JPH0662450A - Self-routing optical switch and optical switch array - Google Patents

Abstract

PURPOSE:To acquire the information on an optical exchange which has a high function and large capacity by securing the connection of an optical path to which the information signal light is outputted in accordance with the presence or absence of the address signal light multiplexed with the information signal light in terms of the wavelength. CONSTITUTION:A switching area 3 and an optical waveguide 6 are formed on an InP substrate. The width of the waveguide 6 is set at 4mum with a Y-shaped optical waveguide branching angle set at 7 deg. respectively. The semiconductor laser light having the wavelength of 1.31mum is made incident on an input terminal 11 of an optical switch as an information signal. Then the semiconductor pulse light having the wavelength of 1.27mum is superposed on the semiconductor laser light as the address signal light. When the optical intensity of the address signal light is low, the information signal light is almost radiated through an output terminal 12. When the intensity of the address signal light is increased, the optical intensity of the information signal light received from the terminal 12 is reduced and radiated through an output terminal 13. The information signal light is completely switched to a radiation terminal 13 from the radiation terminal 12 with incidence of the address signal light of about 0dBm. Thus the inserting loss and the crosstalk value are set at 5dB and -25dB respectively to secure the performance almost equal to a conventional optical switch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical components in optical information processing and optical communication systems, and more particularly to a large-capacity optical switch for exchanging broadband and high-speed optical signals.

[0002]

2. Description of the Related Art Conventional semiconductor waveguide type optical switches and optical switch arrays, and integrated semiconductor waveguide type optical switches used in optical switches are described in Eye Triple E, Journal on Selected Areas in Communication Vol. 6, 1262. Pp-1266
Page, 1988 [IEEE Journal on Selected Areas in C
ommunications, J-SAC-6, pp1262-126
6, 1988].

[0003]

The above-mentioned prior art is a method of shortening the element length of a waveguide type optical switch and enabling a large-scale integration on a semiconductor substrate. We have proposed a two-way crossing type structure, and have realized a compact optical switch array suitable for large-scale integration and suitable for large-capacity optical switching equipment. However, regarding the method of identifying the destination of the information signal and connecting the input and output ends of the optical switch array, no consideration is given, and the destination included in the normal information signal is once converted into an electric signal, It was necessary to read it and operate the drive circuit of the optical switch array according to the destination. For this reason, when the signal speed increases, the control drive circuit becomes complicated when applied to an exchange that exchanges a large amount of information, and there is a problem that it is difficult to achieve further large-scale and high-density integration.

An object of the present invention is to solve the above problems and to have a novel function (self-routing function) of automatically outputting the information signal itself to the destination output end based on the destination information included in the information signal. An object is to provide an optical switch and an optical switch array for an optical switch.

[0005]

The above object is achieved by controlling the connection of an optical switch using at least a destination signal light superimposed on an information signal light.

[0006]

When carriers (electrons and / or holes) are injected into the compound semiconductor material, the carrier density in the semiconductor is changed in the injected region, and the refractive index is changed according to the change in the carrier density. In the carrier injection type optical switch in the conventional example, a pn junction is formed in a switching region, and a current is passed to change the carrier density, that is, the refractive index of the switching region. In the present invention, the switching area is made to absorb only the destination signal light having a wavelength different from that of the information signal light multiplexed with the information signal light, and the carrier density (refractive index) of the area is sufficient for the information signal light to pass through. Change only for a certain time. That is, the information signal light to be connected is changed for the same duration or longer time including it. As a result, the optical switch can be operated without specially controlling the destination with an externally applied signal to the switch section, so that the self-routing of the information signal light becomes possible. Furthermore, in order to construct an optical switch array by connecting this optical switch in multiple stages, the optical absorption edge wavelength in the switching area of the next optical switch is longer than the optical absorption edge wavelength in the switching area of the previous optical switch. If it is set to be shorter than the wavelength, a multi-stage configuration becomes possible and a self-routing optical switch array can be easily realized.
That is, the wavelength of the information signal light is λ _s , the absorption edge wavelength of the _n- th switching region of the multi-stage (provisionally m-stage) optical switch array is used as λ _n , and the n-th optical switch is used. Let λ be the wavelength of the destination signal light multiplexed with the information signal light.
Let _an be λ _a1 <λ ₁ <λ _a2 <λ ₂ <... <λ _an <λ _n <… <λ _am
It may be set so that the relationship of <λ _m <λ _s holds. Here, in order to make the absorption spectrum characteristic of the switching region steep,
If a structure having a quantum size effect, such as a multiple quantum well, a quantum wire, and a quantum box, is introduced into at least this region, the wavelength intervals can be made narrower, so that the capacity of the present optical switch array can be further increased. Further, the quantum size effect causes a large change in the refractive index as compared with the bulk material with respect to the change in the carrier density, so that high efficiency can also be achieved.

