Phase and amplitude modulation noise iterative compensation method and system for optical frequency domain reflectometer

Abstract

The invention discloses a phase and amplitude modulation noise iterative compensation method and system for an optical frequency domain reflectometer, and belongs to the technical field of optical measurement and sensing, and the phase and amplitude modulation noise iterative compensation method for the optical frequency domain reflectometer comprises the steps: collecting an auxiliary interferometer signal and a measured device interference signal; extracting phase information of the auxiliary interferometer signal, and obtaining amplitude modulation noise information based on the phase information; carrying out phase noise suppression on the interference signal of the tested device, then carrying out Fourier transform to obtain a frequency spectrum, and calculating background noise and a signal peak value; generating an amplitude-modulated noise signal based on the signal peak position and the amplitude-modulated noise information; subtracting the amplitude modulation noise signal from the frequency spectrum to obtain a compensated signal; when the signal-to-noise ratio of the signal peak value to the background noise is lower than a set threshold value, iteration is stopped, and phase and amplitude modulation noise iteration compensation is completed. According to the invention, the system compensation cost can be saved, the compensation precision is improved, the system complexity is reduced, the robustness is improved, and the return loss measurement precision is improved.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement and sensing technology, specifically relating to a method and system for iterative compensation of phase and amplitude modulation noise for optical frequency domain reflectometers. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Optical frequency domain reflectometer (OFDR) is a high-precision distributed fiber optic measurement technology based on optical frequency scanning. By analyzing the interference signal between the reflected light and the reference light during laser frequency sweeping, it can achieve micron-level spatial resolution and is widely used in fiber optic sensing, device testing, and short-distance fault location. Its core challenge lies in the phase noise caused by the nonlinear frequency drift of the laser during the frequency sweeping process, and the amplitude fluctuations in the light source output, which introduce amplitude modulation noise and signal distortion, limiting measurement accuracy and dynamic range.

[0004] To address phase noise introduced by frequency sweep nonlinearity, current research focuses on real-time monitoring using an auxiliary interferometer combined with digital resampling algorithms, or using deep neural networks to predict nonlinear errors for phase correction. These methods significantly improve frequency linearity. Amplitude modulation compensation, on the other hand, stabilizes output power through an optoelectronic feedback loop or uses adaptive filtering algorithms to dynamically equalize the received signal, effectively suppressing the impact of amplitude fluctuations on reflection feature extraction. In recent years, hybrid compensation schemes that jointly optimize phase noise and amplitude stability have become a trend. For example, combining hardware predistortion with software post-processing further reduces system complexity and improves robustness, promoting the practical application of OFDR in complex environments.

[0005] However, the inventors discovered that existing technologies require the use of multi-channel auxiliary interferometers to acquire signals or increase hardware costs for feedback when compensating for the effects of amplitude modulation and phase noise, which increases the system cost. At the same time, it is difficult to guarantee the compensation accuracy during the compensation process, which is not conducive to the promotion and application of OFDR technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for iterative compensation of phase and amplitude modulation noise for optical frequency domain reflectometers. It only requires the auxiliary interference signal of one auxiliary interferometer, saving system compensation costs. By introducing a threshold function, the compensation accuracy is improved, the system complexity is reduced, and the robustness is enhanced, which is beneficial to improving the accuracy of return loss measurement.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the technical solution of the present invention provides an iterative compensation method for phase and amplitude modulation noise in an optical frequency domain reflectometer, comprising: S1. Acquire signals from the auxiliary interferometer and the interference signals from the device under test; S2. Extract the phase information of the auxiliary interferometer signal, and obtain amplitude modulation noise information based on the phase information; S3. After suppressing the phase noise of the interference signal of the device under test, perform Fourier transform to obtain the spectrum, and calculate the background noise and signal peak value; S4. Generate an amplitude modulation noise signal based on the signal peak position and amplitude modulation noise information; subtract the amplitude modulation noise signal from the spectrum to obtain the compensated signal; S5. Iterate through S4. Stop iterating when the signal-to-noise ratio of the peak signal to the background noise is lower than the set threshold, and complete the iterative compensation of phase and amplitude modulation noise.

