JP2016033546A - Tree type optical switch constitution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of control terminals to one, and thereby downsize an element.SOLUTION: In a tree type optical switch structure 20 of a Mach-Zehnder type optical switch SW, a phase modulation region and a phase adjustment region are formed in one arm optical waveguide of each optical switch SW. The length of the phase modulation region is L at a first step, and L/2 at a second step. The phase difference capable of being imparted by the phase adjustment region is 0 at the first step, and 0 and -π/4 at the second step. Then, one control terminal CT1 and the electrode terminal of each optical switch SW are connected by an electric wiring LE.SELECTED DRAWING: Figure 1

Description

  The present invention is devised so that a switching operation to a large number of output ports can be performed while reducing the number of control terminals in a tree-type optical switch configuration used in optical information communication.

  Optical communication has the features of large capacity and ultra-high speed, and has been put into practical use in many information communication networks in recent years. In such a network, research and development of increasing the transmission speed and wavelength multiplexing for superimposing a plurality of wavelengths are being carried out as measures for increasing the capacity.

  On the other hand, each network node is linked to a plurality of nodes by optical fibers, and in order to realize efficient traffic, it is necessary to flexibly change the path connecting the nodes.

  Here, when the optical connection is made point-to-point, optical / electrical conversion is performed at the input terminal of the node, switching is performed by an electrical switch, and electrical / optical conversion is performed again at the output terminal of the node to transmit a signal. The In this case, a large amount of power is consumed when optical / electrical conversion is performed or when high-speed switching is performed using an electrical switch.

  On the other hand, research and development has been conducted to arrange and switch an optical switch in a node. In this case, since the optical signal path itself is switched by the optical switch and the path is changed as it is, the optical / electrical conversion or the high-speed switching by the electric switch is not necessary, and the high-speed optical signal is consumed with low power consumption. Can be switched.

As such an optical switch, a thermo-optic switch (TOSW) configured on a glass-based planar light wave circuit (PLC), an InP-based optical modulator, or a semiconductor optical amplifier (SOA) : Semiconductor Optical Amplifier) and switches using LiNbO ₃ -based optical modulators are being researched and developed.

As main optical switch configurations, a crossbar type optical switch configuration capable of performing N × N optical switching and a tree type optical switch configuration capable of performing 1 × N optical switching have been researched and developed.
Also, N 1 × N tree-type optical switch configurations are used on the input side, N N × 1 tree-type optical switch configurations are used on the output side, and the input-side tree-type optical switch configuration and the output-side tree type are used. By connecting the optical switch configuration, a non-blocking N × N optical switch can be realized (see, for example, Non-Patent Document 1).

Here, a 1 × N (1 input, N output) tree-type optical switch configuration 10 according to the prior art will be described with reference to FIG.
In the following description, the symbol “SW” is used to collectively refer to optical switches, and the symbol “SW11, SW21, SW22...” Or the like is used to distinguish individual optical switches.

  The conventional tree-type optical switch configuration 10 shown in FIG. 5 has a 1 × 2 (one input, two output) optical switch SW as a basic component, and a total of seven optical switches SW are arranged in three stages in a tree shape. Connected and configured. Thereby, the tree-type optical switch configuration 10 functions as a 1 × 8 optical switch.

More specifically, in the tree-type optical switch configuration 10, one optical switch SW11 is arranged at the first stage (uppermost stage), two optical switches SW21 and SW22 are arranged at the second stage, and the third stage (uppermost stage). In the lower part, four optical switches SW31, SW32, SW33, SW34 are arranged.
Each optical switch SW is arranged in such a direction that one input port I is located on the upper side and two output ports O are located on the lower side, and each optical switch SW is connected to each output port O of the upper optical switch. The upper and lower optical switches SW are connected by an optical waveguide LL so that the input port I of the lower optical switch is connected.

  As a typical 1 × 2 optical switch SW, a Mach-Zehnder (Mach-Zehnder) type optical phase modulator is used.

As shown in FIG. 6, the MZ type optical phase modulator includes an input-side directional coupler Y1, an output-side directional coupler Y2, and input-side and output-side directional couplers Y1 and Y2. Two arm optical waveguides A1 and A2 to be connected, one input port I connected to the directional coupler Y1 on the input side, and two output ports O connected to the directional coupler Y2 on the output side doing.
The directional coupler Y1 on the input side has a characteristic of dividing the light intensity into two equal parts, and the directional coupler Y2 on the output side has a characteristic of coupling light. Further, the optical waveguide lengths of the two arm optical waveguides A1 and A2 are equal. A phase modulation region PM is formed in one arm optical waveguide A1, and an electrode terminal ET is disposed on the phase modulation region PM.

In such an optical switch SW using an MZ type optical phase modulator, when the signal light P is input to the input port I, voltage or current is supplied to the electrode terminal ET to perform phase modulation in the phase modulation region PM. By changing the phase difference between the arm optical waveguides A1 and A2 to 0 or π / 2, the signal light P is output from one of the two output ports O on the output side, that is, switching is performed. Can do.
That is, if the phase difference between the arm optical waveguides A1 and A2 is set to 0, the signal light P is output from the cross port (the right output port O in FIG. 6), and the phase difference between the optical arm optical waveguides A1 and A2 is calculated. With π / 2, the signal light P is output from the through port (the left output port O in FIG. 6).

  Returning to FIG. 5 and continuing the description, the tree-type optical switch configuration 10 includes the same number (7) of control terminals CT1 to CT7 as the number of optical switches SW (7). Each electrode terminal ET of each optical switch SW is individually supplied with voltage or current from the control electronic circuits C1 to C7 via the control terminals CT1 to CT7 and the electric wiring LE.

  By supplying voltage or current to the electrode terminal ET, the refractive index of the phase modulation region PM of the optical switch (MZ type optical phase modulator) SW changes, the phase is modulated, and a switching operation is performed.

Each control electronics C1~C7 the control voltage of which value 0 and the control voltage V ₀ which is a bolt, and has a voltage value of the phase difference and [pi / 2 between the arm optical waveguides A1, A2 V [pi _{/ 2} is output. Therefore, when the control voltage V ₀ is input from each control electronic circuit C1 to C7 to the electrode terminal ET of each optical switch SW, signal light is output from the cross port, and the electrode of each optical switch SW is output from each control electronic circuit C1 to C7. When the control voltage Vπ _{/ 2} is input to the terminal ET, signal light is output from the through port, and a switching operation can be performed.
FIG. 7 shows a phase fluctuation state due to voltage application of the 1 × 2 optical switch SW.