[0007]

EXAMPLES Example 1 In this example, the Y-type optical switch shown in FIG. 1 was constructed. 2 and 3 show examples of sectional views of the portion indicated by the broken line 1 in FIG. In this embodiment, MO is formed on the InP substrate 2.
InGaA that becomes the switching region 3 by using the CVD method
After growing the sP light absorption layer 31 (absorption edge wavelength λo = 1.29 μm), only the switching region 3 is left and other I
The nGaAsP light absorption layer 31 was removed. After this, MOC
An InGaAsP optical waveguide layer 4 (absorption edge wavelength λg = 1.15 μm) was selectively formed in the portion where the light absorption layer 31 was removed by using the selective growth technique of the VD method. Next, the optical waveguide 6 having the shape shown in FIG. 1 was formed by the usual lithography technique and etching technique. The width of the formed optical waveguide 6 is 4
μm, and the branch angle of the Y-shaped optical waveguide is 7 °. Finally, buried growth with the InP clad layer 5 was performed.

A semiconductor laser beam having a wavelength of 1.31 μm was incident on the input end 11 of the manufactured optical switch as an information signal. Semiconductor laser pulse light having a wavelength of 1.27 μm was superimposed on this incident light as destination signal light, and the light emitted from the output ends 12 and 13 was measured. When the light intensity of the destination signal light was weak, most of the information signal light was emitted from the output end 12, but as the light intensity of the destination signal light was increased, the light of the information signal light emitted from the output end 12 gradually increased. The intensity was reduced and the light was emitted from the output end 13. When the destination signal light of about 0 dBm was made incident, the emission end 12 of the information signal light was almost completely switched to the emission end 13, and the insertion loss and the crosstalk amount were 5 dB and -25 dB, respectively. This value was comparable to the conventional optical switch driven by current injection, and the self-routing function of the optical switch by wavelength multiplexing of the information signal light and the destination signal light, which is the principle of the present invention, was confirmed.

In this embodiment, the buried type optical waveguide structure shown in FIG. 2 is used as the cross-sectional structure of the optical waveguide, but as shown in FIG. 3, the InGaAsP light absorption layer 32 is made of InGaAsP.
A shape embedded in the optical waveguide layer 4 may be used. At this time, the equivalent refractive index felt by the guided light is InGaAsP.
Even if the light absorption layer 32 is partially present in the InGaAsP optical waveguide layer 4, if the dimensions are set to be almost equal,
Since the leakage of the information signal light to the output end 13 when the destination signal light is not incident is reduced, the characteristics of the optical switch are improved. Further, although the buried type optical waveguide structure is used in FIGS. 2 and 3, a refractive index guided type optical waveguide such as a ridge type, a loading type, a BH type and a CSP type which is a structure of an optical waveguide which is usually used. It goes without saying that the same effect can be obtained by using the structure. Although InGaAsP is used as the semiconductor material, other semiconductor material such as GaAlA is used.
The same effect can be obtained by using a III-V group system or a II-VI group system such as an s-based or InGaAlAs-based system.

