An FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator

Abstract

The present invention provides an FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator. Using optical power as a criterion, the method uses a step-by-step scan to obtain a rough value of the optimal bias point as the initial value for loop tracking. A DC signal, a dithering signal, and a feedback signal are superimposed on the bias voltage terminal of the electro-optical modulator. The optical power feedback signal is collected, and the ratio of the fundamental amplitude of the dithering signal to the average optical power is calculated and fed into the control loop as an error feedback value. An appropriate loop gain value is set so that the loop outputs a bias voltage feedback value. After a preset time, the error feedback value approaches zero, and the loop enters a stable tracking state, achieving adaptive tracking of the optimal bias point. By using the ratio of the fundamental wave of the dithering signal to the average optical power as the loop feedback signal, the method effectively avoids the influence of changes in input optical power, photodetector responsivity, and insertion loss on bias point tracking, thus achieving adaptive tracking of the optimal bias point of the electro-optical modulator under varying optical link conditions.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to an FPGA-based optimal bias point adaptive tracking method for an electro-optical modulator. Background Art

[0002] Laser communication technology, with its advantages of high speed, wide bandwidth, confidentiality, and flexibility, is increasingly becoming a technological frontier for intersatellite communications worldwide. In laser communication systems, the quality of the modulated optical signal directly impacts the stability of the entire communication system. Mach-Zehnder electro-optical modulators (EOMs), with their wide bandwidth, low power consumption, and low chirp, are widely used in laser communication technology. However, in practice, factors such as temperature fluctuations, external interference, and aging can cause the EO modulator's bias point to drift, resulting in distortion of the modulated optical signal and, in turn, increased bit error rates. Therefore, addressing the problem of EO modulator bias point drift is crucial for ensuring the stable operation of laser communication systems.

[0003] Currently, methods for controlling the optimal bias point of electro-optical modulators are primarily categorized into two types: those with a dither signal and those without. The dither-free approach typically directly detects the optical power output of the electro-optical modulator and uses the position corresponding to the minimum optical power as the optimal bias point. However, optical power fluctuations can significantly affect the determination of the optimal bias point. The dither-added approach typically uses certain characteristics of the dither signal in the electro-optical modulator's output optical signal as loop feedback signals, which then control the loop to track the optimal bias point in real time. Common dither-added methods include the mixing integration method and the harmonic ratio method. The mixing integration method mixes the modulator's output optical power with a local dither signal and then integrates it. The minimum value of the integration result is used as the optimal bias operating point. However, this integration result is significantly affected by optical power fluctuations. The harmonic ratio method calculates the ratio of the second harmonic to the first harmonic corresponding to the dither signal in the modulator's output optical power signal. The position of the maximum harmonic ratio corresponds to the optimal bias operating point. However, this method is computationally intensive, and in practical applications, the second harmonic amplitude fluctuates significantly, resulting in less pronounced waveform effects.

[0004] The first two methods mentioned above cannot avoid the impact of optical power fluctuations on the optimal bias point position. Stable tracking of the optimal bias point can only be achieved by manually adjusting the integral gain or the amplification factor of the amplifier circuit. While the harmonic ratio method can offset the impact of optical power fluctuations, it is computationally intensive and resource-intensive, making it less effective in practical applications.

[0005] Furthermore, optimal bias point control for electro-optic modulators can be achieved through either hardware or software implementation. Hardware implementations are complex, costly, and inflexible. Software implementations primarily differ in the choice of processor. Mainstream processors include microcontrollers, DSPs, ARM processors, and FPGAs. FPGAs, due to their parallel processing capabilities and high computational speed, are more suitable for rapidly tracking the optimal bias point of electro-optic modulators.

