JP4719193B2 - Light switch - Google Patents

Description

  The present invention relates to an optical switch used in a communication optical transmission device, a wavelength routing device, or the like.

  In recent years, in the field of optical communication, high-speed communication utilizing the characteristics of light has been realized by transmitting an optical signal to a partner without converting it into an electrical signal. Also, it has been realized to perform large-capacity optical transmission using a single optical fiber by WDM (Wavelength Division Multiplexing) technology that multiplexes one optical signal in correspondence with one wavelength. With the development of such optical communication technology, an optical switch that switches a path without converting an optical signal into an electric signal or the like has attracted attention.

  The optical switch has been promoted to have higher functionality as the optical communication network becomes larger. Conventionally, a simple 1 × 2 switch having one input port and two output ports has been used, but in recent years, it has hundreds of input ports and output ports and can perform optical path control in the unit of 10,000. A matrix switch (for example, see Non-Patent Document 1), a wavelength selection switch for selecting an arbitrary wavelength from several tens of wavelengths and outputting it from any of a plurality of output fibers (for example, see Patent Document 1), etc. are proposed. Has been. Among them, the spatial optical system optical switch can achieve high functionality and downsizing.

  The spatial optical system optical switch realizes high functionality and miniaturization by three-dimensionally arranging spatial optical components such as lenses and mirrors together with optical fibers. For such a spatial optical switch, a micromirror device (for example, see Patent Document 2) created by MEMS (Micro Electro Mechanical Systems) technology is often used. Since the MEMS micromirror device can rotate the mirror by a plurality of rotation axes, for example, in addition to the first rotation axis that realizes switching of the optical path, the second rotation that is orthogonal to the rotation axis. It has been proposed to control the optical loss by providing an axis and tilting the mirror about this second pivot axis. By using such an optical loss control function in a wavelength selective switch used in, for example, a WDM optical network, the power between optical signals generated by the difference in wavelength gain and loss in the optical transmission line can be increased even if the number of relays is increased. Since variations can be suppressed, the number of nodes can be increased. Therefore, a spatial optical system optical switch capable of controlling optical loss is becoming an indispensable device for future multi-wavelength optical networks.

  FIG. 24 shows an example of a spatial optical system optical switch using a MEMS micromirror device. In this optical switch, one incident port 101 that introduces input light input from the outside into the inside of the apparatus, N output ports 102 that output input light to the outside, and input from the incident port 101 by a mirror. Along with the MEMS mirror device 103 that selectively reflects incident light toward the exit port 102, a collimator lens 104 that adjusts the input light input from the entrance port 101 in parallel, and the reflected light from the MEMS mirror device 103 is an exit port. And a coupling lens 105 coupled to 102.

  Here, as shown in FIGS. 24 and 25, the MEMS mirror device 103 can rotate the mirror 103a around the X axis and the Y axis orthogonal to each other. Thereby, for example, when the mirror 103 a is rotated around the Y axis, the input light can be selectively reflected to the emission port 102. Further, when the mirror 103a is rotated around the X axis, the optical loss of the input light in the Y axis direction can be controlled. As shown in FIG. 26, such a mirror device 103 often uses a gimbal structure in which a mirror 103a is connected to a base portion via a movable frame. In addition, a plurality of electrodes 1031 to 1034 are arranged opposite to the mirror 103a. By selectively applying a voltage to these electrodes, electrostatic attraction acts on the mirror 103a, and the mirror 103a rotates in a predetermined direction. It will be. In FIG. 26, as an example, the electrodes 1031 to 1034 have a generally rectangular shape in plan view as a whole, and each has a shape of a generally triangular shape in plan view divided into four by its diagonal lines.

Here, the electrode 1031 and the electrode 1033 are disposed symmetrically with respect to the Y axis. Therefore, it is possible to tilt the mirror 103a is applied to the electrode 1031 and the electrode 1033 to the voltage V _x of a predetermined value at a predetermined angle with respect to the Y axis. Here, output port 102, because it is parallel in the X-axis direction, by rotating the mirror 103a by applying a voltage V _x to the Y axis, as shown in FIG. 27, the input light of an arbitrary It can be reflected by the exit port 102. The relationship between the voltage V _x and the light intensity P at this time is represented by a graph as shown in FIG. That is, the peak of only the light intensity quantity of output port 102 on the V _x axis exists.

Further, the electrode 1032 and the electrode 1034 are disposed symmetrically with respect to the X axis. Therefore, by applying a voltage V _y having a predetermined value to the electrodes 1032 and 1034, the mirror 103a can be tilted at a predetermined angle with respect to the X axis as shown in FIG. Here, since the exit ports 102 are arranged in parallel in the X-axis direction, when the voltage V _y is applied, the reflected light moves in the Y-axis direction. Therefore, the coupling ratio of the reflected light to the exit port 102 is changed. Can be adjusted. The relationship between the voltage V _y and the light intensity P at this time is represented by a graph as shown in FIG. That is, there is a peak with the highest coupling efficiency on the origin of the V _y axis and the P axis.

