JP2013088702A - Optical modulator drive controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique that allows for providing appropriate bias control for any drive signal amplitudes.SOLUTION: A drive controller 100 for an optical modulator 2 includes a peak detector 5 for acquiring a peak detection output signal which represents a waveform peak of an electrical signal corresponding to an optical signal from the optical modulator 2, an oscillation circuit 6 for generating an oscillation signal, and a synchronous detection section 7 for performing synchronized detection based on the peak detection output signal and the oscillation signal. The drive controller 100 also includes a bias setting section 8 for generating a control signal for controlling the bias relating to the modulation by the optical modulator 2 based on the result of the synchronous detection, an adder 10b for adding the oscillation signal to the control signal, an amplifier 11 for generating a drive signal by amplifying a data signal based on predetermined signals including the oscillation signal.

Description

  The present invention relates to a drive control device that performs drive control on an optical modulator that generates an optical signal by modulating light emitted continuously from a light source.

  As a modulation method of an optical communication system, a direct modulation method that generates an optical signal having an intensity proportional to an electrical signal by outputting an optical signal corresponding to a drive current to a semiconductor laser such as a laser diode is known. Yes. This direct modulation method has the advantage that the device configuration is very simple. However, if an ultra-high speed / broadband optical communication with a transmission rate exceeding several Gbit / s is performed using this method, the modulation is performed. There is a problem that a wavelength fluctuation (chirping) phenomenon in which the wavelength of light changes inappropriately sometimes limits transmission capacity. For this reason, the direct modulation method as described above is used in an optical communication system having a relatively low transmission rate.

  On the other hand, as a method for performing high-speed optical communication, a semiconductor laser emits light continuously, and an external modulator turns this light on / off in accordance with a drive signal (electric signal), so An external modulation method for suppressing ping is used. A Mach-Zehnder (hereinafter referred to as “MZ”) type optical modulator is known as the most common optical modulator that performs this external modulation method. Further, in the MZ type optical modulator of the NRZ (Non Return to Zero) modulation method, the high level and low level of the drive signal are combined with the light emission point and the extinction point of the light output characteristic, respectively. In the following description, the difference in bias (bias voltage) corresponding to the light emission point / quenching point of the light output characteristic that changes periodically is denoted as Vπ. In this case, the amplitude of the drive signal in the above-described NRZ modulation method is Vπ.

  Now, according to the optical modulator as described above, chirping can be suppressed as described above, but the optical output characteristic with respect to the drive signal drifts due to temperature, change with time, and the like. As a result, there is a problem that intersymbol interference may occur in the on / off level of the optical output. Therefore, for example, as disclosed in Patent Document 1, a technique for appropriately controlling the bias by the drive signal in accordance with the fluctuation of the curve, that is, a technique for normally compensating the operating point of the optical modulator has been proposed. .

  For optical modulators such as MZ type optical modulators, modulation schemes applicable to DPSK (Differential Phase Shift Keying), CSRZ (Carrier-Suppressed Return to Zero), and the like have also been proposed. As an example of such a modulation method, in Patent Document 2, the case where the amplitude of the drive signal (drive amplitude) is 2 Vπ is changed to 100%, and the percentage value is changed to 80% (drive amplitude is 1.6 Vπ). It is possible. A technique for detecting bias deviation by superimposing a low-frequency signal on a bias, that is, detecting a fluctuation amount and a fluctuation direction of an operating point, and feeding back that is disclosed to appropriately control the bias.

JP-A-3-251815 JP 2003-283432 A

  However, in the method disclosed in Patent Document 2, it is possible to stabilize the modulation of the optical modulator by bias control. However, the drive amplitude in which the deviation of the bias cannot be detected among the changed drive amplitudes. Exists. That is, there is a problem that there is a drive amplitude for which appropriate bias control cannot be performed.

  In particular, in the conventional digital transmission or the like, since the drive amplitude in the vicinity of 2Vπ (100%) where the transmission speed is most excellent is generally used, the above-described problem has not been revealed. However, an electrical dispersion compensation technique, which is a kind of analog optical modulation, called a pre-equalization technique has been reported today. In the pre-equalization, the drive signal is 2Vπ due to the requirement of modulation linearity. (100%) has been reported to be driven with a somewhat small amplitude. Therefore, it is considered that the above problems will become apparent in the future.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of performing appropriate bias control at an amplitude of an arbitrary drive signal.

