An automatic bias control device suitable for different working modes of a modulator

Abstract

The application discloses an automatic bias control device suitable for different working modes of a modulator and relates to the technical field of optical modulation, comprising a laser, a modulator, a spectrometer, a PD, a signal acquisition module and an MCU which are sequentially connected, wherein a bias circuit module is arranged between the MCU and the modulator, a TEC module is arranged between the MCU and the laser and the modulator, and a host computer is connected to the MCU; wherein the TEC module is used for temperature compensation of the laser and maintaining constant temperature of the working environment of the modulator; the host computer is used for setting the working mode of the modulator and starting the automatic bias control device. The application can minimize the drift of the working point of the modulator caused by the change of the external environment temperature.

Description

Technical Field

[0001] This invention relates to the field of optical modulation technology, and more specifically to an automatic bias control device applicable to different operating modes of modulators. Background Technology

[0002] In optical communication, electro-optic modulators, which perform electro-optic conversion, are particularly important, especially Mach-Zehnder modulators (MZMs), which are widely used in digital communication due to their large modulation bandwidth and low chirp. However, the operating point of an MZM modulator is susceptible to factors such as temperature, applied electric field, natural aging, manufacturing imperfections, and operating time, causing drift in the modulator's operating point and leading to distortion of the modulated output optical signal and an increase in the bit error rate of the communication system. Therefore, the operating point of the electro-optic modulator needs to be maintained at the desired position on the transmission response curve to achieve stable modulation of the optical signal. Commonly used operating points include Quad+, Quad-, Null, and Peak points. The transmission response curve of an electro-optic modulator is shown in the figure below. Figure 1 As shown.

[0003] In practical applications, modulators typically operate in MAX, QUAD, and MIN modes. The drift of the bias operating point is primarily manifested as a horizontal shift in the transmission characteristic curve. After the modulator has been operating for a period of time, due to changes in temperature, humidity, pressure, etc., the transmission characteristic curve may shift to the left or right.

[0004] Existing control methods for automatic bias locking of modulator operating points mainly fall into two categories: optical power detection and frequency scrambling. The optical power detection method is based on the analysis of the modulator's output optical power to determine whether the bias point has shifted. The frequency scrambling method detects the bias point by adding periodic perturbation signals and monitoring and analyzing relevant harmonic power components.

[0005] The two detection methods mentioned above each have their advantages and disadvantages. For the optical power detection method, the circuit is relatively simple, but the measured value of its output optical power is heavily dependent on the optical power input to the modulator. Once the input optical power value changes, it is impossible to determine whether the operating point has drifted. For the frequency scrambling method, a low-frequency sine wave circuit needs to be added to the circuit, and the output detection part needs to add first harmonic, second harmonic, and peak detection circuits, which makes the circuit configuration more complex. Moreover, the amplitude of the second harmonic detection is small, and the measurement sensitivity is limited. Summary of the Invention

[0006] In view of the deficiencies in the existing technology, the purpose of this invention is to provide an automatic bias control device applicable to different operating modes of the modulator, which can minimize the drift of the modulator operating point caused by changes in the external ambient temperature.

[0007] To achieve the above objectives, the technical solution adopted by the present invention includes a laser, a modulator, a spectrometer, a PD, a signal acquisition module and an MCU connected in sequence. A bias circuit module is provided between the MCU and the modulator. A TEC module is provided between the MCU and the laser and the modulator. A host computer is connected to the MCU.

[0008] The TEC module is used for temperature compensation of the laser and to maintain a constant temperature in the working environment of the modulator. The host computer is used to set the working mode of the modulator and to start the automatic bias control device.

[0009] Based on the above technical solutions,

[0010] The TEC module includes a first TEC circuit module and a second TEC circuit module;

[0011] Both the first TEC circuit module and the second TEC circuit module include TEC components and TEC drive circuits;

[0012] The TEC drive circuit is used to drive TEC components for temperature control.

[0013] The first TEC circuit module is used for temperature compensation during laser operation;

[0014] The second TEC circuit module is used to maintain a constant operating temperature for the modulator during operation.

[0015] Based on the above technical solution, the TEC drive circuit is a hardware circuit based on DRV593.

[0016] Based on the above technical solution, the bias circuit module includes an adder circuit and a DAC output circuit and a sine wave generator circuit connected to the input terminal of the adder circuit.

[0017] Based on the above technical solutions,

[0018] The voltage range output by the DAC output circuit can scan and cover at least one full-wave voltage range of the modulator.

