JPS60257431A - Optical circuit device - Google Patents

Abstract

PURPOSE:To obtain an optical circuit device superior in S/N by providing optical output parts in places which do not include the position where the approximate normal direction of the first end face constituting an optical input part crosses the second end face. CONSTITUTION:In an optical circuit 22 constituted of an optical waveguide 21, an optical input part 24 is provided on the first end face 23, and optical output parts 26 are provided on the second end face, and optical output parts 26 are provided in places 25b which do not include a position 25a where the approximate normal (n) direction of the first end face 23a constituting the optical input part 24 and the second end face 25 cross to each other. A sufficient extinction ratio is obtained if a formula is satisfied where (l), 2wO, (w), and lambda are the length between the first end face 23 and the second end face 25, the width of an optical waveguide 21a of the optical input part, the length between said position 25a and the optical output part 26, and the wavelength of the guided light respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to optical transmission systems. In particular, the present invention relates to an optical circuit device for an optical transmission system configured by end-face coupling.

Conventional configurations and their problems In conventional optical circuit devices, optical coupling by end-face excitation is used because it has high coupling efficiency and is easy to configure. However, when actually constructing an optical circuit device called a total reflection type optical switch as shown in FIG. 1, a problem arose. That is, in the optical circuit 12 constituted by the optical waveguide 11,
The light 21 transmitted through the optical fiber 13 is guided by end face coupling with the optical waveguide 11a with a coupling efficiency η. Optical waveguide 1
The light a1 of 1a is guided through the optical waveguide 11c due to the electro-optic effect due to the electric field generated by the electrode 14, and is guided through the optical fiber 15.
The light is transmitted as light p,2. On the other hand, if no voltage is applied to the electrode 14, the light λ1 travels straight, is guided through the optical waveguide 11b, and is transmitted to the optical fiber 16.

The above operation functions as an optical switch.

Here, since the optical coupling efficiency η of the transmitted light at the optical input section is not 1, it propagates to areas other than the optical waveguide 11a, and light 21' is generated. The light h' is transmitted through the optical fiber 16 at the optical output section.
The problem is that the signal is transmitted to the signal line, reducing the signal S/N ratio.

OBJECTS OF THE INVENTION An object of the present invention is to improve the problem of a decrease in the S/N ratio caused by conventional optical coupling by adding innovations to the optical waveguide configuration, and to provide an optical circuit device with an excellent S/N ratio. The purpose is to

Composition of the Invention The optical circuit device according to the present invention is an optical circuit constituted by an optical waveguide, which has an optical input section at a first terminal and an optical output section at a second terminal, and constitutes the optical input section. The light output portion is provided in a portion that does not include a portion where the second end surface intersects with the substantially normal direction of the first end surface.

In particular, the distance 2 between the first end surface and the second end surface, the width 2wo of the optical waveguide of the optical input section, the intersection of the normal line of the optical input section and the second end surface, and the optical output section. It is preferable to have a structure that satisfies the relationship between the interval W and the wavelength λ of the guided light.

DESCRIPTION OF EMBODIMENTS The structure of the present invention will be explained based on the following embodiments. Second
The figure is a plan view of essential parts of the optical F1'' path device according to the present invention. That is, in the optical circuit 22 constituted by the optical waveguide 21, the optical input section 24 is connected to the first input section 23, and the optical input section 24 is connected to the second input section 23.
The end face 25 has a light output part 26, and the first end 23a, which constitutes the light input part 24, has a substantially normal n direction and the second end face 26.
The configuration is such that the light output section 26 is provided at a portion 25bK that does not include the portion 25a that intersects with the portion 25a.

A concrete example of a total reflection type optical switch with the above configuration is shown in FIG.

Optical waveguide 'IV' with a depth of 4ym! 621 with Ti diffusion L I
Light with a wavelength of 0.81 μm was optically coupled at the optical input section 24 using an optical fiber made of N'b O3 and having a core of 6 μm. In this case, the optical coupling efficiency was 70%. In this case, the intersection angle 0 of the optical switch is set to 20. In this case, the optical switch is operated by applying the voltage of the electrode 27, and the operating voltage is 5Q
The notching operation was performed and the signal was transmitted to the waveguide 21b.If no voltage was applied to the collar electrode 27, the signal was transmitted to the waveguide 21[. However, in the configuration shown in FIG. 1, when light is output through prism coupling, the extinction ratio (voltage O
The ratio of the light intensity at FF and ○N is 2 odB, but when optically coupled to the optical fiber 16 by end-coupling, it becomes 1
Low level 1 to 0dB.

However, according to the present invention, when the distance W between the normal line n and the optical waveguide 2IC is reduced by 1', the extinction ratio becomes 19 dB, which is comparable to prism coupling.

However, if the radius of curvature of the curved portion of the optical waveguide is made small in order to widen the interval W between the two 51, the optical propagation loss of the wire connected to the optical output section 26 will increase, so the radius of curvature of the curved portion should be It has to be large. For this reason,
Optical circuit devices were getting bigger and bigger.

As a result of detailed study to improve this point, the present inventor found that the extinction ratio can be sufficiently changed if the following relationship is met, and has invented a new optical circuit device. This will be explained using FIG. 2 as in the first embodiment.

That is, the distance l between the first end 23 and the second end 25, the width 2W0 of the optical waveguide 21a of the optical input section, the intersection 25a of the normal n of the optical input section and the second end surface 25, and the optical It was favorable if the following relationship was satisfied between the distance W to the output section 26 and the wavelength λ of the guided light. For example, with the same configuration as the first embodiment, l = 5 ms, wO = = 3 pm
, λ-0,81 μm, w) If it is 340 μm, then “2”.

In the case of W) 400 pm, the present inventors found that the extinction ratio of 20 dB with prism coupling is 17 dB when the optical fiber is output with a 6 μm core, and W = 1.
The same characteristics as in the case of y are obtained /ζ. In this case, in the first example, l==1Qm, but in this example, it was only l=5xm, and the extinction ratio was also about the same. Compared to the conventional example, the extinction ratio was improved to the same extent.

''Moon's theory [jl, lte←1, Ti-diffused LiNb○3 An example of an optical waveguide; , glass optical waveguide.

PLZT light barrel waveguides may also be used, all of which are included in the present invention.

Effects of the invention As is clear from the above explanation, the light switch alone! 1
, even if the characteristics are sufficient, it cannot be configured as a component of an optical transmission system.
/The problem of a decrease in S/N ratio that occurred in this case was improved by devising the configuration of the guiding waveguide, and it has a great effect on the industrial field for optical transmission systems. and is very useful.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a conventional optical circuit device, and FIG. 2 is a plan view of essential parts showing the configuration of an optical circuit device according to an embodiment of the present invention. 21. Optical waveguide, 22... optical circuit, 23...
- First end surface, 24... light input section, 25... second end surface, 26... light output section, 27... electrode.

Claims (2)

[Claims] (1) In an optical circuit configured as an optical waveguide, the first end has an optical input section, the second end has an optical output section, and the first end constituting the optical input section has approximately An optical circuit device characterized in that a light output section is provided in a region that does not include a region where a normal direction and a second end surface intersect. (2) - The distance β between the first end surface and the second end surface, the width 2Wo of the optical waveguide of the upper light distribution section, and the ? of the optical input section? J
E Ia'1. and the second end, the distance W between the intersecting portion of the light output portion and the wavelength λ of the guided light satisfies the following relationship: Optical circuit device.