Microwave frequency measurement method and device based on microwave photon technology

Abstract

The application discloses a microwave frequency measurement method and device based on microwave photon technology, and belongs to the technical field of microwave photon frequency measurement. The method constructs multiple-level evaluation models of optical carrier quality coefficient, modulation transmission coefficient, detection quantization coefficient and wavelength-dispersion adaptability, performs comprehensive quantization analysis on key parameters of the system, and dynamically determines the target modulator bias point voltage drift based on the coefficients, so as to realize real-time optimization of the system state. The application overcomes the defects of insufficient adaptability to parameter drift and environmental change in the prior art, and significantly improves the precision, stability and reliability of the microwave frequency measurement.

Description

Technical Field

[0001] This invention belongs to the field of microwave photonic frequency measurement technology, and particularly relates to a microwave frequency measurement method and device based on microwave photonic technology. Background Technology

[0002] With the rapid development of modern radar, communication, and electronic countermeasures systems, higher demands are being placed on the high-precision, real-time measurement of microwave frequencies. Microwave frequency measurement methods based on microwave photonics technology have become a research hotspot in this field due to their advantages such as large bandwidth, low loss, and resistance to electromagnetic interference.

[0003] Currently, common microwave photonic frequency measurement methods mainly rely on techniques such as dispersion effects, frequency-amplitude mapping, or optical filtering to achieve frequency discrimination. However, these methods mostly depend on the static calibration of system parameters, and in practical applications, they are easily affected by factors such as light source drift, modulator bias point fluctuations, fiber dispersion variations, and detector response nonlinearities, leading to decreased measurement accuracy or even failure.

[0004] Existing technologies lack comprehensive evaluation and dynamic correction mechanisms for the coupling effects of multiple system parameters, making it difficult to maintain optimal measurement conditions, especially during long-term operation or environmental changes. Furthermore, existing solutions often focus on optimizing single components, failing to establish a collaborative optimization model across the entire chain from light source, modulation, transmission to detection, thus hindering the improvement of overall system performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a microwave frequency measurement method and apparatus based on microwave photonics technology, thus solving the aforementioned problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a microwave frequency measurement method based on microwave photonics technology, comprising: The optical carrier quality coefficient is determined based on the light source linewidth, the stability of the light source output power, and the cutoff frequency of the photodetector. The modulation transmission coefficients are determined based on the half-wave voltage of the electro-optic modulator, the return loss of the modulator's RF input segment, and the fiber optic link length accuracy. The detection quantization coefficient is determined based on the responsivity of the photodetector, the gain flatness of the back-end amplifier, and the absolute error of the power meter. Based on the stability of the light source center wavelength and the accuracy of the fiber optic link dispersion coefficient under the optical carrier quality coefficient and modulation transmission coefficient, the wavelength-dispersion fit is determined. The target modulator bias point voltage drift is determined based on wavelength-dispersion fit, detection quantization coefficient, and current modulator bias point voltage drift.

[0007] Based on the above technical solutions, the present invention also provides the following optional technical solutions: A further technical solution: The method for confirming the target modulator bias point voltage drift is as follows: the detection quantization coefficient and the wavelength-dispersion fit are compared with a target wavelength-dispersion fit to generate an adjustment factor; the current modulator bias point voltage drift is combined with the adjustment factor, and the target modulator bias point voltage drift is calculated through a nonlinear feedback relationship, wherein the adjustment factor is configured to drive the target drift to change in the correction direction when the wavelength-dispersion fit deviates from the target value.

[0008] A further technical solution: The method for obtaining the wavelength-dispersion fit is as follows: To obtain the stability of the center wavelength of the light source and the accuracy of the dispersion coefficient of the fiber optic link; Based on the stability of the center wavelength of the light source and in combination with the optical carrier quality coefficient, a weighted effective wavelength drift is determined, wherein the optical carrier quality coefficient is used to correct the actual impact of the wavelength stability on the system. Based on the dispersion coefficient accuracy of the optical fiber link and in combination with the modulation transmission coefficient, a weighted effective dispersion deviation is determined, wherein the modulation transmission coefficient is used to correct the actual impact of the dispersion accuracy on the system. The effective wavelength shift and the effective dispersion deviation are compared with preset maximum allowable values ​​to obtain a wavelength shift index and a dispersion deviation index. Based on the wavelength drift index and the dispersion deviation index, the wavelength-dispersion fit is determined by a multi-parameter joint attenuation model.

[0009] Further technical solution: The detection quantization coefficient is obtained as follows: To obtain the responsivity of the photodetector, the gain flatness of the back-end amplifier, and the absolute error of the power meter; The responsivity index is obtained by comparing the detector responsivity with the corresponding reference value. The flatness index is obtained by comparing the gain flatness of the back-end amplifier with the maximum allowable gain difference. The error index is obtained by comparing the absolute error of the power meter with the maximum allowable measurement error. The detection quantization coefficient is determined based on the response index, flatness index, and error index.

