Dynamic wavelength non-parametric point-by-point calibration method based on multi-scale characteristics of interference signals

Abstract

The application provides a dynamic wavelength non-parametric point-by-point calibration method based on multi-scale characteristics of an interference signal, which comprises the following steps: driving a laser by using a simple tuning mode, collecting an interference signal, and generating a standard interference graph by processing the interference signal; collecting an interference signal under a complex tuning condition; extracting a discrete time-frequency relationship and positioning a key node; performing standardization processing on local interference intensity; inversely processing the local normalized continuous time-frequency relationship based on the standard interference graph; and finally, performing multi-scale data superposition and physical frequency restoration to complete dynamic wavelength calibration. The application has reasonable concept, can break away from the dependence on a preset function, realize high-precision dynamic wavelength calibration under a complex modulation and a non-ideal tuning scene, improve the universality and anti-interference ability of the method, and is suitable for high-precision wavelength measurement under the complex modulation and the non-ideal tuning scene.

Description

Technical Field

[0001] This invention relates to the field of spectral measurement technology, specifically to a dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals. Background Technology

[0002] Tunable semiconductor laser absorption spectroscopy (TDLAS) technology, with its advantages of real-time online operation, non-invasiveness, and high sensitivity, has become a core diagnostic technology for scenarios such as combustion diagnostics, hypersonic flow field detection, and environmental monitoring. Accurate measurement of the laser's dynamic wavelength (time-dependent frequency response) is a crucial prerequisite for ensuring the accuracy of mixed spectral analysis and expanding the application boundaries of the technology. Only by establishing a precise time-frequency correlation between wavelength and time can the interference of wavelength drift and modulation distortion on the detection results be effectively eliminated, meeting the high-precision measurement requirements in complex scenarios.

[0003] In the field of TDLAS dynamic wavelength calibration, although related technologies and patents have been explored, significant limitations remain, making it difficult to adapt to complex modulation and non-ideal tuning scenarios. For example, CN201811058473.1 uses a combination of a fiber FP interferometer and a Michelson fiber interferometer, which solves the problem of static calibration deviating from dynamic measurements, but the hardware is complex and does not address the time-frequency deviation caused by the nonlinear response of the laser under complex modulation. CN201911270678.0 clarifies the influence of laser linewidth on gas absorption spectral lines through theory and simulation. While some methods have been proposed, they haven't addressed the optimization of dynamic wavelength calibration methods, thus failing to support the tracing of time-frequency relationships. CN201310140099.0 simplifies the mirror parallelism requirement by using a rotating FP interferometer to achieve static wavelength measurement, but it cannot capture continuous changes in dynamic wavelengths and relies on manual interpretation of peak angles. CN201510836754.5 proposes a calibration-free method based on the WMRF model, which eliminates light intensity fluctuations through harmonic amplitude ratios, but it fails to overcome the bottleneck in complex modulation scenarios due to the limited adaptability of the parameterized model and the increased cost of using etalons. Traditional dynamic wavelength calibration often relies on extracting discrete time-frequency relationships using an FP interferometer and then obtaining continuous time-frequency relationships through nonlinear fitting of a preset function. This type of parameterized method can meet the requirements in simple tuning scenarios, but in complex tuning, the nonlinear response of the laser can lead to significant deviations between the actual time-frequency relationship and the preset model. Furthermore, it often relies on high-cost etalons and prior knowledge, easily generating systematic biases, which severely restricts the application expansion of TDLAS technology in complex and high-precision measurement scenarios.

[0004] The core requirement of Tunable Semiconductor Laser Absorption Spectroscopy (TDLAS) technology is to establish a precise time-frequency relationship between laser wavelength and time. Although existing dynamic wavelength calibration patents have made some progress, they still have significant limitations: some methods rely on matching feature points of a single absorption peak to construct a time-frequency conversion model, which has limited adaptability and is difficult to cope with complex tuning scenarios; some methods improve stability through initial wavelength calibration and locking techniques, but have not solved the problem of high-precision traceability of time-frequency relationships under dynamic scanning; there are also dynamic calibration schemes based on FP interferometers and Michelson interferometers, which can correct dynamic and static calibration deviations, but have not overcome the bottleneck of adapting parametric models to complex modulations.