When the light intensity profiles of the V _x axis and the V _y axis shown in FIGS. 28 and 30 are depicted as contour maps on the V _x −V _y voltage plane, the graph shown in FIG. 31 can be obtained. In general, the control voltage ranges of V _x and V _y are approximately the same, and there are a plurality of peaks in the V _x direction and one peak in the V _y direction, so the light intensity profile on the V _x -V _y voltage plane. Has a shape in which elongated ellipses in the V _y direction are arranged in the V _x direction by the number of emission ports. At this time, selecting the exit port corresponds to applying the voltage V _x corresponding to the vertex of the ellipse corresponding to the exit port. Lowering the loss means searching for a peak of light intensity by applying an appropriate value as the voltage V _y and scanning the ellipse in the major axis direction. Therefore, when the input light is output from an arbitrary output port with low loss, the voltage V _x corresponding to the output port is applied, and the peak of the light intensity is searched by changing the voltage V _y , which corresponds to the peak. A voltage V _y is applied.

The electrostatic drive type MEMS mirror device used for such an optical switch has a drive applied to the electrodes due to a drift related to the time required to charge between the electrodes or other stray capacitances or the influence of charging around the electrodes. A so-called drift phenomenon may occur in which the tilt angle of the mirror is displaced from the original angle determined by the voltage. When this drift phenomenon occurs, in the case of the mirror device having the two rotation axes as described above, both the angular deviation of the Y axis that selects the exit port and the angular deviation of the X axis that controls the optical loss both change in the light intensity. Leads to. Therefore, conventionally, in order to obtain output light having a desired light intensity, the light intensity of the output light output from the exit port is monitored, and the optical axis is controlled based on the deviation from the desired light intensity. It has been done to adjust the turning angle. Specifically, the angle around the X axis, that is, the value of the voltage V _x is adjusted so that the loss increases periodically if the light intensity is higher than a desired value, and the loss decreases if the light intensity is small.

JP 2007-140168 A JP 2003-57575 A Tsuyohi Yamamoto, et al., "A Three-Dimensional MEMS Optical Switching Module Having 100 Input and 100 Out put Ports", IEEE Photonics TECHNOLOGY LETTERS, VOL. 15, NO.10, pp.1360-1362, 2003

  However, when the optical loss is compensated by adjusting the angle around the X axis based on the light intensity of the output light as in the prior art, the angle deviation of the mirror occurs at either of the two rotation axes from the light intensity of the output light. For example, even if an optical loss occurs due to an angle shift in the Y axis for selecting the output port, in order to compensate for the loss, As a result, the optical loss cannot be compensated, and output light having a desired light intensity cannot be obtained.

For example, as shown in FIG. 32, when the light intensity changes in the V _y axis direction (reference a), by applying the value of the voltage V _y so as to cancel the voltage corresponding to the change (reference a b) The loss of light intensity can be compensated. As shown in FIG. 33, even when the light intensity changes in the V _x axis direction along with the V _y axis direction (reference symbol c), if the change amount in the V _x direction is slight, V _x By applying an appropriate voltage to one of the voltages V _y so as to cancel the change in the light intensity corresponding to the change in the voltage axes of V and V _y (symbol d), the loss of the light intensity can be compensated. However, as shown in FIG. 34, where the light intensity is increased when changed (code e), changing the value of how much V _y direction voltage V _y to V _x-axis direction, to compensate the loss of light intensity Output light having a desired light intensity cannot be obtained.

Accordingly, an object of the present invention is to provide an optical switch that can effectively search for a voltage value at which the light intensity of output light becomes a predetermined value or more .

In order to solve the above-described problems, an optical switch according to the present invention includes at least one optical input unit that inputs input light, at least one optical output unit that outputs output light, an X axis, and the X axis. A mirror that is rotatably supported with respect to a Y-axis different from the axis, and a plurality of electrodes that are arranged to face the mirror, and by applying a driving voltage to these electrodes, the mirror is inclined at a predetermined angle. a mirror unit, a detector for detecting the light intensity of the output light output from the light output section, based on the detection result of the detection unit, respectively Ru voltage to rotate the mirror about the X-axis and Y-axis It calculates the V _x and the voltage V _y, and a drive control unit for applying a driving voltage to the electrodes Ru selectively be output from an arbitrary optical output an input light inputted to the predetermined optical input An optical switch, the drive control unit , A voltage V _x and the voltage V _y, and the driving voltage updating part for calculating, based on the primary or more polynomial for the parameter V _t, when changing the parameter V _t, the voltage V _x to be calculated on the basis of the polynomial And the voltage V _y , a determination unit that determines whether the light intensity from the selected light output unit detected by the detection unit reaches a predetermined value, and the light intensity of the output light is determined by the determination unit. When it is determined that the predetermined value is not reached , the coordinates (V _x ′, V _y ′) corresponding to the parameter V _t ′ when it is determined that the predetermined value is not reached on the plane having V _x and V _y as the coordinate axes. as, about the line parallel to the coordinate axes of the V _x or V _y, change to change the polynomial such that the voltage V _x and V _y draws the trajectory calculated by changing the parameter V _t based on the polynomial is axisymmetric and a section, characterized in Rukoto
In addition, another optical switch according to the present invention includes at least one optical input unit that inputs input light, at least one optical output unit that outputs output light, and an X axis and a Y axis different from the X axis. And a mirror device that has a mirror that is rotatably supported and a plurality of electrodes that are arranged to face the mirror, and that tilts the mirror at a predetermined angle by applying a drive voltage to these electrodes, and a light output unit And a voltage V _x and a voltage V _y for rotating the mirror about the X axis and the Y axis, respectively, based on the detection result of the detection unit and the detection result of the detection unit. An optical switch including a drive control unit that applies a drive voltage to the electrodes and selectively outputs input light input to a predetermined light input unit from an arbitrary light output unit, , the voltage V _x and the voltage V _y A driving voltage updating part for calculating, based on the primary or more polynomial for the parameter V _t, when changing the parameter V _t, the voltage V _x and the voltage V _y is calculated based on the polynomial, the detection unit And a determination unit that determines whether or not the light intensity from the selected light output unit detected by the sensor reaches a predetermined value, and the determination unit determines that the light intensity of the output light does not reach the predetermined value If, on a plane whose coordinate axes of V _x and V _y, 'corresponding to (V _x' parameter V _t of the time it is determined not to reach, V _y ') about the coordinates, by a predetermined rotation angle, the polynomial And a changing unit that changes the polynomial so that the trajectory drawn by the voltage V _x and the voltage V _y calculated from the parameter V _t is rotated.

