CN108168686B - Dual wavelength distributed fiber optic acoustic sensing system - Google Patents

Abstract

The invention provides a dual-wavelength distributed optical fiber acoustic sensing system which comprises an th narrow-linewidth laser, a second narrow-linewidth laser, a main coupler, an optical isolator, a modulator, an erbium-doped optical fiber amplifier, a circulator, a th optical fiber grating, a second optical fiber grating, a sensing optical fiber, a wavelength division multiplexer, a th Michelson interferometer, a second Michelson interferometer, a th carrier circuit, a second carrier circuit, a th photoelectric detector, a second photoelectric detector, a data acquisition card, a signal processor and a pulse generator.

Description

Dual wavelength distributed fiber optic acoustic sensing system

technical field

The invention relates to the field of distributed optical fiber sensing, in particular to the field of distributed optical fiber sensing for measuring dynamic vibration or acoustic signals.

Background technique

Distributed optical fiber sensing technology is an important branch of optical fiber sensing. Using the phase, polarization, amplitude, wavelength and other sensitive characteristics of light waves when transmitting in optical fibers, the temperature, strain, vibration and Physical quantities such as sound have good application prospects and occupy a major position in the optical fiber sensing market.

According to the sensing principle, distributed optical fiber sensing technology can be divided into two types: based on interference detection and based on backscattering detection technology. The former uses Mach-Zehnder interferometer, Sagnac interferometer and composite structure to obtain relevant position and external physical information through positioning algorithm and demodulation algorithm. The latter uses the polarization, light intensity, frequency shift and phase changes of backscattered light to measure external physical quantities. Common types include phase sensitive optical time domain reflectometry (Φ-OTDR), polarized optical time domain reflectometry (P-OTDR), Brillouin optical time domain reflectometry (B-OTDR), Raman optical time domain reflectometry ( R-OTDR) etc. Among them, Φ-OTDR is suitable for long-distance spatial continuous distributed vibration or acoustic sensing, and has significant advantages in perimeter safety, seismic exploration, pipeline monitoring, etc.

Φ-OTDR technology realizes distributed vibration or acoustic sensing by detecting the phase signal of the back-scattered Rayleigh light in the sensing fiber. When external vibration or sound acts on a certain position of the sensing fiber, the fiber at that position will feel the effect of external stress or strain, causing the fiber to stretch and change the refractive index, which in turn causes the backscattered light to transmit during transmission. The phase changes, so the measurement of external vibration or sound can be realized by detecting the phase change. There are many solutions for distributed fiber optic acoustic sensing systems, such as the distributed fiber optic sensing system based on phase generation carrier technology, which uses phase generation carrier phase demodulation algorithm to realize the measurement of distributed vibration or acoustic signals, and solves the problem of large dynamic range signals. It overcomes the influence of initial phase drift on signal amplitude (Xu Tuanwei et al., Distributed Optical Fiber Sensing System Based on Phase Generation Carrier Technology, Application No. 201410032610.X).

The spatial resolution of the distributed optical fiber sensing system based on the phase-generated carrier technology depends on the interferometer arm length difference, and is also related to the pulse light width. The spatial resolution can be improved by reducing the interferometer arm length difference and the pulse light width, but with the decrease of the pulse light width, the back Rayleigh scattering light intensity will decrease, and the system noise floor will increase. Spatial resolution is closely related to the system signal-to-noise ratio. Pursuing high spatial resolution will lead to poor system noise characteristics, making it difficult to measure weak vibration or acoustic signals.

SUMMARY OF THE INVENTION

(1) Technical problems to be solved

The present disclosure provides a dual-wavelength distributed optical fiber acoustic sensing system to at least partially solve the above-mentioned technical problems.