[0005] In conclusion, it is necessary to further innovate existing technologies. Summary of the Invention

[0006] To address the technical problems of the aforementioned parametric dynamic wavelength calibration methods, such as reliance on preset models, poor environmental adaptability, and limited applicability, this invention proposes a dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals. This method is rationally conceived, frees itself from dependence on preset functions, and achieves high-precision dynamic wavelength calibration in complex modulation and non-ideal tuning scenarios. It enhances the universality and anti-interference capability of the method, making it suitable for high-precision wavelength measurement in complex modulation and non-ideal tuning scenarios.

[0007] To address the aforementioned technical problems, this invention provides a dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals, which mainly includes the following steps:

[0008] (1) The laser is driven by a simple tuning mode, and the collected interference signals are processed to generate a standard interferogram;

[0009] (2) Acquire the transmitted light intensity signal output by the FP interferometer in complex tuning mode. With reference light intensity signal The reference interference intensity signal was calculated. ;

[0010] (3) The reference interference intensity signal obtained in step (2) Peak detection is performed to extract the times corresponding to all interference peaks. And locate the tuning inflection point; based on the interference peak moment and free spectral range Generate normalized discrete time-frequency relationship And it is extended to a step function;

[0011] (4) For the interference intensity signal segment in each interference cycle in step (3), first perform smoothing to eliminate random noise, and then perform range normalization on the smoothed signal according to the left and right monotonic intervals to obtain the standardized interference intensity. ;

[0012] (5) Standard interferogram generated in step (1) The normalized interference intensity within each interference cycle obtained in step (4) Inversion is performed to obtain the corresponding locally normalized continuous time-frequency relationship;

[0013] (6) The step function obtained in step (3) The locally normalized continuous time-frequency relationship obtained in step (5) By performing linear superposition, a normalized continuous time-frequency relationship is obtained. Then normalize the continuous time-frequency relationship. With free spectral range Multiplying them yields the continuous time-frequency relationship in the physical frequency domain. Complete dynamic wavelength calibration.

[0014] As a preferred embodiment of the present invention, step (1) specifically includes the following steps:

[0015] (1.1) The laser is driven by a simple tuning mode, the reference light intensity and the transmitted light intensity are collected synchronously, the reference interference intensity is calculated and the peak position is extracted to generate a normalized discrete time-frequency relationship. The specific process is as follows: (a) Based on the synchronously collected transmitted light intensity and reference light intensity According to the formula Calculate the reference interference intensity (b) on Perform peak detection to obtain the times corresponding to all interference peaks. (c) Based on free spectral range Generate normalized discrete time-frequency relationship Its definition is: ,in The physical frequency corresponding to the interference peak;

[0016] (1.2) The normalized discrete time-frequency relationship obtained in step (1.1) Perform cubic spline interpolation and construct the interpolation function. To obtain the normalized continuous time-frequency relationship: ,in The function is a piecewise cubic polynomial, satisfying the continuity of function values, first derivative, and second derivative; the original interference signal is... Timeline Replace with The interference signal with normalized frequency as the independent variable is obtained. ;

[0017] (1.3) Obtained from step (1.2) Extract data segments within each interference cycle, and normalize all data segments according to their local frequencies. Align and overlay the data, then average each point to obtain the average interferogram. Perform piecewise range normalization on the average interferogram to generate a standard interferogram. (L scale), Formula: ,in This is the normalized frequency corresponding to the minimum value of the average interferogram.

[0018] As a preferred embodiment of the present invention: the simple tuning mode in step (1.1) is a single-frequency sine sweep; the interpolation process in step (1.2) adopts the cubic spline interpolation method.

[0019] As a preferred embodiment of the present invention, step (2) is performed as follows: in the target complex tuning mode

[0020] Down-driving laser, synchronously acquiring transmitted light intensity and reference light intensity According to the formula Calculate the reference interference intensity signal ,Record It serves as a reference interference signal for subsequent time-frequency relationship calibration.

[0021] As a preferred embodiment of the present invention: the target complex tuning mode in step (2) is at least one of the following: a composite tuning mode of sinusoidal scanning and high-frequency sinusoidal modulation, a composite tuning mode of sinusoidal scanning signal and square wave modulation signal, a hybrid frequency modulation mode, and a strong nonlinear laser tuning mode.