[0010] A further technical solution: The modulation transmission coefficient is obtained as follows: Obtain the half-wave voltage of the electro-optic modulator, the return loss of the modulator's RF input segment, and the accuracy of the fiber optic link length; The voltage exponent is obtained by performing inverse function processing on the square of the ratio of the half-wave voltage of the electro-optic modulator to the voltage reference value. The return loss of the modulator's RF input section and the fiber optic path length accuracy are compared with the corresponding reference values ​​to obtain the loss index and length accuracy index. The modulation transmission coefficients are determined based on the voltage index, loss index, and length accuracy index.

[0011] A further technical solution: The optical carrier quality coefficient is obtained as follows: Obtain the light source linewidth, light source output power stability, and photodetector cutoff frequency; The linewidth of the light source, the stability of the light source output power, and the cutoff frequency of the photodetector are compared with the corresponding reference values ​​to obtain the linewidth index, the power stability index, and the detector bandwidth index. The optical carrier quality coefficient is determined based on the linewidth index, power stability index, and detector bandwidth index.

[0012] Further technical solution: Based on the linewidth index, power stability index, and detector bandwidth index, the steps to determine the optical carrier quality coefficient are as follows: The response index, flatness index, and error index are weighted and fused, wherein the response index contributes to the fusion result through a saturation growth relationship, and the flatness index and error index contribute to the fusion result through a decay relationship, thereby obtaining the detection quantization coefficient.

[0013] Further technical solution: Based on the voltage index, loss index, and length accuracy index, the steps to determine the modulation transmission coefficient are as follows: Based on the voltage index, loss index, and length accuracy index, the modulation transmission coefficient is determined by a product attenuation function, wherein the voltage index is used as the product term, and the loss index and length accuracy index are used as attenuation terms.

[0014] Further technical solution: Based on the linewidth index, power stability index, and detector bandwidth index, the steps to determine the optical carrier quality coefficient are as follows: Based on the linewidth index, power stability index, and detector bandwidth index, the optical carrier quality coefficient is determined by a composite influence function, wherein the linewidth index and detector bandwidth index together constitute the first attenuation term, and the power stability index constitutes the second contribution term.

[0015] The microwave frequency measurement device based on microwave photonics technology adopts the microwave frequency measurement method based on microwave photonics technology described above.

[0016] This invention provides a microwave frequency measurement method and apparatus based on microwave photonics technology, which has the following advantages compared with the prior art: 1. This invention constructs a multi-level parameter model, including optical carrier quality coefficient, modulation transmission coefficient, and detection quantization coefficient, to achieve real-time quantitative evaluation of the performance of each component of the system, providing a reliable basis for system status monitoring and optimization; 2. Based on the synergistic analysis of wavelength-dispersion fit and detection quantization coefficient, this invention can dynamically adjust the modulator bias voltage, effectively suppressing the influence of environmental factors such as light source drift and dispersion fluctuation on measurement accuracy. 3. This invention establishes a closed-loop optimization mechanism from light source, modulation, transmission to detection, thereby improving the overall system performance under multi-parameter coupling and significantly enhancing the accuracy and long-term stability of frequency measurement. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0020] Please see Figure 1 The microwave frequency measurement method and apparatus based on microwave photonics technology, provided in one embodiment of the present invention, include: The optical carrier quality coefficient is determined based on the light source linewidth (3-dB spectral linewidth of the laser), the light source output power stability (standard deviation of optical power fluctuation), and the cutoff frequency of the photodetector (3-dB cutoff frequency). The modulation transmission coefficient is determined based on the half-wave voltage of the electro-optic modulator, the return loss of the modulator's RF input segment (reflection coefficient of the modulator's RF input), and the fiber optic link length accuracy (absolute error of the fiber length). The detection quantization coefficient is determined based on the photodetector's responsivity (photoelectric conversion efficiency), the gain flatness of the back-end amplifier (the difference between the maximum and minimum gain within the frequency band), and the power meter's absolute error. Based on the stability of the center wavelength of the light source (the output wavelength drift of the laser) under the optical carrier quality coefficient and the modulation transmission coefficient, and the accuracy of the fiber optic link dispersion coefficient (the deviation between the actual value and the design value of the dispersion coefficient), the wavelength-dispersion fit is determined. The target modulator bias point voltage drift is determined based on wavelength-dispersion fit, detection quantization coefficient, and current modulator bias point voltage drift.