In the optical switch, the polynomial has parameters V _t , drive voltage offsets along the X axis and Y axis corresponding to an arbitrary optical output unit, V _0x and V _0y , and constants A and B (≠, respectively). 0), V _x = V _0x + A · V _t and V _y = V _0y + B · V _t . When the parameter V _t is changed, the drive control unit determines from the parameter Vt based on the polynomial The voltage Vx and the voltage Vy may be calculated. At this time, the polynomial, when a shaft and a linear function of V _y the angle formed and φ when the V _y in a plane whose coordinate axes of V _x and V _y expressed as a linear function of V _x, V _x = V _0x + V _t · sin φ and V _y = V _0y + V _t · cos φ may be used.

According to the present invention, the voltage V _x and the voltage V _y calculated based on a predetermined function are applied to the electrodes, so that the mirror rotates simultaneously around the X axis and the Y axis. It becomes possible to search for the values of the voltage V _x and the voltage V _{y at which} the intensity is equal to or higher than a predetermined value in a wider range than before, and as a result, the desired light even when the angular deviation occurs in the mirror device. Intense output light can be output.

[First Embodiment]
Hereinafter, a first embodiment according to the present invention will be described in detail with reference to the drawings. The present embodiment will be described by taking as an example a case where it is applied to a 1 × n port optical switch.

<Configuration of optical switch>
As shown in FIG. 1, the optical switch 1 according to the present embodiment includes one input-side optical fiber 11, n output-side optical fibers 12-1 to 12-n, input-side optical fiber 11, and output side. A MEMS mirror device 13 disposed on an optical path connecting the optical fibers 12-1 to 12-n, photodiodes 14-1 to 14-n for monitoring outputs from the output side optical fibers 12-1 to 12-n, and the photodiode 14 An A / D converter 15 that performs A / D conversion on the detection results of −1 to n, and a control device 16 that controls driving of the MEMS mirror device 13 based on an output from the A / D converter 15 are provided. Yes. Also, coupling lenses 17 and 18 for aligning the spatial optical system and the optical fiber are provided on the output side of the input side optical fiber 11 and the input side of the output side optical fiber 12, respectively.

Here, the MEMS mirror device 13 includes a mirror 13a that is rotatably supported by two rotating shafts in the X-axis direction and the Y-axis, and a plurality of electrodes (not shown) disposed to face the mirror 13a. It has. For example, as shown in FIG. 26, these electrodes may be arranged symmetrically with the X axis or the Y axis in between. In this case, by applying a voltage V _x to the electrodes disposed symmetrically to the Y axis, it is possible to rotate the mirror 13a in the X-axis. In addition, the mirror 13a can be rotated around the Y axis by applying the voltage V _y to the electrodes arranged symmetrically with respect to the X axis.

  Note that the electrodes of the MEMS mirror device 13 are not limited to those arranged symmetrically with respect to the X axis or the Y axis as described above, and the mirror 13a is different, for example, provided between the X axis and the Y axis. Any voltage can be set as appropriate as long as the voltage applied to each electrode for rotating around two axes can be distinguished for each axis.

  Further, as shown in FIG. 2, the control device 16 includes a detection unit 21, a drive voltage update unit 22, a drive voltage output unit 23, an arrival determination unit 24, a change unit 25, and an initial value setting unit 26. Is provided.

  The detector 21 calculates a deviation between the light intensity of the output light output from the output side optical fibers 12-1 to 12 -n and the predetermined light intensity from the output from the A / D converter 15.

  The drive voltage update unit 22 updates the value of the drive voltage supplied to each electrode of the MEMS mirror device 13 based on the detection result of the output light by the detection unit 21 and the determination result described later by the arrival determination unit 24. The updated drive voltage is input to the drive voltage output unit 23.

  The drive voltage output unit 23 supplies a drive voltage to each electrode of the MEMS mirror device 13 based on an instruction from the drive voltage update unit 22 or the initial value setting unit 26.

  The arrival determination unit 24 determines whether or not the light intensity reaches a predetermined value based on the light intensity of the output light detected by the detection unit 21.

  The change unit 25 changes the parameter of the drive voltage supplied to the MEMS mirror device 13 when the arrival determination unit 24 determines that the light intensity does not reach a predetermined value.

  The initial value setting unit 26 sets various initial values required when the control device 16 drives the MEMS mirror device 13.

  Such a control device 16 includes an arithmetic device such as a CPU, a storage device that stores various data such as an operation program, a driving intensity of the output light intensity MEMS mirror device 13, and the like. The above hardware resources are controlled by a program through the cooperation of the hardware device and software, and the detection unit 21, the drive voltage update unit 22, the drive voltage output unit 23 described above, An arrival determination unit 24, a change unit 25, and an initial value setting unit 26 are realized.

