A method and device for demodulating the arctangent phase of an optical intensity signal

Abstract

This invention relates to an arctangent phase demodulation method and apparatus for optical intensity signals. The method includes: acquiring three initial optical intensity signals output from a three-terminal coupler; performing consistency adjustment on the three initial optical intensity signals to obtain three target optical intensity signals; processing the three target optical intensity signals based on an arctangent demodulation algorithm to obtain an initial phase signal; obtaining an actual phase signal based on the initial phase signal using a secondary unwinding method; acquiring the phase signal in a non-vibration region to obtain a reference phase signal; and obtaining the phase signal to be measured based on the actual phase signal and the reference phase signal to complete the vibration detection of the vibration signal in the vibration region. This application proposes a three-port demodulation scheme based on an arctangent algorithm, which compensates for the inconsistency of the three optical intensities through dynamic proportional adjustment; and uses the reference phase signal in the non-vibration section as a reference value to eliminate baseline drift caused by data accumulation.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, and in particular to an arctangent phase demodulation method and demodulation device for optical intensity signals. Background Technology

[0002] Phase-sensitive optical time-domain reflectometry (φ-OTDR) is a distributed fiber optic vibration sensing technology characterized by fast response, long transmission distance, and high sensitivity. It shows great application potential in areas such as perimeter intrusion monitoring, oilfield pipeline leak detection, and geological disaster monitoring and early warning. φ-OTDR uses a narrow-linewidth laser as its light source. When the sensing fiber is subjected to external disturbance, the local refractive index at the disturbance location is modulated, causing a phase change in the echo-backscattered Rayleigh (RBS) light at that location. The phase demodulation algorithm based on φ-OTDR detects and analyzes this change to obtain the signal of the external disturbance, thus achieving vibration detection.

[0003] Existing phase demodulation methods mainly include the following two approaches: The first approach involves directly obtaining two AC optical signals through optical path processing, then summing and subtracting the two signals to obtain two orthogonal signals, and finally demodulating the phase signal through orthogonal demodulation. However, this approach does not consider the inconsistency of the three outputs of a 3*3 coupler, which easily introduces phase errors into the demodulated phase signal. The second approach utilizes a coherent detection structure that interferes with the intrinsic light and the backscattered Rayleigh light. After photoelectric conversion, signal mixing, and filtering, the two orthogonal beams are subjected to differential cross-multiplication and subtraction operations to obtain the phase signal of the sensing optical signal. However, since the accuracy of the calculus algorithm depends on the acquisition frequency, and the integration process easily introduces baseline drift, the demodulated phase signal is significantly affected by noise.

[0004] Therefore, there is a need to provide an arctangent phase demodulation method that can guarantee the consistency of the three light intensities, effectively eliminate baseline drift caused by data accumulation, and has a simple algorithm to solve the above technical problems. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an arctangent phase demodulation method for optical intensity signals. This method solves the problem that existing phase demodulation methods do not consider the inconsistencies of the three outputs of a 3x3 coupler, leading to phase errors in the demodulated phase signal or baseline drift introduced by calculus algorithms, resulting in noise affecting the demodulated phase signal.

[0006] The technical effects of this invention are achieved through the following:

[0007] An arctangent phase demodulation method for light intensity signals includes:

[0008] Acquire three initial light intensity signals output from the three-terminal coupler. The three initial light intensity signals include the phase signal to be measured within the vibration region.

[0009] After performing consistency adjustment on the three initial light intensity signals, three target light intensity signals are obtained.

[0010] The initial phase signal is obtained by processing the three target light intensity signals based on the arctangent demodulation algorithm;

[0011] The actual phase signal is obtained by a secondary unwinding method based on the initial phase signal.

[0012] The phase signal in the non-vibration region is acquired to obtain the reference phase signal;

[0013] The phase signal to be measured is obtained based on the actual phase signal and the reference phase signal to complete the vibration detection of the vibration signal in the vibration region.

[0014] Furthermore, after performing consistency adjustment on the three initial light intensity signals, three target light intensity signals are obtained, including:

[0015] One of the three initial light intensity signals is selected as the calibration light intensity signal;

[0016] Based on the calibration light intensity signal, the light intensity difference coefficients corresponding to the three initial light intensity signals are calculated respectively to obtain the three target light intensity signals after consistency adjustment.