(2) Technical solutions

According to an aspect of the present disclosure, a dual-wavelength distributed optical fiber acoustic sensing system is provided, including: a first narrow linewidth laser and a second narrow linewidth laser; a main coupler, the input end of which is connected to the first narrow linewidth the output end of the laser and the second narrow linewidth laser; the optical isolator, the input end of which is connected to the output end of the main coupler; the modulator, the input end of which is connected to the output end of the optical isolator; the erbium-doped fiber amplifier, The input end is connected to the output end of the modulator; the a port of the circulator is connected to the output end of the erbium-doped fiber amplifier; the first fiber grating and the second fiber grating, the first fiber grating and the second fiber grating The fiber grating constitutes a fiber grating string, which is connected to the b port of the circulator; the sensing fiber is connected to the c port of the circulator; the input end of the wavelength division multiplexer is connected to the d port of the circulator; a first Michelson interferometer and a second Michelson interferometer, the first and second Michelson interferometers are respectively connected to two output ports of the wavelength division multiplexer; the first carrier circuit and the second carrier circuit, the output end of the first carrier circuit is connected to the electrical interface of the first Michelson interferometer; the output end of the second carrier circuit is connected to the electrical interface of the second Michelson interferometer; the first photodetector, the second photodetector The input port of the first photodetector is connected to the output end of the first Michelson interferometer, and the input port of the second photodetector is connected to the output end of the second Michelson interferometer; the data acquisition card has multiple an input port, respectively connected to the output ends of the first carrier circuit and the second carrier circuit, the output ports of the first photodetector and the second photodetector; and a signal processor, connected to the data acquisition card, used for data acquisition through The data collected by the card realizes the measurement of distributed signals.

In some embodiments of the present disclosure, the first Michelson interferometer includes: a coupler, a first Faraday rotator, a second Faraday rotator, and a first phase modulator, wherein the first couplers are respectively connected to the wave An output end of the demultiplexer, the input end of the first Faraday rotator, the input end of the first phase modulator, the input end of the first photodetector; the output end of the first phase modulator and the second Faraday rotator The input end of the first phase modulator is connected to the output end of the first carrier circuit.

In some embodiments of the present disclosure, the second Michelson interferometer includes: a second coupler, a third Faraday rotator, a fourth Faraday rotator and a second phase modulator, wherein four of the second coupler The ports are respectively connected to an output end of the wavelength division multiplexer, the input end of the third Faraday rotator, the input end of the second phase modulator, the input end of the second photodetector, the output end of the second phase modulator and the first The input end of the four-Faraday rotator is connected, and the electrical interface of the second phase modulator is connected with the output end of the second carrier circuit.

In some embodiments of the present disclosure, the first phase modulator and the second phase modulator include a piezoelectric ceramic tube and a single-mode optical fiber wound outside the tube wall for generating sinusoidal phase modulation.

In some embodiments of the present disclosure, the one-way arm length difference between the first Michelson interferometer and the second Michelson interferometer is different but similar, and the difference between the two is between 1 m and 5 m.

In some embodiments of the present disclosure, the output wavelengths of the first narrow linewidth laser and the second narrow linewidth laser are different, and are respectively consistent with the center wavelengths of the first fiber grating and the second fiber grating.

In some embodiments of the present disclosure, the pulse generator emits a repetitive pulse voltage signal to act on the modulator to generate a pulse light signal, and the pulse width of the pulse voltage signal is 10ns-100ns.

In some embodiments of the present disclosure, the first phase modulator and the second phase modulator are composed of a piezoelectric ceramic tube and a single-mode optical fiber wound outside the tube wall, which are used to generate sinusoidal phase modulation, and the modulation amplitude is 2rad- 4rad.

In some embodiments of the present disclosure, the dual-wavelength distributed optical fiber acoustic sensing system obtains the measurement of dynamic vibration or acoustic signals with high spatial resolution through the difference between two phase signals with different spatial resolutions. The resolution is the difference between the one-way arm lengths of the two Michelson interferometers.

(3) Beneficial effects

As can be seen from the above technical solutions, the present disclosure at least has the following beneficial effects:

Two phase demodulation results with different but similar spatial resolutions are realized by wavelength division multiplexing, and the monitoring of distributed dynamic vibration or acoustic signals with high spatial resolution is obtained by subtracting the two. Since there is no need to reduce the interferometer arm The length difference and pulse light width therefore ensure the low noise characteristics of the system, which in turn reflects the advantages of both high spatial resolution and low noise.

