Method for avoiding polarization fading points based on range control chart and Φ-otdr original data

Abstract

The application belongs to the technical field of photoelectric data processing, and particularly relates to a method for avoiding polarization fading points based on an extreme difference control chart and Φ-OTDR original data, which comprises the following steps: grouping according to a set sample size, calculating an extreme difference, an extreme difference average value and an action limit; comparing the extreme difference with the action limit to output corresponding comparison values, and adding the comparison values to obtain corresponding cumulative values; the original back Rayleigh scattering signal is processed based on the extreme difference control chart, the original data of each optical pulse is grouped and the extreme difference is calculated, then the extreme difference average value and the action limit are calculated, the comparison values of the mutation positions are obtained based on the action limit, the value of the comparison value is 0 or 1, then the comparison values of the same fiber sampling positions corresponding to all optical pulses are added, the non-polarization fading point area which can be used as a candidate reference point can be easily obtained, and the calculation difficulty is reduced.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic data processing technology, specifically relating to a method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data. Background Technology

[0002] In a phase-domain optical reflectometer (PDT), when a laser pulse is injected into an optical fiber, Rayleigh scattering occurs due to the microscopic density inhomogeneities within the fiber material. A portion of the scattered light returns to the fiber's injection port. This returned Rayleigh scattering, also known as backscattered Rayleigh light, is collected by a photodetector and used to analyze events along the fiber's path. Furthermore, the location of the event can be determined based on the relationship between the propagation time of the laser pulse and the backscattered Rayleigh light within the fiber and its length. When the optical fiber senses an external disturbance, the phase of the light changes. Both theoretical research and experimental measurements show that the change in phase is directly proportional to the magnitude of the disturbance. Therefore, PDT can not only detect the location of external disturbances but also quantitatively represent them. Based on this, PDT can be applied in many fields, including geophysical exploration, energy and power monitoring, and equipment fault diagnosis. Particularly in wind power generation, vibration signals measured by PDT can be used for blade health monitoring and tower stability assessment.

[0003] Therefore, it is necessary to obtain the phase information in the backscattered Rayleigh signal generated by the photodetector after the backscattered Rayleigh light passes through the backscattered light. Since heterodyne detection offers a higher signal-to-noise ratio in phase-optical time-domain reflectometers (TIDRs), and the phase change exists in the fiber region after the disturbance event, heterodyne detection is more advantageous for signal demodulation, thus becoming a commonly chosen detection method in TDRs. Orthogonal demodulation can be implemented digitally, avoiding the requirement for consistent device parameters, making digital orthogonal demodulation a superior choice among various demodulation methods. For this reason, heterodyne detection and digital orthogonal demodulation are currently the most common combination in the research and application of phase-optical time-domain reflectometers. Because the timing of the modulated optical pulse differs slightly from the expected timing, phase-optical time-domain reflectometers based on this combination need to select a reference point before the disturbance event for subtraction when solving for the phase signal to eliminate the difference in phase along the optical pulse sequence direction. However, if the reference point is located at the fiber sampling position where the polarization fading point is located, the phase information cannot be correctly demodulated.

[0004] Therefore, the reference point must not be located at the fiber sampling position corresponding to the polarization fading point, and the significance of avoiding fading points is self-evident. Furthermore, in the process of avoiding fading points, complex calculations should be avoided as much as possible to improve the real-time performance of signal processing. Therefore, in-depth research is needed on how to avoid the fiber sampling position corresponding to the fading point. To this end, a method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data has been invented, providing fiber sampling positions for non-polarization fading points and candidate reference points.

[0005] It should be noted that the information disclosed in this background section is only for understanding the background technology of the present application concept, and therefore, the above description is not considered to constitute prior art information. Summary of the Invention

[0006] This disclosure provides at least one method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data.

[0007] In a first aspect, embodiments of this disclosure provide a method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data, comprising: Step S1: The Φ-OTDR hardware device acquires backscattered Rayleigh signals in chronological order and calibrates a two-dimensional array corresponding to each backscattered Rayleigh signal according to the emission order of the light pulses; Step S2: The Φ-OTDR hardware device groups the backscattered Rayleigh signals in each light pulse according to a set sample size to calculate the range of each group of backscattered Rayleigh signals, and then calculates the average range of the backscattered Rayleigh signals corresponding to each light pulse; Step S3: Φ - The Φ-OTDR hardware device calculates the action limit corresponding to each optical pulse based on the average range of the backscattered Rayleigh signal corresponding to each optical pulse and the proportionality coefficient; Step S4: The Φ-OTDR hardware device compares the range corresponding to each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to the optical pulse to output the corresponding comparison value, and adds the comparison values ​​of the same group number of each optical pulse to obtain the corresponding cumulative value; Step S5: When the cumulative value is greater than 0, the Φ-OTDR hardware device obtains the cumulative value and restores the corresponding one-dimensional array to determine the candidate region of the reference point for non-polarization fading.

