A disturbance range positioning method based on a distributed weak grating array sensing system

Abstract

The application discloses a disturbance range positioning method based on a distributed weak grating array sensing system, relates to the technical field of optical fiber sensing, and aims to solve the problem that the disturbance positioning precision of an existing weak grating array sensing system is limited by the writing interval of the weak grating. The first pulse light and the second pulse light with a specific width, which are emitted into a sensing optical fiber in sequence, are used as probe light, the emission time of the two pulse lights is adjusted, the reflection signals generated after the reflection of the two pulse lights on the grating array are interfered to form beat signals. During the propagation of the pulse light in the optical fiber, the scattered light generated when the pulse light passes through the disturbance position is superimposed with the corresponding reflected light, and then causes the crosstalk of the beat signals. The corresponding relationship between the crosstalk time domain and the disturbance space domain is constructed, the crosstalk information on the corresponding beat signals of the left and right adjacent sensing units of the disturbance is combined, the accurate positioning of the disturbance boundary is realized, and the positioning resolution in the weak grating array sensing system is improved.

Description

Technical Field

[0001] This invention relates to a disturbance range localization method based on a distributed weak grating array sensing system, belonging to the field of fiber optic sensing technology. Background Technology

[0002] With the maturation of fiber Bragg grating (FBG) manufacturing technology, weak FBG arrays are used as sensing units embedded in optical fibers. As a type of FBG, weak FBG arrays are characterized by their extremely low reflectivity, typically less than 0.1% (-30 dB). Inscribing them onto the fiber does not introduce significant transmission loss, allowing multiple weak gratings to be multiplexed into an array. Sensing systems based on weak grating arrays are similar to those based on single-mode fibers, but the sensing fiber is replaced by a weak grating array, and the sensing light is changed from scattered light to reflected light, thus achieving higher signal-to-noise ratios and stability.

[0003] However, in existing weak grating array sensing systems, the accuracy of disturbance localization is limited by the spacing between the weak gratings. Existing methods can typically only determine that a disturbance occurs between two adjacent weak gratings, making it difficult to further determine the spatial range of the disturbance and its boundary location. Therefore, a method capable of achieving high-precision localization of the disturbance range is currently lacking. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a disturbance range localization method based on a distributed weak grating array sensing system, which can improve the localization resolution of the disturbance range in the distributed weak grating array sensing system.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] This invention provides a method for locating the disturbance range based on a distributed weak grating array sensing system, comprising:

[0007] The first pulse light and the second pulse light are reflected sequentially to the distributed weak grating array sensing system, and the first pulse light and the second pulse light form a beat frequency signal through the distributed weak grating array.

[0008] In a distributed weak grating array, a sampling point is selected on the beat frequency signal formed between two adjacent gratings for phase demodulation and dewinding to achieve the initial positioning perturbation range. The initial positioning perturbation range is denoted as [U]. m U m+1 ], where U m U represents the location of the m-th weak grating. m+1 This indicates the location of the (m+1)th weak grating;

[0009] Based on the initial positioning disturbance range, phase demodulation and dewinding are performed on all sampling points on the beat frequency signal formed between the position of the (m-1)th weak grating and the position of the mth weak grating, and the left boundary of the disturbance range is located by combining the time of crosstalk.

[0010] Based on the initial positioning of the disturbance range, phase demodulation and dewinding are performed on all sampling points of the beat frequency signal formed between the location of the (m+1)th weak grating and the location of the (m+2)th weak grating, and the right boundary of the disturbance range is located again by combining the time of crosstalk.

[0011] The final positioning disturbance range is obtained by combining the left and right boundaries of the disturbance range obtained from the secondary positioning.

[0012] Furthermore, the distributed weak grating array sensing system includes a narrow-line pulse laser and a pulse signal generator. The narrow-line pulse laser is used to output continuous light. The continuous light is split by a first coupler and then input to a first acousto-optic modulator and a second acousto-optic modulator. The pulse signal generator is used to generate a driving signal with a preset timing relationship to control the working state of the first acousto-optic modulator and the second acousto-optic modulator.

