CN113124994A - Distributed vibration sensing demodulation method based on weak signal-to-noise ratio signal - Google Patents
Distributed vibration sensing demodulation method based on weak signal-to-noise ratio signal Download PDFInfo
- Publication number
- CN113124994A CN113124994A CN202110563666.8A CN202110563666A CN113124994A CN 113124994 A CN113124994 A CN 113124994A CN 202110563666 A CN202110563666 A CN 202110563666A CN 113124994 A CN113124994 A CN 113124994A
- Authority
- CN
- China
- Prior art keywords
- signal
- vibration
- optical fiber
- light
- carrying
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01H—MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC OR INFRASONIC WAVES
- G01H9/00—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means
- G01H9/004—Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means using fibre optic sensors
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
- G06F17/14—Fourier, Walsh or analogous domain transformations, e.g. Laplace, Hilbert, Karhunen-Loeve, transforms
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Mathematical Physics (AREA)
- Pure & Applied Mathematics (AREA)
- Mathematical Optimization (AREA)
- Mathematical Analysis (AREA)
- Computational Mathematics (AREA)
- Data Mining & Analysis (AREA)
- Theoretical Computer Science (AREA)
- Algebra (AREA)
- Databases & Information Systems (AREA)
- Software Systems (AREA)
- General Engineering & Computer Science (AREA)
- Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
Abstract
The invention belongs to the field of distributed optical fiber vibration sensing, and provides a distributed vibration sensing demodulation method based on a weak signal-to-noise ratio signal. The method comprises the steps of firstly carrying out block filtering processing on heterodyne coherent beat frequency signals acquired by a distributed optical fiber sensing system, then carrying out segmented interpolation processing on data, then carrying out Fourier transform, extracting amplitude and phase information of intermediate frequency signals according to intermediate frequency signals of an acousto-optic modulator, carrying out autocorrelation processing on the amplitude and the phase, then carrying out cross-correlation processing, and finally carrying out spectrum analysis, thus realizing effective demodulation on vibration signals under weak signal-to-noise ratio signals and increasing the sensitivity and accuracy of signal demodulation.
Description
Technical Field
The invention belongs to the technical field of optical fiber sensing, and particularly relates to a distributed vibration sensing demodulation method based on a weak signal-to-noise ratio signal.
Background
With the rapid development of the era of the internet of things, the importance of information perception is more and more reflected in various aspects of social production, the optical fiber sensing technology is one of the fastest developing branches of the modern sensing technologies, the optical fiber sensor rapidly becomes a hot tide of research of people by virtue of the advantages of electromagnetic interference resistance, corrosion resistance, small loss, high sensitivity, high response speed, low cost and the like, and compared with the situation that the traditional electrical scheme is still weak in vibration detection under various special environments, the optical fiber sensing technology has a wider application prospect in detection.
Vibration is one of the carriers of information with which a human can obtain much information. The optical fiber vibration sensing technology is one of optical fiber sensing technologies, the physical quantity monitored by the optical fiber vibration sensing technology is optical fiber vibration caused by an external target, light is used as an information carrier, optical fibers are used as a propagation medium, and a novel sensing technology for acquiring useful information hidden in the optical fibers by analyzing optical signals in the sensing optical fibers is adopted. The distributed optical fiber vibration sensing technology is widely applied to safety monitoring, rock deformation measurement, road and site measurement and perimeter security monitoring of buildings such as bridges, the distributed optical fiber vibration sensing technology can also be applied to the aerospace field to form a distributed intelligent sensing network for monitoring the internal mechanical performance and the external environment of an aircraft in real time, meanwhile, the distributed optical fiber vibration sensing technology can monitor leakage of pipelines and vibration signals transmitted by seismic waves reflected under the stratum, the vibration signals can effectively reflect invisible underground information, and information carried by the vibration signals in various occasions has important application to social life of people at present.
