JP2008046448A - Micromirror device and optical switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control power of output light to an optimum value. <P>SOLUTION: An optical switch is provided with: micromirror devices 3a and 3b which deflect and make input light emitted from an input port 1a selectively incident on an arbitrary output port 1b; an output light detector 4 for detecting power of the output light incident on the output port 1b; and a control device 5 for controlling the micromirror devices 3a and 3b to connect the arbitrary input port 1a and the output port 1b. Each of micromirror devices 3a and 3b has a rotatably supported mirror and a plurality of electrodes arranged apart from the mirror. The control device 5 generates a common bias voltage to each voltage of the micromirror device on an optical path between the input port 1a and the output port 1b to be connected so that the power of the output light is the optimum value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a micromirror device including a mirror having a variable tilt angle and an optical switch using a plurality of micromirror devices.

As one technique for realizing an optical switch, a technique using a micromirror has been proposed (see, for example, Non-Patent Document 1).
FIG. 4 is a perspective view showing a configuration example of a conventional optical switch. In FIG. 4, 1a is an input port, 1b is an output port, 2a is an input side micromirror array, and 2b is an output side micromirror array. The input port 1a and the output port 1b are each composed of a plurality of optical fibers arranged two-dimensionally, and the micromirror arrays 2a and 2b are each composed of a plurality of micromirror devices 3a and 3b arranged two-dimensionally. . The arrows in FIG. 4 indicate the traveling direction of the light beam.

  An optical signal emitted from a certain input port 1a is reflected and deflected by the micromirror device 3a of the input side micromirror array 2a corresponding to the input port 1a. Since the mirror of the micromirror device 3a can rotate around two axes, the reflected light of the micromirror device 3a can be directed to any micromirror device 3b of the output side micromirror array 2b. Similarly, since the mirror of the micromirror device 3b can be rotated about two axes, the reflected light of the micromirror device 3b can be directed to the corresponding output port 1b by appropriately controlling the tilt angle of the mirror. Accordingly, by appropriately controlling the tilt angles of the mirrors of the input side micromirror array 2a and the output side micromirror array 2b, a connection between any two-dimensionally arranged input port 1a and output port 1b is made. The optical path can be switched.

  The most characteristic components of the optical switch are the micromirror arrays 2a and 2b. Non-patent literature 1 discloses, for example, micromirror devices 3a and 3b constituting the micromirror arrays 2a and 2b. FIG. 5 is an exploded perspective view showing the configuration of the micromirror device disclosed in Non-Patent Document 1, and FIG. 6 is a cross-sectional view of the micromirror device of FIG. The micromirror device has a structure in which a mirror substrate 200 on which a mirror is formed and an electrode substrate 300 on which an electrode is formed are arranged in parallel.

  The mirror substrate 200 includes a plate-shaped frame portion 210, a movable frame 220 disposed in the opening of the frame portion 210, and a mirror 230 disposed in the opening of the movable frame 220. The frame part 210, the torsion springs 211a, 211b, 221a, 221b, the movable frame 220, and the mirror 230 are integrally formed of, for example, single crystal silicon. For example, three Ti / Pt / Au layers are formed on the surface of the mirror 230. The pair of torsion springs 211 a and 211 b connect the frame part 210 and the movable frame 220. The movable frame 220 can rotate about the movable frame rotation axis x of FIG. 5 passing through the pair of torsion springs 211a and 211b. Similarly, the pair of torsion springs 221 a and 221 b couple the movable frame 220 and the mirror 230. The mirror 230 can rotate about the mirror rotation axis y of FIG. 5 passing through the pair of torsion springs 221a and 221b. The movable frame rotation axis x and the mirror rotation axis y are orthogonal to each other. As a result, the mirror 230 rotates about two orthogonal axes.