  In the tree-type optical switch configuration 10 shown in FIG. 5, by switching the optical switches SW at each stage, finally, a total of eight optical switches SW31, SW32, SW33, SW34 formed in the third stage are formed. The optical signal P can be output from any one of the output ports O.

T. Watanabe et al., `` Silica-based PLC 1 × 128 thermo-optic switch '' 27th European Conference on Optical Communication (ECOC), vol.2, pp. 134-135, 2001.

Generally speaking, in order to realize a 1 × 2 ^M (1 input, 2 ^M output) tree-type optical switch configuration, it is necessary to arrange the number of 1 × 2 optical switches represented by the following formulas in M stages. Yes (where M is an integer of 2 or more).

That is, the tree-type optical switch configuration having 2 ^M output ports is configured by connecting 2 ^M −1 optical switches (basic components) to M stages.

More specifically, in the tree-type optical switch configuration 10 shown in FIG. 5, M = 3, and a total of seven (= 2 ⁰ +2 ¹ +2 ² = 2 ³ −1) optical switches SW are 3 It was placed on the step, an optical switch structure of 1 × 2 ^3.
In the example of FIG. 5, the signal light P is output from the through port of the optical switch SW11, the signal light P is output from the cross port of the optical switch SW22, and the signal light P is output from the cross port of the optical switch SW33. By inputting the control voltage Vπ _{/ 2} to the optical switch SW11 and inputting the control voltage V ₀ to the optical switches SW22 and SW33, the signal light P is output from the cross port (right output port O) of the optical switch SW33. Is done.
At this time, since no signal light is originally input to the remaining other optical switches SW, either the control voltage V ₀ or the control voltage Vπ _{/ 2} may be input.

Further, the tree type optical switch configuration 10A shown in FIG. 8 has M = 2, and a total of three (= 2 ⁰ +2 ¹ = 2 ² −1) optical switches SW are arranged in two stages. 1 × 2 ² optical switch configuration.
In the example of FIG. 8, the control voltage Vπ _{/ 2} is input to the optical switches SW11 and SW22 so that the signal light is output from the through port of the optical switch SW11 and the signal light is output from the through port of the optical switch SW22. Accordingly, the signal light P is output from the through port (left output port O) of the optical switch SW22.
At this time, since no signal light is originally input to the remaining optical switch SW21, either the control voltage V ₀ or the control voltage Vπ _{/ 2} may be input.

In order to control such a tree-type optical switch configuration (switching operation), conventionally, it is necessary to provide one control terminal CT for one 1 × 2 optical switch.
For example, in the case of the 1 × 4 tree-type optical switch configuration shown in FIG. 8, three control terminals CT are required, and in the case of the 1 × 8 tree-type optical switch configuration shown in FIG. 7 are required, and in the case of a 1 × 16 tree-type optical switch configuration, 15 control terminals CT are required. That is, in the tree-type optical switch configuration, the number of control terminals CT increases as the number of output ports increases.

As the number of control terminals CT increases in this way, the electrical wiring LE becomes complicated and the configuration of the tree-type optical switch increases. Further, the required number of control electronic circuits C increases corresponding to the number of control terminals CT, which causes an increase in the size and power consumption of an optical switch device comprising a tree-type optical switch configuration and the control electronic circuit C.
It is self-evident that the above-described problem also causes a cost increase of the tree type optical switch configuration and the optical switch device.

  Therefore, in the conventional tree-type optical switch configuration, there has been a problem that the number of control terminals cannot be reduced without causing a decrease in the number of ports to be switched and deterioration in characteristics.

  An object of the present invention is to provide a tree-type optical switch configuration in which the number of control terminals can be reduced to one even when the number of output ports is large.

The present invention for solving the above problems
2 ^M −1 (where M is an integer equal to or greater than 2) Mach-Zehnder type optical switches connected in M stages, a tree type optical switch configuration having 2 ^M output ports,
A phase modulation region that is formed in one arm optical waveguide of each of the optical switches, performs a phase modulation operation by inputting a voltage or a current, and gives a phase difference of + phase to the signal light;
Formed in one arm optical waveguide of each of the optical switches, and a phase adjustment region that gives a phase difference of -phase to the signal light;
An electrode terminal disposed on the phase modulation region;
One control terminal,
The control terminal and each of the electrode terminals are connected, and electrical wiring that sends a voltage or current input to the control terminal to the electrode terminal;
Have
Of the optical switches, the length of the phase modulation region formed in the first-stage optical switch is a preset length, and the length of the phase modulation region formed in the second-stage and subsequent optical switches is The length is half of the length of the phase modulation region formed in the optical switch on the upper stage side by one stage with respect to the optical switch of the stage,
In the first stage, the phase difference provided by the phase adjustment region of the optical switch is 0,
In the second and subsequent stages, the phase difference provided by the phase adjustment region of the optical switch is − (π / 2 ^M ) × Q (where Q is a number increasing from 0 by 1, and the maximum value is 2 ^{( M-1)} -1)).

The present invention also provides
A control voltage that causes a phase modulation operation in the phase modulation region is input to the control terminal,
The control voltages are ^2M types of control voltages V0, V1, V2,... V2 ^{M having} different voltage values.
−1, the voltage value of the control voltage V0 is 0, and the voltage value of the control voltage V1 gives a phase difference of + π / 2 to the signal light when input to the phase modulation area of the first stage. After that, as the control voltages V2,... V2 ^M −1, the phase difference given to the signal light becomes + π / 2 when input to the first phase modulation region. It is a value that increases sequentially by + π / 2.

The present invention also provides
A control current that causes a phase modulation operation in the phase modulation region is input to the control terminal,
The control current is 2 ^M types of control currents I0, I1, I2,... I2 ^M −1 having different current values, the current value of the control current I0 is 0, and the current value of the control current I1 is the first current value. It is a value that can give a phase difference of + π / 2 to the signal light when it is input to the first-stage phase modulation region, and thereafter, as the control currents I2,... I2 ^M −1, It is characterized in that the phase difference added to the signal light when it is input to the phase modulation area at the stage is a value that gradually increases by + π / 2 to + π / 2.