[0021] Compared to existing technologies that focus on a single parameter or perform static calibration, such as attempting adjustment by monitoring the wavelength drift of the light source but ignoring its coupling effect with fiber dispersion, this application introduces optical carrier quality coefficient, modulation transmission coefficient, detection quantization coefficient, and wavelength... Dispersion adaptability is used to construct a comprehensive, multi-dimensional performance evaluation system. These coefficients are not isolated but interconnected and synergistic, jointly reflecting the end-to-end performance of the system from optical signal generation, modulation, transmission to electrical signal detection. Furthermore, existing technologies lack dynamic correction mechanisms; once system parameters drift, measurement accuracy decreases. Based on the above multi-dimensional evaluation results, this application can dynamically determine the target modulator bias point voltage drift. This target value directly guides the system to perform precise bias point adjustments, thereby achieving real-time optimization and correction of system performance. This dynamic adjustment capability allows the system to proactively adapt to and maintain high-precision measurement in the face of environmental changes or component aging. Moreover, existing technologies focus on optimizing single links, failing to improve overall system performance. The technical solution of this application quantifies and couples key parameters from multiple links such as light source, modulation, transmission, and detection, forming a full-link collaborative optimization model. For example, wavelength... Determining the dispersion fit comprehensively considers the optical carrier quality coefficient and the modulation transmission coefficient, reflecting the intrinsic relationship between different components. Therefore, the system can identify performance bottlenecks holistically and perform global optimization, rather than just local improvements. This comprehensive evaluation and dynamic correction strategy enables the microwave frequency measurement method of this application to effectively overcome the accuracy degradation problems caused by parameter drift and coupling effects in existing technologies, significantly improving the long-term stability and measurement accuracy of the system in complex dynamic environments. Preferably, the method for obtaining the target modulator bias point voltage drift is as follows: Based on wavelength-dispersion adaptability, detection quantization coefficient, and current modulator bias point voltage drift, the target modulator bias point voltage drift is determined, which can be determined by a drift optimization model. The method for confirming the target modulator bias point voltage drift is as follows: the detection quantization coefficient and the wavelength-dispersion fit are compared with a target wavelength-dispersion fit to generate an adjustment factor; the current modulator bias point voltage drift is combined with the adjustment factor, and the target modulator bias point voltage drift is calculated through a nonlinear feedback relationship, wherein the adjustment factor is configured to drive the target drift to change in the correction direction when the wavelength-dispersion fit deviates from the target value; Specifically, the drift amount of the target modulator bias point voltage can be determined by a drift amount optimization model, which is expressed as follows: ; in, This indicates the voltage drift at the target modulator bias point. This indicates the current modulator bias point voltage drift. Indicates the detection quantization coefficient. Indicates wavelength-dispersion fit. This indicates the target wavelength-dispersion fit.

[0022] The drift optimization model quantifies and predicts the ideal adjustment amount of the modulator bias voltage. Its purpose is to address the fact that in microwave photonic frequency measurement systems, the modulator bias voltage can drift due to environmental changes, device aging, and other factors, affecting modulation efficiency and measurement accuracy. This optimization model allows for the acquisition of a more optimal target bias voltage drift based on real-time system parameters (such as the detection quantization coefficient and wavelength-dispersion fit) and the current bias voltage drift. This guides system adjustments to maintain or restore optimal operating conditions. (Target wavelength-dispersion fit) This parameter represents the degree of matching between wavelength and dispersion characteristics under ideal or desired operating conditions. It is a preset reference value, typically representing the wavelength-dispersion fit level of the system at its optimal performance. The purpose of this parameter is to provide a benchmark for the drift optimization model, enabling the model to assess the deviation between the current system's wavelength-dispersion fit and the ideal state, and adjust the modulator bias point voltage accordingly. This value can be set according to system design requirements, experimental calibration results, or historical operating data. For example, it can be set to the optimal fit value measured during factory calibration, or a high fit threshold determined through simulation or experimentation in a specific application scenario.

[0023] The solution in this application introduces a drift optimization model to optimize key performance indicators (such as the detection quantization coefficient) in microwave photonic frequency measurement systems. Wavelength-dispersion fit This model correlates the current modulator bias point voltage drift with the modulator bias point voltage drift, thereby enabling intelligent adjustment of the modulator bias point voltage. Specifically, the model uses the current modulator bias point voltage drift as a reference. Based on this, the target modulator bias point voltage drift is calculated using a correction factor. In the correction factor The item is the core, comprehensively considering the system's detection quantification capability (by...). Characterization) and the degree of matching between wavelength and dispersion (by Adaptability to target (the difference characterization), when detecting the quantization coefficient A higher value (close to 1) indicates good system detection accuracy; when the wavelength-dispersion fit is high... Approaching target fit When this occurs, it indicates that the system is operating close to an ideal state. At this point, the value of the correction term will approach zero, causing the target drift to decrease. With current drift amount If the difference is close, the system requires no major adjustments. Conversely, if... lower or and A large deviation indicates a decline in system performance, and the correction term will produce a significant non-zero value, thereby guiding the target drift. The system is adjusted in a direction that optimizes system performance. This feedback mechanism, based on real-time system performance parameters, means that the adjustment of the modulator bias point voltage is no longer a simple fixed compensation, but can adaptively respond to changes in the system state, ensuring the accuracy and stability of microwave frequency measurements.