[0008] In an optional implementation, step S1 includes: the Φ-OTDR hardware device acquiring backscattered Rayleigh signals in chronological order, i.e., the Φ-OTDR raw data I. D ;Transfer one-dimensional Φ-OTDR raw data I D Convert to a two-dimensional array E(m,n); where m is the number of light pulses emitted, and the value of m is 1≤m≤M; n is the number of sampling points of the optical fiber, and the value of n is 1≤n≤N; M is the maximum number of light pulses emitted within the observation range; and N is the maximum number of sampling points of the optical fiber within the observation range.

[0009] In one optional implementation, step S2 includes: for any number of optical pulses m x Let the sample size be D, so that the two-dimensional array E(m) can be... x Transform H(m,n) into H(m) x ,j,i)=E(m x (j-1)×D+i), where j is the group number of the backscattered Rayleigh signals in this light pulse after being grouped according to a set sample size, i is the index of a single backscattered Rayleigh signal value in each group, and the value of i ranges from 1 to i to D, while the minimum value of j is 1, the remainder of N divided by D is R, and the maximum value of j is (NR) / D; the range of any group of backscattered Rayleigh signals is HH(m x ,j)=max{E(m x ,(j-1)×D+1),…,E(m x ,j×D)}-min{E(m x ,(j-1)×D+1),…,E(m x ,j×D)}, where max and min are the maximum and minimum values ​​respectively; for any number of light pulses m x Calculate the average range of the backscattered Rayleigh signal corresponding to the light pulse.

[0010] In an optional implementation, step S3 includes: setting a proportionality coefficient as a, where a > 0; calculating the action limit corresponding to each light pulse.

[0011] In an optional implementation, step S4 includes: comparing the range corresponding to each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to the optical pulse; when the range corresponding to any group of backscattered Rayleigh signals in any optical pulse is greater than the action limit corresponding to the optical pulse, the output comparison value is 1; when the range corresponding to any group of backscattered Rayleigh signals in any optical pulse is less than or equal to the action limit corresponding to the optical pulse, the output comparison value is 0.

[0012] In an optional implementation, step S4 further includes: in any light pulse m x The comparison value output at group number j is And m x It is any value of m; the sum of the comparison values ​​of the same group number of each optical pulse is used to obtain the corresponding cumulative value. And j x It is any value that belongs to j.

[0013] In an optional implementation, the method of step S5 includes: when U(j x When ) is greater than 0, obtain the corresponding j. x The value of n, and n x =j x ×D, and n x If it is any value of n, then determine [n] x -D+1,n x [ ] represents the candidate region for the reference point of non-polarization fading.

[0014] In one alternative implementation, Φ-OTDR raw data I D The spatial length corresponding to the uniform sampling interval is D_sample. When the Φ-OTDR hardware device detects heterodyne, the spatial length corresponding to a single cycle of the difference frequency is greater than ten times D_sample.

[0015] In one alternative implementation, the light source frequency fluctuation of the Φ-OTDR hardware device is less than 50kHz.

[0016] Secondly, this disclosure also provides a system employing the above-described method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data, comprising: a Φ-OTDR hardware device; wherein the Φ-OTDR hardware device acquires backscattered Rayleigh signals in chronological order and calibrates a two-dimensional array corresponding to each backscattered Rayleigh signal according to the emission order of the light pulses; the Φ-OTDR hardware device groups the backscattered Rayleigh signals in each light pulse according to a set sample size to calculate the range of each group of backscattered Rayleigh signals, and then calculates the backscattered Rayleigh signal corresponding to each light pulse. The Φ-OTDR hardware device calculates the action limit corresponding to each optical pulse based on the average range of the backscattered Rayleigh signal corresponding to each optical pulse and the proportionality coefficient; the Φ-OTDR hardware device compares the range corresponding to each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to that optical pulse to output the corresponding comparison value, and adds the comparison values ​​of the same group number of each optical pulse to obtain the corresponding cumulative value; when the cumulative value is greater than 0, the Φ-OTDR hardware device obtains the cumulative value and restores the corresponding one-dimensional array to determine the candidate region of the reference point for non-polarization fading.

[0017] The beneficial effect of this invention is that it processes the detected raw backscattered Rayleigh signal based on a range control map. Specifically, it first organizes the detected raw Φ-OTDR data, then groups the raw Φ-OTDR data of each optical pulse and calculates the range, then calculates the mean range and action limit, and obtains the comparison value at the abrupt change based on the action limit. The comparison value is either 0 or 1. Then, it adds the comparison values ​​at the same fiber sampling position corresponding to all optical pulses, which can easily obtain the non-polarization fading point region that can be used as a candidate reference point, thereby reducing the computational difficulty.

