JPS6363007A - Waveguide type branching circuit - Google Patents

Abstract

PURPOSE:To reduce a branch loss, and also, to arbitrarily set a branching ratio by forming an area whose refractive index is different partially, in a branch connection, and adjusting its position, shape and refractive index difference., CONSTITUTION:Y-shaped optical waveguide 11, 11' and 11'' are formed on a substrate 10 by a diffusion method or an ion exchange method, and in this case, a trapezoidal area 12 whose refractive index is different is formed in a branch connection. In this case, when a refractive index of a substrate, a refractive index of a waveguide, and a refractive index of a trapezoidal part are denoted as n1, n2 and n3, respectively, n1<n3<n2 is set. In this way, since the area 12 whose refractive index is different is trapezoidal, out-of-focus by a process does not occur, and also, since the refractive index is varied gradually extending from (a) to (b), an optical loss in the branch connection is reduced, and also, by moving a little the tip part of the trapezoid in the direction as indicated with an arrow (y), a branching ratio of an emitted light can be set arbitrarily.

Description

[Detailed Description of the Invention] [Summary] A waveguide type branch circuit in which a region with a partially different refractive index is formed in the Y-shaped branch, and the position, shape, and refractive index difference of this region is adjusted. By doing so, it became possible to branch waveguide to an arbitrary branching ratio.

[Industrial application field]

The present invention relates to a waveguide type branch circuit used in optical communications.

Waveguide type branch circuits are used for optical branching of LANs (Local Area Networks) and the like, but there is a demand for low loss.

[Conventional technology]

As shown in Fig. 3a, the waveguide type branch circuit has waveguides 2°2', 2'' on a substrate 1 made of electro-optic crystal such as LiNbO3.
The waveguide is formed by diffusing Ti or ion exchange to make the refractive index of that part larger than that of the substrate, and the waveguides 2.2' and 2'' form a figure 7 shape. Six single modes of light from the waveguide 2 can be branched into 6 waveguides 2' and 2''.

[Problem that the invention sought to solve]

In the conventional waveguide type branch circuit described above, in order to reduce the loss at the Y branch, the branch angle is small (for example, 0.2 degrees).
However, if the branching angle is made small, in the conventional manufacturing process, the wedge-shaped part 3 of the branching part becomes blurred, as shown in Figure 3, and the shape is not ideal.
A loss will occur here. Furthermore, there is a problem in that the branching ratio cannot be freely set.

The present invention was created in view of these points, and an object of the present invention is to provide a waveguide type branch circuit that can reduce branching loss and set the branching ratio arbitrarily.

[Means for solving problems]

Therefore, in the present invention, one single mode optical waveguide 11 is replaced by two single mode optical waveguides 11' and 11.
In a Y-shaped branch path that branches into a branch, a region 12 with a partially different refractive index is formed at the branch part, and by adjusting the position, shape, and difference in refractive index, the branching and wave-guiding can be achieved at an arbitrary branching ratio. It is characterized by

[For production]

By providing regions with partially different refractive indexes in the branching portion, it is possible to prevent loss due to blurring of the conventional wedge-shaped portion, and by adjusting the positions of the regions with different refractive indexes, it is possible to achieve an arbitrary branching ratio. What you did becomes possible.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention.

In this embodiment, as shown in the figure, a 7-shaped optical waveguide ILII' is formed on a substrate 10 by a diffusion method or an ion exchange method.

11'' is the same as in the conventional case, and the main point of this embodiment is that a trapezoidal region 12 with different refractive index is formed at the branching part (the tip of the triangular part formed at the part where the leading waveguides 11' and 11" join). was formed. In this case, the refractive index of the substrate is nl, the refractive index of the waveguide is nz, and the refractive index of the trapezoidal part is n3.
Then, n, <il, <fi.

In this embodiment configured as described above, since the region 12 with different refractive index is trapezoidal, there is no blurring caused by the manufacturing process as in the conventional case, and since the refractive index gradually changes from a to b, there is no blurring at the branching part. The light placed on the fire will be reduced. Further, by slightly moving the tip of the trapezoid in the direction of the arrow y, the branching ratio of the emitted light can be arbitrarily set. FIG. 2 is a diagram showing the relationship between the amount of movement of the tip of the trapezoidal part and the branching ratio.

In addition, this embodiment has a strong wavelength dependence, whereas a conventional branch circuit similar to a directional coupler in which two waveguides are formed close to each other or a branch circuit in which two waveguides are crossed can have a strong wavelength dependence. Since the light branching is geometric, there is also the advantage that wavelength dependence is small.

〔Effect of the invention〕

As described above, according to the present invention, the branching ratio can be arbitrarily set with low loss using an extremely simple configuration, and is extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the relationship between the amount of movement of trapezoidal regions with different refractive indexes and the branching ratio in the embodiment of the present invention, and Fig. 3 is a diagram showing a conventional waveguide. FIG. 3 is a diagram showing a type branch circuit. In FIG. 1, 10 is a substrate, 11, 11', and 11' are optical waveguides, and 12 is a trapezoidal region having different refractive indexes.

Claims (1)

[Claims] 1. Y where one single mode optical waveguide (11) branches into two single mode optical waveguides (11', 11'')
In the type branching path, a region (12) with a partially different refractive index is formed at the branching part, and by adjusting the position, shape, and refractive index difference, it is possible to branch and guide the wave to an arbitrary branching ratio. Waveguide type branch circuit. 2. The waveguide type branch circuit according to claim 1, wherein the branch circuit is produced by means such as ion exchange or diffusion.