JPH02230219A - Optical matrix switch - Google Patents

Abstract

PURPOSE:To obtain a small-sized optical matrix switch which is easily manufactured and has low loss and high reliability by composing the switch of only plural 1X2 optical branching and confluence circuits and optical gate elements. CONSTITUTION:Signal light which is made incident on one confluence-side optical waveguide 1 is branched by a 1X2 branching and confluence circuit 3 into two branch-side optical waveguides 2; and the traveling of the branched signal light beams is controlled by the gating operation of an optical gate elements 5 arranged on their propagation branch-side optical waveguides 2. Then the signal light passed through the optical gate element 5 reaches another 1X2 optical branching and confluence circuit 3 and is guides to one confluence- side optical waveguide 1 for confluence, propagated in the confluence-side optical waveguide 1, and projected from the optical matrix switch. Consequently, excessive loss at the time of the branching and confluence of light is small, and the switch is easily manufactured and integrated highly to small size.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical matrix switch using an optical gate element and a branching/merging circuit.

(Prior Art) FIG. 2 is a block diagram showing a 4×4 optical matrix switch as an example of a conventional optical matrix switch of this type. In Figure 2, Ii (i-1 to 4) is the input terminal, O
f is an output end, 1 is a merging side optical waveguide, 2 is a branching side optical waveguide, 3 is a 1×2 optical branching/merging circuit, 4 is a 2×2 optical branching/merging circuit, and 5 is a semiconductor optical gate element having a PN junction. , 1× at the intersection of the merging side optical waveguide 1 and the two branching side optical waveguides 2
A two-light branching/merging circuit 3 is arranged, and two branching side optical waveguides 2 are arranged.
A 2×2 optical branching and merging circuit 4 is arranged at the intersection between the two, and a branching side optical waveguide 2 and a 1×2 optical branching and merging circuit 3 and 2 are connected between the two 1×2 optical branching and merging circuits 3. A 4×4 optical matrix switch is constructed by inserting and arranging semiconductor optical gate elements 5 into the branching optical waveguides 2 that connect the ×2 optical branching/merging circuit 4.

The semiconductor optical gate device 5 having the above-mentioned PN junction is described in literature (for example, M. Ikeda, “Las
er dlode svltch” lELeetro
n % t, ett, vol. 17, No. 23, pp.
J99-900.1981), the operating principle will be briefly explained here.

For example, when a forward current is injected into the semiconductor optical gate device 5 having a PN junction, the so-called active layer becomes a gain waveguide, similar to the operating principle of a semiconductor laser. Therefore, if the signal light has a wavelength within the gain width, the input signal light is amplified and emitted. On the other hand, when no current is injected into the semiconductor optical gate element 5, the input signal light is absorbed by the active layer, so no output signal light is emitted.

In this way, by turning on and off the forward current of the semiconductor optical gate element 5, gating of signal light can be performed.

Therefore, in the optical matrix switch shown in FIG. 2, in order to set a path from an arbitrary input terminal Ii to an arbitrary output terminal Oi, a semiconductor optical gate element placed in the middle of the route, that is, in the branch optical waveguide 2, is required. This is achieved by injecting forward current. As a result, the input signal light incident on the input end 1i is transmitted from the output end 01 via the merging side optical waveguide 1, the 1×2 optical branching/merging circuit 3, the branching optical waveguide 2, or the 2×2 optical branching/merging circuit 4. It will be emitted.

(Problem to be solved by the invention) However, in the optical matrix switch described above, 2X
Since the two-light branching/merging circuit 4 is arranged, there is a drawback that the loss is large and the reliability is poor. The reason is explained below.

FIG. M3 is a configuration diagram of the 2X2 optical branching/merging circuit 4. In FIG. 3, 4a is a branching and merging groove (hereinafter referred to as branching groove), which connects the input branch side optical waveguide 2a-1 or 2.
The signal light incident from b-1 is branched into branch photometric waveguides 2a-2 and 2b-2 for output. This branch groove 4a is
The optical waveguides 2a and 2b are provided at symmetrical positions at the intersection of the optical waveguides 2a and 2b, and the branching ratio thereof is controlled by setting the depth of the groove and the refractive index of the material buried in the groove to desired values.

When these circuits are constructed from semiconductor materials, the core size is 5 μm or less under the condition that the optical waveguide is in a single mode. On the other hand, the branch groove 4a is manufactured using photolithography technology and reactive or ion beam etching technology, but with the current technology, two
It is difficult to accurately manufacture branch grooves 48 having a width of μm or less.

Therefore, as shown by arrow A in FIG.
If the width is the same as that of the evening limit, the optical axis of the signal light reflected from the branch groove 481 will be misaligned with the central axis of the branch optical waveguide 2a-2 or 2b-2.

