JP2010091793A - Mechanism and method of controlling optical switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably control optical output power using a MEMS micromirror apparatus having a chevron voltage-loss characteristic. <P>SOLUTION: An adder 11 obtains the deviation of a detected result with respect to a target value, a compensation value calculation part 12 calculates the compensation value with respect to the current voltage on the basis of the deviation, a tilt sign calculation part 13 obtains the sign of the rate of variation in the power with respect to the variation in the voltage at the present voltage, a multiplier 14 and an adder 15 add or subtract compensation value to or from the present voltage according to the sign, a next voltage is calculated by negatively feeding back the deviation to the present voltage, and an electrode voltage transformation part 16 calculates a driving voltage from the next voltage. Thus, the optical output power is automatically controlled so as to achieve a target value without falling down to a positive feedback and without narrowing the variable control range of the optical power, and a stable optical output power control is obtained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a control mechanism and control method for an optical switch used in a communication optical transmission device, a wavelength routing device, and 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 one optical fiber by WDM (Wavelength Division Multiplexing) technology that multiplexes one optical signal corresponding to 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 function of the optical switch is not just switching the path, but the power of the optical signal is adjusted for each path so that the power of the optical signal passing through any path is within a certain range, that is, output. A “power adjustment mechanism” is required as an additional function so that the power deviation of the optical signal is within a certain range regardless of the path. This function, also referred to as “level equivalence”, can increase the number of nodes that can pass through the light, thereby realizing an economical optical network.

  The optical switch has been promoted to have higher functionality as the optical communication network becomes larger. Conventionally, a simple 1 × 2 switch with one input port and two output ports has been used, but in recent years, it has several hundred input ports and output ports and performs optical path control in units of ten thousand units. And a wavelength selective switch that selects an arbitrary wavelength from several tens of wavelengths and outputs the selected wavelength from any of a plurality of output fibers (for example, see Patent Document 1). 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 Documents 1 and 2) created by MEMS (Micro Electro Mechanical Systems) technology is often used. The MEMS micromirror device is a device that applies a voltage to an electrode disposed opposite to a mirror and rotates the mirror around a rotation axis by an electrostatic force generated between the electrode and the mirror. 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 MEMS micromirror device is orthogonal to the first rotation axis. It has been proposed to control light loss by tilting a mirror about a second pivot axis.

As a method for controlling the optical loss to control the optical output power to a desired value (target value), the optical output power is applied to an electrode disposed opposite to the mirror so that the deviation between the target value and the optical output power becomes zero. Feedback control that repeatedly controls voltage is known. Among these, in particular, PID control is proportional control (P control) that returns a voltage proportional to the deviation as a feedback amount, integral control (I control) that returns a voltage proportional to the accumulated value of the deviation as a feedback amount, and time variation of the deviation. It is often used because of its versatility and applicability, which includes differential control (D control) in which a voltage proportional to is returned as a feedback amount.
The case where this PID control is applied to the optical switch using the MEMS micromirror device described above will be described below.

  The wavelength selective switch 100 shown in FIG. 8 diffracts input light from one input-side optical fiber 101, n output-side optical fibers 102-1 to 102-n, and the input-side optical fiber 101, and wavelength. The diffraction grating 103 that generates m light beams having different wavelengths, and m light beams having specific wavelengths diffracted by the diffraction grating 103 are reflected for each wavelength, and the corresponding output side optical fibers 102-1 to 102-102 are reflected. MEMS mirror devices 104-1 to 104-m to be output from -n, a combiner 105 for combining outputs from the output side optical fibers 102-1 to 102-n, and light combined by the combiner 105 to m A demultiplexer 106 for demultiplexing for each specific wavelength, photodiodes 107-1 to 107-m for monitoring each light demultiplexed by the demultiplexer 106, and the photodiodes 107-1 to 107-1 An A / D converter 108 for A / D converting the detection result of 7-m, and a control mechanism for controlling driving of the MEMS mirror devices 104-1 to 104-m based on an output from the A / D converter 108 109.