[0008] In at least one embodiment, acquiring auxiliary interferometer signals and interference signals of the device under test specifically includes: connecting the device under test to the sweeping optical path, activating the narrow linewidth tunable laser, and splitting the sweeping light into three sweeping optical signals through an optical splitter. One of the sweeping optical signals is acquired by the signal acquisition and processing module after passing through the auxiliary interferometer and the balanced photodetector to obtain the auxiliary interferometer signal. The other two sweep frequency optical signals are transmitted in two paths: one passes through a circulator, the device under test, and then through the circulator again before entering the heterodyne coherent detection optical path; the other directly enters the heterodyne coherent detection optical path. Subsequently, these two optical signals interfere with each other. After the interference signal is balanced by photodetector, it is acquired by the signal acquisition and processing module to obtain the interference signal of the device under test.

[0009] In at least one embodiment, extracting the phase information of the auxiliary interferometer signal specifically includes: selecting an interpolation factor, performing interpolation processing on the auxiliary interferometer signal based on the interpolation factor to obtain the interpolated signal, and extracting the phase information using Hilbert transform.

[0010] In at least one embodiment, the interpolation factor is selected to satisfy the condition that the difference between the interpolated signal phase and the target phase is less than 0.1 radians, and the amplitude modulation noise information signal-to-noise ratio is greater than 30 dB.

[0011] In at least one embodiment, obtaining amplitude modulation noise information based on the phase information specifically includes: selecting data point positions based on the phase information, and extracting amplitude modulation noise information based on the data point positions; wherein, the data point positions satisfy:

[0012] In the formula, Indicates the location of data points Phase information; Indicates the number of phase intervals; It is an integer. .

[0013] In at least one embodiment, phase noise suppression is performed on the interference signal of the device under test, specifically including: interpolating the interference signal of the device under test based on a selected interpolation factor to obtain an interpolated signal, extracting the data corresponding to the data point position in the interpolated signal, and obtaining the phase noise suppressed interference signal of the device under test.

[0014] In at least one embodiment, generating an amplitude-modulated noise signal based on the signal peak position and amplitude-modulated noise information specifically includes: extracting the position information of the signal peak, using the position information as the modulation frequency to modulate the amplitude-modulated noise information, thereby obtaining the amplitude-modulated noise signal corresponding to the signal peak.

[0015] Secondly, the technical solution of the present invention also provides a phase and amplitude modulation noise iterative compensation system for an optical frequency domain reflectometer, comprising: The signal acquisition module is configured to acquire signals from the auxiliary interferometer and interference signals from the device under test. The peak calculation module is configured to: extract the phase information of the auxiliary interferometer signal, obtain amplitude modulation noise information based on the phase information; perform Fourier transform on the interference signal of the device under test after phase noise suppression to obtain the spectrum, and calculate the background noise and signal peak value; The iterative compensation module is configured to: generate an amplitude-modulated noise signal based on the signal peak position and amplitude-modulated noise information; subtract the amplitude-modulated noise signal from the spectrum to obtain the compensated signal; perform iterative compensation, and stop iterating when the signal-to-noise ratio of the signal peak to the background noise is lower than a set threshold, thus completing the iterative compensation of phase and amplitude-modulated noise.

[0016] Thirdly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the phase and amplitude modulation noise iterative compensation method for an optical frequency domain reflectometer as described in the first aspect.

[0017] Fourthly, the present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps in the iterative compensation method for phase and amplitude modulation noise for an optical frequency domain reflectometer as described in the first aspect.

[0018] The beneficial effects of the above-described technical solution of the present invention are as follows: The phase and amplitude modulation noise iterative compensation method for optical frequency domain reflectometers of this invention is a hybrid compensation scheme that simultaneously optimizes phase and amplitude modulation noise. First, an auxiliary interferometer is used to demodulate the time-varying frequency and amplitude modulation information of the swept frequency light source. Then, phase noise and amplitude modulation effects are gradually repaired to prevent distortion of the interference signal, thereby improving the accuracy of return loss measurement. This method only requires one auxiliary interferometer signal, saving system compensation costs. Simultaneously, by introducing a threshold function to improve compensation accuracy, it is beneficial for the further development of optical frequency domain reflectometers in the field of high-precision sensing. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a schematic diagram of the phase and amplitude modulation noise iterative compensation method for an optical frequency domain reflectometer disclosed in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the signal acquisition system structure disclosed in Embodiment 1 of the present invention; Figure 3 This is a schematic flowchart of the phase and amplitude modulation noise iterative compensation method for an optical frequency domain reflectometer disclosed in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the signal processing process of the auxiliary interferometer disclosed in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the interference signal processing process of the device under test disclosed in Embodiment 1 of the present invention. Detailed Implementation