  The electrode substrate 300 has a plate-like base portion 310 and a terrace-like protruding portion 320. The base 310 and the protrusion 320 are made of, for example, single crystal silicon. The protrusion 320 includes a second terrace 322 having a truncated pyramid shape formed on the upper surface of the base 310, a first terrace 321 having a truncated pyramid shape formed on the upper surface of the second terrace 322, and the first terrace. And a pivot 330 having a columnar shape formed on the upper surface of 321. Four electrodes 340 a to 340 d are formed on the four corners of the protruding portion 320 and the upper surface of the base portion 310 following the four corners. In addition, a pair of convex portions 360 a and 360 b arranged side by side so as to sandwich the protruding portion 320 is formed on the upper surface of the base portion 310. Further, a wiring 370 is formed on the upper surface of the base 310, and electrodes 340a to 340d are connected to the wiring 370 via lead lines 341a to 341d. An insulating layer 311 made of silicon oxide or the like is formed on the surface of the base 310, and electrodes 340a to 340d, lead lines 341a to 341d, and wirings 370 are formed on the insulating layer 311.

  The mirror substrate 200 and the electrode substrate 300 as described above are formed by joining the lower surface of the frame portion 210 and the upper surfaces of the convex portions 360a and 360b so that the mirror 230 and the electrodes 340a to 340d are opposed to each other. A micromirror device as shown in FIG. 6 is configured. In such a micromirror device, the mirror 230 is grounded, a positive driving voltage is applied to the electrodes 340a to 340d, and an asymmetric potential difference is generated between the electrodes 340a to 340d, thereby causing the electrostatic attraction force of the mirror 230. And the mirror 230 can be rotated in an arbitrary direction.

T. Yamamoto, et al., “A Three-Dimensional MEMS Optical Switching Module Having 100 Input and 100 Output Ports”, Photonics Technology Letters, IEEE, Vol.15, No.10, p.1360-1362

  In a conventional optical switch, a control device that controls the micromirror devices 3a and 3b supplies a driving voltage to the micromirror devices 3a and 3b when the function of a VOA (Variabie Optical Attenuator) that controls optical power is realized. 230 is perturbed (vibrated), the correlation between the drive voltage and the output light power is obtained, and the optimum drive voltage (for example, the drive at which the output light power is at the optimum value) can be obtained. In general, the voltage is determined. Therefore, the conventional optical switch controls the power of the output light incident on the output port 1b by the angle of the mirror 230 of the micromirror devices 3a and 3b.

  However, in the conventional optical switch, the power loss of the output light becomes large, and in some cases, there is a possibility that the power of the output light cannot be controlled to the optimum value. The reason is that the conventional optical switch controls the power of the output light exclusively by controlling the angle of the mirror 230, and the focus is not controlled and the light is defocused at the output port 1b. This is because the power of the output light may change rapidly with respect to the angle change of the mirror 230.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a micromirror device and an optical switch that can control the power of output light to an optimum value.

The micromirror device of the present invention includes a mirror that is rotatably supported, a plurality of electrodes that are spaced apart from the mirror, and an output light detection device that detects the power of output light that is reflected light from the mirror. And a control device that generates and applies a common bias voltage to each electrode so that the power of the output light becomes an optimum value.
Further, in one configuration example of the micromirror device of the present invention, the control device includes a drive voltage generating unit that generates a drive voltage corresponding to a desired tilt angle of the mirror for each electrode, and the power of the output light is A bias voltage generating means for generating the bias voltage so as to obtain an optimum value, and an adding means for adding the bias voltage and the drive voltage for each electrode and applying the added voltage to the corresponding electrode; It is what has.

In addition, the optical switch of the present invention independently provides one or more input ports for inputting input light, one or more output ports for outputting output light, and one or more input lights emitted from the input port. One or more micromirror devices that deflect and selectively enter any output port; an output light detection device that detects the power of output light incident on the output port; and any input port and output A control device for controlling the micromirror device to connect between the ports, each micromirror device comprising a mirror that is rotatably supported, and a plurality of electrodes that are spaced apart from the mirror. The control device has a bias voltage common to each electrode of the micromirror device on the optical path between the input port to be connected and the output port to be connected to the output light. Chromatography is used to apply generated so that the optimum value.
In one configuration example of the optical switch of the present invention, the control device generates a drive voltage corresponding to a desired tilt angle of a mirror of the micromirror device on the optical path for each electrode of the micromirror device. A drive voltage generating means; a bias voltage generating means for generating the bias voltage so that the power of the output light becomes an optimum value; and adding the bias voltage and the drive voltage for each electrode. Addition means for applying a voltage to the corresponding electrode of the micromirror device on the optical path.