<Operation of optical switch 1>
Next, the overall operation of the optical switch 1 according to the present embodiment will be described. First, an optical signal (input light) input from the input side fiber 11 into the optical switch 1 is collimated or condensed by the collimator lens 17 and irradiated to the MEMS mirror device 13. The MEMS mirror device 13 reflects input light in a predetermined direction and inputs the input light to a predetermined output-side optical fiber 12 through a coupling lens 18.

At this time, the output side optical fibers 12 are juxtaposed at a predetermined interval along the X-axis direction of the mirror 13a included in the MEMS mirror device 13. Therefore, the control unit 16 supplies a predetermined voltage V _x with respect to the MEMS mirror device 13, an input-side optical fiber 11 a mirror 13a by a predetermined angle rotation about the Y axis and arbitrary output side optical fiber 12 By forming the optical path, the input light can be output from the arbitrary output side optical fiber 12.

Further, by supplying a predetermined voltage V _y to the mirror device 13 and rotating the mirror 13a around the X axis, the optical path of the reflected light of the input light by the mirror 13a can be moved in the Y axis direction. . Then, since the coupling efficiency between the reflected light and the output side optical fiber 12 changes, the light intensity of the output light output from the output side optical fiber 12 changes.

  An optical signal (output light) output from the output-side optical fiber 12 is split in power and received by the photodiodes 14-1 to 14-n. The light reception signal made up of an analog signal is A / D converted by the A / D converter 15 to become a digital signal and is inputted to the control device 16.

  Based on the light reception signal input from the A / D converter 15, the control device 16 sets a drive voltage to be supplied to the MEMS mirror device 13 so that the output light has a light intensity exceeding a predetermined value. This is supplied to the MEMS mirror device 13. Such setting of the drive voltage is performed, for example, by performing PID control well known as feedback control. Such a drive voltage setting operation will be described later.

<Drive voltage setting operation>
Next, the drive voltage setting operation by the control device 16 will be described with reference to FIG.

  First, when the controller 16 selects from the outside which of the output side optical fibers 12-1 to 12-n the input light is to be output (step S1), the initial value setting unit 26 selects the selected output side. A drive voltage corresponding to the optical fiber 12 is supplied to the MEMS mirror device 13 (step S2). Here, the initial value setting unit 26 includes in advance a table indicating the value of the drive voltage to be applied to the electrode of the MEMS mirror device 13 when the input light is reflected to each of the output side optical fibers 12-1 to 12 -n. You may be allowed to. In this case, the initial value setting unit 26 supplies the drive voltage to the MEMS mirror device 13 based on the table.

  When the drive voltage is supplied to the MEMS mirror device 13 and the mirror 13a is tilted based on the drive voltage, the input light is output as output light from the selected output-side optical fibers 12-1 to 12-n. The device 16 acquires the light intensity of the output light from the photodiodes 14-1 to 14 -n and the A / D converter 15 by the detection unit 21 (step S <b> 3), and detects whether this value exceeds a predetermined value. (Step S4).

  When the light intensity of the output light exceeds a predetermined value (step S4: YES), the control device 16 returns to the process of step S3.

  On the other hand, if the light intensity of the output light does not exceed the predetermined value (step S4: NO), the controller 16 determines whether the light intensity of the output light exceeds the predetermined value by the arrival determination unit 24. It is determined whether or not (step S5). Details of the arrival determination operation will be described later.

  When the light intensity may exceed a predetermined value (step S5: YES), the control device 16 updates the drive voltage supplied to the MEMS mirror device 13 by the drive voltage update unit 22 (step S6). The process returns to S2. Details of the update operation will be described later.

  On the other hand, when there is no possibility that the light intensity exceeds the predetermined value (step S5: NO), the control device 16 changes the parameter for updating the drive voltage by the changing unit 25 (step S7), and the process of step S5 is performed. Return to processing. Details of the parameter changing operation will be described later.

  Thereby, the optical switch 1 can output the input light input from the input side optical fiber 11 in the state which has the light intensity exceeding predetermined value from arbitrary output side optical fibers 12-1 to 12-n. .

<Update operation>
Next, the drive voltage update operation by the drive voltage update unit 22 will be described.

First, with respect to the voltage V _x for selecting the output side optical fibers 12-1 to 12 -n and the voltage V _y for controlling the loss of output light, the parameter V _t having these components as the components is _expressed by ).

V _x = V _0x + f _x (V _t ) (1)
V _y = V _oy + f _y (V _t ) (2)

Here, as shown in FIG. 4, V _0x and V _oy are offset values of drive voltages corresponding to the selected output side optical fibers 12-1 to 12 -n and drive voltages corresponding to the other output side optical fibers 12. This is the value of the drive voltage when the loss of light intensity is minimized when there is no angular deviation due to drift or the like. Further, f _x (V _t ) and f _y (V _t ) represent first-order or higher-order polynomials with respect to V _t . In the following description, a case where f _x (V _t ) and f _y (V _t ) are linear functions will be described as an example. In this case, the expressions (1) and (2) are expressed by the following expressions (3) and (4).

V _x = V _0x + A · V _t (3)
V _y = V _oy + B · V _t (4)

When the above equations (3) and (4) are shown on a plane having V _x and V _y as coordinate axes, the initial voltage, that is, a straight line that passes through the values of V _x and V _{y in} a state where no angular deviation has occurred. . When the inclination of this straight line with respect to the V _y axis is φ, the above expressions (3) and (4) are expressed by the following expressions (5) and (6). The angle φ can also be defined as the slope of the straight line with respect to V _x .