[0018] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A flowchart illustrating a method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data, provided in this embodiment of the disclosure;

[0022] Figure 2 A schematic diagram of backscattered Rayleigh signals superimposed according to an embodiment of this disclosure;

[0023] Figure 3 A schematic diagram of the subgroup range values ​​corresponding to the first optical pulse provided in an embodiment of this disclosure;

[0024] Figure 4 A schematic diagram showing the average range of all optical pulses provided in the embodiments of this disclosure;

[0025] Figure 5 A schematic diagram showing the range action limits corresponding to all optical pulses provided in the embodiments of this disclosure;

[0026] Figure 6 A schematic diagram showing the comparison results of the range and action limit corresponding to the first optical pulse provided in this embodiment of the disclosure;

[0027] Figure 7 A schematic diagram of the off-boundary summation provided for embodiments of this disclosure;

[0028] Figure 8 This is a schematic diagram showing the comparison between the extra-boundary sum and the modulus value provided in an embodiment of this disclosure. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

[0030] The terminology used herein is for the purpose of describing specific exemplary configurations only and is not intended to be limiting. As used herein, the singular articles “a,” “an,” and “the” may also be intended to include plural forms unless otherwise clearly stated herein. The terms “comprising,” “including,” and “having” are inclusive and thus specify the presence of features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as requiring them to be performed in the specific order discussed or shown, unless specifically identified as such. Additional or alternative steps may be employed.

[0031] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0032] Φ-OTDR (Phase Optical Time Domain Reflectometer) refers to a phase optical time domain reflectometer.

[0033] Research has shown that the backscattered Rayleigh signal output by a heterodyne-detected phase optical time-domain reflectometer can be expressed as follows: Where t is the time from when the probe pulse leaves the fiber injection port to when the backscattered Rayleigh light returns to the fiber injection port, and E R and E LO These are the amplitude factors of the backscattered Rayleigh light and the reference light, respectively, A R and A LO These are the polarization-related factors of the backscattered Rayleigh light and the reference light, respectively. The phase is caused by external disturbances, and Δω is the modulation frequency. The modulation frequency is usually generated by an electro-optic modulator or an acousto-optic modulator, and its frequency is generally in the range of tens to hundreds of megahertz. The polarization-dependent factor causes the backscattered Rayleigh signal to increase and decrease repeatedly along the length of the fiber. However, due to the randomness of the factors affecting the refractive index, this cyclical change is not periodic. For the demodulation of the phase signal, if the polarization-dependent factor, i.e., A... R A LO When the product of the two is zero, that is, when the backscattered Rayleigh signal light and the reference light are polarization mismatched, it is impossible to extract phase information from the intensity I(t) of the backscattered Rayleigh signal. However, judging solely from the intensity of the backscattered Rayleigh signal, A R A LO While the product of A and B being zero affects the solution for the phase signal, it does not affect the change in the intensity of the backscattered Rayleigh signal itself. In other words, A R A LO The product being zero does not affect the trend of the intensity of the backscattered Rayleigh signal itself. A R A LOWhen the product of the two values ​​is zero, the backscattered Rayleigh signal is zero. However, if the backscattered Rayleigh signal is converted into a magnitude (obtained by orthogonal demodulation), the magnitude at this point is the minimum. Since the magnitude is an absolute value, it is also zero. In the magnitude curve, besides the minimum, there are several local minima. These local minima are not caused by polarization mismatch between the backscattered Rayleigh signal and the reference light; they are caused by interference phenomena due to the non-uniform refractive index distribution throughout the fiber. Therefore, although local minima appear, they are generally not zero. These polarization and interference factors together cause the backscattered Rayleigh curve in a heterodyne-detected phase-optic time-domain reflectometer to follow the fiber length. Furthermore, for a heterodyne-detected phase-optic time-domain reflectometer, the backscattered Rayleigh signal is also modulated by a higher intermediate-frequency cosine term generated by the acousto-optic modulator. The waveform trend of the backscattered Rayleigh signal caused by polarization and interference factors is the envelope of the curve. Ideally, the fiber sampling position corresponding to the zero value of the envelope ("zero point") is the location of polarization. However, due to factors such as optical pulse modulation jitter, the "zero point" may change slightly. The modulation of the high-frequency cosine term makes it difficult to determine the location of polarization fading points. Moreover, the presence of various types of noise can make determining the location of polarization fading points even more difficult. Eliminating polarization fading points is crucial for accurate demodulation of the phase signal. Therefore, accurately and quickly eliminating the location of polarization fading points is essential.

