quartz).

In the figure, the waveguide of the branching / multiplexing optical waveguide circuit has a width W ₂₂ less than the width W ₂₁ of the input waveguide 11.
The wedge structure member 12 that is inserted into the input waveguide 11 and branches the input waveguide 11 and the width of the input waveguide 11 that is connected to the branch portions 11a and 11b that are narrower than the width of the input waveguide 11 by the wedge structure member 12 The input waveguide 11 is provided with tapered waveguides 13 and 14 extending to W ₂₁ and arcuate waveguides 15 and 16 connected to the tapered waveguides 13 and 14 and having two predetermined curvatures R. Branch part 11a of
11b and the tapered waveguides 13 and 14 and the arcuate waveguides 15 and 16 form a branch waveguide.

The wedge structure member 12 has W _{22 at} its tip.
Flat portion 1 having the following width W ₂₃ (hereinafter referred to as “blunt width”)
2a is formed. Branching portion 11 of input waveguide 11
Although a and 11b are thinned by the wedge structure member 12, they are widened to the same width W ₂₁ of the input waveguide 11 by the tapered waveguides 13 and 14. The tapered waveguides 13 and 14 have an inner divergence angle θ and an outer divergence angle 2θ.
have.

The waveguides expanded by the tapered waveguides 13 and 14 are smoothly connected to the substantially S-shaped arcuate waveguides 15 and 16 having two predetermined curvature radii R.

In such a branching / multiplexing optical waveguide circuit, when light is input to the input waveguide 11, it is branched and split into branching portions 11a,
11b, tapered waveguides 13 and 14 and arcuate waveguide 1
It is adapted to be output from a branch waveguide composed of 5 and 16. On the contrary, when light is input from the branch waveguide, it is combined and output from the input waveguide 11.

Next, the operation of the embodiment will be described.

By branching the input waveguide 11 with a wedge-shaped structure and providing the flat portion 12a at the tip of the wedge structure member 12, fine fabrication of the waveguide in manufacturing is eliminated and dimensional error is reduced. At the same time, the wave front of the incident light entering from the input waveguide 11 is inclined in the branching direction by the wedge structure member 12, so that branching loss is suppressed. Therefore, the light input to the input waveguide 11 of such a branching / multiplexing optical waveguide circuit is output from the branching waveguide with an accurate branching ratio.

FIG. 2 is a diagram showing the relationship between the wedge width W ₂₂ and the branch loss of the branching / multiplexing optical waveguide circuit shown in FIG.
The horizontal axis shows the wedge width W ₂₂ , and the vertical axis shows the branch loss. The width and height of the waveguide are about 8 μm.

From the figure, when the wedge width W ₂₂ is zero, that is, when the wedge structural member 12 is not present, the branch loss is about 0.08.
In contrast to dB, the wedge width W ₂₂ is reduced to about 0.06 dB by forming a wedge-shaped structure with a wedge width of about 5 μm, and the branch loss is reduced.

FIG. 3 shows a rounded width W ₂₃ when the wedge width W ₂₂ of the branching / multiplexing optical waveguide circuit shown in FIG. 1 is set to about 5 μm.
FIG. 5 is a diagram showing the relationship between the branch loss and
₂₃ , the vertical axis shows branch loss.

From the figure, when the round width W ₂₃ is zero, that is, when the tip is sharp, the branch loss is about 0.06 dB, while when the round width W ₂₃ is about 2 μm, it is about 0.0.
It is reduced to 35 dB, and it can be seen that the branch loss is smaller than when the round width W ₂₃ is zero.

As described above, according to this embodiment, the width of the input waveguide 11 is equal to or less than the width W ₂₁ , and the branch portions 11a and 11b.
Wedge structure member 1 inserted in the branch to branch the input waveguide 11
2 and the width W of the input waveguide 11 due to the wedge structure member 12
Input waveguide 1 connected to a branch waveguide that is thinner than ₂₁
Since the tapered waveguides 13 and 14 that expand to a width of 1 and the arcuate waveguides 15 and 16 that are connected to the tapered waveguides 13 and 14 and have a predetermined curvature R are provided, the dimensional error in manufacturing is small. A branching / multiplexing optical waveguide circuit with less branching loss can be realized.

In this embodiment, the wedge width is provided at the tip of the wedge structure member, but the width is not limited to this.
A wedge structural member having no rounded width may be used.

[0024]

In summary, according to the present invention, the following excellent effects are exhibited.

(1) It is possible to reduce manufacturing dimensional errors.

(2) Branch loss can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining the concept of an embodiment of a branching / multiplexing optical waveguide circuit of the present invention.

2 is a diagram showing a relationship between a wedge width and a branch loss of the branching / multiplexing optical waveguide circuit shown in FIG.

3 is a diagram showing a relationship between a rounded width and a branch loss when the wedge width of the branching / multiplexing optical waveguide circuit shown in FIG. 1 is set to about 5 μm.

FIG. 4 is an explanatory diagram for explaining the concept of a conventional branching / multiplexing optical waveguide circuit.

[Explanation of symbols]

 11 Input Waveguides 11a, 11b Branching Part 12 Wedge Structural Member 12a Flat Part 13, 14 Tapered Waveguide 15, 16 Arc Waveguide

Claims (3)

[Claims] 1. A branching / multiplexing optical waveguide circuit for branching an input waveguide in a clad on a substrate to form a plurality of branching waveguides, wherein the input waveguide has a width equal to or smaller than a width of the waveguide. A wedge structure member that is inserted into a waveguide and branches the input waveguide to form a branched waveguide, and a wedge structure member having a flat tip, and a branch portion of each input waveguide that is narrower than the width of the input waveguide by the wedge structure member. Branching / multiplexing optical waveguide, comprising: a tapered waveguide that is connected to the input waveguide and widens to the width of the input waveguide; and an arc waveguide that is connected to the tapered waveguide and has a predetermined curvature. circuit. 2. The branching / multiplexing optical waveguide circuit according to claim 1, wherein a flat portion having a width shorter than the width of the wedge structure member is formed at a tip of the wedge structure member. 3. The branching / multiplexing optical waveguide circuit according to claim 1, wherein the substrate is made of quartz.