Method of controlling an operating point of an electro-optical modulator and optical fiber sensing system

Abstract

The application provides a control method for an operating point of an electro-optical modulator and an optical fiber sensing system, and the control method comprises the following steps: in a system initialization stage, performing global scanning and collecting corresponding optical power response data; calculating an initialization completion degree and a real-time drift rate; when the initialization completion degree and / or the real-time drift rate meet a mode switching threshold condition, switching from a global scanning mode to a local scanning mode to realize seamless connection of the two modes; taking a bias voltage corresponding to a preliminary minimum point of a response curve obtained by global scanning as a center of an initial range of local scanning, collecting corresponding optical power response data, and calculating a frequency domain characteristic value E; taking the frequency domain characteristic value E as a judgment basis, analyzing a signal frequency domain energy distribution law, and when the frequency domain characteristic value E meets a preset condition, locking a bias voltage corresponding to the frequency domain characteristic value E as the operating point of the electro-optical modulator, so that the method can effectively filter out environmental noise and circuit interference and accurately lock the operating point.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and more particularly to a method for controlling the operating point of an electro-optic modulator and a fiber optic sensing system. Background Technology

[0002] Fiber optic sensing technology, with its advantages of resistance to electromagnetic interference, high sensitivity, and distributed measurement capabilities, is widely used in industrial monitoring, energy exploration, and smart grids. The electro-optic modulator (EOM) is the core modulation device in a fiber optic sensing system. Its performance, especially the stability of its operating point (typically the lowest point of the transmission response curve, denoted by Null), directly determines the system's measurement accuracy and signal-to-noise ratio.

[0003] Existing EOM (Electronic Optical Memory) operating point control methods typically perform a global scan during system initialization to locate the operating point, followed by a switch to a local scan mode for fine-tuning and locking. However, existing technologies have the following drawbacks: First, the switching logic between global and local scans is simplistic, usually based solely on the scan completion signal or a fixed time threshold. This fails to dynamically adapt to rapid or slow drifts caused by environmental disturbances (such as temperature drift or mechanical vibration), resulting in lag during periods of severe disturbance or excessive scanning during stable periods, wasting resources. Second, during the local scan phase, traditional methods often employ a time-domain optical power threshold method to determine the operating point, which is highly susceptible to random environmental noise and fixed-frequency interference from the circuit. This leads to inaccurate operating point locking, a high false alarm rate, and difficulty in meeting the requirements of high-precision, high-interference-resistant fiber optic sensing applications. Summary of the Invention

[0004] Based on this, the present invention provides a method for controlling the operating point of an electro-optic modulator and an optical fiber sensing system to solve at least one of the above-mentioned problems.

[0005] This application provides a method for controlling the operating point of an electro-optic modulator, including:

[0006] During the system initialization phase, the electro-optic modulator is controlled to enter the global scanning mode to perform a global scan and collect the corresponding optical power response data.

[0007] Calculate initialization completion rate and real-time drift rate ;

[0008] When the initialization completion rate And / or the real-time drift rate When the mode switching threshold condition is met, the electro-optic modulator is controlled to switch from the global scanning mode to the local scanning mode. The local scanning mode uses the bias voltage corresponding to the initial minimum point of the response curve obtained by fitting the global scanning as the initial range center of the local scanning, collects the corresponding optical power response data, and calculates the frequency domain feature value E.

[0009] In local scanning mode, the frequency domain feature value E is used as the discrimination criterion. When the frequency domain feature value E meets the preset conditions, the bias voltage corresponding to the frequency domain feature value E is locked as the operating point of the electro-optic modulator.

[0010] Optionally, the mode switching threshold condition is the initialization completion rate. Greater than or equal to the initialization completion threshold , and / or, when the real-time drift rate Less than or equal to the preset drift rate threshold ;

[0011] Optionally, the method for controlling the operating point of the electro-optic modulator further includes continuously monitoring the real-time drift rate during a local scan. When detected Then, the electro-optic modulator is controlled to switch from the local scanning mode to the global scanning mode, wherein, The preset drift rate threshold;

[0012] Optionally, the method for controlling the operating point of the electro-optic modulator further includes continuously monitoring the real-time drift rate during a local scan. When detected Then, the electro-optic modulator is controlled to maintain a local scanning mode, wherein, This is a preset drift rate threshold.

[0013] Optionally, the initialization completion degree The calculation formula is:

[0014] ;

[0015] ;

[0016] in, , These are the weighting coefficients. Indicates the number of valid sampling points. This indicates the preset theoretical number of sampling points; This indicates the goodness of fit of the curve obtained by fitting the response curve of the global scan. This represents the preset goodness-of-fit threshold;

[0017] Optionally, the real-time drift rate The calculation method is as follows:

[0018] The operating point bias voltage is continuously acquired for Q sampling periods. The voltage offset per unit time is calculated through linear regression, based on the real-time drift rate. The calculation formula for obtaining the real-time drift rate The real-time drift rate The calculation formula is:

[0019] ;

[0020] in, Let Q be the maximum offset of the operating point bias voltage within each of the Q cycles. This represents the corresponding time interval.

[0021] Optionally, the steps of the global scanning mode include performing a global scan within a preset global bias voltage range, and acquiring the optical signals of the electro-optic modulator at different bias voltages point by point, wherein the global bias voltage range covers the rated driving voltage range of the electro-optic modulator.

[0022] And / or,

[0023] The steps of the local scanning mode include performing a local scan within a preset local bias voltage range, acquiring optical signals of the electro-optic modulator under different bias voltages, and calculating the frequency domain characteristic value E corresponding to each bias voltage point based on the optical signal corresponding to each acquired bias voltage point.

[0024] Optionally, the frequency domain eigenvalue E is calculated as follows:

[0025] Preprocess the discrete sampling sequence x[n] of the optical signal acquired by local scanning;

[0026] Calculate the total energy characterization parameters Fundamental frequency energy characterization parameters and second harmonic energy characterization parameters ;

[0027] According to the formula The normalized frequency domain eigenvalues ​​E are calculated; where,

[0028] ;

[0029] ;

[0030] ;

[0031] ;

[0032] ;

[0033] in, These are the normalization coefficients; The preset theoretical number of sampling points; , , This is the energy weighting coefficient.