In the tree-type optical switch configuration of the present invention, the number of control terminals of the tree-type optical switch configuration can be reduced without reducing the number of output ports that output signal light or causing characteristic deterioration.
As a result, the tree-type optical switch configuration (element) is downsized, the electrode wiring is simplified, the number of control electronic circuits is reduced, and the optical switch device comprising the tree-type optical configuration and control electronic circuits is downsized and the power consumption is reduced. Can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the tree type | mold optical switch structure and control electronic circuit based on Example 1 of this invention. The block diagram which shows the optical switch used for an Example. FIG. 3 is a characteristic diagram illustrating an operation state of each optical switch in the first embodiment. The block diagram which shows the tree type | mold optical switch structure and control electronic circuit which concern on Example 2 of this invention. The block diagram which shows the tree-type optical switch structure and control electronic circuit which concern on a prior art. The block diagram which shows the optical switch used for a prior art. The perspective view which shows the operation state of the optical switch in a prior art. The block diagram which shows the other tree type | mold optical switch structure and control electronic circuit based on a prior art.

  Hereinafter, a tree-type optical switch configuration according to the present invention will be described in detail based on examples.

[Example 1]
FIG. 1 is a configuration diagram showing a tree-type optical switch configuration 20 according to Embodiment 1 of the present invention.
The tree-type optical switch configuration 20 according to the first embodiment includes a 1 × 2 optical switch SW as a basic component, and is configured by connecting a total of three optical switches SW in a tree shape in two stages. .

More specifically, in the tree-type optical switch configuration 20, one optical switch SW11 is arranged at the first stage (uppermost stage), and two optical switches SW21 and SW22 are arranged at the second stage (lowermost stage). .
Each optical switch SW is arranged in such a direction that one input port I is located on the upper side and two output ports O are located on the lower side, and each optical switch SW is connected to each output port O of the upper optical switch. The upper and lower optical switches SW are connected by an optical waveguide LL so that the input port I of the lower optical switch is connected.

  As each optical switch SW, a Mach-Zehnder (Mach-Zehnder) type optical phase modulator is used.

As shown in FIG. 2, the MZ type optical phase modulator includes an directional coupler Y1 on the input side, a directional coupler Y2 on the output side, and directional couplers Y1 and Y2 on the input side and output side. Two arm optical waveguides A1 and A2 to be connected, one input port I connected to the directional coupler Y1 on the input side, and two output ports O connected to the directional coupler Y2 on the output side doing.
The directional coupler Y1 on the input side has a characteristic of dividing the light intensity into two equal parts, and the directional coupler Y2 on the output side has a characteristic of coupling light. Further, the lengths of the two arm optical waveguides A1 and A2 are equal.

Of the arm optical waveguides A1 and A2, a phase modulation region PM is formed in one arm optical waveguide A1, and an electrode terminal ET is disposed on the phase modulation region PM. The length of the phase modulation region PM along the light transmission direction will be described later.
Further, a phase adjustment region PA is formed in one arm optical waveguide A1. The amount of phase adjustment by the phase adjustment area PA will be described later.
After all, in one arm optical waveguide A1 of the arm optical waveguides A1 and A2, the phase modulation region PM and the phase adjustment region PA are arranged in series.

  In order to obtain phase modulation in the phase modulation region PM, the refractive index of the optical waveguide may be changed. In a glass-based optical waveguide, the temperature is controlled by applying a current to a heater (in this case, the electrode terminal becomes a heater), and the refractive index is changed using a TO (Thermo-Optic) effect. In an InP-based optical waveguide, the refractive index is changed by using a Franz-Keldysh (FK) effect by applying a voltage, a Quantum Confined Stark Effect (QCSE) effect, or a plasma effect by current injection. In the LN-based optical waveguide, the refractive index is changed using the Pockels effect caused by voltage application.

Here, description will be made using the FK effect by applying voltage in an InP-based optical waveguide.
A phase modulation region PM capable of applying a voltage with a pin structure to a part of one arm optical waveguide A1 of the MZ type optical modulator is manufactured. When a voltage is applied to this part with a reverse bias, phase fluctuations occur along with absorption changes due to the FK effect. The amount of phase fluctuation is determined by the product of the amount of change in refractive index per unit length due to the applied voltage and the length of the phase modulation region PM.

In such an optical switch SW using an MZ type optical phase modulator, when the signal light P is input to the input port I, a voltage is supplied to the electrode terminal ET to perform phase modulation in the phase modulation region PM and to adjust the phase. By adjusting the phase in the area PA, the signal light P can be output from one of the two output ports O on the output side, that is, switching can be performed.
That is, if the phase difference (optical optical path length difference) between the two arm optical waveguides A1 and A2 is ± nπ, light is output from the opposite optical waveguide (cross port) to which the two arm optical waveguides A1 and A2 are input, and the two arm optical waveguides A1 , A2 has a phase difference of ± (2n + 1) π / 2, the light is output from the same optical waveguide (through port) as the optical input (where n is an integer).

Returning to FIG. 1, the description of the tree-type optical switch configuration 20 will be continued.
As described above, the phase modulation region PM and the phase adjustment region PA are formed in one arm optical waveguide A1 of the optical switches (MZ type optical phase modulators) SW11, SW21, SW22, respectively.

The phase modulation region PM is a component that exists in the conventional tree-type optical switch configuration, but the length of the conventional phase modulation region PM is the same even if the stage where the optical switch SW is arranged is different. Met.
On the other hand, in the first embodiment, the length of the phase adjustment region PM (the length along the light transmission direction) varies depending on the arrangement stage of the optical switch. Specifically, the settings are as follows.
The length of the phase adjustment region PM of the first optical switch SW11 at the first stage is a predetermined length L set in advance.
The length of the phase modulation area PM of the first and second optical switches SW21 and SW22 in the second stage is L / 2.

The phase adjustment area PA is a component that did not exist in the conventional tree-type optical switch configuration. In the first embodiment, the phase difference ΔΦ that can be given by adjusting the phase in the phase adjustment area PA is set as follows.
The phase difference ΔΦ means the phase difference of the signal light P that has passed through the phase adjustment area PA with respect to the signal light P input to the phase adjustment area PA.
The phase difference ΔΦ that can be given by the phase adjustment area PA of the first-stage optical switch SW11 is zero.
The phase difference ΔΦ that can be provided by the phase adjustment area PA of the first optical switch SW21 at the second stage is zero.
The phase difference ΔΦ that can be provided by the phase adjustment area PA of the second optical switch SW22 in the second stage is −π / 4.