  The drive control device for an optical modulator according to the present invention is an optical modulator that generates an optical signal by modulating light continuously emitted from a light source based on a drive signal, and is based on the voltage of the drive signal. This is a drive control device for an optical modulator that performs drive control on an optical modulator whose optical output characteristics change periodically. The drive control device includes a peak detection unit that acquires a peak detection output signal indicating a peak of a waveform of an electric signal according to the optical signal from the optical modulator, an oscillation circuit unit that generates an oscillation signal, and the peak A synchronous detection unit that performs synchronous detection based on the peak detection output signal acquired by the detection unit and the oscillation signal generated by the oscillation circuit unit; The drive control device includes: a bias control unit that generates a control signal for controlling a bias related to the modulation of the optical modulator based on a result of the synchronous detection by the synchronous detection unit; and the bias control unit An adder that adds the oscillation signal generated by the oscillation circuit unit to the generated control signal and a data signal based on a predetermined signal including the oscillation signal generated by the oscillation circuit unit, And an amplifier for generating the drive signal.

  According to the present invention, appropriate bias control can be performed at an amplitude of an arbitrary drive signal.

1 is a block diagram illustrating a configuration of a drive control device for an optical modulator according to a first embodiment. FIG. 5 is a diagram illustrating an operation of the drive control device for the optical modulator according to the first embodiment. FIG. 5 is a diagram illustrating an operation of the drive control device for the optical modulator according to the first embodiment. FIG. 5 is a diagram illustrating an operation of the drive control device for the optical modulator according to the first embodiment. FIG. 5 is a diagram illustrating an operation of the drive control device for the optical modulator according to the first embodiment. FIG. 5 is a diagram illustrating an operation of the drive control device for the optical modulator according to the first embodiment. FIG. 5 is a diagram illustrating an operation of the drive control device for the optical modulator according to the first embodiment. 6 is a block diagram illustrating a configuration of a drive control apparatus for an optical modulator according to a second embodiment. FIG. 6 is a block diagram illustrating a configuration of a drive control device for an optical modulator according to Embodiment 3. FIG. 6 is a block diagram illustrating a configuration of a drive control device for an optical modulator according to Embodiment 3. FIG. It is a figure which shows operation | movement of a related drive control apparatus. It is a figure which shows operation | movement of a related drive control apparatus. It is a figure which shows operation | movement of a related drive control apparatus.

<Embodiment 1>
First, before describing the drive control device for an optical modulator according to the first embodiment of the present invention, a drive control device (hereinafter referred to as “related drive control device” related to the drive control device and capable of realizing a high transmission rate). Will be described below. In the following description, it is assumed that the optical modulator is an MZ type optical modulator, but the present invention is not limited to this.

  The optical modulator according to the related drive control device generates an optical signal by modulating light continuously emitted from a light source such as a semiconductor laser based on a drive signal (electric signal), and outputs the optical signal. To do.

  FIG. 11 is a diagram illustrating the characteristics (optical output characteristics) of the optical signal with respect to the voltage of the drive signal in the optical modulator. In this optical modulator, as shown by a curve a shown in FIG. 11, the optical output characteristics change periodically with respect to the direction in which the voltage of the drive signal (drive voltage) increases or decreases (the horizontal direction in FIG. 11). ing. The light output characteristic with respect to the driving voltage here has a sine wave (cosine wave) waveform. Based on such a light output characteristic, the light output is maximum at the light emission point A and the light output at the extinction point B. Becomes the minimum (in this case, off).

  Next, an MZ type optical modulator to which the NRZ modulation method (NRZ modulation code) is applied will be described. In the NRZ modulation method, the high level and the low level of the drive signal whose level can be changed in the period T are adjusted to the light emitting point A and the extinction point B, respectively. That is, by setting the light output characteristic (extinction curve) as shown by the curve a shown in FIG. 11, on / off modulation of the light output according to the drive signal is performed. In the following description, the difference in bias (bias voltage) corresponding to the light emission point / quenching point of the light output characteristic that changes periodically is denoted as Vπ. In this case, the amplitude of the drive signal in the above-described NRZ modulation method is Vπ.