Description of drawings

FIG. 1 is a schematic structural diagram of a dual-wavelength distributed optical fiber acoustic sensing system according to an embodiment of the present disclosure.

FIG. 2 shows the relationship between spatial resolution and spatial sampling resolution in an embodiment of the present disclosure.

3 is a schematic diagram of a phase demodulation result of a disturbance signal by a dual-wavelength distributed optical fiber acoustic sensing system according to an embodiment of the present disclosure.

[Description of Symbols of Main Elements of the Embodiments of the Present Disclosure in the Drawings]

1A, the first narrow linewidth laser; 1B, the second narrow linewidth laser

2. Coupler; 3. Optical isolator

4. Modulator; 5. Erbium-doped fiber amplifier

6. Circulator;

7A, the first fiber grating; 7B, the second fiber grating

8. Sensing fiber; 9. Wavelength division multiplexer

10A, the first coupler; 10B, the second coupler

11A, the first Faraday rotator; 11B, the second Faraday rotator

11C, the third Faraday rotator; 11D, the fourth Faraday rotator

12A, the first phase modulator 12B the second phase modulator

13A first carrier circuit; 13B second carrier circuit

14A, first photodetector and 14B second photodetector

15. Data acquisition card; 16. Signal processor,

17. Pulse generator;

100A, the first Michelson interferometer; 100B, the second Michelson interferometer

Detailed ways

The present disclosure provides a dual-wavelength distributed optical fiber acoustic sensing system, while ensuring its low noise advantage, realizing the monitoring of distributed dynamic vibration or acoustic signals with high spatial resolution and low noise, overcoming the high spatial resolution and high spatial resolution of the system. The problem that the signal-to-noise ratio is difficult to take into account at the same time improves the performance of the distributed optical fiber acoustic sensing system.

In order to make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below with reference to the specific embodiments and the accompanying drawings.

Certain embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings, some but not all embodiments of which are shown. Indeed, various embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth in this number; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

In a first exemplary embodiment of the present disclosure, a dual wavelength distributed fiber optic acoustic sensing system is provided. FIG. 1 is a schematic structural diagram of a dual-wavelength distributed optical fiber acoustic sensing system according to a first embodiment of the disclosure. As shown in FIG. 1 , the dual-wavelength distributed optical fiber acoustic sensing system of the present disclosure includes:

Please refer to FIG. 1, the present invention provides a dual-wavelength distributed optical fiber acoustic sensing system, including:

The first narrow linewidth laser 1A, the second narrow linewidth laser 1B, the main main coupler 2, the optical isolator 3, the modulator 4, the erbium-doped fiber amplifier 5, the circulator 6, the first fiber grating 7A, the second fiber Grating 7B, sensing fiber 8, wavelength division multiplexer 9, first Michelson interferometer 100A, second Michelson interferometer 100B, first carrier circuit 13A, second carrier circuit 13B, first photodetector 14A, The second photodetector 14B, the data acquisition card 15 , the signal processor 16 and the pulse generator 17 .

The output ends of the first narrow linewidth laser 1A and the second narrow linewidth laser 1B are connected to the input end of the main coupler 2, the output end of the main coupler 2 is connected to the input end of the optical isolator 3, and the output end of the optical isolator 3 The output end is connected with the input end of the modulator 4, the output end of the modulator 4 is connected with the input end of the erbium-doped fiber amplifier 5, the output end of the erbium-doped fiber amplifier 5 is connected with the a port of the circulator 6, and the b of the circulator 6 is connected. The port is connected to the fiber grating string composed of the first fiber grating 7A and the second fiber grating 7B, the c port of the circulator 6 is connected to the sensing fiber 8, and the d port of the circulator 6 is connected to the input end of the wavelength division multiplexer 9. , the two output ports of the wavelength division multiplexer 9 are respectively connected to the first Michelson interferometer 100A and the second Michelson interferometer 100B, and the input ends of the first Michelson interferometer 100A are connected to the first photodetector. The input port of the second Michelson interferometer 100B is connected to the input port of the second photodetector 14B, and the output ports of the first photodetector 14A and the second photodetector 14B are connected to the data acquisition card 15 The two input ports of the first carrier circuit 13A are connected to the electrical interface of the first Michelson interferometer 100A and an input port of the data acquisition card 15 at the same time, and the output end of the second carrier circuit 13B is simultaneously connected to the second Michelson interferometer. The electrical interface of the interferometer 100B is connected to another input port of the data acquisition card 15 . The output port of the data acquisition card 15 is connected to the signal processor 16 , and the output port of the pulse generator 17 is connected to the electrical interface of the modulator 4 .