Such a shift in the optical axis in a single mode optical waveguide causes a large coupling loss. For example, if the branch angle is 45
If the width of the branch groove 4a is 2 μm, the amount of deviation of the optical axis is 1.85 μm, and the coupling loss of the reflected light is 3 μm.
dB or more. In fact, an optical waveguide was fabricated using InGaAsP/InP semiconductor materials, and Cg2 reactive
When a 2×2 optical branch circuit was fabricated by forming a branch groove with a width of 2 μm by ion beam etching, the coupling loss to the optical waveguide on the reflection side was not less than 5 dB. Of this, the extra 2 dB of loss is thought to be due to poor smoothness of the branch grooves and the fact that the grooves were not cut perpendicularly but became groove-like.

The present invention has been made in view of the above circumstances, and its purpose is to make it small, easy to manufacture, and with low loss.
Our objective is to provide a highly reliable optical matrix switch.

(Means for Solving the Problems) In order to achieve the above object, in claim (1), the signal light propagated through the optical waveguide is branched into two optical waveguides, and
It has a plurality of 1x2 optical branching and merging circuits that combine the two signal lights propagated through these two optical waveguides into the one optical waveguide, and one optical waveguide on the branch side of the one 1x2 optical branching and merging circuit; One optical waveguide on the branch side of another 1×2 optical branching/merging circuit was connected to each other, and optical gate elements were placed at these connection points.

Moreover, in claim (2), the optical axes of each optical gate element are arranged in parallel.

(Function) According to claim (1), for example, a signal light incident on one merging optical waveguide is branched into two branching optical waveguides by one 1×2 optical branching and merging circuit. . The progress of each of these branched signal lights is controlled by the gating operation of an optical gate element disposed in the branch-side optical waveguide through which they propagate. Due to this gating operation, the signal light that has passed through the optical gate element reaches another 1×2 optical branching/merging circuit.
It merges into one merging side optical waveguide, propagates through this merging side optical waveguide, and is emitted from the optical matrix switch.

Second, according to claim (2), an optical matrix switch can be constructed using a plurality of optical gate elements having uniform characteristics.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of a 4×4 optical matrix switch according to the present invention, and the same components as those in FIG. 2 showing a conventional example are denoted by the same reference numerals. That is, I i
(i-1 to 4) are input terminals, Oi is an output terminal, 1 is a merging side optical waveguide, 2 is a branching side optical waveguide, 3 is a 1×2 optical branching/merging circuit, and 5 is a semiconductor optical gate element having a PN junction. It is.

The 1×2 optical branching and merging circuit 3 transmits and reflects the signal light propagated through the merging optical waveguide 1 to branch into two branching optical waveguides 2, and conversely propagates through the two branching optical waveguides 2. The signal light is merged into the merging side optical waveguide 1.

FIG. 4 is a block diagram of a 1×2 optical branching/merging circuit 3 having such a function. In FIG. 4, 3a is a branching and merging groove (hereinafter referred to as branching groove) with a full width of approximately 2 μm, and the signal light incident from the merging side optical waveguide 1 is transferred to the branching side optical waveguide 2-
1.2-2, and the branch side optical waveguide 2-1.2
The two signal lights incident from -2 are merged into the merge side optical waveguide 1.

As shown in FIG. 4, this branching groove 3a is an intersection between the merging optical waveguide 1 and the branching optical waveguide 2-1 arranged in a straight line, and the branching optical waveguide 2-2, which intersects at a predetermined branching angle. The reflective surface 3ar is arranged on the so-called diagonal line of the part,
The configuration is such that the optical axis of the reflected light does not deviate from the central axis of the branch optical waveguide 2-2.

The optical matrix switch shown in Figure 1 has these functions.
The 1×2 optical branching/merging circuit 3 having the configuration is arranged in 24 rows and 6 columns.
The merging side optical waveguide 1 of the 1×2 optical branching/merging circuit 3 in the first column is used as the input optical waveguide, and the merging side optical waveguide 1 of the 1×2 optical branching/merging circuit 3 in the sixth column is arranged in a matrix. 1 is an output optical waveguide, and the branch side optical guides of each 1×2 optical branching/merging circuit 3 in the first and second columns, the third and fourth columns, and the fifth and sixth columns are The waveguides 2 are arbitrarily connected to each other, and the merging side optical waveguides 1 of each of the 1×2 optical branching and merging circuits 3 in the second and third columns and the fourth and fifth columns are connected to each other. And furthermore,
Semiconductor optical gate elements 5 are respectively arranged at the connection points between the branch optical waveguides 2 to form a 4×4 optical matrix switch.

