Pipeline leakage detection device and method based on miniature point type optical fiber probe

Abstract

The invention belongs to the technical field of safety monitoring of heat distribution pipelines, and particularly provides a pipeline leakage detection device and method based on a miniature point type optical fiber probe. The pipeline leakage detection device based on the miniature point type optical fiber probe comprises a DAS demodulator and a detection device, the detection device comprises a first transmission optical cable and a second transmission optical cable, the starting ends of the first transmission optical cable and the second transmission optical cable are connected to the DAS demodulator, and the tail ends of the first transmission optical cable and the second transmission optical cable are provided with a first probe and a second probe respectively. The first probe and the second probe are fixedly connected to the outer side of a to-be-detected pipeline; the DAS demodulator is used for calculating the time difference of the vibration signals transmitted from the leakage point to the first probe and the second probe based on the vibration signals transmitted back by the first probe and the second probe, and calculating the position of the leakage point based on the time difference. The method is very flexible in arrangement, can be quickly deployed at the key points of the pipeline, and has very high detection sensitivity to high-frequency vibration generated by tiny leakage, so that high-precision positioning is performed on the leakage of the deeply-buried heat distribution pipeline.

Description

Technical Field

[0001] This invention belongs to the field of thermal pipeline safety monitoring technology, and particularly relates to a pipeline leakage detection device and method based on a miniature point fiber optic probe. Background Technology

[0002] Leak detection in urban underground heating pipelines is a crucial step in ensuring heating safety and conserving energy. Currently, mainstream leak detection methods have the following shortcomings: 1. Point sensors based on electrical principles (such as piezoelectric accelerometers and hydrophones): These sensors need to be installed at pipeline monitoring points (such as valve wells). Each sensor requires an independent power supply and signal transmission line, making the system complex and costly. Their sensitivity is limited, they are slow to respond to minor leaks, and they are susceptible to electromagnetic interference in the field, exhibiting poor long-term stability.

[0003] 2. Traditional Distributed Fiber Optic Acoustic Sensing (DAS) Technology: This technology uses optical fibers laid along the entire length of the pipeline as continuously distributed sensors, enabling long-distance monitoring. However, it has significant drawbacks: while optical fibers can be installed when laying new pipelines, it is no longer feasible for older pipelines in urban areas to lay optical fibers and implement real-time monitoring; for new pipelines, laying sensing optical fibers along the entire length is a large-scale and costly undertaking; secondly, the entire optical fiber is sensitive to vibration, and in the complex urban underground environment, background noise from traffic and construction can drown out weak leakage signals, resulting in a low signal-to-noise ratio, high false alarm rate, and difficulties in data analysis. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a pipeline leak detection device and method based on a miniature point fiber optic probe. It is extremely flexible in deployment and can be quickly deployed at key points of the pipeline (such as flanges and valve bodies). It also has extremely high detection sensitivity to high-frequency vibrations generated by minor leaks, enabling vibration measurement of the point probe at the end of the fiber optic cable, thereby achieving high-precision location of leaks in deeply buried thermal pipelines.

[0005] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: The first aspect of the present invention provides a pipeline leak detection device based on a miniature point fiber optic probe.

[0006] A pipeline leak detection device based on a miniature point fiber optic probe includes a DAS demodulator and at least one set of detection devices. The detection devices include a first transmission optical cable and a second transmission optical cable that are independently set. The beginnings of the first transmission optical cable and the second transmission optical cable are respectively connected to the DAS demodulator. The ends of the first transmission optical cable and the second transmission optical cable are respectively provided with a first probe and a second probe. The first probe and the second probe are fixedly connected to the outside of the pipeline to be detected. The DAS demodulator is used to calculate the time difference between the vibration signal propagating from the leak point to the first and second probes based on the vibration signals transmitted back from the first and second probes, and to calculate the location of the leak point based on the time difference.

[0007] As an alternative technical solution, the first probe and the second probe are used to detect the vibration signal of the pipeline to be tested.

[0008] As an alternative technical solution, the first probe and the second probe are centimeter-level fiber optic probes of a preset length, and the fiber optic probes are subjected to sensitivity enhancement treatment.

[0009] As an alternative technical solution, the first probe and the second probe are encapsulated and fixed inside a base or housing, the base having a magnetic attraction function, and the housing having a clamp connected to it.