Each component of the high spatial resolution dual-wavelength distributed optical fiber acoustic sensing system of this embodiment will be described in detail below.

The first Michelson interferometer 100A includes: a coupler 10A, a first Faraday rotator 11A, a second Faraday rotator 11B and a first phase modulator 12A, and the four ports of the first coupler 10A are respectively connected to the wavelength division multiplexer 9 An output of the first Faraday rotator 11A, the input of the first phase modulator 12A, the input of the first photodetector 14A, the output of the first phase modulator 12A and the second Faraday rotator The input terminal of 11B is connected, and the electrical interface of the first phase modulator 12A is connected to the output terminal of the first carrier circuit 13A.

The second Michelson interferometer 100B includes: a second coupler 10B, a third Faraday rotator 11C, a fourth Faraday rotator 11D and a second phase modulator 12B, and the four ports of the second coupler 10B are respectively connected to wavelength division multiplexing An output of the device 9, the input of the third Faraday rotator 11C, the input of the second phase modulator 12B, the input of the second photodetector 14B, the output of the second phase modulator 12B and the fourth Faraday The input end of the rotator 11D is connected, and the electrical interface of the second phase modulator 12B is connected to the output end of the second carrier circuit 13B.

The one-way arm length difference of the first Michelson interferometer 100A and the second Michelson interferometer 100B is different but similar, and the difference is between 1 m and 5 m.

In the above solution, the output wavelengths of the first narrow linewidth laser 1A and the second narrow linewidth laser 1B are different, and are respectively consistent with the center wavelengths of the first fiber grating 7A and the second fiber grating 7B.

The pulse generator 17 emits a repetitive pulse voltage signal to act on the modulator 4 to generate a pulse light signal, and the pulse width of the pulse voltage signal is between 10ns-100ns.

The two phase modulators are composed of piezoelectric ceramic tubes and single-mode optical fibers wound outside the tube wall to generate sinusoidal phase modulation with a modulation amplitude between 2rad-4rad.

The measurement of dynamic vibration or acoustic signal with high spatial resolution is obtained by the difference of the phase signals with two different spatial resolutions. The spatial resolution of the system is the difference between the lengths of the one-way arms of the two Michelson interferometers.

In this embodiment, the two narrow linewidth lasers use continuous output RIO semiconductor lasers, the linewidth is less than 2kHz, and the operating wavelengths are λ ₁ =1550.12nm and λ ₂ =1546.92nm respectively. Two narrow linewidth lasers with different wavelengths are combined by the main coupler, and then enter the modulator through the optical isolator to generate periodic repetitive pulse light. The pulse width usually adopts a pulse width of 10ns to 100ns. A small pulse width helps to provide high spatial resolution, but a small pulse width corresponds to a small power of Rayleigh scattered light, so the system signal-to-noise ratio is low. A pulse width of 50 ns was used in this system (corresponding to a spatial length of 10 m). The pulse repetition frequency is related to the length of the transmission fiber. When the fiber length is 10km, the maximum pulse repetition frequency is 10kHz. The pulsed light enters the erbium-doped fiber amplifier for optical power amplification after passing through the optical isolator, and the amplified optical signal is filtered by the circulator and the fiber grating. The center wavelength of the fiber grating is consistent with the working wavelength of the narrow linewidth laser, which is 1550.12 nm and 1546.92nm, the 3dB bandwidth is less than 0.2nm, to ensure that the pulsed light entering the sensing fiber does not contain too much spontaneous emission light and to ensure the coherence of the pulsed light.

