A system for searching for an optimal modulation point of a micro-ring modulator and a feedback control device thereof

Abstract

The application discloses a silicon-based micro-ring optimal modulation point searching system and a feedback control device thereof. The system comprises a pseudo-random sequence generating module, a signal remapping module, a static transmission curve importing module, a signal modulation module, a noise introducing module, a receiving bandwidth limiting module and a error code judging module. The optimal modulation point searching system uses the error code rate as a measurement standard innovatively, combines the measured static transmission curve of the micro-ring modulator, comprehensively considers multiple factors influencing the modulation effect, and establishes the optimal modulation point to be locked by the feedback control device. The feedback control device uses a photoelectric diode, a digital potentiometer, a voltage comparator, a microcontroller and a voltage output module. The searching system determines the optimal modulation point, calculates the position information of the point and sends the position information to the microcontroller, so that the feedback control is completed by controlling the digital potentiometer, the voltage comparator and the voltage output module.

Description

Technical Field

[0001] This invention belongs to the field of modulator detection and control, and relates to a micro-ring modulator optimal modulation point search system and its feedback control device. Background Technology

[0002] With the rapid development of modern information technology, the throughput and bandwidth of data communication urgently need to be improved. Traditional electronic technology is limited by the physical layer of electrical interconnection, and cannot meet the application requirements of high-throughput data exchange in terms of power consumption, latency, heat dissipation, and bandwidth. The emergence of optical interconnect technology has broken through the performance bottleneck of electrical transmission. However, due to the high sensitivity of silicon to temperature changes, in a highly integrated large-scale photonic device system, a transient thermal load on an adjacent device or a slow increase in ambient temperature can cause changes in the operating state of the device.

[0003] Microring modulators are crucial devices in silicon photonics for generating ultra-high frequency RF signals in the optical domain. They are also susceptible to temperature-induced changes in device characteristics, leading to deterioration of RF signal modulation. Fortunately, we can control the temperature of the microring device through feedback control, locking its modulation position to meet operational requirements. However, in optical links, fluctuations in laser source output and changes in link insertion loss can cause fluctuations in the average optical power at the monitoring point, resulting in instability at the locking point of feedback control.

[0004] On the other hand, there is no unified standard in the research field for determining the optimal modulation point of a micro-ring modulator. Most existing technologies use the point of maximum optical modulation amplitude as the optimal modulation point, while others use the point of maximum slope of the micro-ring transmission curve or determine it based on the linearity index—level separation mismatch rate, etc. Factors affecting the final modulation effect of the micro-ring modulator include optical modulation amplitude, static nonlinear distortion caused by the Lorentzian shape of the transmission curve, and dynamic nonlinear distortion caused by the dynamic response. Existing technologies generally only consider one aspect of these factors and do not comprehensively consider all influences. Therefore, finding a metric that can comprehensively consider multiple factors and establishing a model based on it to search for the optimal modulation point is crucial for the feedback control system of the micro-ring modulator. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an optimal modulation point search system for a micro-ring modulator and its feedback control device. The optimal modulation point search system innovatively uses the bit error rate as a metric, combining it with the measured static transmission curve of the micro-ring modulator, and comprehensively considering multiple factors affecting the modulation effect to determine the optimal modulation point that the feedback control system must lock. Furthermore, by incorporating a designed external feedback control device, the optimal modulation point is locked.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention first provides an optimal modulation point search system for silicon-based microrings, comprising:

[0008] A pseudo-random sequence generation module is used to generate the digital code stream of the modulated signal at the transmitting end;

[0009] The signal remapping module is used to remap the second-order signal of the digital code stream generated by the pseudo-random sequence generation module to a fourth-order PAM4 signal.

[0010] The static transmission curve import module is used to import the static transmission curves of the micro-ring modulator under each modulation voltage into the search system and perform curve fitting.