  According to the present invention, a common bias voltage is generated and applied to each electrode of the micromirror device so that the power of the output light, which is the reflected light of the mirror, becomes an optimum value. And a sudden change in the power of the output light can be suppressed. As a result, it is possible to realize a micromirror device capable of controlling the optical power more appropriately than in the past.

  In the present invention, a common bias voltage is applied to each electrode of the micromirror device on the optical path between the input port to be connected and the output port so that the power of the output light incident on the output port becomes an optimum value. By generating and applying the voltage to the light source, the focus of the output light can be controlled, and a sudden change in the power of the output light can be suppressed. As a result, it is possible to realize an optical switch capable of controlling optical power more appropriately than in the past. Further, according to the present invention, it is possible to reduce the possibility of the problem that the output light power cannot be controlled to the optimum value as in the conventional optical switch.

[First Embodiment]
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the optical switch according to the first embodiment of the present invention. The same components as those in FIG. 4 are denoted by the same reference numerals. In FIG. 1, 4 is an output light detection device, and 5 is a control device. Since the mechanical configuration of each of the input-side micromirror device 3a and the output-side micromirror device 3b is the same as that of the prior art, description will be made using the reference numerals in FIGS.

The input light emitted from the input port 1a is reflected by the respective mirrors of the input-side micromirror device 3a and the output-side micromirror device 3b and enters the output port 1b.
The output light detection device 4 is provided for each output port 1b. Each output light detection device 4 detects the power of the output light incident on the corresponding output port 1b.
The control device 5 generates a voltage to be applied to the micromirror devices 3a and 3b so that the output light power has an optimum value.

  The major difference between the present embodiment and the conventional optical switch is that in the conventional optical switch, the driving voltage for controlling the mirror 230 of each micromirror device 3a, 3b to a desired angle is different from that of the micromirror device 3a, 3b. In contrast to application to the electrodes 340a to 340d, in the present embodiment, application to the electrodes 340a to 340d is performed by a combination (addition / subtraction) of a bias voltage common to the electrodes 340a to 340d and a drive voltage for each electrode. The voltage is determined, and the bias voltage is changed in accordance with the output light power.

Hereinafter, differences between the present embodiment and the conventional optical switch will be described in more detail. FIG. 2 is a block diagram illustrating a configuration example of the control device 5. In the example of FIG. 2, only one micromirror device is described.
The mirror voltage application means 500 of the control device 5 is provided for each micromirror device. Each mirror voltage application unit 500 applies a ground potential to the mirror 230 via the frame part 210, the torsion springs 211a and 211b, the movable frame 220, and the torsion springs 221a and 221b of the corresponding micromirror device.

  The control means 501 recognizes which input port 1a and output port 1b should be connected. As described above, in order to connect between the arbitrary input port 1a and the output port 1b, the input side micromirror device 3a corresponding to the input port 1a and the output side micromirror device 3b corresponding to the output port 1b, respectively. It is necessary to control the tilt angle of the mirror 230 to an appropriate value. Therefore, the control unit 501 generates the target value Axref of the inclination angle of the mirror 230 around the rotation axis x and the target value Ayref of the inclination angle of the mirror 230 around the rotation axis y shown in FIG. 5 for each micromirror device. And output. Further, the control unit 501 generates and outputs a target value (optimum value) Pref of the output light power for each micromirror device in order to optimize the power of the output light incident on the output port 1b.