Example 2 In this example, the Y-type optical switch of Example 1 was replaced with the X-type and single-sided crossing type optical switches shown in FIGS. The structure of the optical waveguide is similar to that of the first embodiment. The information signal light and the destination signal light were made incident on the input ends 41, 42 of the manufactured X-type optical switch of FIG. 4 in the same manner as in Example 1, and the characteristics of the light emitted at the output ends 43, 44 were examined. Also, in the one-way crossing type optical switch shown in FIG. 5, the information signal light and the destination signal light are made incident on the input end 51 to output the output end 5.
The characteristics of the light emitted from 2, 53 were examined. as a result,
The same results as in Example 1 were obtained, and it was confirmed that the present invention is effective without depending on the construction method of the optical switch.

Example 3 In this example, the optical switches described in Examples 1 and 2 were arranged in the shape shown in FIG. 7 to form an optical switch array, and the basic function of self-routing was confirmed. The optical switch 100 of the present invention, which has been described in detail in the first and second embodiments, is schematically written as shown in FIG. 6 in order to briefly describe the configuration. The information signal light incident from the input end 60 is emitted from the output end 61 when the destination signal light is present, and is emitted from the output end 62 when the destination signal light is absent. The optical switches were arranged in an array with the three-stage configuration of FIG. 7, and a light wave obtained by wavelength-multiplexing the information signal light and the destination signal light was made incident from the input end 70. Since the multistage configuration is used in this embodiment, the absorption edge wavelength λ ₁ of the light absorption layer in the switching region of the first-stage optical switch 111 and the light absorption in the switching region of the second-stage optical switches 121 and 122. The absorption edge wavelength λ ₂ of the layer and the absorption edge wavelength λ ₃ of the light absorption layer in the switching region of the third-stage optical switch 131, 132, 133, 134 have a relationship of λ ₁ <λ ₂ <λ _3. There is. Here, the output end 7 is used as the destination signal light.
In order to emit the information signal light to the appropriate output terminals 1 to 78, the wavelength-multiplexed light having the relationship shown in FIG. 8 was used. Here, [0] in FIG. 8 indicates that lights of corresponding wavelengths are not multiplexed, and [1] indicates that they are multiplexed. That is, the destination code according to the bit configuration with or without three waves corresponds to the destination bit number (output end code) corresponding to the output end. As a result, the information signal light in which the destination signal light is multiplexed is self-routed and automatically guided to the corresponding destination output end and emitted. The wavelength of the information signal light at this time is λ _s , and the wavelength of the destination signal light multiplexed with the information signal light used in the optical switch at each stage is λ _s .
_{If a1} , λ _a2 , and λ _a3 are satisfied, the relationship of λ _a1 <λ ₁ <λ _a2 <λ ₂ <λ _a3 <λ ₃ <λ _s holds.

In this embodiment, three optical switch arrays are used.
Although the tree structure having a step structure has been described, it is needless to say that the same effect can be obtained with a structure having four or more steps and also with an array structure other than the tree structure, such as a crossbar, a simplified tree, a batcher, or a banyan.

[0013]

According to the present invention, there is provided an optical switch and an optical switch array which are small in size and have a new function (self-routing function) of outputting an information signal light to the output terminal according to a destination signal of its own. Therefore, it is possible to construct a high-performance, large-capacity optical switch in a new optical information processing and communication system.

[Brief description of drawings]

FIG. 1 is a waveguide structure diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a waveguide structure cross section in Example 1;

FIG. 3 is a diagram showing another example of the cross section of the waveguide structure according to the first embodiment.

FIG. 4 is a diagram showing an example of a waveguide structure of Example 2;

FIG. 5 is a diagram showing another example of the waveguide structure according to the second embodiment.

FIG. 6 is a diagram schematically showing the optical switch of the present invention.