[0034] Based on the above research, this disclosure provides a method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data. It introduces the concept of range control charts and utilizes the calculation process of the control chart. A range control chart divides the sampled data into several subgroups according to a certain sample size, calculates the range value of each subgroup, and calculates the center line, upper control limit, and lower control limit based on all the range values. Since the range value is non-negative, when the calculated lower control limit is negative, it is considered 0. In this case, the main focus is on the upper control limit, because exceeding the upper limit indicates increased process variation, which is an abnormal signal that requires action. Therefore, the upper control limit can be simply mapped to the action limit. Because the range control chart can monitor changes in process variation, it is sensitive to abnormal fluctuations. In equation (1), although the higher intermediate frequency cosine term generated by the acousto-optic modulator is the fastest changing term, it does not itself cause significant changes in data variation. Therefore, applying the range control chart to the Φ-OTDR raw data can, to a certain extent, directly shield the influence of the higher intermediate frequency cosine term. After removing the influence of the higher mid-frequency cosine term, the Φ-OTDR raw data is to be observed for its own envelope. Although polarization fading will directly cause the phase to be difficult to demodulate correctly, it will not significantly affect the overall trend of the envelope. The influence of polarization on the envelope corresponding to Equation (1) is similar to the variation law of the sine curve. It is most likely to appear at the extreme value of the envelope change, while the trend of the envelope change at the polarization fading point is often the smallest. The range within the subgroup is a quantity that reflects the degree of data change. Normally, data outside the action limit or outside the boundary is considered to be abnormal data. When points appear outside the boundary, it is considered that the data reaction process is not in a steady state. However, the specific value of the action limit is defined by humans, that is, the value of the action limit can be adjusted. The so-called steady state is conditional and relative. After introducing the control chart into the processing of Φ-OTDR raw data, the Φ-OTDR raw data along the fiber length direction does not focus on whether its distribution along the fiber length direction is in a steady state, but only on how to avoid the fiber sampling position where the fading point is located. If we think about it this way, we can try to think about it from the opposite perspective. Points outside the control chart's action limits are likely to correspond to extreme values ​​of the envelope or be close to extreme values ​​of the envelope. The fiber sampling positions corresponding to these points must be far away from polarization fading, and the sampled signals at these positions naturally have a high signal-to-noise ratio due to their high intensity values. Using these positions as reference points will inevitably yield good phase signal demodulation results. Therefore, using the accumulation method can avoid the fiber sampling positions corresponding to polarization fading points.

[0035] The solutions mentioned in this application are all results obtained by the inventors after practice and careful research. Therefore, the discovery process of the above problems and the solutions proposed in this disclosure below should be considered as contributions made by the inventors to this disclosure.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0037] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0038] like Figures 1 to 8 As shown, at least one embodiment provides a method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data, comprising: Step S1: The Φ-OTDR hardware device acquires backscattered Rayleigh signals in chronological order and calibrates a two-dimensional array corresponding to each backscattered Rayleigh signal according to the emission order of the light pulses; Step S2: The Φ-OTDR hardware device groups the backscattered Rayleigh signals in each light pulse according to a set sample size to calculate the range of each group of backscattered Rayleigh signals, and then calculates the average range of the backscattered Rayleigh signals corresponding to each light pulse; Step S3: Φ- The OTDR hardware device calculates the action limit corresponding to each optical pulse based on the average range of the backscattered Rayleigh signal corresponding to each optical pulse and the proportionality coefficient; Step S4: The Φ-OTDR hardware device compares the range corresponding to each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to the optical pulse to output the corresponding comparison value, and adds the comparison values ​​of the same group number of each optical pulse to obtain the corresponding cumulative value; Step S5: When the cumulative value is greater than 0, the Φ-OTDR hardware device obtains the cumulative value and restores the corresponding one-dimensional array to determine the candidate region of the reference point for non-polarization fading.

[0039] Specifically, the detection structure of the phase optical time domain reflectometer (Φ-OTDR) in the Φ-OTDR hardware device is heterodyne detection. The back Rayleigh scattering light generated by the detection pulse light enters the balanced photodetector together with the reference light to form a back Rayleigh scattering signal.

[0040] In at least one embodiment, the detected raw backscattered Rayleigh signal is processed based on a range control map. Specifically, the detected raw Φ-OTDR data is first organized, then the raw Φ-OTDR data of each optical pulse is grouped and the range is calculated. The mean range and action limit are then calculated. The comparison value at the abrupt change is obtained based on the action limit. The comparison value is either 0 or 1. Then, the comparison values ​​at the same fiber sampling position corresponding to all optical pulses are added together. This makes it easy to obtain the non-polarization fading point region that can be used as a candidate reference point, thereby reducing the computational difficulty.