[0006] Therefore, a tracking method is needed to avoid the influence of optical power fluctuation on the position of the optimal bias point. Summary of the Invention

[0007] The present invention aims to solve the problem of the influence of optical power fluctuation on the position of the optimal bias point. It provides an FPGA-based method for adaptively tracking the optimal bias point of an electro-optical modulator. The method uses optical power as a criterion and step-scans to obtain a rough value of the optimal bias point as the initial value of the loop tracking. A DC signal, a dither signal, and a feedback signal are superimposed on the bias voltage terminal of the electro-optical modulator. The optical power feedback signal is collected, and the ratio of the fundamental wave amplitude of the dither signal to the average optical power is calculated and sent to the control loop as an error feedback value. An appropriate loop gain value is set so that the loop outputs a bias voltage feedback value. After a preset time, the error feedback value approaches zero, and the loop enters a stable tracking state, thereby achieving adaptive tracking of the optimal bias point. The present invention uses the ratio of the fundamental wave of the jitter signal to the average optical power as the loop feedback signal, offsetting the impact of optical power fluctuations on the loop and effectively avoiding the influence of input optical power, photodetector responsivity, and insertion loss changes on bias point tracking. The present invention uses FPGA as the main controller. Its high-speed parallel processing capability can greatly improve the tracking speed of the optimal bias point compared to processors such as single-chip microcomputers, ARM, and DSP, and can realize adaptive tracking of the optimal bias point of the electro-optical modulator when the optical link changes.

[0008] The present invention provides an FPGA-based method for adaptively tracking the optimal bias point of an electro-optical modulator, comprising the following steps:

[0009] S1. Using optical power as the criterion, the bias voltage end of the electro-optical modulator in the tracking system is step-scanned, and the position of the minimum optical power is used as the rough value of the optimal bias point and the initial value of the loop tracking;

[0010] S2, FPGA superimposes a DC signal, an output jitter signal, and a feedback signal on the bias voltage terminal of the electro-optic modulator;

[0011] S3 and FPGA receive the optical power feedback signal collected by the ADC and photodetector and calculate the error feedback value to be sent to the control loop. The error feedback value is the ratio of the fundamental amplitude of the jitter signal in the optical power feedback signal to the average optical power.

[0012] S4, FPGA sets the loop gain value and outputs the bias voltage feedback value to the electro-optical modulator;

[0013] S5. Determine whether the preset time has been reached. If not, return to step S2. If yes, the loop enters a stable tracking state, and the optimal bias point adaptive tracking method is completed.

[0014] The present invention discloses an FPGA-based adaptive tracking method for an optimal bias point of an electro-optical modulator. Preferably, the tracking system includes: an electro-optical modulator, a laser optically connected to an input end of the electro-optical modulator, a spectroscope and a photodetector optically connected in sequence to an output end of the electro-optical modulator, an ADC and an FPGA electrically connected in sequence to the output end of the photodetector, a first DAC electrically connected in sequence to a radio frequency signal output end of the FPGA, a drive amplifier circuit, and a second DAC electrically connected to a control signal output end of the FPGA; the other output end of the spectroscope is optically connected to a next-stage optical path; the output end of the FPGA is electrically connected to the laser; the output end of the drive amplifier circuit is electrically connected to the radio frequency input end of the electro-optical modulator; and the output end of the second DAC is electrically connected to the control signal input end of the electro-optical modulator.

[0015] FPGA is used for laser control, RF signal output, bias voltage control, optical power feedback value collection and algorithm process control.

[0016] The present invention describes an FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator. Preferably, the spectroscope is a 1:9 spectroscope. After the output light of the electro-optical modulator is split by the spectroscope, 90% of the output light is transmitted as modulated light to the next optical path, and 10% of the output light is fed back to the FPGA via a photodetector for closed-loop control.

[0017] The present invention describes an FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator. As a preferred embodiment, in step S2, the DC signal is a rough value of the optimal bias point, the jitter signal is a low-frequency, low-amplitude sinusoidal signal, and the feedback signal is the bias voltage feedback value in step S4 and the initial value is zero.

[0018] In the FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator described in the present invention, as a preferred embodiment, the frequency and amplitude of the jitter signal are lower than those of the radio frequency signal.

[0019] The present invention provides an FPGA-based electro-optic modulator optimal bias point adaptive tracking method. As a preferred embodiment, the frequency range of the dithering signal is 1 kHz to 10 kHz, and the amplitude range of the dithering signal is 0.05V to 0.1V.

[0020] In the FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator described in the present invention, as a preferred embodiment, in step S3, the error feedback value Ratio is:

[0021]

[0022] Among them, V l is the jitter signal voltage, V π is the half-wave voltage, V dc is the DC bias voltage.