  In such a wavelength selective switch 100, the mirror of the MEMS mirror device corresponding to an optical signal of a certain wavelength is arranged around the output port selection axis (axis along the arrangement direction of the MEMS mirror device (hereinafter referred to as X axis)). By rotating and coupling to a specific output side port, only an optical signal of a certain wavelength of an optical signal of a maximum m wavelength input from the input side optical fiber 101 is arbitrarily output side optical fibers 102-1 to 102-102. -N can be taken out. If the mirror is rotated around the Y axis orthogonal to the X axis, the light reflected by the mirror changes in a direction orthogonal to the direction in which the output side optical fibers are arranged, and the output side port. Since the coupling shift occurs, the output optical signal can be adjusted without the optical signal leaking to the other output side optical fiber. In each optical fiber of the output side optical fiber, a part of the optical power is branched at a low rate via a coupler, and once merged into one optical fiber by the combiner 105, the demultiplexer 106 performs m It is demultiplexed into optical signals for each wavelength. The demultiplexed optical signals are received by the photodiodes 107-1 to 107-m corresponding to the signals and converted into electric signals, and then the power of the signals is digitized by the A / D converter 108. The The deviation between the digitized optical signal power and the target power is calculated by the control mechanism 109, and the feedback amount corresponding to the deviation is used as an axis for realizing the loss control of the mirror corresponding to the optical signal wavelength. The power of the optical signal can be made constant at the target value by returning to the control voltage that is turned around the signal.

  Next, a mechanism for adjusting the optical output power by changing the coupling ratio with the output optical fiber in the wavelength selective switch 100 described above will be described with reference to FIG.

  When the direction of the light beam emitted from the input side optical fiber 101 into the space is changed by changing the angle of the micro mirror 201 constituting the MEMS mirror devices 104-1 to 104-m, the coupling with the output side optical fiber 102 is performed. The state changes. As a result, the optical power that can be extracted from the output side optical fiber 102 also changes. Therefore, by appropriately controlling the angle of the micromirror 201, an appropriate attenuation factor can be given to the input optical power, and the desired optical power can be extracted from the output side optical fiber 102.

  Electrodes 202 and 203 are provided below the micromirror 201, and two electrostatic forces generated between the micromirror 201 and the electrodes 202 and 203 by applying an appropriate voltage to the two electrodes 202 and 203. The angle of the micromirror 201 can be controlled from the force relationship. Since the angle is determined by the difference between the electrostatic forces generated by the two electrodes 202 and 203, for example, a differential voltage Vd between the electrode voltages applied to the two electrodes 202 and 203 is defined, and the micromirror 201 is used as a function of this Vd. The angle θ can be expressed as θ = θ (Vd). For simplicity, in the following description, the differential voltage is simply referred to as voltage, and the notation is also simply expressed as V instead of Vd.

  The angle of the micromirror 201 is controlled by one voltage V, and the coupling rate of the optical signal whose direction is changed by the micromirror 201 is an optimum angle at which the coupling rate is maximum with respect to the angle of the micromirror 201. It becomes smaller before and after (loss increases). Therefore, the relationship between the voltage V and the coupling rate (or loss) is a mountain profile as shown in FIG. When power control is performed, feedback control is performed so that a desired power is obtained on a curve passing through the mountain profile.

  As described above, for feedback control, a part of the output from the output side optical fiber can be taken out using the coupler 210 and can be calculated using the O / E converter 211 and the A / D converter 212. Then, the data is digitized and input to the control mechanism 109. The control mechanism 109 calculates a deviation between the target value and the digitized optical output power, and calculates a feedback amount from the deviation. As a method for calculating the feedback amount, a method for calculating the feedback amount based on the above-described PID control is generally known. The control mechanism 109 calculates a new voltage by adding the calculated feedback amount to the current voltage V, and applies an electrode voltage corresponding to the new voltage to the electrode. By repeating this process, the deviation is reduced, and the optical output power can be matched with the target value.

Japanese Patent No. 3579015 JP 2007-240728 A Kazuo Hiroi, Akira Miyata, “Introduction to Automatic Control Technology Learned by Simulation”, CQ Publisher, published October 1, 2004

  However, when the coupling rate (or loss) is seen as a function of the voltage V that controls the micromirror, the change of the loss with respect to the voltage, that is, the slope, is bounded by the voltage V at which the coupling rate is maximum (loss is minimum). Positive and negative are reversed. Further, the change (slope) of the loss with respect to the voltage is not constant and changes with the voltage.