[0010] As an optional technical solution, the DAS demodulator is also used to calibrate the position coordinates of the first and second probes before calculating the location of the leak point: After the first probe is installed, the background curve of the Rayleigh scattering signal corresponding to the first probe is first obtained by the DAS demodulator. Then, the pipe where the first probe is located is tapped. The vibration generated by the tapping is transmitted through the first probe and the first transmission optical cable to the DAS demodulator, generating a Rayleigh scattering signal due to the tapping. By comparing the Rayleigh scattering signal generated by the tap with the background curve, the point where the light intensity changes is located, and the distance coordinates corresponding to this point are marked as the position of the first probe, that is, the position of the first registration point. Similarly, the position of the second probe is calibrated to obtain the position of the second registration point.

[0011] As an optional technical solution, the DAS demodulator is also used to process only the fiber optic signals obtained from the first registration point location and the second registration point location after acquiring the first registration point location and the second registration point location.

[0012] As an optional technical solution, the DAS demodulator is used to calculate the time difference between the vibration signal propagating from the leak point to the first and second probes based on the vibration signals returned by the first and second probes, specifically: The stress wave generated by the pipeline leak propagates along the pipe wall and reaches the first and second probes in succession. The DAS demodulator simultaneously or time-divisionally queries two probes to acquire the phase change signals of the first registration point position and the second registration point position, denoted as S_A(t) and S_B(t). Filter S_A(t) and S_B(t); The time difference Δt between S_A(t) and S_B(t) after filtering is calculated using a cross-correlation algorithm.

[0013] As an alternative technical solution, the DAS demodulator calculates the location of the leak point based on the time difference, using the following formula: L1 = (L + V * Δt) / 2; Where L represents the distance between the first and second probes; V represents the propagation speed of the stress wave in the pipe wall to be tested; Δt is the measured time difference; and L1 is the distance from the leak point to the first probe.

[0014] As an optional technical solution, the DAS demodulator is also used to convert the time axis t of the Rayleigh scattering signal into the distance axis D, obtaining a curve of the scattered light intensity distribution with distance, the conversion formula being: Distance D = (speed of light c / refractive index of fiber n) × time t / 2.

[0015] A second aspect of the present invention provides a method for detecting pipeline leaks.

[0016] The pipeline leak detection method based on the pipeline leak detection device based on the miniature point fiber optic probe described in the first aspect includes the following steps: The first and second probes are respectively installed at the designated locations on the pipeline to be inspected; Register the positions of the first probe and the second probe to obtain the first registration point position where the first probe is located and the second registration point position where the second probe is located. The stress wave generated by the pipeline leak propagates along the pipe wall and reaches the first and second probes in succession. The DAS demodulator simultaneously or time-divisionally queries two probes to acquire the phase change signals of the first registration point position and the second registration point position; Based on the phase change signals of the first and second registration point positions, the time difference of the stress wave generated by the pipeline leak propagating from the leak point to the first and second probes is calculated. The DAS demodulator calculates the location of the leak point based on the time difference. The above one or more technical solutions have the following beneficial effects: This invention provides a pipeline leak detection device and method based on a miniature point fiber optic probe. It is extremely flexible in deployment and can be quickly deployed at key points of the pipeline (such as flanges and valve bodies). It also has extremely high detection sensitivity to high-frequency vibrations generated by minor leaks, enabling vibration measurement of the point probe at the end of the fiber optic cable, thereby achieving high-precision location of leaks in deeply buried thermal pipelines.

[0017] This invention employs an ultra-short, independent micro-probe design, which has the following significant advantages compared to existing technologies: Extremely convenient deployment: The centimeter-level probe, combined with the magnetic base, can be used immediately in narrow spaces such as valve wells, making it extremely fast to deploy and ideal for temporary testing or inspection of key areas.

[0018] Extremely high spatial resolution: The sensitive length of 5-10 cm means that the probe can only detect the vibration of a very small section of the pipe directly below it, which greatly eliminates vibration interference from other parts of the pipe, making the positioning indication very accurate.

[0019] Completely independent channels: Dual independent optical fibers completely eliminate signal crosstalk that may exist in a shared optical path, ensuring the purity of signals from the two measurement points and improving the reliability of time difference positioning.