[0013] Under the action of the driving signal, the first acousto-optic modulator and the second acousto-optic modulator are respectively used to perform time-series modulation on continuous light to generate a first pulse light and a second pulse light respectively;

[0014] The first and second pulses are combined by the second coupler to form a double-pulse optical signal. The double-pulse optical signal is amplified by an erbium-doped fiber amplifier and then fed into a distributed weak grating array through a circulator. The distributed weak grating array generates a beat frequency signal on the amplified double-pulse optical signal. The beat frequency signal is fed back to the circulator and then input to a photodetector. The photodetector converts the beat frequency signal into an electrical signal. The electrical signal is digitally acquired by a data acquisition card and then transmitted to an external computing system.

[0015] Furthermore, the distributed weak grating array includes multiple weak gratings arranged sequentially, with two adjacent weak gratings forming a sensing unit.

[0016] Furthermore, each of the sensing units corresponds to a beat frequency signal. The process of forming the beat frequency signal includes: in each sensing unit, the first pulse light is reflected by the rear weak grating and returns to the front weak grating. At this time, the second pulse light is reflected by the front weak grating, and the two reflected lights interfere with each other at the front weak grating to form a beat frequency signal.

[0017] Furthermore, the emission time interval between the first pulse light and the second pulse light satisfies the following expression:

[0018] ;

[0019] in, This indicates the time interval between the emission of the first and second pulses of light. This represents the effective refractive index of a distributed weak grating array. This represents the grating spacing in a distributed weak grating array. This represents the speed of light in a vacuum.

[0020] Furthermore, the first pulse and the second pulse have the same pulse width and satisfy the following expression:

[0021] ;

[0022] in, Indicates the pulse width. This represents the effective refractive index of a distributed weak grating array. This represents the grating spacing in a distributed weak grating array. This represents the speed of light in a vacuum.

[0023] Furthermore, a sampling point is selected on the beat frequency signal formed between two adjacent gratings in the distributed weak grating array for phase demodulation and dewinding to realize that the sampling point in the initial positioning disturbance range is the center point of the beat frequency signal.

[0024] Furthermore, the calculation expression for the left boundary of the secondary positioning disturbance range is as follows: , among which, U m This indicates the location of the m-th weak grating. Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. Indicates the pulse width. This indicates the time range during which crosstalk exists between the beat frequency signals formed between the (m-1)th weak grating and the mth weak grating.

[0025] Furthermore, the calculation expression for the right boundary of the secondary positioning disturbance range is as follows: , among which, U m+1 This indicates the location of the (m+1)th weak grating. Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. Indicates the pulse width. This represents the time range during which crosstalk exists in the beat frequency signal formed between the positions of the (m+1)th weak grating and the (m+2)th weak grating.

[0026] Furthermore, when the sampling rate is greater than 100MHz, the positioning resolution of the final positioning disturbance range... Less than 1m, of which, Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. This indicates the sampling rate.

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0028] This invention utilizes the crosstalk boundary information formed by scattered light in the target beat frequency signal, and realizes the inversion and positioning of the disturbance position through the correspondence between the beat frequency crosstalk boundary and the spatial position, thereby enabling high-resolution determination of the disturbance position between two adjacent sensing units composed of gratings.

[0029] When the sampling rate is greater than 100MHz, the positioning method of the present invention can achieve positioning resolution. With a spatial resolution of less than 1m, the positioning resolution is improved compared to the traditional method's spatial resolution ΔL. times ( Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. (Indicates the sampling rate). Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the distributed weak grating array sensing system in the disturbance range localization method based on the distributed weak grating array sensing system in one embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram illustrating the variation of the interference window at different sampling points on beat frequency 2 in a disturbance range localization method based on a distributed weak grating array sensing system in one embodiment of the present invention.

[0032] Figure 3 This is a schematic diagram illustrating the principle of achieving high-precision disturbance range positioning using an interference window of adjacent beat frequencies in a disturbance range positioning method based on a distributed weak grating array sensing system in one embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram of the beat frequency signal obtained in the disturbance range localization method based on a distributed weak grating array sensing system in one embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram of the three-dimensional results of phase demodulation and dewinding at different sampling points on the beat frequency signal corresponding to the sensing unit where the disturbance is located in a disturbance range localization method based on a distributed weak grating array sensing system in one embodiment of the present invention.