The pulsed light containing two different wavelengths generates back Rayleigh scattering during the propagation of the sensing fiber, and different Rayleigh scattering light is generated at different positions. When the coherence length of the narrow linewidth laser is greater than the length of the transmission fiber, the Rayleigh scattering light are coherent. The back Rayleigh scattered light of the sensing fiber enters the WDM through the d port of the circulator, and the wavelength division multiplexer separates the two different wavelengths of Rayleigh scattered light into the coupler and the Faraday rotating mirror respectively. Michelson interferometers 100A and 100B composed of phase modulators. The one-way arm length difference of the two Michelson interferometers is different but similar, and the difference between the two is between 1m and 5m.

For the Rayleigh scattered light of each wavelength, the Michelson interferometer has the arm length difference, that is, the delay, so at a certain moment the photodetector receives two Rayleigh scatterings separated by a distance equal to the one-way arm length difference. Therefore, the one-way arm length difference of the interferometer is the spatial resolution of the single-wavelength distributed optical fiber acoustic sensing system. Rayleigh scattered light with wavelengths of 1550.12 nm and 1546.92 nm respectively enters two Michelson interferometers with different arm length differences, wherein the one-way arm length difference of Michelson interferometer 100A is 10 m, and the one-way arm length of Michelson interferometer 100B is 10 m. The difference is 11m, and the corresponding spatial resolutions of the two are 10m and 11m, respectively. The interference signals of the two channels are respectively converted into a time-series electrical signal by the corresponding photodetectors, which are received by the four-channel data acquisition card. The single-channel sampling rate of the data acquisition card is 100MS/s, and the corresponding spatial sampling interval (ie, the spatial sampling resolution of the system) is 1m, so the spatial resolution is much larger than the spatial sampling resolution. For each Michelson interferometer, different times correspond to the double Rayleigh scattered light interference signals at different positions, so it is equivalent to the interference signal of an interferometer moving along the sensing fiber, and the arm length difference of the interferometer is the system space Resolution, each moving distance is the spatial sampling resolution, and the relationship between the spatial resolution and the spatial sampling resolution is shown in Figure 2.

The electrical signal sequence received by the data acquisition card connected to the Michelson interferometer is stored in the signal processor to form a line of data. The number of sampling points (m) per line of data depends on the sampling rate and pulse repetition frequency of the data acquisition card. For the pulse repetition frequency of 10kHz, the sampling rate of the data acquisition card is 100MS/s, and the corresponding sampling points of each line of data are m=10000. After collecting the interference signal sequence generated by n optical pulses, mxn matrix data will be formed. For the interference signal at the same position, since a phase modulator is added to one arm of the Michelson interferometer (the phase modulator consists of a piezoelectric ceramic tube and a single-mode fiber wound outside the tube wall to generate sinusoidal phase modulation), Therefore, there is a phase modulation in the interference signal in the same column of data, and the expression of its interference fringes is:

V=A+Bcos(Ccos(2πf ₀ t)+φ(t))

Among them, A is the DC term related to the interferometer input light intensity, coupler insertion loss, etc., B is related to the interferometer input light intensity, coupler splitting ratio, interferometer extinction ratio, etc., B=kA, k is the interference The fringe visibility, k<1, C is the modulation amplitude of the interferometer, the value is between 2rad and 4rad, f ₀ is the carrier modulation frequency, and φ(t) is the phase signal to be demodulated. Regarding the demodulation of the phase signal φ(t) involved in the above interference fringes, the phase generation carrier demodulation technology is used, which is implemented on a signal processor.