[0041] In at least one embodiment, the method of step S1 includes: the Φ-OTDR hardware device acquiring backscattered Rayleigh signals in chronological order, i.e., the Φ-OTDR raw data I. D ;Transfer one-dimensional Φ-OTDR raw data I D Convert to a two-dimensional array E(m,n); where m is the number of light pulses emitted, and the value of m is 1≤m≤M; n is the number of sampling points of the optical fiber, and the value of n is 1≤n≤N; M is the maximum number of light pulses emitted within the observation range; and N is the maximum number of sampling points of the optical fiber within the observation range.

[0042] Specifically, regardless of how the light pulse is emitted, the acquisition of the backscattered Rayleigh signal is performed sequentially over time, meaning the acquired raw signal is one-dimensional. The acquired Φ-OTDR raw data I is now presented. D The optical pulses are processed according to their emission order. The number of emission times is denoted as m, with a maximum of 1000. The number of sampling points on the optical fiber is denoted as n, with a maximum value of 10000. This process is used to process the acquired Φ-OTDR raw data I. D To convert it into a two-dimensional array E(m,n), please refer to [link / reference]. Figure 2 , Figure 2 This is a superimposed diagram of the backscattered Rayleigh signals corresponding to 1000 light pulses.

[0043] In at least one embodiment, the method of step S2 includes: for any number of optical pulses m x Let the sample size be D, so that the two-dimensional array E(m) can be... x Transform H(m,n) into H(m) x ,j,i)=E(m x (j-1)×D+i), where j is the group number of the backscattered Rayleigh signals in this light pulse after being grouped according to a set sample size, i is the index of a single backscattered Rayleigh signal value in each group, and the value of i ranges from 1 to i to D, while the minimum value of j is 1, the remainder of N divided by D is R, and the maximum value of j is (NR) / D; the range of any group of backscattered Rayleigh signals is HH(m x,j)=max{E(m x ,(j-1)×D+1),…,E(m x ,j×D)}-min{E(m x ,(j-1)×D+1),…,E(m x ,j×D)}, where max and min are the maximum and minimum values ​​respectively; for any number of light pulses m x Calculate the average range of the backscattered Rayleigh signal corresponding to the light pulse.

[0044] Specifically, the range is calculated for the backscattered Rayleigh signal corresponding to each light pulse to reflect changes in data dispersion, effectively highlighting the effects of polarization and interference. A subgroup size of 5 (sample size D) is used, and the sample is divided into subgroups according to the natural number of sampling points. The range for each subgroup is then calculated; the range is the difference between the largest and smallest value within the subgroup, ensuring that all range values ​​are non-negative. Please refer to [link / reference]. Figure 3 , Figure 3 The range values ​​calculated for the backscattered Rayleigh signal corresponding to the first light pulse are shown.

[0045] Specifically, for the backscattered Rayleigh signal of each light pulse, after grouping according to a set sample size and calculating the range of each group, all range values ​​are summed and averaged to obtain the average range of the backscattered Rayleigh signal when the set sample size is 5. Please refer to [link to relevant documentation]. Figure 4 The average range of all light pulses is as follows: Figure 4 As shown.

[0046] In at least one embodiment, the method of step S3 includes: setting a proportionality coefficient as a, where a > 0; calculating the action limit corresponding to each light pulse.

[0047] Specifically, the three sigma control limits of the range control chart are directly proportional to the average range. Here, we adopt this relationship and set the proportionality coefficient 'a' to 2.114. The product of 2.114 and the average range is the action limit. The value of the proportionality coefficient can be flexibly adjusted according to the actual situation; a larger value means more information is eliminated, and vice versa. Please refer to [link / reference]. Figure 5 When the proportionality coefficient is 2.114, the action limit corresponding to each optical pulse is as follows: Figure 5 As shown.

[0048] In at least one embodiment, the method of step S4 includes: comparing the range corresponding to each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to the optical pulse; when the range corresponding to any group of backscattered Rayleigh signals in any optical pulse is greater than the action limit corresponding to the optical pulse, the output comparison value is 1; when the range corresponding to any group of backscattered Rayleigh signals in any optical pulse is less than or equal to the action limit corresponding to the optical pulse, the output comparison value is 0.

[0049] Specifically, please refer to Figure 6 Taking the first light pulse as an example, when the subgroup range is greater than the action limit, it is marked as 1; otherwise, it is marked as 0. Figure 6 As shown.

[0050] In at least one embodiment, the method of step S4 further includes: in any light pulse m x The comparison value output at group number j is And m x It is any value of m; the sum of the comparison values ​​of the same group number of each optical pulse is used to obtain the corresponding cumulative value. And j x It is any value that belongs to j.