[0021] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] As described in the background section, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method and system for iterative compensation of phase and amplitude modulation noise for optical frequency domain reflectometers. It only requires the auxiliary interference signal of one auxiliary interferometer, saving system compensation costs. By introducing a threshold function, the compensation accuracy is improved, the system complexity is reduced, and the robustness is enhanced, which is beneficial to improving the accuracy of return loss measurement.

[0023] Example 1 In a typical embodiment of the present invention, such as Figures 1 to 5 As shown, this embodiment discloses an iterative compensation method for phase and amplitude modulation noise in an optical frequency domain reflectometer, specifically including the following steps: S1. Acquire signals from the auxiliary interferometer and the interference signals from the device under test; S2. Extract the phase information of the auxiliary interferometer signal, and obtain the amplitude modulation noise information based on the phase information; S3. After suppressing the phase noise of the interference signal of the device under test, perform Fourier transform to obtain the spectrum, and calculate the background noise and signal peak value; S4. Generate an amplitude modulation noise signal based on the signal peak position and amplitude modulation noise information; subtract the amplitude modulation noise signal from the spectrum to obtain the compensated signal; S5. Iterate through S4. Stop iterating when the signal-to-noise ratio of the peak signal to the background noise is lower than the set threshold, and complete the iterative compensation of phase and amplitude modulation noise.

[0024] The core principle of this method is as follows: In an optical frequency domain reflectometer (OFDR) system, the expression for the interference signal output of the interferometer under test is:

[0025] In the formula, This indicates the time delay difference information generated by the interferometer under test; This represents the amplitude of the photoelectric field output by the light source. Its amplitude changes with time, exhibiting a certain periodic modulation, which leads to amplitude modulation noise. Specifically, it can be expressed as:

[0026] In the formula, Indicates the output of the light source. Sub-modulation frequency and harmonic frequency; Indicates the first Second harmonic amplitude.

[0027] The expression for the interference signal output of the reference interferometer is:

[0028] It can be seen that the auxiliary interferometer signal Interference signal with the device under test Zhongdu contains It is the instantaneous light frequency output by the light source, which can be specifically expressed as:

[0029] It can be seen that the instantaneous light frequency In addition to containing linear frequency sweep information It also includes a portion of phase noise (i.e., swept-frequency nonlinearity). Due to the presence of frequency sweep nonlinearity, the interference signal is broadened.

[0030] If the nonlinear part After removing and considering only amplitude modulation noise, the interference signal after Fourier transform, except for... corresponding frequency In addition to the information present, the amplitude will also be at the modulation frequency. and There are signals at the difference frequency and the combination frequency, and the final interference signal can be expressed as:

[0031] because The amplitude of the electric field output by the light source, therefore There are also similar The same amplitude modulation noise, except that the center frequency is different. Replace with , represented as .

[0032] To simultaneously suppress the effects of frequency sweep nonlinearity and amplitude modulation noise, this embodiment first obtains the result through Hilbert transformation. Obtaining phase Then, the instantaneous light frequency is obtained using the following formula. :

[0033] Then select the following points for the phase:

[0034] in A positive integer, representing the number of data intervals selected. A higher value results in a better amplitude modulation noise signal-to-noise ratio (SNR), but it also increases the computation time. Therefore, the value needs to be selected based on the amplitude modulation noise SNR; generally, an appropriate value should be chosen. The signal-to-noise ratio of the amplitude modulation noise should be at least 30 dB. Substituting these extracted points into the expression for the interference signal of the reference interferometer, we obtain:

[0035] At this point, the nonlinear part of the frequency sweep has been eliminated. Remove, and perform a Fourier transform on the above signal. It can be obtained ,and It can be removed through signal demodulation, ultimately yielding amplitude modulation noise. .