[0011] The signal modulation module is used to modulate the remapped symbol sequence into a power signal stream according to the fitted static transmission curve;

[0012] The noise introduction module is used to introduce Gaussian white noise into the power signal stream modulated by the signal modulation module, thereby interfering with signal transmission.

[0013] The receive bandwidth limiting module includes a digital filter for limiting the bandwidth at the receiving end;

[0014] The bit error rate decision module is used by the receiver to receive and decide the signal output by the receiver bandwidth limitation module to obtain the final bit error rate result.

[0015] The micro-ring modulator optimal modulation point search system scans the optical carrier operating wavelength within the search area, and passes through the above modules sequentially at each operating wavelength; the scan obtains the bit error rate characteristic curve related to the wavelength, and the point with the minimum bit error rate is the optimal modulation point.

[0016] The present invention also provides a feedback control device based on the search system, comprising:

[0017] Two photodiodes (PDs) are respectively positioned at the input and output ends of the micro-ring modulator. They are used to extract optical power information at the flat band and modulation point of the transmission curve of the micro-ring modulator, respectively. The optical power information extracted at the input end enters channel 1, and the optical power information extracted at the output end enters channel 2. The ratio of the two optical powers can be used to determine the current modulation point position, and the ratio is immune to optical power fluctuations.

[0018] The digital potentiometer (DP) is used to convert the current-form monitoring signal output by the photodiode (PD) into a voltage form; it is also used to set the operating wavelength position locked by the feedback circuit.

[0019] The voltage comparator VC is used to sample the monitoring signals of two channels. When the voltage of channel 1 is greater than the voltage of channel 2, the incremental change information output by the voltage comparator is 1; when the voltage of channel 1 is less than the voltage of channel 2, the incremental change information output by the voltage comparator is 0.

[0020] The microcontroller (MCU) is used to control the gain of the digital potentiometer and the output voltage of the power supply module.

[0021] The voltage output module outputs a stable drive voltage signal based on the control signal output by the microcontroller and applies it to the thermoelectrode integrated in the microring modulator.

[0022] As a preferred embodiment of the present invention, after receiving the incremental change information output by the voltage comparator, the microcontroller increases or decreases the feedback control signal accordingly, and outputs it to the voltage output module in the form of a digital signal.

[0023] The microcontroller receives the optimal modulation point search result from the search system. The optimal modulation point position can be described by the ratio of the optical power of the micro-ring modulator at the flat band of the transmission curve and at the optimal modulation point. The microcontroller sets the resistance ratio R2 / R1 of the digital potentiometers on the two channels to the aforementioned optical power ratio, and simultaneously outputs a clock signal to the voltage comparator for sampling. The voltage output module outputs a stable drive voltage signal based on the control signal output by the microcontroller and applies it to the thermoelectric electrode integrated in the micro-ring modulator. The thermoelectric electrode is used to tune the modulation point position of the micro-ring modulator.

[0024] As a preferred embodiment of the present invention, the comparator is a time-controlled comparator, the clock signal is output by a microcontroller, and the clock frequency is related to the sampling rate; the microcontroller is a single-chip microcomputer or implemented using an FPGA; the voltage output module includes a digital-to-analog converter (DAC), and the DAC output voltage is output after rectification and amplification circuits.

[0025] Compared to existing technologies, the search system described in this invention adjusts the optimal modulation point search result according to changes in the measured micro-ring, bias voltage, modulation amplitude, and data transmission rate, making it a more adaptable and personalized solution. Furthermore, the system search result can be combined with a feedback control device to lock onto the optimal modulation point. This feedback control device can resist optical power fluctuations caused by laser source output fluctuations and changes in link insertion loss, improving the stability of the feedback control. The entire system and device are independent of the micro-ring modulator and can be fabricated as an electrical chip, co-packaged with the optical chip, allowing for real-time monitoring and adjustment of the micro-ring modulator's operating position. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the optimal modulation point search system for silicon-based microrings of the present invention.

