JP4676410B2 - Light switch - Google Patents

Description

  The present invention relates to an optical switch having a deflecting element such as a mirror.

  As one technique for realizing an optical switch, a technique using a deflecting element such as a micromirror has been proposed (see, for example, Non-Patent Document 1). A conventional optical switch using a micromirror is shown in FIG.

  The optical switch shown in FIG. 4 includes an input port 1a, an output port 1b, an input side micromirror array 2a, and an output side micromirror array 2b. 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. . In addition, the arrow in FIG. 4 has shown the advancing direction of the light beam.

  An optical signal emitted from a certain input port 1a is reflected by the mirror of the micromirror device 3a of the input side micromirror array 2a corresponding to this input port 1a, and its traveling direction is changed. As will be described later, the mirror of the micromirror device 3a is configured to be rotatable about two axes, and the reflected light of the micromirror device 3a can be directed to any micromirror device 3b of the output side micromirror array 2b. it can. Similarly, the mirror of the micromirror device 3b is also configured to be rotatable about two axes, and the reflected light of the micromirror device 3b is directed to an arbitrary output port 1b by appropriately controlling the tilt angle of the mirror. be able to. Therefore, by appropriately controlling the tilt angles of the mirrors of the input-side micromirror array 2a and the output-side micromirror array 2b, the optical path is switched, and the arbitrary input port 1a and output port 1b arranged two-dimensionally Can be connected.

  The most characteristic components of such an optical switch are micromirror devices 3a and 3b having mirrors. Conventionally, as shown in FIGS. 5 and 6, 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 (for example, (Refer nonpatent literature 1.).

  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 connect the movable frame 220. 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 are provided on the upper surface of the base portion 310 so as to sandwich the protruding portion 320. 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. The mirror 230 can be tilted 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, Volume 15, Issue: 10, pp1360-1362

  In the optical switch as described above, the positional error between the input / output port and the mirror and the change in the mirror tilt angle occur due to environmental changes such as ambient temperature and humidity, etc., and the deviation from the optimum mirror tilt angle gradually increases. A drift occurs in which the power loss of the output light fluctuates with time.

  However, when the drift per unit time is large, the relationship between the voltage applied to the electrodes 340a to 340d and the intensity of the output light greatly changes even during perturbation. In some cases, the maximum value of the intensity was searched.

For example, when the relationship between the voltage applied to the electrodes 340a to 340d and the light intensity of the output light is as shown in FIG. 7A, the light intensity in the range ΔV from the voltage V ₁ [V] to the voltage V ₂ [V]. The maximum value is the light intensity I _{2 at} the voltage V ₂ . However, if a large drift occurs in the amount of deviation from the optimum mirror tilt angle per unit time, for example, as shown in FIG. 7B, the light intensity I _{4 at} the time t = 2Δt after the sampling time is maximum. However, the light intensity I ₂ at time t = 0 is determined to be the maximum value. In this case, since the range ΔV is narrow, it is not possible to search for a driving voltage at which the light intensity becomes maximum.

  Accordingly, the present invention has been made to solve the above-described problems, and an object thereof is to provide an optical switch capable of accurately searching for an optimum posture of a deflection element.

In order to solve the problems as described above, an optical switch according to the present invention is rotatably supported by at least one input port for inputting input light and at least one output port for outputting output light. A mirror, and a control electrode disposed opposite to the mirror, and selectively deflects the input light input to the input port by deflecting the input light by a mirror inclined according to the voltage applied to the control electrode. The mirror device to be incident, the perturbation unit that perturbs the mirror by applying a voltage that changes within a predetermined range to the control electrode, and the mirror deflection angle at which the output light power becomes the optimum value when the mirror is perturbed. A detection unit for detecting, a measurement unit for measuring in advance a change amount of the tilt angle of the mirror when a voltage is applied to the control electrode, and a range setting unit for setting a predetermined range based on the change amount, the measurement unit comprising: Detecting the light intensity of the output light at a predetermined sampling time interval, the amount of change is measured by comparing the values for each sampling time, the range setting unit is controlled to tilt the variation a predetermined range It is characterized in that it is set above the range of the voltage applied to the electrode . The optimum output light power, that is, the light intensity means a light intensity at which the optical loss is minimized or a desired light intensity based on a request from the system. The drive voltage when realizing the rotation angle of the mirror capable of obtaining such light intensity is referred to as an optimum drive voltage.

