JPS59135441A - Optical waveguide switch - Google Patents

Abstract

PURPOSE:To generate a gain for the light of a wavelength which is guided by arranging an optical amplifier in each branching path of an optical waveguide having plural branching paths and switching the excitation state. CONSTITUTION:Approximately uniform photoelectric power is distributed to two branching waveguide paths 3 and 3' from a main waveguide 1. The optical amplifiers 4 and 4' consist of a laser amplifying medium, and the medium is set to the excitation state by excitation from the external to generate a gain for the light of a wavelength which is guided, and it is outputted through output waveguides 5 and 5'. If the wavelength and the laser medium are selected properly, fairly intensive absorption is obtained. When the gain in the optical amplifier 4 is denoted as GdB and the absorption in the amplifier 4' is denoted as LdB, (-G+L)dB is attained as a crosstalk quantity observed in the output terminals of waveguides 5 and 5'. As the result, a high-speed optical switch is realized which does not required dimensions of an ultrahigh precision and has less crosstalk quantity.

Description

[Detailed description of the invention] The present invention relates to an optical waveguide switch that switches optical paths.

In information transmission systems using optical waveguides such as optical fibers, optical switches are required to switch optical signals from one waveguide to multiple waveguides at high speed in order to enable a flexible configuration of the information transmission network. It is. Conventionally, for such applications, there have been methods using light deflection using the acousto-optic effect of a light propagation medium, light deflection using the electro-optic effect of the medium, and electro-optic coupling coefficients for directional couplers. Various methods are being considered, such as those that change the effect depending on the effect, and those that combine a directional coupler and an optical phase modulator, but in both cases, in order to achieve low insertion loss characteristics and low crosstalk characteristics, extremely high Accurate optical waveguide fabrication technology is required. For example, in an optical switch using a directional coupler, in order to obtain a crosstalk characteristic of about -30 dB to -40 dB, the coupling length of the optical waveguide must be adjusted to about 10 μm. Further, the error in the thickness and width of the optical waveguide itself must be suppressed to 1 μm or less. Fabrication of such highly accurate optical waveguides is quite difficult with current technology.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide an optical waveguide switch which eliminates the above-mentioned drawbacks.

That is, the objective is to achieve low crosstalk characteristics even for optical waveguides with relatively low precision.

In order to achieve the above object, the present invention disposes an optical amplifier in each branch of an optical waveguide having a plurality of branches, and substantially changes the output optical signal of the amplifier by switching the excitation state of the optical amplifier. It is characterized by being constructed in such a way that it can be opened and closed.

The present invention will be described in detail below with reference to Examples.

FIG. 1 is a diagram showing the basic structure of the optical waveguide switch of the present invention, and in the figure, 1 is a main waveguide.

The optical signal guided to the main waveguide 1 is distributed to two branch waveguides 3 and 3' by a branching section 2 to have substantially equal optical power.

4 and 4' are optical amplifiers. An optical amplifier is composed of a laser amplification medium, and is pumped externally to bring the state of the medium into an excited state, thereby producing a gain for light of a guided wavelength. 5 and 5' are output waveguides.

Switching is performed by switching the excitation state of optical amplifier 4.4'. That is, when the optical amplifier 4 is in an excited state and the optical amplifier 41 is not in an excited state, the light branched into the waveguide 3 is amplified, but the light branched into the waveguide 3' is not amplified, and the wavelength and If the laser medium is appropriately selected, rather strong absorption can be caused. Therefore, for the amount of crosstalk observed at the output end of the waveguide 5°5', the gain in the optical amplifier 4 is e (dB), and the absorption at 4' is L(
-00L (dB) can be obtained as (dB). −
As an example, when a Ga, AIAs semiconductor laser (optical oscillator length 0.5 mm) is used as an optical amplifier, the gain will be around 20 dB, and the absorption loss in the unexcited state will be about 1. It is about 20dB.

Therefore, a total crosstalk amount of about -40 dB can be achieved relatively easily. Main wave/path 1, branch 2 and waveguide 3.3'
, 5.5' need only have the function of guiding light, and ultra-precise waveguide fabrication technology is not required.

The above-mentioned FIG. 1 shows the basic configuration, and the actual configuration can be realized in various ways. Namely.

Branch waveguides can be made by directly branching optical fibers, constructed on dielectric substrates, or constructed on semiconductor substrates. It can also be configured with a Y-shaped branch as shown in FIG. 1, a distributed coupling type as shown in FIG.

In addition, in the same figure, the main waveguide 2' is a distributed coupling part at 1,
3 and 3' are branch waveguides. On the other hand, semiconductor lasers (Noavry-Perot cavity type, distributed feedback (distributed feedback)
The object of the present invention can be achieved by appropriately combining lasers such as OF' B type, blank reflection (DBJ type, etc.), and fiber type lasers.

However, in order to construct a compact optical waveguide switch, it is desirable to construct branch waveguides and optical amplifiers in a seven-dimensional structure on one substrate.

An example of such a structure may be one in which a (2)aAs semiconductor is used as a substrate, and GaAJAs and GaAs semiconductor layers are laminated in multiple layers on this substrate to provide the above-mentioned functions. FIGS. 3 and 4 show a plan view and a partial cross-sectional configuration of an embodiment of the optical waveguide switch according to the present invention. The branch waveguide is an n-type () a p on the A s substrate 6.
Type A7Io3Gao7ASf: obtained by laminating klo and Gao9 As, which will become the waveguide layer 9, on top of it in a Y-shaped branch pattern. The optical amplifying sections 4 and 41 are composed of a so-called double heterostructure distributed feedback laser, and the structure includes a pn-UaS substrate 6, a N-A layer, and a UaO7A s layer 1 at the bottom. (), p-A
l o,:+ ()a o,'y A 8 layers 8, p-(
+aAs layer 11, p-kl o,z ()ao8A s
Layer 12, p A 71oo 7Ga o, 93 As
Layer 13, p A l o3 Ga 0.7 A s Layer 1
4 (this type of DFB laser is described in the literature as Ai
Ki.

etaJ, AppA, Phys, Lett, vol, 2
9P.

506 1976). p"0.07G
ao93As layer 13 and p A e o, 2 ()a
Corrugations are provided at appropriate intervals between the O, s As layers 12, and are designed to have a gain for a desired wavelength. By flowing a current in the forward direction between the upper electrode 15 and the lower electrode 7, light is amplified in this region, and an optical switching operation can be obtained by switching the currents supplied to the two optical amplifiers.

Note that the switching speed is essentially high because it utilizes the turning on and off of the laser excited state of the semiconductor.

In addition, although the above-mentioned embodiment described the case of two for simplicity of explanation, it is clear that the number can be two or more.

As described above, according to the present invention, it is possible to realize a high-speed optical switch with a low amount of crosstalk, which does not require ultra-high precision dimensions for the optical waveguide.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the principle configuration of the present invention, Fig. 2 is a diagram showing a distributed coupling type branching, and Figs. FIG. 7 is a plan view γS and a partial sectional view thereof. ]... Main r) 155.2... Branch part, 3... Branch waveguide, 4... Optical amplifier, 5... Optical waveguide. No. 1? Zen meal

Claims (1)

[Claims] An optical branching waveguide that branches one optical waveguide into a plurality of optical waveguides, an optical waveguide connected to the plurality of branched optical waveguides via an optical amplifier, and switching the excitation state of the optical amplifier. An optical waveguide switch comprising: means.