[0020] The system is highly flexible: the probe and transmission fiber optic cable can be made into a portable inspection kit, and a single DAS demodulator can be equipped with multiple such kits for routine inspection of pipelines in different locations.

[0021] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a structural diagram of the device in Embodiment 1.

[0024] The attached diagram lists the components represented by each number as follows: 1. DAS demodulator; 2. First transmission optical cable; 3. Second transmission optical cable; 4. First probe; 5. Second probe; 6. Pipe to be tested; 7. Leak point. Detailed Implementation

[0025] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0027] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0028] Example 1 This embodiment discloses a pipeline leak detection device based on a miniature point-type fiber optic probe. The device consists of a DAS demodulator, two independent optical cables, and two centimeter-scale miniature probes. The probes are quickly fixed to the pipeline by means of magnetic attraction or other methods; the DAS system focuses on monitoring the vibration at only the probe location; and precise positioning is achieved by utilizing the time difference between the two independent signals.

[0029] This invention integrates the advantages of convenient deployment of point sensors and high sensitivity of DAS technology, making it particularly suitable for rapid and accurate leak detection and location of deeply buried pipelines.

[0030] like Figure 1 As shown, a pipeline leak detection device based on a miniature point fiber optic probe includes a DAS demodulator and at least one set of detection devices. The detection devices include a first transmission optical cable and a second transmission optical cable that are independently set. The beginnings of the first transmission optical cable and the second transmission optical cable are respectively connected to the DAS demodulator. The ends of the first transmission optical cable and the second transmission optical cable are respectively provided with a first probe and a second probe. The first probe and the second probe are fixedly connected to the outside of the pipeline to be detected. The DAS demodulator is used to calculate the time difference between the vibration signal propagating from the leak point to the first and second probes based on the vibration signals transmitted back from the first and second probes, and to calculate the location of the leak point based on the time difference.

[0031] This embodiment aims to provide a device that is extremely flexible in its deployment, can be quickly deployed at critical points in pipelines (such as flanges and valve bodies), and has extremely high detection sensitivity to high-frequency vibrations caused by minute leaks. For example... Figure 1 As shown, the pipeline leak detection device based on a miniature point fiber optic probe provided in this embodiment mainly includes the following components: (1) DAS demodulator (built-in Φ-OTDR): This is the core device of the device in this embodiment. The key point is that it has two independent detection channels (first transmission optical cable and second transmission optical cable), which can simultaneously or time-divisionally transmit detection pulses to two independent optical paths and process the return signals.

[0032] (2) First transmission optical cable and second transmission optical cable: These are two physically separate independent optical cables, which are the key to achieving signal purity and avoiding crosstalk.

[0033] (3) Miniature point fiber optic sensing probe (first probe and second probe): In this embodiment, a first probe is set at the end of the first transmission optical cable and a second probe is set at the end of the second transmission optical cable. The first probe and the second probe are fiber optic probes that have been enhanced in sensitivity. Their size is much smaller than the length of the pipe. They are encapsulated in an interior with a magnetic base and can be quickly adsorbed onto the exposed part of the iron pipe on site; or they can be encapsulated in an interior of a mechanical housing with a clamp connected to the mechanical housing and fixed to the pipe to be tested through the clamp.

[0034] In this embodiment, the clamp can be a clamp or similar device, which is convenient to use on the cylindrical pipe wall to be tested.

[0035] (4) The pipeline to be tested is buried deep underground, and the leak point is located in a complex underground environment. Only the two ends are easy to measure.

[0036] (5) Leakage point: that is, the point where water leaks. When a leak occurs, vibration stress waves will propagate along the pipe wall to both sides.

[0037] The technical solution of this embodiment will now be explained in detail.

[0038] The pipeline leak detection device based on miniature point fiber optic probes in this embodiment includes: a DAS demodulator, two completely independent transmission optical cables, and two miniature point fiber optic sensing probes. The DAS demodulator, with at least two independent detection channels embedded within it, or switched via an optical switch, is used to emit laser pulses into two independent optical paths and receive their respective backscattered Rayleigh signals. Its core is a phase-sensitive optical time-domain reflectometer (Φ-OTDR), meaning the DAS demodulator contains a phase-sensitive optical time-domain reflectometer (Φ-OTDR). Its signal processing unit is configured as follows: The optical phase change signal at a specific distance corresponding to the installation position of the miniature probe at the end of each independent optical path is read and analyzed separately. The two transmission optical cables are physically separate, meaning the first and second transmission optical cables are installed separately. Each transmission optical cable is connected to an output port of the DAS demodulator and a miniature point-type fiber optic sensor probe at each end.