V _x = V _0x + V _t · sinφ (5)
V _y = V _oy + V _t · cos φ (6)

As shown in FIG. 5, the drive voltage update unit 22 sequentially changes the values of the voltage V _x and the voltage V _{y using} the parameter V _t inclined by the angle φ with respect to the V _y axis as a variable, and the light intensity of the output light In other words, so-called feedback control is performed to search for the optimum value of the. As a result, when the value of V _t is changed, the values of V _x and V _y are changed at the same time. Therefore, the mirror 13a of the mirror device 13 is simultaneously changed around the X axis and the Y axis. The tolerance for is expanded. For example, as shown in FIG. 6, when the allowable range r of the angular deviation is set with a predetermined light intensity P ₁ as a reference, only the value of the voltage V _y is changed as in the prior art, and the mirror 13a is rotated only in the X-axis direction. When it is changed, the allowable range of angular deviation is an area between two straight lines parallel to the V _y axis (see the graph on the left side of FIG. 7). On the other hand, when the drive voltage is updated using the parameter V _t as in the present embodiment, the allowable range of the angle deviation is an area between two straight lines parallel to the straight line V _t (the graph on the right side of FIG. 7). The allowable range is larger than in the conventional case. Therefore, even when an angular deviation occurs, it is possible to search for a driving voltage that can output output light having a desired light intensity in a wider range than in the past.

<Parameter change operation>
Next, the changing operation of the parameter V _t by the changing unit 25 will be described.

As described above, by setting the parameter V _t that is inclined with respect to the V _y axis by the drive voltage update unit 22, the allowable range of angular deviation can be expanded, but an angular deviation larger than the allowable range occurs. In this case, it is impossible to obtain output light having a desired light intensity even when the parameter Vt is used. For example, when controlled the operation of the MEMS mirror device 13 with no angle deviation, as shown in FIG. 8, a drift or the like, to cause angular displacement as shown in FIG. 9, the linear V _t is V _x Assume that the axis is displaced in the positive direction. In such a case, as shown in FIG. 10, the output light having the desired light intensity (the innermost ellipse in FIG. 10) cannot be obtained when the parameter V _t is changed to some extent. In such a case, the arrival determination unit 24 determines that the light intensity of the output light does not exceed a predetermined value. In response to this result, the changing unit 25 changes the relationship between the parameter V _t and the voltage Vx and Vy.

For example, as shown in FIG. 11, the parameter V _t is changed to be symmetrical with respect to the V _y axis, in other words, the sign of φ that is the intersection angle between the parameter V _t and the V _y axis is reversed. Thereby, the constant terms V _0x and V _0y in the relational expressions (5) and (6) between V _t and V _x and V _y are changed to V _0x ′ and V _0y ′ represented by the following expression (7). In addition, the angle between the new V _t and the V _y axis is (−φ).

(V _0x ′, V _oy ′) = (V _x (V _t ′) −V _t ′ · sin (−φ), V _oy ) (7)

Here, V _t ′ is a value in the vicinity of the maximum point on the V _t axis before the change, and indicates coordinates (hereinafter referred to as a base point) that are determined to be unable to reach the target predetermined light intensity value. . V _x (V _t ′) is the value of V _{x at} V _t ′. The above equation (7) includes a trigonometric function, but since sin (−φ) = − sinφ, if φ is constant, sinφ can be given as a constant, In this case, it is only necessary to make the sign of sin negative. Therefore, the calculation for performing the conversion is sufficient with four arithmetic operations, and can be executed without imposing a heavy load on the CPU.

Incidentally, the line changing unit 25 not only changes in line symmetry parameter V _t with respect to V _y axis, for example, as shown in FIG. 12, with respect to V _x axis parameter V _t around the base point Alternatively, the parameter V _t may be rotated by a predetermined angle α around the base point as shown in FIG. In particular, FIG. 11, when changing the V _t axisymmetric as shown in FIG. 12, since the differential value before and after the light intensity and V _t voltage switching does not change rapidly, the same control parameters before and after the switching An update operation can be performed using feedback control.

<Arrival judgment operation>
Next, the arrival determination operation by the arrival determination unit 24 will be described. Examples of the arrival determination operation include a method based on the maximum value of light intensity and a method based on a differential value of light intensity. Each will be described below.

(Method based on maximum value)
In this case, the arrival judgment portion 24, as shown in FIG. 14, the control monitors the value P of the light intensity in the voltage axis V _t axis on a, if the value of the current intensity is equal to or greater than the value measured in the previous Updates the maximum value to the current light intensity, and if the current light intensity falls below the previous value, the maximum value at that time is compared with the desired desired light intensity. At this time, when the maximum value P is lower than the target value, the arrival determination unit 24 determines that the target value cannot be reached on the control axis.

(Method based on differential value)
In this case, the arrival judgment portion 24, as shown in FIG. 15, to monitor the sign change in the differential value dP / dV _t between the value P of the control voltage V _t and the light intensity, the both positive and negative sign in the past It is determined that the maximum point has been passed by detecting whether or not it has been taken. Even when it is determined that the maximum point has been passed by this method, if the light intensity of the output light does not exceed the target value, the arrival determination unit 24 determines that the light intensity cannot reach the target value on the control axis. To do.

<Specific Example of Operation of Control Device 16>
Next, a specific example of the operation of the control device 16 will be described in detail with reference to FIG.