  Therefore, when P control is applied to such a function, first of all, there is a risk that the value will diverge from negative feedback control to positive feedback control at the peak at which the loss is lowest. is there.

  Second, since the slope of the function (dL / dV) (L is loss) differs depending on V, even if the same negative feedback amount is given, the amount of loss to be compensated is different if the value of V is different. For this reason, the number of feedbacks required to reach the target depends on V. That is, the “pulling” time until the target value is reached varies depending on the value of V and the target value. In a network system, the time required for switching and power equivalence is usually defined regardless of the value of the target power, so that the convergence time varies depending on the target value.

  Conventionally, in order to deal with the first problem, that is, to avoid positive feedback control, the voltage range to be used is limited to only the left side or the right side of the voltage (referred to as the peak voltage) at which the loss is minimum. However, in the case of a MEMS mirror, due to the phenomenon that the peak voltage changes with time, the initially determined peak voltage does not necessarily match the current peak voltage, and the initially limited voltage range becomes inappropriate over time. There is a problem. This problem is called drift, and there are various factors for the cause. For example, as an electrical factor, as the time during which the voltage is applied elapses, electric charges are charged in the insulator around the electrode, and a change occurs in the electrostatic force to move the mirror. Further, when the ambient temperature changes, thermal expansion and compression of the mirror and the optical member occur, and an optical shift is also a factor of drift.

  This drift is a phenomenon that settles down over time, so it is possible to prevent positive feedback in any case by limiting the voltage range with a margin so that it does not fall into positive feedback even if drift occurs in advance. Is possible. However, in the case of such voltage limitation with a margin, there is a problem that the region near the minimum loss (peak) becomes unusable and the power variable range becomes narrow.

  In order to cope with the second problem, there is a linear approximation, that is, a method in which a voltage range is divided with a slope of a close value and a proportionality constant is optimized for each voltage range. However, in the case of MEMS mirrors, as in the case described above, the relationship between voltage and loss changes with time, so what was initially the optimal division range is not necessarily optimal over time. End up.

  Therefore, an object of the present invention is to realize stable control of optical output power using the MEMS micromirror device having the above-described mountain-shaped voltage-loss characteristics. More specifically, to provide a control mechanism and a control method for an optical switch that automatically controls the optical output power as desired without falling into positive feedback and without narrowing the variable range of optical power adjustment. Objective.

  In order to solve the problems as described above, the control mechanism of the optical switch according to the present invention includes at least one light input unit that inputs input light, at least one light output unit that outputs output light, and rotation. A mirror device that has a mirror that is supported and a plurality of electrodes that are arranged opposite to the mirror, and tilts the mirror at a predetermined angle by applying a drive voltage to these electrodes; An optical switch that includes a detection unit that detects the power of output light, and calculates a drive voltage based on the detection result of the detection unit, and applies the drive voltage to the electrode to tilt the mirror. An adder for obtaining a deviation of the detection result with respect to the target value, a compensation amount calculating unit for calculating a compensation amount for the current voltage based on the deviation output from the adder, and a current A sign detection unit for obtaining a sign of the rate of change of power with respect to a change in voltage in the voltage, and adding or subtracting a compensation amount to the current voltage according to the sign detected by the sign detection unit, thereby obtaining a deviation in the current voltage A compensation voltage calculation unit that calculates a negatively fed back voltage as a next voltage, and a drive voltage calculation unit that calculates a drive voltage from the next voltage obtained by the compensation voltage calculation unit.

  In the optical switch control mechanism, the compensation amount calculation unit calculates a compensation amount including a value obtained by multiplying the compensation amount by at least a parameter, and the parameter has a predetermined rate of change in power with respect to a change in current voltage. If the value is in the range, the reference value of the parameter optimized with the reference voltage may be multiplied by the ratio between the reference voltage value and the absolute value of the current voltage.