[0039] The core sensing element of the miniature point fiber optic sensor is a short fiber optic cable with a length of 5 to 10 centimeters. This fiber optic cable is subjected to sensitization treatment (such as removing part of the coating layer to enhance mechanical coupling).

[0040] The first and second probes are encapsulated inside a housing with a magnetic base or mechanical clamp, which facilitates quick adsorption or fixation to exposed parts of iron pipes on site.

[0041] Each probe is essentially an independent, ultra-sensitive vibration sensor. When using this embodiment, the specific steps include: 1. Rapid deployment: Two miniature point fiber optic sensing probes are magnetically attached to the outer walls of the pipe at both ends of the suspected leaking pipe section (e.g., inside two adjacent valve wells), or to the outer wall of any pipe to be tested.

[0042] 2. Channel Registration and Focus: Connect two independent optical cables to the DAS demodulator. The instrument accurately registers the distance coordinates corresponding to each probe by measuring the round-trip time of the optical pulse (e.g., channel A: 50.125 meters; channel B: 50.255 meters).

[0043] In subsequent monitoring, the system only continuously monitors the phase signals near these two coordinate points.

[0044] The specific method is as follows: (1) Transmission and reception: The DAS demodulator transmits an extremely narrow laser pulse to an optical path (first transmission optical cable / first channel).

[0045] (2) Obtaining the scattering curve: When a pulse propagates in an optical fiber, each point will generate backscattered Rayleigh light. The demodulator receives the curve of the intensity of the scattered light returned from the entire optical fiber as a function of time, which is the initial Rayleigh scattering curve.

[0046] (3) Distance mapping: According to the formula distance D = (speed of light c / fiber refractive index n) × time t / 2, the time axis t is accurately converted into the distance axis D. Thus, the demodulator obtains a curve of the scattered light intensity distribution with distance.

[0047] (4) Probe Position Registration (Precise Positioning): After the technician installs the probe, during the initial calibration phase, he will gently tap the pipe where the first probe of the fiber optic sensor is located. The demodulator will continuously collect Rayleigh scattering curves.

[0048] ① Obtain a background curve when no tapping is performed.

[0049] ② When struck, the optical fiber at the point where the optical fiber sensor probe is located undergoes micro-strain, causing a drastic change in the phase of the Rayleigh scattering signal at that point, which in turn causes significant fluctuations in the intensity of the scattered light at that point.

[0050] ③ By comparing the changes in the Rayleigh scattering curve before and after the impact, the system can pinpoint the "point" where the light intensity changes with extreme precision. The distance coordinates corresponding to this point (e.g., 50.125 meters) are the location of the fiber optic sensor probe. The system registers these coordinates as the monitoring point of the first probe on the first transmission optical cable.

[0051] (5) Repeat the operation: Repeat steps (1)-(4) for another independent optical path (second transmission optical cable / second channel) to register the coordinates of the fiber optic sensor probe (e.g., 50.255 meters).

[0052] Subsequently, in all subsequent monitoring, the DAS demodulator will no longer process data from the entire fiber, but will instead focus all its signal processing capabilities (phase demodulation algorithm) on these two registered, centimeter-scale "points," thereby improving the signal-to-noise ratio and sensitivity.

[0053] 3. Signal acquisition and demodulation: The DAS demodulator simultaneously or time-divisionally queries two probes. Pipe vibration acts on the miniature probe, causing deformation of the short optical fiber inside, thereby modulating the phase of the backscattered Rayleigh light.

[0054] 4. Time difference positioning: The stress wave generated by the leak propagates along the pipe wall and reaches the two probes sequentially. The system calculates the time difference Δt between the two independent signals using a cross-correlation algorithm, and substitutes it into the formula L1 = (L + V * Δt) / 2 to accurately calculate the location of the leak.

[0055] The specific method is as follows: (1) Signal acquisition: The system synchronously acquires the phase change signals of the two registration points, denoted as S_A(t) and S_B(t), which represent the change of strain caused by pipeline vibration over time.

[0056] (2) Signal preprocessing: Filter the two signals to remove obvious external high-frequency noise and low-frequency drift, and retain the characteristic frequency band that may exist in leakage vibration.

