JP2726491B2 - Optical matrix switch - Google Patents

Description

The present invention relates to an optical matrix switch using an optical waveguide having a gate function.

(Prior Art) FIG. 2 shows an example of a conventional optical matrix switch of this type, for example, a 2 × 2 optical matrix switch, in which 1, 2, 3, 4, 5, 6, 7 are optical waveguide switches. Wave paths, 8, 9, 10, and 11 are grooves.

The optical waveguides 1 to 4 constitute an input end or an output end. The optical waveguide 1 is connected to the optical waveguide 2 via the optical waveguide 5 and to the optical waveguide 4 via the optical waveguide 7. Further, the optical waveguide 3 is connected to the optical waveguide 4 via the optical waveguide 6 and to the optical waveguide 2 via the optical waveguide 7. The optical waveguides 5 to 7 are optical waveguides having a gate function, for example, semiconductor optical waveguides having a PN junction. The structure and operating principle of this semiconductor optical waveguide having a PN junction are described in “Laser diode swi
tch ”(Electron Lett, vol. 17, No. 23, P899-900, 1981)
However, when a forward current is injected, the active layer becomes a gain waveguide similarly to a semiconductor laser. The grooves 8 to 11 constitute means for branching or joining optical signals. The groove 8 is provided at a connection portion of the optical waveguides 5 and 7 on the optical waveguide 1 side, and the groove 9 is provided at the optical waveguide 5 and 7. It is provided at the connection portion on the side of the wave path 2. The groove 10 is provided at a connection portion of the optical waveguides 6 and 7 on the optical waveguide 3 side, and the groove 11 is provided at a connection portion of the optical waveguides 6 and 7 on the optical waveguide 4 side.

In the above configuration, if a forward current is injected into the optical waveguides 5 and 6 and not injected into the optical waveguide 7, the optical waveguides 5 and 6 become gain waveguides, but the optical waveguide 7 becomes an absorption waveguide.
Therefore, for example, when signal light having a wavelength within the gain width is input from the optical waveguide 1, the signal light is branched into the optical waveguide 5 by the groove 8, amplified, and further emitted to the optical waveguide 2 through the groove 9. You. Similarly, the signal light incident from the optical waveguide 3 is also transmitted through the groove 10, the optical waveguide 6, and the groove 11 to the optical waveguide 4.
Emitted to

On the other hand, when a forward current is injected into the optical waveguide 7, the optical waveguide 7 becomes a gain waveguide, and the signal light incident from the optical waveguide 1 is branched into the optical waveguide 7 by the groove 8, amplified, and transmitted through the groove 11. The light is emitted to the wave path 4. Similarly, light incident from the optical waveguide 3 is also emitted to the optical waveguide 2 through the groove 10, the optical waveguide 7, and the groove 9.

(Problems to be Solved by the Invention) In the above-described optical matrix switch, the light is branched or merged by the action of the half mirrors of the grooves 8 to 11, so that the branch ratio in the grooves 8 to 11 is close to 1: 1. And low loss were required. The branching ratio in the grooves 8 to 11 is determined by the depth of the grooves, but in order to reduce the loss, the grooves have to be narrow and have good side smoothness and verticality.

Conventionally, for example, when digging a groove in an optical waveguide composed of an InP system, an ion beam etching method using Br ₂ has been adopted for Cl ₂ , but a groove having a narrow groove width and good side surface smoothness and verticality is desired. It was extremely difficult to dig to a depth.

In the optical matrix switch, an optical path length from the optical waveguide 1 to the optical waveguide 2 and an optical path length from the optical waveguide 1 to the optical waveguide 4 (or an optical path length from the optical waveguide 3 to the optical waveguide 4 and an optical path length from the optical waveguide 3 to the optical waveguide). 2).
There is a problem that the insertion loss and the isolation (difference in light intensity between the ON signal and the OFF signal) vary depending on the setting of the optical path.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical matrix switch which eliminates the above-mentioned problems, is easy to manufacture, and has little variation in insertion loss and isolation due to a set optical path.

(Means for Solving the Problems) In the present invention, in order to achieve the above object, in an optical matrix switch using an optical waveguide having a gate function,
An optical matrix switch is proposed in which the optical signal branching or merging means is configured by using a total reflection groove, and the optical waveguides are arranged such that the lengths of the optical paths that branch and merge are equal.

(Operation) According to the present invention, light incident from one end of the optical waveguide is branched at the total reflection groove, and emitted through the optical waveguide having a gate function and another total reflection groove.

(Embodiment) FIG. 1 shows an embodiment of an optical matrix switch according to the present invention, in which the same components as those of the conventional example are denoted by the same reference numerals. That is, 1,2,3,4,12,13,14 are optical waveguides, 1
5, 16, 17, 18, 19, and 20 are total reflection grooves.