Especially for a phase-sensitive optical time domain reflectometer (phi-OTDR), compared with other optical fiber distributed sensing technologies, the distributed optical time domain reflectometer can perform distributed multi-point monitoring on weak signals in a long distance range, and uses a narrow line width light source with high coherence to modulate and generate short pulse width pulses, so that the spatial resolution is further improved. At present, in a distributed optical fiber vibration sensing technology based on phase sensitive optical time domain reflection, there are generally three ways to realize the demodulation of a vibration signal: the method is characterized in that a direct intensity demodulation method is adopted, backward Rayleigh scattered light signals are directly detected and collected, adjacent difference is carried out on scattered light interference signals obtained by sampling to detect vibration signals, the method can only simply judge the position information of vibration points, and the related amplitude and frequency information of vibration is difficult to collect; secondly, a heterodyne coherent amplitude demodulation method is adopted, wherein after Rayleigh scattering light interference signals and local coherent light signals are subjected to beat frequency, beat frequency signals are collected by a collection card, amplitude signals are extracted from the beat frequency signals and subjected to adjacent difference to realize the judgment of vibration signals, and the scheme can accurately collect position and frequency information related to the vibration signals and is difficult to collect amplitude information related to the vibration signals; thirdly, a heterodyne coherent phase demodulation method, after performing beat frequency on Rayleigh scattering light interference signals and local coherent light signals, acquiring beat frequency signals by an acquisition card, extracting phase signals from the beat frequency signals to perform adjacent difference processing, the scheme can completely acquire amplitude, frequency and position information related to vibration signals, but due to the accumulation effect of phases and the singular point problem in phase winding, errors are easy to occur in practical application, the three vibration sensing demodulation schemes can all realize the acquisition of vibration signals, but all have the problems of incompleteness, low accuracy and the like in the acquisition of vibration information, the interference of noise in practical application and monitoring systems also easily causes the vibration signals to be submerged in noise signals, thereby causing the phenomenon that the vibration signals cannot be effectively detected, particularly for signals with poor signal-to-noise ratio, the extraction of the vibration signals is more difficult, the method is not suitable for monitoring occasions requiring high sensitivity and high accuracy, such as weak vibration signals, large environmental noise and the like. The distributed vibration sensing demodulation method based on the weak signal-to-noise ratio signal is suitable for effectively detecting the vibration signal under the condition of the weak signal-to-noise ratio.
Disclosure of Invention
In order to overcome the defects of the traditional distributed optical fiber vibration sensing demodulation technology based on phase sensitive optical time domain reflection and better meet the requirement of effectively extracting vibration information under weak signal-to-noise ratio signals and complex conditions on the basis of maintaining the traditional distributed vibration sensing framework, the invention provides a distributed vibration sensing demodulation method based on the weak signal-to-noise ratio signals.
A distributed vibration sensing demodulation method based on weak signal-to-noise ratio signals is characterized by comprising the following steps:
(1) firstly, partitioning a Rayleigh scattering reflected signal for matrix processing, acquiring a series of original data of the reflected signal of a single pulse, and then carrying out low-pass filtering processing on the original data to filter out a high-frequency part of a beat signal;
(2) then, carrying out segmented interpolation processing on the Rayleigh scattering reflected signals, wherein the interpolation function enables data to become integer frequency points;
(3) then, segmenting the reflection data of each pulse according to the distance resolution, wherein the segmentation processing is to effectively extract the vibration position and reduce the calculation amount;
(4) and finally, carrying out Fourier transform on the segmented pulse reflection data, and extracting amplitude and phase information of the intermediate frequency signal according to the intermediate frequency signal of the acousto-optic modulator.
Further, in order to improve the sensitivity of detecting the vibration signal, an effective vibration signal is extracted under the condition of weak signal-to-noise ratio, and autocorrelation processing is respectively carried out on the time direction of the pulse train of the amplitude and the phase of the intermediate frequency signal at a certain position of the optical fiber.