  The tree-type optical switch configuration 20 according to the first embodiment includes one control terminal CT1 regardless of the number of optical switches SW arranged. Each electrode terminal ET of each optical switch SW is supplied with a voltage from one control electronic circuit C1 via the control terminal CT1 and the electric wiring LE.

The control electronic circuit C1 selectively outputs any one of the control voltages V ₀ , V ₁ , V ₂ , V ₃ , and the output control voltage is common to the electrode terminals ET of the optical switches SW11, SW21, SW22. Is input. Thus, a phase difference can be given by performing phase modulation in the phase modulation region PM.
The voltage values of the control voltages V ₀ , V ₁ , V ₂ and V ₃ are set as follows.

(1) The voltage value of the control voltage V ₀ is 0 volts. For this reason, even if the control voltage V ₀ is input to the phase modulation region PM, no phase modulation occurs in the phase modulation region PM (a phase difference is not given in the phase modulation region PM).

(2) The voltage value of the control voltage V ₁ is a value that can give a phase difference of + π / 2 in the phase modulation region PM when a voltage is applied to the phase modulation region PM having a length L. Is set to
Accordingly, when the voltage is applied to the phase modulation region PM having a length of L / 2, the control voltage V ₁ can give a phase difference of + π / 4 in the phase modulation region PM.

(3) The voltage value of the control voltage V ₂ is set to a value that can give a phase difference of + π in the phase modulation region PM when a voltage is applied to the phase modulation region PM having a length L. Has been.
Therefore, when a voltage is applied to the phase modulation region PM having a length L / 2, the control voltage V ₂ can give a phase difference of + π / 2 in the phase modulation region PM.

(4) When the voltage value of the control voltage V ₃ is applied to the phase modulation region PM having a length L, the voltage value can be given a phase difference of + 3π / 2 in the phase modulation region PM. Is set.
Therefore, when the control voltage V ₃ is applied to the phase modulation region PM whose length is L / 2, a phase difference of + 3π / 4 can be imparted in the phase modulation region PM.

A general digital / analog converter circuit (DAC: Digital to Analog Converter) may be used as the control electronic circuit C1 that generates such a plurality of voltages. This electronic circuit (digital / analog conversion circuit) is a circuit that converts a multi-bit digital signal d logically generated from an IC circuit such as an FPGA (Field Programmable Gate Array) into an analog signal.
In the above case, it can be easily realized by converting a digital signal of at least 2 bits into an analog signal of 4 gradations.

  Next, the switching operation of the tree-type optical switch configuration 20 configured as described above will be described.

When the control voltage V ₀ is applied from the control electronic circuit C 1 to the phase modulation region PM of the first-stage optical switch SW 11, the phase difference between the arm optical waveguides A 1 and A 2 becomes 0, and when the control voltage V ₂ is applied, the arm optical waveguide The phase difference between A1 and A2 becomes + π, and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₁ is applied from the control electronic circuit C1 to the phase modulation region PM of the optical switch SW11, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2, and when the control voltage V ₃ is applied, the arm optical waveguide A1, The phase difference between A2 becomes + 3π / 2π, and the signal light P is output from the left output port (through port) O.
In the optical switch SW11, no phase difference is given in the phase adjustment area PA.
After all, the phase fluctuation due to the voltage application in the 1 × 2 optical switch SW11 becomes as shown in FIG.

In the second-stage first optical switch SW21, when the control voltages V = V ₁ and V ₃ , the signal light P is output from either output port O because the signal light P is not input to the optical switch SW21. There is no particular need to consider.
When the control voltage V ₀ is applied to the phase modulation region PM of the optical switch SW 21, the phase difference between the arm optical waveguides A 1 and A 2 becomes 0, and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₂ is applied to the phase modulation region PM of the optical switch SW21, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2, and the signal light P is output from the left output port (through port) O. .
In the optical switch SW21, no phase difference is given in the phase adjustment area PA.
Eventually, the phase fluctuation due to voltage application in the 1 × 2 optical switch SW21 is as shown in FIG.

In the second optical switch SW22 in the second stage, when the control voltages V = V ₀ and V _2, no signal light is input to the optical switch SW22, so that no signal light P is output from either output port O. There is no particular need to consider.
When the control voltage V ₁ is applied to the phase modulation region PM of the optical switch SW22, a phase difference of + π / 4 can be given to the signal light P in the phase modulation region PM. In addition, a phase difference of −π / 4 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes 0 (= + π / 4−π / 4), and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₃ is applied to the phase modulation region PM of the optical switch SW22, a phase difference of + 3π / 4 can be given to the signal light P in the phase modulation region PM. In addition, a phase difference of −π / 4 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2 (= + 3π / 4−π / 4), and the signal light P is output from the left output port (through port) O.
Eventually, the phase fluctuation due to voltage application in the 1 × 2 optical switch SW22 is as shown in FIG.

The above is summarized as shown in Table 1.

Therefore, the tree-type optical switch configuration 20 can perform the following switching operation.
(1) When the control voltage V ₀ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, the signal light P is output from the cross port of the first optical switch SW21 at the second stage.
(2) When the control voltage V ₁ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, the signal light P is output from the cross port of the second optical switch SW22 at the second stage.
(3) When the control voltage V ₂ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, the signal light P is output from the through port of the first optical switch SW21 at the second stage.
(4) When the control voltage V ₃ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, the signal light P is output from the through port of the second optical switch SW22 at the second stage.

As described above, there are four output ports O in the final stage of the tree-type optical switch configuration 20, but the tree-type optical switch configuration 20 only needs to have one control terminal C1. For this reason, the tree-type optical switch configuration 20 can simplify the electrical wiring LE and can be downsized.
Further, since only one control electronic circuit C1 needs to be connected to the tree-type optical switch configuration 20, the optical switch device including the tree-type optical switch configuration 20 and the control electronic circuit C1 can be reduced in size and power consumption. Can do.

[Example 2]
FIG. 4 is a configuration diagram showing a tree-type optical switch configuration 20A according to the second embodiment of the present invention.
The tree-type optical switch configuration 20A according to the second embodiment includes a 1 × 2 optical switch SW as a basic component, and is configured by connecting a total of seven optical switches SW in a tree shape in three stages. .