[0034] Optionally, the preset condition is that the frequency domain feature value E tends to a stable peak value; the step of determining that the frequency domain feature value E meets the preset condition includes:

[0035] Calculate the frequency domain eigenvalue E in the current local scan mode;

[0036] If the frequency domain eigenvalue E is greater than or equal to the peak threshold If Y%, and the fluctuation amplitude of the frequency domain feature value E within q consecutive sampling periods is less than the preset fluctuation threshold, then it is determined that the frequency domain feature value E meets the preset condition, the bias voltage corresponding to the current local scanning mode is determined as a candidate point, and the electro-optic modulator operating point is determined based on the candidate point.

[0037] If the frequency domain eigenvalue E is less than the peak threshold If Y%, then the local scanning direction is adjusted according to the trend of the frequency domain characteristic value E changing with voltage until the frequency domain characteristic value E meets the preset condition. Then, the bias voltage corresponding to the current local scanning mode is used as the candidate point, and the operating point of the electro-optic modulator is determined according to the candidate point. , .

[0038] Optionally, the preset condition is that the frequency domain feature value E tends to a stable peak value; the step of determining that the frequency domain feature value E meets the preset condition includes:

[0039] Calculate the frequency domain eigenvalue E in the current local scan mode;

[0040] If the frequency domain eigenvalue E is greater than or equal to the peak threshold If Y%, and the fluctuation amplitude of the frequency domain feature value E is less than the preset fluctuation threshold within q consecutive sampling periods, then it is determined that the frequency domain feature value E meets the preset condition, the bias voltage corresponding to the current local scanning mode is determined as a candidate point, and further interference verification is performed.

[0041] If the frequency domain eigenvalue E is less than the peak threshold If Y%, then the local scanning direction is adjusted according to the trend of frequency domain characteristic value E changing with voltage until the frequency domain characteristic value E meets the preset condition. Then, the bias voltage corresponding to the current local scanning mode is used as the candidate point, and further interference verification is performed. , ;

[0042] The interference verification steps include:

[0043] Calculate the characteristic frequency energy ratio γ, frequency domain entropy H, and interference frequency suppression ratio K of the optical signal acquired by local scanning;

[0044] When both conditions are met , , When the characteristic frequency energy ratio γ, frequency domain entropy H, and interference frequency suppression ratio K satisfy the secondary screening conditions, the current bias voltage is recorded as the candidate point obtained after the secondary screening, and the operating point of the electro-optic modulator is determined based on the candidate point.

[0045] like , , If any one of the conditions is not met, based on frequency domain entropy The scanning direction is adjusted by changing the direction of the change, and the scanning continues until the characteristic frequency energy ratio γ, frequency domain entropy H, and interference frequency suppression ratio K are determined to meet the secondary screening conditions. The current bias voltage is recorded as the candidate point obtained after secondary screening, and the electro-optic modulator operating point is determined based on the candidate point.

[0046] in, The minimum characteristic frequency energy percentage is preset. The preset minimum entropy threshold, This is the preset suppression ratio threshold.

[0047] Optionally, determining the operating point of the electro-optic modulator based on candidate points includes:

[0048] For the candidate points that pass the verification, the frequency domain eigenvalues ​​are continuously monitored. Compared with interference suppression ratio ;

[0049] If frequency domain eigenvalues The fluctuation range exceeds Z% or Then, a local scan mode is activated to correct the bias voltage of the operating point and compensate for minor drifts caused by environmental disturbances. ;

[0050] If frequency domain eigenvalues Compared with interference frequency rejection ratio If the value remains within the threshold range, the corresponding candidate point is determined to be the stable operating point of the electro-optic modulator.

[0051] Optionally, the characteristic frequency energy ratio γ is calculated by performing a Fourier transform on the optical signal acquired through local scanning to obtain a frequency domain spectrum, and then calculating the characteristic frequency. Calculate the corresponding peak spectral energy Total energy of the entire frequency band The ratio of the characteristic frequency energy proportions is obtained. ,in, ;

[0052] And / or,

[0053] The frequency domain entropy The calculation method involves dividing the frequency domain spectrum after Fourier transform into... Calculate the energy percentage for each frequency range. According to frequency domain entropy The calculation formula is obtained, where, , ;

[0054] And / or,

[0055] The method for calculating the interference frequency suppression ratio K is to calculate the characteristic frequency for fixed frequency interference. peak energy With interference frequency peak energy The ratio of the two values ​​is the interference frequency suppression ratio. ,in, .

[0056] Based on the same inventive concept, this application also provides an optical fiber sensing system, including a photodetector, a signal conditioning circuit, a first analog-to-digital converter, a control unit, a second analog-to-digital converter, and an electro-optic modulator;

[0057] The control unit is used to store and execute the control method for the operating point of the electro-optic modulator provided in the first aspect, obtain the bias voltage of the operating point of the electro-optic modulator, and lock it at the operating point.

[0058] The method for controlling the operating point of an electro-optic modulator provided in this embodiment of the invention includes: performing a global scan and acquiring corresponding optical power response data during the system initialization phase; and calculating the initialization completion degree. and / or real-time drift rate When initialization completion degree and real-time drift rate When one of the conditions meets the threshold, the system switches from global scanning mode to local scanning mode to achieve seamless connection between the two modes. Using the bias voltage corresponding to the initial lowest point of the response curve obtained from global scanning as the center, a local scan is performed to collect the corresponding optical power response data and calculate the frequency domain characteristic value E. Based on the frequency domain characteristic value E, by analyzing the signal frequency domain energy distribution law, when the frequency domain characteristic value E meets the preset condition, the bias voltage corresponding to the frequency domain characteristic value E is locked as the operating point of the electro-optic modulator. This method can effectively filter out environmental noise and circuit interference and accurately lock the operating point of the electro-optic modulator.

[0059] Compared with the prior art, the present invention has at least the following beneficial effects:

[0060] First, by using a dual-parameter switching algorithm of "initialization completion rate - real-time drift rate", seamless coordination between global scanning and local scanning modes is achieved, dynamically adapting to changes in operating conditions.

[0061] Second, the frequency domain feature value E is introduced as the core discrimination criterion in the local scanning stage, replacing the traditional power threshold method, which significantly improves the anti-interference capability and the working point locking accuracy. Attached Figure Description

[0062] Figure 1 A hardware system logic block diagram of a method for controlling the operating point of an electro-optic modulator provided in an embodiment of the present invention;

[0063] Figure 2 A schematic diagram of the transmission response curve of an electro-optic modulator provided in an embodiment of this application;

[0064] Figure 3 A flowchart illustrating a method for controlling the operating point of an electro-optic modulator, provided in an embodiment of the present invention. Detailed Implementation

[0065] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the present application and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present application are shown in the drawings, not the entire structure. Various modifications and variations can be made to the present application without departing from its spirit or scope, which will be apparent to those skilled in the art. Therefore, the present application is intended to cover modifications and variations of the present application that fall within the scope of the technical solutions claimed in the corresponding claims and their equivalents. It should be noted that the implementation methods provided in the embodiments of the present application can be combined with each other without contradiction.