[0027] Figure 2 This is a flowchart of the receive bandwidth limitation module in the search model.

[0028] Figure 3 These are the principle block diagram and test block diagram of the overall feedback control device of the present invention.

[0029] Figure 4 It is the result of searching for the optimal modulation point based on a certain micro-ring, with -35dBW Gaussian white noise added when the optical carrier input power is 0dBm. Detailed Implementation

[0030] The present invention will be further described and illustrated below with reference to the accompanying drawings and examples.

[0031] like Figure 1 The diagram shows the principle block diagram of the optimal modulation point search system for the silicon-based microring of the present invention. This system uses the bit error rate (BER) as a metric to implement the optimal modulation point search method of the present invention. The system design of the present invention is derived from the actual signal modulation, transmission, and reception processes. The system includes a pseudo-random sequence generation module, a signal remapping module, a static transmission curve import module, a signal modulation module, a noise introduction module, a receive bandwidth limiting module, and a bit error rate determination module.

[0032] The pseudo-random sequence generation module is used to generate the digital bitstream of the modulated signal at the transmitting end. The specific code pattern of this digital bitstream is a pseudo-random bit sequence (PRBS), which most closely resembles the data transmission behavior of a real link and possesses the characteristic of generating near-random data. The sequence length of the digital bitstream needs to be confirmed through prior testing. The specific testing procedure is as follows: a random sequence length is set, and multiple PRBSs are repeatedly generated at this sequence length. The bit error rate (BER) of each generation result is calculated using the optimal modulation point search system of the silicon-based microring of this invention (all parameters of the search system remain unchanged). The BER calculation results are compared. If the deviation of the test results is within the order of 1e-3, the sequence length meets the experimental requirements and can be used as the sequence length of the digital bitstream.

[0033] The signal remapping module is used to remap the second-order signal of the digital code stream generated by the pseudo-random sequence generation module to a fourth-order PAM4 signal. In this invention, the silicon-based microring (microring modulator) uses PAM4 modulation. PAM4 uses four different signal levels for signal transmission, representing four PAM4 symbols: 0, 1, 2, and 3. Each symbol contains 2 bits of digital code stream logic information; therefore, the digital code stream generated by the pseudo-random sequence generation module needs to be remapped. The digital code stream is allocated in groups of 2 bits, with four possible 2-bit allocations: 00, 01, 10, and 11. The correspondence between the 2-bit pairings and the PAM4 symbols is 00-0, 01-1, 10-2, and 11-3. In the signal remapping module, the paired sequences are remapped according to this correspondence to obtain the symbol sequence.

[0034] The static transmission curve import module is used to import the static transmission curves of the micro-ring modulator under various modulation voltages into the optimal modulation point search system of this invention, and perform curve fitting. The static transmission curves are the measured results of the micro-ring modulator; a total of four static transmission curves need to be imported, which are the static transmission curves of the micro-ring operating under the fourth voltage during actual modulation. After importing the four micro-ring static transmission curves, each is fitted and smoothed to obtain four fitted static transmission curves of Lorentzian curve type.

[0035] The signal modulation module modulates the remapped symbol sequence into a power signal stream based on the fitted static transmission curves. The input parameters for the signal modulation module are the remapped PAM4 signal stream and the four fitted static transmission curves. In this module, the optimal modulation point search system of this invention establishes the modulation point for the current bit error rate calculation, converts the PAM4 signal into the power level corresponding to that point on the static transmission curve, simulates the modulation process, and finally outputs the modulated power signal stream.

[0036] The noise introduction module introduces Gaussian white noise into the power signal stream modulated by the signal modulation module to interfere with signal transmission. The purpose of superimposed Gaussian white noise is to demonstrate the anti-interference capability of the modulated signal at each modulation point, and its strength is ultimately quantified using the bit error rate (BER) metric. The Gaussian white noise power setting also requires prior testing confirmation: the power of the added noise is randomly set, a power signal stream with superimposed noise is generated, and the BER simulation is performed on all sampling points (each modulation point) within the search area using the optimal modulation point search system of this invention. If the BER test results at all points within the search area are greater than 0, then the power intensity meets the experimental requirements.