More specifically, in the tree-type optical switch configuration 20A, one optical switch SW11 is arranged at the first stage (the uppermost stage), two optical switches SW21 and SW22 are arranged at the second stage, and the third stage (the uppermost stage). In the lower part, four optical switches SW31, SW32, SW33, SW34 are arranged.
Each optical switch SW is arranged in such a direction that one input port I is located on the upper side and two output ports O are located on the lower side, and each optical switch SW is connected to each output port O of the upper optical switch. The upper and lower optical switches SW are connected by an optical waveguide LL so that the input port I of the lower optical switch is connected.

As each optical switch SW, a Mach-Zehnder (Mach-Zehnder) type optical phase modulator is used.
The MZ type optical phase modulator has the configuration shown in FIG. That is, the phase modulation region PM and the phase adjustment region PA are arranged in series in one arm optical waveguide A1 of the arm optical waveguides A1 and A2 having the same length, and on the phase modulation region PM, The electrode terminal ET is arranged.
The phase modulation region PM is formed as a region where a voltage can be applied to a part of one arm optical waveguide A1 of the arm optical waveguides A1 and A2 which are InP optical waveguides, and a reverse bias is applied to this portion. When a voltage is applied at, phase fluctuations occur along with absorption changes due to the FK effect.

In such an optical switch SW using an MZ type optical phase modulator, when the signal light P is input to the input port I, a voltage is supplied to the electrode terminal ET to perform phase modulation in the phase modulation region PM and to adjust the phase. By adjusting the phase in the area PA, the signal light P can be output from one of the two output ports O on the output side, that is, switching can be performed.
That is, if the phase difference (optical optical path length difference) between the two arm optical waveguides A1 and A2 is ± nπ, light is output from the opposite optical waveguide (cross port) to which the two arm optical waveguides A1 and A2 are input, and the two arm optical waveguides A1 , A2 has a phase difference of ± (2n + 1) π / 2, the light is output from the same optical waveguide (through port) as the optical input (where n is an integer).

Returning to FIG. 4, the description of the tree-type optical switch configuration 20A will be continued.
As described above, one arm optical waveguide A1 of the optical switches (MZ type optical phase modulators) SW11, SW21, SW22, SW31, SW32, SW33, SW34 is respectively provided with the phase modulation area PM and the phase adjustment area PA. Is formed.

In the second embodiment, the length of the phase adjustment region PM (the length along the light transmission direction) varies depending on the arrangement stage of the optical switch. Specifically, the settings are as follows.
The length of the phase adjustment region PM of the first optical switch SW11 at the first stage is a predetermined length L set in advance.
The length of the phase modulation area PM of the first and second optical switches SW21 and SW22 in the second stage is L / 2.
The length of the phase modulation area PM of the first, second, third, and fourth optical switches SW31, SW32, SW33, and SW34 in the third stage is L / 4.

In the second embodiment, the phase difference ΔΦ that can be given by adjusting the phase in the phase adjustment area PA is set as follows.
The phase difference ΔΦ that can be given by the phase adjustment area PA of the first-stage optical switch SW11 is zero.
The phase difference ΔΦ that can be provided by the phase adjustment area PA of the first optical switch SW21 at the second stage is zero.
The phase difference ΔΦ that can be provided by the phase adjustment area PA of the second optical switch SW22 in the second stage is −π / 4.
The phase difference ΔΦ that can be provided by the phase adjustment area PA of the first optical switch SW31 at the third stage is zero.
The phase difference ΔΦ that can be provided by the phase adjustment area PA of the second optical switch SW32 at the third stage is −2π / 8.
The phase difference ΔΦ that can be provided by the phase adjustment area PA of the third optical switch SW33 at the third stage is −π / 8.
The phase difference ΔΦ that can be provided by the phase adjustment area PA of the fourth optical switch SW34 at the third stage is −3π / 8.

  The tree-type optical switch configuration 20A according to the second embodiment includes one control terminal CT1 regardless of the number of optical switches SW arranged. Each electrode terminal ET of each optical switch SW is supplied with a voltage from one control electronic circuit C1 via the control terminal CT1 and the electric wiring LE.

The control electronic circuit C1 selectively outputs any one of the control voltages V ₀ , V ₁ , V ₂ , V ₃ , V ₄ , V ₅ , V ₆ , V ₇ , and the output control voltage is an optical switch. The signal is commonly input to the electrode terminals ET of SW11, SW21, SW22, SW31, SW32, SW33, and SW34. Thus, a phase difference can be given by performing phase modulation in the phase modulation region PM.
The voltage values of the control voltages V ₀ , V ₁ , V ₂ , V ₃ , V ₄ , V ₅ , V ₆ and V ₇ are set as follows.

(1) The voltage value of the control voltage V ₀ is 0 volts. For this reason, even if the control voltage V ₀ is input to the phase modulation region PM, no phase modulation occurs in the phase modulation region PM (a phase difference is not given in the phase modulation region PM).

(2) The voltage value of the control voltage V ₁ is a value that can give a phase difference of + π / 2 in the phase modulation region PM when a voltage is applied to the phase modulation region PM having a length L. Is set to
Accordingly, when the voltage is applied to the phase modulation region PM having a length of L / 2, the control voltage V ₁ can give a phase difference of + π / 4 in the phase modulation region PM.
Further, when a voltage is applied to the phase modulation region PM having a length of L / 4, the control voltage V ₁ can provide a phase difference of + π / 8 in the phase modulation region PM.

(3) The voltage value of the control voltage V ₂ is set to a value that can give a phase difference of + π in the phase modulation region PM when a voltage is applied to the phase modulation region PM having a length L. Has been.
Therefore, when a voltage is applied to the phase modulation region PM having a length L / 2, the control voltage V ₂ can give a phase difference of + π / 2 in the phase modulation region PM.
Further, when a voltage is applied to the phase modulation region PM having a length of L / 4, the control voltage V ₂ can give a phase difference of + π / 4 in the phase modulation region PM.

(4) When the voltage value of the control voltage V ₃ is applied to the phase modulation region PM having a length L, the voltage value can be given a phase difference of + 3π / 2 in the phase modulation region PM. Is set.
Therefore, when the control voltage V ₃ is applied to the phase modulation region PM whose length is L / 2, a phase difference of + 3π / 4 can be imparted in the phase modulation region PM.
Further, when a voltage is applied to the phase modulation region PM having a length of L / 4, the control voltage V ₃ can give a phase difference of + 3π / 8 in the phase modulation region PM.