[0066] Figure 1 This invention provides a hardware system logic block diagram of a method for controlling the operating point of an electro-optic modulator. Figure 2 A schematic diagram of the transmission response curve of an electro-optic modulator provided in an embodiment of this application is shown below. Figure 1 and Figure 2 This application provides an optical fiber sensing system, which can serve as the hardware system for the control method of the operating point of the electro-optic modulator (EOM) provided in the following embodiments. The system mainly includes a photodetector (PD), a impedance amplifier and signal amplification integrated module (TIA&Amp), an analog-to-digital converter (ADC), a control unit (Processor), and an electro-optic modulator (EOM). The system uses the control unit (Processor) with the operating point control method deployed as the core control node. (Refer to...) Figure 1 Its module collaboration and signal flow logic is as follows:

[0067] The externally input optical signal is received by the photodetector (PD) and converted into a weak current signal. After being conditioned into an analog signal by the transimpedance amplification and signal amplification integrated module (TIA&Amp), it is input into the analog-to-digital converter (ADC) and converted into a digital signal.

[0068] The control unit (processor) receives the digital signal and processes it based on the built-in electro-optic modulator operating point (Null) control method to obtain the bias voltage corresponding to the electro-optic modulator (EOM) operating point. Based on the bias voltage, a new digital control signal is generated and output to the digital-to-analog converter (DAC).

[0069] The control unit (processor) can be an integrated circuit (IC), processor, microprocessor, such as a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof, and stores a calculation program that executes the control method of the electro-optic modulator operating point (Null).

[0070] A digital-to-analog converter (DAC) converts the received digital control signal into an analog voltage signal, which is then amplified (e.g., ...). Figure 1 The digital control signal shown (12V OP-Amp) is ultimately input to the electro-optic modulator bias module (EOM Bias). The EOM Bias module then generates a precise bias voltage corresponding to the operating point of the electro-optic modulator (EOM) and applies it to the EOM, ultimately locking the EOM at its operating point. Figure 2 As shown. Among them, Figure 2 The horizontal axis represents the bias voltage V, and the vertical axis represents the output power P.

[0071] For example, in some applications that require generating high extinction ratio light pulses, such as optical time domain reflectometers (OTDRs), the electro-optic modulator (EOM) needs to be locked at the lowest point of the transmission curve. In this way, when no modulation signal is applied, the output light is almost zero, thus achieving a very clean pulse switching effect.

[0072] This application embodiment achieves precise and dynamic control of the electro-optic modulator (EOM) operating point through a closed-loop hardware architecture of optical signal conversion, electrical signal conditioning, digital computation, and analog driving, adapting to the complex operating conditions of fiber optic sensing systems.

[0073] This application focuses on achieving "high efficiency and precision" in locating the operating point of an electro-optic modulator (EOM). It optimizes the entire process of EOM operating point locating, summarizing the control method as follows: An innovative switching algorithm is employed between global and local scans, determining the switching timing based on two parameters: initialization completion and / or real-time drift rate, achieving seamless transition between global and local scan modes. Local scanning uses frequency domain characteristic values ​​as the core discrimination criterion. By analyzing the signal's frequency domain energy distribution, compared to the traditional power threshold method, it effectively filters out environmental noise and circuit interference, accurately locating the operating point.

[0074] The following explains in detail the method for controlling the operating point of the electro-optic modulator provided in the embodiments of this application.

[0075] Based on the same inventive concept, this embodiment provides a method for controlling the operating point of an electro-optic modulator. Figure 3 A flowchart of a method for controlling the operating point of an electro-optic modulator provided in an embodiment of the present invention, in conjunction with... Figures 1-3 This embodiment provides a method for controlling the operating point of an electro-optic modulator, the method comprising:

[0076] Step S1: During the system initialization phase, control the electro-optic modulator to enter the global scanning mode, perform a global scan, and collect the corresponding optical power response data.

[0077] Step S2: Calculate the initialization completion rate and real-time drift rate When initialization completion degree When the real-time drift rate meets the mode switching threshold condition, the electro-optic modulator is controlled to switch from global scanning mode to local scanning mode.

[0078] Step S3: In the local scanning mode, the bias voltage corresponding to the initial lowest point of the response curve obtained from the global scanning fitting is used as the initial range center of the local scan. The corresponding optical power response data is collected, and the frequency domain characteristic value E is calculated.

[0079] Step S4: In local scanning mode, using the frequency domain feature value E as the criterion, when the frequency domain feature value E meets the preset condition, the bias voltage corresponding to the frequency domain feature value E is locked as the operating point of the electro-optic modulator. The preset condition is that the frequency domain feature value E tends to a stable peak value.

[0080] Specifically, after system startup, it first enters global scanning mode, performing a global scan within a preset global bias voltage range. The photodetector collects optical signals from the electro-optic modulator point-by-point under different bias voltages. The preset global bias voltage range covers the rated drive voltage range of the electro-optic modulator. The control unit (Processor) synchronously calculates the initialization completion rate. and real-time drift rate .

[0081] Among them, the initialization completion degree It is used to quantify the coverage completeness and fitting accuracy of the global scan on the transmission response curve of the electro-optic modulator (EOM), and serves as a basic criterion for switching to local scan.

[0082] Specifically, initialization completion rate The calculation formula is:

[0083] (1.1)

[0084] (1.2)

[0085] in, , These are the weighting coefficients. Indicates the number of valid sampling points. This indicates the preset theoretical number of sampling points; This indicates the goodness of fit of the curve obtained by fitting the response curve of the global scan. This represents the preset goodness-of-fit threshold. Valid sampling points are defined as sampling points where the signal-to-noise ratio is greater than or equal to the preset threshold.

[0086] Furthermore, real-time drift rate It is used to capture the dynamic shift of the working point caused by environmental disturbances and changes in fiber optic sensing links, and serves as a dynamic adjustment indicator for mode switching, which can prevent the working point from losing lock due to drift during local scanning.