  The above optical modulator has an advantage that chirping can be suppressed. However, the light output characteristic with respect to the drive signal drifts according to a temperature change or a change with time. For example, the curve “a” shown in FIG. As a result, there is a problem that intersymbol interference occurs in the on / off level of the optical output.

  Therefore, a technique has been proposed in which the bias is appropriately controlled (that is, the operating point of the optical modulator is normally compensated) in accordance with the fluctuation of the curve indicating the optical output characteristic with respect to the drive voltage. Specifically, a drive signal on which a low-frequency oscillation signal (hereinafter referred to as “dither signal”) is superimposed is input to the optical modulator, and bias deviation from the output of the optical modulator (the amount of change and fluctuation of the operating point). Direction) and feedback it to control the bias to an appropriate value. According to this control, it is possible to suppress the influence of the drift of the light output characteristics. Note that the optimum bias point in such control is approximately the midpoint between the voltage at which the light output is turned on and the voltage at which the light output is turned off.

  Now, the related drive control device can deal with DPSK, CSRZ, and the like against the background described above. Specifically, the related drive control device can change the percentage value to, for example, 80% (drive amplitude is 1.6Vπ), assuming that the drive amplitude is 2Vπ as 100%. Then, a drive signal in which a low-frequency signal is superimposed on the bias is input to the optical modulator, a bias shift is detected from the output of the optical modulator, and the bias is controlled by feedback of the detected deviation.

  When the amplitude of the drive signal is approximately equal to 100% of 2Vπ, maximization control is performed to control the bias so that the average value of the optical output power is maximized, and the amplitude is somewhat smaller than 100% of 2Vπ. If it is a value (for example, 40% of 2Vπ), minimization control is performed to control the bias so that the average value of the optical output power is minimized. In such a related drive control device, ideally, the optimum bias point is the optimum bias point at the voltage at which the light output is turned off (hereinafter referred to as “NULL point”). Control is performed so that it becomes a point.

  According to the related drive control apparatus as described above, it is possible to detect bias deviation and feed back it to control the bias appropriately even in a modulation system in which the NULL point such as DPSK or CSRZ is the optimum bias. It is. As a result, it is possible to suppress the influence of the drift of the light output characteristics.

  However, according to the related drive control device, there is a problem that there is a drive amplitude for which appropriate bias control cannot be performed. Here, FIG. 12 shows the operation of the related drive control apparatus when the drive amplitude is 50% of 2Vπ. As shown in FIG. 12, according to the control of the related drive control device, the dither signal component does not appear in the optical signal. This phenomenon occurs similarly even if the bias is an optimum value or deviated from the optimum value. Next, this will be described with reference to FIG.

  FIG. 13 is a diagram illustrating a relationship between a synchronous detection output obtained by synchronous detection of an optical signal and a dither signal and a bias deviation in the related drive control device. When the drive amplitude is 100% of 2Vπ, the synchronous detection output is zero when the bias deviation is zero (that is, the optimum bias), and the synchronous detection output is small when the drive amplitude is small. Therefore, when the drive amplitude is 100% of 2Vπ, it is possible to detect a bias shift based on the synchronous detection output.

  However, when the drive amplitude is 50% of 2Vπ, the synchronous detection output is always zero for any bias deviation. Therefore, it is impossible to detect a bias deviation for feedback. That is, the related drive control apparatus has a problem that there is a region (50% of 2Vπ) in which appropriate bias control cannot be performed among the percentage values of the drive amplitude.

  On the other hand, according to the drive control device for an optical modulator according to the present embodiment, it is possible to perform appropriate bias control even when the drive amplitude is 50% of 2Vπ. That is, according to the drive control apparatus according to the present embodiment, it is possible to perform appropriate bias control at an arbitrary drive amplitude. Hereinafter, the drive control apparatus according to the present embodiment will be described.

