JP4932539B2 - Optical interferometer control circuit - Google Patents

Description

  The present invention relates to adjustment of a filter optical frequency of a Mach-Zehnder type, AWG, or ring type optical interferometer used as an optical filter.

As an optical filter, a Mach-Zehnder type AWG (Arrayed) that uses light interference
Waveguide gratings or ring type optical interferometers are known. In such an optical interferometer, a resistor formed on at least a part of the optical waveguide is used as a heater, and the refractive index of the optical waveguide is changed by heat generated by supplying electric power to the heater. The filter optical frequency can be shifted.

  FIG. 6 is a block diagram showing a conventional example, showing an example of controlling the filter optical frequency of a Mach-Zehnder optical interferometer (hereinafter referred to as MZI). The heater 2 is provided in the MZI 1, and the filter optical frequency of the MZI 1 is controlled by supplying a current (or voltage) corresponding to a control voltage from the outside to the heater 2 from the heater driving circuit 3. In the example of FIG. 6, the control voltage is generated by the control voltage generation circuit 5 under the control of the microprocessor 4.

Patent 3320172

  Since the electric power consumed by the heater is the square of the current × the resistance value, the manufacturing variation of the resistance value of the heater directly affects the control accuracy. Further, when the resistance value of the heater is excessive, there is a risk of exceeding the rated power of the heater. For this reason, conventionally, the resistance value of the heater is recorded in advance, and the control voltage or the heater drive signal is corrected in accordance with the resistance value. For example, Patent Document 1 describes that the heater resistance value is recorded and the power supplied to the heater is controlled according to the detected voltage value, although the application is different. However, in this method, it is necessary to individually measure and record the resistance value of the heater, and there is a problem in mass-producing the control circuit.

  The present invention provides a control method and a control circuit for an optical interferometer capable of solving such problems and supplying power corresponding to a control voltage by absorbing fluctuations in the resistance value of the heater. Objective.

According to the perspective of the present invention, in a control circuit for controlling the transmitted light frequency of the optical interferometer by heat generation of the heater formed on the optical waveguide of the optical interferometer, which corresponds to a control voltage input as a control signal power There is provided an optical interferometer control circuit comprising power control means for controlling the power consumed by the heater so that is supplied to the heater.

  The power control means includes means for obtaining a resistance value of the heater from a current flowing through the heater and a potential difference between both ends of the heater, and means for adjusting a voltage or current supplied to the heater based on the resistance value. Can be included.

  Specifically, a heater drive circuit that supplies a drive current corresponding to the input voltage to the heater is provided, and the means for obtaining the resistance value includes a voltage measurement circuit for obtaining a potential difference between both ends of the heater, and the voltage measurement. A resistance value calculating circuit for calculating a resistance value from a potential difference obtained by the circuit and a driving current value of the heater driving circuit, wherein the adjusting means inputs the control voltage to the heater driving circuit with a variable gain. It is desirable to include a variable gain amplifier and a gain adjustment circuit that adjusts the gain of the variable gain amplifier based on the calculated resistance value of the calculating means. In this case, it is preferable that the drive current value of the heater drive circuit is obtained from the value of the control voltage and the gain of the variable gain amplifier.

  Means for obtaining the power consumption of the heater from the current flowing through the heater and the potential difference across the heater, and means for adjusting the voltage or current supplied to the heater based on the power consumption.

  Specifically, a heater drive circuit that supplies a drive current corresponding to the input voltage to the heater is provided, and the means for obtaining the power consumption includes a current measurement circuit that measures the drive current flowing through the heater drive circuit, and A voltage measuring circuit for obtaining a potential difference between both ends of the heater; and a power calculating circuit for calculating a power value from a driving current value measured by the current measuring circuit and a potential difference measured by the voltage measuring circuit, and the means for adjusting Includes a variable gain amplifier that inputs the control voltage to the heater drive circuit with a variable gain, and a correction value calculation circuit that adjusts the gain of the variable gain amplifier based on the power value calculated by the power calculation circuit. Is desirable. In this case, the current measuring circuit is a resistance in the heater driving circuit, and is connected in series with the heater to measure a potential difference between both ends of the resistor whose resistance value is known. A current calculation circuit for calculating a current value flowing through a resistor whose resistance value is known from a measured value.

  In order to absorb the fluctuation of the heater resistance value which is a conventional problem in the frequency shift control of the optical interferometer, the power consumed by the heater is directly controlled so that the power corresponding to the control voltage is supplied to the heater. As a result, it is possible to suppress the current at a high resistance and increase the current at a low resistance without measuring the heater resistance value in advance, thereby absorbing variations in the heater resistance value. Further, by defining the upper limit of the amount of power to be applied, the risk of exceeding the allowable power of the heater can be eliminated. According to the present invention, a process of actually measuring and recording the heater resistance value is not necessary, and a control circuit with high productivity can be realized.

  FIG. 1 is a block diagram for briefly explaining an embodiment of the present invention. Here, a case where MZI is used as an optical interferometer will be described as an example.