[0035] Figure 6This is a schematic diagram of phase demodulation and dewinding waterfall on the left beat frequency signal corresponding to different sampling points of the sensing unit where the disturbance is located in the disturbance range localization method based on the distributed weak grating array sensing system in one embodiment of the present invention;

[0036] Figure 7 This is a schematic diagram of phase demodulation and unwinding waterfall on the beat frequency signal corresponding to different sampling points on the right side of the sensing unit where the disturbance is located, in the disturbance range localization method based on a distributed weak grating array sensing system according to an embodiment of the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0038] This invention provides a method for locating the disturbance range based on a distributed weak grating array sensing system. The structure of the distributed weak grating array sensing system is as follows: Figure 1 As shown, it specifically includes a narrow linewidth laser, a coupler, a pulse signal generator, an acousto-optic modulator, an erbium-doped fiber amplifier, a circulator, a sensing fiber with a weak grating array inscribed on it, a photodetector, a data acquisition card, and an external computing system.

[0039] A narrow-linewidth laser outputs continuous light, which is split by a first coupler and then input to a first acousto-optic modulator and a second acousto-optic modulator. A pulse signal generator is used to generate drive signals with a preset timing relationship to control the operating state of the first and second acousto-optic modulators.

[0040] Under the action of the driving signal, the first and second acousto-optic modulators perform time-series modulation on the continuous light, respectively, to generate a first pulse light and a second pulse light with a specific period, a specific pulse width and a specific pulse interval. The two pulse lights are introduced with different frequency shifts under the action of the acousto-optic modulators, thus having different optical frequencies.

[0041] The first and second pulses of light are combined by a second coupler to form a double-pulse light signal, which is then further amplified by an erbium-doped fiber amplifier. Utilizing its unidirectional transmission characteristic, the circulator guides the amplified double-pulse light signal into the sensing fiber (i.e., a distributed weak grating array). Multiple weak gratings distributed along the fiber reflect the incident double-pulse light signal, and the reflected light from the two pulses at each grating superimposes to produce interference, forming an interference light signal. This interference light signal is then output from the circulator and converted into an electrical signal by a photodetector. This electrical signal, representing a beat frequency signal, reflects disturbance information in the sensor system. Subsequently, a data acquisition card digitizes the beat frequency signal, converts it into a digital signal, and transmits it to an external computing system. The external computing system analyzes and processes the acquired data to locate and analyze the disturbance range.

[0042] Based on the aforementioned distributed weak grating array sensing system, the disturbance range localization method specifically includes the following steps:

[0043] S1. The first pulse light and the second pulse light are emitted sequentially to the distributed weak grating array sensing system. The two pulse lights interfere with the reflected signals generated by the distributed weak grating array to form a beat frequency signal.

[0044] A distributed weak grating array includes multiple weak gratings arranged sequentially. Two adjacent weak gratings constitute a sensing unit. Taking the m-th weak grating and the (m+1)-th weak grating as an example, when the first pulse light is emitted, it is reflected by the (m+1)-th weak grating and returns to the m-th weak grating. At the same time, the second pulse light just reaches the m-th weak grating and completes reflection. At this time, the reflected light of the two pulses meet and interfere at the m-th weak grating, thus forming a beat frequency signal.

[0045] In this embodiment, the first pulse light and the second pulse light pass through the (m-1), m, m+1, and m+2 weak gratings in sequence, forming beat frequencies 1, 2, and 3, respectively. Specifically, the positions of the four gratings are represented as U. m-1 U m U m+1 U m+2 .

[0046] It should be noted that the emission time interval between the first pulse and the second pulse must satisfy the following expression:

[0047] ;

[0048] in, This indicates the time interval between the emission of the first and second pulses of light. This represents the effective refractive index of a distributed weak grating array. This represents the grating spacing in a distributed weak grating array. This represents the speed of light in a vacuum.

[0049] Furthermore, to facilitate subsequent positioning at any location within the sensing unit composed of adjacent weak gratings, the pulse widths of the first and second pulses must satisfy the following expression:

[0050] ;

[0051] in, This indicates the pulse width, which is equal to the time width corresponding to the spacing between adjacent weak gratings.

[0052] S2, the first pulse light, and the second pulse light will continuously generate scattered light during propagation in the distributed weak grating array. When there is a disturbance in the distributed weak grating array, the scattered light generated at the disturbance location will overlap with the reflected light at the corresponding grating location, thereby introducing crosstalk noise into the corresponding beat frequency signal.

[0053] The following example, using beat frequency 2 between the m-th weak grating and the (m+1)-th weak grating, illustrates the crosstalk formation mechanism at beat frequency 2. Specifically:

[0054] For the first pulse light, when the perturbation position is located between the m-th weak grating and the (m+1)-th weak grating, or between the (m+1)-th weak grating and the (m+2)-th weak grating, the first pulse light is at the perturbation position. The scattered light generated at each location may overlap with the reflected light generated at the (m+1)th weak grating, thus creating crosstalk caused by the first pulse light at beat frequency 2.

[0055] For beat frequency 2 The position of the perturbation at the beat frequency corresponding to the time when it is subjected to crosstalk caused by the first pulse light. It should meet the following requirements:

[0056]

[0057] in, This indicates the start time of beat frequency 2. This represents the time offset of the beat frequency point on beat frequency 2 relative to the start time of beat frequency 2; This indicates that the leading edge of the first pulse light has reached the disturbance position. The moment when the scattered light returns to the photodetector This indicates that the trailing edge of the first pulse light reaches the disturbance position. The moment when the scattered light generated returns to the photodetector.

[0058] From the above formula, it can be seen that for the time in beat frequency 2... When the corresponding beat frequency point is subjected to crosstalk caused by the first pulse light, the disturbance location is distributed within the following interval:

[0059]

[0060] The above interval is defined as the first pulse light interference window corresponding to beat frequency 2. With... As the frequency changes, the first pulse light interference window corresponding to beat frequency 2 will move along the fiber direction, thereby scanning the disturbance position within a certain spatial range.

[0061] For the second pulse, when the perturbation position is located between the m-th weak grating and the (m+1)-th weak grating, or between the (m-1)-th weak grating and the m-th weak grating, the second pulse is at the perturbation position. The scattered light generated at each location may overlap with the reflected light generated at the m-th weak grating, thus creating crosstalk caused by the second pulse light at beat frequency 2.

[0062] Based on the emission time interval between the first pulse light and the second pulse light For beat frequency 2 When the beat frequency point corresponding to a given moment is subjected to crosstalk caused by the second pulse light, the location of the disturbance is... It should meet the following requirements:

[0063]

[0064] in, This indicates the start time of beat frequency 2. This indicates that the leading edge of the second pulse light has reached the disturbance position. The time it takes for the generated scattered light to return to the photodetector. This indicates that the trailing edge of the second pulse light reaches the disturbance position. The time it takes for the scattered light generated to return to the photodetector.

[0065] From the above formula, it can be seen that for beat frequency 2... When the beat frequency point corresponding to a given time is subjected to crosstalk caused by the second pulse light, the disturbance location is distributed within the following interval:

[0066]

[0067] The above interval is defined as the second pulse light interference window corresponding to beat frequency 2. With As the frequency changes, the second pulse light interference window corresponding to beat frequency 2 will move along the fiber direction, thereby scanning the disturbance position within a certain spatial range.

[0068] As can be seen from the above analysis, when crosstalk occurs at a beat frequency point corresponding to a certain moment in beat frequency 2, the interval where the disturbance is located can be determined based on the positions of the first pulse light interference window and the second pulse light interference window corresponding to that moment.

[0069] like Figure 2 As shown, in time( =0), the coverage areas of the first and second pulse light interference windows corresponding to beat frequency 2 are respectively and Therefore, if crosstalk occurs at the beat frequency point corresponding to that moment, it indicates that the disturbance may be located between the m-th and (m+1)-th gratings, or between the (m-1)-th and m-th gratings. At time 1, the coverage areas of the two interference windows respectively become and Therefore, if crosstalk occurs at the beat frequency point corresponding to that moment, it indicates that the disturbance may be located between the (m+1)th and (m+2)th gratings, or between the mth and (m+1)th gratings.

[0070] Since the phase demodulation and unwinding results are only weak phase noise when there is no external disturbance, significant phase fluctuations will occur when there is a disturbance. Therefore, preliminary positioning is achieved based on the phase fluctuation. Thus, a sampling point is selected on the beat frequency signal generated by each sensing unit for phase demodulation and unwinding to achieve initial positioning of the disturbance range. In this embodiment, the initial positioning disturbance range is represented as [U... m U m+1 ], where U m U represents the location of the m-th weak grating. m+1 This indicates the location of the (m+1)th weak grating.

[0071] In some embodiments, the optimal location of the selected sampling point is the center point of the beat frequency signal.

[0072] Whether crosstalk occurs at any beat frequency point in beat frequency 2 depends on whether there is a disturbance within the coverage area of ​​the first and second pulse light interference windows at that moment. As time changes, the two interference windows move along the fiber direction, and their coverage relationship with the disturbance location also changes accordingly. Therefore, the crosstalk state of the corresponding beat frequency point will change. Therefore, after determining in step S2 that the disturbance is located between the m-th grating and the (m+1)-th grating, the sensing unit composed of the m-th grating and the (m+1)-th grating can be scanned using the first pulse light interference window corresponding to beat frequency 1 and the second pulse light interference window corresponding to beat frequency 3. Combined with the distribution of crosstalk in beat frequencies 1 and 3, the left and right boundaries of the disturbance interval can be determined.

[0073] S3. When a disturbance exists between the m-th and m+1-th gratings, the disturbance range is... At that time, the first pulse light interference window corresponding to beat frequency 1 is used. The sensing unit composed of the m-th and (m+1)-th gratings is scanned, where This is the time offset of the beat frequency point on beat frequency 1 relative to the start time of beat frequency 1.

[0074] like Figure 3 As shown, the initial coverage area of ​​the first pulse light interference window corresponding to beat frequency 1 is... As the beat frequency point on beat frequency 1 moves continuously, the interference window gradually enters the area between the m-th and m+1-th gratings, and thus its coverage area changes accordingly.

[0075] When the right boundary of the window moves to the disturbance position At this point, the window begins to overlap with the perturbation range, and crosstalk begins to occur at the corresponding beat frequency point on beat frequency 1. Subsequently, as the interfering window continues to move to the right, the crosstalk at the corresponding beat frequency point will persist because the window always covers a portion of the perturbation range. When the window moves to the farthest scanning position, the pulse width is exactly equal to the spacing between adjacent gratings. The corresponding time length, at which point the coverage area of ​​the interference window is... At this point, the entire disturbance range exists within this window, and the crosstalk determination for all beat frequency points on beat frequency 1 is complete. Therefore, it can be seen that crosstalk on beat frequency 1 manifests as appearing from a certain beat frequency point and continuing until the beat frequency signal ends. The time offsets corresponding to the beat frequency points where crosstalk occurs on beat frequency 1 are as follows:

[0076]

[0077] Therefore, when crosstalk exists on beat frequency 1 for a time range of 1, , Therefore, the left boundary of the disturbance range can be obtained by inverting the time range of crosstalk on beat frequency 1. This allows for secondary positioning of the left boundary of the disturbance range:

[0078]

[0079] Based on the above derivation process, this step only requires phase demodulation and dewinding of all sampling points on beat frequency 1 formed between the (m-1)th and mth samples, and considering the time of crosstalk on beat frequency 1. The left boundary of the disturbance range is located a second time, and its expression is: , among which, U m This indicates the location of the m-th weak grating. Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. Indicates the pulse width. This indicates the time range during which crosstalk exists between the beat frequency signals formed between the (m-1)th weak grating and the mth weak grating.

[0080] S4. When there is a disturbance between the m-th and m+1-th gratings, the disturbance range is... At that time, the second pulse light interference window corresponding to beat frequency 3 is used. The sensing unit composed of the m-th and (m+1)-th gratings is scanned, where This is the time offset of the beat frequency point on beat frequency 3 relative to the starting time of beat frequency 3.

[0081] like Figure 3 As shown, since the pulse width is equal to the spacing between adjacent gratings... The corresponding time length, the initial coverage area of ​​the second pulse light interference window corresponding to beat frequency 3 is As the beat frequency point on beat frequency 3 moves continuously, the interference window gradually moves away from the area between the m-th and m+1-th gratings, and its coverage area changes accordingly. At this point, the disturbance interval falls completely within the window, so crosstalk exists at the beat frequency point corresponding to beat frequency 3. As the window continues to move to the right, the disturbance interval within the window gradually decreases, but as long as it still overlaps with the disturbance interval, the beat frequency point corresponding to beat frequency 3 will continue to generate crosstalk.

[0082] When the left edge of the window moves to the disturbance position At this point, the disturbance interval is exactly outside the window, and the corresponding beat frequency point no longer generates crosstalk. When the window moves to the farthest scan position, the crosstalk situation of all beat frequency points on beat frequency 3 is determined. Therefore, the crosstalk on beat frequency 3 appears from the start of the beat frequency and ends at a certain beat frequency point. The time offsets corresponding to the beat frequency points on beat frequency 3 where crosstalk occurs are as follows:

[0083]

[0084] Therefore, when crosstalk exists on beat frequency 3, the time range is... , Therefore, the right boundary of the disturbance range can be obtained by inverting the time range of crosstalk on beat frequency 3. This allows for secondary positioning of the right boundary of the disturbance range:

[0085]

[0086] Based on the above derivation process, this step only requires phase demodulation and dewinding of all sampling points on beat frequency 3 formed between the (m+1)th and (m+2)th beat frequencies, and considering the crosstalk time Δτ on beat frequency 3. 2LThe right boundary of the disturbance range is located a second time, and its expression is: , among which, U m+1 This indicates the location of the (m+1)th weak grating. Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. Indicates the pulse width. This indicates the time of crosstalk in the beat frequency signal formed between the position of the (m+1)th weak grating and the position of the (m+2)th weak grating.

[0087] The final positioning disturbance range is obtained by combining the left and right boundaries of the disturbance range from the secondary positioning. Its expression is: .

[0088] The following analysis will be based on specific experiments:

[0089] The experimental parameters are as follows: the spacing between the weak gratings is 50m, and a sensing unit is formed between two adjacent weak gratings to sense external disturbances. The dual-pulse pulse width is set to 350ns, the sampling rate of the data acquisition card is set to 1GSa / s, and the system adopts a phase-locked dual-pulse structure, as shown in the figure. Figure 1 As shown.

[0090] Due to the sampling rate limitation of the data acquisition card, the beat frequency signal acquired in the actual system is a discrete signal. Therefore, the beat frequency point in the theoretical analysis is characterized by discrete sampling points in this embodiment.

[0091] The beat frequency signal collected in the experiment is as follows Figure 4 As shown, after performing phase demodulation and dewinding on different sampling points at each beat frequency, the phase response results of the corresponding sampling points of each sensing unit are obtained, as follows: Figure 5 , Figure 6 and Figure 7 As shown.

[0092] Depend on Figure 5 It can be seen that the phase demodulation and unwinding results of this beat frequency have obvious phase fluctuations and exhibit obvious sinusoidal distribution characteristics, indicating that the disturbance is located in the sensing unit corresponding to this beat frequency. This beat frequency is denoted as beat frequency 2.

[0093] After determining that the disturbance is located within the sensing unit, to further invert the specific spatial range of the disturbance within that sensing unit, the beat frequency corresponding to the adjacent sensing unit to its left is first analyzed, and this beat frequency is denoted as beat frequency 1. The two-dimensional results of phase demodulation and dewinding at different sampling points on beat frequency 1 are as follows: Figure 6 As shown. By Figure 6 As can be seen, the crosstalk signal begins to appear at a certain sampling point and continues until the beat frequency ends at 1, with a corresponding time range of 80 ns. Based on the quadratic localization expression for the left boundary of the disturbance range: It can be calculated that the left boundary of the disturbance is located 20.3 m to the right of the m-th grating.

[0094] Then, the beat frequency corresponding to the adjacent sensor unit to the right of the sensor unit where the disturbance occurs is analyzed, and this beat frequency is denoted as beat frequency 3. The two-dimensional results of phase demodulation and dewinding at different sampling points on beat frequency 3 are as follows: Figure 7 As shown. By Figure 7 It can be seen that the crosstalk signal starts from the beat frequency 3 and ends at a certain sampling point, with a corresponding time range of 20 ns. Based on the quadratic localization expression for the right boundary of the disturbance range: It can be calculated that the right boundary of the disturbance is located 5.3 m to the left of the (m+1)th grating.

[0095] When the sampling rate is greater than 100MHz, the positioning method of the present invention can achieve positioning resolution. Less than 1m, compared to the spatial resolution of traditional methods Improved positioning resolution times.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for locating the disturbance range based on a distributed weak grating array sensing system, characterized in that, include: The first pulse light and the second pulse light are reflected sequentially to the distributed weak grating array sensing system, and the first pulse light and the second pulse light form a beat frequency signal through the distributed weak grating array. In a distributed weak grating array, a sampling point is selected on the beat frequency signal formed between two adjacent gratings for phase demodulation and dewinding to achieve the initial positioning perturbation range. The initial positioning perturbation range is denoted as [U]. m U m+1 ], where U m U represents the location of the m-th weak grating. m+1 This indicates the location of the (m+1)th weak grating; Based on the initial positioning disturbance range, phase demodulation and dewinding are performed on all sampling points on the beat frequency signal formed between the position of the (m-1)th weak grating and the position of the mth weak grating, and the left boundary of the disturbance range is located by combining the time of crosstalk. Based on the initial positioning of the disturbance range, phase demodulation and dewinding are performed on all sampling points of the beat frequency signal formed between the location of the (m+1)th weak grating and the location of the (m+2)th weak grating, and the right boundary of the disturbance range is located again by combining the time of crosstalk. The final positioning disturbance range is obtained by combining the left and right boundaries of the disturbance range obtained from the secondary positioning.

2. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 1, characterized in that, The distributed weak grating array sensing system includes a narrow-line pulse laser and a pulse signal generator. The narrow-line pulse laser is used to output continuous light. The continuous light is split by a first coupler and then input to a first acousto-optic modulator and a second acousto-optic modulator. The pulse signal generator is used to generate a driving signal with a preset timing relationship to control the working state of the first acousto-optic modulator and the second acousto-optic modulator. Under the action of the driving signal, the first acousto-optic modulator and the second acousto-optic modulator are respectively used to perform time-series modulation on continuous light to generate a first pulse light and a second pulse light respectively; The first and second pulses are combined by the second coupler to form a double-pulse optical signal. The double-pulse optical signal is amplified by an erbium-doped fiber amplifier and then fed into a distributed weak grating array through a circulator. The distributed weak grating array generates a beat frequency signal on the amplified double-pulse optical signal. The beat frequency signal is fed back to the circulator and then input to a photodetector. The photodetector converts the beat frequency signal into an electrical signal. The electrical signal is digitally acquired by a data acquisition card and then transmitted to an external computing system.

3. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 2, characterized in that, The distributed weak light grating array includes multiple weak light gratings arranged in sequence, and two adjacent weak light gratings constitute a sensing unit.

4. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 3, characterized in that, Each of the sensing units corresponds to a beat frequency signal. The process of forming the beat frequency signal includes: in each sensing unit, the first pulse light is reflected by the rear weak grating and returns to the front weak grating. At this time, the second pulse light is reflected by the front weak grating, and the two reflected lights interfere with each other at the front weak grating to form a beat frequency signal.

5. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 1, characterized in that, The emission time interval between the first pulse light and the second pulse light satisfies the following expression: ； in, This indicates the time interval between the emission of the first and second pulses of light. This represents the effective refractive index of a distributed weak grating array. This represents the grating spacing in a distributed weak grating array. This represents the speed of light in a vacuum.

6. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 5, characterized in that, The first pulse and the second pulse have the same pulse width and satisfy the following expression: ； in, Indicates the pulse width. This represents the effective refractive index of a distributed weak grating array. This represents the grating spacing in a distributed weak grating array. This represents the speed of light in a vacuum.

7. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 1, characterized in that, In the distributed weak grating array, a sampling point is selected on the beat frequency signal formed between two adjacent gratings for phase demodulation and dewinding to realize that the sampling point in the initial positioning disturbance range is the center point of the beat frequency signal.

8. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 1, characterized in that, The calculation expression for the left boundary of the secondary positioning disturbance range is as follows: , among which, U m This indicates the location of the m-th weak grating. Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. Indicates the pulse width. This indicates the time range during which crosstalk exists between the beat frequency signals formed between the (m-1)th weak grating and the mth weak grating.

9. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 1, characterized in that, The calculation expression for the right boundary of the secondary positioning disturbance range is as follows: , among which, U m+1 This indicates the location of the (m+1)th weak grating. Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. Indicates the pulse width. This represents the time range during which crosstalk exists in the beat frequency signal formed between the positions of the (m+1)th weak grating and the (m+2)th weak grating.

10. The disturbance range localization method based on a distributed weak grating array sensing system according to claim 1, characterized in that, When the sampling rate is greater than 100MHz, the positioning resolution of the final positioning disturbance range Less than 1m, of which, Represents the speed of light in a vacuum. This represents the effective refractive index of a distributed weak grating array. This indicates the sampling rate.

Images