[0037] The receive bandwidth limiting module includes a digital filter used to limit the bandwidth at the receiving end. The specific process of the receive bandwidth limiting module is as follows: Figure 2As shown, the limitation on the reception bandwidth has a differentiated impact on the modulation effect at different transmission rates, and therefore the optimal modulation point searching system of the present invention can find the optimal modulation points at different positions according to rate information. The power signal stream after noise superposition is a sequence signal that does not carry rate information, so each bit needs to be first extended into a long symbol in this module. If the transmission rate is R b (bit / s), the sampling rate is f s , then the number of extended points N per symbol is:

[0038]

[0039] Rate information is added to the extended signal stream, and a filtering result is obtained after passing through a digital filter with limited bandwidth. After the signal passes through the digital filter, phase lag in the time domain will inevitably occur, so it is necessary to discard the first N a sampling points, and the value of N a is determined according to the order N ord of the digital filter.

[0040]

[0041] After the filtering result is aligned, the long symbol signal is down-sampled and restored to a sequence signal, so as to obtain the final signal received by the receiving end.

[0042] The error decision module is used for the receiving end to receive and decide the signal output by the receiving bandwidth limitation layer, so as to obtain the final bit error rate result. The error decision module is the last layer of the model, and serves as the receiving end of the modulation signal in the optimal modulation point searching system of the present invention. The module first calculates the decision threshold of the received signal. The unit of the sequence signal output by the receiving bandwidth limitation module is milliwatt, and the decision threshold is the average value of the corresponding powers of every two adjacent-order symbols. For example, if the corresponding powers of symbol 0 and symbol 1 are P0 and P1 respectively, the decision threshold Pth1=(P0+P1) / 2. After calculating three decision thresholds Pth1, Pth2 and Pth3, the logic for the receiving end to decide the power sequence signal is as follows: when the received signal power P RX < Pth1, the PAM4 symbol is 0; when Pth1 < P RX < Pth2, the PAM4 symbol is 1; when Pth2 < P RX < Pth3, the PAM4 symbol is 2; when Pth3 < P RX , the PAM4 symbol is 3. The PAM4 signal stream obtained after reception and decision is restored to a digital code stream according to the mapping rule of the signal remapping module, and then compared with the code stream at the transmitting end to calculate the bit error rate.

[0043] After calculating the bit error rate by completing the bit error decision, the optimal modulation point search system of the present invention changes the modulation point position to perform simulation calculation for the next modulation point. Finally, after scanning the defined search area, the minimum bit error rate is determined as the optimal modulation point.

[0044] This invention provides a feedback control system against power fluctuation lockout, implemented using an optimal modulation point search model, as detailed below. Figure 3 As shown:

[0045] The main control unit includes two photodiodes (PD), a digital potentiometer (DP), a voltage comparator (VC), a microcontroller (MCU), a host computer, and a voltage output module.

[0046] Two photodiodes are positioned at the input and output ends of the micro-ring modulator, respectively. At each end, 1% of the optical power is coupled out by an optical coupler and fed into the photodiodes. These photodiodes are used to extract optical power information at the flat band and modulation point of the transmission curve, respectively. The optical power information extracted at the input end enters channel 1, and the optical power information extracted at the output end enters channel 2. The ratio of the two optical powers can be used to determine the current modulation point position, and this ratio is immune to optical power fluctuations.