[0036] Due to the auxiliary interferometer signal Acting as a reference clock, extracting This can eliminate sweep frequency nonlinearity. Each signal has amplitude modulation noise. However, the signal with the highest amplitude is definitely a valid signal, so we only need to find the frequency corresponding to the highest signal in sequence. Then use Modulation amplitude modulation noise is obtained Then, the frequency was eliminated using simple addition and subtraction. The corresponding amplitude modulation noise is sufficient.

[0037] Based on the above principles, the phase and amplitude modulation noise iterative compensation method for optical frequency domain reflectometers will be described in detail below with reference to specific implementation methods.

[0038] S1. Acquire the signals from the auxiliary interferometer and the interference signals from the device under test.

[0039] In this step, the following is used: Figure 2 The acquisition system shown acquires signals from the auxiliary interferometer and interference signals from the device under test.

[0040] Specifically, the device under test 204 is connected to the frequency sweeping optical path, and the narrow linewidth tunable laser 201 is activated. The frequency sweeping light is split into three frequency sweeping optical signals by the optical splitter 202. One of the frequency sweeping optical signals passes through the auxiliary interferometer 205 and the balanced photodetector 206 and is then acquired by the signal acquisition and processing module 209 to obtain the auxiliary interferometer signal. Specifically, it can be expressed as:

[0041] In the formula, This indicates the time delay difference information generated by the auxiliary interferometer; This represents the amplitude of the output photoelectric field of a narrow-linewidth tunable laser. The amplitude of this field varies with time, exhibiting a certain periodic modulation, which leads to amplitude modulation noise. Specifically, it can be expressed as:

[0042] In the formula, This indicates the output of a narrow-linewidth tunable laser. Sub-modulation frequency and harmonic frequency; Indicates the first Second harmonic amplitude.

[0043] The other two sweeping optical signals are transmitted in two paths: one passes through circulator 203, the device under test (DUT) 204, then back through circulator 203, and finally into the heterodyne coherent detection optical path 207; the other directly enters the heterodyne coherent detection optical path 207. These two optical signals then interfere with each other. The interference signal is balanced by photodetector 208 and then acquired by signal acquisition and processing module 209 to obtain the interference signal from the DUT. Specifically, it can be expressed as:

[0044] In the formula, This indicates the time delay difference information generated by the device under test.

[0045] S2. Extract the phase information of the auxiliary interferometer signal, and obtain the amplitude modulation noise information based on the phase information.

[0046] To simultaneously suppress the effects of frequency sweep nonlinearity and amplitude modulation noise, an appropriate interpolation factor is first selected in this step. Based on this interpolation factor For auxiliary interferometer signals conduct Linear interpolation is used to obtain the interpolated signal. And the Hilber transform was used to extract the auxiliary interferometer signal. Phase information .

[0047] Then, select an appropriate number of phase intervals. Based on phase information Select data point location Among them, the location of data points satisfy:

[0048] In the formula, Indicates the location of data points Phase information; Indicates the number of phase intervals; It is an integer. .

[0049] Next, extract the interpolated signal. Corresponding location information The data is used to obtain the amplitude of the processed auxiliary interference signal. Then filter out Modulation frequency, to obtain amplitude modulation noise information .

[0050] In this embodiment, the interpolation factor The selection must satisfy the condition that the difference between the interpolated signal phase and the target phase is less than 0.1 radians, i.e. Meanwhile, amplitude modulation noise information The signal-to-noise ratio is greater than 30dB.

[0051] S3. After suppressing the phase noise of the interference signal of the device under test, perform Fourier transform to obtain the spectrum, and calculate the background noise and signal peak.

[0052] In this step, the interference signal of the device under test is first analyzed. conduct Double interpolation is used to obtain the interpolated signal. Extract the interpolated signal The data corresponding to position information Z is used to obtain the phase noise-suppressed interference signal of the device under test. .

[0053] Then, the interference signal of the device under test after phase noise suppression. Perform a Fourier transform to obtain the spectrum. And based on the spectrum Calculate the background noise and signal peak Background noise The signal peak value Vmax is obtained by reading the amplitude of the highest noise signal.