Further, the self-correlation signals of the amplitude and the phase are subjected to cross-correlation treatment, then Fourier change is carried out on the cross-correlation signals, the power spectral density of a cross-correlation function is obtained, the process can effectively inhibit background noise, further extracts vibration signals,
the current A (t) output by the detector and related to the vibration is as follows:
A(t)∝c|r0+Δr(t)|ESELcos(2πΔft+Δφ(t))
where c is the response coefficient of the balanced detector, r0The Rayleigh scattering coefficient of the optical fiber under the condition of no disturbance, Δ r (t) is the change of the Rayleigh scattering coefficient of the optical fiber caused by vibration, Δ phi (t) is the phase change of the optical fiber transmission light caused by vibration,ESfor injecting the amplitude of the pulsed light field, ELΔ f is the heterodyne frequency difference for the amplitude of the local optical field.
Further, the vibration-related alternating current a (t) output by the balance detector is obtained by the following system: a high-coherence narrow-linewidth laser is used as a light source and is divided into two beams of light through a 90:10 coupler, wherein one beam of light is modulated into a light pulse sequence through an acousto-optic modulator, the light pulse sequence is amplified by an optical amplifier and then enters a port 1 of a circulator, the light pulse sequence is input into a vibration sensing optical fiber through a port 2 of the circulator, backward Rayleigh scattering light in the vibration sensing optical fiber passes through the circulator and is reflected out of a port 3 of the circulator and enters a coupler 50:50 together with the other light beam in the first 90:10 coupler, heterodyne beat frequency is carried out in the coupler, a beat frequency optical signal passes through a balance detector to be converted into an electrical signal, and finally the electrical signal is collected by a data acquisition card.
Compared with the prior art, the invention has the characteristics and advantages that: the advantages of an amplitude modulation method and a phase modulation method in a distributed vibration sensing demodulation scheme are comprehensively utilized, block filtering and segmented interpolation processing are carried out, the phase and amplitude information of the obtained intermediate frequency signal are subjected to autocorrelation processing and then cross-correlation operation, frequency information related to the vibration signal can be further extracted, the error of the existing demodulation method is reduced to a certain extent, and the method can also be used for accurately extracting the frequency and phase information related to the vibration signal for the signal with weak signal to noise ratio.
Drawings
FIG. 1 is a flow chart of the algorithm of the present invention.
Fig. 2 is a schematic diagram of a distributed optical fiber vibration sensing structure based on phase sensitive optical time domain reflection.
Detailed Description
The following description of the embodiments of the present invention is provided in connection with the accompanying drawings and examples, but the invention is not limited thereto.
The structure of the distributed optical fiber vibration sensing system based on phase sensitive optical time domain reflection adopted in the embodiment is shown in figure 1, the system adopts a high-coherence narrow linewidth laser as a light source, the high-coherence narrow linewidth laser is divided into two beams of light through a coupler of 90:10, one beam of light is modulated into a light pulse sequence through an acousto-optic modulator, the light pulse sequence is amplified by an optical amplifier and then enters a port 1 of a circulator, the amplified light pulse sequence is input into a vibration sensing optical fiber through a port 2 of the circulator, the backward Rayleigh scattered light in the vibration sensing optical fiber passes through the circulator and is reflected out of the 3 ports of the circulator, enters a 50:50 coupler with the other beam in the first 90:10 coupler, heterodyne beat frequency is carried out in the coupler, a beat frequency optical signal passes through a balance detector, the optical signal is converted into an electric signal, and finally the electric signal is collected by a data acquisition card.
The current A (t) output by the detector and related to the vibration is as follows:
A(t)∝c|r0+Δr(t)|ESELcos(2πΔft+Δφ(t))
where c is the response coefficient of the balanced detector, r0The Rayleigh scattering coefficient of the optical fiber under the condition of no disturbance, delta r (t) is the change of the Rayleigh scattering coefficient of the optical fiber caused by vibration, delta phi (t) is the phase change of the optical fiber transmission light caused by vibration, ESFor injecting the amplitude of the pulsed light field, ELΔ f is the heterodyne frequency difference for the amplitude of the local optical field.