[0087] Specifically, real-time drift rate The calculation method is as follows: continuously collect the operating point bias voltage for Q sampling periods, calculate the voltage offset per unit time through linear regression, and then calculate the voltage offset based on the real-time drift rate. The calculation formula is obtained.

[0088] Among them, real-time drift rate The calculation formula is: (1.3)

[0089] in, Let Q be the maximum offset of the operating point bias voltage within each of the Q cycles. This represents the corresponding time interval.

[0090] In one implementation, the mode switching threshold from global scan to local scan is the initialization completion rate. Greater than or equal to the initialization completion threshold .in, This is the preset initialization completion threshold.

[0091] In one implementation, the mode switching threshold condition from global scan to local scan is when the real-time drift rate... Less than or equal to the preset drift rate threshold .in, This is a preset drift rate threshold.

[0092] In one implementation, the mode switching threshold from global scan to local scan is the initialization completion rate. Greater than or equal to the initialization completion threshold and real-time drift rate Less than or equal to the preset drift rate threshold .

[0093] In some embodiments of the control method, the mode switching threshold condition from global scan to local scan is: The control unit (processor) makes real-time judgments: when the conditions are met... Once the global scan is deemed complete and the electro-optic modulator (EOM) operating point has stabilized, a switching command is triggered, and the system smoothly switches from global scan mode to local scan mode, achieving seamless transition between the two modes. The processor simultaneously records the initial minimum point of the transmission response curve fitted by the current global scan, which serves as the initial range center for the local scan.

[0094] In some embodiments of the control method, the mode switching threshold condition from global scan to local scan is: The control unit (processor) makes real-time judgments: when the conditions are met... Once the global scan is deemed complete and the electro-optic modulator (EOM) operating point has stabilized, a switching command is triggered, and the system smoothly switches from global scan mode to local scan mode, achieving seamless transition between the two modes. The processor simultaneously records the initial minimum point of the transmission response curve fitted by the current global scan, which serves as the initial range center for the local scan.

[0095] In some embodiments of the control method, the mode switching threshold condition from global scan to local scan is: and The control unit (processor) makes real-time judgments: when the conditions are met... ,and Once the global scan is completed and the operating point of the electro-optic modulator (EOM) has stabilized, a switching command is triggered, and the system smoothly switches from the global scan mode to the local scan mode, achieving a seamless transition between the global and local scan modes. At the same time, the initial minimum point of the transmission response curve fitted by the current global scan is recorded as the initial range center of the local scan.

[0096] When the system switches to partial scan mode, the processor continuously monitors the real-time drift rate during the partial scan. When detected This indicates that increased environmental disturbances caused a sudden change in the system. The control unit (processor) immediately controls the electro-optic modulator to switch from local scanning mode back to global scanning mode, re-covering and initializing the transmission response curve to avoid operating point control failure; if it continues to maintain... The processor continuously maintains a local scanning mode to prepare for further and more precise locking of the working point (Null).

[0097] This application addresses the shortcomings of traditional power threshold methods, which are susceptible to environmental noise and circuit interference, leading to misjudgment of the operating point and inability to accurately pinpoint the absolute minimum point of the transmission response curve. In local scanning mode, using the frequency domain characteristic value E as the core discrimination criterion, and by analyzing the frequency domain energy distribution law of the optical signal, it can achieve a dual improvement in anti-interference capability and judgment accuracy.

[0098] To address the shortcomings of traditional power threshold methods, such as weak anti-interference capability and insufficient judgment accuracy, this invention constructs a discrimination index with frequency domain characteristic value E as the core based on the provided formula for calculating the spectral characteristic value E. Combined with the characteristics of the output optical signal of the electro-optic modulator (EOM) of the fiber optic sensing system, by analyzing the coupling relationship between the fundamental frequency, the second harmonic, and the total energy, it accurately filters out environmental random noise, circuit power frequency interference (50Hz), and mechanical vibration interference, thereby achieving quantitative determination of the operating point.

[0099] In one feasible embodiment, the specific steps of the local scanning mode include:

[0100] Local scanning is performed within a preset local bias voltage range to acquire optical signals from the electro-optic modulator at different bias voltages point by point. The global bias voltage range covers the rated drive voltage range of the electro-optic modulator.

[0101] In one feasible embodiment, the steps of the local scanning mode include:

[0102] A local scan is performed within a preset local bias voltage range to collect optical signals from the electro-optic modulator under different bias voltages. Based on the optical signal corresponding to each bias voltage point, the frequency domain characteristic value E corresponding to each bias voltage point is calculated.

[0103] Furthermore, the frequency domain eigenvalue E is calculated as follows:

[0104] S11. Preprocess the discrete sampling sequence x[n] of the optical signal acquired by local scanning.

[0105] S12. Calculate the total energy characterization parameters. Fundamental frequency energy characterization parameters and second harmonic energy characterization parameters .

[0106] S13, According to the formula The normalized frequency domain eigenvalue E is calculated.

[0107] Specifically, x[n] is the discrete sampling sequence of the optical signal acquired by local scanning. N is the preset theoretical number of sampling points, where This discrete sampling sequence of optical signals is adapted to the frequency domain resolution requirements of Fast Fourier Transform (FFT).

[0108] Specifically, the formula for calculating the spectral eigenvalue E and its physical meaning are as follows:

[0109] Specifically, total energy characterization parameters The calculation formula is:

[0110] (1.4)

[0111] in, The total energy characterization parameter is calculated based on the acquired optical signal sequence, reflecting the sampled signal. The overall energy level includes the total contribution of the effective signal, noise, and interference. The above total energy characterization parameters... In the calculation formula (1.4), the summation of the two terms corresponds to the sum of squares of energy at a single sampling point and the energy coupling term across sampling points, respectively, and together they represent the cumulative effect of the signal's time-domain energy.

[0112] Specifically, fundamental frequency energy characterization parameters The calculation formula is:

[0113] (1.5)

[0114] These are the fundamental frequency energy characterization parameters of the optical signal sequence, reflecting the energy distribution of the effective modulated signal. In the calculation formula (1.5), two items screen the fundamental frequency components, highlight the effective signal contribution through energy weighting, and suppress non-fundamental frequency interference.

[0115] Specifically, second harmonic energy characterization parameters The calculation formula is:

[0116] (1.6)

[0117] The second harmonic energy is a parameter that characterizes the optical signal sequence. It mainly reflects the effects of signal distortion, noise, and link interference. The higher the proportion of second harmonic energy, the more severe the interference to the signal. It can be used as an auxiliary indicator for interference determination.