[0017] Furthermore, after performing consistency adjustment on the three initial light intensity signals, three target light intensity signals are obtained, which includes:

[0018] The initial light intensity signals of the three channels are simplified to obtain the light intensity expression corresponding to each initial light intensity signal, so as to update the initial light intensity signal.

[0019] Furthermore, the light intensity expression represents the light intensity signal at different times. The parameters of the light intensity expression include the average value of the output light intensity at different detection positions within the vibration region and the AC coefficient of the output light intensity at different detection positions within the vibration region. By selecting one of the three output initial light intensity signals as a calibration path, and performing consistency adjustment on the three initial light intensity signals based on the initial light intensity signal of the calibration path, the amplitude of the three initial light intensity signals after consistency adjustment is ensured to be balanced, the frequency is the same, and the phase difference between each pair of signals is 2π / 3, thus achieving real-time alignment of the three initial light intensity signals.

[0020] Furthermore, the initial phase signal is obtained by processing the three target light intensity signals based on the arctangent demodulation algorithm, including:

[0021] Based on the three target light intensity signals, construct sine and cosine terms with a tangent relationship;

[0022] The initial phase signal is obtained by performing arctangent calculation on the sine and cosine terms based on the arctangent demodulation algorithm.

[0023] Further, the actual phase signal is obtained from the initial phase signal using a secondary unwinding method, including:

[0024] The initial phase signal is subjected to first-order differential processing to obtain the corresponding first-order differential signal;

[0025] The actual phase signal is obtained by unwinding the first-order differential signal.

[0026] Further, the first-order differential signal is unwound to obtain the actual phase signal, including:

[0027] Determine whether the first-order differential signal is greater than or equal to -π and less than or equal to π;

[0028] If so, the first-order differential signal is taken as the actual phase signal;

[0029] If not, when the first-order differential signal is greater than π, the actual phase signal is obtained by subtracting the first-order differential signal from 2π; when the first-order differential signal is less than -π, the actual phase signal is obtained by summing the first-order differential signal from 2π. Traditional unwinding methods are accurate when the actual change in the true value is within a certain range; however, when the actual jump in the true value is greater than this range, it may be misjudged as a wound value due to unwinding, introducing errors. Therefore, this application proposes a secondary unwinding method. After obtaining the initial phase signal by performing arctangent calculation on the sine and cosine terms using the arctangent demodulation algorithm, an unwinding operation is then performed based on the first-order differential data of the initial phase signal. The result of the secondary unwinding is used as the actual unwinding result, thereby expanding the dynamic range of phase change and restoring the actual phase signal.

[0030] Further, the phase signal in the non-vibration region is acquired to obtain a reference phase signal, including:

[0031] Acquire phase signals from several consecutive acquisition cycles during vibration detection within a non-vibration area;

[0032] The corresponding phase difference signal is obtained from the phase signals of the several consecutive acquisition cycles in the non-vibration area, and is used as a reference phase signal.

[0033] Further, obtaining the phase signal to be measured based on the actual phase signal and the reference phase signal includes:

[0034] Obtain the actual phase signals of all detection positions within the vibration region at any given time;

[0035] The final phase signal is obtained by subtracting the reference phase signal from the actual phase signal corresponding to all detection positions, and the phase signal to be measured is calculated. By introducing the differential signal from the non-vibration region as a reference value, the inherent drift between periodic data is eliminated, and the degree of restoration of the phase signal to be measured is improved.

[0036] Additionally, an arctangent phase demodulation device for light intensity signals is also provided, comprising:

[0037] Light intensity signal acquisition module: used to acquire three initial light intensity signals output by the three-terminal coupler, the three initial light intensity signals including the phase signal to be measured in the vibration region;

[0038] Consistency adjustment module: used to perform consistency adjustment on the three initial light intensity signals to obtain three target light intensity signals;

[0039] Arctangent demodulation module: used to process the three target light intensity signals based on the arctangent demodulation algorithm to obtain the initial phase signal;

[0040] Secondary unwinding module: used to obtain the actual phase signal based on the initial phase signal using a secondary unwinding method;

[0041] Reference phase acquisition module: used to acquire the phase signal in the non-vibration region to obtain the reference phase signal;

[0042] Phase signal acquisition module: used to obtain the phase signal to be measured based on the actual phase signal and the reference phase signal, so as to complete the vibration detection of the vibration signal in the vibration area.