The phase generation carrier demodulation algorithm is as follows: the output signal of the Michelson interferometer is multiplied by the one-fold frequency cos(2πf ₀ t) and double-frequency component cos(4πf ₀ t) of the output electrical signal of the carrier circuit, and then passes through a low-pass The filter obtains the sine term -BJ ₂ (C)sin[φ(t)] and the cosine term -BJ ₁ (C)cos[φ(t)] containing the phase signal φ(t) respectively (where J ₁ (C) ) and J ₂ (C) are the first-order and second-order Bessel functions of the first kind, respectively), and after dividing the two terms, the phase signal with constant coefficients is calculated by the arctangent algorithm [J ₂ (C)/J ₁ (C)]·φ(t), the constant coefficient J ₂ (C)/J ₁ (C) can be determined by calibration, and then the phase signal φ(t) can be obtained. When C=2.63rad, J ₂ (C)/J ₁ (C)=1, the phase signal φ(t) can be obtained directly without constant coefficient calibration, so the phase generation carrier demodulation technology usually chooses C=2.63rad as the optimized value.

Using two light sources with different wavelengths and two Michelson interferometers with different arm length differences, by sharing the sensing fiber, the monitoring of dynamic vibration or acoustic signals with two different spatial resolutions is realized, and their corresponding phase signals are respectively is φ _λ1 (z _k , t _i ), φ _λ2 (z _k , t _i ), z _k represents the position of the sensing fiber, and t _i represents the sampling time of a single-channel signal. Differentiating the two, the phase information of the dual-wavelength distributed optical fiber acoustic sensing system is obtained as:

φ(z _k , t _i )=φ _λ2 (z _k , t _i )-φ _λ1 (z _k , t _i )

Due to differential processing, the spatial resolution of the dual-wavelength distributed optical fiber acoustic sensing system is the difference between the lengths of the one-way arms of the two Michelson interferometers. Since the pulse width is not reduced, the low noise of the system is guaranteed. The advantages.

3 is a schematic diagram of a phase demodulation result of a disturbance signal by a dual-wavelength distributed optical fiber acoustic sensing system according to an embodiment of the present disclosure. For the one-way arm length difference of Michelson interferometer 100A is 10m, and the one-way arm length difference of Michelson interferometer 100B is 11m, the spatial resolution of the dual-wavelength distributed optical fiber acoustic sensing system is 1m. If the sensing fiber is disturbed at a certain position, for the Michelson interferometer 100A (spatial resolution 10m, spatial sampling resolution 1m), there are disturbance signals at 10 consecutive sampling points, while for the Michelson interferometer For 100B (spatial resolution 11m, spatial sampling resolution 1m), there are 11 consecutive sampling points with disturbance signals. By subtracting the phase demodulation results of the two, a disturbance signal with a spatial resolution of 1m (spatial sampling resolution of 1m) can be obtained. The specific relationship is shown in Figure 3.

The present disclosure realizes two phase demodulation results with different but similar spatial resolutions by means of wavelength division multiplexing, and obtains the monitoring of distributed dynamic vibration or acoustic signals with high spatial resolution by subtracting the two, because there is no need to reduce interference The difference in the length of the instrument arm and the width of the pulsed light ensure the low noise of the system, which in turn reflects the advantages of both high spatial resolution and low noise.

Of course, the above hardware structure should also include functional modules such as a power supply module (not shown in the figure), which can be understood by those skilled in the art, and those skilled in the art can also add corresponding functional modules according to functional requirements , which will not be repeated here.

So far, the introduction of the high spatial resolution dual-wavelength distributed optical fiber acoustic sensing system according to the first embodiment of the present disclosure is completed.

So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings. It should be noted that, in the accompanying drawings or the text of the description, the implementations that are not shown or described are in the form known to those of ordinary skill in the technical field, and are not described in detail. In addition, the above definitions of various elements and methods are not limited to various specific structures, shapes or manners mentioned in the embodiments, and those of ordinary skill in the art can simply modify or replace them.

It should also be noted that the directional terms mentioned in the embodiments, such as "up", "down", "front", "rear", "left", "right", etc., only refer to the directions of the drawings, not used to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are denoted by the same or similar reference numbers. Conventional structures or constructions will be omitted when it may lead to obscuring the understanding of the present disclosure.