  In the control mechanism of the optical switch, the deviation is calculated from the optical output power when the predetermined voltage is applied to the electrode and the target value, the target loss is calculated from the deviation, the voltage with respect to the target loss is calculated, An initial voltage calculation unit that obtains a drive voltage from the voltage and applies the drive voltage to the electrodes may be further provided.

  The optical switch control method according to the present invention includes at least one light input unit for inputting input light, at least one light output unit for outputting output light, a mirror that is rotatably supported, and the mirror. And a mirror device that tilts the mirror at a predetermined angle by applying a driving voltage to these electrodes, and detection that detects the power of the output light output from the light output unit A driving voltage is calculated on the basis of a detection result of the detection unit, and the driving voltage is applied to the electrode to tilt the mirror. An addition step for obtaining a deviation of the detection result with respect to the current value, a compensation amount calculation step for calculating a compensation amount for the current voltage based on the deviation output by the addition step, A sign detection step for obtaining the sign of the rate of change of power with respect to a change in voltage, and adding or subtracting the compensation amount to the current voltage according to the sign detected by this sign detection step, and negatively feeding back the deviation to the current voltage A compensation voltage calculating step for calculating the calculated voltage as a next voltage, and a driving voltage calculating step for calculating a driving voltage from the next voltage calculated in the compensation voltage calculating step.

  According to the present invention, the deviation of the detection result with respect to the target value is obtained, the compensation amount for the current voltage is calculated based on the deviation, the sign of the rate of change in power with respect to the change in voltage at the current voltage is obtained, and the sign Depending on the current value, the compensation amount is added to or subtracted from the current voltage, the voltage obtained by negatively feeding back the deviation to the current voltage is calculated as the next voltage, and the drive voltage is calculated from the next voltage, thereby providing positive feedback. It is possible to automatically control the optical output power so as to achieve the target without narrowing the optical power adjustment variable range, and to realize stable control of the optical output power.

[First Embodiment]
Hereinafter, a first embodiment according to the present invention will be described in detail with reference to the drawings. The optical switch control mechanism according to the present embodiment corresponds to the optical switch control mechanism 109 described with reference to FIGS. Therefore, in the present embodiment, the same components as those of the optical switch already described with reference to FIGS. 8 and 9 are denoted by the same names and reference numerals, and the description thereof is omitted as appropriate.

<Configuration of control mechanism>
As shown in FIG. 1, an optical switch control mechanism 1 according to the present embodiment includes an adder 11 that calculates a deviation between an optical output power and a target value in order to execute normal PID control, and the adder. Compensation amount calculation unit 12 that calculates a feedback amount from the deviation calculated by 11, Pow indicating the value of optical output power, PrevPow indicating the previous value of this optical output power Pow, voltage V, and the previous time of this voltage V The slope is calculated from four variables PrevV indicating the voltage value of the current, the slope code calculation unit 13 extracts the sign of the slope, the code calculated by the slope code calculation unit 13 and the compensation amount calculation unit 12 A multiplier 14 that multiplies the feedback amount, an adder 15 that subtracts the feedback amount output from the multiplier 14 from the current voltage V, and a new voltage V output from the adder 15 is physically obtained. The electrode voltage converter 16 to be applied to convert the voltage (electrode voltage) to the electrodes 202 and 203, and a timer 17 for measuring a predetermined control period [Delta] T. Here, the previous optical output power PrevPow is calculated based on the optical output power Pow by a delay unit -ΔT18 that adds a delay of one cycle from the current value. Similarly, the previous voltage PrevV is calculated based on the voltage V by a delay unit −ΔT19 that adds a delay of one cycle from the current value.

  Such a control mechanism 1 includes an arithmetic device such as a CPU, a RAM, a ROM, and the like, and includes a storage device that stores an operation program, various data, and the like, and performs an operation based on the program. , The hardware resources described above may be controlled by a program, and the above-described components may be realized. Further, it may be realized using a programmable logic circuit such as FPGA, which is an intermediate method between software and hardware, or may be realized as hardware as an IC.

<Operation of control mechanism>
Next, the operation of the control mechanism 1 according to the present embodiment will be described with reference to FIG.