[0024] Through the above technical solution, the microwave photonic frequency measurement method can achieve accurate and adaptive determination of the modulator bias point voltage drift. This method no longer relies on simple fixed compensation or empirical adjustments, but instead introduces a drift optimization model that incorporates the system's detection performance and wavelength-dispersion matching, allowing the calculation of the target drift to dynamically reflect the system's current actual operating state. This helps the system intelligently adjust the modulator bias point voltage in the face of environmental changes or device aging, thereby effectively suppressing the impact of bias point drift on modulation efficiency and measurement accuracy, ensuring the long-term stability and high accuracy of microwave frequency measurements.

[0025] Preferably, the wavelength-dispersion fit is obtained as follows: Obtain the stability of the center wavelength of the light source (the amount of laser output wavelength drift) and the accuracy of the fiber optic link dispersion coefficient (the deviation between the actual value and the design value of the dispersion coefficient). The effective wavelength drift is determined based on the center wavelength stability of the light source and the optical carrier quality coefficient. Specifically, a weighted effective wavelength drift is determined based on the center wavelength stability of the light source and the optical carrier quality coefficient. The optical carrier quality coefficient is used to correct for the actual impact of the wavelength stability on the system. Specifically, the effective wavelength shift can be determined by an effective wavelength shift model, which is expressed as follows: ; in, Indicates the effective wavelength shift. Indicates the stability of the center wavelength of the light source. Indicates the wavelength correction factor. Indicates the optical carrier quality factor; The effective dispersion deviation is determined based on the fiber optic link dispersion coefficient accuracy and the modulation transmission coefficient. Specifically, a weighted effective dispersion deviation is determined based on the fiber optic link dispersion coefficient accuracy and the modulation transmission coefficient, wherein the modulation transmission coefficient is used to correct the actual impact of the dispersion accuracy on the system. Specifically, the effective dispersion deviation can be determined by an effective dispersion deviation model, which is expressed as follows: ; in, Indicates the effective dispersion deviation. Indicates the accuracy of the dispersion coefficient of the fiber optic link. Indicates the dispersion correction factor. Indicates the modulation transmission coefficient; The wavelength drift index is obtained by processing the ratio of the effective wavelength drift to the maximum allowable drift. The dispersion deviation index is obtained by taking the ratio of the effective dispersion deviation to the maximum permissible dispersion deviation. The wavelength-dispersion fit is determined based on the wavelength drift index and the dispersion deviation index. Specifically, the wavelength-dispersion fit is determined by a multi-parameter joint attenuation model based on the wavelength drift index and the dispersion deviation index. Specifically, the wavelength-dispersion fit can be determined by a wavelength-dispersion fit model, which is expressed as follows: ; in, Indicates wavelength-dispersion fit. Indicates the wavelength shift index. The index representing the dispersion deviation is described above. The larger the value, the better the system performs.

[0026] Among them, the center wavelength stability of the light source refers to the degree of fluctuation in the output wavelength of the laser during operation. This drift may be caused by factors such as temperature changes, current fluctuations, or device aging. Its function is to reflect the long-term reliability of the light source and its impact on measurement accuracy. It can be achieved by real-time monitoring with a high-precision spectrometer or by reducing drift through built-in temperature control and current stabilization circuits. The dispersion coefficient accuracy of the fiber optic link refers to the difference between the actual measured value and the theoretical design value of the dispersion coefficient in the fiber optic link. Dispersion causes different wavelengths of light signals to travel at different speeds in the fiber, thus causing signal distortion. Its function is to quantify the impact of the fiber optic link on signal transmission quality. It can be achieved by precise measurement with a time-domain dispersion meter or by estimation and calibration using detailed specifications provided by the fiber optic manufacturer. Effective wavelength shift refers to the corrected wavelength shift after considering the influence of the optical carrier quality coefficient on the stability of the light source's center wavelength. Its function is to more accurately reflect the actual impact of light source wavelength shift on system performance. The wavelength correction factor is a parameter used to adjust the degree of influence of the light source's center wavelength stability on the effective wavelength shift. Its function is to weight the sensitivity of wavelength shift based on specific system characteristics and experimental data. This can be achieved through experimental calibration and optimization, or by pre-setting an empirical value according to system design requirements. Effective dispersion deviation refers to the corrected dispersion deviation after considering the influence of the modulation transmission coefficient on the accuracy of the fiber optic link's dispersion coefficient. Its function is to more accurately reflect the actual impact of fiber optic link dispersion deviation on system performance. The dispersion correction factor is a parameter used to adjust the degree of influence of the fiber optic link's dispersion coefficient accuracy on the effective dispersion deviation. Its function is to weight the sensitivity of dispersion deviation based on specific system characteristics and experimental data. This can be achieved through dynamic adjustment using a system adaptive algorithm, or by manual calibration. The maximum permissible drift refers to the maximum allowable wavelength shift of the light source's center wavelength that the system can tolerate while ensuring normal operation and meeting performance specifications. Its function is to serve as a benchmark for normalization, converting the actual drift into a dimensionless exponent. This can be determined through system design specifications or derived through statistical analysis of long-term operational data. The maximum permissible dispersion deviation refers to the maximum allowable deviation of the fiber optic link's dispersion coefficient that the system can tolerate while ensuring normal operation and meeting performance specifications. Its function is also to serve as a benchmark for normalization, converting the actual dispersion deviation into a dimensionless exponent. This can be determined through industry standards or experimental verification, or set based on the system's tolerance to dispersion. The wavelength drift exponent is a dimensionless parameter obtained by comparing the effective wavelength drift with the maximum permissible drift. Its function is to quantify the relative degree of wavelength drift, facilitating subsequent model calculations.The dispersion deviation index is a dimensionless parameter obtained by comparing the effective dispersion deviation with the maximum permissible dispersion deviation. Its function is to quantify the relative degree of dispersion deviation, which facilitates subsequent model calculations.