The optical switch further includes a time setting unit configured to set a time for supplying a voltage that varies within a predetermined range by the perturbation unit, and the time setting unit includes a preset power loss power range. The time may be set to be equal to or less than a value obtained by dividing the range of the tilt angle of the mirror corresponding to the above by the amount of change per sampling time.

  According to the present invention, it is possible to search for the maximum value of the power of the output light without being affected by the drift by setting the predetermined range based on the change amount of the tilt angle of the mirror of the unit time value. As a result, the optimum deflection angle of the mirror can be searched accurately.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, the same components as those described in the background art section with reference to FIGS. 4 to 6 are denoted by the same names and reference numerals, and the description thereof is omitted as appropriate.

[Configuration of optical switch]
As shown in FIG. 1, the optical switch 10 according to the present embodiment includes an input port 1a, an output port 1b, an input side micromirror device 3a, an output side micromirror device 3b, and an output light measurement device 4. And a control device 5.

  The output light measuring device 4 detects the intensity of the output light emitted from the output port 1b and converts it into an electrical signal. As a configuration example of such an output light measuring device 4, a configuration in which a part of the output light is cut out and the intensity of the output light is measured by a light receiving element such as a photodiode can be considered.

  The control device 5 includes a drive unit 6, a detection unit 7, a control unit 8, and a storage unit 9.

  The drive unit 6 supplies a drive voltage to the micromirror devices 3a and 3b based on an instruction from the control unit 8 to incline the mirror 230 at a predetermined angle, or gives a minute change to the drive voltage to move the mirror 230. Perturb.

  The detection unit 7 detects the measurement result of the output light by the output light measurement device 4 when the driving unit 6 drives the micromirror devices 3a and 3b. The detected measurement result is output to the control unit 8.

  The control unit 8 is a functional unit that controls the overall operation of the optical switch 10, and includes at least a search setting unit 81, a perturbation unit 82, an optimum value detection unit 83, and a switching unit 84.

  The search setting unit 81 is a functional unit that sets a range and time when the mirror 230 is perturbed by the perturbation unit 82 according to the drift amount of the power loss of the output light. Such a search setting unit 81 measures a drift amount of power loss of output light at a predetermined unit time (hereinafter referred to as “sampling time”) interval, and based on the measurement result of the measurement unit 81a. A range setting unit 81b for setting a predetermined range in which the mirror 230 is perturbed (hereinafter referred to as “search range”), and a predetermined time for which the mirror 230 is perturbed based on the measurement result of the measurement unit 81a (hereinafter referred to as “search time”). And a time setting unit 81c for setting. Here, the search range means a range of drive voltage (hereinafter referred to as “perturbation voltage”) that is periodically changed to be supplied to the micromirror devices 3 a and 3 b in order to perturb the mirror 230. The search time means the time required to perturb the mirror 230 with all perturbation voltages when the mirror 230 is perturbed with the perturbation voltage set within the search range. The perturbation means that the mirror 230 is vibrated by supplying a perturbation voltage to each electrode of the micromirror devices 3a and 3b. For example, when there are four electrodes 340a to 340d as shown in FIGS. 5 and 6, the mirror 230 is perturbed by supplying a perturbation voltage to each electrode. Note that the search range and search time set by the search setting unit 81 are stored in the storage unit 9.

  The perturbation unit 82 perturbs each mirror 230 based on the search range set by the range setting unit 81b when connecting the optical path between the arbitrary micromirror device 3a and the arbitrary micromirror device 3b. Perturbation voltage is set, and this perturbation voltage is supplied to the micromirror devices 3 a and 3 b via the drive unit 6. The supply of the perturbation voltage is performed so that the mirror 230 is perturbed with each perturbation voltage within the search time set by the time setting unit 81c.