(5) When the voltage value of the control voltage V ₄ is applied to the phase modulation region PM having a length L, the voltage value is set to a value that can give a phase difference of + 2π in the phase modulation region PM. ing.
Therefore, when the control voltage V ₄ is applied to the phase modulation region PM whose length is L / 2, a phase difference of + π can be imparted in the phase modulation region PM.
Further, when a voltage is applied to the phase modulation region PM having a length of L / 4, the control voltage V ₄ can provide a phase difference of + π / 2 in the phase modulation region PM.

(6) When the voltage value of the control voltage V ₅ is applied to the phase modulation region PM whose length is L, the voltage value of the control voltage V ₅ can be given a phase difference of + 5π / 2 in the phase modulation region PM. Is set.
Therefore, when the control voltage V ₅ is applied to the phase modulation region PM having a length of L / 2, a phase difference of + 5π / 4 can be given in the phase modulation region PM.
Further, when a voltage is applied to the phase modulation region PM having a length of L / 4, the control voltage V ₅ can provide a phase difference of + 5π / 8 in the phase modulation region PM.

(7) When the voltage value of the control voltage V ₆ is applied to the phase modulation region PM having a length L, the voltage value is set to a value that can give a phase difference of + 3π in the phase modulation region PM. ing.
Therefore, when the control voltage V ₆ is applied to the phase modulation region PM whose length is L / 2, a phase difference of + 3π / 2 can be given in the phase modulation region PM.
Further, when a voltage is applied to the phase modulation region PM having a length of L / 4, the control voltage V ₆ can give a phase difference of + 3π / 4 in the phase modulation region PM.

(8) When the voltage value of the control voltage V ₇ is applied to the phase modulation region PM whose length is L, the voltage value of the control voltage V ₇ is a value that can give a phase difference of + 7π / 2 in the phase modulation region PM. Is set.
Therefore, when the control voltage V ₇ is applied to the phase modulation region PM whose length is L / 2, a phase difference of + 7π / 4 can be given in the phase modulation region PM.
Further, when a voltage is applied to the phase modulation region PM having a length of L / 4, the control voltage V ₇ can give a phase difference of + 7π / 8 in the phase modulation region PM.

A general digital / analog converter circuit (DAC: Digital to Analog Converter) may be used as the control electronic circuit C1 that generates such a plurality of voltages. This electronic circuit (digital / analog conversion circuit) is a circuit that converts a multi-bit digital signal d logically generated from an IC circuit such as an FPGA (Field Programmable Gate Array) into an analog signal.
In the above case, it can be easily realized by converting a digital signal of at least 2 bits into an analog signal of 8 gradations.

  Next, the switching operation of the tree-type optical switch configuration 20A configured as described above will be described.

When the control voltage V ₀ is applied from the control electronic circuit C 1 to the phase modulation region PM of the first-stage optical switch SW 11, the phase difference between the arm optical waveguides A 1 and A 2 becomes 0, and when the control voltage V ₂ is applied, the arm optical waveguide The phase difference between A1 and A2 is + π, and when the control voltage V ₄ is applied, the phase difference between the arm optical waveguides A1 and A2 is + 2π, and when the control voltage V ₆ is applied, the phase difference between the arm optical waveguides A1 and A2 is The signal light P is output from the right output port (cross port) O.
When the control voltage V ₁ is applied from the control electronic circuit C1 to the phase modulation region PM of the optical switch SW11, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2, and when the control voltage V ₃ is applied, the arm optical waveguide A1, phase difference between A2 is + 3 [pi] / 2 [pi, and the control voltage arm optical waveguides A1 by applying a V _5, the phase difference between A2 is + 5 [pi] / 2 [pi next, position between the control voltage is applied to V ₇ arm optical waveguides A1, A2 The phase difference becomes + 7π / 2π, and the signal light P is output from the left output port (through port) O.
In the optical switch SW11, no phase difference is given in the phase adjustment area PA.

In the first optical switch SW21 in the second stage, when the control voltages V = V ₁ , V ₃ , V ₅ , and V ₇ , the signal light P is not input to the optical switch SW 21, and therefore, from either output port O. The signal light P is not output, and there is no need to consider it in particular.
When the control voltage V ₀ is applied to the phase modulation region PM of the optical switch SW 21, the phase difference between the arm optical waveguides A 1 and A 2 becomes 0, and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₂ is applied to the phase modulation region PM of the optical switch SW21, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2, and the signal light P is output from the left output port (through port) O. .
When the control voltage V ₄ is applied to the phase modulation region PM of the optical switch SW 21, the phase difference between the arm optical waveguides A 1 and A 2 becomes π, and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₆ is applied to the phase modulation region PM of the optical switch SW21, the phase difference between the arm optical waveguides A1 and A2 becomes + 3π / 2, and the signal light P is output from the left output port (through port) O. .
In the optical switch SW21, no phase difference is given in the phase adjustment area PA.

In the second optical switch SW22 in the second stage, when the control voltage V = V ₀ , V ₂ , V ₄ , V _6, no signal light is input to the optical switch SW 22, so that the signal is output from either output port O. The light P is not output and there is no need to consider it in particular.
When the control voltage V ₁ is applied to the phase modulation region PM of the optical switch SW22, a phase difference of + π / 4 can be given to the signal light P in the phase modulation region PM. In addition, a phase difference of −π / 4 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes 0 (= + π / 4−π / 4), and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₃ is applied to the phase modulation region PM of the optical switch SW22, a phase difference of + 3π / 4 can be given to the signal light P in the phase modulation region PM. In addition, a phase difference of −π / 4 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2 (= + 3π / 4−π / 4), and the signal light P is output from the left output port (through port) O.
When the control voltage V ₅ is applied to the phase modulation region PM of the optical switch SW22, a phase difference of + 5π / 4 can be imparted to the signal light P in the phase modulation region PM. In addition, a phase difference of −π / 4 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes π (= + 5π / 4−π / 4), and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₇ is applied to the phase modulation region PM of the optical switch SW22, a phase difference of + 7π / 4 can be given to the signal light P in the phase modulation region PM. In addition, a phase difference of −π / 4 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes + 3π / 2 (= + 7π / 4−π / 4), and the signal light P is output from the left output port (through port) O.

