Vibration information determination method and multi-wavelength optical fiber vibration interferometer system
Through a multi-wavelength fiber optic vibration interferometer system, a wavelength division multiplexer and a coherent demodulator are used to obtain the phase information of the multi-wavelength laser and solve the waveform-position equations. This solves the problem that a single interferometer cannot locate the vibration position, and achieves the effect of simultaneously determining the vibration position and waveform.
Patent Information
- Application Number
- CN202510939586.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-08
- Publication Date
- 2025-09-12
AI Technical Summary
In the existing technology, a single interferometer can only extract the vibration phase but cannot determine the vibration position, and cannot calculate the position and time of the vibration event through the information carried by a forward laser beam.
A multi-wavelength fiber vibration interferometer system is used. N lasers of different wavelengths are simultaneously injected into the fiber link through a wavelength division multiplexer. Each laser carries information about n vibration events along the fiber link. A coherent demodulation device is used to obtain the phase information of lasers of different wavelengths. The waveform-position equations are solved by a data processing unit to determine the position and waveform of the vibration event.
The method achieves the simultaneous determination of vibration position and vibration waveform through a set of interferometers, solving the "underdetermination" problem of traditional interferometers when the spectra of multiple vibration events overlap. By increasing the number of equations and constraints, it can accurately solve the position and waveform of vibration events.
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Figure CN120628265A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of forward fiber interferometers, and in particular to a vibration information determination method and a multi-wavelength fiber vibration interferometer system. Background Art
[0002] Optical fiber, a critical infrastructure of the modern information society, has been extensively deployed around the world. Distributed fiber-optic vibration sensing technology can be used to monitor vibration events along the fiber-optic network.
[0003] Currently, in the field of distributed fiber-optic vibration sensing, Sagnac interferometers, Mach-Zehnder interferometers, and Michelson interferometers are commonly used to determine vibration information (including vibration position and waveform) along the network. Specifically, these interferometers carry vibration information through forward-transmitted laser light and extract it by demodulating it at the receiving end.
[0004] However, a single interferometer can only extract the vibration phase (i.e., part of the vibration waveform) but cannot determine the vibration position. This is because both the position and time of the vibration event are unknown, equivalent to a two-dimensional unknown quantity. The vibration information carried by a single forward laser beam (equivalent to a known equation) alone cannot be used to solve and locate it.
[0005] Therefore, how to simultaneously determine the vibration position and vibration waveform through a set of interferometers has become a technical problem that needs to be solved urgently. Summary of the Invention
[0006] Based on the above problems, the present application provides a vibration information determination method and a multi-wavelength fiber optic vibration interferometer system, which can simultaneously determine the vibration position and vibration waveform through a set of interferometers.
[0007] The embodiments of this application disclose the following technical solutions:
[0008] In a first aspect, the present application discloses a vibration information determination method, which is applied to a multi-wavelength fiber optic vibration interferometer system, wherein the multi-wavelength fiber optic vibration interferometer system includes a wavelength division multiplexer, an optical fiber link, a coherent demodulation device, and a data processing unit. The method includes:
[0009] The wavelength division multiplexer simultaneously injects N lasers of different wavelengths into the optical fiber link, and each laser carries vibration information of n vibration events along the optical fiber link, where N≥2n, and both N and n are positive integers;
[0010] The coherent demodulation device obtains phase information of the N laser beams with different wavelengths by coherently demodulating the N laser beams with different wavelengths;
[0011] The data processing unit solves a waveform-position equation group according to the phase information of the N laser beams with different wavelengths to determine the vibration positions and vibration waveforms of the n vibration events.
[0012] Optionally, the waveform-position equation group is as follows:
[0013]
[0014] Among them, φ λN The wavelength is λ N The phase information of the laser, φ n is the waveform of the nth vibration event, x n is the distance between the nth vibration event and the coherent demodulation device, v N The wavelength is λ N The propagation speed of the laser in the optical fiber link.
[0015] Optionally, the wavelength division multiplexer is a dense wavelength division multiplexer.
[0016] Optionally, the coherent demodulation method includes an orthogonal demodulation method or a three-port coupler demodulation method.
[0017] Optionally, the wavelength difference between the N lasers of different wavelengths is related to an acquisition rate of an acquisition card.