[0019] The voltage output by the DAC output circuit and the signal output by the sine wave generator circuit are combined with an AC signal with the required DC component generated by the adder circuit to apply the voltage required for the operating point to the DC bias terminal of the modulator.

[0020] Based on the above technical solution, the signal acquisition module includes an optical power detection circuit, a first harmonic filter circuit, and a peak-to-peak value detection circuit connected in sequence.

[0021] Based on the above technical solutions,

[0022] The optical power detection circuit is an IV amplifier circuit, used to detect the optical power value output by the modulator after passing through the spectrometer;

[0023] The first harmonic filter circuit is a low-frequency filter circuit, used to filter high-frequency signals in the signal output by the modulator after passing through the spectrometer.

[0024] The peak-to-peak detection circuit is used to detect the amplitude of the first harmonic signal in the signal output by the modulator after passing through the spectrometer.

[0025] Based on the above technical solution, the MCU is used to control the operation of the signal acquisition module and the TEC module, as well as to scan and lock the operating point of the modulator, and at the same time upload the data detected by the signal acquisition module to the host computer.

[0026] Based on the above technical solution, the wavelength of the light output by the laser is matched with the wavelength of the input light of the modulator.

[0027] Based on the above technical solution, the modulator is a lithium niobate modulator made of thin film or thick film material.

[0028] Compared with the prior art, the advantages of the present invention are as follows:

[0029] (1) By adding a TEC module, the modulator’s operating environment can be stabilized at a constant temperature to the maximum extent, thereby minimizing the drift of the modulator’s operating point caused by changes in the ambient temperature.

[0030] (2) By combining optical power detection and frequency scrambling, the advantages of each method are combined. This not only makes up for the dependence of optical power detection on input optical power, but also makes up for the need for frequency scrambling to detect the first and second harmonics to lock the operating point. At the same time, without increasing hardware complexity, this invention can lock the modulator's various operating modes through the combination of software algorithms, which is of positive significance. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of the operating points of the electro-optic modulator's response transmission curve.

[0033] Figure 2This is a schematic diagram of the automatic bias control device applicable to different operating modes of the modulator in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the bias circuit module in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the signal acquisition module in an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the automatic bias control device when the modulator is operating at the MAX point. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. It should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances. In this application, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0038] This invention provides an automatic bias control device applicable to different operating modes of a modulator. This device, through circuit design, suppresses modulator operating point drift during actual use. Furthermore, it establishes a unified and simple operating point locking method for different modulator operating modes. See also... Figure 2 As shown, the automatic bias control device of the present invention, applicable to different operating modes of the modulator, includes a laser, a modulator, a spectrometer, a PD (photodiode), a signal acquisition module, and an MCU (Microcontroller Unit) connected in sequence. A bias circuit module is provided between the MCU and the modulator, that is, one end of the bias circuit module is connected to the MCU and the other end is connected to the modulator. A TEC (Thermo Electric Cooler) module is provided between the MCU and the laser and the modulator, that is, one end of the TEC module is connected to the MCU and the other end is connected to the laser and the modulator. A host computer is connected to the MCU.

[0039] In this invention, the TEC module is used for temperature compensation during laser operation and to maintain a constant operating temperature for the modulator. Specifically, the TEC module includes a first TEC circuit module and a second TEC circuit module; both the first and second TEC circuit modules include TEC components and a TEC drive circuit. The TEC drive circuit is a hardware circuit based on DRV593 (an amplifier). In actual use, both the first and second TEC circuit modules include at least one TEC component and a TEC drive circuit. The TEC drive circuit is used to drive the TEC components for temperature control. The first TEC circuit module is used for temperature compensation during laser operation. The second TEC circuit module is used to maintain a constant operating temperature for the modulator, thereby minimizing the impact of changes in the external working environment on the modulator's operating point drift.

[0040] In this invention, the host computer is used to set the modulator's operating mode and to start the automatic bias control device of this invention.

[0041] See Figure 3 As shown, in this invention, the bias circuit module includes an adder circuit and a DAC (digital-to-analog converter) output circuit and a sine wave generator circuit connected to the input terminal of the adder circuit. The voltage range output by the DAC output circuit can scan and cover at least one full-wave voltage range of the modulator; the voltage output by the DAC output circuit and the signal output by the sine wave generator circuit, through the AC signal with the desired DC component generated by the adder circuit, are used to apply the voltage required for the operating point to the DC bias terminal of the modulator.