  The optimum value detection unit 83 determines the optical path between the arbitrary micromirror device 3a and the arbitrary micromirror device 3b from the detection result of the light intensity of the output light by the detection unit 7 when the mirror 230 is perturbed by the perturbation unit 82. A drive voltage (hereinafter referred to as “operating voltage”) that realizes an optimum deflection angle, that is, an inclination angle of each mirror 230 at the time of connection is detected.

  The switching unit 84 connects the corresponding micromirror device 3a via the drive unit 6 based on the operating voltage stored in the storage unit 9 when connecting the optical path between the arbitrary micromirror device 3a and the arbitrary micromirror device 3b. , 3b is supplied with an operating voltage.

  The storage unit 9 stores the search range and search time set by the search setting unit 81, the perturbation voltage set by the perturbation unit 82, the program for realizing the operation of the optical switch 10, and the like.

  Such a control device 5 includes an arithmetic device such as a CPU, a storage device such as a memory and an HDD (Hard Disc Drive), an input device that detects input of information from the outside such as a keyboard, a mouse, a pointing device, a button, and a touch panel, I / F devices that send and receive various types of information via communication lines such as the Internet, LAN (Local Area Network), WAN (Wide Area Network), etc., and CRT (Cathode Ray Tube), LCD (Liquid Crystal Display) or FED The computer includes a display device such as (Field Emission Display) and a program installed in the computer. That is, the hardware device and software cooperate to control the above hardware resources by a program, and the above-described drive unit 6, detection unit 7, control unit 8, and storage unit 9 are realized. Note that the program may be provided in a state of being recorded on a recording medium such as a flexible disk, a CD-ROM, a DVD-ROM, or a memory card.

[Search setting operation]
Next, the search range and search time setting operation by the search setting unit 81 will be described.

  First, the measurement unit 81a of the search setting unit 81 measures the drift amount of the power loss of the output light at the sampling time interval. In this measurement, a predetermined operating voltage is supplied to an arbitrary micromirror device 3a, 3b for measuring the drift amount, the mirror 230 is tilted to a predetermined angle, an optical path is connected between them, and an external input is made. This is performed based on the measurement result of the output light measurement device 4 when an optical signal having a predetermined light intensity distribution is input from the port 1a toward the micromirror device 3a. That is, the drift amount is measured by detecting the light intensity of the output light at the sampling time interval and comparing the values for each sampling time.

  When the drift amount is measured, the range setting unit 81b of the search setting unit 81 determines the range of voltages to be applied to the electrodes 340a to 340d in order to tilt the amount of drift of the mirror corresponding to the drift. The search range is set so as to be wider. This search range is set for each sampling time. The perturbation voltage is set by the perturbation unit 82 based on such a search range. In addition, the time setting unit 81c of the search setting unit 81 sets the search time to be equal to or less than a value obtained by dividing the tilt angle range of the mirror 230 corresponding to the preset power loss amount of the output light by the drift amount per sampling time. Set.

  By setting the search range in this way, even if drift occurs, it is possible to search for the peak of the light intensity of the output light in a wider range than this drift, so the optimum of the mirror 230 The posture can be searched. Further, by setting the search time as described above, it is possible to perform a search at a shorter interval than when the light intensity of the output light is lost by a predetermined value or more, and it is possible to search near the peak of the light intensity of the output light. As a result, the optimum posture of the mirror 230 can be searched.

  Next, an example of the setting operation of the search range and the search time will be described with reference to FIG. FIG. 2 shows a drift of loss of output light as a function of time in a one-dimensional model in which the rotation angle error increases in one direction along the mirror rotation axis, the movable frame rotation axis, etc., and 6 is a graph showing a relationship between a loss of output light and a tilt angle of a mirror 230. In FIG. 2, a case where the maximum value of the light intensity of the output light is determined by comparing three points will be described as an example. Therefore, in FIG. 2, the curves y1 to y3 mean the first search, and y4 means the second search. The meaning of each symbol in FIG. 2 is as follows.