  First, the control mechanism 1 initializes related variables (step S1). Here, the variable for storing the previous value and the slope dP / dV for determining whether the variable is in the negative region or the positive region are also initialized. Specifically, for example, in the case of the gradient dP / dV, dP / dV = 0 is set.

Next, as a preparation before performing feedback control, the control mechanism 1 applies an electrode voltage converted from the initial voltage value V ₀ to the electrodes 202 and 203 and observes the value P ₀ of the optical power at this time. Thereafter, these values are copied to a variable for storing the previous value (step S2). Specifically, when the optical output power Pn is acquired by applying the initial value of the voltage Vn, V _n−1 = V _n and P _n−1 = P _n are set. Here, n represents the current value and n-1 represents the previous value.

  Next, the control mechanism 1 executes feedback control and repeats the feedback control loop of steps S3 to S11 until a stop command is issued in step S12. For the stop command, for example, a logical variable for a stop flag is provided in advance, and the stop flag is set to False (not stop) at the time of initialization. When a stop event is executed by the user or the like, this stop flag variable is changed to True (stop). In step S12, it is confirmed whether the stop flag is True or False. If True, the process exits the loop and stops, and if False, the feedback control loop is continued.

  In the feedback control loop, first, the timer 17 measures the time, and the control loop time Δt elapses (step S3). At this time, the next step or the like is not executed.

Next, the adder 11 calculates the target value Pt and the current deviation e _n is the difference between the current power Pn (step S4). The deviation e _n is calculated by the following equation (1).

e _n = P _t −P _n (1)

Then, the compensation amount calculation unit 12 uses the deviation e _n calculated by the adder 11, proportional control, integral control, and calculates the feedback amount MV for derivative control (step S5). Specifically, the feedback amount MV _p for proportional control is expressed by the following equation (2), the feedback amount MV _i for integral control is expressed by the following equation (3), and the feedback amount MV _d for differential control is expressed by the following equation (4). feedback amount MV for the deviation e _n based on the amount is calculated by the following equation (5). Here, kp means a proportionality constant.

_{MV p = kp * e n ···} (2)
_{MV in = MV in-1 +} kp * e n * Δt / Ti ··· (3)
_{MV d = kp * (e n} -e n-1) * Td / Δt ··· (4)
MV = MV _p + MV _in + MV _d (5)

Next, before returning the MV calculated by the compensation amount calculation unit 12 to the control voltage, the gradient sign calculation unit 13 calculates the gradient dP / dV, and the sign of dP / dV is negative or dP / dV is 0. Whether or not (step S6). When the sign of dP / dV is negative or dP / dV is 0 (step S6: YES), the multiplier 14 and the adder 15 subtract MV from the previous voltage V _n−1 and then apply the next voltage. Vn is calculated (step S7). On the other hand, when the sign of dP / dV is positive (step S6: NO), the multiplier 14 and the adder 15 calculate the voltage Vn to be applied next after adding MV to the previous voltage Vn _-1. (Step S8).

  When the voltage Vn to be applied is determined, the control mechanism 1 causes the electrode voltage conversion unit 16 to convert the voltage Vn into an electrode voltage that is actually applied to the electrodes 202 and 203, and causes this to be applied to the electrodes 202 and 203. The power Pn of the output light at this time is acquired (step S9).

When the optical output power P _n is acquired, the inclination code calculation unit 13 uses the acquired P _n , the current V _n , the previous P _n−1 and V _n−1 to calculate the inclination dP / dV is calculated (step S10).

dP / dV = (P _n −P _n−1 ) / (V _n −V _n−1 ) (6)

  When the slope dP / dV is calculated, each value is copied to a variable holding the previous value for the next calculation (step S11). Specifically, as shown by the following formulas (7) to (10), the current value is replaced with a variable. When the value is replaced in this way, the process proceeds to step S12.