[0043] As described above, the present invention has the following beneficial effects:

[0044] 1) By selecting one of the three output initial light intensity signals as the calibration path, and adjusting the three initial light intensity signals based on the initial light intensity signal of the calibration path, the amplitude of the three initial light intensity signals after the consistency adjustment is balanced, the frequency is the same, and the phase difference between each pair is 2π / 3, thus realizing the real-time alignment of the three initial light intensity signals.

[0045] 2) A secondary unwinding method is proposed, which allows the initial phase signal to be obtained by calculating the arctangent of the sine and cosine terms using the arctangent demodulation algorithm, and then the unwinding operation is performed based on the first-order differential data of the initial phase signal so that the result of the secondary unwinding is used as the result of the actual unwinding, thereby expanding the dynamic range of phase change and restoring the actual phase signal.

[0046] 3) By introducing the differential signal from the non-vibration region as a reference value, the inherent drift between periodic data is eliminated, and the degree of restoration of the phase signal under test is improved. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the present invention, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0048] Figure 1 A flowchart illustrating an arctangent phase demodulation method for an optical intensity signal provided in this specification embodiment;

[0049] Figure 2 A schematic diagram of an optical fiber containing vibration information provided in an embodiment of this specification;

[0050] Figure 3 This is a structural block diagram of an arctangent phase demodulation device for an optical intensity signal provided in an embodiment of this specification. Detailed Implementation

[0051] The technical solutions of the embodiments 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, and 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.

[0052] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0053] Example 1:

[0054] like Figure 1 As shown in the embodiments of this specification, an arctangent phase demodulation method for light intensity signals is provided, including:

[0055] S100: Acquire the three initial light intensity signals output by the three-terminal coupler. The three initial light intensity signals include the phase signal to be measured in the vibration region.

[0056] S200: After performing consistency adjustment on the three initial light intensity signals, three target light intensity signals are obtained;

[0057] In one specific implementation, step S200 involves performing consistency adjustment on the three initial light intensity signals to obtain three target light intensity signals, prior to which the following steps are included:

[0058] The initial light intensity signals of the three channels are simplified to obtain the light intensity expression corresponding to each initial light intensity signal, so as to update the initial light intensity signal.

[0059] The light intensity expression refers to the light intensity signal at a specific location at different times t, where different times t refer to the periodic sampling times for the same location. The parameters of the light intensity expression include the average value of the output light intensity at different detection positions within the vibration region and the AC coefficient of the output light intensity at different detection positions within the vibration region.

[0060] In one specific implementation, step S200 involves adjusting the consistency of the three initial light intensity signals to obtain three target light intensity signals, including:

[0061] One of the three initial light intensity signals is selected as the calibration light intensity signal;

[0062] Based on the calibration light intensity signal, the light intensity difference coefficients corresponding to the three initial light intensity signals are calculated respectively to obtain the three target light intensity signals after consistency adjustment.

[0063] It should be noted that the principle of the phase demodulation algorithm of the three-terminal coupled direct probe φ-OTDR architecture is as follows:

[0064] In the direct-probe φ-OTDR architecture based on three-terminal coupling, three-terminal coupling refers to an optical structure with a 3×3 coupler at its core. This structure ensures that after the light intensity signal passes through the three ports, due to the optical characteristics of the coupler itself, it can output three initial light intensity signals with the same frequency and a phase difference of 2π / 3 between each pair of signals.

[0065] After the initial light intensity signals from these three outputs pass through the photodetector, their light intensity expression can be simplified to the following form:

[0066]

[0067] Where k is the sequence number of the three optical signals; p is a different position point on the optical fiber, representing various positions from the head to the tail of the optical fiber. Let be the initial light intensity signal output from the k-th channel at position p; Let be the average value of the k-th output light intensity at position p; Let be the AC coefficient of the output light intensity of the k-th path at position p; The phase signal to be measured is extracted using a phase demodulation algorithm.

[0068] In theory, However, due to the differences in photodetectors and the independence of the three optical paths during transmission, fluctuations occur between the three initial light intensity signals. Therefore, after acquiring the three initial light intensity signals, it is necessary to perform consistency adjustments to update the initial light intensity signals and ensure that the data is aligned in real time.

[0069] Therefore, in this embodiment, the specific operation of consistency adjustment is as follows:

[0070] 1) Select the first initial light intensity signal as the calibration path, and calculate the light intensity difference coefficients between the three initial light intensity signals and the first initial light intensity signal in turn, denoted as ρ1, ρ2, and ρ3 respectively. The calculation method is as follows:

[0071]

[0072] 2) Calculate separately The three initial light intensity signals after consistency adjustment are expressed as follows:

[0073]

[0074] in, This represents the three initial light intensity signals after consistency adjustment. These represent the average output light intensity of the k-th channel at position p and the AC coefficient, respectively.