[0042] Specifically, the DAC output circuit is a bipolar DAC capable of outputting ±10V, thus its output range can scan and cover at least one full-wave voltage range of the modulator. This ensures accurate detection of each operating point of the modulator during system operation. The sine wave generator circuit can use a commonly used sine wave chip with an output signal frequency of 1kHz. In this invention, the bias circuit module can output different signals depending on the modulator's operating mode. For example, upon power-on, when it is necessary to locate the modulator's various operating points and half-wave voltage parameters, the MCU controls the DAC output circuit of the bias circuit module to output only the DC component, without including a sine wave signal, for quickly scanning the modulator's various operating point data.

[0043] See Figure 4 As shown, in this invention, the signal acquisition module includes an optical power detection circuit, a first harmonic filter circuit, and a peak-to-peak value detection circuit connected in sequence. The optical power detection circuit is an IV (current-voltage) amplifier circuit used to detect the optical power value output by the modulator after passing through the spectrometer; the first harmonic filter circuit is a low-frequency filter circuit used to filter high-frequency signals in the signal output by the modulator after passing through the spectrometer; the peak-to-peak value detection circuit is used to detect the amplitude of the first harmonic signal in the signal output by the modulator after passing through the spectrometer.

[0044] In this invention, the MCU is an FPGA or MCU unit used to control the operation of the signal acquisition module and the TEC module, as well as to scan and lock the operating point of the modulator, and simultaneously upload the data detected by the signal acquisition module to the host computer.

[0045] In this invention, the wavelength of the laser output is 1310nm or 1550nm. Specifically, the wavelength of the light output by the laser is matched with the wavelength of the input light of the modulator.

[0046] In this invention, the modulator is a lithium niobate modulator made of thin film or thick film material.

[0047] In one possible implementation, the present invention also provides a readable storage medium located in a PLC (Programmable Logic Controller) controller, on which a computer program is stored. When executed by a processor, the program enables the corresponding operation control of the signal acquisition module and the bias circuit module.

[0048] Storage media may be any combination of one or more computer-readable media. A computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. Computer-readable storage media may be, for example, but not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or devices, or any combination thereof. More specific examples (a non-exhaustive list) of computer-readable storage media include: electrical connections having one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof. In this document, a computer-readable storage medium may be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0049] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media may also be any computer-readable medium other than computer-readable storage media, capable of transmitting, propagating, or transmitting programs for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium may be transmitted using any suitable medium, including but not limited to: wireless, wireline, optical fiber, RF, etc., or any suitable combination thereof.

[0050] Computer program code for performing the operations of this invention can be written in one or more programming languages ​​or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, and C++, as well as conventional procedural programming languages—such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0051] In actual use, after power-on, the MCU scans the modulator's operating point data through the bias circuit module. The user selects the modulator's operating mode (MAX point, QUAD point, MIN point) through the host computer. The MCU applies the corresponding operating voltage according to the modulator's operating mode and detects and locks the operating point of the device in real time.

[0052] It should be noted that, due to different modulator operating modes, the hardware circuits and software logic used in the automatic bias control device are not entirely the same, but the automatic bias control device of this invention is compatible with different modulator operating modes. A detailed description follows.

[0053] In Example 1, when the modulator operates in MAX / MIN point mode, the circuit of the automatic bias control device can be simplified, such as... Figure 5 As shown, the bias circuit module can be simplified to a DAC output circuit, and the original sine wave generator circuit and adder circuit can be simplified and removed; the signal acquisition module can be simplified to an optical power detection circuit, and the original first harmonic filter circuit and peak-to-peak value detection circuit can be simplified and removed. The specific implementation steps are as follows:

[0054] S1: Power-on initialization, mainly including laser operation, TEC module operation, and DAC output circuit initialization of the bias circuit module;

[0055] S2: The MCU controls the bias circuit module to make the DAC output circuit gradually apply a scanning voltage to the DC bias port of the modulator in 50mV increments, with a time gradient of -10V to 10V every 50ms. During this period, the signal acquisition module detects the amplitude of the optical power signal output by the modulator through the optical power detection circuit and transmits each optical power data to the MCU.