[0018] In a second aspect, the present application discloses a multi-wavelength fiber vibration interferometer system, the multi-wavelength fiber vibration interferometer system comprising: a wavelength division multiplexer, an optical fiber link, a coherent demodulation device, and a data processing unit;
[0019] The wavelength division multiplexer is used to simultaneously inject N lasers of different wavelengths into the optical fiber link, each laser carrying vibration information of n vibration events along the optical fiber link, N≥2n, and N and n are both positive integers;
[0020] The coherent demodulation device is used to obtain phase information of the N laser beams with different wavelengths by coherently demodulating the N laser beams with different wavelengths;
[0021] The data processing unit is used to solve the waveform-position equation group according to the phase information of the N laser beams with different wavelengths, and determine the vibration positions and vibration waveforms of the n vibration events.
[0022] Optionally, the waveform-position equation group is as follows:
[0023]
[0024] Among them, φ λN The wavelength is λ NThe phase information of the laser, φ n is the waveform of the nth vibration event, x n is the distance between the nth vibration event and the coherent demodulation device, v N The wavelength is λ N The propagation speed of the laser in the optical fiber link.
[0025] Optionally, the wavelength division multiplexer is a dense wavelength division multiplexer.
[0026] Optionally, the coherent demodulation method includes an orthogonal demodulation method or a three-port coupler demodulation method.
[0027] Optionally, the wavelength difference between the N lasers of different wavelengths is related to an acquisition rate of an acquisition card.
[0028] Compared with the existing technology, this application has the following beneficial effects:
[0029] An embodiment of the present application provides a vibration information determination method and a multi-wavelength fiber optic vibration interferometer system. The method is applied to the multi-wavelength fiber optic vibration interferometer system, which includes a wavelength division multiplexer, an optical fiber link, a coherent demodulation device and a data processing unit. The method includes: the wavelength division multiplexer simultaneously injects N lasers of different wavelengths into the optical fiber link, each laser carries vibration information of n vibration events along the optical fiber link, N≥2n, and N and n are both positive integers; the coherent demodulation device obtains phase information of the N lasers of different wavelengths by coherently demodulating the N lasers of different wavelengths; the data processing unit solves a waveform-position equation group according to the phase information of the N lasers of different wavelengths to determine the vibration position and vibration waveform of the n vibration events. Therefore, the vibration information determination method provided in the embodiment of the present application adopts the simultaneous incidence of multi-wavelength lasers, and each wavelength independently carries vibration information. By solving the waveform-position equation group, the number of equations and constraints are increased, thereby fundamentally solving the "underdetermination problem" of traditional single-wavelength or dual-wavelength interferometers that cannot locate when the spectra of multiple vibration events overlap, and can simultaneously determine the vibration position and vibration waveform through a set of interferometers. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.
[0031] Figure 1Schematic diagrams of a Sagnac interferometer, a Mach-Zehnder interferometer, and a Michelson interferometer;
[0032] Figure 2 A schematic diagram of a multi-wavelength fiber vibration interferometer system provided in an embodiment of the present application;
[0033] Figure 3 A flowchart of a vibration information confirmation method provided in an embodiment of the present application. DETAILED DESCRIPTION
[0034] As described above, in the field of distributed optical fiber vibration sensing technology, any one of the Sagnac interferometer, Mach-Zehnder interferometer, and Michelson interferometer is usually used to determine the vibration information (including vibration position and vibration waveform) along the network. Figure 1 The figure shows a schematic diagram of a Sagnac interferometer, a Mach-Zehnder interferometer, and a Michelson interferometer. Specifically, these interferometers carry vibration information through forward-transmitted laser light and then demodulate it at the receiving end to extract the vibration information.
[0035] However, a single interferometer can only extract the vibration phase (i.e., part of the vibration waveform) but cannot determine the vibration position. This is because both the position and time of the vibration event are unknown, equivalent to a two-dimensional unknown quantity. The vibration information carried by a single forward laser beam (equivalent to a known equation) alone cannot be used to solve and locate it.