Δθ: Search range Δt: Sampling time ΔL: Angle corresponding to target loss fluctuation range T _L : Search one cycle time α: Drift time conversion factor (angle / unit time) per unit time, drift drift loss per unit time Coefficient αΔt converted to angle: drift angle amount per perturbation time αT _L : drift angle amount per search cycle

The angle-loss distribution at each sampling time represented by the curves y _{1 to} y ₄ is a quadratic function model. Since the drift angle amount is generated by α ₁ at time t, the loss distribution function is as shown below.

When t = 0 and θ = 0: y ₁ (θ, t) = 0 (position a in the figure)
When t = Δt, θ = Δθ: y ₂ (θ, t) = − Δθ ² + 2αΔθΔt−α ² Δt ²
When t = 2Δt, θ = Δθ: y ₃ (θ, t) = − Δθ ² + 4αΔθΔt-4α ² Δt ²

  In such a one-dimensional model, the search range and search time are set so as to satisfy the following conditions [1] and [2].

[1] Conditions for finding a peak value by comparing three points with drift

When t = Δt to t = 2Δt, the range setting unit 81 of the search setting unit 81 sets the search range to be equal to or greater than the drift amount. Therefore, as shown in the following equation (1), the search range Δθ is set to be equal to or larger than the drift angle amount αΔt per sampling time.

Δθ> αΔt (1)

[2] Conditions for entering the loss fluctuation regulation value even if there is a drift

  As shown in the following equation (2), the angle with respect to the loss variation regulation value is set to be smaller than the angle amount drifting in the time required for one search cycle.

ΔL> αT _L (2)

  ΔL is set based on the operating voltage stored in the storage unit 9. For example, when the loss fluctuation width is defined as 0.5 dB, the angle width value is 0.5 dB lower than the peak position angle. In addition, the time required for one search cycle is set to be equal to or less than the value obtained by dividing the angular width determined by the loss variation prescribed value by the drift coefficient.

  The range setting unit 81b and the time setting unit 81c of the search setting unit 81 set the search range and the search time so as to satisfy the conditions as described above. As a result, even when drift occurs, the peak of the light intensity of the output light can be searched, so that the optimum posture of the mirror 230 can be searched more accurately.

  Note that, depending on the system environment in which the optical switch is used, it may be necessary to prevent a loss fluctuation due to perturbation during search from exceeding a specified value. In such a case, if the specified value is “perturbation width specified value”, the search range Δθ can be set so that the difference between the maximum loss value and the minimum value in the search range Δθ is less than the specified loss width value. Good.

[Perturbation operation]
Next, the perturbation operation by the perturbation unit 82 will be described.

  First, when the search range is set by the method described above, the perturbation unit 82 sets the perturbation voltage based on this search range. This perturbation voltage is set in sampling time units. The initial perturbation voltage is set from a search range centered on the operation voltage stored in advance in the storage unit 9. The next perturbation voltage is applied after the lapse of the sampling time from the application of the first perturbation voltage, and is set based on the search range set according to the drift amount at that time. Accordingly, the search range at this time is shifted in a predetermined direction from the initial search range, or the range is wider than the initial search range. Further, the perturbation voltage is constituted by a value obtained by dividing the set search range at a predetermined interval. Specific examples are shown below.

  For example, in the case where the search range in the X direction of the micromirror device 3a is set to X1 and the Y direction is set to Y1, if the perturbation voltage is set in a spiral shape, as shown in FIG. 3, it is within the range consisting of X1 and Y1. The perturbation voltage is set by dividing the range at predetermined intervals in consideration of the number of turns of the spiral. The perturbation voltage is similarly set for the micromirror device 3b. In FIG. 3, 25 perturbation voltages are set, but the number of perturbation voltages to be set can be set freely as appropriate. Further, the method of setting the perturbation voltage is not limited to the spiral shape, and can be set freely as appropriate, for example, approximately N-shaped or latticed.