P _n-1 = P _n (7)
V _n-1 = V _n (8)
e _n-1 = e _n (9)
MV _in-1 = MV _in (10)

As shown in FIG. 3, the sign of the slope is inverted at the peak of the voltage-loss profile (the point at which the loss is minimized), and is negative in the area on the right side of the peak and positive in the area on the left side of the page. I understand that DP / dV shown in Equation (6) is the slope of a straight line connecting the white point indicated by symbol a and the black point indicated by symbol b in FIG. 3, and the difference between V _n and V _n−1 extends over both regions. By taking an appropriate size so that there is not, the sign of dP / dV matches the sign of the slope at V _n . Therefore, if the sign of feedback is changed and added to V _n based on the sign of dP / dV, negative feedback and positive feedback appearing on the left and right of the peak in the past will be made negative feedback in either region. Can do.

  As described above, according to the present embodiment, the adder 11 calculates the deviation of the detection result with respect to the target value, and the compensation amount calculation unit 12 calculates the compensation amount for the current voltage based on the deviation. The slope code calculation unit 13 obtains the sign of the power change rate with respect to the voltage change at the current voltage, and the multiplier 14 and the adder 15 add or subtract the compensation amount to the current voltage according to the sign. Thus, the voltage obtained by negatively feeding back the deviation to the current voltage is calculated as the next voltage, and the electrode voltage conversion unit 16 calculates the drive voltage from the next voltage. As a result, it is possible to automatically control the optical output power as desired without falling into positive feedback and without narrowing the optical power adjustment variable range, thereby realizing stable optical output power control. it can.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described. In this embodiment, an initial voltage calculator 20 is further added to the control mechanism 1 according to the first embodiment described above. Therefore, in the present embodiment, the same names and symbols are assigned to the same components as those in the first embodiment, and the description thereof is omitted as appropriate.

<Configuration of control mechanism>
As shown in FIG. 4, the control mechanism 2 according to the present embodiment includes an adder 11, a compensation amount calculation unit 12, an inclination code calculation unit 13, a multiplier 14, an adder 15, and an electrode voltage conversion. Unit 16, timer 17, delay unit −ΔT 18, delay unit −ΔT 19, and initial voltage calculation unit 20.

  The initial voltage calculation unit 20 calculates a deviation from the current optical output power and a target value, calculates a target loss from the deviation, calculates a voltage with respect to the target loss, and outputs this as an initial voltage.

Here, the initial voltage calculation unit 20 measures the voltage-loss characteristics as shown in FIG. 5 in advance using an optical switch to be controlled, and tabulates or approximates the voltage with respect to the loss based on this result. Make it a function and save it in memory. The reason why the voltage-loss characteristic is used instead of the voltage-optical output power characteristic is that the optical output power depends on the input power. For this reason, if the input power when the relationship between the voltage and the optical output power is measured in advance is different from the input power when the optical switch is currently used, the voltage-optical output power characteristic changes. However, since the voltage-loss characteristic does not depend on the input power, the voltage-loss characteristic itself does not change even if the input power changes. Further, the loss with respect to the target power cannot be obtained only from the voltage-loss characteristics. In order to determine the loss, it is necessary to estimate the input power. Therefore, in the present embodiment, a voltage that causes a specified loss (ATTTest) is applied once before the start of PI control. By measuring the optical output power (Pout) at this time, the current input power (Pin) can be estimated as Pin = Pout + ATTest. By using these values, the loss (ATTTarget) with respect to the target power (Ptarget) can be obtained as ATTarget = Pin−Ptarget = Pout + ATTest−Ptarget. Furthermore, the voltage with respect to the estimated loss is calculated using voltage-loss characteristics. The calculated initial voltage is converted into an electrode voltage using the electrode voltage conversion unit 16 and then applied to the electrodes 202 and 203 of the micromirror 201. In this way, the power P ₀ immediately before starting the PI control is a value very close to the target value Ptaget (in principle, the state of the optical switch when the voltage-light output characteristic is evaluated, and the current Therefore, the PI control only needs to eliminate a relatively small deviation. Thereby, the dispersion | variation in drawing-in time can be made small.

<Operation of control mechanism>
Next, the operation of the control mechanism 2 according to the present embodiment will be described with reference to FIG. In the present embodiment, the case where operation is performed by PI control without using D control will be described as an example, but it goes without saying that D control may also be used.

  First, the control mechanism 2 initializes related variables. Here, the inclination dP / dV is also initialized (step S21). Specifically, for example, in the case of the gradient dP / dV, dP / dV = 0 is set.