[0027] Through the above technical solution, this application enables a more refined and accurate quantitative evaluation of the wavelength and dispersion characteristics in a microwave photonic frequency measurement system. By introducing effective wavelength drift and effective dispersion deviation, and combining them with optical carrier quality coefficient and modulation transmission coefficient for correction, the problem of insufficient evaluation of these key parameters in traditional methods is overcome, allowing the actual impact of wavelength and dispersion on system performance to be more realistically reflected. Furthermore, by converting these corrected parameters into dimensionless exponents and using a wavelength-dispersion fit model for comprehensive evaluation, an intuitive and quantitative index is provided to characterize the system's operating state. This precise fit evaluation provides a more reliable and accurate input for subsequent optimization of the target modulator bias point voltage drift, thereby significantly improving the accuracy of microwave frequency measurement and the overall robustness of the system, effectively avoiding measurement errors caused by poor wavelength and dispersion fit.

[0028] Preferably, the detection quantization coefficient is obtained in the following way: Obtain the responsivity (photoelectric conversion efficiency) of the photodetector, the gain flatness (the difference between the maximum and minimum gain in the frequency band) of the back-end amplifier, and the absolute error of the power meter; The responsivity index is obtained by comparing the detector responsivity with the corresponding reference value. The flatness index is obtained by comparing the gain flatness of the back-end amplifier with the maximum allowable gain difference. The error index is obtained by comparing the absolute error of the power meter with the maximum allowable measurement error. The detection quantization coefficient is determined based on the response index, flatness index, and error index. Specifically, the response index, flatness index, and error index are weighted and fused, wherein the response index contributes to the fusion result through a saturation growth relationship, and the flatness index and error index contribute to the fusion result through a decay relationship, thereby obtaining the detection quantization coefficient. Specifically, the detection quantization coefficient can be determined by a detection quantization model, which is expressed as follows: ; in, Indicates the detection quantization coefficient. Indicates the responsiveness index. Indicates the flatness index. Indicates the error index. Represents the weight coefficient and The Furthermore, the larger the value, the higher the detection quantification accuracy.

[0029] Obtaining the responsivity of the photodetector, the gain flatness of the back-end amplifier, and the absolute error of the power meter provides the raw data foundation for evaluating the performance of the detection system. The responsivity of the photodetector measures its efficiency in converting optical signals into electrical signals, typically obtained by measuring the ratio of its current output to the optical power input at a specific wavelength. The gain flatness of the back-end amplifier reflects the consistency of the amplifier's amplification capability across different frequencies within its operating band; a smaller difference indicates less signal distortion. The absolute error of the power meter represents the maximum deviation between the power meter's measurement result and the true value, and is a crucial parameter for assessing measurement accuracy. These parameters can be obtained in real-time through laboratory calibration, manufacturer datasheets, or online monitoring systems. For example, the responsivity of the photodetector can be obtained by illuminating the detector with a standard light source of known power and measuring the output current; gain flatness can be obtained by measuring the amplifier's gain at different frequencies using a sweep frequency analyzer and calculating the difference between its maximum and minimum gain; the absolute error of the power meter is usually provided by calibration certificates or specifications. To unify these parameters with different dimensions and physical meanings for comprehensive evaluation, this application introduces a ratio processing mechanism. The responsivity index is obtained by comparing the detector responsivity with a corresponding reference value. This index directly reflects the detector's performance. For example, an ideal or benchmark responsivity value can be set as a reference; the higher the actual responsivity, the larger the responsivity index, indicating better detector performance. The flatness index is obtained by comparing the gain flatness of the back-end amplifier with the maximum allowable gain difference. This index quantifies the amplifier's performance consistency within its operating frequency band. Weighting coefficients are parameters used to adjust the importance of different factors in decision-making; they can be determined through preset strategies or the analytic hierarchy process (AHP).