[0051] Specifically, due to factors such as pulse modulation jitter and noise, the range of a single optical pulse cannot accurately reflect the polarization fading point. Therefore, the ranges corresponding to each optical pulse are summed with the action limit by subgroup number. Please refer to [link to relevant documentation]. Figure 7 The result of adding them is as follows Figure 7 As shown, the result of the addition is named the cumulative value.

[0052] In at least one embodiment, the method of step S5 includes: when U(j x When ) is greater than 0, obtain the corresponding j. x The value of n, and n x =j x ×D, and n x If it is any value of n, then determine [n] x -D+1,n x [ ] represents the candidate region for reference points in non-polarization fading. The corresponding phase information can be demodulated based on the reference point selected in this region.

[0053] Specifically, in order to correspond with the sequence numbers of the original records, the horizontal array of the accumulated values ​​is magnified according to the set sample size, and the result is as follows: Figure 8 As shown in (a). For ease of comparison, in Figure 8 (b) shows the modulus. The modulus is the result obtained by orthogonal demodulation followed by square root operation. Figure 8(b) The results on both sides of the mid-magnitude value differ significantly from other values ​​because they are calculated based on the detector and system noise floor. On the left, the difference in trigger signal and system delays prevent backscattered Rayleigh light from entering the detector. On the right, the limited fiber length naturally results in no backscattered Rayleigh light being generated. (Comparison) Figure 2 , Figure 3 and Figure 8 (b) It can be found on the left and right sides of the three. Figure 8 (b) It can more clearly display information about the backscattered Rayleigh light. Similarly, the fiber sampling location with a modulus of 0 or close to 0 indicates the location of the polarization fading point. Figure 8 (a) and Figure 8 (b) It can be observed that the accumulated value at the fiber sampling position where the polarization fading point is located is 0. Therefore, when the reference point is selected at the fiber sampling position with a higher accumulated value, the polarization fading point is naturally avoided.

[0054] In at least one embodiment, Φ-OTDR raw data I D The spatial length corresponding to the uniform sampling interval is D_sample. When the Φ-OTDR hardware device detects heterodyne, the spatial length corresponding to a single cycle of the difference frequency is greater than ten times D_sample.

[0055] In one alternative implementation, the light source frequency fluctuation of the Φ-OTDR hardware device is less than 50kHz.

[0056] Specifically, the smaller the value of the proportionality coefficient 'a', the better it reflects the distribution of fading points at each sampling position of the optical fiber. At the same time, the maximum value of 'a' should ensure that the accumulated value at the sampling position of the optical fiber before the disturbance event has a peak value.

[0057] Based on the same technological concept, such as Figures 1 to 8As shown, at least one embodiment also provides a system employing the above-described method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data, comprising: a Φ-OTDR hardware device; wherein the Φ-OTDR hardware device acquires backscattered Rayleigh signals in chronological order and calibrates a two-dimensional array corresponding to each backscattered Rayleigh signal according to the emission order of the light pulses; the Φ-OTDR hardware device groups the backscattered Rayleigh signals in each light pulse according to a set sample size to calculate the range of each group of backscattered Rayleigh signals, and then calculates the backscattered Rayleigh signal corresponding to each light pulse. The Φ-OTDR hardware device calculates the action limit corresponding to each optical pulse based on the average range of the backscattered Rayleigh signal corresponding to each optical pulse and the proportionality coefficient. The Φ-OTDR hardware device compares the range corresponding to each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to that optical pulse to output the corresponding comparison value, and adds the comparison values ​​of the same group number of each optical pulse to obtain the corresponding cumulative value. When the cumulative value is greater than 0, the Φ-OTDR hardware device obtains the cumulative value and restores the corresponding one-dimensional array to determine the candidate region of the reference point for non-polarization fading.

[0058] In summary, this invention processes the detected raw backscattered Rayleigh signal based on a range control map. First, the detected raw Φ-OTDR data is organized. Then, the raw Φ-OTDR data for each optical pulse is grouped and the range is calculated. The mean range and action limit are then calculated. Based on the action limit, a comparison value is obtained at the point of abrupt change. The comparison value is either 0 or 1. Finally, the comparison values ​​at the same fiber sampling position corresponding to all optical pulses are added together. This easily yields the non-polarization fading point region that can serve as a candidate reference point, thus reducing computational complexity.

[0059] The disclosures and other solutions, examples, embodiments, modules, and functional operations described in this document can be implemented in digital electronic circuits, or computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents, or combinations thereof. The disclosures and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a tangible and non-volatile computer-readable medium for execution by a data processing apparatus or for controlling the operation of the data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a storage device, a material composition that influences machine-readable propagated signals, or one or more of these. The terms "data processing unit" or "data processing apparatus" include all means, devices, and machines for processing data, including, for example, programmable processors, computers, or multiprocessors or computer groups. In addition to hardware, the apparatus may also include code that creates an execution environment for a computer program, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or combinations thereof. The propagated signals are artificially generated signals, such as machine-generated electrical, optical, or electromagnetic signals, which are generated to encode information for transmission to a suitable receiver device.