[0118] In calculation , , Then, by using the coupling ratio of fundamental energy to total energy and second harmonic energy, the purity and frequency domain concentration of the effective signal are quantified, and the following is calculated based on the formula for calculating the frequency domain eigenvalue E:

[0119] (1.7)

[0120] (1.8)

[0121] in, The normalization coefficient is used to eliminate the influence of the weighting coefficient on the frequency domain eigenvalue E, so that the frequency domain eigenvalue E only reflects the frequency domain distribution characteristics of the signal. To preset the theoretical number of sampling points, , , This refers to the energy weighting coefficient; the energy weighting coefficient can be dynamically adjusted according to the sensing accuracy of the fiber optic sensing system, and this embodiment does not impose such a limitation. It should be noted that both global scanning and local scanning require sampling. The number of sampling points can be the same or different in both scanning modes.

[0122] Combining the above formulas (1.4)-(1.8), when the operating point of the electro-optic modulator (EOM) approaches the absolute minimum point of the transmission response curve, the effective signal energy is concentrated in the fundamental wave, the second harmonic and interference noise energy are suppressed, and the frequency domain characteristic value E tends to a stable peak value; conversely, when the interference is enhanced or the operating point is shifted, the frequency domain characteristic value E drops significantly and fluctuates violently.

[0123] As an example, the steps for extracting the frequency domain eigenvalue E include:

[0124] S21. The control unit (Processor) preprocesses the optical signal x[n] acquired by the local scan, and fills the Fourier transform (FFT) length with the mean value.

[0125] S22. Calculate sequentially according to the above formulas (1.4-1.6). , and Substituting into formulas (1.7) to (1.8), we obtain the normalized frequency domain eigenvalues ​​E.

[0126] S23. Collect frequency domain characteristic values ​​E for three consecutive sampling periods, calculate the mean and fluctuation amplitude, and use them as the basis for subsequent judgment.

[0127] Furthermore, considering the characteristics of the output optical signal from the electro-optic modulator (EOM) in the fiber optic sensing system, after the processor initiates a local scan, it calculates three types of core frequency domain characteristic values ​​based on the optical signal acquired during the local scan to effectively filter out random noise and fixed-frequency interference. These three types of core frequency domain characteristic values ​​include the energy percentage of the characteristic frequency. Frequency domain entropy H and interference frequency suppression ratio K.

[0128] Specifically, the proportion of characteristic frequency energy The calculation method is as follows:

[0129] The control unit performs a Fourier transform (FFT) on the optical signal acquired by partial scanning to obtain a frequency domain spectrum and calculates the characteristic frequencies. Corresponding peak spectral energy Total energy of the entire frequency band The ratio of the characteristic frequency energy proportions is obtained. Characteristic frequency energy percentage The calculation formula is: (2.1)

[0130] in, The total energy of the entire frequency band. Characteristic frequency The corresponding peak energy of the spectrum.

[0131] Specifically, the absolute minimum point of the transmission response curve of the electro-optic modulator (EOM) corresponds to the minimum value of the optical signal energy, and this energy value is at the characteristic frequency. (The frequency is consistent with the EOM drive signal frequency of the electro-optic modulator, set to...) The distribution at point () is unique. A Fourier transform (FFT) is performed on the optical signal acquired by local scanning to obtain the frequency domain spectrum, and the characteristic frequencies are calculated. Calculate the peak energy of the spectrum Total energy of the entire frequency band The ratio, i.e. When the operating point approaches the absolute minimum point, It tends to reach a stable minimum value.

[0132] Among them, frequency domain entropy Used to quantify the uniformity of frequency domain energy distribution, interference signals cause frequency domain energy dispersion and increase frequency domain entropy; while at the absolute minimum point, the optical signal energy distribution is concentrated and the frequency domain entropy is the lowest.

[0133] Among them, frequency domain entropy The calculation method is as follows: The control unit (Processor) divides the frequency domain spectrum after the Fast Fourier Transform (FFT) transformation into... Calculate the energy percentage for each frequency range. The frequency domain entropy is obtained according to the calculation formula. .

[0134] Specifically, frequency domain entropy The calculation formula is: ; (2.2)

[0135] Optionally, a frequency domain entropy threshold can be set. ,when Furthermore, if there is no significant fluctuation for several consecutive sampling cycles, the electro-optic modulator (EOM) is determined to be approaching its operating point.

[0136] The interference frequency suppression ratio K is calculated as follows: For fixed-frequency interference, the control unit (Processor) calculates the characteristic frequency. peak energy With interference frequency peak energy The ratio, i.e. The control unit (Processor) determines: when At that point, it is determined that the interference has been effectively filtered out and the collected data is reliable.

[0137] In some embodiments of this application, after initiating a local scan, the bias voltage corresponding to the initial lowest point of the response curve obtained from the global scan fitting is used as the initial range center of the local scan, and a narrow range scan interval is set, using frequency domain feature values. This serves as the core criterion for accurate determination, enabling precise positioning of the operating point. The preset condition for the frequency domain eigenvalue E is the frequency domain eigenvalue... The steps to determine if the frequency domain eigenvalue E meets the preset conditions include: (The value tends to stabilize at a peak value.)

[0138] S31. The control unit (Processor) calculates the frequency domain characteristic value E in the current local scan mode.

[0139] Specifically, after the local scan is initiated, the control unit (Processor) collects optical signals point by point within a preset local bias voltage range (narrow interval). The control unit (processor) synchronously extracts frequency domain feature values ​​for each sampling point. At the same time, a peak threshold for the frequency domain eigenvalue E is set. .in, This is the stable value of the frequency domain eigenvalue E corresponding to the absolute minimum point.

[0140] S32. If the control unit (Processor) determines that the frequency domain characteristic value E is greater than or equal to the peak threshold... If Y% is greater than or equal to q, and the fluctuation amplitude of the frequency domain feature value E within q consecutive sampling periods is less than a preset fluctuation threshold, then the frequency domain feature value E is determined to meet the preset condition. The bias voltage corresponding to the current local scanning mode is then determined as a candidate point, and the operating point of the electro-optic modulator is determined based on the candidate point.

[0141] in, , q is an integer.

[0142] For example, Y=90, i.e. 90%, q=3, and the preset fluctuation threshold of the fluctuation amplitude of the frequency domain feature value E is 2%.