As shown in fig. 2, the method includes the steps of performing starting point positioning on an alternating current signal a (t) output by a balance detector and related to vibration, then performing blocking and low-pass filtering, then performing segmented interpolation, performing fourier transform on a reflection signal after the segmented interpolation, and then extracting amplitude and phase information of an intermediate frequency signal according to the intermediate frequency signal of an acousto-optic modulator.
When extracting the amplitude and phase information of the intermediate frequency signal, the real part of the signal is i (t) and the imaginary part of the signal is s (t), and the corresponding amplitude and phase signals are:
Δφ(t)∝arctan(S(t)/I(t))+kπ
where k is a natural number, Δ r (t) is amplitude information related to the vibration signal, and Δ Φ (t) is phase information related to the vibration signal, it can be seen from the phase equation that when i (t) approaches 0, a singular point exists in the phase, and an error is easily generated in the actual signal processing. The actual amplitude and phase signals are therefore:
in the above formula, nr(t) is the amplitude modulated signal noise,
is phase modulated signal noise.
In order to suppress noise generated by signal modulation and singular point defects brought by phase demodulation as much as possible, after extracting the phase and amplitude of a vibration signal by using segmented interpolation and Fourier transform, performing autocorrelation algorithm processing on the phase and amplitude, and after respective autocorrelation, performing cross-correlation processing on autocorrelation signals of the amplitude and the phase to obtain a cross-correlation function:
wherein R isS(τ) is the cross-correlation function of the signal correlations, Rn(τ) is the noise-related cross-correlation function, from which the noise component with a large influence on the phase unwrapping is seen
The frequency information of the vibration signal can be obtained by carrying out frequency spectrum analysis on the cross-correlation signal.
In a specific embodiment of the invention, the laser line width of a narrow line width laser is 2kHz, the laser emergent power is 10dBm, the pulse width output by an acousto-optic modulator is 300ns, the peak power is 8dBm, the coupling ratio of two couplers is 90:10 and 50:50 respectively, the length of a vibration sensing optical fiber is 20km, a 100Hz-500Hz sine wave vibration signal is applied to the tail end of the vibration sensing optical fiber 20km, and the method can effectively detect and extract the amplitude, phase and frequency information of the vibration signal.
Claims (1)
1. A distributed vibration sensing demodulation method based on weak signal-to-noise ratio signals is characterized by comprising the following steps:
(1) firstly, partitioning a Rayleigh scattering reflected signal for matrix processing, acquiring a series of original data of the reflected signal of a single pulse, and then carrying out low-pass filtering processing on the original data to filter out a high-frequency part of a beat signal;
(2) then, carrying out segmented interpolation processing on the Rayleigh scattering reflected signals, wherein the interpolation function enables data to become integer frequency points;
(3) then, segmenting the reflection data of each pulse according to the distance resolution, wherein the segmentation processing is to effectively extract the vibration position and reduce the calculation amount;
(4) finally, Fourier transform is carried out on the segmented pulse reflection data, and amplitude and phase information of the intermediate frequency signal are extracted according to the intermediate frequency signal of the acousto-optic modulator;
the current A (t) output by the detector and related to the vibration is as follows:
A(t)∝c|r0+Δr(t)|ESELcos(2πΔft+Δφ(t))