[0056] S3: The MCU records the optical power data corresponding to each step interval voltage, and then scans to obtain the DC bias voltage and optical power data corresponding to each operating point of the modulator;

[0057] S4: Set the modulator's working mode to MAX point via the host computer interface;

[0058] S4: The MCU receives the instruction, sets the DAC output circuit to the voltage value V0 corresponding to MAX through the bias circuit module, and records the optical power data acquired at this time.

[0059] S5: Acquire the optical power data P of the modulator at 500ms intervals. Once the optical power data of the modulator is less than the optical power data acquired last time, the MCU dynamically adjusts the output voltage of the DAC output circuit. For example, when the working mode is MAX point, if the acquired optical power data P is less than the value acquired last time, it indicates that the working point of the modulator has drifted to a certain extent or the input optical power of the modulator has changed. At this time, the output voltage of the DAC output circuit is dynamically adjusted to reduce the amplitude of ΔV.

[0060] S6: Acquire optical power data. If the optical power data is smaller than the previous data, it indicates that the step voltage direction is reversed. It is necessary to adjust ΔV = -1*ΔV, continue adjusting the output voltage of the DAC output circuit, and detect the acquired optical power. This cycle repeats continuously, effectively dynamically locking the modulator's operating point to the MAX point. Because the amplitude of ΔV in this invention is small, only 5-10mV, its dynamic change by one step does not affect the modulator's modulation efficiency. Furthermore, in this invention, the control algorithm does not rely on changes in the modulator's input optical power, thus maintaining the modulator in MAX point operating mode at all times.

[0061] In addition, when the modulator is operating in the MIN point mode, its hardware is exactly the same as described above, and its control implementation steps are also similar. The only difference is that when operating in the MIN point, once the detected optical power value is greater than the previously detected optical power value, it is determined that the operating point of the device has drifted.

[0062] In Example 2, when the modulator operates in Quad-point mode (Quad+ or Quad- points are collectively referred to as Quad points), its operating point locking method is similar to the scrambling method, such as... Figure 2 As shown, the bias circuit module includes a DAC output circuit, a sine wave generator circuit, and an adder circuit, while the signal acquisition circuit module includes an optical power detection circuit, a first harmonic filter circuit, and a peak-to-peak value detection circuit.

[0063] The principle of operating point locking using the scrambling method is as follows: When operating at the Quad point, by applying a 1kHz sine wave signal with a DC component to the bias circuit, the signal light part of the modulator output will generate optical signals with 1kHz and 2kHz signals. At this time, the amplitude of the generated 1kHz optical signal is at its maximum value. By detecting the amplitude change of the 1kHz optical signal, it can be determined whether the signal is stably operating at the Quad point.

[0064] The specific implementation process is as follows:

[0065] A: Power-on initialization mainly includes laser operation, TEC module operation, and DAC output circuit initialization of the bias circuit module;

[0066] B: The MCU controls the bias circuit module to make the DAC output circuit gradually apply a scanning voltage to the DC bias port of the modulator in 50mV increments, with a time gradient of -10V to 10V every 50ms. During this period, the signal acquisition module detects the amplitude of the optical power signal output by the modulator through the optical power detection circuit and transmits each optical power data to the MCU.

[0067] C: The MCU records the optical power data corresponding to each step interval voltage, and then scans to obtain the DC bias voltage and optical power data corresponding to each operating point of the modulator;

[0068] D: Set the modulator's working mode to Quad point via the host computer interface;

[0069] E: The MCU receives the instruction and sets the output of the DAC output circuit to the DC voltage V0 corresponding to MAX through the bias circuit module. It also generates a sine wave signal with a period of 1KHz and an amplitude of 50mV through the sine wave generator circuit. The DC voltage V0 and the 1KHz sine wave signal are combined through the adder circuit to generate a signal with a DC component of V0, a ​​period of 1KHz, and an AC amplitude of 50mV, which is then applied to the DC bias terminal of the modulator.

[0070] F: The amplitude of the 1KHz signal in the optical signal output by the modulator is acquired through the first harmonic filter circuit and peak-to-peak detection circuit of the signal acquisition module at 500ms intervals. Once the amplitude of the 1KHz signal is detected to be less than the previously acquired data value, it indicates that the modulator's operating state has drifted. The MCU then dynamically adjusts the output voltage of the DAC output circuit. For example, when the operating mode is Quad point, if the amplitude of the acquired 1KHz signal output by the modulator is less than the previously acquired value, it indicates that the modulator's operating point has drifted to a certain extent or the input optical power of the modulator has changed. At this time, the output voltage of the DAC output circuit is dynamically adjusted to reduce the amplitude of ΔV.