[0023] The present invention provides an FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator, as a preferred embodiment,

[0024] Average optical power for:

[0025]

[0026] Where k is the insertion loss and η is the photodetector responsivity;

[0027] Jitter signal fundamental amplitude P 1st for:

[0028]

[0029] In the FPGA-based electro-optic modulator optimal bias point adaptive tracking method described in the present invention, as a preferred embodiment, in step S3, the sampling rate of the optical power feedback signal is less than the radio frequency.

[0030] The present invention provides an FPGA-based electro-optical modulator optimal bias point adaptive tracking method. As a preferred embodiment, the control logic of the FPGA-based electro-optical modulator optimal bias point adaptive tracking method includes a scanning state machine and a closed-loop state machine, and the end of the scanning state machine is the beginning of the closed-loop state machine.

[0031] The scanning state machine is: initial state bias voltage V bias is 0V, the optimal bias point voltage V Null is 0V, and the scanning step voltage is a fixed value V step , scan the working range of the electro-optic modulator once, determine the voltage value with the minimum feedback optical power value, and obtain the optimal bias point V Null A rough value of

[0032] The closed-loop state machine is: Initial state bias voltage feedback value V fb is 0V, and the jitter signal voltage is V l , bias voltage V bias =V Null +V fb +Vl , where V l <V π , V π is the half-wave voltage, and the ratio of the fundamental amplitude of the jitter signal to the average optical power is sent into the loop as the error feedback value to obtain the updated bias voltage feedback value V fb , after the set time constant τ, the loop is locked.

[0033] This technical solution is: an FPGA-based electro-optic modulator optimal bias point adaptive tracking method, including the following steps:

[0034] S1. Using optical power as the criterion, step-scan the bias voltage end of the electro-optical modulator. The position of the minimum optical power is used as the rough value of the optimal bias point and as the initial value of the loop tracking.

[0035] S2, superimposing a DC signal, a dithering signal, and a feedback signal on the bias voltage terminal of the electro-optic modulator;

[0036] S3 and FPGA calculate the fundamental amplitude of the jitter signal and the average optical power in the feedback signal through the optical power feedback signal collected by the ADC and photodetector, and send the ratio of the two as the error feedback value into the control loop;

[0037] S4. Set the loop gain value to make the loop output bias voltage feedback value;

[0038] S5. Repeat steps S2-S4. After a preset time, the error feedback value approaches zero, and the loop enters a stable tracking state, achieving adaptive tracking of the optimal bias point.

[0039] The implementation device includes an optical modulator, FPGA, laser, photodetector, ADC, DAC, driver amplifier circuit, and spectroscope. The FPGA serves as the master control chip, responsible for laser control, RF signal output, bias voltage control, optical power feedback acquisition, and algorithm flow control. After the electro-optic modulator's output light passes through a 1:9 spectroscope, 90% of the light is transmitted as modulated light to the next stage, and 10% of the light is fed back to the FPGA via a photodetector for closed-loop control.

[0040] The DC signal in step S2 is a rough value of the optimal bias point in step S1, the jitter signal is a low-frequency, low-amplitude sinusoidal signal, and the feedback signal is the bias voltage feedback value generated in step S4 and its initial value is zero.

[0041] The calculation method of the fundamental amplitude of the jitter signal frequency component in the optical power feedback signal in step S3 is: the optical power feedback signal is respectively combined with the local jitter signal V sin , orthogonal signal V cos Multiply them, add them up during the integration period, and then take the modulus. The corresponding calculation formula is:

[0042]

[0043] Where, P fb is the optical power feedback signal, P 1st is the fundamental wave amplitude, and this formula is the formula for realizing the fundamental wave amplitude.

[0044] The frequency and amplitude of the jitter signal are much lower than those of the RF signal, so it will not affect the modulation information.

[0045] The optical power feedback signal is collected at a sampling rate much lower than the RF frequency, which not only avoids interference from RF signals but also reduces the requirements for ADC devices.