[0030] Through the above technical solution, this application provides a systematic and quantitative method for obtaining detection quantization coefficients. This method transforms key parameters such as the responsivity of the photodetector, the gain flatness of the back-end amplifier, and the absolute error of the power meter into standardized exponents, and then uses a detection quantization model for comprehensive evaluation, accurately reflecting the overall performance of the detection link. This allows for a more precise consideration of the actual performance of the detection link when determining the voltage drift at the target modulator bias point, effectively avoiding measurement errors caused by insufficient detection accuracy assessment, thereby significantly improving the accuracy and reliability of microwave frequency measurement. The introduction of this quantization coefficient provides an objective and comparable performance indicator for the entire microwave frequency measurement system, which is helpful for system optimization and maintenance, and ensures the stability and consistency of measurement results.

[0031] Preferably, the modulation transmission coefficient is obtained in the following way: Obtain the half-wave voltage of the electro-optic modulator, the return loss of the modulator's RF input section (reflection coefficient at the modulator's RF input), and the fiber optic link length accuracy (absolute error in fiber length). The voltage exponent is obtained by taking the square of the ratio of the half-wave voltage of the electro-optic modulator to the voltage reference value and then performing inverse function processing on the square. , Indicates the voltage index. Indicates half-wave voltage. (Indicates voltage reference value); The return loss of the modulator's RF input section and the fiber optic path length accuracy are compared with the corresponding reference values ​​to obtain the loss index and length accuracy index. The modulation transmission coefficient is determined based on the voltage index, loss index, and length accuracy index. Specifically, the modulation transmission coefficient is determined by a product attenuation function based on the voltage index, loss index, and length accuracy index, wherein the voltage index is used as a product term, and the loss index and length accuracy index are used as attenuation terms. Specifically, the modulation transmission coefficients can be determined by a modulation transmission model, which is expressed as follows: ; in, Represents the modulation transmission coefficient, Indicates the voltage index. This represents the loss index. The length precision index is indicated by the following. Furthermore, the larger the value, the higher the modulation and transmission efficiency.

[0032] The half-wave voltage of an electro-optic modulator refers to the voltage that changes the phase of the output optical signal of the electro-optic modulator. The voltage required for the radian is a key parameter for measuring the electro-optic conversion efficiency of the modulator, directly affecting the modulator's ability to convert electrical signals into optical signals. It can be obtained through transmission curve fitting or small-signal derivation (requiring knowledge of the modulator type). The return loss (reflection coefficient at the modulator's RF input) refers to the ratio of the energy reflected back from the RF input of the electro-optic modulator due to impedance mismatch to the incident energy. Lower return loss indicates higher efficiency of the RF signal entering the modulator and less energy loss. It can be achieved by optimizing the impedance matching network design of the modulator's RF input port, such as using matching resistors, inductors, or capacitors, or by selecting RF connectors and transmission lines with good impedance characteristics, or by using directional couplers and power meters. Fiber optic link length accuracy (absolute error in fiber length) refers to the absolute deviation between the actual fiber optic link length and the designed or nominal length. The accuracy of fiber optic link length is crucial for phase matching and delay control in microwave photonic links, especially when frequency measurements are involved. Length error can introduce additional phase noise or frequency drift. This can be achieved by employing high-precision fiber cleaving and splicing techniques, using a sophisticated optical time domain reflectometer (OTDR) for length measurement and calibration, or integrating temperature compensation mechanisms to reduce fiber length changes caused by thermal expansion. Voltage index It is achieved by adjusting the half-wave voltage of the electro-optic modulator. With voltage reference value The square value obtained by performing a ratio operation followed by a reciprocal function operation is called. This index quantifies the impact of the modulator's half-wave voltage on modulation transmission efficiency. A higher value generally indicates that the modulator can achieve effective modulation at lower voltages, thus improving modulation efficiency. Loss Index The return loss index is obtained by comparing the return loss of the modulator's RF input section with a corresponding reference value. This index reflects the impact of the RF signal reflection loss at the modulator input on the modulation transmission efficiency. The smaller the loss index, the higher the RF signal transmission efficiency. Length accuracy index The length accuracy index is obtained by comparing the fiber optic link length precision with a corresponding reference value. This index quantifies the impact of fiber optic link length error on modulation transmission efficiency. The smaller the length accuracy index, the closer the fiber optic link length is to the ideal value, and the smaller the negative impact on modulation transmission. Modulation transmission coefficient It is a comprehensive parameter used to quantify the overall efficiency of the electro-optic modulation process in a microwave photonic link. It takes into account factors such as the half-wave voltage of the electro-optic modulator, the return loss of the RF input section, and the accuracy of the fiber optic link length. Determining this coefficient is crucial for accurately evaluating and optimizing the performance of the microwave photonic link. The larger the value, the higher the modulation and transmission efficiency and the stronger the system's ability to modulate and transmit microwave signals.

