WO2020181920A1 - Procédé de traitement de signaux basé sur un capteur acoustique distribué à fibre optique - Google Patents

Procédé de traitement de signaux basé sur un capteur acoustique distribué à fibre optique Download PDF

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WO2020181920A1
WO2020181920A1 PCT/CN2020/072557 CN2020072557W WO2020181920A1 WO 2020181920 A1 WO2020181920 A1 WO 2020181920A1 CN 2020072557 W CN2020072557 W CN 2020072557W WO 2020181920 A1 WO2020181920 A1 WO 2020181920A1
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signal
optical fiber
acoustic sensor
sensing
signal source
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PCT/CN2020/072557
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English (en)
Chinese (zh)
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蔡海文
梁嘉靖
郑汉荣
王照勇
卢斌
叶青
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中国科学院上海光学精密机械研究所
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Publication of WO2020181920A1 publication Critical patent/WO2020181920A1/fr

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    • 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
    • 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

Definitions

  • the invention relates to the field of signal source monitoring, in particular to a signal processing method based on a distributed optical fiber acoustic sensor.
  • Distributed optical fiber acoustic sensors are widely used in railway safety, oil and gas pipeline monitoring, perimeter security and other fields.
  • Most of the existing distributed optical fiber acoustic sensors use ordinary communication optical fibers as the sensing fibers.
  • They have low transduction coefficients for disturbance signals in the application scenarios of distributed optical fiber acoustic sensors, and their ability to detect weak signals is limited by the sensor.
  • the base noise of the system on the other hand, the application scenarios of distributed optical fiber acoustic sensors often have environmental noise and interference signals other than the target signal, making it difficult for the sensing system to effectively identify the target signal in a complex working environment.
  • Phase-sensitive OTDR system based on digital coherent detection is proposed.
  • the sensitive optical time domain reflectometer quantifies the measurement system and the demodulation formula of amplitude and phase information, but it does not further use the spatial correlation between the quantified sound field signals to enhance the sound field signals.
  • the present invention proposes a signal processing method based on distributed optical fiber acoustic sensors, which enables the distributed sensing system to detect disturbance signals in a directional and fixed-point manner, and at the same time has the ability to enhance and suppress specific directions or specific spaces.
  • the ability of location signals is suitable for existing sensing systems and has the advantages of simple implementation, fast processing speed, strong anti-interference ability, and obvious improvement in signal-to-noise ratio. It can greatly improve the use of distributed optical fiber acoustic sensors in railway safety, oil and gas pipeline monitoring, and perimeter The ability to monitor target signals in complex working environments such as security.
  • the present invention proposes a signal processing method based on a distributed optical fiber acoustic sensor, which includes a signal source, a distributed optical fiber acoustic sensor, and a sensing optical fiber.
  • the method is characterized in that the method is as shown in Figure 1 and includes the following steps:
  • the distributed optical fiber acoustic sensor transmits detection light pulses to the sensing fiber, quantitatively monitors the sound field sensed along the sensing fiber, and obtains the sound field distribution signal S(l, t), where l Represents the one-dimensional axial space of the sensing fiber, and t is time;
  • the number of sensing units included in the enhanced aperture is N, which is determined by the spatial sampling frequency f s of the distributed optical fiber acoustic sensor, which is taken at intervals of ⁇ n,
  • the sound field signals collected by two sensing units are used as the sampling signal group,
  • l 1 represents the starting position of the enhanced aperture on the fiber link
  • M represents the number of signal sources
  • the spatial position information is the azimuth vector of the signal source relative to the enhanced aperture or the three-dimensional position coordinates of the signal source relative to the enhanced aperture.
  • the spatial position information is obtained by using the signal source spatial positioning method or artificially designated according to prior knowledge.
  • the interval of the enhanced aperture is determined according to the requirements of specific application scenarios, and the calculation time and the enhancement effect need to be weighed.
  • the sampling signal group includes the number of sensing units according to the requirements of specific application scenarios, and the calculation time and the enhancement effect need to be weighed.
  • the signal source spatial positioning method based on distributed optical fiber sensing does not belong to the scope of this patent.
  • the spatial information may be only the azimuth vector of the signal source relative to the enhanced aperture, or only the three-dimensional position coordinates of the signal source relative to the enhanced aperture, or both may be included, depending on actual application scenarios and application requirements.
  • the array signal processing method in the step 3) is an adaptive spatial filtering method or a delay sum method.
  • the adaptive spatial filtering method is one of a minimum variance distortionless response beamformer (MVDR), a linearly constrained minimum variance beamformer (LCMV), and a generalized sidelobe canceling beamformer (GSC).
  • MVDR minimum variance distortionless response beamformer
  • LCMV linearly constrained minimum variance beamformer
  • GSC generalized sidelobe canceling beamformer
  • the delay summation method is as follows:
  • the signal suppression effect is limited by the size of the enhanced aperture. If the m'th signal source needs to be enhanced, recalculate its delay compensation weight w m' ( ⁇ ), and calculate the enhanced signal according to the above equation Just output Y m' (t).