[0022] As a preferred embodiment of the present invention, the specific process of step (3) of extracting discrete time-frequency relationships and locating key nodes is as follows:

[0023] The reference interference intensity signal obtained in step (2) Peak detection was performed, and the corresponding times of all interference peaks were extracted. and the location of the tuning inflection point;

[0024] The normalized discrete time-frequency relationship is recursively assigned according to the free spectral range and extended to a step function: Let the normalized frequency reference value of the first interference peak be... Then the first The normalized discrete time-frequency relationship corresponding to each interference peak is as follows: Within the time intervals between all interference peaks, the normalized time-frequency relationship is defined as the value of the previous peak, forming a step function:

[0025] ;

[0026] in, For the first The peak moment of each interference peak.

[0027] As a preferred embodiment of the present invention, the specific process of standardizing the local interference intensity in step (4) is as follows:

[0028] The signal segment within the target interference period is smoothed using a smooth spline fitting method to obtain the smoothed interference intensity. ;

[0029] Using the local normalized frequency relationship corresponding to this period ,Will Mapped to normalized frequency Smoothed interference intensity as the independent variable The normalized frequency corresponding to the minimum point of smooth interference intensity. The signal is divided into two monotonic intervals, left and right, by the boundary.

[0030] Perform range normalization within each monotonic interval, as shown in the following formula:

[0031] ;

[0032] in, The measured standardized interference intensity was used as the inversion input; The normalized frequency corresponding to the minimum value of the periodically smoothed signal is used to obtain the normalized interference intensity. .

[0033] As a preferred embodiment of the present invention, the specific process of step (5) is as follows: based on the standard interferogram generated in step (1) Establish standardized interference intensity With local normalized frequency The mapping relationship; for the normalized interference intensity obtained in step (4) Based on its value and the minimum value of the standard interferogram By comparison, it is determined that it belongs to the left monotonic interval. or right monotonic interval And select the corresponding mapping relationship for inversion; through interpolation or lookup table in the mapping relationship of the selected interval, Converted to local normalized frequency This yields a locally normalized continuous time-frequency relationship.

[0034] As a preferred embodiment of the present invention, the normalized continuous time-frequency relationship in step (6) is expressed as:

[0035] ;

[0036] The continuous time-frequency relationship in the physical frequency domain in step (6) is expressed as follows:

[0037] .

[0038] By adopting the above technical solution, the present invention has the following beneficial effects:

[0039] This invention presents a reasonable concept for a dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals. It is a high-precision dynamic wavelength calibration method that is free from dependence on preset models, adaptable to complex modulation and non-ideal tuning scenarios, reduces system hardware costs, and improves the universality and anti-interference capability of the method. It is a key requirement for promoting the extension of TDLAS technology to more complex application scenarios and is of great significance for ensuring the accuracy of mixed spectrum analysis and expanding the application boundaries of TDLAS technology.

[0040] This invention integrates "P-scale" (unit-scale discrete calibration) and "L-scale" (local-scale continuous mapping), eliminating the dependence on preset function models and effectively solving the wavelength calibration problem in complex modulation / non-ideal tuning scenarios. It is applicable to various complex modulation modes such as square wave modulation and hybrid frequency modulation.

[0041] Experimental verification shows that the absolute frequency measurement uncertainty of this invention is significantly reduced, approaching the intrinsic linewidth limit of the DFB laser, and the random error is greatly reduced compared with traditional parameterization methods, resulting in a significant improvement in measurement accuracy. It achieves point-by-point calibration of the sub-free spectral range (FSR) accuracy, with an absolute frequency uncertainty of 0.00053 cm⁻¹. -1 (Approximately 15MHz), random error is reduced by about 2 / 3 compared to traditional parameterization methods.

[0042] Experimental verification shows that this invention is applicable to complex scenarios such as square wave, irregular wave, and mixed frequency wave modulation, providing a high-precision time-frequency reference for TDLAS mixed spectrum analysis, and can be widely used in fields such as combustion diagnostics and hypersonic flow field detection.

[0043] This invention eliminates the need for complex hardware such as high reflectivity and small FSR etalons, reducing system costs. At the same time, it can effectively capture dynamic fluctuations in laser frequency, has strong anti-interference capabilities, and the system deviation can be controlled within 3.1%, providing a high-precision time-frequency reference for the mixed spectrum analysis of TDLAS technology.