[0033] Through the above technical solution, this application can achieve a more refined and accurate quantification of modulation and transmission efficiency in microwave photonic links. By comprehensively considering key factors such as the half-wave voltage of the electro-optic modulator, the return loss of the RF input segment, and the accuracy of the fiber optic link length, and converting them into a unified exponential form, the modulation and transmission coefficients are then calculated using a modulation and transmission model, effectively avoiding evaluation biases that may exist in traditional methods. This allows for a more precise and accurate quantification of effective dispersion deviation and wavelength. The determination of dispersion fit is more reliable, which significantly improves the overall accuracy and stability of microwave frequency measurement methods based on microwave photonics technology, ensuring that high-confidence measurement results can be obtained even in complex environments.

[0034] Preferably, the optical carrier quality coefficient is obtained in the following way: Obtain the light source linewidth (3-dB spectral linewidth of the laser), the light source output power stability (standard deviation of optical power fluctuation), and the cutoff frequency of the photodetector (3-dB cutoff frequency). The linewidth of the light source, the stability of the light source output power, and the cutoff frequency of the photodetector are compared with the corresponding reference values ​​to obtain the linewidth index, the power stability index, and the detector bandwidth index. The optical carrier quality coefficient is determined based on the linewidth index, power stability index, and detector bandwidth index. Specifically, the optical carrier quality coefficient is determined by a composite influence function based on the linewidth index, power stability index, and detector bandwidth index. The linewidth index and detector bandwidth index together constitute the first attenuation term, and the power stability index constitutes the second contribution term. Specifically, the optical carrier quality coefficient can be determined through an optical carrier quality model, which is expressed as follows: ; in, Indicates the optical carrier quality factor. Indicates the line width index. Indicates the power stability index. The detector bandwidth index is represented by the following. Furthermore, the higher the value, the better the optical carrier quality.

[0035] Among these, obtaining the light source linewidth (laser 3-dB spectral linewidth), light source output power stability (standard deviation of optical power fluctuation), and photodetector cutoff frequency (3-dB cutoff frequency) is fundamental to evaluating optical carrier quality. Light source linewidth refers to the width of the laser's output spectrum, usually measured in 3-dB bandwidth. It reflects the purity of the laser frequency; the narrower the linewidth, the better the laser's coherence and the higher its frequency stability. It can be obtained directly through a spectral analyzer, such as using a Fabry-Perot interferometer, or indirectly through techniques such as self-heterodyne or delayed self-heterodyne. Light source output power stability refers to the stability of the laser's output optical power over time. The smaller the standard deviation of optical power fluctuation, the more stable the light source output. This can be obtained by monitoring the light source output over a long period with an optical power meter and calculating its power fluctuation standard deviation, or by using a photodiode for real-time monitoring and statistical analysis through a data acquisition system. The cutoff frequency (3-dB cutoff frequency) of a photodetector refers to the frequency range in which the photodetector can effectively respond. It is usually defined as the frequency at which the responsivity decreases by 3dB. It determines the detector's ability to respond to high-frequency signals. It can be obtained by measuring the detector's response to different frequency optical signals with a spectrum analyzer or by consulting the technical specifications provided by the detector manufacturer.

[0036] Through the above technical solution, this application provides a comprehensive and quantitative method for evaluating optical carrier quality. This method comprehensively considers key factors such as the linewidth of the light source, output power stability, and the bandwidth of the photodetector, and transforms them into standardized indices. By substituting these indices into a specific optical carrier quality model, the optical carrier quality coefficient can be accurately calculated. This refined evaluation avoids the limitations of single-parameter evaluation and ensures a comprehensive understanding of optical carrier quality. In microwave frequency measurement methods based on microwave photonics technology, the accurate optical carrier quality coefficient can serve as a basis for subsequent wavelength measurements. The reliable input for dispersion fit calculation significantly improves the accuracy and stability of the entire measurement system, effectively avoids measurement errors caused by inaccurate optical carrier quality assessment, and thus enhances the overall performance of microwave frequency measurement.

[0037] As an embodiment of the present invention, a microwave frequency measurement device based on microwave photonics technology adopts the above-described microwave frequency measurement method based on microwave photonics technology.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A microwave frequency measurement method based on microwave photonics technology, characterized in that, include: The optical carrier quality coefficient is determined based on the light source linewidth, the stability of the light source output power, and the cutoff frequency of the photodetector. The modulation transmission coefficients are determined based on the half-wave voltage of the electro-optic modulator, the return loss of the modulator's RF input segment, and the fiber optic link length accuracy. The detection quantization coefficient is determined based on the responsivity of the photodetector, the gain flatness of the back-end amplifier, and the absolute error of the power meter. Based on the stability of the light source center wavelength and the accuracy of the fiber optic link dispersion coefficient under the optical carrier quality coefficient and modulation transmission coefficient, the wavelength-dispersion fit is determined. The target modulator bias point voltage drift is determined based on wavelength-dispersion fit, detection quantization coefficient, and current modulator bias point voltage drift.