  FIG. 1 is a block diagram showing a configuration of drive control apparatus 100 according to the present embodiment. In addition, in Embodiment 2-4, the referential mark attached | subjected to the component demonstrated by this Embodiment shall be attached | subjected also to the component same or similar to the said component.

  In FIG. 1, the components (light source 1 and optical modulator 2) around the drive control device 100 are also illustrated. The light source 1 is composed of a semiconductor laser, for example, and emits light continuously. The optical modulator 2 is composed of, for example, an MZ type optical modulator or the like, and generates an optical signal by modulating continuous light from the light source 1 based on a drive signal while adding a bias (bias voltage). Note that the optical output characteristic with respect to the drive voltage related to the optical modulator 2 changes periodically similarly to the optical output characteristic of the related drive control device shown in FIG.

  As shown in FIG. 1, the drive control apparatus 100 according to the present embodiment includes a duplexer 3, a photodiode 4, a peak detection unit 5, an oscillation circuit unit 6, a synchronous detection unit 7, and a bias setting. A unit 8, an amplitude setting unit 9, adders 10 a and 10 b, and an amplifier 11 are provided. The drive control apparatus 100 converts an external data signal into a drive signal and outputs the drive signal to the optical modulator 2 and outputs the above-described bias relating to the modulation of the optical modulator 2. Thus, the drive control apparatus 100 performs drive control on the optical modulator 2. Next, components of the drive control device 100 will be described in detail.

  The demultiplexer 3 demultiplexes the optical signal (output signal) from the optical modulator 2, and the photodiode 4 converts the optical signal obtained by demultiplexing by the demultiplexer 3 into an electrical signal.

  The peak detection unit 5 acquires a peak detection output signal indicating the peak of the waveform of the electrical signal obtained by the photodiode 4 (an electrical signal corresponding to the optical signal from the optical modulator 2). Here, the peak detection unit 5 acquires a peak detection output signal indicating an envelope formed by connecting local peaks of the waveform of the electrical signal obtained by the photodiode 4. For example, a peak detector that can be easily configured using a diode and a capacitor, a peak detector that is easily available in the market, and the like are usually used for such a peak detector 5.

  The oscillation circuit unit 6 generates a low-frequency oscillation signal (dither signal). It is assumed that the dither signal generated by the oscillation circuit unit 6 has a lower frequency than the control signal and the drive signal.

  The synchronous detection unit 7 performs synchronous detection based on the peak detection output signal acquired by the peak detection unit 5 and the dither signal generated by the oscillation circuit unit 6. That is, the synchronous detection unit 7 extracts the difference between the peak detection output signals from the dither signal that is the reference signal. For example, a detector including a band pass filter, a mixer, and a low-pass filter is used for the synchronous detection unit 7. Further, the processing in the synchronous detection unit 7 may be realized by digital signal processing.

  The bias setting unit 8, which is a bias control unit, generates a control signal for controlling the bias related to the modulation of the optical modulator 2 based on the result of the synchronous detection by the synchronous detection unit 7. That is, the bias setting unit 8 sets a bias related to the modulation of the optical modulator 2.

  The amplitude setting unit 9 generates an amplitude setting signal indicating the amplitude that the drive signal input to the optical modulator 2 should have. Here, as an example of the amplitude setting in the amplitude setting unit 9, the amplitude that the drive signal should have is set as a percentage value of 2Vπ, such as 100%, 80%,. However, the present invention is not limited to this, and the amplitude itself may be set such as 2Vπ, 1.6Vπ,.

  The adder 10a adds a dither signal generated by the oscillation circuit unit 6 and an amplitude setting signal generated by the amplitude setting unit 9, thereby setting a gain signal (predetermined signal) for setting the gain of the amplifier 11. Is generated. Therefore, the gain signal includes a dither signal from the oscillation circuit unit 6 and an amplitude setting signal from the amplitude setting unit 9.

  The adder 10b adds the dither signal generated by the oscillation circuit unit 6 to the control signal generated by the bias setting unit 8 to thereby add a bias (control signal after addition) to be used in the modulation of the optical modulator 2. ) To the optical modulator 2.