[0047] A digital potentiometer is used to convert the current-form monitoring signal output by a photodiode into a voltage-form signal. It is also used to set the operating wavelength position locked by the feedback circuit. The specific formula for the locking principle is shown below:

[0048]

[0049] Where γ avg For the micro-ring transmission response at the locking point, I1 and I2 are the photocurrents of channel 1 and channel 2, respectively, and R1 and R2 are the resistance values ​​set by the digital potentiometers on channel 1 and channel 2, respectively. The ratio of photocurrents indicates the current modulation point position, and the inverse ratio of digital potentiometer resistance values ​​indicates the target modulation point position. When the two are equal, the feedback voltage remains stable and the locking is successful.

[0050] The voltage comparator is used to sample the monitoring signals of two channels. When the voltage of channel 1 is greater than the voltage of channel 2, the voltage comparator outputs an incremental change information of 1; when the voltage of channel 1 is less than the voltage of channel 2, the voltage comparator outputs an incremental change information of 0.

[0051] After receiving the incremental change information from the voltage comparator output, the microcontroller increases or decreases the feedback control signal accordingly and outputs it to the voltage output module as a digital signal. Additionally, the microcontroller receives the optimal modulation point search result from the search system. The optimal modulation point position can be described by the ratio of the optical power at the flat band of the transmission curve and at the optimal modulation point. The microcontroller sets the resistance ratio R2 / R1 of the two digital potentiometers to the aforementioned optical power ratio and simultaneously outputs a clock signal to the voltage comparator for sampling. Based on the control signal output by the microcontroller, the voltage output module outputs a stable drive voltage signal applied to the thermoelectric electrode integrated within the micro-ring modulator (the thermoelectric electrode is used to tune the modulation point position of the micro-ring modulator).

[0052] Figure 3 The overall feedback control system shown also includes a test link section. When in use, the micro-loop modulator outputs to the actual application optical network; when testing and verifying the optimal modulation point search model and its feedback control system, it outputs to the test system. The test end is first connected to a low-noise amplifier erbium-doped fiber amplifier to compensate for the optical power loss after splitting, then to a high-speed photodetector to down-convert and demodulate the modulated signal on the optical carrier into an electrical signal, and finally to a sampling oscilloscope or bit error rate meter to measure the signal quality or bit error rate obtained from the actual modulation, transmission, and reception. The test results can verify the accuracy of the optimal modulation point search model built in this invention.

[0053] Figure 3 The dashed box outside the optical link represents the high-speed signal modulation optical carrier link at the transmitting end in a practical application. A code generator produces a high-speed code signal. After being amplified to a suitable modulation amplitude by a microwave amplifier, the signal is added to the DC voltage output from a DC voltage source at a DC bias terminal. Finally, this signal is applied to the micro-ring modulator as a modulation signal via a probe. The laser source in the optical link outputs laser light, and a polarization controller controls the polarization state of the laser in the single-mode fiber. The laser light is then input to the micro-ring modulator as an optical carrier. After the signal is modulated onto the optical carrier, it is output to the test system or the actual application optical network.

[0054] Figure 4 The figure shows the simulation results of the model described in this invention. The four Lorentz lines in the figure are the fitted static transmission curves of the micro-ring modulator operating under fourth-order voltage. The two curves with annotations are the bit error rate (BER) result curve and the symbol error rate (SER) result curve, respectively. As can be seen from the figure, after the model scans the search region, the BER first decreases monotonically on the micro-ring resonant side and then increases rapidly, with a minimum value existing within the region. This point is the optimal modulation point obtained from the simulation. Based on the location of this point, setting the ratio of the resistance values ​​of the two digital potentiometers to the ratio of the optical power at the aforementioned optimal modulation point will achieve locking at the optimal modulation point.