2. The microwave frequency measurement method based on microwave photonics technology according to claim 1, characterized in that, The method for confirming the voltage drift at the bias point of the target modulator is as follows: the detection quantization coefficient and the wavelength-dispersion fit are compared with a target wavelength-dispersion fit to generate an adjustment factor; The current modulator bias point voltage drift is combined with the adjustment factor, and the target modulator bias point voltage drift is calculated through a nonlinear feedback relationship. The adjustment factor is configured to drive the target drift to change in the correction direction when the wavelength-dispersion fit deviates from the target value.

3. The microwave frequency measurement method based on microwave photonics technology according to claim 2, characterized in that, The wavelength-dispersion fit is obtained as follows: To obtain the stability of the center wavelength of the light source and the accuracy of the dispersion coefficient of the fiber optic link; Based on the stability of the center wavelength of the light source and in combination with the optical carrier quality coefficient, a weighted effective wavelength drift is determined, wherein the optical carrier quality coefficient is used to correct the actual impact of the wavelength stability on the system. Based on the dispersion coefficient accuracy of the optical fiber link and in combination with the modulation transmission coefficient, a weighted effective dispersion deviation is determined, wherein the modulation transmission coefficient is used to correct the actual impact of the dispersion accuracy on the system. The effective wavelength shift and the effective dispersion deviation are compared with preset maximum allowable values ​​to obtain a wavelength shift index and a dispersion deviation index. Based on the wavelength drift index and the dispersion deviation index, the wavelength-dispersion fit is determined by a multi-parameter joint attenuation model.

4. The microwave frequency measurement method based on microwave photonics technology according to claim 2, characterized in that, The detection quantization coefficient is obtained as follows: To obtain the responsivity of the photodetector, the gain flatness of the back-end amplifier, and the absolute error of the power meter; The responsivity index is obtained by comparing the detector responsivity with the corresponding reference value. The flatness index is obtained by comparing the gain flatness of the back-end amplifier with the maximum allowable gain difference. The error index is obtained by comparing the absolute error of the power meter with the maximum allowable measurement error. The detection quantization coefficient is determined based on the response index, flatness index, and error index.

5. The microwave frequency measurement method based on microwave photonics technology according to claim 3, characterized in that, The modulation transmission coefficients are obtained as follows: Obtain the half-wave voltage of the electro-optic modulator, the return loss of the modulator's RF input segment, and the accuracy of the fiber optic link length; The voltage exponent is obtained by performing inverse function processing on the square of the ratio of the half-wave voltage of the electro-optic modulator to the voltage reference value. The return loss of the modulator's RF input section and the fiber optic path length accuracy are compared with the corresponding reference values ​​to obtain the loss index and length accuracy index. The modulation transmission coefficients are determined based on the voltage index, loss index, and length accuracy index.

6. The microwave frequency measurement method based on microwave photonics technology according to claim 3, characterized in that, The optical carrier quality coefficient is obtained as follows: Obtain the light source linewidth, light source output power stability, and photodetector cutoff frequency; The linewidth of the light source, the stability of the light source output power, and the cutoff frequency of the photodetector are compared with the corresponding reference values ​​to obtain the linewidth index, the power stability index, and the detector bandwidth index. The optical carrier quality coefficient is determined based on the linewidth index, power stability index, and detector bandwidth index.

7. The microwave frequency measurement method based on microwave photonics technology according to claim 6, characterized in that, The steps for determining the optical carrier quality coefficient based on the linewidth index, power stability index, and detector bandwidth index are as follows: The response index, flatness index, and error index are weighted and fused, wherein the response index contributes to the fusion result through a saturation growth relationship, and the flatness index and error index contribute to the fusion result through a decay relationship, thereby obtaining the detection quantization coefficient.

8. The microwave frequency measurement method based on microwave photonics technology according to claim 5, characterized in that, The steps for determining the modulation transmission coefficients based on the voltage index, loss index, and length accuracy index are as follows: Based on the voltage index, loss index, and length accuracy index, the modulation transmission coefficient is determined by a product attenuation function, wherein the voltage index is used as a product term, and the loss index and length accuracy index are used as attenuation terms.

9. The microwave frequency measurement method based on microwave photonics technology according to claim 6, characterized in that, The steps for determining the optical carrier quality coefficient based on the linewidth index, power stability index, and detector bandwidth index are as follows: Based on the linewidth index, power stability index, and detector bandwidth index, the optical carrier quality coefficient is determined by a composite influence function, wherein the linewidth index and detector bandwidth index together constitute the first attenuation term, and the power stability index constitutes the second contribution term.

10. A microwave frequency measurement device based on microwave photonics technology, characterized in that, The microwave frequency measurement method based on microwave photonics technology as described in any one of claims 1-9 is adopted.

Images