Next, the control mechanism 2 acquires the voltage V ₀ corresponding to the target power from the voltage-loss table based on the voltage-loss characteristics as shown in FIG. 5 as a preparation before entering the feedback control (step S22).

Next, the control mechanism 2 applies the voltage V _n = V ₀ acquired from the voltage-loss table to the electrodes 202 and 203, observes the value P ₀ of the optical power at this time, and then sets these values last time. Is copied to a variable to store (step S23).

  Next, the control mechanism 2 executes feedback control, and repeats the feedback control loop of steps S24 to S32 until a stop command is issued in step S33. The stop command is issued by the same method as described in the first embodiment.

  In the feedback control loop, first, the time is measured by the timer 17 and the control loop time Δt elapses (step S24). At this time, the next step or the like is not executed.

Next, the adder 11 calculates the target value Pt and the current deviation e _n is the difference between the current power Pn (step S25). The deviation e _n is calculated by the above equation (1).

Then, the compensation amount calculation unit 12 uses the deviation e _n calculated by the adder 11, calculates a feedback amount MV for proportional control and integral control (step S26). In this embodiment, the calculation of the feedback amount, unlike the conventional PI control, is calculated by a function of the proportionality constant kp as a function kp of V _n (V _n).

When V _n falls within a certain voltage range −Vref to Vref, it is determined that the number of pull-in times is taken because it is in the vicinity of the peak, and the pull-in is accelerated using kp (V _n ) shown in the following equation (10). To do. Here, kp0 is a proportionality constant when optimized at V _n = Vref (reference voltage).

kp (V _n ) = kp 0 * Vref / | V _n | (10)

However, when V _n is close to 0, the value of Vref / | V _n | becomes very large, so that the value of kp (V _n ) also becomes excessively large. In order to prevent this, when the value of Vref / | V _n | becomes larger than the limit value VRateMax, the following equation (11) is used instead of the above equation (10).

kp (V _n ) = kp0 * VrateMax (11)

In the case of V _n <−Vref or V _n > Vref, the conventional PI control is used because it is in a region away from the peak. That is, as shown in the following expression (12), kp is not a function of Vn but is treated as a constant.

kp (V _n ) = kp0 (12)

In the above equation (10), kp (V _n ) is a −1 power function of V _n , but this is based on the voltage V in the vicinity of the peak as shown in FIG. This is because the relationship between the power P can be approximated to a quadratic function of P 関 数 V ² and V. Therefore, the slope near the peak is proportional to V as a differential value of the quadratic function as shown in the following equation (13).

dP / dV = −AV (13)

Here, -A is a quadratic coefficient when power is approximated by a quadratic function of voltage. From this equation (13), the closer the V is to the origin, the smaller the slope, so the closer to the origin, the smaller the change in power for the same feedback amount MV. Therefore, as shown in the above equation (10), the parameter kp (V _n ) used when obtaining the feedback amount MV is optimized to kp0 (reference value), Vref (reference voltage value), and V _n (reference value). a value multiplying the reciprocal of the absolute value of the current voltage value) (in other words, the Kp0, absolute value to a value multiplied by the ratio of) that at the Vref and V _n, independently of the V, the same have the same power change amount when compensation for the deviation e _n. For this reason, the expression (10) can be applied only when the power is expressed in dBm. When displayed in watts (usually the optical power is expressed in mW), it is necessary to convert to dBm display using the following equation (14).

P [dBm] = 10 log (P [mW]) (14)

  In the above example, the case where there is a peak at which the loss is minimum at the origin (V = 0) has been described. However, when the peak is not at the origin but at V = Vpeak, V-Vpeak is defined as a new voltage. Thus, it goes without saying that the above-described method can be applied if the translation is performed in parallel with the origin.

Therefore, the feedback amount MV _p is the formula for proportional control (15), the feedback amount MV _i represents the following formula for the integral control (16), the feedback amount MV is the formula for the deviation e _n based on these feedback amount (17) Calculated.