[0055] Previous technologies have primarily locked the optimal modulation point at the minimum average optical power at the output end. This point is near the resonant wavelength of the microring's static transmission curve, with an offset limited to a few picometers. However, in practical applications, the optimal modulation point of the microring modulator may lie outside this range. The optimal modulation point search system of this invention expands the search range to a nanometer-level offset to the resonant wavelength. It uses the received bit error rate of the modulation signal as a metric to find the optimal modulation point within this range, ensuring that the microring modulator operates at this point for optimal modulation performance in practical applications. Furthermore, the location of the minimum average optical power does not change with the modulation signal rate; therefore, the target modulation position locked by existing technologies is unaffected by the modulation signal rate, which contradicts the bandwidth limitations of practical applications. The optimal modulation point search system of this invention includes a digital filter in its receiving bandwidth limiting layer to restrict the receiving bandwidth. Therefore, the optimal modulation point searched by the model changes according to the signal rate in practical applications, allowing the microring modulator to operate at the optimal modulation point at different signal rates.

[0056] The above description illustrates one implementation of this solution. Furthermore, this solution can also be adopted by changing the MCU's control algorithm and the DAC's output, combined with other modulators such as series-parallel MZM modulators. It should be noted that some details of this solution may change in practical applications. Improvements or adjustments made based on the general framework of this invention are still within the limitations of this patent. The scope of protection of this invention is determined by the appended claims.

Claims

1. A micro-ring modulator optimal modulation point search system, characterized in that... include: A pseudo-random sequence generation module is used to generate the digital code stream of the modulated signal at the transmitting end; The signal remapping module is used to remap the second-order signal of the digital code stream generated by the pseudo-random sequence generation module to a fourth-order PAM4 signal. The static transmission curve import module is used to import the static transmission curves of the micro-ring modulator under each modulation voltage into the search system and perform curve fitting. The static transmission curves imported by the static transmission curve import module are the measured results of the silicon-based micro-ring. A total of four static transmission curves need to be imported, which are the static transmission curves of the micro-ring operating under the fourth voltage in the actual modulation process. After the four micro-ring static transmission curves are imported, they are each fitted and smoothed to obtain four fitted static transmission curves. The fitted curve type is Lorentz line type. The signal modulation module is used to modulate the remapped symbol sequence into a power signal stream according to the fitted static transmission curve; The noise introduction module is used to introduce Gaussian white noise into the power signal stream modulated by the signal modulation module, thereby interfering with signal transmission. The receive bandwidth limiting module includes a digital filter for limiting the bandwidth at the receiving end; the specific process of the receive bandwidth limiting module is as follows: Since the power signal stream after noise superposition is a sequential signal and does not include rate information, in the receiving bandwidth limiting module, each bit is first extended into a long symbol. If the transmission rate is R... b The sampling rate is f s Then the number of extension points N for each symbol is: (1) The expanded signal stream now includes rate information, and the filtered result is obtained after passing through a bandwidth-limited digital filter. Since the signal will inevitably experience phase lag in the time domain after passing through the digital filter, the initial N values ​​must be discarded. a N sampling points a The value is based on the order N of the digital filter. ord Sure: (2) After the filtering results are aligned, the long symbol signal is downsampled and restored to a sequence signal to obtain the final signal received by the receiver. The bit error rate decision module is used by the receiver to receive and decide the signal output by the receiver bandwidth limitation module to obtain the final bit error rate result. The micro-ring modulator optimal modulation point search system scans the optical carrier operating wavelength within the search area, and passes through the above modules sequentially at each operating wavelength; the scan obtains the bit error rate characteristic curve related to the wavelength, and the point with the minimum bit error rate is the optimal modulation point.

2. The micro-ring modulator optimal modulation point search system according to claim 1, characterized in that, The digital code stream generated by the pseudo-random sequence generation module is a pseudo-random bit sequence (PRBS). The sequence length of the digital bitstream needs to be confirmed by prior testing. The specific testing procedure is as follows: randomly set the sequence length, generate multiple PRBSs repeatedly under the sequence length, and calculate the bit error rate of each generation result through the micro-ring modulator optimal modulation point search system. All parameters of the search system remain unchanged. Compare the bit error rate calculation results. If the deviation of the test results is within the order of 1e-3, the sequence length meets the requirements and is taken as the sequence length of the digital bitstream.