  The above gain signal including the dither signal generated by the oscillation circuit unit 6 and the amplitude setting signal generated by the amplitude setting unit 9 is input to the gain adjustment terminal of the amplifier 11. Then, the amplifier 11 generates a drive signal by amplifying the data signal based on the gain signal. That is, the drive signal generated by the amplifier 11 is a signal amplified (intensity modulated) by the gain signal that has moved the oscillation center of the dither signal by the amplitude setting signal. The drive signal generated in this way is input to the optical modulator 2 via the capacitor 12.

  Next, the operation of the drive control apparatus 100 according to the present embodiment will be described. The continuous light emitted from the light source 1 is input to the optical modulator 2. The adder 10 a adds the dither signal from the oscillation circuit unit 6 to the amplitude setting signal from the amplitude setting unit 9 and outputs the gain signal obtained thereby to the amplifier 11. The amplifier 11 generates a drive signal by amplifying the data signal based on the gain signal from the adder 10a. The optical modulator 2 outputs an optical signal obtained by modulating continuous light from the light source 1 based on a drive signal in consideration of a bias. The optical signal output from the optical modulator 2 is demultiplexed by the demultiplexer 3, converted into an electric signal by the photodiode 4, and input to the peak detector 5. The peak detector 5 generates a peak detection output signal indicating the envelope of the electrical signal. Here, since the peak detector 5 acquires the envelope of the electric signal, only the component related to the dither signal is extracted.

  The synchronous detection unit 7 performs synchronous detection by multiplying the peak detection output signal from the peak detection unit 5 and the dither signal generated by the oscillation circuit unit 6, and thereby the difference between the peak detection output signal from the dither signal. And outputs the signal to the bias setting unit 8. The bias setting unit 8 outputs a control signal for controlling the bias based on the signal from the synchronous detection unit 7. The adder 10 b adds the dither signal to the control signal and outputs the bias obtained thereby to the optical modulator 2.

  According to the drive control apparatus 100 according to the present embodiment that performs the above control, it is possible to appropriately control the bias with respect to an arbitrary amplitude of the drive signal, that is, an arbitrary amplification in the amplifier 11. As a result, it is possible to suppress the influence of drift of the light output characteristics. Hereinafter, this will be described with reference to FIGS.

  FIG. 2 is a diagram showing signals generated in drive control apparatus 100 according to the present embodiment. FIG. 2 includes FIGS. 2 (a) to 2 (c).

  FIG. 2A is a diagram illustrating a bias input to the optical modulator 2 from the adder 10b, that is, a control signal after addition). As shown in FIG. 2A, two dither signals having the same phase appear at both ends in the amplitude direction of the bias waveform.

  FIG. 2B is a diagram illustrating a drive signal input from the amplifier 11 to the optical modulator 2, that is, a signal that has been amplitude-modulated based on a gain signal including a dither signal. As shown in FIG. 2B, two dither signals whose phases are shifted from each other by 180 ° appear at both ends in the amplitude direction of the waveform of the drive signal.

  In the present embodiment, the bias shown in FIG. 2A and the drive signal shown in FIG. 2B are input to the optical modulator 2. Then, as shown in FIG. 2C, the optical modulator 2 adds a dither signal on one light emitting point side and cancels the dither signal on the other light emitting point side (hereinafter referred to as “composite signal”). The optical signal (output signal) is generated based on “ As a result, the dither signal superimposed on the composite signal is asymmetrical on one light emitting point side and the other light emitting point side.

  Next, the operations of the optical modulator 2 and the drive control device 100 when the optical modulator 2 generates an optical signal (output signal) based on the combined signal as shown in FIG. This will be described with reference to FIG.

  FIG. 3 is a diagram illustrating operations of the optical modulator 2 and the drive control device 100 when the bias is appropriately set. In this case, as indicated by the alternate long and short dash line in FIG. 3, the light emission point corresponds to the center of the amplitude of the dither signal superimposed on the synthesized signal. As a result, the peak detection output signal from the peak detection unit 5 includes only a frequency component that is twice the frequency of the dither signal. For this reason, the output of the synchronous detection unit 7 indicating the result of synchronous detection between the peak detection output signal from the peak detection unit 5 and the dither signal from the oscillation circuit unit 6 is zero. When the bias setting unit 8 receives zero from the synchronous detection unit 7, the bias setting unit 8 determines that the bias is appropriately controlled and set.