[0143] Specifically, the control unit (Processor) determines that when E ≥ 90%E and the fluctuation amplitude of the frequency domain characteristic value E over three consecutive sampling periods is ≤ 2%, the current bias voltage value is recorded as a candidate point. In some embodiments, the fluctuation amplitude of the frequency domain characteristic value E is ≤ 2%, satisfying a preset condition. In this case, the bias voltage corresponding to the candidate point is determined as the operating point of the electro-optic modulator, thus completing the electro-optic modulator operating point locking.

[0144] S33. If the frequency domain characteristic value E of the control unit (processor) is less than the peak threshold... If Y%, then the local scanning direction is adjusted according to the trend of frequency domain characteristic value E changing with voltage until the frequency domain characteristic value E meets the preset condition. Then, the bias voltage corresponding to the current local scanning mode is determined as the candidate point, and the electro-optic modulator operating point is determined according to the candidate point.

[0145] Specifically, the processor determines that if E < 90%E, it indicates a large fluctuation in the bias voltage at that moment. The processor adjusts the local scanning direction based on the direction of change of the frequency domain characteristic value E. For example, when the frequency domain characteristic value E increases with the increase of the bias voltage, the processor scans in the direction of decreasing bias voltage; when the frequency domain characteristic value E decreases with the increase of voltage, the processor scans in the direction of increasing voltage, until the frequency domain characteristic value E approaches the lowest voltage range, thus completing the locking of the electro-optic modulator's operating point.

[0146] In some embodiments, determining the frequency domain eigenvalue E alone is insufficient to accurately pinpoint the operating point of the electro-optic modulator. Therefore, based on steps S31-S33, the control unit (Processor) further constructs a multi-eigenvalue joint determination rule structure, using the frequency domain eigenvalue... Using this as the core criterion, and combining interference verification and secondary screening steps, the operating point is accurately located and dynamically corrected. Specifically, the preset condition for the frequency domain eigenvalue E is that the frequency domain eigenvalue E tends to a stable peak value; the steps for determining whether the frequency domain eigenvalue E meets the preset condition include:

[0147] S41. The control unit (Processor) calculates the frequency domain characteristic value E in the current local scan mode.

[0148] Specifically, after the local scan is initiated, the control unit (Processor) collects optical signals point by point within a preset local bias voltage range (narrow interval). The control unit (processor) synchronously extracts the frequency domain feature value E for each sampling point, and simultaneously sets the peak threshold of the frequency domain feature value E. .in, This is the stable value of the frequency domain eigenvalue E corresponding to the absolute minimum point.

[0149] S42. If the control unit (Processor) determines that the frequency domain characteristic value E is greater than or equal to the peak threshold... If Y% of the frequency domain feature value E is less than a preset fluctuation threshold within q consecutive sampling periods, then the frequency domain feature value E is determined to meet the preset conditions. The bias voltage corresponding to the current local scanning mode is then identified as a candidate point, and further interference verification is performed. Where 0 < Y ≤ 100, 0 < q ≤ 20.

[0150] For example, Y=90, i.e. 90%, q=3, and the preset fluctuation threshold of the fluctuation amplitude of the frequency domain feature value E is 2%.

[0151] Specifically, the control unit (Processor) determines that when E≥90%E and the fluctuation amplitude of the frequency domain characteristic value E over three consecutive sampling periods is ≤2%, the current bias voltage value is recorded as a candidate point.

[0152] S43. If the frequency domain characteristic value E of the control unit (processor) is less than the peak threshold... If Y%, then the local scanning direction is adjusted according to the trend of frequency domain characteristic value E changing with voltage until the frequency domain characteristic value E meets the preset conditions. Then, the bias voltage corresponding to the current local scanning mode is determined as the candidate point, and further interference verification is performed.

[0153] Specifically, the processor determines that if E < 90%E, it indicates a large fluctuation in the bias voltage at that moment. The processor adjusts the local scanning direction based on the direction of change of the frequency domain characteristic value E. For example, when the frequency domain characteristic value E increases with the increase of the bias voltage, the processor scans in the direction of decreasing bias voltage; when the frequency domain characteristic value E decreases with the increase of voltage, the processor scans in the direction of increasing voltage, until the frequency domain characteristic value E approaches the lowest voltage range. Then, the bias voltage corresponding to the current local scanning mode is determined as a candidate point, and further interference verification is performed.

[0154] in, The proportion of characteristic frequency energy. The minimum characteristic frequency energy percentage is preset. H is the frequency domain entropy. The preset minimum entropy threshold is denoted as , and the interference frequency suppression ratio is denoted as . The preset suppression ratio threshold is used. This interference verification and secondary screening step includes:

[0155] S44. Calculate the characteristic frequency energy ratio of the optical signal. Frequency domain entropy H and interference frequency suppression ratio K.

[0156] S45. If the control unit (Processor) determines that the following conditions are met simultaneously: , , At that time, determine the proportion of characteristic frequency energy. The frequency domain entropy H and the interference frequency suppression ratio K satisfy the secondary screening conditions, and the current bias voltage is recorded as the candidate point obtained after secondary screening. The operating point of the electro-optic modulator is determined based on the candidate point.

[0157] S45. If the control unit (Processor) determines... , , If any one of the conditions is not met, based on frequency domain entropy Adjust the scanning direction according to the direction of change until the energy percentage of the characteristic frequency is determined. The frequency domain entropy H and the interference frequency suppression ratio K satisfy the secondary screening conditions, and the current bias voltage is recorded as the candidate point obtained after secondary screening. The operating point of the electro-optic modulator is determined based on the candidate point.

[0158] For example, in step S42 above, if the control unit (Processor) determines that the frequency domain characteristic value E is greater than or equal to the peak threshold... Based on the condition that Y% is less than the fluctuation amplitude of the frequency domain characteristic value E within q consecutive sampling periods, the control unit (Processor) simultaneously determines that the following conditions are met: H and K satisfy the secondary screening criteria, that is, they satisfy... , , At any time, record the current bias voltage value as a candidate point.

[0159] like If any one of H and K does not satisfy the secondary screening condition, then based on the frequency domain entropy... The direction of change adjusts the local scanning direction. For example, when the frequency domain entropy... As the bias voltage increases, the frequency domain entropy is scanned in the direction of increasing bias voltage. When the bias voltage decreases, the scan proceeds in the direction of decreasing bias voltage.

[0160] Optionally, determining the operating point of the electro-optic modulator based on candidate points includes:

[0161] S46. The control unit (Processor) continuously monitors the frequency domain characteristic values ​​of the verified candidate points. Compared with interference suppression ratio .