Unless known to the contrary, the numerical parameters set forth in this specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained from the teachings of the present disclosure. Specifically, all numbers used in the specification and claims to indicate compositional contents, reaction conditions, etc., should be understood as being modified by the word "about" in all cases. In general, the meaning expressed is meant to include a change of ±10% in some embodiments, a change of ±5% in some embodiments, a change of ±1% in some embodiments, and a change of ±1% in some embodiments. Example ±0.5% variation.

Furthermore, the word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

The ordinal numbers such as "first", "second", "third", etc. used in the description and the claims are used to modify the corresponding elements, which themselves do not mean that the elements have any ordinal numbers, nor do they Representing the order of a certain element and another element, or the order in the manufacturing method, the use of these ordinal numbers is only used to clearly distinguish an element with a certain name from another element with the same name.

Furthermore, unless the steps are specifically described or must occur sequentially, the order of the above steps is not limited to those listed above, and may be varied or rearranged according to the desired design. And the above embodiments can be mixed and matched with each other or with other embodiments based on the consideration of design and reliability, that is, the technical features in different embodiments can be freely combined to form more embodiments.

The algorithms and displays provided herein are not inherently related to any particular computer, virtual system, or other device. Various general-purpose systems can also be used with teaching based on this. The structure required to construct such a system is apparent from the above description. Furthermore, this disclosure is not directed to any particular programming language. It is to be understood that various programming languages may be used to implement the disclosures described herein and that the descriptions of specific languages above are intended to disclose the best mode of the disclosure.

The present disclosure may be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. Various component embodiments of the present disclosure may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art should understand that a microprocessor or a digital signal processor (DSP) may be used in practice to implement some or all of the functions of some or all of the components in the related apparatus according to the embodiments of the present disclosure. The present disclosure can also be implemented as apparatus or apparatus programs (eg, computer programs and computer program products) for performing some or all of the methods described herein. Such a program implementing the present disclosure may be stored on a computer-readable medium, or may be in the form of one or more signals. Such signals may be downloaded from Internet sites, or provided on carrier signals, or in any other form.

Those skilled in the art will understand that the modules in the device in the embodiment can be adaptively changed and arranged in one or more devices different from the embodiment. The modules or units or components in the embodiments may be combined into one module or unit or component, and further they may be divided into multiple sub-modules or sub-units or sub-assemblies. All features disclosed in this specification (including accompanying claims, abstract and drawings) and any method so disclosed may be employed in any combination, unless at least some of such features and/or procedures or elements are mutually exclusive. All processes or units of equipment are combined. Each feature disclosed in this specification (including accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Also, in a unit claim enumerating several means, several of these means can be embodied by one and the same item of hardware.

Similarly, it will be appreciated that in the above description of exemplary embodiments of the disclosure, various features of the disclosure are sometimes grouped together into a single embodiment, figure, or its description. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the following claims reflect, disclosed aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the present disclosure.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present disclosure in detail. It should be understood that the above-mentioned specific embodiments are only specific embodiments of the present disclosure, and are not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure should be included within the protection scope of the present disclosure.

Claims (9)