[0044] The operation process of the present invention is clear, and it can be adapted to different types of tunable lasers. It has been successfully used in the diagnosis of extreme dynamic environments such as shock tunnels and hypersonic combustion, and has broad application prospects in the fields of combustion diagnosis and hypersonic flow field detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0046] Figure 1 It is a schematic diagram of an F - P interferometer and a periodic change diagram of the interference intensity with the optical frequency;

[0047] Figure 1 (a) is a schematic structural diagram of an F - P interferometer, mainly including the F - P interferometer body and a detector. After the laser is incident on the F - P interferometer, multi - beam interference occurs, and the detector is used to receive the interference signal;

[0048] Figure 1 (b) is a periodic change curve of the interference intensity with the optical frequency when the incident angle i = 0, showing the periodic characteristics of the interference signal. The frequency interval between adjacent interference peaks is the free spectral range (FSR);

[0049] Figure 2 It is a comparison diagram of the multi - scale characteristics of the time - frequency relationship calibration method;

[0050] Figure 2 (a) shows the composition of the interference signal and prior knowledge, and the prior knowledge includes a scanning function, a modulation function, a transfer function, etc.;

[0051] Figure 2 (b) is the signal composition from a multi - scale perspective, including the interference line shape (L - scale) at the local scale (<FSR), the normalized discrete time - frequency relationship (P - scale) at the unit scale (=FSR), and the preset function at the global scale (>FSR);

[0052] Figure 2 (c) compares the linear superposition reconstruction method of the present invention with the non - linear fitting reconstruction method of the parametric method, highlighting the advantage that the present invention does not require a preset model.

[0053] Figure 3 It is a schematic diagram of the standard interferogram measurement method;

[0054] Figure 3(a) shows the interferometric measurement signal obtained under simple tuning conditions and its normalized discrete time-frequency relationship obtained by peak finding;

[0055] Figure 3 (b) is the normalized continuous time-frequency relation obtained by interpolating the normalized discrete time-frequency relation;

[0056] Figure 3 (c) is the measured interference signal (the time domain axis has been replaced with the relative frequency axis);

[0057] Figure 3 (d) is a superimposed display of the interferograms obtained in each cycle (only the first five cycles are shown here as an example);

[0058] Figure 3 (e) is the final standard interferogram (the red dashed line is the boundary between the two monotonic intervals).

[0059] Figure 4 Example graph showing the normalized time-frequency relationship measured point by point;

[0060] Figure 4 (a) shows the interference signal measured under complex tuning conditions and the normalized discrete time-frequency relationship obtained by peak finding;

[0061] Figure 4 (b) is the step function expanded from the normalized discrete time-frequency relation;

[0062] Figure 4 (c) Comparison of reference interference intensity (black) and standard interference intensity (red) (the red dashed line is the boundary between the two monotonic intervals);

[0063] Figure 4 (d) represents the locally normalized time-frequency relationship;

[0064] Figure 4 (e) represents the global normalized time-frequency relationship.

[0065] Figure 4 The complete implementation process of the dynamic wavelength nonparametric point-by-point calibration method of the present invention is clearly demonstrated, including constructing a standard interferogram through a simple tuning mode, acquiring and processing interference signals under complex tuning conditions, inverting the locally normalized continuous time-frequency relationship based on the standard interferogram, superimposing it with the step function extended from the discrete time-frequency relationship, and finally obtaining the continuous time-frequency relationship.

[0066] Figure 5 Here is a flowchart of the NPP method;

[0067] Figure 5The complete process of the method of the present invention is clearly demonstrated, including constructing a standard interferogram through simple tuning, acquiring and processing the interference signal under complex tuning, and obtaining the final dynamic wavelength calibration result by superimposing multi-scale data. Detailed Implementation

[0068] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] The present invention will be further explained below with reference to specific embodiments.

[0070] like Figure 1 As shown in the figure, this embodiment provides a dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals, which includes the following steps:

[0071] Step 100: Drive the laser using a simple tuning mode, collect interference signals, process them to generate a standard interferogram (i.e., "L scale"):

[0072] Step 101: Drive the laser using a simple tuning mode such as single-frequency sinusoidal scanning, synchronously acquire the reference light intensity and transmitted light intensity, calculate the reference interference intensity and extract the peak position, and generate a normalized discrete time-frequency relationship: based on the synchronously acquired transmitted light intensity... and reference light intensity According to the formula Calculate the reference interference intensity (b) on Perform peak detection to obtain the times corresponding to all interference peaks. (c) Based on free spectral range Generate normalized discrete time-frequency relationship Its definition is: ,in The value is the physical frequency corresponding to the interference peak.