[0046] Using the ratio of the fundamental amplitude of the jitter signal frequency component to the average optical power as the error feedback value can effectively mitigate the impact of optical power fluctuations. This conclusion is derived as follows:

[0047] Let P i is the input optical power, P o is the output optical power, and the transfer function of the electro-optic modulator is:

[0048]

[0049] Where k is the insertion loss, V π is the half-wave voltage, V RF is the RF signal voltage, V dc is the DC bias voltage, V l is the jitter signal voltage.

[0050] After the electro-optic modulator's output light passes through the spectroscope, a portion of the light is received by the photodetector. The FPGA controls the ADC to sample at a sampling rate much lower than the RF band. Assuming the photodetector responsivity is η, the optical power feedback signal can be expressed as:

[0051]

[0052] Expand this formula:

[0053]

[0054] Taylor expand the formula, retain the first-order term and sort it out:

[0055]

[0056] From the above formula, it can be concluded that the average optical power is expressed as:

[0057]

[0058] The fundamental amplitude of the jitter signal is expressed as:

[0059]

[0060] Then the ratio of the fundamental amplitude of the jitter signal to the average optical power is:

[0061]

[0062] This formula shows that the ratio of the jitter signal's fundamental amplitude to the average optical power is independent of not only the input optical power but also the insertion loss and responsivity of the photodetector. Therefore, using this ratio as a feedback signal can effectively mitigate the effects of optical link fluctuations.

[0063] The FPGA-based control logic is completed by two state machines, where the end mark of the scanning state machine is the start mark of the closed-loop state machine.

[0064] (1) Scan state machine: initial state bias voltage V bias is 0V, the optimal bias point voltage V Null is 0V, and the scanning step voltage is a fixed value V step Scan the electro-optic modulator within its operating range to determine the voltage value with the minimum feedback optical power, i.e. the optimal bias point V Null Rough value of .

[0065] (2) Closed-loop state machine: initial state bias voltage feedback value V fb is 0V, and the jitter signal is V l , bias voltage V bias =V Null +V fb +V l , where V π >>V l The ratio of the fundamental amplitude of the jitter signal to the average optical power is sent into the loop as the error to obtain the updated bias voltage feedback value V fb After setting the time constant τ, the bias voltage feedback value V fb Stable, loop locked.

[0066] The voltage feedback value is calculated through the power feedback value.

[0067] The present invention has the following advantages:

[0068] (1) It effectively avoids the influence of optical link changes such as input optical power, photodetector responsivity, and insertion loss on bias point tracking, solves the influence of problems such as laser power attenuation and photodetector responsivity reduction caused by long-term operation on bias point tracking, avoids manual operations such as manual modulation of gain value or amplification factor, and improves the adaptability, reliability, and stability of the entire control system.

[0069] (2) Operations such as jitter signal generation, fundamental wave extraction, ratio calculation, and loop control are implemented inside the FPGA, reducing the complexity of the hardware circuit.

[0070] (3) The FPGA control logic adopted is simple and efficient, and fully utilizes the FPGA's parallel processing capabilities, which can achieve optimal bias point tracking faster than other processors. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 The schematic diagram of the structure of an FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator;

[0072] Figure 2 This is a flow chart of an FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator;

[0073] Figure 3 This is the FPGA control logic diagram of an FPGA-based electro-optic modulator optimal bias point adaptive tracking method.

[0074] Reference numerals:

[0075] 1. Electro-optic modulator; 2. FPGA; 3. ADC; 4. Photodetector; 5. Laser; 6. Spectrometer; 7. First DAC; 8. Driver amplifier circuit; 9. Second DAC. DETAILED DESCRIPTION

[0076] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0077] Example 1

[0078] like Figure 1 As shown, an FPGA-based electro-optic modulator optimal bias point adaptive tracking method includes the following steps:

[0079] S1. Using optical power as a criterion, the bias voltage end of electro-optical modulator 1 in the tracking system is step-scanned, and the position of the minimum optical power is used as a rough value of the optimal bias point and the initial value of the loop tracking;

[0080] S2 and FPGA2 superimpose a DC signal, an output jitter signal, and a feedback signal on the bias voltage terminal of the electro-optical modulator 1;