_{MV p = kp (V n)} * e n ··· (15)
_{MV in = MV in-1 +} kp (V n) * e n * Δt / Ti ··· (16)
MV = MV _p + MV _in (17)

  Subsequent steps S27 to S32 are equivalent to steps S6 to S11 described in the first embodiment.

  Thus, according to the present embodiment, the initial voltage calculation unit 20 calculates a deviation from the optical output power and the target value, calculates a target loss from the deviation, calculates a voltage with respect to the target loss, Can be automatically controlled to achieve the target optical output power without falling into positive feedback, narrowing the optical power adjustment variable range, and stable light output. Power control can be realized.

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

It is a figure which shows typically the structure of the control mechanism of the optical output power which concerns on this invention. It is a flowchart which shows operation | movement of the control mechanism of optical output power. It is a figure which shows the profile of voltage-light output power. It is a figure which shows typically the structure of the control mechanism of the other optical output power which concerns on this invention. It is a figure which shows the profile of a voltage-loss characteristic. 6 is a flowchart showing the operation of the optical output power control mechanism shown in FIG. It is a figure which shows the profile of voltage-light output power. It is a figure which illustrates the structure of a wavelength selective switch typically. It is a figure which illustrates typically the mechanism which adjusts optical output power. It is a figure which shows the profile of a voltage-loss characteristic.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2 ... Control mechanism of optical switch, 11 ... Adder, 12 ... Compensation amount calculation part, 13 ... Sign calculation part, 14 ... Multiplier, 15 ... Adder, 16 ... Electrode voltage conversion part, 17 ... Timer, 18 , 19... Delay unit-.DELTA.T, 20... Initial voltage calculation unit.

Claims (4)

At least one light input section for inputting input light;
At least one light output unit for outputting output light;
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 detection unit that detects the power of the output light output from the light output unit, the drive voltage is calculated based on a detection result of the detection unit, and the drive voltage is calculated as the electrode. A control mechanism of an optical switch that is applied to and tilts the mirror,
An adder for obtaining a deviation of the detection result with respect to a target value;
A compensation amount calculation unit for calculating a compensation amount for the current voltage based on the deviation output from the adder;
A sign detection unit for obtaining a sign of a rate of change of the power with respect to a change in voltage at a current voltage;
A compensation voltage calculation unit that adds or subtracts the compensation amount to the current voltage according to the code detected by the code detection unit, and calculates a voltage obtained by negatively feeding back the deviation to the current voltage as a next voltage. When,
And a drive voltage calculation unit that calculates the drive voltage from the next voltage obtained by the compensation voltage calculation unit. The compensation amount calculation unit calculates the compensation amount including a value obtained by multiplying the compensation amount by a parameter with respect to the compensation amount,
When the rate of change of the power with respect to the current voltage change is a value within a predetermined range, the parameter includes the reference voltage value optimized by the reference voltage and the reference voltage value and the current voltage. The optical switch control mechanism according to claim 1, comprising a value obtained by multiplying a ratio with an absolute value. Calculate the deviation from the optical output power when the predetermined voltage is applied to the electrode and the target value, calculate the target loss from this deviation, calculate the voltage for this target loss, and determine the drive voltage from this voltage, The optical switch control mechanism according to claim 1, further comprising: an initial voltage calculation unit that applies the drive voltage to the electrodes. At least one light input section for inputting input light;
At least one light output unit for outputting output light;
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 detection unit that detects the power of the output light output from the light output unit, the drive voltage is calculated based on a detection result of the detection unit, and the drive voltage is calculated as the electrode. A method of controlling an optical switch that tilts the mirror when applied to the mirror,
An adding step for obtaining a deviation of the detection result with respect to a target value;
A compensation amount calculating step for calculating a compensation amount for the current voltage based on the deviation output by the adding step;
A sign detection step for obtaining a sign of the rate of change of the power with respect to a change in voltage at a current voltage;
Compensation voltage calculating step of adding or subtracting the compensation amount to or from the current voltage according to the code detected by the code detecting step and calculating a voltage obtained by negatively feeding back the deviation to the current voltage as a next voltage When,
And a driving voltage calculating step of calculating the driving voltage from the next voltage calculated in the compensation voltage calculating step.

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