  A heater 2 is provided on at least one of the branched optical waveguides of the MZI 1, and the refractive index of the optical waveguide is changed by heat generated by supplying electric power to the heater 2, and the filter light has a magnitude proportional to the electric power. The frequency shifts. The amount of shift of the filter optical frequency is set by a control voltage input as a control signal from the control voltage generation circuit 5. In the embodiment shown in FIG. 1, electric power corresponding to the control voltage from the control voltage generation circuit 5 is applied to the heater 2. A constant power control circuit 6 for controlling the power consumed by the heater 2 is provided so as to be supplied. Here, “constant power control” does not mean that constant power is always maintained, but means that constant power is controlled to 1: 1 with respect to the control voltage.

  The constant power control is performed by actually detecting the resistance value of the heater 2 or by measuring the power actually consumed by the heater 2. Specific examples will be described below.

  FIG. 2 is a block diagram showing the first embodiment of the present invention. In this embodiment, a resistance value measuring circuit 11 for obtaining a resistance value of the heater 2 from a current flowing through the heater 2 and a potential difference between both ends of the heater 2 and a voltage or current supplied to the heater 2 based on the resistance value are adjusted. For this reason, a gain adjustment circuit 12 and a variable gain amplifier 13 for correcting the control voltage supplied from the control voltage generation circuit 5 to the heater drive circuit 3 are provided.

  As the heater drive circuit 3, a voltage-current conversion circuit that outputs a predetermined current with respect to an input voltage value is used, and the current flowing through the heater 2 can be obtained from the output voltage of the variable gain amplifier 13 by calculation. Therefore, the resistance value measurement circuit 11 can determine the resistance value of the heater 2 by measuring the potential difference between both ends of the heater 2. The gain of the variable gain amplifier 13 is adjusted according to the resistance value, the control voltage supplied from the control voltage generation circuit 5 to the heater drive circuit 3 is adjusted, and the power consumed by the heater 2 is adjusted.

  FIG. 3 is a block diagram for explaining this embodiment in more detail. The heater drive circuit 3 is configured to output a constant current with respect to the input voltage by controlling the current flowing through the internal resistor R3, which is connected in series with the heater 2 and whose resistance value is known, according to the input voltage. ing. The variable gain amplifier 13 is configured as a non-inverting amplifier having an input resistance value R1 to the non-inverting input, a resistance value R1 between the inverting input and the ground point, and a feedback resistance value R1 + Rv between the output and the inverting input. The gain is G = 1 + Rv. Further, a voltage measurement circuit 111 and a resistance value calculation circuit 112 are provided as circuits corresponding to the resistance value measurement circuit 11 shown in FIG.

  In this configuration, the output voltage of the variable gain amplifier 13 is GVc with respect to the control voltage Vc from the control voltage generation circuit 5, and the output current of the heater drive circuit 3 is calculated as I = GVc / R3. The resistance value Rh of the heater 2 is obtained by measuring the potential difference Vm between both ends of the heater 2 by the voltage measuring circuit 111 and calculating (Vm / GVc) × R3 by the resistance value calculating circuit 112. In accordance with this value, the gain adjustment circuit 12 adjusts the gain of the variable gain amplifier 13.

  The gain G of the variable gain amplifier 13 may be determined in the initial state where the control is started, or may be controlled so that the gain is always optimum. In the former case, the control is simple, but the gain determined at the start of the control is maintained thereafter, and it is not possible to cope with a change in resistance value or a change with time due to the heat of the heater 2. In the latter case, the response speed of the feedback loop for controlling the gain can be designed to respond faster than the heater control loop, so that it is possible to cope with a change in resistance value and a change with time due to heat.

  When determining the gain G of the variable gain amplifier 13 at the start of control, the gain G is configured so that the initial value of the gain G is 1, and the gain thereafter is determined based on the resistance value Rh calculated in that state. It is desirable to determine G.

  FIG. 4 is a block diagram showing the second embodiment of the present invention. In this embodiment, a current measurement circuit 21 that measures the drive current flowing through the heater 2, a voltage measurement circuit 22 that measures the potential difference between both ends of the heater 2, and a power calculation circuit 23 that determines the power consumption of the heater 2 from these measured values are provided. And a feedback control circuit 24 for correcting the control voltage supplied from the control voltage generation circuit 5 to the heater drive circuit 3 in order to adjust the voltage or current supplied to the heater 2 based on the power consumption. .

  FIG. 5 is a block diagram for explaining this embodiment in more detail. The configuration of the heater drive circuit 3 is the same as that shown in FIG. 3, and a voltage measurement circuit 211 that measures the potential difference between both ends of the internal resistance R3 of the heater drive circuit 3 as a circuit corresponding to the current measurement circuit 21 of FIG. And a current calculation circuit 212 that calculates the value of the current flowing through the internal resistor R3 from the measurement value of the voltage measurement circuit 211. Further, as a circuit corresponding to the feedback control circuit 24 of FIG. 4, a variable gain amplifier 242 that inputs the control voltage from the control voltage generation circuit 5 to the heater driving circuit 3 with a variable gain, and the gain of the variable gain amplifier 242 is set to the power. And a correction value calculation circuit 241 that adjusts based on the power value calculated by the arithmetic circuit 23.