[0054] S4. Generate an amplitude modulation noise signal based on the signal peak position and amplitude modulation noise information; subtract the amplitude modulation noise signal from the spectrum to obtain the compensated signal.

[0055] In this step, the signal peak value is extracted first. Location information With this location information Modulation frequency modulation amplitude noise information Thus, the signal peak value is obtained. Corresponding amplitude modulation noise signal .

[0056] Then, from the spectrum Subtract the amplitude modulation noise signal from the middle To remove amplitude modulation noise, the compensated spectrum signal is obtained. This process can be represented as:

[0057] In the formula, This indicates the number of iterations to remove amplitude modulation noise. .

[0058] S5. Iterate through S4. Stop iterating when the signal-to-noise ratio of the peak signal to the background noise is lower than the set threshold, and complete the iterative compensation of phase and amplitude modulation noise.

[0059] In this step, step S4 is executed iteratively until the signal peak value is reached. With background noise The iteration stops when the signal-to-noise ratio is below 50dB, at which point the phase and amplitude modulation noise iteration compensation is completed.

[0060] like Figure 3 As shown, the complete process of the phase and amplitude modulation noise iterative compensation method for optical frequency domain reflectometers proposed in this embodiment is as follows: The first step is to measure the auxiliary interference signal according to step 102. like Figure 4 As shown in 401, due to the phase noise introduced by the frequency sweep nonlinearity, the auxiliary interference signal 401 is no longer a sharp interference signal, the signal is broadened, and the system resolution decreases.

[0061] The second step is to set the interpolation factor according to steps 103-106. For auxiliary interference signals Interpolation obtained Then, the interference signal is extracted using the Hilbert transform. Phase information ;make ,Will The closest in amplitude ( Location information corresponding to the data Extract, extract Data points, and make judgments If the requirements are met, proceed to the next step; otherwise, set the interpolation factor. Run the loop.

[0062] Third step, following steps 107-109, use the formula The amplitude modulation noise information is obtained, and the amplitude modulation noise information result is as follows: Figure 4 As shown in 403, 402 is the intermediate frequency and the modulation frequency. The amplitude modulation noise is symmetrical about 402. Figure 4 In the diagram, 403 represents the highest amplitude modulation noise at 53.1 dB, and 404 represents the highest noise signal at 82.5 dB. 82.5 - 53.1 = 29.4 dB. At this point, the amplitude modulation noise signal-to-noise ratio (SNR) is less than 30 dB, which is insufficient to meet the SNR requirement. Therefore, the phase interval needs to be reduced. ,make Repeat the first two steps.

[0063] Fourth step, reduce the phase interval Subsequently, the amplitude modulation noise signal-to-noise ratio improved, such as Figure 4 The highest noise signal in the 405 becomes 92.4dB, while the highest amplitude modulation noise in the 403 remains at 53.1dB. At this point, the amplitude modulation noise meets the signal-to-noise ratio requirement.

[0064] Fifth step, following step 110, pass the filter to... Figure 4 The highest modulation frequency 402 is filtered out to obtain amplitude modulation noise information. ,like Figure 4 As shown in Figure 406.

[0065] Step 6, following step 111, the interference signal of the device under test. like Figure 5 As shown in Figure 501, due to the influence of phase noise, the interference signal is difficult to distinguish, and the signal is subjected to... Interpolation value And extract the data point at position Z to obtain ,right The spectrum is obtained by performing a Fourier transform. like Figure 5 As shown in Figure 502, since the phase noise has been suppressed, the interference signal can be distinguished. However, due to the influence of amplitude modulation noise, some stray interference signals exist in the signal, affecting data analysis, such as... Figure 5 The detailed image of 502 is shown below.

[0066] Step 7, following steps 112-114, let The highest signal in the interference signal That is, signal 502 must be a valid signal, with an amplitude of -42dB. The noise floor of signal 503 is N=-123dB. At this point, the highest signal-to-noise ratio is 123-42=81dB, which is greater than 50dB. Therefore, amplitude modulation noise must be present in the vicinity of this signal. ,by signal location As modulation frequency get amplitude modulation noise corresponding to the signal Then use the formula get The result after suppressing the influence of amplitude modulation noise at the location, such as Figure 5 As shown in Figure 503, the interference signal becomes easier to distinguish due to the suppression of amplitude modulation noise.