[0057] (3) Cross-correlation calculation to find Δt: Calculate the cross-correlation function R_AB(τ) of the two signals: R_AB(τ) = Σ [ S_A(t) * S_B(t + τ) ] By iterating through all possible time offsets τ, find the τ_max that maximizes R_AB(τ).

[0058] This τ_max represents the time difference Δt between the vibration signal propagating from the leak point to the two probes. If the maximum value is τ>0, it means the signal arrives at A before B, and the leak point is closer to A.

[0059] (4) Precise positioning: Calculate using the formula mentioned above.

[0060] Given: The distance between the two probes is L, the propagation velocity of the stress wave in the pipe wall is V, and the measured time difference is Δt.

[0061] Let the distance from the leak point to probe A be L1, and the distance to probe B be L2, then L1 + L2 = L.

[0062] The time difference for the vibration wave to reach the two probes is: Δt = (L1 / V) - (L2 / V) = (L1 - L2) / V.

[0063] Combine the two equations: Equation 1: L1 + L2 = L; Equation 2: L1 - L2 = V * Δt; Add Equation 1 and Equation 2 to solve for the leakage point location: 2L1 = L + V * Δt =>L1 = (L + V * Δt) / 2 5. Event recognition: Analyze the frequency components of the vibration signal to identify the characteristic frequencies generated by leakage cavitation, turbulence, etc., in order to distinguish from interference such as impact and friction.

[0064] The specific method is: (1) Spectrum analysis: Perform a fast Fourier transform on the collected vibration signal segment to convert it from the time domain to the frequency domain and observe its power spectral density.

[0065] (2) Establish a leakage spectrum feature library: Through laboratory simulations or known leakage cases, summarize the typical frequency domain characteristics of the vibration signals of thermal pipeline leaks. These characteristics usually include: ① Wideband characteristic: The energy is distributed over a relatively wide frequency range rather than a single frequency point.

[0066] ② Characteristic frequency band: Due to cavitation and turbulence, there is usually continuous energy concentration in the medium and high frequency bands (e.g., 5 kHz - 20 kHz).

[0067] ③ Persistence: The leakage signal is continuous rather than a short pulse.

[0068] ④ Set recognition rules: Based on the feature library, set simple and feasible recognition rules.

[0069] For example: Band energy ratio criterion --- Calculate the ratio of the energy of the signal in the characteristic frequency band (such as 5 - 20 kHz) to the energy of the full frequency band (or low frequency band). If this ratio continuously exceeds a certain empirical threshold, it indicates that there may be a leak.

[0070] Dual-channel correlation criterion --- A real leakage signal will necessarily be detected by two probes, and the calculated propagation time difference Δt and the positioning result L1 are physically reasonable (i.e., 0 < L1 < L). Many local disturbances (such as impacts near a single probe) are usually clearly captured by only one probe, or the calculated time difference and position are significantly unreasonable.

[0071] The criterion that "the dual-channel signals are correlated and the positioning results are physically reliable" is a powerful criterion for distinguishing between leakage and interference.

[0072] Example 2 This embodiment discloses a method for detecting pipeline leaks.

[0073] The pipeline leak detection method based on the pipeline leak detection device based on the miniature point fiber optic probe described in Embodiment 1 includes the following steps: The first and second probes are respectively installed at the designated locations on the pipeline to be inspected; Register the positions of the first probe and the second probe to obtain the first registration point position where the first probe is located and the second registration point position where the second probe is located. The stress wave generated by the pipeline leak propagates along the pipe wall and reaches the first and second probes in succession. The DAS demodulator simultaneously or time-divisionally queries two probes to acquire the phase change signals of the first registration point position and the second registration point position; Based on the phase change signals of the first and second registration point positions, the time difference of the stress wave generated by the pipeline leak propagating from the leak point to the first and second probes is calculated. The DAS demodulator calculates the location of the leak point based on the time difference. Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0074] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A pipeline leak detection device based on a miniature point-type fiber optic probe, characterized in that, It includes a DAS demodulator and at least one set of detection devices. The detection devices include a first transmission optical cable and a second transmission optical cable that are independently set. The beginnings of the first transmission optical cable and the second transmission optical cable are respectively connected to the DAS demodulator. The ends of the first transmission optical cable and the second transmission optical cable are respectively provided with a first probe and a second probe. The first probe and the second probe are fixedly connected to the outside of the pipe to be tested. The DAS demodulator is used to calculate the time difference between the vibration signal propagating from the leak point to the first and second probes based on the vibration signals transmitted back from the first and second probes, and to calculate the location of the leak point based on the time difference.