First, the initial value setting unit 26 outputs the optical fibers 12-1 to 12-n that output optical signals, the corresponding initial drive voltages (V _0x , V _0y ), and target values P _t , V _{t of the} light intensity. Initial values V _t0 and parameters for PID control, etc. are initialized (step S11). Further, the initial installation unit 26 sets an initial value V _t0 of the parameter Vt (step S12). When these are set, the drive voltage output unit 23 calculates the voltages V _x and V _y with respect to the set V _t0 based on the initial drive voltage, and supplies this to the MEMS mirror device 13 (step S13). .

Thereby, when an optical signal is output from the symmetric output side optical fibers 12-1 to 12-n, the detector 21 measures the light intensity P ₀ of the optical signal (step S14). At this time, with the initial value V _t0 of the parameter V _t , the light intensity of the output light is not necessarily the target value. Therefore, the drive voltage update unit 22 periodically calculates a deviation e (= P _t −P ₀ ) between the target value and the light intensity so that the light intensity of the output light matches the target value (step S15). applying a negative feedback amount Fb in accordance with the deviation V _t (step S16, S17).

When V _t is updated, the driving voltage output unit 23 is again applied to the electrodes of the MEMS mirror device 13 calculates the voltage V _x, V _y (step S18). As a result, the light intensity of the output light approaches the target value and eventually coincides.

However, the angle deviation caused by drift or the like, it may no longer be able to output light reaches the target value on the V _t axis. In order to determine such a case, the arrival determination unit 24 calculates the difference between the previous and current values of PID control that periodically repeats the differential value dp / dV _t on the V _t axis {(dp / dV _t ) = {P ₀ (current) −P ₀ (current)} / {V _t (current) V _t (previous)} (steps S19 and S20). When the differential value becomes positive, PlusFlag is set to 1 (step S21). On the other hand, when the differential value becomes negative, the arrival determination unit 24 sets MinusFlag to 1. Note that MinusFlag and PlusFlag have an initial value of 0.

  When the product of both MinusFlag and PlusFlag is 1 (step S22: YES), the differential value dp / ds has experienced both positive and negative values, that is, it has passed through the local maximum point. When it is determined that the light intensity has not reached the target value, the conversion unit 25 performs the parameter changing operation as described above (step S26). When this parameter changing operation is performed, the conversion unit 25 returns MinusFlag and PlusFlag to 0 which is an initial value.

If the product of both MinusFlag and PlusFlag does not become 1 (step S22: NO), the driving voltage updating unit 22 updates the parameters V _t and the light intensity P ₀ to the current value (step S24).

  The above-described operation is repeated until a stop command is input from the outside (step S24). By doing in this way, the optical switch 1 according to the present embodiment sets the value of the output light intensity regardless of whether the X axis or the Y axis is deviated while the control device 16 performs processing. It is possible to match the target value.

FIG. 17 shows changes in light intensity with time when the process shown in FIG. 16 is applied to an optical switch having a MEMS mirror device that is driven in two axes. In FIG. 17, the target value is set to -15.2 dBm, and stable operation is realized over several tens of hours. The light intensity in V _t axis at this time is shown in FIG. 18. As shown in FIG. 18, it can be seen that the value of V _t changes even though the light intensity value of the output light is constant. This is because the change in the angle of the mirror over time is compensated. Figure 19 shows a locus of trajectories on V _t axis shown converted to the V _x -V _y plane in Figure 18. At this time, the inclination angle of the V _t axis with respect to the V _y axis is 10 °. Although it can be observed from FIG. 18 that normal PID control is being performed, if the locus on the V _x -V _y plane shown in FIG. 19 is seen, it is simply fixed on the V _x -V _y plane. It can be seen that the target value is tracked while the tilt angle φ of the control axis is reversed as necessary in response to the change in the angle of the mirror over time, instead of controlling the straight line.

Further, a method of PID control on the loss profile with maximum point by using a differential value of the V _t axis in the process shown in FIG. 16 will be described with reference to FIG. 20. Normally, in PID control, a compensation amount proportional to the deviation is added to the control voltage, and the sign at the time of adding is set to be negative feedback. For example, if the light intensity increases by V _t decreases, the deviation becomes larger due to a decrease in the light intensity of the output light, a negative compensation amount as V _t decreases are added. However, if it has a local maximum point is that the V _t than the maximum point light intensity increases by decreasing the V _t is a large area, V _t than maximum point V _t is decreased in a small area As a result, the light intensity also decreases (see arrow f in FIG. 20). Accordingly, in a small space than the maximum point, reducing the V _t in order to compensate for the reduction in light intensity as in the case output light mentioned above, become positive feedback state rather the light intensity is reduced. Therefore, in this embodiment, preventing positive feedback by differential value dP / dV _t of the light intensity of the V _t and the output light back and forth the maximum point to utilize the changes sign.

Specifically, when the compensation voltage amount is Fb, it is possible to avoid falling into positive feedback by adding Fb to V _t according to the following equation (8).

V _t = V _t + (sign of dP / dV _t ) × Fb (8)

Moreover, it is possible to avoid falling into positive feedback by adding Fb to V _t according to the following equation (9).

V _t = V _t + (reference differential value) / (dP / dV _t ) × Fb (9)

In this formula (9), it is possible to avoid positive feedback by setting the reference differential value to a positive value. Further, in this case, due to the shape of the quadratic parallelepiped line, the absolute value of dP / dV _t is small near the maximum point, and the change in the light intensity ΔP of the output light with respect to the feedback amount Fb is small (FIG. 20). It is also possible to correct that (see arrow g). When the value of dP / dV _t is extremely small, it is necessary to prevent the absolute value of “(reference differential value) / (dP / dV _t )” from exceeding the limit value in order to prevent divergence. For the reference differential value, for example, dP / dV _t at an arbitrary voltage V _t may be measured in advance and used.