[0081] The DC signal is a rough value of the optimal bias point, the dithering signal is a low-frequency, low-amplitude sinusoidal signal, the feedback signal is the bias voltage feedback value in step S4 and the initial value is zero, the frequency and amplitude of the dithering signal are lower than those of the RF signal, the frequency range of the dithering signal is: 1 kHz to 10 kHz, and the amplitude range of the dithering signal is: 0.05 V to 0.1 V; in this embodiment, the frequency of the dithering signal is 3 kHz, the frequency of the RF signal is 1 GHz, and the amplitude of the dithering signal is 0.1 V;

[0082] S3 and FPGA2 receive the optical power feedback signal collected by ADC3 and photodetector 4 and calculate the error feedback value to be sent to the control loop. The error feedback value is the ratio of the fundamental amplitude of the jitter signal in the optical power feedback signal to the average optical power.

[0083] The error feedback value Ratio is:

[0084]

[0085] Among them, V l is the jitter signal voltage, V π is the half-wave voltage, V dc is the DC bias voltage;

[0086] Average optical power for:

[0087]

[0088] Where k is the insertion loss and η is the photodetector responsivity;

[0089] Jitter signal fundamental amplitude P 1st for:

[0090]

[0091] The sampling rate of the optical power feedback signal is lower than the radio frequency. In this embodiment, the sampling rate of the optical power feedback signal is 100 kHz.

[0092] S4, FPGA2 sets the loop gain value and outputs the bias voltage feedback value to the electro-optical modulator 1;

[0093] S5. Determine whether the preset time has been reached. If not, return to step S2. If yes, the loop enters a stable tracking state, and the optimal bias point adaptive tracking method is completed.

[0094] like Figure 2As shown, the tracking system includes: an electro-optical modulator 1, a laser 5 optically connected to the input end of the electro-optical modulator 1, a spectroscope 6 optically connected to the output end of the electro-optical modulator 1 in sequence, a photodetector 4, an ADC 3 and an FPGA 2 electrically connected to the output end of the photodetector 4 in sequence, a first DAC 7 electrically connected to the radio frequency signal output end of the FPGA 2 in sequence, a driving amplifier circuit 8 and a second DAC 9 electrically connected to the control signal output end of the FPGA 2, the other output end of the spectroscope 5 optically connected to the next-stage optical path, the output end of the FPGA 2 electrically connected to the laser 5, the output end of the driving amplifier circuit 8 electrically connected to the radio frequency input end of the electro-optical modulator 1, and the output end of the second DAC 9 electrically connected to the control signal input end of the electro-optical modulator 1;

[0095] FPGA2 is used for laser control, RF signal output, bias voltage control, optical power feedback value collection and algorithm process control;

[0096] The beam splitter 6 is a 1:9 beam splitter. After the output light of the electro-optical modulator 1 is split by the beam splitter 6, 90% of the output light is transmitted as modulated light to the next optical path, and 10% of the output light is fed back to the FPGA 2 through the photodetector 4 for closed-loop control.

[0097] like Figure 3 As shown, the control logic of the FPGA-based electro-optical modulator optimal bias point adaptive tracking method includes a scanning state machine and a closed-loop state machine, and the end of the scanning state machine is the beginning of the closed-loop state machine;

[0098] The scanning state machine is: initial state bias voltage V bias is 0V, the optimal bias point voltage V Null is 0V, and the scanning step voltage is a fixed value V step , scan once within the working range of the electro-optic modulator 1, determine the voltage value with the minimum feedback optical power value, and obtain the optimal bias point V Null A rough value of

[0099] The closed-loop state machine is: Initial state bias voltage feedback value V fb is 0V, and the jitter signal voltage is V l , bias voltage V bias =V Null +V fb +V l , where V l <V π , V π is the half-wave voltage, and the ratio of the fundamental amplitude of the jitter signal to the average optical power is sent into the loop as the error feedback value to obtain the updated bias voltage feedback value V fb , after the set time constant τ, the loop is locked.