[0075] S300: The initial phase signal is obtained by processing the three target light intensity signals based on the arctangent demodulation algorithm;

[0076] In one specific implementation, step S300 processes the three target light intensity signals based on the arctangent demodulation algorithm to obtain an initial phase signal, including:

[0077] Based on the three target light intensity signals, construct sine and cosine terms with a tangent relationship;

[0078] The initial phase signal is obtained by performing arctangent calculation on the sine and cosine terms based on the arctangent demodulation algorithm.

[0079] Specifically, the initial phase signal can be calculated by demodulating the three light intensity data (i.e., the three initial light intensity signals) after consistency adjustment using the relationship between the sine and cosine formulas. This application employs an arctangent demodulation algorithm, which is simple to operate and does not require complex calculus circuits to solve for the initial phase signal. The calculation process is as follows:

[0080] 1) Constructing the sine term

[0081] 2) Constructing the cosine term

[0082] 3) After the sine and cosine terms are constructed, the initial phase information is obtained by using their tangent relationship as follows:

[0083]

[0084] S400: The actual phase signal is obtained by a secondary unwinding method based on the initial phase signal;

[0085] In one specific implementation, step S400 obtains the actual phase signal based on the initial phase signal using a secondary unwinding method, including:

[0086] The initial phase signal is subjected to first-order differential processing to obtain the corresponding first-order differential signal;

[0087] The actual phase signal is obtained by unwinding the first-order differential signal.

[0088] In one specific implementation, unwinding the first-order differential signal to obtain the actual phase signal includes:

[0089] Determine whether the first-order differential signal is greater than or equal to -π and less than or equal to π;

[0090] If so, the first-order differential signal is taken as the actual phase signal;

[0091] If not, when the first-order differential signal is greater than π, the actual phase signal is obtained by subtracting the first-order differential signal from 2π; when the first-order differential signal is less than -π, the actual phase signal is obtained by summing the first-order differential signal from 2π.

[0092] It should be noted that after arctangent calculation, the initial phase signal The phase value falls within the range of (-π, π). The principle behind arctangent calculation is as follows: when the actual phase value exceeds this range, phase entanglement occurs. That is, the actual phase value is added to or subtracted by several 2π values ​​to ensure that the calculated value always falls within (-π, π), which may result in inconsistencies between the initial phase signal and the actual phase value. Therefore, the result of the arctangent algorithm needs to be untangled to restore the actual phase.

[0093] The classic unwinding method is as follows: when the absolute value of the difference between consecutive elements of phase data is greater than π, ±2π is taken as its true value. Here, consecutive elements of phase data refer to the phase at the current moment and the phase at the next moment. That is, when the phase at the next moment minus the phase at the current moment is less than -π, then the phase at the next moment is added to 2π to obtain the actual phase value at the next moment; when the phase at the next moment minus the phase at the current moment is greater than π, then the phase at the next moment is subtracted from 2π to obtain the actual phase value at the next moment.

[0094] This processing method is only accurate when the actual change of the true value, that is, the change of the difference between consecutive elements of the phase data, is within the range of (-π, π). When the absolute value of the actual change of the true value is greater than or equal to π, it will introduce errors because it will be misjudged as a tangled value and untangled.

[0095] Therefore, this application proposes a method using an initial phase signal. First-order differential data Perform the unwinding operation. The result after unwinding is The actual unwinding result is denoted as The specific steps are as follows:

[0096] Solve Then, perform a first-order differential, i.e., a first-order difference, to obtain the first-order differential signal.

[0097] For first-order differential signals Perform unwinding operation: when the difference between consecutive elements is greater than π (or less than -π), take +2π (or -2π) as its true value and record it as the actual phase signal. This is done to complete the unwinding process and obtain an accurate actual phase signal.

[0098] By proposing the secondary unwinding method in this application, after obtaining the initial phase signal by performing arctangent calculation on the sine and cosine terms using the arctangent demodulation algorithm, the unwinding operation is then performed based on the first-order differential data of the initial phase signal to use the result of the secondary unwinding as the actual unwinding result, thereby expanding the dynamic range of phase change and restoring the actual phase signal.