[0073] Step 102: Apply the normalized discrete time-frequency relationship obtained in step S101. Perform cubic spline interpolation and construct the interpolation function. To obtain the normalized continuous time-frequency relationship: ,in The function is a piecewise cubic polynomial, satisfying the continuity of function values, first derivative, and second derivative; the original interference signal is... Timeline Replace with The interference signal with normalized frequency as the independent variable is obtained. .

[0074] Step 103, obtained from step S102 Extract data segments within each interference cycle, and normalize all data segments according to their local frequencies. Align and overlay the data, then average each point to obtain the average interferogram. Perform piecewise range normalization on the average interferogram to generate a standard interferogram. (L scale), Formula: ,in This is the normalized frequency corresponding to the minimum value of the average interferogram.

[0075] The simple tuning mode described in step S101 above is a single-frequency sine sweep.

[0076] The interpolation process in step S102 above uses the cubic spline interpolation method. Specific process...

[0077] Step 200: Acquire the transmitted light intensity signal output by the FP interferometer in the target complex tuning mode. With reference light intensity signal The reference interference intensity signal was calculated. The specific process is as follows: The laser is driven under at least one of the following complex tuning modes: composite tuning of sinusoidal scanning and high-frequency sinusoidal modulation, composite tuning mode of sinusoidal scanning signal and square wave modulation signal, hybrid frequency modulation mode, and strongly nonlinear laser tuning mode, while simultaneously acquiring the transmitted light intensity. and reference light intensity According to the formula Calculate the reference interference intensity ,Record It serves as a reference interference signal for subsequent time-frequency relationship calibration.

[0078] Step 300: Extract discrete time-frequency relationships and locate key nodes.

[0079] The reference interference intensity signal obtained in step S200 Peak detection was performed, and the corresponding times of all interference peaks were extracted. and the location of the tuning inflection point; recursively assign the normalized discrete time-frequency relationship according to the free spectral range interval and extend it to a step function: let the normalized frequency reference value of the first interference peak be . Then the first The normalized discrete time-frequency relationship corresponding to each interference peak is as follows: Within the time interval between all interference peaks, the normalized time-frequency relationship is defined as the value of the previous peak, forming a step function (i.e., the "P-scale"): ,in, For the first The peak moment of each interference peak.

[0080] Step 400: Standardize the local interference intensity.

[0081] The specific process for standardizing the local interference intensity is as follows: A smooth spline fitting method is used to smooth the signal segment within the target interference period to eliminate random noise and obtain the smoothed interference intensity. ; Utilizing the local normalized frequency relationship corresponding to this period ,Will Mapped to normalized frequency Smoothed interference intensity as the independent variable The normalized frequency corresponding to the minimum point of smooth interference intensity. Divide the signal into two monotonic intervals, left and right, using the boundary as the boundary; perform range normalization within each monotonic interval, as shown in the following formula: ,in The measured standardized interference intensity is used as the inversion input. The normalized frequency corresponding to the minimum value of the periodically smoothed signal is used to obtain the normalized interference intensity. .

[0082] Step 500: Locally Normalized Time-Frequency Relationship Inversion

[0083] The specific process of inverting the locally normalized continuous time-frequency relationship based on the standard interferogram is as follows: Based on the standard interferogram generated in step (1) Establish standardized interference intensity With local normalized frequency The mapping relationship; for the normalized interference intensity obtained in step (4) Based on its value and the minimum value of the standard interferogram By comparison, it is determined that it belongs to the left monotonic interval. or right monotonic interval And select the corresponding mapping relationship for inversion; through interpolation (such as piecewise linear interpolation) or lookup table in the mapping relationship of the selected interval, Converted to local normalized frequency This yields a locally normalized continuous time-frequency relationship.

[0084] Step 600: Multi-scale data overlay and physical frequency restoration

[0085] The step function obtained in step (3) (P-scale) and Locally Normalized Continuous Time-Frequency Relationship Linear superposition yields a normalized continuous time-frequency relationship. Normalize the continuous time-frequency relationship and Multiplying them restores the continuous time-frequency relationship in the physical frequency domain. Complete dynamic wavelength calibration.