[0036] After research, the inventors proposed a vibration information determination method and a multi-wavelength fiber optic vibration interferometer system. The method is applied to the multi-wavelength fiber optic vibration interferometer system, which includes a wavelength division multiplexer, an optical fiber link, a coherent demodulation device and a data processing unit. The method includes: the wavelength division multiplexer simultaneously injects N lasers of different wavelengths into the optical fiber link, each laser carries the vibration information of n vibration events along the optical fiber link, N≥2n, and N and n are both positive integers; the coherent demodulation device obtains the phase information of the N lasers of different wavelengths by coherent demodulating the N lasers of different wavelengths; the data processing unit solves the waveform-position equation group according to the phase information of the N lasers of different wavelengths to determine the vibration position and vibration waveform of the n vibration events. Therefore, the vibration information determination method provided in the embodiment of the present application adopts the simultaneous incidence of multi-wavelength lasers, and each wavelength independently carries vibration information. By solving the waveform-position equation group, the number of equations and constraints are increased, thereby fundamentally solving the "underdetermination problem" of traditional single-wavelength or dual-wavelength interferometers that cannot locate when the spectra of multiple vibration events overlap, and can simultaneously determine the vibration position and vibration waveform through a set of interferometers.
[0037] In order to help those skilled in the art better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.
[0038] See also Figure 2 , which is a flow chart of a vibration information confirmation method provided by an embodiment of the present application. The method is applied to a multi-wavelength fiber vibration interferometer system. Figure 3 , which is a schematic diagram of a multi-wavelength fiber vibration interferometer system provided by an embodiment of the present application. Figure 3 It can be seen that the multi-wavelength fiber vibration interferometer system includes a wavelength division multiplexer (WDM), an optical fiber link, a coherent demodulation device and a data processing unit (not shown in the figure).
[0039] S201: A wavelength division multiplexer simultaneously injects N lasers of different wavelengths into an optical fiber link. Each laser carries vibration information of n vibration events along the optical fiber link, where N ≥ 2n, and both N and n are positive integers.
[0040] A wavelength division multiplexer (WDM) is a device that combines optical signals of different wavelengths into a single optical fiber for transmission. In one specific implementation, dense wavelength division multiplexing (DWDM) can be used to simultaneously inject N laser beams of different wavelengths into an optical fiber link. DWDM can multiplex a large number of optical signals of different wavelengths within a relatively narrow wavelength interval (typically 0.8 nm or less), significantly increasing the transmission capacity of optical fibers.
[0041] Each laser beam incident on an optical fiber link independently carries vibration information from n vibration events along its path. These vibration events can originate from various dynamic changes in the fiber's surrounding environment, such as building vibrations, traffic, and fluid flow in underground pipelines. When an optical fiber link is subjected to external vibrations, physical properties such as the fiber's length and refractive index change, causing changes in the vibration information.
[0042] It's understandable that within a fiber optic link, lasers of different wavelengths are affected by dispersion during transmission. Dispersion is a key physical phenomenon in optical fibers. It refers to the fact that, due to the different refractive indices of the fiber material for light signals of different frequencies (or wavelengths), light signals of different wavelengths propagate at different speeds within the fiber. This speed difference causes the light pulse to gradually broaden during transmission, much like a sharp light pulse transforming into a wider, gentler pulse after traveling a certain distance through an optical fiber. However, while dispersion can cause different wavelengths of laser light to propagate at different speeds, it does not affect their ability to carry vibrational information.
[0043] It's important to note that the choice of wavelength difference affects the distinction and independence of the vibration information carried by lasers of different wavelengths. If the wavelength difference is too small, the vibration information carried by lasers of different wavelengths may interfere with each other, resulting in phase aliasing and an inability to accurately restore the vibration position and waveform. Therefore, the wavelength difference between N lasers of different wavelengths can be determined based on the acquisition rate of the acquisition card to ensure that the acquisition card can accurately capture the vibration information carried by each laser at a sufficient rate, thereby enabling effective monitoring and analysis of vibration events.
[0044] S202: The coherent demodulation device performs coherent demodulation on N laser beams with different wavelengths to obtain phase information of the N laser beams with different wavelengths.
[0045] For N laser beams with different wavelengths, the coherent demodulation device needs to perform coherent demodulation on each laser beam separately to extract the phase information of the N laser beams with different wavelengths, including the waveform information and position information of the vibration event.
[0046] In one specific implementation, the coherent demodulation process can be: using N local oscillator lights, each with the same frequency and phase (or with a fixed phase difference) as each laser beam, to mix with the N received laser beams of different wavelengths. After mixing, a low-frequency signal containing the original signal information is generated. By processing this low-frequency signal (including filtering, amplification, and demodulation), the phase information of the N laser beams of different wavelengths can be extracted, including the waveform information and position information of the vibration event.
[0047] It should be noted that, in practical applications, there are many specific implementation methods for coherent demodulation, such as orthogonal demodulation and three-port coupler demodulation. This application does not limit the specific coherent demodulation method.