  The drive voltage generation unit 502 is provided for each micromirror device. Each drive voltage generation unit 502 generates a drive voltage for each of the electrodes 340a to 340d of the corresponding micromirror device according to the target values Axref and Ayref of the inclination angle of the mirror 230 of the corresponding micromirror device. As shown in FIG. 2, each drive voltage generation unit 502 includes subtraction units 505 and 506 and an angle controller 507.

The subtracting means 505 subtracts the tilt angle Ax of the mirror 230 around the rotation axis x detected by a sensor (not shown) from the target value Axref of the tilt angle of the mirror 230, and the subtracting means 506 is the target of the tilt angle of the mirror 230. The inclination angle Ay of the mirror 230 around the rotation axis y detected by a sensor (not shown) is subtracted from the value Ayref.
In order to detect the tilt angles Ax and Ay of the mirror 230, a sensor electrode is provided on the insulating layer 311 of the base 310 of the micromirror device separately from the electrodes 340a to 340d so as to face the mirror 230. What is necessary is just to detect the electrostatic capacitance according to the distance of the mirror 230 and sensor electrode which change according to the inclination angle of 230.

The angle controller 507 adjusts the tilt angle Ax of the mirror 230 to the target value Axref and the tilt angle Ay of the mirror 230 to the target value Ayref (that is, the outputs of the subtracting means 505 and 506 become zero). ), A driving voltage is generated for each of the electrodes 340a to 340d.
In the present embodiment, the rotation axes x and y and the dividing lines of the electrodes 340a to 340d are arranged so as to intersect at 45 degrees, so that the rotation of the mirror 230 around the rotation axis x is related. The electrodes to be operated are 340a and 340c, and the electrodes related to the rotation of the mirror 230 around the rotation axis y are 340b and 340d. Therefore, the drive voltage to the electrodes 340a and 340c is generated so that the output of the subtracting means 505 becomes zero, and the drive voltage to the electrodes 340b and 340d is generated so that the output of the subtracting means 506 becomes zero. Thus, the tilt angle of the mirror 230 is controlled to a desired value.

  Next, the bias voltage generation means 503 is provided for each micromirror device. Each bias voltage generation unit 503 generates a bias voltage Vb common to the electrodes 340a to 340d of the corresponding micromirror device according to the target value Pref of the output light power. As described above, the control unit 501 outputs the target value Pref of the output light power to the micromirror devices 3a and 3b on the optical path between the input port 1a and the output port 1b to be connected. As shown in FIG. 2, each bias voltage generation unit 503 includes a subtraction unit 508 and an optical power controller 509.

The subtracting unit 508 subtracts the power value P of the output light detected by the output light detection device 4 of the output port 1b to which the output light should enter from the target value Pref of the power of the output light.
The optical power controller 509 generates the bias voltage Vb so that the power P of the output light coincides with the target value Pref (that is, the output of the subtracting means 508 becomes zero).

  When the bias voltage Vb common to the electrodes 340a to 340d is changed, the distance between the mirror 230 and the electrodes 340a to 340d (the vertical position of the mirror 230 shown in FIG. 6) changes. The change in the vertical position of the mirror 230 of the micromirror devices 3a and 3b on the optical path between the input port 1a and the output port 1b changes the optical path length between the input port 1a and the output port 1b. It means to do. Therefore, by adjusting the bias voltage Vb, it is possible to control the focus of the output light, and it is possible to avoid a sudden change in the loss of light due to defocusing or light defocusing at the output port 1b.

  The adding means 504a to 504d add the bias voltage Vb common to each electrode and the driving voltage for each electrode generated by the driving voltage generating means 502, and apply the added voltage to the corresponding electrodes 340a to 340d. .

  In the present embodiment, the angle of the mirror 230 of the micromirror devices 3a and 3b is controlled as in the conventional case, and at the same time, the bias voltage Vb is controlled so that the power of the output light becomes an optimum value, thereby focusing the output light. Therefore, a rapid change in the output light power can be suppressed as compared with the conventional optical switch, and more appropriate optical power control can be realized. Further, it is possible to reduce the possibility of the problem that the output light power cannot be controlled to the optimum value as in the conventional optical switch.