3. The micro-ring modulator optimal modulation point search system according to claim 1, characterized in that, The silicon-based microring selects PAM4 modulation. PAM4 uses four different signal levels for signal transmission. The four signal levels represent four PAM4 symbols: 0, 1, 2, and 3. Each symbol contains 2 bits of digital code stream logic information. Therefore, the digital code stream generated by the pseudo-random sequence generation module needs to be remapped. The digital code stream is allocated in groups of 2 bits, with four possible 2-bit allocations: 00, 01, 10, and 11. The correspondence between the 2-bit pairings and the PAM4 symbols is 00-0, 01-1, 10-2, and 11-3. In the signal remapping module, the paired sequences are remapped according to the correspondence to obtain the symbol sequence.

4. The optimal modulation point search system for a micro-ring modulator according to claim 1, characterized in that, The input parameters of the signal modulation module are the remapped PAM4 signal stream and the four fitted static transmission curves. In this signal modulation module, the search system establishes the modulation point for bit error rate calculation and converts the PAM4 signal into the power level corresponding to the static transmission curve at the modulation point, simulates the modulation process, and finally outputs the modulated power signal stream.

5. The micro-ring modulator optimal modulation point search system according to claim 1, characterized in that, The power of the Gaussian white noise introduced by the noise introduction module needs to be confirmed by prior testing: the power of the noise is randomly set, the power signal stream after the noise is superimposed is generated, and the bit error rate is simulated for all sampling points in the search area through the search system. If the bit error rate test results at each point in the search area are greater than 0, then the power intensity meets the requirements.

6. A feedback control device based on the search system of claim 1, characterized in that... include: Two photodiodes (PDs) are respectively positioned at the input and output ends of the micro-ring modulator. They are used to extract optical power information at the flat band and modulation point of the transmission curve of the micro-ring modulator, respectively. The optical power information extracted at the input end enters channel 1, and the optical power information extracted at the output end enters channel 2. The ratio of the two optical powers is used to determine the current modulation point position, and the ratio is immune to optical power fluctuations. The digital potentiometer (DP) is used to convert the current-form monitoring signal output by the photodiode (PD) into a voltage form; it is also used to set the operating wavelength position locked by the feedback circuit. The voltage comparator VC is used to sample the monitoring signals of two channels. When the voltage of channel 1 is greater than the voltage of channel 2, the incremental change information output by the voltage comparator is 1; when the voltage of channel 1 is less than the voltage of channel 2, the incremental change information output by the voltage comparator is 0. The microcontroller (MCU) is used to control the gain of the digital potentiometer and the output voltage of the power supply module. The voltage output module outputs a stable drive voltage signal based on the control signal output by the microcontroller and applies it to the thermoelectrode integrated in the microring modulator.

7. The feedback control device according to claim 6, characterized in that, After receiving the incremental change information output by the voltage comparator, the microcontroller increases or decreases the feedback control signal accordingly and outputs it to the voltage output module in the form of a digital signal. The microcontroller receives the optimal modulation point search result from the search system. The optimal modulation point position is described by the ratio of the optical power of the micro-ring modulator at the flat band of the transmission curve and at the optimal modulation point. The microcontroller sets the resistance ratio R2 / R1 of the digital potentiometers on the two channels to the aforementioned optical power ratio, and simultaneously outputs a clock signal to the voltage comparator for sampling. The voltage output module outputs a stable drive voltage signal based on the control signal output by the microcontroller and applies it to the thermoelectric electrode integrated in the micro-ring modulator. The thermoelectric electrode is used to tune the modulation point position of the micro-ring modulator.

8. The feedback control device according to claim 7, characterized in that, The comparator is a time-controlled comparator, and the clock signal is output by a microcontroller. The clock frequency is related to the sampling rate. The microcontroller can be a single-chip microcomputer or implemented using an FPGA. The voltage output module includes a digital-to-analog converter (DAC), and the DAC output voltage is output after rectification and amplification circuits.

Images