[0048] S203: The data processing unit solves the waveform-position equation group according to the phase information of N laser beams with different wavelengths to determine the vibration positions and vibration waveforms of the n vibration events.
[0049] For each wavelength of laser light, a waveform-position equation can be established. Taking the case of laser light with four wavelengths and two vibration events (vibration 1 and vibration 2) as an example, formula (1) shows the corresponding waveform-position equation group:
[0050]
[0051] in, They represent the phase information of the laser beams with wavelengths of λ1, λ2, λ3, and λ4 after coherent demodulation. The phase information reflects the changes in the laser beam after being affected by vibration events during transmission. Represents the phase waveform information of vibration 1 and vibration 2, respectively, and is used to describe the waveform characteristics of the vibration event itself. x1 and x2 represent the distance from the location of vibration 1 and vibration 2 to the receiving end (i.e., the coherent demodulation device), respectively, clarifying the location of the vibration event in space. v1, v2, v3, and v4 represent the propagation speed of lasers with wavelengths λ1, λ2, λ3, and λ4 in the optical fiber, respectively. Lasers of different wavelengths may have different propagation speeds in the optical fiber.
[0052] As you can understand, in this system of equations, the left side contains the phase information after coherent demodulation of laser beams of different wavelengths, reflecting the phase change caused by a vibration event during transmission. The right side contains the phase waveform and position information of the vibration event, as well as the laser's propagation speed in the fiber. This system of equations establishes a mathematical relationship between the laser phase information and the waveform and position of the vibration event.
[0053] Subsequently, in order to facilitate the solution of the equations, Fourier transform is performed on both ends of formula (1) to obtain the following formula (2), where the Fourier transform can convert the function in the time domain (or spatial domain) into a function in the frequency domain, thereby simplifying the solution process of the equations:
[0054]
[0055] The unknown quantities are the waveforms Φ1 and Φ2 of vibration 1 and vibration 2, and the distances x1 and x2 between the locations where vibration 1 and vibration 2 occur and the receiving end (i.e., the coherent demodulation device).
[0056] Since there are four equations (corresponding to four wavelengths of laser), after these equations are combined, the matrix inversion or optimization algorithm (such as least squares method, multivariate regression method, etc.) can be used to solve the equation group to obtain the vibration position and vibration waveform of the two vibration events.
[0057] It can be understood that the above formula (2) is a set of waveform-position equations for four laser wavelengths and two vibration events. According to this rule, when there are N lasers of different wavelengths and it is desired to demodulate n vibration events occurring in the optical fiber link, formula (2) can be expanded to the following formula (3):
[0058]
[0059] Among them, φ λN The wavelength is λ N The phase information of the laser, φ n is the waveform of the nth vibration event, x n is the distance between the nth vibration event and the coherent demodulation device, v N The wavelength is λ N The propagation speed of the laser light in the optical fiber link. N needs to be ≥ 2n.
[0060] It is understandable that traditional single-wavelength or dual-wavelength interferometers have limitations when facing multiple vibration events: since the spectra of multiple vibration events will overlap, the number of equations is insufficient and the position and waveform of the vibration event cannot be uniquely determined. There is an "underdetermination problem", that is, there is not enough information to accurately solve all unknown vibration event parameters. The vibration information determination method provided by the embodiment of the present application significantly increases the number of valid equations. When the number of incident laser wavelengths increases, the number of valid equations provided also increases. According to the above formula (3), more vibration events along the optical fiber link can be solved. By increasing the number of equations, the "underdetermination problem" is fundamentally solved, and the vibration position and vibration waveform can be determined simultaneously through a set of interferometers. Moreover, when there are counter-propagating lasers, the propagation speeds of the two in the optical fiber link are v and -v respectively, which can also constitute valid equations, further enhancing the applicability and flexibility of the vibration information determination method in different scenarios.
[0061] It is understandable that the vibration information determination method provided in the embodiment of the present application is not limited to a specific interferometer structure (such as Mach-Zehnder, Michelson or Sagnac), which means that no matter which type of interferometer is used, as long as the multi-wavelength solution principle is satisfied, the corresponding function of the method can be achieved. This characteristic of not relying on a specific interferometer structure brings good compatibility. It enables the vibration information determination method provided in the embodiment of the present application to be seamlessly integrated with the existing fiber optic sensing system without the need for large-scale transformation or adjustment of the system, thereby making full use of the resources and infrastructure of the existing system, thereby avoiding the high costs that may be incurred due to technology upgrades.