[0086] The present invention will be further described below with reference to specific embodiments:

[0087] (I) Experimental System Setup

[0088] The experimental system uses a DFB tunable semiconductor laser (NLK1E5EAAA, NTT) with a center wavelength of 1391 nm. The laser output is split by optical fiber, and one path passes through a silicon-based FP interferometer (FSR=0.0172 cm⁻¹). -1 One beam (with a reflectivity R=0.3) passes through a gas cell filled with high-purity nitrogen, while the other beam serves as a reference beam. A quartz pillar is installed in the optical window, and the air in the optical path is replaced with high-purity nitrogen to suppress interference from ambient moisture. Reference signal With transmitted signal Data was simultaneously acquired by two photodiode detectors (PDA20CS2, Thorlabs) and recorded by a digital oscilloscope (SDS5000X, Siglent) with a sampling rate of 50 MHz. The oscilloscope clock was strictly synchronized with a 10 MHz reference clock.

[0089] (ii) Construction of standard interferogram (“L scale”)

[0090] Pump the gas tank to 10. -2 After Pa, pure nitrogen gas is introduced to eliminate residual absorption. A 50 Hz sinusoidal scanning signal is generated using a dual-channel function generator, and a DFB laser is driven by a laser controller (ITC4001, Thorlabs) for simple tuning. Reference and transmitted light intensities are simultaneously acquired, the reference interference intensity is calculated, and the peak position is extracted to generate a normalized discrete time-frequency relationship. A normalized continuous time-frequency relationship is obtained through cubic spline interpolation, replacing the time axis of the interference signal. Data segments from each period are truncated, aligned, and superimposed, and then normalized by averaging and range to generate a standard interferogram.

[0091] (III) Dynamic wavelength calibration under complex tuning conditions

[0092] A composite signal containing a 50 Hz sinusoidal scan and a 10 kHz high-frequency sinusoidal modulation is generated to drive a laser. Interference signals are simultaneously acquired, and reference interference intensity is calculated. Peak detection is performed on the interference signal to extract the interference peaks and tuning inflection point positions. Normalized discrete time-frequency relationships are assigned according to the FSR interval and expanded into step functions. The target interference periodic signal segment is selected, and after smoothing and normalization, the locally normalized continuous time-frequency relationship is inverted based on the standard interferogram. The step function and the locally normalized continuous time-frequency relationship are linearly superimposed, and then multiplied by the FSR to obtain the continuous time-frequency relationship, completing the calibration.

[0093] (iv) Verification of square wave modulation scenario

[0094] A laser was driven by a composite signal of 100 Hz sinusoidal scanning and 10 kHz square wave modulation. The gas cell was filled with an argon mixture containing 1% water vapor (total pressure 6 kPa), and the optical path was purged with high-purity nitrogen. The dynamic wavelength was calibrated using the method of this invention, harmonic components were extracted through continuous wavelet transform, and the 2f / 1f harmonics were normalized to eliminate the influence of light intensity fluctuations. The fitting residual amplitude was less than 5% of the signal intensity, verifying the applicability of the method in complex modulation scenarios.

[0095] This invention is well-conceived and can break free from dependence on preset functions, achieving high-precision dynamic wavelength calibration in complex modulation and non-ideal tuning scenarios. It improves the universality and anti-interference capability of the method and is suitable for high-precision wavelength measurement in complex modulation and non-ideal tuning scenarios.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interferometric signals, characterized in that, The main steps include: (1) The laser is driven by a simple tuning mode, and the collected interference signals are processed to generate a standard interferogram; (2) Acquire the transmitted light intensity signal output by the FP interferometer in complex tuning mode. With reference light intensity signal The reference interference intensity signal was calculated. ; (3) The reference interference intensity signal obtained in step (2) Peak detection is performed to extract the times corresponding to all interference peaks. And locate the tuning inflection point; based on the interference peak moment and free spectral range Generate normalized discrete time-frequency relationship And it is extended to a step function; (4) For the interference intensity signal segment in each interference cycle in step (3), first perform smoothing to eliminate random noise, and then perform range normalization on the smoothed signal according to the left and right monotonic intervals to obtain the standardized interference intensity. ; (5) Standard interferogram generated in step (1) The normalized interference intensity within each interference cycle obtained in step (4) Inversion is performed to obtain the corresponding locally normalized continuous time-frequency relationship; (6) The step function obtained in step (3) The locally normalized continuous time-frequency relationship obtained in step (5) By performing linear superposition, a normalized continuous time-frequency relationship is obtained. Then normalize the continuous time-frequency relationship. With free spectral range Multiplying them yields the continuous time-frequency relationship in the physical frequency domain. Complete dynamic wavelength calibration.