[0060] Computer programs (also known as programs, software, software applications, scripts, or code) can be written in any programming language (including compiled or interpreted languages) and can be deployed in any form, including as standalone programs or as modules, components, subroutines, or other units suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to that program, or in multiple coordinating files (e.g., a file storing one or more modules, subroutines, or portions of code). Computer programs can be deployed and executed on one or more computers located at a single site or distributed across multiple sites interconnected by a communication network.

[0061] The processing and logic flows described in this document can be executed by one or more programmable processors that execute one or more computer programs to perform functions by manipulating input data and generating outputs. The processing and logic flows can also be executed by special-purpose logic circuitry, and the devices can be implemented as special-purpose logic circuitry, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits).

[0062] For example, processors suitable for executing computer programs include general-purpose and special-purpose microprocessors, as well as any one or more of any type of digital computer. Typically, the processor receives instructions and data from read-only memory or random access memory, or both. The basic components of a computer are a processor that executes instructions and one or more storage devices that store the instructions and data. Typically, a computer will also include one or more mass storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks, or operatively coupled to receive data from or transfer data to mass storage devices, or both. However, a computer does not necessarily have such devices. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including, for example, semiconductor memory devices such as erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and optical disc read-only memory (CD ROM) and digital versatile optical disc read-only memory (DVD-ROM). The processor and memory may be supplemented by dedicated logic circuitry or incorporated into dedicated logic circuitry.

[0063] While this patent document contains numerous details, it should not be construed as limiting the scope of any invention or claim, but rather as a description of features of specific embodiments of a particular invention. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various functions described in the context of a single embodiment may also be implemented individually in multiple embodiments, or in any suitable sub-combination. Furthermore, although the foregoing features may be described as functioning in certain combinations, or even initially claimed to be so, in certain circumstances, one or more features from a combination of claims may be removed from the combination, and a combination of claims may refer to a sub-combination or a variation of a sub-combination.

[0064] Similarly, although the operations are described in a specific order in the accompanying drawings, this should not be construed as requiring the specific order or sequence shown to perform such operations, or all the described operations, in order to obtain the desired result. Furthermore, the separation of various system components in the embodiments of this patent document should not be construed as requiring such separation in all embodiments.

[0065] Only some implementations and examples are described; other implementations, enhancements, and variations can be made based on the content described and illustrated in this patent document.

[0066] When no intermediate component exists other than a line, trace, or other medium between the first and second components, the first component is directly coupled to the second component. When an intermediate component other than a line, trace, or other medium exists between the first and second components, the first component is indirectly coupled to the second component. The term "coupling" and its variations include direct coupling and indirect coupling. Unless otherwise stated, the term "about" is used to mean a range including upper and lower 10% of the value.

[0067] While several embodiments are provided in this disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of this disclosure. The present examples are intended to be illustrative rather than restrictive and are not limited to the details given. For example, various elements or components may be combined or integrated into another system, or certain features may be omitted or not implemented.

[0068] In the several embodiments provided herein, it should be understood that the disclosed apparatus and methods can also be implemented in other ways. The apparatus embodiments described above are merely illustrative; for example, the flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than those marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in block diagrams and / or flowcharts, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.

[0069] Furthermore, without departing from the scope of this disclosure, the discrete or individual technologies, systems, subsystems, and methods described and illustrated in the various embodiments may be combined or integrated with other systems, modules, technologies, or methods. Other items shown or discussed as coupled may be directly connected or indirectly coupled or communicated via some interface, device, or intermediate component in an electrical, mechanical, or other manner. Those skilled in the art can identify other examples of changes, substitutions, and modifications without departing from the spirit and scope of this disclosure.

Claims

1. A method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data, characterized in that, include: Step S1: The Φ-OTDR hardware device acquires backscattered Rayleigh signals in chronological order and calibrates the two-dimensional array corresponding to each backscattered Rayleigh signal according to the emission order of the light pulses; Step S2: The Φ-OTDR hardware device groups the backscattered Rayleigh signals in each optical pulse according to a set sample size, calculates the range of each group of backscattered Rayleigh signals, and then calculates the average range of the backscattered Rayleigh signals corresponding to each optical pulse. Step S3: The Φ-OTDR hardware device calculates the action limit corresponding to each optical pulse based on the average range of the backscattered Rayleigh signal corresponding to each optical pulse and the proportionality coefficient; Step S4: The Φ-OTDR hardware device compares the range corresponding to each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to the optical pulse to output the corresponding comparison value, and adds the comparison values ​​of the same group number of each optical pulse to obtain the corresponding cumulative value. Step S5: When the accumulated value is greater than 0, the Φ-OTDR hardware device obtains the accumulated value and restores the corresponding one-dimensional array to determine the candidate region of the reference point for non-polarization fading.