[0062] In summary, an embodiment of the present application provides a vibration information determination method and a multi-wavelength fiber optic vibration interferometer system. The method is applied to a multi-wavelength fiber optic vibration interferometer system, and the multi-wavelength fiber optic vibration interferometer system includes a wavelength division multiplexer, an optical fiber link, a coherent demodulation device and a data processing unit. The method includes: the wavelength division multiplexer simultaneously injects N lasers of different wavelengths into the optical fiber link, and each laser carries the vibration information of n vibration events along the optical fiber link, N≥2n, and N and n are both positive integers; the coherent demodulation device obtains the phase information of the N lasers of different wavelengths by coherently demodulating the N lasers of different wavelengths; the data processing unit solves the waveform-position equation group according to the phase information of the N lasers of different wavelengths to determine the vibration position and vibration waveform of the n vibration events. Therefore, the vibration information determination method provided in the embodiment of the present application adopts the simultaneous incidence of multi-wavelength lasers, and each wavelength independently carries vibration information. By solving the waveform-position equation group, the number of equations and constraints are increased, thereby fundamentally solving the "underdetermination problem" of traditional single-wavelength or dual-wavelength interferometers that cannot locate when the spectra of multiple vibration events overlap, and can simultaneously determine the vibration position and vibration waveform through a set of interferometers.
[0063] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components indicated as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. A person of ordinary skill in the art can understand and implement it without expending creative work.
[0064] The above is merely one specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.
Claims
1. A vibration information determination method, characterized in that: Applied to a multi-wavelength optical fiber vibration interferometer system, the multi-wavelength optical fiber vibration interferometer system includes a wavelength division multiplexer, an optical fiber link, a coherent demodulation device and a data processing unit, the method includes: The wavelength division multiplexer simultaneously injects N lasers of different wavelengths into the optical fiber link, and each laser carries vibration information of n vibration events along the optical fiber link, where N≥2n, and both N and n are positive integers; The coherent demodulation device obtains phase information of the N laser beams with different wavelengths by coherently demodulating the N laser beams with different wavelengths; The data processing unit solves a waveform-position equation group according to the phase information of the N laser beams with different wavelengths to determine the vibration positions and vibration waveforms of the n vibration events.
2. The method according to claim 1, characterized in that The waveform-position equations are as follows: Among them, φ λN The wavelength is λ N The phase information of the laser, φ n is the waveform of the nth vibration event, x n is the distance between the nth vibration event and the coherent demodulation device, v N The wavelength is λ N The propagation speed of the laser in the optical fiber link.
3. The method according to claim 1, characterized in that The wavelength division multiplexer is a dense wavelength division multiplexer.
4. The method according to claim 1, wherein The coherent demodulation method includes an orthogonal demodulation method or a three-port coupler demodulation method.
5. The method according to claim 1, wherein The wavelength difference between the N laser beams of different wavelengths is related to the acquisition rate of the acquisition card.
6. A multi-wavelength optical fiber vibration interferometer system, characterized in that: The multi-wavelength optical fiber vibration interferometer system includes: a wavelength division multiplexer, an optical fiber link, a coherent demodulation device and a data processing unit; The wavelength division multiplexer is used to simultaneously inject N lasers of different wavelengths into the optical fiber link, each laser carrying vibration information of n vibration events along the optical fiber link, N≥2n, and N and n are both positive integers; The coherent demodulation device is used to obtain phase information of the N laser beams with different wavelengths by coherently demodulating the N laser beams with different wavelengths; The data processing unit is used to solve the waveform-position equation group according to the phase information of the N laser beams with different wavelengths, and determine the vibration positions and vibration waveforms of the n vibration events.
7. The system according to claim 6, characterized in that The waveform-position equations are as follows: Among them, φ λN The wavelength is λ N The phase information of the laser, φ n is the waveform of the nth vibration event, x n is the distance between the nth vibration event and the coherent demodulation device, v N The wavelength is λ N The propagation speed of the laser in the optical fiber link.
8. The system according to claim 6, characterized in that The wavelength division multiplexer is a dense wavelength division multiplexer.
9. The system according to claim 6, wherein: The coherent demodulation method includes an orthogonal demodulation method or a three-port coupler demodulation method.
10. The system according to claim 6, wherein: The wavelength difference between the N laser beams of different wavelengths is related to the acquisition rate of the acquisition card.