[0162] S47. If the fluctuation range of the frequency domain eigenvalue E exceeds Z% or If this is the case, a local scan mode is activated to correct the operating point voltage and compensate for minor drifts caused by environmental disturbances. Where 0 < Z.

[0163] S48. If the frequency domain eigenvalue Compared with interference frequency rejection ratio If the value remains within the threshold range, the corresponding candidate point is determined to be the stable operating point of the electro-optic modulator.

[0164] For example, Z=3. In steps S46-S48, the control unit (Processor) continuously monitors the frequency domain characteristic values ​​of the verified candidate points. Compared with interference suppression ratio When judging if the frequency domain eigenvalue The fluctuation range exceeds 3% or Immediately initiate local scan mode to quickly correct the bias voltage of the operating point and compensate for minor drifts caused by environmental disturbances; when judging frequency domain eigenvalues Compared with interference suppression ratio If the value remains within the threshold range for an extended period, the corresponding candidate point is determined to be the stable operating point of the electro-optic modulator.

[0165] Thus, this application achieves timely switching back to global scanning mode during the disturbance phase through interference verification and secondary screening, enabling accurate and stable locking of the operating point of the electro-optic modulator, thereby balancing efficiency and stability. This application, combined with a multi-feature value joint determination rule, further reduces the false positive rate of absolute minimum points, making it particularly suitable for fiber optic sensing systems in highly interference scenarios such as underground and outdoor environments.

[0166] Based on the above embodiments, the method for calculating the frequency domain feature value E provided in this application can also be applied to the global scanning working point search. Specifically, in the global scan, the initialization completion degree is calculated. and initialization completion Combining the above formulas (1.4)-(1.8), the corresponding frequency domain feature value E of the global scan is calculated synchronously. Specifically, the calculation method for the corresponding frequency domain feature value E of the global scan is as follows:

[0167] S51. Preprocess the discrete sampling sequence x[n] of all scanned optical signals.

[0168] S52. Calculate the total energy characterization parameters of the global scan. Fundamental frequency energy characterization parameters and second harmonic energy characterization parameters .

[0169] S53. The normalized frequency domain eigenvalue E is calculated according to the formula E = W1 / (W0·W2).

[0170] Specifically, let x[n] be the discrete sampling sequence of the optical signal acquired by global scanning. N is the preset theoretical number of sampling points, where This optical signal discrete sampling sequence is adapted to the frequency domain resolution requirements of Fast Fourier Transform (FFT); , , The energy weighting coefficient can be dynamically adjusted according to the sensing accuracy of the fiber optic sensing system, but this application does not impose any limitations on it.

[0171] According to formulas (1.4) to (1.6), the final frequency domain eigenvalue E is obtained as follows:

[0172] (1.7)

[0173] (1.8)

[0174] in, The normalization coefficient is used to eliminate the influence of the weighting coefficient on the frequency domain eigenvalue E, so that the frequency domain eigenvalue E only reflects the frequency domain distribution characteristics of the signal. To preset the theoretical number of sampling points, , , This is the energy weighting coefficient.

[0175] Combining the above formulas (1.4)-(1.8), when the operating point of the electro-optic modulator (EOM) approaches the absolute minimum point of the transmission response curve, the effective signal energy is concentrated in the fundamental wave, the second harmonic and interference noise energy are suppressed, and the frequency domain characteristic value E tends to a stable peak value; conversely, when the interference is enhanced or the operating point is shifted, the frequency domain characteristic value E drops significantly and fluctuates violently.

[0176] As an example, the steps for extracting the frequency domain eigenvalue E include:

[0177] 1) The control unit (Processor) preprocesses the optical signal x[n] acquired by global scanning, and fills the Fourier transform (FFT) length with the mean value.

[0178] 2) Calculate sequentially according to the above formulas (1.4-1.8). , and Substitute the values ​​into the equation to obtain the normalized frequency domain eigenvalues ​​E.

[0179] 3) Collect frequency domain feature values ​​E for three consecutive sampling periods, calculate the mean and fluctuation amplitude, and use them as the basis for subsequent judgment.

[0180] Furthermore, by combining the mode switching threshold conditions for global scanning to local scanning provided in the above embodiment with steps S32~S33 and S42~S43, it is jointly determined whether the switching conditions for global scanning to local scanning are met.

[0181] Specifically, when the control unit (Processor) determines:

[0182] Initialization completion rate and initialization completion When at least one of them satisfies the mode switching threshold condition, and the frequency domain eigenvalue E is greater than or equal to the peak threshold. When the frequency domain characteristic value E is less than a preset fluctuation threshold within q consecutive sampling periods, the global scan is considered complete, and the operating point of the electro-optic modulator (EOM) tends to stabilize. This triggers a switching command, and the system smoothly switches from global scan mode to local scan mode, achieving seamless transition between the two modes. The processor simultaneously records the initial minimum point of the transmission response curve fitted by the current global scan, serving as the initial range center for the local scan. This process ensures a smooth transition from global scan mode to local scan mode.

[0183] In summary, compared with the traditional approach of "fixed switching to local control after global scan is completed", this application adopts a dual-parameter switching algorithm of initialization completion degree and / or real-time drift rate, which can dynamically adapt to changes in operating conditions. It can quickly complete global optimization in the initialization stage, maintain precise local control in the stable stage, and promptly switch back to global scan in the disturbance stage, thus balancing efficiency and stability.

[0184] Compared with the traditional power threshold method, this method can effectively filter out random environmental noise and fixed frequency circuit interference through frequency domain eigenvalue analysis. It is especially suitable for strong interference scenarios such as underground and outdoor environments of fiber optic sensing systems, ensuring the stability of weak acoustic signal modulation.