As described above, according to this embodiment, the values of the voltage V _x and the voltage V _y are calculated using the parameter V _t and applied to the electrodes, so that the mirror rotates around the X axis and the Y axis. Since the output light is simultaneously rotated, the values of the voltage V _x and the voltage V _y at which the light intensity of the output light is equal to or higher than a predetermined value can be searched in a wider range than in the past. Even if a deviation occurs, output light having a desired light intensity can be output.

  In this embodiment, the case where the present invention is applied to an optical switch of 1 × n port has been described as an example. However, the present invention is applicable to various switches as long as it is an optical switch having a mirror device having two rotation axes. Needless to say, it can be done. For example, you may make it apply to the wavelength selective switch 2 which has a 1 * n port by m wavelength as shown in FIG. This wavelength selective switch 2 diffracts input light from one input-side optical fiber 11, n output-side optical fibers 12-1 to 12-n, and input-side optical fiber 11, and has m specific wavelengths. A diffraction grating 31 that generates light, and MEMS mirror devices 13-1 to 13-m that reflect m light beams diffracted by the diffraction grating for each wavelength and output them to corresponding output optical fibers 12-1 to 12-n. A multiplexer 32 that multiplexes the outputs from the output side optical fibers 12-1 to 12 -n, and a demultiplexer 33 for each of m specific wavelengths of light multiplexed by the multiplexer 32, Photodiodes 14-1 to 14-m for monitoring each light demultiplexed by the demultiplexer 33, an A / D converter 15 for A / D converting the detection results of the photodiodes 14-1 to 14m, Based on the output from the A / D converter 15, the MEMS mirror device 13- And a control unit 16 for controlling the driving of ~m. By performing the same processing as that of the optical switch 1 described above on the wavelength selective switch 2 by the control device 16, it is possible to obtain the same effect as that of the optical switch 1.

In the present embodiment, the detection unit 21, the drive voltage update unit 22, the drive voltage output unit 23, the arrival determination unit 24, the change unit 25, and the initial value setting unit 26 cause the light intensity of the output light to be equal to or higher than a predetermined value. Although the values of the voltage V _x and the voltage V _y are calculated, it goes without saying that various configurations can be applied if the values of these voltages are calculated based on the parameter V _t . For example, the control device 16 may be configured by only the detection unit 21, the drive voltage update unit 22, the drive voltage output unit 23, and the initial value setting unit 26. In this case, the values of the voltage V _x and the voltage V _y corresponding to the output-side optical fiber 12 selected by the initial value setting unit 26 are set, and the light intensity of the output light is monitored by the detection unit 21. When the predetermined value is not exceeded, the drive voltage update unit 22 performs the drive voltage update operation described above. As a result, it is possible to search for the values of the voltage V _x and the voltage V _y at which the light intensity of the output light is equal to or higher than a predetermined value in a wider range than before, and as a result, output light having the predetermined light intensity Can be output.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the present embodiment, the configurations of the drive voltage update unit 22 and the change unit 25 of the control device 16 in the first embodiment described above are different. Therefore, in this embodiment, the same components as those in the first embodiment are denoted by the same names and reference numerals, and description thereof will be omitted as appropriate.

In the present embodiment, when the arrival determination unit 24 determines that the target light intensity cannot be reached on the current V _y axis, the change unit 25 searches for the target light intensity on the V _x axis. Change to For example, as shown in FIG. 22, when the angle shift occurs and the drive voltage is in the state indicated by symbol h, the target light intensity is searched for on the straight line along the V _y axis (dotted line i in FIG. 22). Even so, that goal cannot be reached. In this case, as shown in FIG. 23, as a base point the voltage value determines that it can not reach the target, to search for the light intensity of the target with (dotted line j in Fig. 23) linearly along the V _x axis. As a result, it is possible to search for a drive voltage indicated by the symbol k that represents the target light intensity.

  The present invention can be applied to various devices that optimize the light intensity of reflected light by a mirror device having a plurality of rotation axes.