[0100] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. An FPGA-based adaptive tracking method for the optimal bias point of an electro-optical modulator, characterized by: The following steps are involved: S1. Using optical power as a criterion, the bias voltage end of the electro-optical modulator (1) in the tracking system is scanned in steps, and the position of the minimum optical power is used as a rough value of the optimal bias point and the initial value of the loop tracking; S2, FPGA (2) superimposes a DC signal, a jitter signal and a feedback signal on the bias voltage terminal of the electro-optical modulator (1); The DC signal is a rough value of the optimal bias point, the dithering signal is a low-frequency, low-amplitude sinusoidal signal, and the feedback signal is the bias voltage feedback value in step S4 and its initial value is zero; S3, the FPGA (2) receives the optical power feedback signal collected by the ADC (3) and the photodetector (4) and calculates an error feedback value to be sent to the control loop, wherein the error feedback value is the ratio of the fundamental wave amplitude of the jitter signal in the optical power feedback signal to the average optical power; S4, the FPGA (2) sets a loop gain value and outputs a bias voltage feedback value to the electro-optical modulator (1); S5. Determine whether the preset time has been reached. If not, return to step S2. If yes, the loop enters a stable tracking state, and the optimal bias point adaptive tracking method is completed. The tracking system comprises: the electro-optical modulator (1), a laser (5) optically connected to the input end of the electro-optical modulator (1), a spectroscope (6) optically connected to the output end of the electro-optical modulator (1) in sequence, the photodetector (4), the ADC (3) electrically connected to the output end of the photodetector (4) in sequence, the FPGA (2), a first DAC (7) electrically connected to the radio frequency signal output end of the FPGA (2) in sequence, a driving amplifier circuit (8) and a second DAC (9) electrically connected to the control signal output end of the FPGA (2), the other output end of the spectroscope (6) optically connected to the next optical path, the output end of the FPGA (2) electrically connected to the laser (5), the output end of the driving amplifier circuit (8) electrically connected to the radio frequency input end of the electro-optical modulator (1), and the output end of the second DAC (9) electrically connected to the control signal input end of the electro-optical modulator (1); The FPGA (2) is used for laser control, radio frequency signal output, bias voltage control, optical power feedback value collection and algorithm process control; The control logic of the FPGA-based electro-optical modulator optimal bias point adaptive tracking method includes a scanning state machine and a closed-loop state machine, and the end of the scanning state machine is the beginning of the closed-loop state machine; The scanning state machine is: initial state bias voltage 0V, the optimal bias point voltage is 0V, the scanning step voltage is a fixed value , scan once within the working range of the electro-optic modulator (1), determine the voltage value with the minimum feedback light power value, and obtain the optimal bias point A rough value of The closed-loop state machine is: initial state bias voltage feedback value is 0V, and the jitter signal voltage is , bias voltage ,in , The ratio of the fundamental amplitude of the jitter signal to the average optical power is sent into the loop as the error feedback value to obtain an updated bias voltage feedback value. , after setting the time constant After that, the loop is locked.

2. The method for adaptively tracking the optimal bias point of an electro-optical modulator based on FPGA according to claim 1, characterized in that: The spectroscope (6) is a 1:9 spectroscope. After the output light of the electro-optical modulator (1) is split by the spectroscope (6), 90% of the output light is transmitted as modulated light to the next-stage optical path, and 10% of the output light is fed back to the FPGA (2) via the photodetector (4) for closed-loop control.

3. The method for adaptively tracking the optimal bias point of an electro-optical modulator based on FPGA according to claim 1, characterized in that: The frequency and amplitude of the jitter signal are lower than those of the radio frequency signal.

4. The method for adaptively tracking the optimal bias point of an electro-optical modulator based on FPGA according to claim 3, characterized in that: The frequency range of the dithering signal is 1KHz~10KHz, and the amplitude range of the dithering signal is 0.05V~0.1V.

5. The method for adaptively tracking the optimal bias point of an electro-optical modulator based on FPGA according to claim 1, characterized in that: In step S3, the error feedback value Ratio is: ； in, is the jitter signal voltage, is the half-wave voltage, is the DC bias voltage.

6. The method for adaptively tracking the optimal bias point of an electro-optical modulator based on FPGA according to claim 5, characterized in that: Average optical power for: ； Where k is the insertion loss, is the photodetector responsivity; Jitter signal fundamental amplitude for: 。 7. The method for adaptively tracking the optimal bias point of an electro-optical modulator based on FPGA according to claim 1, characterized in that: In step S3, the sampling rate of the optical power feedback signal is lower than the radio frequency.

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