  When the perturbation voltage is set when connecting the optical path between the micromirror device 3a and the micromirror device 3b to which an optical signal having a predetermined light intensity distribution is input from the input port 1a from the outside, the perturbation unit 82 In order to search for an optimum operating voltage with a small connection loss of the propagating optical signal, an optical signal having a predetermined light intensity distribution is input from the outside to the micromirror device 3a from the input port 1a. Further, the perturbation voltage of the micromirror device 3b is fixed to the outermost shell point, and the mirror 230 is perturbed while sequentially moving the respective points where the perturbation voltage of the micromirror device 3a is set. The perturbation is performed within the search time while moving each point. That is, a one-cycle search in which perturbation is performed covering all the set perturbation voltages is performed within the search time. At this time, the light intensity of the optical signal measured by the output light measurement device 4 via the detection unit 7 is stored in the storage unit 9.

  When the perturbation voltage of the micromirror device 3a is sequentially moved for each set point, the perturbation voltage of the micromirror device 3b is moved to the next point, and each set point of the micromirror device 3a is sequentially moved Each mirror 230 is perturbed. When the micromirror device 3b is moved to the last value of the perturbation voltage, the light intensity at each point is stored in the storage unit 9. When the optimum value detector 84 connects the optical path between the micromirror device 3a and the micromirror device 3b, the perturbation voltage when the light intensity becomes maximum among the light intensities stored in the storage unit 9 is connected. Set as the optimal operating voltage. Such a search for the operating voltage is performed within the search time.

  Thus, according to the present embodiment, by making the search range equal to or greater than the drift amount in the sampling time, it becomes possible to search for the peak of the output light without being affected by the drift. The optimal posture of the mirror 230 can be searched more accurately.

  The present invention can be applied to an optical element such as an optical switch that perturbs a changing element such as a mirror by applying a periodically changing drive voltage.

(A) is a block diagram showing the configuration of the optical switch of the present invention, (b) is a block diagram showing the configuration of the control device. It is a figure for demonstrating search setting operation | movement. It is a figure which shows an example of a perturbation voltage. It is a perspective view which shows the structure of an optical switch typically. It is a perspective view which shows the structure of a mirror apparatus typically. It is sectional drawing which shows the structure of a mirror apparatus typically. (A) is a schematic diagram which shows the relationship between the light intensity of output light, and a drive voltage, (b) is a schematic diagram which shows the relationship between the light intensity of output light when a drift generate | occur | produces, and a drive voltage.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a ... Input port, 1b ... Output port, 3a ... Input side micromirror device, 3b ... Output side micromirror device, 4 ... Output light measuring device, 5 ... Control device, 6 ... Drive part, 7 ... Detection part, 8 ... Control unit, 9 ... storage unit, 81 ... search setting unit, 81a ... measurement unit, 81b ... range setting unit, 81c ... time setting unit, 82 ... perturbation unit, 83 ... optimum value detection unit, 84 ... switching unit.

Claims (2)

At least one input port for inputting input light;
At least one output port for outputting output light;
A mirror that is rotatably supported and a control electrode disposed opposite to the mirror, and deflects input light input to the input port by the mirror that is inclined according to a voltage applied to the control electrode. A mirror device that selectively enters any of the output ports;
A perturbation unit that perturbs the mirror by applying a voltage that changes within a predetermined range to the control electrode;
A detection unit for detecting a deflection angle of the mirror at which the power of the output light becomes an optimum value when the mirror is perturbed;
A measurement unit that measures in advance the amount of change in tilt angle of the mirror when a voltage is applied to the control electrode;
A range setting unit that sets the predetermined range based on the amount of change, and
The measurement unit detects the light intensity of the output light at a predetermined sampling time interval, measures the change amount by comparing the values for each sampling time ,
The said range setting part sets the said predetermined range more than the range of the voltage applied to the said control electrode in order to tilt the said variation | change_quantity, The optical switch characterized by the above-mentioned . A time setting unit for setting a time for supplying a voltage that varies within the predetermined range by the perturbation unit;
The time setting unit sets the time to be equal to or less than a value obtained by dividing a range of the tilt angle of the mirror corresponding to a preset power loss range of the output light by the amount of change per sampling time. the optical switch of claim 1 Symbol mounting, characterized in that.

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