It is a schematic diagram showing a 1 × n port optical switch according to the present invention. It is a block diagram which shows the structure of a control apparatus. It is a flowchart which shows drive voltage setting operation | movement. The light intensity on the V _x -V _y voltage plane is a diagram showing by contour lines. It is a diagram illustrating a parameter V _t. It is a figure explaining the allowable amount of angle deviation. It is a figure explaining the angle shift allowable range of the past and this invention. Is a diagram showing the light intensity on the V _x -V _y voltage plane when there is no angular deviation. Is a diagram showing the light intensity on the V _x -V _y voltage plane when there is angular misalignment. It is a figure explaining the search of the peak of light intensity in FIG. The V _t is a diagram obtained by changing line-symmetrically with respect to V _y axis. The V _t is a diagram obtained by changing line-symmetrically with respect to V _x axis. The V _t is a diagram obtained by rotating angle alpha. It is a figure explaining the method of determining whether light intensity reaches | attains a target value based on the maximum value. It is a figure explaining the method of determining whether light intensity reaches | attains a target value based on a differential value. It is a flowchart which shows the specific example of operation | movement of a control apparatus. It is a figure which shows the specific example of the time change of light intensity. It is a figure which shows the light intensity of the Vt axis _| shaft in FIG. The trajectory of the V _t axis in FIG. 18 is a diagram obtained by converting on V _x -V _y plane. It is a diagram illustrating a PID control using the differential value of the V _t axis. It is a figure which shows the wavelength selective switch which has m wavelength and 1xn port to which this invention is applied. Is a diagram showing the light intensity on the V _x -V _y voltage plane when there is angular misalignment. It is a diagram illustrating a search along the V _x axis in FIG. 22. It is a figure which shows the structure of the spatial optical system optical switch using a MEMS micromirror. It is a figure which shows the structure of a MEMS micromirror. It is a figure which shows the structure of the mirror of a MEMS micromirror, and an electrode. It is a figure which shows the output port selection operation | movement of a spatial optical system optical switch. Is a graph showing the relationship between the voltage V _x and the light intensity P. It is a figure which shows the port coupling rate adjustment operation | movement of a spatial optical system optical switch. It is a figure which shows the relationship between the voltage _Vy and the light intensity P. The light intensity on the V _x -V _y voltage plane is a diagram showing by contour lines. It is a figure explaining the case where light intensity changes to the _Vy axis direction. It is a diagram illustrating a case where the light intensity is changed to V _x-axis direction together with the V _y-axis direction. It is a diagram illustrating a case where the light intensity is greatly changed to V _x-axis direction.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical switch, 2 ... Wavelength selection switch, 11 ... Input side optical fiber, 12-1 to n ... Output side optical fiber, 13 ... MEMS mirror apparatus, 14-1 to n ... Photodiode, 15 ... A / D conversion 16 ... control device 17,18 ... collimating lens, 21 ... detection unit, 22 ... drive voltage update unit, 23 ... drive voltage output unit, 24 ... arrival judgment unit, 25 ... change unit, 26 ... initial value setting unit 31 ... Diffraction grating, 32 ... Multiplexer, 33 ... Demultiplexer.

Claims (4)

At least one light input section for inputting input light;
At least one light output unit for outputting output light;
The mirror has a mirror rotatably supported with respect to the X-axis and a Y-axis different from the X-axis, and a plurality of electrodes arranged to face the mirror. By applying a driving voltage to these electrodes, the mirror is A mirror device tilted at a predetermined angle;
A detection unit for detecting the light intensity of the output light output from the light output unit;
Based on the detection result of the detector, the mirror by calculating the X-axis and the Y axis respectively rotated to cause Ru voltage V _x and the voltage V _y around, the driving voltage to the electrode an optical switch comprising a drive control unit which Ru is selectively outputted from any of the light output section input light input to the predetermined said optical input unit Te,
The drive control unit
A drive voltage update unit that calculates the voltage V _x and the voltage V _y based on a first-order or higher-order polynomial for the parameter V _t ;
When the parameter V _t is changed , the light intensity from the selected light output unit detected by the detection unit is predetermined with respect to the voltage V _x and the voltage V _y calculated based on the polynomial. A determination unit that determines whether or not the value of
When it is determined by the determination unit that the light intensity of the output light does not reach a predetermined value, the parameter V _t ′ at the time when it is determined that it does not reach on the plane having the coordinate axes V _x and V _y is set. The voltage V _x calculated by changing the parameter V _t based on the polynomial with respect to a straight line passing through the corresponding (V _x ′, V _y ′) coordinate and parallel to the coordinate axis of V _x or V _y. And a changing unit for changing the polynomial so that the locus drawn by the V _y is line symmetric.
The optical switch according to claim Rukoto equipped with. At least one light input section for inputting input light;
At least one light output unit for outputting output light;
The mirror has a mirror rotatably supported with respect to the X-axis and a Y-axis different from the X-axis, and a plurality of electrodes arranged to face the mirror. A mirror device tilted at a predetermined angle;
A detection unit for detecting the light intensity of the output light output from the light output unit;
Based on the detection result of the detection unit, a voltage V _x and a voltage V _y for rotating the mirror around the X axis and the Y axis are calculated, and the driving voltage is applied to the electrodes to obtain a predetermined value. A drive control unit that selectively outputs the input light input to the light input unit from any of the light output units;
An optical switch comprising:
The drive control unit
A drive voltage update unit that calculates the voltage V _x and the voltage V _y based on a first-order or higher-order polynomial for the parameter V _t ;
When the parameter V _t is changed , the light intensity from the selected light output unit detected by the detection unit is predetermined with respect to the voltage V _x and the voltage V _y calculated based on the polynomial. A determination unit that determines whether or not the value of
When it is determined by the determination unit that the light intensity of the output light does not reach a predetermined value, the parameter V _t ′ at the time when it is determined that it does not reach on the plane having the coordinate axes V _x and V _y is set. The voltage V _x calculated from the parameter V _t based on the polynomial and the locus drawn by the voltage V _y rotate about a corresponding (V _x ′, V _y ′) coordinate by a predetermined rotation angle. A changing unit for changing the polynomial to
An optical switch, characterized in that it comprises a. The polynomial is
If the parameter is V _t , the drive voltage offsets along the X-axis and Y-axis corresponding to an arbitrary light output unit are V _0x and V _0y , and the constants are A and B (≠ 0), respectively.
V _x = V _0x + A ・ V _t
V _y = V _0y + B ・ V _t
It is represented by these. The optical switch of Claim 1 or 2 characterized by the above-mentioned. The polynomial is
The V _y When the angle of the axis with the linear function and the angle of the V _y when expressed as a linear function of V _x phi on a plane whose coordinate axes of the V _y and the V _x,
V _x = V _0x + V _t · sinφ
V _y = V _0y + V _t · cosφ
The optical switch according to claim 3, wherein:

Images