where c is the response coefficient of the balanced detector, r0The Rayleigh scattering coefficient of the optical fiber under the condition of no disturbance, delta r (t) is the change of the Rayleigh scattering coefficient of the optical fiber caused by vibration, delta phi (t) is the phase change of the optical fiber transmission light caused by vibration, ESFor injecting the amplitude of the pulsed light field, ELThe amplitude of the local light field is shown, and delta f is the heterodyne frequency difference; the vibration-related alternating current A (t) output by the balance detector is obtained by the following system: a high-coherence narrow-linewidth laser is used as a light source and is divided into two beams of light through a 90:10 coupler, wherein one beam of light is modulated into a light pulse sequence through an acousto-optic modulator, the light pulse sequence is amplified by an optical amplifier and then enters a port 1 of a circulator, the light pulse sequence is input into a vibration sensing optical fiber through a port 2 of the circulator, backward Rayleigh scattering light in the vibration sensing optical fiber passes through the circulator and is reflected out of a port 3 of the circulator and enters a coupler 50:50 together with the other light beam in the first 90:10 coupler, heterodyne beat frequency is carried out in the coupler, a beat frequency optical signal passes through a balance detector to be converted into an electrical signal, and finally the electrical signal is collected by a data acquisition card.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110563666.8A CN113124994B (en) | 2021-05-24 | 2021-05-24 | Distributed vibration sensing demodulation method based on weak signal-to-noise ratio signal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110563666.8A CN113124994B (en) | 2021-05-24 | 2021-05-24 | Distributed vibration sensing demodulation method based on weak signal-to-noise ratio signal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113124994A true CN113124994A (en) | 2021-07-16 |
| CN113124994B CN113124994B (en) | 2022-09-23 |
Family
ID=76783219
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110563666.8A Active CN113124994B (en) | 2021-05-24 | 2021-05-24 | Distributed vibration sensing demodulation method based on weak signal-to-noise ratio signal |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113124994B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113824661A (en) * | 2021-11-22 | 2021-12-21 | 高勘(广州)技术有限公司 | Modulation and demodulation method for communication system |
| CN115014497A (en) * | 2022-05-18 | 2022-09-06 | 暨南大学 | DAS signal processing method based on improved Hilbert-Huang transform |
| CN115389007A (en) * | 2022-10-26 | 2022-11-25 | 之江实验室 | Demodulation method of distributed acoustic wave sensing system adopting scattering enhanced optical fiber |
| CN117073990A (en) * | 2023-10-16 | 2023-11-17 | 常州灵动芯光科技有限公司 | Linewidth testing system and method for narrow linewidth laser |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110150477A1 (en) * | 2009-12-18 | 2011-06-23 | Winzer Peter J | Receiver Algorithms for Coherent Detection of Polarization-Multiplexed Optical Signals |
| CN102128639A (en) * | 2010-12-24 | 2011-07-20 | 中国计量学院 | Spontaneous Brillouin scattered light time-domain reflectometer on basis of double laser frequency locking |
| CN106679790A (en) * | 2016-12-05 | 2017-05-17 | 华南理工大学 | Cross-correlation demodulation method for improving sensitivity of distributed optical fiber vibration sensing |
| CN111157102A (en) * | 2020-01-02 | 2020-05-15 | 河海大学常州校区 | Positioning method for eliminating frequency interference in distributed optical fiber sensing system |
-
2021
- 2021-05-24 CN CN202110563666.8A patent/CN113124994B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110150477A1 (en) * | 2009-12-18 | 2011-06-23 | Winzer Peter J | Receiver Algorithms for Coherent Detection of Polarization-Multiplexed Optical Signals |
| CN102128639A (en) * | 2010-12-24 | 2011-07-20 | 中国计量学院 | Spontaneous Brillouin scattered light time-domain reflectometer on basis of double laser frequency locking |
| CN106679790A (en) * | 2016-12-05 | 2017-05-17 | 华南理工大学 | Cross-correlation demodulation method for improving sensitivity of distributed optical fiber vibration sensing |
| CN111157102A (en) * | 2020-01-02 | 2020-05-15 | 河海大学常州校区 | Positioning method for eliminating frequency interference in distributed optical fiber sensing system |
Non-Patent Citations (3)
| Title |
|---|
| YING SHANG ET AL.: "Optical fiber distributed acoustic sensing based on the self-interference of Rayleigh backscattering", 《MEASUREMENT》 * |