1. A dual-wavelength distributed optical fiber acoustic sensing system, comprising: The first narrow linewidth laser (1A) and the second narrow linewidth laser (1B), the output wavelengths of the first narrow linewidth laser (1A) and the second narrow linewidth laser (1B) are different from those of the first fiber grating respectively. (7A), the center wavelength of the second fiber grating (7B) is consistent; a main coupler (2), the input end of which is connected to the output ends of the first narrow linewidth laser (1A) and the second narrow linewidth laser (1B); an optical isolator (3), the input end of which is connected to the output end of the main coupler (2); a modulator (4), the input of which is connected to the output of the optical isolator (3); an erbium-doped fiber amplifier (5), the input end of which is connected to the output end of the modulator (4); a circulator (6), the a port of which is connected to the output end of the erbium-doped fiber amplifier (5); A first fiber grating (7A) and a second fiber grating (7B), the first fiber grating (7A) and the second fiber grating (7B) form a fiber grating string, and are connected to the b port of the circulator (6) ; a sensing fiber (8), connected to the c port of the circulator (6); a wavelength division multiplexer (9), the input of which is connected to the d port of the circulator (6); The first Michelson interferometer (100A) and the second Michelson interferometer (100B) are respectively connected to the wavelength division multiplexer ( 9) two output ports; A first carrier circuit (13A) and a second carrier circuit (13B), the output end of the first carrier circuit (13A) is connected to the electrical interface of the first Michelson interferometer (100A); the second carrier circuit (13B) The output end is connected to the electrical interface of the second Michelson interferometer (100B); The first photodetector (14A), the second photodetector (14B), the input port of the first photodetector (14A) is connected to the output end of the first Michelson interferometer (100A), the second photodetector ( The input port of 14B) is connected to the output end of the second Michelson interferometer (100B); A data acquisition card (15), which has a plurality of input ports, which are respectively connected to the output ends of the first carrier circuit (13A) and the second carrier circuit (13B), the first photodetector (14A) and the second photodetector (14B) output port; and A signal processor (16), connected to the data acquisition card (15), is used for realizing distributed signal measurement through the data acquired by the data acquisition card (15). 2. The dual-wavelength distributed optical fiber acoustic sensing system according to claim 1, the first Michelson interferometer (100A), comprising: A first coupler (10A), a first Faraday rotator (11A), a second Faraday rotator (11B) and a first phase modulator (12A), wherein the four ports of the first coupler (10A) are respectively connected to the wave An output end of the demultiplexer (9), the input end of the first Faraday rotator (11A), the input end of the first phase modulator (12A), the input end of the first photodetector (14A); the first The output terminal of the phase modulator (12A) is connected to the input terminal of the second Faraday rotator (11B), and the electrical interface of the first phase modulator (12A) is connected to the output terminal of the first carrier circuit (13A). 3. The dual-wavelength distributed optical fiber acoustic sensing system according to claim 2, the second Michelson interferometer (100B), comprising: A second coupler (10B), a third Faraday rotator (11C), a fourth Faraday rotator (11D) and a second phase modulator (12B), wherein the four ports of the second coupler (10B) are respectively connected to the wave An output of the demultiplexer (9), an input of a third Faraday rotator (11C), an input of a second phase modulator (12B), an input of a second photodetector (14B), a second The output terminal of the phase modulator (12B) is connected to the input terminal of the fourth Faraday rotator (11D), and the electrical interface of the second phase modulator (12B) is connected to the output terminal of the second carrier circuit (13B). 4. The dual-wavelength distributed optical fiber acoustic sensing system according to claim 3, wherein the first phase modulator (12A) and the second phase modulator (12B) comprise a piezoelectric ceramic tube and a Single-mode fiber for generating sinusoidal phase modulation. 5. The dual-wavelength distributed optical fiber acoustic sensing system according to claim 3, wherein the one-way arm length difference of the first Michelson interferometer (100A) and the second Michelson interferometer (100B) are different but similar, and the two The difference is between 1m-5m. 6. The dual-wavelength distributed optical fiber acoustic sensing system according to claim 1, wherein the output wavelengths of the first narrow linewidth laser (1A) and the second narrow linewidth laser (1B) are different from those of the first optical fiber, respectively. The center wavelengths of the grating (7A) and the second fiber grating (7B) are the same. 7. The dual-wavelength distributed optical fiber acoustic sensing system according to claim 6, the pulse generator (17) emits a repetitive pulse voltage signal and acts on the modulator (4) to generate a pulsed optical signal, and the pulse width of the pulsed voltage signal is 10ns-100ns. 8. The dual-wavelength distributed optical fiber acoustic sensing system according to claim 3, wherein the first phase modulator (12A) and the second phase modulator (12B) are composed of a piezoelectric ceramic tube and a It is composed of single-mode fiber and is used to generate sinusoidal phase modulation with a modulation amplitude of 2rad-4rad. 9. The dual-wavelength distributed optical fiber acoustic sensing system according to claim 1, obtains the measurement of dynamic vibration or acoustic signal with high spatial resolution by having the difference of the phase signals of two different spatial resolutions, and the system spatial resolution is the difference between the one-way arm lengths of the two Michelson interferometers.

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