2. The method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in claim 1, characterized in that, The method in step S1 includes: The Φ-OTDR hardware acquires backscattered Rayleigh signals in chronological order, i.e., the Φ-OTDR raw data I. D ; One-dimensional Φ-OTDR raw data I D Convert to a two-dimensional array E(m,n); where m is the number of light pulses emitted, and the value of m is in the range of 1≤m≤M. n is the number of sampling points in the optical fiber, and the value of n is in the range of 1≤n≤N. M is the maximum number of light pulses emitted within the observation range, and N is the maximum number of sampling points in the optical fiber within the observation range.

3. The method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in claim 2, characterized in that, The method in step S2 includes: For any light pulse m x Let the sample size be D, so that the two-dimensional array E(m) can be... x Transform H(m,n) into H(m) x ,j,i)=E(m x ,(j-1)×D+i), j is the group number of the back Rayleigh scattering signal in this light pulse after grouping according to the set sample size, i is the index of the individual back Rayleigh scattering signal value in each group of back Rayleigh scattering signals, and the value range of i is 1≤i≤D, while the minimum value of j is 1, the result of the remainder of N divided by D is R, and the maximum value of j is (NR) / D; The range of any set of backscattered Rayleigh signals is HH(m) x ,j)=max{E(m x ,(j-1)×D+1),…,E(m x ,j×D)}-min{E(m x ,(j-1)×D+1),…,E(m x ,j×D)}, where max and min are the maximum and minimum value operations, respectively; For any light pulse m x Calculate the average range of the backscattered Rayleigh signal corresponding to the light pulse.

4. The method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in claim 3, characterized in that, The method in step S3 includes: Let the proportionality coefficient be a, and a > 0; Calculate the action limit corresponding to each light pulse as follows:

5. The method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in claim 4, characterized in that, The method in step S4 includes: Compare the range of each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to that optical pulse; The output comparison value is 1 when the range of any group of backscattered Rayleigh signals in any light pulse is greater than the action limit of the light pulse; the output comparison value is 0 when the range of any group of backscattered Rayleigh signals in any light pulse is less than or equal to the action limit of the light pulse.

6. The method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in claim 5, characterized in that, The method in step S4 further includes: In any light pulse m x The comparison value output at group number j is And m x It is any value that belongs to m; The comparison values ​​of the same group number of each optical pulse are added together to obtain the corresponding cumulative value. And j x It is any value that belongs to j.

7. The method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in claim 6, characterized in that, The method in step S5 includes: When U(j x When ) is greater than 0, obtain the corresponding j. x The value of n, and n x =j x ×D, and n x If it is any value of n, then determine [n] x -D+1,n x [ ] represents the candidate region for the reference point of non-polarization fading.

8. The method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in claim 2, characterized in that, Φ-OTDR raw data I D The spatial length corresponding to the uniform sampling interval is D_sample. When the Φ-OTDR hardware device detects heterodyne, the spatial length corresponding to a single cycle of the difference frequency is greater than ten times D_sample.

9. The method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in claim 1, characterized in that, The light source frequency fluctuation of the Φ-OTDR hardware device is less than 50kHz.

10. A system employing the method for avoiding polarization fading points based on range control charts and Φ-OTDR raw data as described in any one of claims 1-9, characterized in that, include: Φ-OTDR hardware; in The Φ-OTDR hardware device acquires backscattered Rayleigh signals in chronological order and calibrates the two-dimensional array corresponding to each backscattered Rayleigh signal according to the emission order of the light pulses. The Φ-OTDR hardware device groups the backscattered Rayleigh signals in each optical pulse according to a set sample size, calculates the range of each group of backscattered Rayleigh signals, and then calculates the average range of the backscattered Rayleigh signals corresponding to each optical pulse. The Φ-OTDR hardware device calculates the action limit corresponding to each optical pulse based on the average range of the backscattered Rayleigh signal corresponding to each optical pulse and the proportionality coefficient. The Φ-OTDR hardware device compares the range corresponding to each group of backscattered Rayleigh signals in each optical pulse with the action limit corresponding to the optical pulse to output the corresponding comparison value, and adds the comparison values ​​of the same group number of each optical pulse to obtain the corresponding cumulative value. When the accumulated value is greater than 0, the Φ-OTDR hardware device obtains the accumulated value and restores the corresponding one-dimensional array to determine the candidate region of the reference point for non-polarization fading.

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