In such a configuration, in order to set a path from an arbitrary input terminal It to an arbitrary output terminal Oi, a semiconductor optical gate element 5 placed in the middle of the route, that is, in the branch optical waveguide 2 is required.
This is achieved by injecting a forward current into the As a result, the input signal light incident on the input end It is outputted from the output end Oi via each merging side optical waveguide 1, 1x2 optical branching and merging circuit 3, and branching side optical waveguide 2 on the set path. will be done.

At this time, when the signal light is branched or merged in the 1×2 optical branching/merging circuit 3, the optical axis of the reflected light does not deviate from the central axis of the branching optical waveguide 2, as described above, and
Regarding the transmitted light, when the width of the branching groove 38 is about 2 μm, there is no shift in the optical axis of the transmitted light, and the coupling loss is extremely small.

As described above, according to the first embodiment, a so-called link-type optical matrix switch is configured using only a plurality of 1×2 optical branching/merging circuits 3 having the configuration shown in FIG. 4 above. This makes it possible to create a compact, low-loss optical matrix switch.

Further, the width of the branching groove 38 of the 1×2 optical branching and merging circuit 3 is 2μ.
Since it can be relatively wide, about m, it is easy to manufacture an optical matrix switch.

FIG. 5 is a configuration diagram showing a second embodiment of a 4×4 optical matrix switch according to the present invention. The difference between the second embodiment and the first embodiment is that the optical axes of the semiconductor optical gate elements 5 inserted at the midpoints of connections between the branch optical waveguides 2 are all arranged in parallel.

In addition to the effects of the first embodiment, the second embodiment having such a configuration is effective in facilitating the fabrication of the semiconductor optical gate device 5 and making the characteristics uniform. In particular, the crystal orientation is unidirectional for the optical axis of the branch-side optical waveguide 2 of the semiconductor optical gate element 5 during buried growth of a vertical cross section or for etching processing when forming a ridge-type optical waveguide. is easy.

FIG. 6 is a configuration diagram showing a third embodiment of a 4×4 optical matrix switch according to the present invention. The difference between this third embodiment and the second embodiment is that the so-called branching and merging sections of each 1×2 optical branching and merging circuit 3 are configured symmetrically, and the 3 dB
It is located at the cutter 31, and the same effects as in the second embodiment can be obtained.

Further, although the 3 dB coupler 31 in the third embodiment is of a linear type, it may be of a curved type, and it goes without saying that any other 3 dB coupler may be used.

In addition, in the first to third embodiments, the explanation was given using a 4×4 optical matrix switch as an example, but the invention is not limited to this. It goes without saying that the present invention can also be applied to large-scale optical matrix switches such as...

(Effect of the invention) As explained above, according to claim (1), a plurality of
Since the optical matrix switch is constructed using only the ×2 optical branching/merging circuit and the optical gate element, it has the following advantages.

■Excess loss when signal light is branched or merged can be reduced.

■It has a large manufacturing tolerance and can be manufactured easily.

■Compact and highly integrated.

■Since it is possible to configure a so-called link-type optical switch network,
The multiplicity of the set path between input and output terminals is increased, providing excellent flexibility in use.

Further, according to claim (2), it is possible to easily manufacture an optical gate element, and in addition to the effect of claim (1) described above, there is an advantage that an optical matrix switch can be easily manufactured.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a first embodiment of a 4 x 4 optical matrix switch according to the present invention, Fig. 2 is a block diagram of a conventional 4 x 4 optical matrix switch, and Fig. 3 is a 2 x 2 optical branching/merging circuit. FIG. 4 is a configuration diagram of a 1×2 optical branch/combine circuit according to the present invention, FIG. 5 is a configuration diagram showing a second embodiment of a 4×4 optical matrix switch according to the present invention, and FIG. The figure is a configuration diagram showing a third embodiment of a 4×4 optical matrix switch according to the present invention. In the figure, 1... Merging side optical waveguide, 2... Branching side optical waveguide, 3... 1x2 optical branch/combine circuit, 31...3dB
Coupler, 5... semiconductor optical gate element. Patent applicant Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] (1) 1×2 optical branching/merging in which the signal light propagated through one optical waveguide is branched into two optical waveguides, and the two signal lights propagated through these two optical waveguides are merged into the first optical waveguide. It has a plurality of circuits, and one optical waveguide on the branch side of one 1×2 optical branching and merging circuit;
An optical matrix switch characterized in that the optical waveguides are connected to one optical waveguide on the branch side of another 1×2 optical branching/merging circuit, and optical gate elements are arranged at these connection points. (2) The optical matrix switch according to claim (1), wherein the optical axes of each of the optical gate elements are arranged in parallel.