[0185] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Features of various embodiments of the present invention can be partially or wholly coupled or combined with each other, and can cooperate and be technically driven in various ways. Various obvious changes, readjustments, combinations, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Many other equivalent embodiments may be included without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for controlling the operating point of an electro-optic modulator, characterized in that, include: During the system initialization phase, the electro-optic modulator is controlled to enter the global scanning mode to perform a global scan and collect the corresponding optical power response data. Calculate initialization completion rate and real-time drift rate ; When the initialization completion rate And / or the real-time drift rate When the mode switching threshold condition is met, the electro-optic modulator is controlled to switch from the global scanning mode to the local scanning mode. The local scanning mode uses the bias voltage corresponding to the initial minimum point of the response curve obtained by fitting the global scanning as the initial range center of the local scanning, collects the corresponding optical power response data, and calculates the frequency domain characteristic value E. In local scanning mode, the frequency domain feature value E is used as the discrimination criterion. When the frequency domain feature value E meets the preset conditions, the bias voltage corresponding to the frequency domain feature value E is locked as the operating point of the electro-optic modulator. The frequency domain eigenvalue E is calculated as follows: Preprocess the discrete sampling sequence x[n] of the optical signal acquired by local scanning; Calculate the total energy characterization parameters Fundamental frequency energy characterization parameters and second harmonic energy characterization parameters ; According to the formula The normalized frequency domain eigenvalues ​​E are calculated; where, ； ； ； ； ； in, These are the normalization coefficients; The preset theoretical number of sampling points; , , Energy weighting coefficient; The preset condition is the frequency domain feature value. The frequency domain characteristic value tends to stabilize at a peak value; determine the frequency domain characteristic value. The steps to meet the preset conditions include: Calculate the frequency domain eigenvalues ​​in the current local scanning mode. ; If frequency domain eigenvalues Greater than or equal to the peak threshold If Y%, and the fluctuation amplitude of the frequency domain feature value E within q consecutive sampling periods is less than the preset fluctuation threshold, then it is determined that the frequency domain feature value E meets the preset condition, the bias voltage corresponding to the current local scanning mode is determined as a candidate point, and further interference verification is performed, or the electro-optic modulator operating point is determined based on the candidate point. If the frequency domain eigenvalue E is less than the peak threshold If Y%, then the local scanning direction is adjusted according to the trend of frequency domain characteristic value E changing with voltage until the frequency domain characteristic value E meets the preset condition. Then, the bias voltage corresponding to the current local scanning mode is used as the candidate point, and further interference verification is performed. , ; The interference verification steps include: Calculate the characteristic frequency energy ratio of the optical signal acquired by partial scanning. Frequency domain entropy H and interference frequency rejection ratio ; When both conditions are met , , At that time, determine the proportion of characteristic frequency energy. Frequency domain entropy H and interference frequency rejection ratio All three conditions must be met for secondary screening. The current bias voltage is recorded as the candidate point obtained after secondary screening. The operating point of the electro-optic modulator is determined based on the candidate point. like , , If any one of the conditions is not met, based on frequency domain entropy Adjust the scanning direction according to the direction of change, and continue scanning until the energy percentage of the characteristic frequency is determined. Frequency domain entropy H and interference frequency rejection ratio All three conditions must be met for the secondary screening. The current bias voltage is recorded as the candidate point obtained after the secondary screening. The operating point of the electro-optic modulator is determined based on the candidate point. in, The minimum characteristic frequency energy percentage is preset. The preset minimum entropy threshold, This is the preset suppression ratio threshold.

2. The method according to claim 1, characterized in that, The mode switching threshold condition is the initialization completion rate. Greater than or equal to the initialization completion threshold , and / or, when the real-time drift rate Less than or equal to the preset drift rate threshold ; And / or, The method for controlling the operating point of the electro-optic modulator further includes continuously monitoring the real-time drift rate during local scanning. When detected Then, the electro-optic modulator is controlled to switch from the local scanning mode to the global scanning mode; wherein, The preset drift rate threshold; And / or, The method for controlling the operating point of the electro-optic modulator further includes continuously monitoring the real-time drift rate during local scanning. When detected Then, the electro-optic modulator is controlled to maintain a local scanning mode; wherein, This is a preset drift rate threshold.

3. The method according to claim 1, characterized in that, The initialization completion degree The calculation formula is: ； ； in, , These are the weighting coefficients. Indicates the number of valid sampling points. This indicates the preset theoretical number of sampling points; This indicates the goodness of fit of the curve obtained by fitting the response curve of the global scan. This represents the preset goodness-of-fit threshold; And / or, The real-time drift rate The calculation method is as follows: The operating point bias voltage is continuously acquired for Q sampling periods. The voltage offset per unit time is calculated through linear regression, based on the real-time drift rate. The calculation formula for obtaining the real-time drift rate Wherein, the real-time drift rate The calculation formula is: ； in, Let Q be the maximum offset of the operating point bias voltage within each of the Q cycles. This represents the corresponding time interval.

4. The method according to claim 1, characterized in that, The steps of the global scanning mode include performing a global scan within a preset global bias voltage range, and acquiring the optical signals of the electro-optic modulator at different bias voltages point by point; wherein, the global bias voltage range covers the rated driving voltage range of the electro-optic modulator. And / or, The steps of the local scanning mode include performing a local scan within a preset local bias voltage range, acquiring optical signals of the electro-optic modulator under different bias voltages, and calculating the frequency domain characteristic value E corresponding to each bias voltage point based on the optical signal corresponding to each acquired bias voltage point.

5. The method according to claim 1, characterized in that, The step of determining the operating point of the electro-optic modulator based on candidate points includes: For the candidate points that pass the verification, the frequency domain eigenvalues ​​are continuously monitored. Compared with interference suppression ratio ; If frequency domain eigenvalues The fluctuation range exceeds Z% or Then, a local scan mode is activated to correct the bias voltage of the operating point and compensate for minor drifts caused by environmental disturbances. ; If frequency domain eigenvalues Compared with interference frequency rejection ratio If the value remains within the threshold range, the corresponding candidate point is determined to be the stable operating point of the electro-optic modulator.

6. The method according to claim 1, characterized in that, The characteristic frequency energy ratio The calculation method involves performing a Fourier transform on the optical signal acquired through local scanning to obtain a frequency domain spectrum, and then calculating the characteristic frequencies. Calculate the corresponding peak spectral energy Total energy of the entire frequency band The ratio of the characteristic frequency energy proportions is obtained. ,in, ; And / or, The frequency domain entropy The calculation method involves dividing the frequency domain spectrum after Fourier transform into... Calculate the energy percentage for each frequency range. According to frequency domain entropy The calculation formula is obtained, where, , ; And / or, The interference frequency suppression ratio The calculation method is to calculate the characteristic frequency for fixed-frequency interference. peak energy With interference frequency peak energy The ratio of the two values ​​is the interference frequency suppression ratio. ,in, .

7. A fiber optic sensing system, characterized in that, It includes a photodetector, a transimpedance amplifier and signal amplification integrated module, an analog-to-digital converter, a control unit, and an electro-optic modulator; The control unit is used to store and execute the control method of the electro-optic modulator operating point according to any one of claims 1-6 to obtain the bias voltage corresponding to the electro-optic modulator operating point, and lock it at the operating point.

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