[0099] S500: Acquire the phase signal in the non-vibration region to obtain the reference phase signal;

[0100] In one specific implementation, step S500 acquires the phase signal within the non-vibration region to obtain a reference phase signal, including:

[0101] Acquire phase signals from several consecutive acquisition cycles during vibration detection within a non-vibration area;

[0102] The corresponding phase difference signal is obtained from the phase signals of the several consecutive acquisition cycles in the non-vibration area, and is used as a reference phase signal.

[0103] S600: The phase signal to be measured is obtained based on the actual phase signal and the reference phase signal to complete the vibration detection of the vibration signal in the vibration area.

[0104] In one specific implementation, obtaining the phase signal to be measured based on the actual phase signal and the reference phase signal includes:

[0105] Obtain the actual phase signals of all detection positions within the vibration region at any given time;

[0106] The final phase signal is obtained by subtracting the reference phase signal from the actual phase signal corresponding to all detection positions, and the phase signal to be measured is calculated.

[0107] It should be noted that since Φ-OTDR uses a narrow-linewidth laser as its light source, and lasers have inherent drift, the demodulated phase result is prone to drift over time during the calculation process, which is equivalent to introducing an additional time-varying error. Based on this consideration, this application uses the differential signal from the non-vibration region as a reference value to eliminate the inherent drift of the periodic data. The specific operation method is as follows.

[0108] like Figure 2 As shown, this embodiment simplifies the vibration region and the non-vibration region into vibration segments and non-vibration segments, using a schematic diagram of an optical fiber containing vibration information as an example. The segment between positions A and B is the vibration segment, and the segment between positions C and D is the non-vibration segment.

[0109] The demodulated phase data between positions AB and CD are denoted as follows: Let the phase data at any time within a certain period be denoted as Among them, t i This represents the i-th time.

[0110] Then from time t1 to t T The phase data vector between moments, i.e., the phase signal of several consecutive acquisition cycles in the non-vibration region, can be expressed as:

[0111]

[0112] The phase difference signal obtained by calculating the phase difference of the non-vibrating segment CD over a period of time is as follows:

[0113]

[0114] Its meaning is: to calculate the difference between the phase data of the next moment and the phase data of the previous moment within the non-vibration segment CD.

[0115] Phase difference signal As a reference phase signal, the phase signal at any other location on the optical fiber is subtracted from this reference phase signal to obtain the final result. Taking the vibration segment AB as an example, let the final phase data obtained for segment AB be denoted as... Its calculation method is as follows

[0116]

[0117] By analogy, the demodulation result ψ(t) over the entire range is obtained, which is the final phase signal to be measured.

[0118] like Figure 3 As shown in the embodiments of this specification, an arctangent phase demodulation device for light intensity signals is also provided, comprising:

[0119] Light intensity signal acquisition module 301: used to acquire three initial light intensity signals output by the three-terminal coupler, wherein the three initial light intensity signals include the phase signal to be measured in the vibration region;

[0120] Consistency adjustment module 302: used to perform consistency adjustment on the three initial light intensity signals to obtain three target light intensity signals;

[0121] Arctangent demodulation module 303: used to process the three target light intensity signals based on the arctangent demodulation algorithm to obtain the initial phase signal;

[0122] Secondary unwinding module 304: used to obtain the actual phase signal based on the initial phase signal using a secondary unwinding method;

[0123] Reference phase acquisition module 305: used to acquire the phase signal in the non-vibration region to obtain the reference phase signal;

[0124] Phase signal acquisition module 306: used to obtain the phase signal to be measured based on the actual phase signal and the reference phase signal, so as to complete the vibration detection of the vibration signal in the vibration area.

[0125] While the present invention has been described through preferred embodiments, it is not limited to the embodiments described herein, and various changes and modifications are made without departing from the scope of the invention.

[0126] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0127] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. An arctangent phase demodulation method of optical intensity signals, applied to phase sensitive optical time domain reflectometry, characterized in that, The method comprises the following steps: obtaining three initial light intensity signals output by a three-terminal coupler, the three initial light intensity signals comprising a to-be-measured phase signal in a vibration region, the three initial light intensity signals being three initial light intensity signals with the same frequency and a phase difference of 2π / 3 between each other; selecting one of the three initial light intensity signals as a calibration light intensity signal; calculating light intensity difference coefficients corresponding to the three initial light intensity signals based on the calibration light intensity signal to obtain three target light intensity signals after consistency adjustment; processing the three target light intensity signals based on an inverse tangent demodulation algorithm to obtain an initial phase signal; performing first-order differential processing on the initial phase signal to obtain a first-order differential signal corresponding to the initial phase signal; performing unwinding operation on the first-order differential signal to obtain an actual phase signal; obtaining a phase signal in a non-vibration region to obtain a reference phase signal; obtaining the to-be-measured phase signal according to the actual phase signal and the reference phase signal to complete vibration detection of a vibration signal in the vibration region.