  In the example shown in FIG. 2, a sensor for detecting the tilt angles Ax and Ay of the mirror 230 is required for each micromirror device, but the tilt angle of the mirror 230 can be controlled without using the sensor. In this case, the angle controller 507 is provided with a table in which the relationship between the tilt angle of the mirror 230 and the drive voltage value is set in advance. The angle controller 507 may acquire the drive voltage value corresponding to the target values Axref and Ayref of the tilt angle of the mirror 230 from the table and generate the drive voltage.

  There are the following two methods for setting the target value (optimum value) Pref of the output light power. When the focus of the output light is controlled, the power of the output light varies depending on the position of the focus, and takes a maximum value at a certain focus position. One method of setting the optimum value Pref is a method in which this known maximum value is set to Pref. The other method is a method corresponding to so-called VOA, in which a desired value required from the system is set as the optimum value Pref.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing the configuration of the wavelength selective switch according to the second embodiment of the present invention. In the present embodiment, the present invention is applied to a wavelength selective switch (WSS) which is a kind of optical switch. In FIG. 3, 6 is an input port, 7a and 7b are output ports, 8 is a micromirror array, 10 is a main lens, 11 is a reflective diffraction grating, 12 is a collimating lens, and 13a and 13b are output ports 7a and 7b, respectively. Reference numeral 14 denotes an output light detection device provided in the control device. The micromirror array 8 includes a plurality of micromirror devices 9a, 9b, and 9c arranged one-dimensionally.

  The input port 6 emits a wavelength multiplexed optical signal 15 in which a plurality of optical signals having different wavelengths are multiplexed toward the main lens 10. The wavelength multiplexed optical signal 15 that has passed through the main lens 10 is incident on the reflective diffraction grating 11. The wavelength multiplexed optical signal 15 incident on the reflection type diffraction grating 11 is reflected by the reflection type diffraction grating 11 and demultiplexed into a plurality of optical signals 16a, 16b, and 16c having different wavelengths. The demultiplexed optical signals 16a, 16b, and 16c pass through the main lens 10 again and enter predetermined micromirror devices 9a, 9b, and 9c, respectively.

  The optical signals 16a, 16b, and 16c are reflected by the mirrors of the corresponding micromirror devices 9a, 9b, and 9c, respectively, and then become optical signals 17a, 17b, and 17c that are collimated by the collimating lens 12, and the main lens 10 Then, the light enters the reflective diffraction grating 11. The optical signals 17a, 17b, and 17c are reflected by the reflective diffraction grating 11, and then pass through the main lens 10 again and enter one of the output ports 7a and 7b. In the example of FIG. 3, the optical signals 17a and 17c reflected by the micromirror devices 9a and 9c are incident on the output port 7a, and the optical signal 17b reflected by the micromirror device 9b is incident on the output port 7b.

In this way, after the wavelength multiplexed optical signal 15 from the input port 6 is incident on the reflective diffraction grating 11 and demultiplexed into a plurality of optical signals, the demultiplexed optical signals are respectively associated with the corresponding micromirror devices 9a, 9b, By making the light incident on the mirror 9c and appropriately controlling the direction of each mirror by the control means 14 at this time, one set of optical signals having one wavelength or a plurality of optical signals having different wavelengths is provided. Alternatively, a plurality of sets can be extracted, combined for each set, and incident on the desired output ports 7a and 7b.
In FIG. 3, two output ports and three micromirror devices are configured. However, the present invention is not limited to the number of output ports or the number of micromirror devices. As an example of a desirable form, the number of micromirror devices may be the same as the number of wavelengths of the optical signal input from the input port, and the number of output ports may be the number of wavelengths or less.

The configuration of each micromirror device 9a, 9b, 9c is the same as that of the micromirror device 3a, 3b of the first embodiment.
Similar to the first embodiment, each of the output light detection devices 13a and 13b detects the power of the output light incident on the corresponding output ports 7a and 7b.