In the first optical switch SW31 at the third stage, when the control voltages V = V ₁ , V ₂ , V ₃ , V ₅ , V ₆ , V ₇ , the signal light P is not input to the optical switch SW 31. The signal light P is not output from the output port O, and there is no need to consider it in particular.
When the control voltage V ₀ is applied to the phase modulation region PM of the optical switch SW 31, the phase difference between the arm optical waveguides A 1 and A 2 becomes 0, and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₄ is applied to the phase modulation region PM of the optical switch SW31, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2, and the signal light P is output from the left output port (through port) O. .

In the second optical switch SW32 in the third stage, when the control voltages V = V ₀ , V ₁ , V ₃ , V ₄ , V ₅ , V _7, no signal light is input to the optical switch SW 32. The signal light P is not output from the output port O, and there is no need to consider it in particular.
When the control voltage V ₂ is applied to the phase modulation region PM of the optical switch SW32, a phase difference of + π / 4 can be given to the signal light P in the phase modulation region PM. In addition, a phase difference of −2π / 8 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes 0 (= + π / 4−2π / 8), and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₆ is applied to the phase modulation region PM of the optical switch SW32, a phase difference of + 3π / 4 can be imparted to the signal light P in the phase modulation region PM. In addition, a phase difference of −2π / 8 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2 (= + 3π / 4−2π / 8), and the signal light P is output from the left output port (through port) O.

In the third optical switch SW33 at the third stage, when the control voltages V = V ₀ , V ₂ , V ₃ , V ₄ , V ₆ , V _7, no signal light is input to the optical switch SW 33. The signal light P is not output from the output port O, and there is no need to consider it in particular.
When the control voltage V ₁ is applied to the phase modulation region PM of the optical switch SW33, a phase difference of + π / 8 can be given to the signal light P in the phase modulation region PM. In addition, a phase difference of −π / 8 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes 0 (= + π / 8−π / 8), and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₅ is applied to the phase modulation region PM of the optical switch SW33, a phase difference of + 5π / 8 can be given to the signal light P in the phase modulation region PM. In addition, a phase difference of −π / 8 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2 (= + 5π / 8−π / 8), and the signal light P is output from the left output port (through port) O.

In the fourth optical switch SW34 in the third stage, when the control voltages V = V ₀ , V ₁ , V ₂ , V ₄ , V ₅ , V ₆ , no signal light is input to the optical switch SW 34. The signal light P is not output from the output port O, and there is no need to consider it in particular.
When the control voltage V ₃ is applied to the phase modulation region PM of the optical switch SW34, a phase difference of + 3π / 8 can be given to the signal light P in the phase modulation region PM. Further, a phase difference of −3π / 8 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes 0 (= + 3π / 8-3π / 8), and the signal light P is output from the right output port (cross port) O.
When the control voltage V ₇ is applied to the phase modulation region PM of the optical switch SW 34, a phase difference of + 7π / 8 can be given to the signal light P in the phase modulation region PM. Further, a phase difference of −3π / 8 is given to the signal light P in the phase adjustment area PA. As a result, the phase difference between the arm optical waveguides A1 and A2 becomes + π / 2 (= + 7π / 8-3π / 8), and the signal light P is output from the left output port (through port) O.

The above is summarized as shown in Table 2. In Table 2, a blank column represents an optical switch to which no signal light is input.

Therefore, the tree-type optical switch configuration 20A can perform the following switching operation.
(1) When the control voltage V ₀ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, SW31, SW32, SW33, and SW34, the signal light P is transmitted from the cross port of the first optical switch SW31 at the third stage. Is output.
(2) When the control voltage V ₁ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, SW31, SW32, SW33, and SW34, the signal light P is transmitted from the cross port of the third optical switch SW33 in the third stage. Is output.
(3) When the control voltage V ₂ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, SW31, SW32, SW33, and SW34, the signal light P is transmitted from the cross port of the second optical switch SW31 at the third stage. Is output.
(4) When the control voltage V ₃ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, SW31, SW32, SW33, and SW34, the signal light P is transmitted from the cross port of the fourth optical switch SW34 at the third stage. Is output.
(5) When the control voltage V ₄ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, SW31, SW32, SW33, and SW34, the signal light P is output from the through port of the first optical switch SW31 at the third stage. Is output.
(6) When the control voltage V ₅ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, SW31, SW32, SW33, and SW34, the signal light P is output from the through port of the third optical switch SW33 at the third stage. Is output.
(7) When the control voltage V ₆ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, SW31, SW32, SW33, and SW34, the signal light P is transmitted from the through port of the second optical switch SW31 at the third stage. Is output.
(8) When the control voltage V ₇ is input to the electrode terminals ET of the optical switches SW11, SW21, SW22, SW31, SW32, SW33, SW34, the signal light P is output from the through port of the fourth optical switch SW34 at the third stage. Is output.

As described above, the output port O at the final stage of the tree-type optical switch configuration 20A has eight, but the tree-type optical switch configuration 20A only needs to have one control terminal C1. For this reason, the tree-type optical switch configuration 20A can simplify the electrical wiring LE and can be downsized.
Further, since only one control electronic circuit C1 needs to be connected to the tree-type optical switch configuration 20A, the optical switch device composed of the tree-type optical switch configuration 20A and the control electronic circuit C1 can be reduced in size and power consumption. Can do.

[Modifications, etc.]
The present invention is not limited to the above-described 1 × 4 tree-type optical switch configuration (Example 1) and 1 × 8 tree-type optical switch configuration (Example 2), but also 1 × 16, 1 × 32, and 1 ×. It is possible to cope with a multi-port configuration such as a 2 ^M tree type optical switch configuration (where M is an integer of 2 or more).

In the 1 × 2 ^M tree type optical switch configuration, the following settings are made.
(1) The length of the phase modulation region PM formed in the first-stage optical switch SW of the optical switches SW is a preset length L, and is formed in the second-stage and subsequent optical switches SW. The length of the phase modulation region PM is half the length of the phase modulation region PM formed in the optical switch on the upper stage side by one stage with respect to the optical switch SW of the stage.
(2) In the first stage, the phase difference provided by the phase adjustment area PA of the optical switch SW is zero.
(3) In the second and subsequent stages, the phase difference provided by the phase adjustment area PA of the optical switch SW is − (π / 2 ^M ) × Q (where Q is a number increasing from 0 to 1, The value is any one of 2 ^(M-1) -1.