2. The pipeline leak detection device based on a miniature point-type fiber optic probe as described in claim 1, characterized in that, The first and second probes are used to detect vibration signals in the pipeline under test.

3. The pipeline leak detection device based on a miniature point-type fiber optic probe as described in claim 1, characterized in that, The first and second probes are centimeter-level fiber optic probes of a preset length, and the fiber optic probes have undergone sensitivity enhancement treatment.

4. The pipeline leak detection device based on a miniature point-type fiber optic probe as described in claim 3, characterized in that, The first and second probes are encapsulated and fixed inside a base or housing. The base has a magnetic attraction function, and the housing is connected to a clamp.

5. The pipeline leak detection device based on a miniature point-type fiber optic probe as described in claim 1, characterized in that, The DAS demodulator is also used to calibrate the position coordinates of the first and second probes before calculating the location of the leak point: After the first probe is installed, the background curve of the Rayleigh scattering signal corresponding to the first probe is first obtained by the DAS demodulator. Then, the pipe where the first probe is located is tapped. The vibration generated by the tapping is transmitted through the first probe and the first transmission optical cable to the DAS demodulator, generating a Rayleigh scattering signal due to the tapping. By comparing the Rayleigh scattering signal generated by the tap with the background curve, the point where the light intensity changes is located, and the distance coordinates corresponding to this point are marked as the position of the first probe, that is, the position of the first registration point. Similarly, the position of the second probe is calibrated to obtain the position of the second registration point.

6. The pipeline leak detection device based on a miniature point-type fiber optic probe as described in claim 5, characterized in that, The DAS demodulator is also used to process only the fiber optic signals obtained from the first and second registration point locations after acquiring the first and second registration point locations.

7. The pipeline leak detection device based on a miniature point-type fiber optic probe as described in claim 5, characterized in that, The DAS demodulator is used to calculate the time difference between the vibration signal propagating from the leak point to the first and second probes based on the vibration signals transmitted back from the first and second probes. Specifically: The stress wave generated by the pipeline leak propagates along the pipe wall and reaches the first and second probes in succession. The DAS demodulator simultaneously or time-divisionally queries two probes to acquire the phase change signals of the first registration point position and the second registration point position, denoted as S_A(t) and S_B(t). Filter S_A(t) and S_B(t); The time difference Δt between S_A(t) and S_B(t) after filtering is calculated using a cross-correlation algorithm.

8. The pipeline leak detection device based on a miniature point-type fiber optic probe as described in claim 7, characterized in that, The DAS demodulator calculates the location of the leak point based on the time difference, using the following formula: L1 = (L + V * Δt) / 2; Where L represents the distance between the first and second probes; V represents the propagation speed of the stress wave in the pipe wall to be tested; Δt is the measured time difference; and L1 is the distance from the leak point to the first probe.

9. The pipeline leak detection device based on a miniature point-type fiber optic probe as described in claim 5, characterized in that, The DAS demodulator is also used to convert the time axis t of the Rayleigh scattering signal into the distance axis D, obtaining a curve of the scattered light intensity as a function of distance. The conversion formula is as follows: Distance D = (speed of light c / refractive index of fiber n) × time t / 2.

10. A pipeline leak detection method based on the pipeline leak detection device based on a miniature point fiber optic probe according to any one of claims 1-9, characterized in that, Includes the following steps: The first and second probes are respectively installed at the designated locations on the pipeline to be inspected; Register the positions of the first probe and the second probe to obtain the first registration point position where the first probe is located and the second registration point position where the second probe is located. The stress wave generated by the pipeline leak propagates along the pipe wall and reaches the first and second probes in succession. The DAS demodulator simultaneously or time-divisionally queries two probes to acquire the phase change signals of the first registration point position and the second registration point position; Based on the phase change signals of the first and second registration point positions, the time difference of the stress wave generated by the pipeline leak propagating from the leak point to the first and second probes is calculated. The DAS demodulator calculates the location of the leak point based on the time difference.

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