| 司召鹏等: "基于FFT 的分布式振动传感信号解调分析", 《中国激光》 * |
| 贾青等: "基于DFB光纤激光拍频解调的高分辨率声发射检测技术", 《石家庄铁道大学学报(自然科学版)》 * |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113824661A (en) * | 2021-11-22 | 2021-12-21 | 高勘(广州)技术有限公司 | Modulation and demodulation method for communication system |
| CN113824661B (en) * | 2021-11-22 | 2022-03-15 | 高勘(广州)技术有限公司 | Modulation and demodulation method for communication system |
| CN115014497A (en) * | 2022-05-18 | 2022-09-06 | 暨南大学 | DAS signal processing method based on improved Hilbert-Huang transform |
| CN115389007A (en) * | 2022-10-26 | 2022-11-25 | 之江实验室 | Demodulation method of distributed acoustic wave sensing system adopting scattering enhanced optical fiber |
| CN115389007B (en) * | 2022-10-26 | 2023-03-10 | 之江实验室 | Demodulation method of distributed acoustic wave sensing system adopting scattering enhanced optical fiber |
| CN117073990A (en) * | 2023-10-16 | 2023-11-17 | 常州灵动芯光科技有限公司 | Linewidth testing system and method for narrow linewidth laser |
| CN117073990B (en) * | 2023-10-16 | 2024-01-26 | 常州灵动芯光科技有限公司 | Linewidth testing system and method for narrow linewidth laser |
Also Published As
| Publication number | Publication date |
|---|---|
| CN113124994B (en) | 2022-09-23 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN113124994B (en) | Distributed vibration sensing demodulation method based on weak signal-to-noise ratio signal | |
| CN106679790B (en) | Cross-correlation demodulation method for improving sensitivity of distributed optical fiber vibration sensing | |
| CN107101658B (en) | Phase sensitive optical time domain reflection distributed optical fiber sensing system method for rapidly positioning | |
| CN112097813B (en) | 3X 3 coupler photoelectric detection method and device based on optical frequency modulation | |
| CN106052842B (en) | Distributed optical fiber vibration sensing system capable of eliminating fading noise and demodulation method thereof | |
| CN107179097B (en) | Optical fiber interference type sensing modulation-demo-demodulation method and device based on phase shift signal modulation | |
| CN110132329B (en) | Stress, temperature and vibration composite detection optical fiber sensor and signal processing method | |
| CN110864714B (en) | Distributed sensing system based on Michelson-Sagnac fiber optic interferometer | |
| CN107990970B (en) | The method for eliminating the noise that declines in distribution type fiber-optic acoustic systems | |
| CN207036249U (en) | A kind of highly sensitive distributed optical fiber vibration sensing system | |
| CA2841403A1 (en) | Method of acoustic surveying | |
| CN103900623A (en) | Optical time domain reflectometer based on double acoustic-optical modulators and common-mode rejection method of optical time domain reflectometer | |
| CN114543973B (en) | Distributed ultrahigh frequency vibration signal measurement method and optical fiber sensor | |
| CN113852416A (en) | Phase demodulation method and device with fading noise identification and elimination function | |
| CN102564476B (en) | Multipoint disturbance positioning method | |
| Bai et al. | Noise reduction method of Φ-OTDR system based on EMD-TFPF algorithm | |
| CN210567574U (en) | Oil and gas pipeline leakage monitoring system based on optical fiber | |
| CN115824378A (en) | Vibration detection method of high-frequency-response distributed optical fiber acoustic wave sensor | |
| CN111579048A (en) | OFDR system vibration detection method based on sliding time gating | |
| CN113639847B (en) | Pulse modulation and demodulation module and distributed optical fiber vibration sensing positioning method | |
| CN112179475B (en) | Separation method of multi-source aliasing distributed optical fiber vibration sensing signals | |
| CN112880711B (en) | Distributed optical fiber sensing method and system based on double pulse modulation | |
| CN108317402B (en) | Distributed optical fiber sensing positioning early warning analysis method | |
| CN108344432A (en) | The method for obtaining the heat transfer agent of Brillouin fiber optic distributed sensing system | |
| CN116907627A (en) | Optical path difference auxiliary-based large dynamic range distributed phase sensing method and device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |