Distributed phase detection device and method with large dynamic measurement range

Abstract

The invention provides a distributed phase detection device and method with a large dynamic measurement range. The device comprises a first laser, a second laser, a first pulse modulation and frequency shift module, a second frequency shift module and a receiving module, wherein the first laser is used for generating a signal with the frequency of 0; the second laser is used for generating a signal with frequency; the first pulse modulation and frequency shift module is used for generating a detection light pulse containing two frequencies based on the signal with the frequency of 0 and the signal with the frequency of 0; the detection light pulse is used for being injected into a to-be-detected optical fiber to generate Rayleigh backscattered light with two frequencies; the second frequency shift module is used for generating a signal containing the frequency Y. based on the signal containing the frequency Y. The receiving module is used for receiving Rayleigh backscattered light with two frequencies, a signal with the frequency of 1, and a beat frequency signal of the signal with the frequency of 1; the beat frequency signal is used for phase detection; the receiving module comprises a coherent receiver and a data acquisition module. According to the device provided by the embodiment of the invention, two sets of coherent receivers and acquisition modules required in a traditional dual-wavelength scheme are simplified into one set, and the hardware complexity and equipment cost of the system are remarkably reduced while an equivalent measurement function is maintained.

Description

Technical Field

[0001] The present invention relates to the technical field of phase detection, and in particular to a distributed phase detection device and method with a large dynamic measurement range. Background Art

[0002] Rayleigh scattering-based phase-sensitive optical time-domain reflectometry (Φ-OTDR) is a distributed multipath interferometer with high sensitivity. By measuring the phase change of coherent Rayleigh scattered light signals and exploiting the linear relationship between external disturbances and the Rayleigh scattered light phase, Φ-OTDR can quantitatively analyze the spatial distribution of temperature or strain. It has become a key technology for distributed acoustic sensing (DAS), distributed hydrophone arrays, and seismic monitoring, and has garnered widespread attention in academia and industry in recent years.

[0003] In related technologies, the phase of optical signals in Φ-OTDR systems is typically obtained through IQ demodulation, calculated using the arctangent (I / Q) function. Researchers have proposed a dual-wavelength detection scheme that uses two different wavelength light sources to obtain phase difference information. However, this solution requires two independent coherent receivers and corresponding data acquisition modules, significantly increasing system complexity and cost. Summary of the Invention

[0004] The present invention provides a distributed phase detection device and method with a large dynamic measurement range. By introducing local oscillator optical frequency shifting technology, the two sets of coherent receivers and acquisition modules required in the traditional dual-wavelength solution are simplified to one set. While maintaining equivalent measurement functions, the system's hardware complexity and equipment cost are significantly reduced.

[0005] The present invention provides a distributed phase detection device with a large dynamic measurement range, comprising: A first laser, a second laser, a first pulse modulation and frequency shift module, a second frequency shift module and a receiving module; wherein, The first laser is used to generate a frequency of The second laser is used to generate a signal with a frequency of signal; The first pulse modulation and frequency shift module is used to The signal and frequency are The signal is used to generate a detection light pulse containing two frequencies; the detection light pulse is used to inject into the optical fiber to be tested to generate Rayleigh backscattered light of two frequencies; The second frequency shift module is used to The signal generation includes a frequency of signal; The receiving module is used to receive the Rayleigh backscattered light of the two frequencies and the The signal frequency is The beat frequency signal of the signal is used for phase detection; the receiving module includes a coherent receiver and a data acquisition module.

[0006] According to a distributed phase detection device with a large dynamic measurement range provided by the present invention, the driving signal of the first pulse modulation and frequency shift module is a single pulse signal.

[0007] According to a distributed phase detection device with a large dynamic measurement range provided by the present invention, when the driving signal of the first pulse modulation and frequency shift module is a single pulse signal, the range of the phase detection includes: in, Indicates the minimum measurable phase.

[0008] According to a distributed phase detection device with a large dynamic measurement range provided by the present invention, the driving signal of the first pulse modulation and frequency shift module is a frequency division multiplexing (FDM) signal.

[0009] According to a distributed phase detection device with a large dynamic measurement range provided by the present invention, when the driving signal of the first pulse modulation and frequency shift module is an FDM signal, the range of the phase detection includes: in, Indicates the minimum measurable phase.

[0010] The present invention also provides a distributed phase detection method, comprising the following steps: Get the Rayleigh backscattered light corresponding to the two frequencies of the detection light and the frequency The signal frequency is The beat frequency signal of the signal; wherein the frequency is The signal is the second frequency shift module based on the frequency The two frequencies of Rayleigh backscattered light are first pulse modulated and the frequency shift module is based on the frequency The signal and frequency are The signal is generated by The signal is generated by the first laser; the frequency is The signal is generated by the second laser; Phase detection is performed based on the beat frequency signal.

[0011] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, any of the above-described distributed phase detection methods is implemented.

[0012] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which implements any of the above-described distributed phase detection methods when executed by a processor.

[0013] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the distributed phase detection method as described above is implemented.

[0014] The invention provides a distributed phase detection device and method with a large dynamic measurement range, wherein the second frequency shift module is based on a frequency of The signal generation includes a frequency of The signal is then After the local oscillator light is combined with the Rayleigh backscattered light, the obtained beat signal will be generated at the intermediate frequency. and Two spectral components are formed at the two locations, representing the scattered information of the two different-frequency probe lights. This allows all the information required for dual-wavelength detection to be acquired using only one coherent receiver and one data acquisition module, resolving the high system complexity and high cost associated with the existing dual-wavelength detection schemes that require two independent coherent receivers and data acquisition modules. In other words, by introducing local oscillator optical frequency shifting technology, this application simplifies the two coherent receivers and acquisition modules required in traditional dual-wavelength schemes into a single set, significantly reducing the system's hardware complexity and equipment cost while maintaining equivalent measurement functionality. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 This is one of the schematic diagrams of the distributed phase detection with a large dynamic measurement range provided by the present invention.

[0017] Figure 2 This is the second schematic diagram of the distributed phase detection with a large dynamic measurement range provided by the present invention.

[0018] Figure 3 It is a schematic diagram of the driving signal provided by the present invention. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0020] The following combination Figure 1-Figure 3 The present invention describes a distributed phase detection device and method with a large dynamic measurement range.

[0021] In order to facilitate a clearer understanding of the technical solutions of the various embodiments of the present application, some technical contents related to the various embodiments of the present application are first introduced.

[0022] Optical fiber has the advantages of small size, light weight, easy bending, low loss, good resistance to electromagnetic interference, and good radiation resistance. Distributed fiber optic sensing uses optical fiber as a medium and utilizes natural scattering processes in optical fiber, such as Rayleigh, spontaneous Raman, and spontaneous / stimulated Brillouin scattering, to achieve sensing of physical quantities such as temperature and strain. Among them, the Rayleigh scattering-based phase-sensitive optical time-domain reflectometer (Φ-OTDR) is a distributed multipath interferometer with high sensitivity. By measuring the phase change of the coherent Rayleigh scattered light signal and utilizing the linear relationship between external disturbances and the Rayleigh scattered light phase, Φ-OTDR can quantitatively analyze the spatial distribution of temperature or strain. It has become a key technical means for realizing distributed acoustic field sensing (DAS), distributed hydrophone arrays, and seismic monitoring, and has garnered widespread attention from academia and industry in recent years.

[0023] In Φ-OTDR systems, the phase of optical signals is typically acquired through IQ demodulation, calculated using the arctangent (I / Q) function. However, in the actual demodulation process, if the measured phase exceeds the valid range of the arctangent function (-π, π), the demodulation result will be erroneous, causing the output phase value to be incorrectly wrapped within the (-π, π) interval. This phenomenon severely limits the dynamic range of strain measurable by the Φ-OTDR system. To address this issue, researchers have proposed a dual-wavelength detection scheme that utilizes phase difference information obtained from two different wavelength light sources to expand the system's measurable dynamic strain range. However, this scheme requires two independent coherent receivers and corresponding data acquisition modules, significantly increasing system complexity and cost. Furthermore, this scheme is susceptible to measurement noise, which can cause the minimum measurable strain value to exceed π, creating a "blind zone" between π and the minimum measurable strain value. This issue not only reduces measurement accuracy but also limits the application of this technology in practical engineering scenarios.

[0024] Another technical approach is to use frequency division multiplexing (FDM) technology to expand the measurable dynamic strain range. The core idea is to The dynamic measurement range can be increased by 100% by injecting probe pulses of different frequencies into the optical fiber at equal intervals. However, this method The value of is strictly limited by the modulator bandwidth, so the improvement of its dynamic range is still limited, which makes it difficult to meet the actual needs of large-scale strain measurement.

[0025] For example, Figure 1 As shown in the system structure of the traditional dual-wavelength detection scheme, the frequencies are and Laser 1 and Laser 2 are each divided into two optical signals through coupler 1 and coupler 2: The downlink light is used as local oscillator light 1 and local oscillator light 2 for coherent reception; the uplink light is combined by coupler 3 and then pulse modulated and frequency shifted to generate a and The probe light pulse is then amplified to the required optical power level by an optical amplifier and injected into the fiber under test through a circulator. Therefore, in the traditional solution, the returned Rayleigh backscattered light needs to be split into two beams by coupler 4, and then beat with two local oscillator lights of different frequencies. The respective Rayleigh backscattered signals are then acquired through two independent coherent receivers and data acquisition modules, which greatly increases the system complexity and cost.

[0026] In the Φ-OTDR system, the distance between two optical fiber positions ( ) phase difference It can be expressed as: in is the frequency of the probe light, is the effective refractive index of the optical fiber, is the speed of light in a vacuum. In the traditional unwrap algorithm, the phase interval between two adjacent measurements cannot exceed ±π, otherwise it will lead to phase demodulation errors.

[0027] The core principle of the dual-wavelength detection scheme is to obtain the phase difference of two detection lights with different frequencies ( and ), and perform second-order difference processing to obtain the corrected phase difference : because ,therefore Much smaller than , which allows the system to recover To obtain a large dynamic range of strain measurement capability. Theoretically, the expansion factor of the phase measurement dynamic range is , this proportional factor can be flexibly controlled by adjusting the frequency difference between the two lasers.

[0028] In summary, the system structure of the traditional dual-wavelength detection solution requires two independent coherent receiver systems and corresponding data acquisition modules, which not only increases the hardware complexity of the system, but also increases the overall cost of the equipment, limiting the widespread application of the technology.

[0029] Figure 2 Schematic diagram of a distributed phase detection device with a large dynamic measurement range provided by the present invention. Figure 2 As shown, the device includes the following: A first laser, a second laser, a first pulse modulation and frequency shift module, a second frequency shift module and a receiving module; wherein, The first laser is used to generate a frequency of The second laser is used to generate a signal with a frequency of signal; The first pulse modulation and frequency shift module is used to The signal and frequency are The signal is used to generate a probe light pulse containing two frequencies; the probe light pulse is used to inject into the optical fiber to be tested to generate Rayleigh backscattered light of two frequencies; The second frequency shift module is used to The signal generation includes a frequency of signal; The receiving module is used to receive two frequencies of Rayleigh backscattered light and a frequency of The signal frequency is The beat frequency signal of the signal is used for phase detection; the receiving module includes a coherent receiver and a data acquisition module.

[0030] Specifically, the system structure of the traditional dual-wavelength detection solution requires two independent coherent receiver systems and corresponding data acquisition modules, which not only increases the hardware complexity of the system, but also increases the overall cost of the equipment, limiting the widespread application of the technology.

[0031] In order to solve the above problems, the first pulse modulation and frequency shift module in the embodiment of the present application is based on the frequency The signal and frequency are The signal generated contains and The two-frequency detection light pulse is then amplified by an optical amplifier to the required optical power level and injected into the optical fiber under test through a circulator to generate Rayleigh backscattered light of two frequencies. The signal generation includes a frequency of The signal is then The local oscillator light 1 is combined by the coupler 4 and then beats with the Rayleigh backscattered light.

[0032] With this design, the obtained beat frequency signal will be at the intermediate frequency and Two spectral components are formed at the two locations, representing the scattered information of the two different frequency probe lights. Combined with bandpass filtering technology in digital signal processing, the system can effectively separate the two Rayleigh backscattered signals, thereby acquiring all the information required for dual-wavelength detection using only one coherent receiver and one data acquisition module. This solves the high system complexity and high cost caused by the need for two independent coherent receivers and data acquisition modules in existing dual-wavelength detection solutions, and explores a new dynamic strain measurement solution with a simplified structure.

[0033] In the above embodiment, the second frequency shift module is based on the frequency The signal generation includes a frequency of The signal is then After the local oscillator light is combined with the Rayleigh backscattered light, the obtained beat signal will be generated at the intermediate frequency. and Two spectral components are formed at the two locations, representing the scattered information of the two different-frequency probe lights. This allows all the information required for dual-wavelength detection to be acquired using only one coherent receiver and one data acquisition module, resolving the high system complexity and high cost associated with the existing dual-wavelength detection schemes that require two independent coherent receivers and data acquisition modules. In other words, by introducing local oscillator optical frequency shifting technology, this application simplifies the two coherent receivers and acquisition modules required in traditional dual-wavelength schemes into a single set, significantly reducing the system's hardware complexity and equipment cost while maintaining equivalent measurement functionality.

[0034] In some embodiments, the driving signal of the first pulse modulation and frequency shift module is a single pulse signal.

[0035] Specifically, the driving signal of the first pulse modulation and frequency shift module in the embodiment of the present application is a single pulse signal , so that the first pulse modulation and frequency shift module is based on the frequency The signal and frequency are The signal generated contains and The two-frequency detection light pulse is then amplified by an optical amplifier to the required optical power level and injected into the optical fiber under test through a circulator to generate Rayleigh backscattered light of two frequencies. This method is simple and convenient to implement, and is convenient for quickly and accurately generating and The beat frequency signal containing two spectral components is detected and phase detection is performed.

[0036] In some embodiments, when the driving signal of the first pulse modulation and frequency shift module is a single pulse signal, the range of phase detection includes: in, Indicates the minimum measurable phase.

[0037] Specifically, the driving signal of the first pulse modulation and frequency shift module is a single pulse signal. In practical applications, the system measurement performance will be affected by noise. Assume that the minimum measurable phase due to noise interference is , then the phase detection range in this application is .

[0038] In some embodiments, the driving signal of the first pulse modulation and frequency shift module is a frequency division multiplexing (FDM) signal.

[0039] Specifically, the driving signal of the first pulse modulation and frequency shift module is a single pulse signal. In the case of , the minimum measurable phase due to noise interference is , the range of phase detection is When the noise is large or the scale factor When it is larger, it may appear Greater than situation, which will result in In order to solve the above problems, such as Figure 3 As shown, the present application further combines FDM technology to adjust the driving signal of the first pulse modulation and frequency shift module to a frequency division multiplexing FDM signal.

[0040] In some embodiments, when the driving signal of the first pulse modulation and frequency shift module is an FDM signal, the range of phase detection includes: in, Indicates the minimum measurable phase.

[0041] Specifically, in the embodiment of the present application, the driving signal of the first pulse modulation and frequency shift module is adjusted to a frequency division multiplexing FDM signal, that is, by injecting FDM pulses into the optical fiber at equal intervals, the dynamic range can be effectively expanded. times, extending the system's measurement range to By rationally designing parameters With the scale factor The value of Greater than , which can be achieved from arrive Full range dynamic measurement without blind spots. That is, this application creatively realizes the arrive The full-range continuous measurement capability enables the system to simultaneously monitor small strain changes and large dynamic strain events, greatly improving the applicability of distributed fiber optic sensing systems in extreme environments.

[0042] The device of the above embodiment, because the dual-wavelength detection scheme is affected by measurement noise, may cause its minimum measurable strain value to be higher than π, thereby forming a measurement "blind spot" between π and the minimum measurable strain value, limiting its practicality in application scenarios requiring full-range accurate monitoring. By further combining FDM technology, the present application adjusts the drive signal of the first pulse modulation and frequency shift module to a frequency-division multiplexing FDM signal. This can effectively overcome the measurement "blind spot" problem caused by noise interference in the prior art, as well as the limitation of frequency-division multiplexing technology that is limited by bandwidth and cannot achieve large-scale strain measurement, thereby realizing a technical solution for continuous monitoring of the entire range from small strain to large strain.

[0043] Exemplarily, an embodiment of the present application further provides a distributed phase detection method, which is applied to the above-mentioned distributed phase detection device with a large dynamic measurement range, including: Get the Rayleigh backscattered light corresponding to the two frequencies of the detection light and the frequency The signal frequency is The beat frequency signal of the signal; where the frequency is The signal is the second frequency shift module based on the frequency The two frequencies of Rayleigh backscattered light are the first pulse modulation and the frequency shift module is based on the frequency The signal and frequency are The signal generated by The signal is generated by the first laser; the frequency is The signal is generated by the second laser; Phase detection is performed based on the beat frequency signal.

[0044] Specifically, in the embodiment of the present application, the first pulse modulation and frequency shift module is based on a frequency of The signal and frequency are The signal generated contains and The two-frequency detection light pulse is then amplified by an optical amplifier to the required optical power level and injected into the optical fiber under test through a circulator to generate Rayleigh backscattered light of two frequencies. The signal generation includes a frequency of The signal is then The local oscillator light 1 is combined by the coupler 4 and then beats with the Rayleigh backscattered light.

[0045] With this design, the obtained beat frequency signal will be at the intermediate frequency and Two spectral components are formed at the two wavelengths, representing the scattered information of the two different frequency probe lights. Combined with bandpass filtering technology in digital signal processing, the system can effectively separate the two Rayleigh backscattered signals, thereby completing the acquisition of all the information required for dual-wavelength detection using only one coherent receiver and one data acquisition module. This solves the high system complexity and high cost caused by the need for two independent coherent receivers and data acquisition modules in existing dual-wavelength detection solutions, and explores a new dynamic strain measurement solution with a simplified structure.

[0046] In the above embodiment, the second frequency shift module is based on the frequency The signal generation includes a frequency of The signal is then After the local oscillator light is combined with the Rayleigh backscattered light, the obtained beat signal will be generated at the intermediate frequency. and Two spectral components are formed at the two locations, representing the scattered information of the two different-frequency probe lights. This allows all the information required for dual-wavelength detection to be acquired using only one coherent receiver and one data acquisition module, resolving the high system complexity and high cost associated with the existing dual-wavelength detection schemes that require two independent coherent receivers and data acquisition modules. In other words, by introducing local oscillator optical frequency shifting technology, this application simplifies the two coherent receivers and acquisition modules required in traditional dual-wavelength schemes into a single set, significantly reducing the system's hardware complexity and equipment cost while maintaining equivalent measurement functionality.

[0047] On the other hand, the present invention also provides a computer program product, the computer program product includes a computer program, the computer program can be stored on a non-transitory computer-readable storage medium, and when the computer program is executed by a processor, the computer can execute the distributed phase detection method provided by the above methods, the method comprising: obtaining the Rayleigh backscattered light corresponding to the two frequencies of the detection light and the frequency of The signal frequency is The beat frequency signal of the signal; where the frequency is The signal is the second frequency shift module based on the frequency The two frequencies of Rayleigh backscattered light are the first pulse modulation and the frequency shift module is based on the frequency The signal and frequency are The signal generated by The signal is generated by the first laser; the frequency is The signal is generated by the second laser; phase detection is performed based on the beat frequency signal.

[0048] In another aspect, the present invention further provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program is executed by a processor to implement the distributed phase detection method provided by the above methods, the method comprising: obtaining Rayleigh backscattered light corresponding to the two frequencies of detection light and the frequency of The signal frequency is The beat frequency signal of the signal; where the frequency is The signal is the second frequency shift module based on the frequency The two frequencies of Rayleigh backscattered light are the first pulse modulation and the frequency shift module is based on the frequency The signal and frequency are The signal generated by The signal is generated by the first laser; the frequency is The signal is generated by the second laser; phase detection is performed based on the beat frequency signal.

[0049] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0050] Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented using software plus a necessary general-purpose hardware platform, or of course, hardware. Based on this understanding, the essence of the above technical solution, or the portion that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, or an optical disk, and includes a number of instructions for causing a computer device (such as a personal computer, server, or network device) to execute the methods described in each embodiment or certain portions of the embodiments.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A distributed phase detection device with a large dynamic measurement range, characterized in that: include: A first laser, a second laser, a first pulse modulation and frequency shift module, a second frequency shift module and a receiving module; wherein, The first laser is used to generate a frequency of signal; The second laser is used to generate a frequency of signal; The first pulse modulation and frequency shift module is used to The signal and frequency are The signal is used to generate a detection light pulse containing two frequencies; the detection light pulse is used to inject into the optical fiber to be tested to generate Rayleigh backscattered light of two frequencies; The second frequency shift module is used to The signal generation includes a frequency of signal; The receiving module is used to receive the Rayleigh backscattered light of the two frequencies and the The signal frequency is The beat frequency signal of the signal is used for phase detection; the receiving module includes a coherent receiver and a data acquisition module.

2. The distributed phase detection device with a large dynamic measurement range according to claim 1, characterized in that: The driving signal of the first pulse modulation and frequency shift module is a single pulse signal.

3. The distributed phase detection device with a large dynamic measurement range according to claim 2, characterized in that: When the driving signal of the first pulse modulation and frequency shift module is a single pulse signal, the range of the phase detection includes: in, Indicates the minimum measurable phase.

4. The distributed phase detection device with a large dynamic measurement range according to claim 1, characterized in that: The driving signal of the first pulse modulation and frequency shift module is a frequency division multiplexing (FDM) signal.

5. The distributed phase detection device with a large dynamic measurement range according to claim 4, characterized in that: When the driving signal of the first pulse modulation and frequency shift module is an FDM signal, the range of the phase detection includes: in, Indicates the minimum measurable phase.

6. A distributed phase detection method, applied to the distributed phase detection device with a large dynamic measurement range as claimed in any one of claims 1 to 5, characterized in that: include: Get the Rayleigh backscattered light corresponding to the two frequencies of the detection light and the frequency The signal frequency is The beat frequency signal of the signal; wherein the frequency is The signal is the second frequency shift module based on the frequency The two frequencies of the detection light are first pulse modulation and frequency shift module based on the frequency of The signal and frequency are The signal is generated by The signal is generated by the first laser; the frequency is The signal is generated by the second laser; Phase detection is performed based on the beat frequency signal.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the distributed phase detection method according to claim 6 is implemented.

8. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the distributed phase detection method according to claim 6 is implemented.

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