The optical waveguides 12 to 14 are optical waveguides having a gate function, for example, semiconductor optical waveguides having a PN junction similar to the conventional example. The optical waveguide 12 has a shape that is bent at substantially a right angle, and connects the optical waveguides 1 and 2. The optical waveguide 13 has a shape that is bent at substantially a right angle, and connects the optical waveguides 3 and 4.
The optical waveguide 14 has a shape in which two optical waveguides intersect at a substantially right angle, and connects the optical waveguides 1 and 4 and 3 and 2 respectively. Here, the optical waveguides 12 and 13 are configured such that the optical path length is the same as each optical path intersecting the optical waveguide 14.

The total reflection grooves 15 to 18 constitute the optical signal branching or merging means, and have a bottom surface shape of an isosceles triangle having a vertex angle of 45 ° here. The total reflection groove 15 is provided for the optical waveguides 12 and 14.
And a total reflection groove.
Reference numeral 16 is provided at a connection portion of the optical waveguides 12 and 14 on the optical waveguide 2 side. The total reflection groove 17 is provided at a connection portion of the optical waveguides 13 and 14 on the optical waveguide 3 side, and the total reflection groove 18 is provided at a connection portion of the optical waveguides 13 and 14 on the optical waveguide 4 side. Here, each of the total reflection grooves 15 to 18 is formed such that the bisector of the apex angle coincides with the center line of each of the optical waveguides 1 to 4.

The total reflection grooves 19 and 20 constitute refraction means for an optical signal, and have a substantially rectangular bottom shape here. The total reflection groove 19 is provided outside the refraction portion of the optical waveguide 12, and the total reflection groove 20 is provided outside the refraction portion of the optical waveguide 13. Here, the total reflection grooves 19 and 20 are formed such that one side thereof forms an angle of 45 ° with the center line of the optical waveguides 12 and 13.

Note that the depth of the total reflection grooves 15 to 20 is set to a depth that covers the entire optical waveguide portion of each optical waveguide.

In the above configuration, if a forward current is injected into the optical waveguides 12 and 13 but not into the optical waveguide 14, the optical waveguides 12 and 13 become gain waveguides, but the optical waveguide 14 becomes an absorption waveguide.
Therefore, for example, when a signal light having a wavelength within the gain width is incident on the optical waveguide 1, the signal light is totally reflected, that is, branched into the optical waveguides 12 and 14 by the total reflection groove 15 at a ratio of 1: 1.
Of these, the signal light branched to the optical waveguide 12 side is amplified here, reflected by the total reflection groove 19, propagates, and further
Through the optical waveguide 2. Similarly, the signal light incident from the optical waveguide 3 is also applied to the total reflection groove 17 and the optical waveguide 13.
(Including the total reflection groove 20), and is emitted to the optical waveguide 4 via the total reflection groove 18.

On the other hand, when a forward current is injected into the optical waveguide 14,
Reference numeral 14 denotes a gain waveguide. The signal light incident from the optical waveguide 1 and branched to the optical waveguide 14 by the total reflection groove 15 is amplified by the optical waveguide 14 and emitted to the optical waveguide 4 through the total reflection groove 18. Similarly, the signal light incident from the optical waveguide 3 is also emitted to the optical waveguide 2 via the total reflection groove 17, the optical waveguide 14, and the total reflection groove 16.

As described above, according to the embodiment, since the light is branched or merged by the total reflection action of the total reflection grooves 15 to 18, the depth of the groove is equal to the depth of the entire light guiding portion. In addition, it is not necessary to reduce the groove width as in the related art, and it is only necessary to keep the smoothness and the verticality of the side surface of the groove satisfactorily. Further, since the total reflection grooves 15 to 18 utilize the total reflection of light, a branching or merging characteristic having no wavelength dependence can be obtained, and a branching ratio of approximately 1: 1 can be obtained. Further, the optical waveguides 12 and 13 are connected to the total reflection groove 19 and
Since the optical path formed by the optical waveguide 14 is folded by 20, the lengths of the optical paths become equal, so that the insertion loss and the variation in isolation due to the set path can be reduced.

It should be noted that the shape of the bottom surface and the angle of the apex angle of the total reflection grooves 15 to 18 are merely examples, and are not limited thereto. Further, the optical waveguides 12 and 13 need only have the same optical path length as the optical path of the optical waveguide 14, and are not limited to the configuration using the total reflection grooves 19 and 20.

(Effects of the Invention) As described above, according to the present invention, since the optical signal branching or merging means is configured using the total reflection groove, the branching ratio does not depend on the groove depth, and therefore, the manufacturing is easy. At the same time, branching or merging is performed by total reflection of light, so that branching or merging characteristics without wavelength dependence can be obtained. In addition, since the optical waveguides are arranged so that the lengths of the optical paths that are branched or merged are equal, there is an advantage that insertion loss and variation in isolation due to the set optical paths can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical matrix switch of the present invention, and FIG. 2 is a block diagram showing an example of a conventional optical matrix switch. 1-4, 12-14: optical waveguide, 15-18: total reflection groove.

Claims (1)

(57) [Claims] In an optical matrix switch using an optical waveguide having a gate function, an optical signal branching or merging means is formed by using a total reflection groove, and the lengths of the branched and merged optical paths are equal. An optical matrix switch characterized by arranging optical waveguides as described above.