Among the above setting conditions, “the phase difference given by the phase adjustment area PA of the optical switch SW is − (π / 2 ^M ) × Q (where Q is a number that increases by 1 from 0. The maximum value is any one of 2 ^(M−1) −1) ”.
Q is 1 when M = 2. Therefore, the phase difference Δφ is − (π / 2 ² ) × 1 = −π / 4.
When M = 3, Q is 1, 2, 3. Therefore, the phase difference Δφ is − (π / 2 ³ ) × 1 = −π / 8, − (π / 2 ³ ) × 2 = −2π / 8, − (π / 2 ³ ) × 3 = −3π / 8

The control voltages are ^2M types of control voltages V0, V1, V2,... V2 ^M −1 having different voltage values. The value of the control voltage is set as follows.
The current value of the control voltage V0 is 0, and the current value of the control voltage V1 is a value that can give a phase difference of + π / 2 to the signal light when input to the first-stage phase modulation region, Thereafter, as the control voltages V2, V3,..., V2 ^M −1, the phase difference imparted to the signal light when it is input to the first-stage phase modulation region becomes + π / 2 sequentially, + π / 2. Increase the value gradually.

The number of phase modulations required is increased by increasing the number of ports. In this case, the increase in applied voltage is suppressed, and instead, the phase modulation region can be lengthened to cope with it.
In addition, it is necessary to supply a multi-value control voltage with high accuracy, but considering the number of bits (8-16 bits) of a general digital / analog converter circuit (DAC), a major problem is about 1 × 128. Don't be.

In addition to the method of increasing the number of ports of the basic configuration by multi-leveling the control voltage of the DAC as described above, the number of ports of the basic configuration is 1 × 4 or 1 × 8, which is easy to manufacture. A multi-stage configuration may be used to increase the number of ports.
In this case, although the required number of DACs increases, the number of control terminals and the number of control electric circuits can be greatly reduced as compared with the conventional example. For example, a 1 × 64 optical switch can be composed of 21 1 × 4 optical switches, and the number of control terminals is 21.
On the other hand, since the configuration of the conventional example requires 63 control terminals, it can be reduced to 1/3. It can also be configured with seven 1 × 8 optical switches, and the number of control terminals is seven, which can be reduced to 1/9.

  Further, in the first and second embodiments, the control voltage is input from the control electronic circuit C to the tree-type optical switch configuration. However, the control voltage is formed in an InP-based optical waveguide that changes the refractive index using the plasma effect by current injection. When the phase modulation region PM formed in a glass-based optical waveguide that changes the refractive index using the TO (Thermo-Optic) effect by supplying current to the heater (electrode terminal) is adopted. Is supplied with a control current instead of a control voltage.

The control current is 2 ^M types of control currents I0, I1, I2,... I2 ^M −1 having different current values. The value of the control current is set as follows.
The current value of the control current I0 is 0, and the current value of the control current I1 is a value that can give a phase difference of + π / 2 to the signal light when input to the first-stage phase modulation region, Thereafter, as the control currents I2, I3,..., I2 ^M −1, the phase difference imparted to the signal light when it is input to the first-stage phase modulation region is sequentially increased to + π / 2, and then + π / 2. Increase the value gradually.

The present invention can be applied to a 1 × 2 ^M tree-type optical switch configuration using a Machender optical modulator that performs switching by voltage application or current input as a basic component.

10, 10A, 20, 20A Tree-type optical switch configuration SW, SW11, SW21, SW22, SW31, SW32, SW33, SW34 Optical switch I Input port O Output port Y1, Y2 Directional coupler A1, A2 Arm optical waveguide PM Phase Modulation area PA Phase adjustment area ET Electrode terminal CT, CT1 to CT7 Control terminal LL Optical waveguide LE Electrical wiring C, C1 to C7 Control electronics

Claims (3)

2 ^M −1 (where M is an integer equal to or greater than 2) Mach-Zehnder type optical switches connected in M stages, a tree type optical switch configuration having 2 ^M output ports,
A phase modulation region that is formed in one arm optical waveguide of each of the optical switches, performs a phase modulation operation by inputting a voltage or a current, and gives a phase difference of + phase to the signal light;
Formed in one arm optical waveguide of each of the optical switches, and a phase adjustment region that gives a phase difference of -phase to the signal light;
An electrode terminal disposed on the phase modulation region;
One control terminal,
The control terminal and each of the electrode terminals are connected, and electrical wiring that sends a voltage or current input to the control terminal to the electrode terminal;
Have
Of the optical switches, the length of the phase modulation region formed in the first-stage optical switch is a preset length, and the length of the phase modulation region formed in the second-stage and subsequent optical switches is The length is half of the length of the phase modulation region formed in the optical switch on the upper stage side by one stage with respect to the optical switch of the stage,
In the first stage, the phase difference provided by the phase adjustment region of the optical switch is 0,
In the second and subsequent stages, the phase difference provided by the phase adjustment region of the optical switch is − (π / 2 ^M ) × Q (where Q is a number increasing from 0 by 1, and the maximum value is 2 ^{( M-1)} is a tree type optical switch configuration. In claim 1,
A control voltage that causes a phase modulation operation in the phase modulation region is input to the control terminal,
The control voltages are ^2M types of control voltages V0, V1, V2,... V2 ^{M having} different voltage values.
−1, the voltage value of the control voltage V0 is 0, and the voltage value of the control voltage V1 gives a phase difference of + π / 2 to the signal light when input to the phase modulation area of the first stage. After that, as the control voltages V2,... V2 ^M −1, the phase difference given to the signal light becomes + π / 2 when input to the first phase modulation region. A tree-type optical switch configuration characterized by a value that increases sequentially by + π / 2. In claim 1,
A control current that causes a phase modulation operation in the phase modulation region is input to the control terminal,
The control current is 2 ^M types of control currents I0, I1, I2,... I2 ^M −1 having different current values, the current value of the control current I0 is 0, and the current value of the control current I1 is the first current value. It is a value that can give a phase difference of + π / 2 to the signal light when it is input to the first-stage phase modulation region, and thereafter, as the control currents I2,... I2 ^M −1, A tree-type optical switch configuration characterized in that the phase difference given to the signal light when it is input to the phase modulation area of the stage is a value that increases by + π / 2 sequentially to + π / 2.

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