[0071] G: Acquire the amplitude of the 1kHz signal output from the modulator. If the amplitude of the 1kHz signal is smaller than the previous data, it indicates that the step voltage direction is reversed. It is necessary to adjust ΔV = -1*ΔV, continue adjusting the output voltage of the DAC output circuit, and detect the amplitude of the acquired 1kHz signal output from the modulator. This cycle repeats continuously, effectively dynamically locking the modulator's operating point to the Quad point. Because the amplitude of ΔV is small in this invention, only 5-10mV, its dynamic change by one step does not affect the modulator's modulation efficiency. Furthermore, in this invention, the control algorithm does not rely on changes in the modulator's input optical power, thus maintaining the modulator in Quad point operating mode at all times.

[0072] The automatic bias control device applicable to different operating modes of the modulator in this embodiment of the invention stabilizes the modulator's operating environment at a constant temperature by adding a TEC module, thereby minimizing the drift of the modulator's operating point caused by changes in the external ambient temperature. By combining optical power detection and frequency scrambling, the advantages of each are combined. This not only compensates for the dependence of optical power detection on input optical power, but also compensates for the need for frequency scrambling to detect the first and second harmonics to lock the operating point. At the same time, this invention can lock the modulator's various operating modes without increasing hardware complexity through the combination of software algorithms, which is of positive significance.

[0073] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0074] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0075] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An automatic bias control device applicable to different operating modes of a modulator, characterized in that, It includes a laser, a modulator, a spectrometer, a PD, a signal acquisition module, and an MCU connected in sequence. A bias circuit module is provided between the MCU and the modulator. A TEC module is provided between the MCU and the laser and the modulator. A host computer is connected to the MCU. The TEC module is used for temperature compensation during laser operation and to maintain a constant temperature in the working environment of the modulator. The host computer is used to set the working mode of the modulator and to start the automatic bias control device. The TEC module includes a first TEC circuit module and a second TEC circuit module. Both the first TEC circuit module and the second TEC circuit module include TEC components and TEC drive circuits; The TEC drive circuit is used to drive TEC components for temperature control. The first TEC circuit module is used for temperature compensation during laser operation; The second TEC circuit module is used to maintain a constant operating temperature for the modulator during operation; The bias circuit module includes an adder circuit and a DAC output circuit and a sine wave generator circuit connected to the input of the adder circuit. The voltage range output by the DAC output circuit can scan and cover at least one full-wave voltage range of the modulator. The voltage output by the DAC output circuit and the signal output by the sine wave generator circuit are combined by an adder circuit to generate an AC signal with the required DC component, which is used to apply the voltage required for the operating point to the DC bias terminal of the modulator. The signal acquisition module includes an optical power detection circuit, a first harmonic filter circuit, and a peak-to-peak value detection circuit connected in sequence. The optical power detection circuit is an IV amplifier circuit, used to detect the optical power value output by the modulator after passing through the spectrometer. The first harmonic filter circuit is a low-frequency filter circuit, used to filter high-frequency signals in the signal output by the modulator after passing through the spectrometer. The peak-to-peak detection circuit is used to detect the amplitude of the first harmonic signal in the signal output by the modulator after passing through the spectrometer; The MCU is used to control the operation of the signal acquisition module and the TEC module, as well as to scan and lock the operating point of the modulator, and to upload the data detected by the signal acquisition module to the host computer. When the working mode is MAX point, if the acquired optical power data P is less than the previous acquired value, the output voltage of the DAC output circuit will be dynamically adjusted. When operating at the MIN point, if the detected optical power value is greater than the previously detected optical power value, the output voltage of the DAC output circuit will be dynamically adjusted. When operating at the Quad point, a 1kHz sine wave signal with a DC component is applied to the bias circuit section, and the amplitude change of the 1kHz optical signal in the signal light output by the modulator is detected to determine whether the signal is stably operating at the Quad point.

2. An automatic bias control device for different operating modes of a modulator as claimed in claim 1, characterized in that: The TEC drive circuit is a hardware circuit based on DRV593.

3. The automatic bias control device applicable to different operating modes of a modulator as described in claim 1, characterized in that: The wavelength of the light output by the laser is matched with the wavelength of the input light to the modulator.

4. An automatic bias control device for different operating modes of a modulator as recited in claim 1, further characterized by: The modulator is a lithium niobate modulator made of thin or thick film material.

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