  On the other hand, FIG. 4 is a diagram illustrating operations of the optical modulator 2 and the drive control device 100 when the bias is set higher than an appropriate value. In this case, as indicated by the alternate long and short dash line in FIG. 4, the emission point corresponds to a value lower than the center of the amplitude of the dither signal superimposed on the synthesized signal. As a result, the peak detection output signal includes the same frequency component as the dither signal, and the phase is shifted from the dither signal by 180 °. For this reason, the output of the synchronous detector 7 is a negative value. When the bias setting unit 8 receives a negative value from the synchronous detection unit 7, the bias setting unit 8 outputs a control signal for decreasing the bias according to the value.

  FIG. 5 is a diagram illustrating operations of the optical modulator 2 and the drive control device 100 when the bias is set lower than an appropriate value. In this case, as indicated by the alternate long and short dash line in FIG. 5, the emission point corresponds to a value higher than the center of the amplitude of the dither signal superimposed on the synthesized signal. As a result, the peak detection output signal includes the same frequency component as the dither signal, and the phase is the same as the dither signal. For this reason, the output of the synchronous detection unit 7 is a positive value. When the bias setting unit 8 receives a positive value from the synchronous detection unit 7, the bias setting unit 8 outputs a control signal for increasing the bias according to the value.

  As described above, if the control described with reference to FIGS. 3 to 5 is performed, the bias can be controlled to an appropriate value, and the influence of the drift of the light output characteristics can be suppressed.

  However, the above is a description of the case where the dynamic amplitude of the drive signal input to the optical modulator 2 is 100% of 2Vπ. Next, operations of the optical modulator 2 and the drive control device 100 when the amplitude of the drive signal is 50% of 2Vπ will be described with reference to FIG. Here, FIG. 6 shows operations of the optical modulator 2 and the drive control device 100 when the amplitude of the drive signal is 50% of 2Vπ and the bias is appropriately set. In this case, the center point of the light emission point and the extinction point corresponds to the center of the amplitude of the dither signal superimposed on the combined signal, as indicated by the alternate long and short dash line in FIG. As a result, the output signal of the peak detector 5 includes the same frequency component as the dither signal, and the phase is the same as the dither signal. For this reason, the output of the synchronous detection unit 7 is a positive value.

  Next, FIG. 7 shows the relationship between the synchronous detection output and the bias deviation in the drive control apparatus 100 according to the present embodiment. As shown in FIG. 7, in the drive control apparatus 100 according to the present embodiment, the bias shift corresponding to the peak of the synchronous detection output varies depending on the drive amplitude. The peak value is the same regardless of the drive amplitude.

  Now, as shown in FIG. 7, according to the drive control apparatus 100 according to the present embodiment, even if the drive amplitude is 0, 25, 50, 75, or 100% of 2Vπ, the bias shifts. The synchronous detection output changes accordingly. For example, when the drive amplitude is 50% of 2Vπ, the synchronous detection output increases in the positive direction as the bias deviation approaches zero, as shown by a curve with a triangle in FIG. Therefore, according to the drive control apparatus 100 according to the present embodiment, even when the drive amplitude is 50% of 2Vπ, which cannot be performed by the related drive control apparatus, an appropriate bias according to the synchronous detection output is obtained. Control can be performed. That is, appropriate bias control can be performed at an arbitrary drive signal amplitude. Further, in the bias control of the optical modulator 2, the bias can be controlled to the NULL point, and the optical modulator 2 can be stably operated.

  The amplitude of the dither signal included in the bias (output signal) from the adder 10b shown in FIG. 2A and the amplitude of the dither signal included in the gain signal shown in FIG. It is desirable to be equal. In this case, it is possible to completely cancel at one light emission point of the combined signal shown in FIG. 2C, and to suppress signal quality deterioration due to addition of the dither signal. In addition, the synchronous detection output can be made relatively large, and the control sensitivity can be increased. However, it is not always necessary to make the two amplitudes equal to each other. For example, when the control sensitivity is sufficiently obtained, this is not necessary.