  The internal resistance R3 of the heater drive circuit 3 is connected in series with the heater 2, and its resistance value is known. Therefore, the value of the current flowing through the heater 2 through the internal resistance R3 is obtained from I = Vr3 / R3 from the potential difference Vr3 across the internal resistance R3. Furthermore, the actual power consumption of the heater 2 is obtained in the power calculation circuit 23 from the current value I and the measurement value of the voltage measurement circuit 22. A correction value is calculated by the correction value calculation circuit 241 in accordance with the power consumption value, and the gain of the variable gain amplifier 242 is adjusted.

  In the above embodiments, the case where MZI is used as an optical interferometer has been described as an example. However, the present invention can be similarly used in an optical interferometer of AWG or ring type.

The block block diagram which illustrates embodiment of this invention simply. The block block diagram which shows the 1st Example of this invention. The block block diagram explaining this Example further in detail. The block block diagram which shows the 2nd Example of this invention. The block block diagram explaining this Example further in detail. The block block diagram which shows a prior art example.

Explanation of symbols

1 MZI
2 Heater 3 Heater drive circuit 4 Microprocessor 5 Control voltage generation circuit 6 Constant power control circuit 11 Resistance value measurement circuit 12 Gain adjustment circuit 13 Variable gain amplifier 111 Voltage measurement circuit 112 Resistance value calculation circuit 21 Current measurement circuit 22 Voltage measurement circuit 23 Power calculation circuit 24 Feedback control circuit 211 Voltage measurement circuit 212 Current calculation circuit 241 Correction value calculation circuit 242 Variable gain amplifier

Claims (4)

In a control circuit for controlling the transmitted light frequency of the optical interferometer by the heat generated by the heater (2) formed on the optical waveguide of the optical interferometer,
Power control means for controlling power consumed by the heater (2) so that power corresponding to a control voltage input as a control signal is supplied to the heater (2) ;
A heater drive circuit (3) for supplying a drive current corresponding to the input voltage to the heater (2);
With
The power control means includes means (11) for obtaining a resistance value of the heater (2) from a current flowing through the heater (2) and a potential difference between both ends of the heater (2), and the heater (2) based on the resistance value. 2) means for adjusting the voltage or current supplied to (12, 13),
The means (11) for obtaining the resistance value includes a voltage measurement circuit (111) for obtaining a potential difference between both ends of the heater (2), a potential difference obtained by the voltage measurement circuit (111), and the heater driving circuit (3). A resistance value calculation circuit (112) for calculating a resistance value from the drive current value of
The means (12, 13) for adjusting the voltage or current includes a variable gain amplifier (13) for inputting the control voltage to the heater drive circuit (3) with a variable gain, and a gain of the variable gain amplifier (13). A control circuit for an optical interferometer , comprising: a gain adjustment circuit (12) that adjusts based on the resistance value calculated by the resistance value calculation circuit (112) . The control circuit of the optical interferometer of claim 1, wherein obtaining from the gain of the value of said control voltage driving current variable gain amplifier (13) of the heater drive circuit (3). In a control circuit for controlling the transmitted light frequency of the optical interferometer by the heat generated by the heater (2) formed on the optical waveguide of the optical interferometer,
Power control means for controlling power consumed by the heater (2) so that power corresponding to a control voltage input as a control signal is supplied to the heater (2);
Means (21, 22, 23) for obtaining power consumption of the heater (2) from a current flowing through the heater (2) and a potential difference between both ends of the heater (2);
Means (24) for adjusting the voltage or current supplied to the heater (2) based on its power consumption;
A heater drive circuit (3) for supplying a drive current corresponding to the input voltage to the heater (2);
With
The means (21, 22, 23) for determining the power consumption includes a current measurement circuit (21) for measuring the drive current flowing through the heater drive circuit (3), and a voltage measurement for determining a potential difference between both ends of the heater (2). A circuit (22), and a power calculation circuit (23) that calculates a power value from the drive current value measured by the current measurement circuit (21) and the potential difference measured by the voltage measurement circuit (22),
The adjusting means (24) includes a variable gain amplifier (242) for inputting the control voltage to the heater driving circuit (3) with a variable gain, and a gain of the variable gain amplifier (242) to the power calculation circuit (23). And a correction value calculation circuit (241) that adjusts based on the calculated power value.
An optical interferometer control circuit. The current measurement circuit (21) is a resistance in the heater drive circuit (3), which is connected in series with the heater (2) and has a resistance value that measures a potential difference between both ends of a known resistance ( and 211), the control circuit of the optical interferometer of claim 3, wherein said resistance value from the measured values comprises a current calculation circuit (212) for calculating a current flowing through the known resistance of the voltage measuring circuit (211).

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