2. The arctangent phase demodulation method of an optical intensity signal according to claim 1, characterized in that, After consistency adjustment is performed on the three initial light intensity signals to obtain three target light intensity signals, the following step is performed: simplifying the three initial light intensity signals to obtain a light intensity expression corresponding to each of the initial light intensity signals, so as to update the initial light intensity signals.

3. The arctangent phase demodulation method of an optical intensity signal according to claim 2, characterized in that, The light intensity expression is a light intensity signal at different time points, and parameters of the light intensity expression include an average value of output light intensity at different detection positions in the vibration region and an alternating current coefficient of the output light intensity at the different detection positions in the vibration region.

4. The arctangent phase demodulation method of an optical intensity signal according to claim 3, characterized in that, The processing of the three target light intensity signals based on the inverse tangent demodulation algorithm to obtain an initial phase signal comprises the following steps: constructing a sine term signal and a cosine term signal having a tangent relationship according to the three target light intensity signals; performing inverse tangent calculation on the sine term signal and the cosine term signal based on the inverse tangent demodulation algorithm to obtain an initial phase signal.

5. The arctangent phase demodulation method of optical intensity signals according to claim 4, characterized in that, The unwinding operation is performed on the first-order differential signal to obtain an actual phase signal, comprising: judging whether the first-order differential signal is greater than or equal to π and less than or equal to π. If yes, the first-order differential signal is taken as an actual phase signal. If not, when the first-order differential signal is greater than π, the actual phase signal is obtained by subtracting 2π from the first-order differential signal; when the first-order differential signal is less than π, the actual phase signal is obtained by adding 2π to the first-order differential signal. π, the actual phase signal is obtained by subtracting 2π from the first-order differential signal; when the first-order differential signal is less than π, the actual phase signal is obtained by adding 2π to the first-order differential signal.

6. The arctangent phase demodulation method of optical intensity signals according to claim 5, characterized in that, The obtaining of a phase signal in a non-vibration region to obtain a reference phase signal comprises the following steps: obtaining phase signals in a non-vibration region in a plurality of continuous acquisition periods in a vibration detection process; obtaining a phase difference signal corresponding to the phase signals in the non-vibration region in the plurality of continuous acquisition periods as a reference phase signal.

7. The arctangent phase demodulation method of an optical intensity signal according to claim 6, characterized in that, The obtaining of the to-be-measured phase signal according to the actual phase signal and the reference phase signal comprises the following steps: obtaining actual phase signals of all detection positions in the vibration region at any time point; subtracting the actual phase signals of all detection positions from the reference phase signal to obtain a final phase signal to calculate the to-be-measured phase signal.

8. An arctangent phase demodulation apparatus for optical intensity signals for use in phase sensitive optical time domain reflectometry, characterized in that The method comprises the following steps: an intensity signal acquisition module: used for obtaining three initial light intensity signals output by a three-terminal coupler, the three initial light intensity signals comprising a to-be-measured phase signal in a vibration region, the three initial light intensity signals being three initial light intensity signals with the same frequency and a phase difference of 2π / 3 between each other; a calibration light intensity signal determination module: used for selecting one of the three initial light intensity signals as a calibration light intensity signal; The consistency adjustment module is configured to calculate light intensity difference coefficients corresponding to the three initial light intensity signals respectively based on the calibration light intensity signal, so as to obtain three target light intensity signals after consistency adjustment; The inverse tangent demodulation module is configured to process the three target light intensity signals based on an inverse tangent demodulation algorithm to obtain initial phase signals; The differential processing module is configured to perform first-order differential processing on the initial phase signals to obtain corresponding first-order differential signals; The secondary unwinding module is configured to perform unwinding operation on the first-order differential signals to obtain actual phase signals; The reference phase obtaining module is configured to obtain phase signals in a non-vibration region to obtain a reference phase signal; The phase signal obtaining module is configured to obtain the to-be-measured phase signal according to the actual phase signals and the reference phase signal, so as to complete vibration detection of the vibration signals in the vibration region.

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