[0067] Step 8, following steps 115-118, let Extract the peak value after removing 504. Location information Using position signals and amplitude modulation noise Generate amplitude modulation noise Then, the corresponding amplitude modulation noise is filtered out. This process is repeated until amplitude modulation noise suppression is completed for signals with a signal-to-noise ratio greater than 50dB. The result after suppression is... like Figure 5 As shown in Figure 505, only three sharp interference signals remain, corresponding to the return loss information of the three reflection points in the optical path.

[0068] Example 2 In a typical embodiment of the present invention, this embodiment discloses an iterative compensation system for phase and amplitude modulation noise for an optical frequency domain reflectometer, comprising: The signal acquisition module is configured to acquire signals from the auxiliary interferometer and interference signals from the device under test. The peak calculation module is configured to: extract the phase information of the auxiliary interferometer signal, obtain amplitude modulation noise information based on the phase information; perform Fourier transform on the interference signal of the device under test after phase noise suppression to obtain the spectrum, and calculate the background noise and signal peak value; The iterative compensation module is configured to: generate an amplitude-modulated noise signal based on the signal peak position and amplitude-modulated noise information; subtract the amplitude-modulated noise signal from the spectrum to obtain the compensated signal; perform iterative compensation, and stop iterating when the signal-to-noise ratio of the signal peak to the background noise is lower than a set threshold, thus completing the iterative compensation of phase and amplitude-modulated noise.

[0069] Example 3 In a typical embodiment of the present invention, this embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps in the iterative compensation method for phase and amplitude modulation noise of an optical frequency domain reflectometer as described in Embodiment 1. These steps include: S1. Acquire signals from the auxiliary interferometer and the interference signals from the device under test; S2. Extract the phase information of the auxiliary interferometer signal, and obtain the amplitude modulation noise information based on the phase information; S3. After suppressing the phase noise of the interference signal of the device under test, perform Fourier transform to obtain the spectrum, and calculate the background noise and signal peak value; S4. Generate an amplitude modulation noise signal based on the signal peak position and amplitude modulation noise information; subtract the amplitude modulation noise signal from the spectrum to obtain the compensated signal; S5. Iterate through S4. Stop iterating when the signal-to-noise ratio of the peak signal to the background noise is lower than the set threshold, and complete the iterative compensation of phase and amplitude modulation noise.

[0070] Example 4 In a typical embodiment of the present invention, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the iterative compensation method for phase and amplitude modulation noise of an optical frequency domain reflectometer as described in Embodiment 1. These steps include: S1. Acquire signals from the auxiliary interferometer and the interference signals from the device under test; S2. Extract the phase information of the auxiliary interferometer signal, and obtain amplitude modulation noise information based on the phase information; S3. After suppressing the phase noise of the interference signal of the device under test, perform Fourier transform to obtain the spectrum, and calculate the background noise and signal peak value; S4. Generate an amplitude modulation noise signal based on the signal peak position and amplitude modulation noise information; subtract the amplitude modulation noise signal from the spectrum to obtain the compensated signal; S5. Iterate through S4. Stop iterating when the signal-to-noise ratio of the peak signal to the background noise is lower than the set threshold, and complete the iterative compensation of phase and amplitude modulation noise.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An iterative compensation method for phase and amplitude modulation noise in an optical frequency domain reflectometer, characterized in that, include: S1. Acquire signals from the auxiliary interferometer and the interference signals from the device under test; S2. Extract the phase information of the auxiliary interferometer signal, and obtain amplitude modulation noise information based on the phase information; S3. After suppressing the phase noise of the interference signal of the device under test, perform Fourier transform to obtain the spectrum, and calculate the background noise and signal peak value; S4. Generate an amplitude modulation noise signal based on the signal peak position and amplitude modulation noise information; subtract the amplitude modulation noise signal from the spectrum to obtain the compensated signal; S5. Iterate through S4. Stop iterating when the signal-to-noise ratio of the peak signal to the background noise is lower than the set threshold, and complete the iterative compensation of phase and amplitude modulation noise.