  Similar to the first embodiment, the control device 14 determines a driving voltage for controlling the mirror of the micromirror device 9a to a desired angle, and at the same time, applies a common bias voltage to each electrode of the micromirror device 9a. The output power detected by the corresponding output light detection devices 13a and 13b is determined so as to be optimal, and a voltage obtained by combining a bias voltage common to each electrode and a drive voltage for each electrode is used as a micromirror device. Apply to each electrode 9a. Similarly, the control device 14 determines the voltage applied to each electrode for each of the micromirror devices 9b and 9c.

As described above, in the example of FIG. 3, the optical signal reflected by the micromirror devices 9a and 9c enters the output port 7a, and the optical signal reflected by the micromirror device 9b enters the output port 7b. Therefore, the control device 14 determines the bias voltage of the micromirror devices 9a and 9c so that the power of the output light detected by the output light detection device 13a is optimized, and the output light detected by the output light detection device 13b. Therefore, the bias voltage of the micromirror device 9b is determined so that the power of is optimal. The control device 14 as described above can be realized with the same configuration as the control device 5 described in the first embodiment.
Thus, according to the present embodiment, the same effect as that of the first embodiment can be obtained in the wavelength selective switch.

  The present invention can be applied to a micromirror device and an optical switch using a plurality of micromirror devices.

It is a block diagram which shows the structure of the optical switch which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structural example of the control apparatus of the optical switch which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the wavelength selective switch which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows the structural example of the conventional optical switch. It is a disassembled perspective view which shows the structure of a micromirror device. It is sectional drawing of the micromirror device of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a, 6 ... Input port, 1b, 7a, 7b ... Output port, 2a, 2b, 8 ... Micromirror array, 3a, 3b, 9a, 9b, 9c ... Micromirror device, 4, 13a, 13b ... Output light detection device 5, 14 ... control device, 10 ... main lens, 11 ... reflective diffraction grating, 12 ... collimating lens, 200 ... mirror substrate, 211a, 211b, 221a, 221b ... torsion spring, 220 ... movable frame, 230 ... mirror , 300 ... Electrode substrate, 340a to 340d ... Electrode, 500 ... Mirror voltage application means, 501 ... Control means, 502 ... Drive voltage generation means, 503 ... Bias voltage generation means, 504a-504d ... Addition means, 505, 506, 508 ... subtracting means, 507 ... angle controller, 509 ... optical power controller.

Claims (4)

A mirror that is pivotally supported;
A plurality of electrodes spaced apart from the mirror;
An output light detection device that detects the power of output light that is reflected light of the mirror;
And a control device that generates and applies a common bias voltage to each electrode so that the power of the output light becomes an optimum value. The micromirror device according to claim 1, wherein
The controller is
Drive voltage generating means for generating a drive voltage for each electrode according to a desired tilt angle of the mirror;
Bias voltage generating means for generating the bias voltage so that the power of the output light becomes an optimum value;
A micromirror device comprising addition means for adding each of the bias voltage and the drive voltage for each electrode and applying the added voltage to the corresponding electrode. One or more input ports for input light;
One or more output ports for outputting output light;
One or more micromirror devices that selectively deflect one or more input light beams emitted from the input ports and selectively enter any of the output ports;
An output light detection device for detecting the power of the output light incident on the output port;
A control device for controlling the micromirror device to connect between the arbitrary input port and the output port;
Each micromirror device has a mirror that is rotatably supported and a plurality of electrodes that are spaced apart from the mirror,
The control device generates a bias voltage common to each electrode of the micromirror device on the optical path between the input port and the output port to be connected so that the power of the output light becomes an optimum value. An optical switch characterized by being applied. The optical switch according to claim 3,
The controller is
Drive voltage generation means for generating a drive voltage corresponding to a desired tilt angle of the mirror of the micromirror device on the optical path for each of the electrodes of the micromirror device;
Bias voltage generating means for generating the bias voltage so that the power of the output light becomes an optimum value;
An optical switch comprising adding means for adding the bias voltage and the drive voltage for each electrode and applying the added voltage to the corresponding electrode of the micromirror device on the optical path.

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