FIG. 7 is a diagram showing an example of an optical switch array configuration according to a third embodiment.

FIG. 8 is a diagram illustrating an operation of a self-routing function according to a third embodiment.

[Explanation of symbols]

1 ... Dashed line showing position of cross-sectional structure diagram, 2 ... InP substrate, 3
... switching region, 4 ... InGaAsP optical waveguide layer, 5
... InP clad layer, 6 ... Optical waveguide, 11 ... Input end of Example 1, 12, 13 ... Output end of Example 1, 31, 32 ...
InGaAsP absorption layer, 41 ... Input end of X-crossing optical switch of the second embodiment, 42, 43 ... Output end of X-crossing optical switch of the second embodiment, 51 ... Input of crossover optical switch of the second embodiment Ends, 52, 53 ... Output ends of the one-way crossover type optical switch of the second embodiment, 60 ... Input ends of the optical switch schematically shown in the third embodiment, 61, 62 ... schematically shown in the third embodiment. Output end of optical switch, 70 ... Input end of optical switch schematically shown in the third embodiment, 71, 72, 73, 74, 7
5, 76, 77, 78 ... Output end of optical switch schematically shown in Example 3, 100 ... Optical switch schematically shown in Example 3, 111 ... First stage of optical switch array of Example 3 Optical switches 121, 122 ... Second-stage optical switches of the optical switch array of Example 3, 131, 132, 13
3,134 ... The third stage optical switch of the optical switch array of the third embodiment.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Shinji Nishimura 1-280 Higashi Koikeku, Kokubunji, Tokyo Metropolitan Institute of Hitachi, Ltd. (72) Inventor Mari Ogawa 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Central Research Laboratory (72) Inventor Koji Ishida 1-280, Higashi Koikekubo, Kokubunji, Tokyo Hitachi Research Center, Hitachi Ltd.

Claims (9)

[Claims] 1. A waveguide type optical switch using a compound semiconductor, wherein the information signal light is output depending on the presence or absence of destination signal light having destination information which is wavelength-multiplexed and superposed on information signal light having information. A self-routing optical switch characterized by connecting optical paths that should be used. 2. The wavelength of the information signal light is longer than the wavelength of the multiplexed destination signal light.
Self-routing optical switch described. 3. In the optical switch and the optical switch array, the destination signal light having a time width longer than a time width for maintaining connection of optical paths for a certain time and completing connection of the information signal light is wavelength-converted to the information signal light. The self-routing optical switch according to claim 2, wherein the self-routing optical switch is multiplexed. 4. The method according to claim 2, wherein a part or all of the destination signal light is absorbed in a part of a region for switching an optical path, and a change in the refractive index of the part is induced. 3. The self-routing optical switch described in 3. 5. The self-routing optical switch according to claim 2, wherein the multiplexed destination signal light is at least two or more. 6. A self-routing optical switch according to claim 2, 3, 4 or 5, wherein at least a part of a portion of the optical switch where a change in refractive index is induced has a multiple quantum well structure. 7. A waveguide type optical switch using a compound semiconductor, wherein the information signal light is output according to the presence or absence of destination signal light having destination information which is wavelength-multiplexed and superposed on information signal light having information. A self-routing optical switch array composed of multiple stages of optical switches that connect the appropriate optical paths. 8. The absorption edge wavelength of the switching region of the n-th optical switch of the optical switch array constructed by connecting m-stage optical switches to λ _n , and the information signal light used in the n-th optical switch. When the wavelength of the destination signal light to be multiplexed is λ _an and the wavelength of the information signal light is λ _s , these wavelengths are λ _a1 <λ ₁ <λ _a2 <λ ₂ <... <λ _an <λ _n <… < λ _am
A self-routing optical switch array, characterized in that the relationship <λ _m <λ _s is established. 9. An optical switch formed by using the self-routing optical switch according to claim 1.