2. The iterative compensation method for phase and amplitude modulation noise for an optical frequency domain reflectometer as described in claim 1, characterized in that, Acquiring auxiliary interferometer signals and interference signals of the device under test (DUT) specifically includes: connecting the DUT into the sweeping optical path, activating the narrow linewidth tunable laser, and splitting the sweeping light into three sweeping optical signals through an optical splitter. One of the sweeping optical signals passes through the auxiliary interferometer and the balanced photodetector and is then acquired by the signal acquisition and processing module to obtain the auxiliary interferometer signal. The other two sweep frequency optical signals are transmitted in two paths: one passes through a circulator, the device under test, and then through the circulator again before entering the heterodyne coherent detection optical path; the other directly enters the heterodyne coherent detection optical path. Subsequently, these two optical signals interfere with each other. After the interference signal is balanced by photodetector, it is acquired by the signal acquisition and processing module to obtain the interference signal of the device under test.

3. The iterative compensation method for phase and amplitude modulation noise for an optical frequency domain reflectometer as described in claim 1, characterized in that, Extracting phase information from the auxiliary interferometer signal specifically includes: selecting an interpolation factor, performing interpolation processing on the auxiliary interferometer signal based on the interpolation factor to obtain the interpolated signal, and extracting phase information using Hilbert transform.

4. The iterative compensation method for phase and amplitude modulation noise for an optical frequency domain reflectometer as described in claim 3, characterized in that, The interpolation factor should be selected to ensure that the difference between the interpolated signal phase and the target phase is less than 0.1 radians, and that the amplitude modulation noise information signal-to-noise ratio is greater than 30 dB.

5. The iterative compensation method for phase and amplitude modulation noise for an optical frequency domain reflectometer as described in claim 3, characterized in that, Obtaining amplitude modulation noise information based on the phase information specifically includes: selecting data point positions based on the phase information, and extracting amplitude modulation noise information based on the data point positions; wherein, the data point positions satisfy: In the formula, Indicates the location of data points Phase information; Indicates the number of phase intervals; It is an integer. .

6. The iterative compensation method for phase and amplitude modulation noise for an optical frequency domain reflectometer as described in claim 5, characterized in that, Phase noise suppression of the interference signal of the device under test (DUT) specifically includes: interpolating the interference signal of the DUT based on the selected interpolation factor to obtain the interpolated signal, extracting the data at the corresponding data point positions in the interpolated signal, and obtaining the phase noise suppressed interference signal of the DUT.

7. The iterative compensation method for phase and amplitude modulation noise for an optical frequency domain reflectometer as described in claim 1, characterized in that, The method for generating an amplitude-modulated noise signal based on the signal peak position and amplitude-modulated noise information includes: extracting the position information of the signal peak, using the position information as the modulation frequency to modulate the amplitude-modulated noise information, thereby obtaining the amplitude-modulated noise signal corresponding to the signal peak.

8. An iterative compensation system for phase and amplitude modulation noise in an optical frequency domain reflectometer, characterized in that, include: The signal acquisition module is configured to acquire signals from the auxiliary interferometer and interference signals from the device under test. The peak calculation module is configured to: extract the phase information of the auxiliary interferometer signal, and obtain amplitude modulation noise information based on the phase information; After suppressing phase noise in the interference signal of the device under test, a Fourier transform is performed to obtain the spectrum, and the background noise and signal peak value are calculated. The iterative compensation module is configured to: generate an amplitude-modulated noise signal based on the signal peak position and amplitude-modulated noise information; subtract the amplitude-modulated noise signal from the spectrum to obtain the compensated signal; perform iterative compensation, and stop iterating when the signal-to-noise ratio of the signal peak to the background noise is lower than a set threshold, thus completing the iterative compensation of phase and amplitude-modulated noise.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the iterative compensation method for phase and amplitude modulation noise for an optical frequency domain reflectometer as described in any one of claims 1-7.

10. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the phase and amplitude modulation noise iterative compensation method for an optical frequency domain reflectometer as described in any one of claims 1-7.

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