  In the related drive control device, the synchronous detection output corresponding to the optimum bias is zero regardless of the drive amplitude, but the synchronous detection output corresponding to the optimum bias in the drive control device 100 according to the present embodiment is As shown in FIG. 7, it varies depending on the drive amplitude. Therefore, it is desirable to automatically control the bias using the relationship according to the drive amplitude from the relationship between the synchronous detection output and the bias deviation shown in FIG. This will be described in the second to fourth embodiments.

<Embodiment 2>
FIG. 8 is a block diagram showing a configuration of drive control apparatus 100 according to Embodiment 2 of the present invention. In general, drive control apparatus 100 according to the present embodiment is configured such that amplitude setting section 9 is directly connected to bias setting section 8 in drive control apparatus 100 according to the first embodiment.

  In the drive control apparatus 100 according to the first embodiment described above, the bias setting unit 8 is configured so that the bias deviation set in advance for the synchronous detection output becomes zero based on the relationship shown in FIG. Control with feedback. However, as described above, since the relationship between the synchronous detection output and the bias deviation changes according to the drive amplitude, it is considered that information related to the drive amplitude should be input to the bias setting unit 8.

  Therefore, in the present embodiment, in the drive control device 100, the amplitude setting signal generated by the amplitude setting unit 9, that is, a signal indicating 100% of 2Vπ, 0% of 2Vπ, or the like is input to the bias setting unit 8. . The bias setting unit 8 calculates the amplitude of the drive signal input to the optical modulator 2 based on the amplitude setting signal generated by the amplitude setting unit 9.

  The bias setting unit 8 has a storage unit 8a that stores the relationship between the synchronous detection output and the bias deviation shown in FIG. 7, and corresponds to the calculated amplitude from the relationship stored in the storage unit 8a. Get relationship. Then, the bias setting unit 8 generates a control signal based on the acquired relationship so that the bias deviation set for the synchronous detection output becomes zero. That is, in the present embodiment, the bias setting unit 8 generates a control signal for controlling the bias in consideration of the amplitude setting signal generated by the amplitude setting unit 9.

  According to the drive control apparatus 100 according to the present embodiment as described above, each time the amplitude is changed by the amplitude setting unit 9, the relationship between the synchronous detection output and the bias deviation is appropriately selected and the relationship is used. And appropriate bias control can be performed. Therefore, the user-friendly drive control device 100 can be realized.

<Embodiment 3>
FIG. 9 is a block diagram showing a configuration of drive control apparatus 100 according to Embodiment 2 of the present invention. The drive control apparatus 100 according to the present embodiment is substantially the same as the drive control apparatus 100 according to the first embodiment, except that a light intensity detection unit 13 connected to the photodiode 4 and the bias setting unit 8 is added. ing.

  In the second embodiment described above, the control signal is generated in consideration of the amplitude indicated by the amplitude setting signal generated by the amplitude setting unit 9. Here, the amplitude indicated by the amplitude setting signal is considered to have a correspondence relationship with the light intensity of the optical signal from the optical modulator 2.

  Therefore, in the present embodiment, the light intensity detector 13 detects the light intensity of the optical signal from the optical modulator 2 (here, the light intensity of the optical signal input to the photodiode 4). Then, the bias setting unit 8 calculates the amplitude of the drive signal input to the optical modulator 2 based on the light intensity detected by the light intensity detection unit 13.

  The bias setting unit 8 has a storage unit 8a that stores the relationship between the synchronous detection output and the bias deviation shown in FIG. 7, and corresponds to the calculated amplitude from the relationship stored in the storage unit 8a. Get relationship. Then, the bias setting unit 8 generates a control signal based on the acquired relationship so that the bias deviation set for the synchronous detection output becomes zero. That is, in the present embodiment, the bias setting unit 8 generates a control signal in consideration of the light intensity detected by the light intensity detection unit 13.

  According to the drive control apparatus 100 according to the present embodiment as described above, each time the amplitude is changed by the amplitude setting unit 9, the relationship between the synchronous detection output and the bias deviation is appropriately selected and the relationship is used. And appropriate bias control can be performed. Therefore, the user-friendly drive control device 100 can be realized.