2. The dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals as described in claim 1, characterized in that, Step (1) specifically includes the following steps: (1.1) The laser is driven by a simple tuning mode, the reference light intensity and the transmitted light intensity are collected synchronously, the reference interference intensity is calculated and the peak position is extracted to generate a normalized discrete time-frequency relationship. The specific process is as follows: (a) Based on the synchronously collected transmitted light intensity and reference light intensity According to the formula Calculate the reference interference intensity (b) on Perform peak detection to obtain the times corresponding to all interference peaks. (c) Based on free spectral range Generate normalized discrete time-frequency relationship Its definition is: ,in The physical frequency corresponding to the interference peak; (1.2) The normalized discrete time-frequency relationship obtained in step (1.1) Perform cubic spline interpolation and construct the interpolation function. To obtain the normalized continuous time-frequency relationship: ,in The function is a piecewise cubic polynomial, satisfying the continuity of function values, first derivative, and second derivative; the original interference signal is... Timeline Replace with The interference signal with normalized frequency as the independent variable is obtained. ; (1.3) Obtained from step (1.2) Extract data segments within each interference cycle, and normalize all data segments according to their local frequencies. Align and overlay the data, then average each point to obtain the average interferogram. Perform piecewise range normalization on the average interferogram to generate a standard interferogram. ("L" scale), formula: ,in This is the normalized frequency corresponding to the minimum value of the average interferogram.

3. The dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals as described in claim 1, characterized in that: The simple tuning mode in step (1.1) is a single-frequency sine sweep. The interpolation process in step (1.2) uses the cubic spline interpolation method.

4. The dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals as described in claim 1, characterized in that, The process of step (2) is as follows: in the target complex tuning mode Down-driving laser, synchronously acquiring transmitted light intensity and reference light intensity According to the formula Calculate the reference interference intensity signal ,Record It serves as a reference interference signal for subsequent time-frequency relationship calibration.

5. The dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals as described in claim 4, characterized in that: The target complex tuning mode in step (2) is at least one of the following: a composite tuning mode of sinusoidal scanning and high-frequency sinusoidal modulation, a composite tuning mode of sinusoidal scanning signal and square wave modulation signal, a hybrid frequency modulation mode, and a strong nonlinear laser tuning mode.

6. The dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals as described in claim 1, characterized in that, The specific process of extracting discrete time-frequency relationships and locating key nodes in step (3) is as follows: The reference interference intensity signal obtained in step (2) Peak detection was performed, and the corresponding times of all interference peaks were extracted. and the location of the tuning inflection point; The normalized discrete time-frequency relationship is recursively assigned according to the free spectral range and extended to a step function: Let the normalized frequency reference value of the first interference peak be... Then the first The normalized discrete time-frequency relationship corresponding to each interference peak is as follows: Within the time intervals between all interference peaks, the normalized time-frequency relationship is defined as the value of the previous peak, forming a step function: ； in, For the first The peak moment of each interference peak.

7. The dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals as described in claim 1, characterized in that, The specific process of standardizing the local interference intensity in step (4) is as follows: The signal segment within the target interference period is smoothed using a smooth spline fitting method to obtain the smoothed interference intensity. ; Using the local normalized frequency relationship corresponding to this period ,Will Mapped to normalized frequency Smooth interference intensity as the independent variable The normalized frequency corresponding to the minimum point of smooth interference intensity. The signal is divided into two monotonic intervals, left and right, by the boundary. Perform range normalization within each monotonic interval, as shown in the following formula: ； in, The measured standardized interference intensity was used as the inversion input; The normalized frequency corresponding to the minimum value of the periodically smoothed signal is used to obtain the normalized interference intensity. .

8. The dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals as described in claim 1, characterized in that, The specific process of step (5) is as follows: based on the standard interferogram generated in step (1) Establish standardized interference intensity With local normalized frequency The mapping relationship; for the normalized interference intensity obtained in step (4) Based on its value and the minimum value of the standard interferogram By comparison, it is determined that it belongs to the left monotonic interval. or right monotonic interval And select the corresponding mapping relationship for inversion; through interpolation or lookup table in the mapping relationship of the selected interval, Converted to local normalized frequency This yields a locally normalized continuous time-frequency relationship.

9. The dynamic wavelength nonparametric point-by-point calibration method based on the multi-scale characteristics of interference signals as described in claim 1, characterized in that, The normalized continuous time-frequency relationship in step (6) is expressed as follows: ； The continuous time-frequency relationship in the physical frequency domain in step (6) is expressed as follows: 。

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