<Embodiment 4>
FIG. 10 is a block diagram showing a configuration of drive control apparatus 100 according to Embodiment 2 of the present invention. The drive control apparatus 100 according to the present embodiment is generally the same as the drive control apparatus 100 according to the first embodiment except that a high-frequency peak detection unit 14 (amplitude detection unit) connected to the capacitor 12 and the optical modulator 2 is added. It has become.

  In the second embodiment described above, the control signal is generated in consideration of the amplitude indicated by the amplitude setting signal generated by the amplitude setting unit 9. On the other hand, in the present embodiment, the high-frequency peak detector 14 directly detects the amplitude of the drive signal input to the optical modulator 2.

  The bias setting unit 8 has a storage unit 8a that stores the relationship between the synchronous detection output and the bias deviation shown in FIG. 7, and corresponds to the calculated amplitude from the relationship stored in the storage unit 8a. Get relationship. Then, the bias setting unit 8 generates a control signal based on the acquired relationship so that the bias deviation set for the synchronous detection output becomes zero. That is, in the present embodiment, the bias setting unit 8 generates a control signal in consideration of the amplitude detected by the high frequency peak detection unit 14.

  According to the drive control apparatus 100 according to the present embodiment as described above, each time the amplitude is changed by the amplitude setting unit 9, the relationship between the synchronous detection output and the bias deviation is appropriately selected and the relationship is used. And appropriate bias control can be performed. Therefore, the user-friendly drive control device 100 can be realized.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and the form of each embodiment can be modified or omitted as appropriate.

  DESCRIPTION OF SYMBOLS 1 Light source, 2 Optical modulator, 5 Peak detection part, 6 Oscillation circuit part, 7 Synchronous detection part, 8 Bias setting part, 9 Amplitude setting part, 10b Adder, 11 Amplifier, 13 Light intensity detection part, 14 High frequency peak detection Part, 100 drive control device.

Claims (5)

An optical modulator that generates an optical signal by modulating light continuously emitted from a light source based on a driving signal, wherein the optical output characteristic with respect to the voltage of the driving signal changes periodically. On the other hand, a drive control device for an optical modulator that performs drive control,
A peak detector for acquiring a peak detection output signal indicating a peak of a waveform of an electric signal according to the optical signal from the optical modulator;
An oscillation circuit unit for generating an oscillation signal;
A synchronous detection unit that performs synchronous detection based on the peak detection output signal acquired by the peak detection unit and the oscillation signal generated by the oscillation circuit unit;
A bias control unit that generates a control signal for controlling a bias related to the modulation of the optical modulator based on a result of synchronous detection in the synchronous detection unit;
An adder for adding the oscillation signal generated by the oscillation circuit unit to the control signal generated by the bias control unit;
An optical modulator drive control device comprising: an amplifier that generates the drive signal by amplifying a data signal based on a predetermined signal including an oscillation signal generated by the oscillation circuit unit. The drive control device for an optical modulator according to claim 1,
An optical modulator drive control device, wherein an amplitude of the oscillation signal included in the output signal from the adder is equal to an amplitude of the oscillation signal included in the predetermined signal. A drive control apparatus for an optical modulator according to claim 1 or 2,
An amplitude setting unit that generates an amplitude setting signal included in the predetermined signal, indicating an amplitude that the drive signal should have;
The bias control unit is a drive control device for an optical modulator, which generates the control signal in consideration of the amplitude setting signal generated by the amplitude setting unit. A drive control apparatus for an optical modulator according to claim 1 or 2,
A light intensity detector that detects the light intensity of the optical signal from the optical modulator;
The bias control unit is a drive control device for an optical modulator, which generates the control signal in consideration of the light intensity detected by the light intensity detection unit. A drive control apparatus for an optical modulator according to claim 1 or 2,
An amplitude detector for detecting the amplitude of the drive signal;
The drive control device for an optical modulator, wherein the bias control unit generates the control signal in consideration of an amplitude of the drive signal detected by the amplitude detection unit.

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