  • LCMV linear constrained minimum variance beamformer
  • K represents the number of repetitions of the distributed optical fiber acoustic sensor emitting detection light pulses to the sensing optical fiber
  • the restriction vector determines that only The m-th signal source performs directional enhancement, while the other signal sources perform directional suppression.
  • the phase compensation weight is calculated according to the following equation,
  • H represents conjugate transpose
  • the enhanced signal is calculated according to the following equations,
  • the step 2) further includes:
  • the step 3) is to use a linearly constrained minimum variance beamformer to process the frequency domain sampled signal group, specifically:
  • J represents the frequency accuracy of the fast Fourier transform of the distributed optical fiber acoustic sensor on the time-domain sampling signal group
  • the restriction vector F 1 ⁇ M [0 0 ... 1 ... 0], where the m-th element of the restriction vector is 1, and the rest are 0.
  • the restriction vector is determined to be only
  • the m-th signal source is directional enhancement, and the other signal sources are directional suppression.
  • the phase compensation weight corresponding to each sub-band is calculated according to the following equation,
  • H represents conjugate transpose
  • the frequency-domain enhanced signal is calculated according to the following equation,
  • the present invention is suitable for the existing distributed optical fiber acoustic sensor system, which can be realized only by using the sensing units distributed along the optical fiber and preprocessing the received signal, and is simple to implement and low in cost;
  • the present invention not only effectively suppresses the random noise of the system, improves the sensitivity of the system, but also has the function of enhancing or suppressing specific spatial directions and specific spatial positions, effectively expanding the distributed optical fiber acoustic sensor in sound waves
  • Applications in the fields of communication and detection have further improved the existing sensing system's ability to monitor target signals in complex working environments, which is of great significance.
  • the present invention enables the distributed optical fiber acoustic sensor to realize real-time quantitative sound field measurement in a large range and long distance, with a large sensing aperture, easy to form a beamformer with precise spatial orientation, and can effectively suppress interference signals in the measurement environment, and improve Signal-to-interference ratio:
  • the sensing points are densely arranged on the sensing fiber, providing a large number of redundant sensing signals for signal source enhancement, which can effectively suppress the system noise of the sensing system itself, and greatly improve the sensitivity of the sensing system .
  • Figure 1 is a flow chart of signal processing of the present invention
  • FIG. 2 is a schematic diagram of the signal processing method of the present invention.
  • Figure 3 is a schematic diagram of the signal processing method of the dual-parallel sensing optical fiber laying structure of the present invention
  • the schematic diagram is shown in Figure 2.
  • the distributed optical fiber acoustic sensor 1 including the phase-sensitive optical time domain reflectometer for coherent detection, the sensing fiber 2, the enhanced aperture 2-1, the sensing channel 2-2, and the specific spatial direction
  • the signal source can be a wideband signal or a narrowband signal.
  • the signal processing method mainly includes the following three steps:
  • the distributed optical fiber acoustic sensor 1 of the coherent detection phase-sensitive optical time domain reflectometer emits detection light pulses to the sensing fiber 2 to quantitatively monitor the sound field sensed along the sensing fiber, And obtain the sound field distribution signal S(l,t), where l represents the one-dimensional axial space of the sensing fiber, and t is the time;
  • phase-sensitive optical time domain reflectometer 1 preprocesses the obtained sound field signal:
  • the distributed optical fiber acoustic sensor 1 selects a section of L as the enhanced aperture 2-1 in the sensing optical fiber link, and uses the signal source spatial positioning method based on distributed optical fiber sensing in this section.
  • the spatial position information of the received signal within the enhanced aperture 2-1 is obtained.
  • the number of sensing channels 2-2 included is N, which is specifically determined by the sampling frequency f s of the distributed optical fiber acoustic sensor, taking ⁇ n as the interval.
  • the sound field signals collected by two sensing units are used as the sampling signal group,
  • l 1 represents the starting position of the enhanced aperture 2-1 on the optical fiber link.
  • the enhanced signal is calculated according to the following equations,
  • the suppression effect is limited by the size of the enhanced aperture. If the m'th signal source needs to be enhanced, recalculate its delay compensation weight w m' ( ⁇ ), and calculate the enhanced signal output Y according to the above equation m' (t) is fine.
  • the principle diagram is shown in Figure 3. It includes a distributed optical fiber acoustic sensing system with an optical frequency domain reflectometer structure, a sensing fiber 2, an enhanced aperture 2-1, a sensing channel 2-2, and a signal source in a specific spatial direction. 3-1, signal source 3-2 and 3-3 beamformer 4 at a specific spatial location.
  • the sensing optical fiber 2 is laid in a double parallel structure and is connected to the distributed optical fiber acoustic sensing system 1.
  • the sensing optical fiber laying structure needs to meet the requirements of the signal source spatial positioning method based on distributed optical fiber sensing, which does not belong to the scope of this patent.
  • the signal source can be considered a narrowband signal.
  • the signal processing method mainly includes 3 steps:
  • the optical frequency domain reflectometer 1 emits detection light pulses to the sensing fiber 2, quantitatively detects the sound field sensed along the sensing fiber 2, and obtains the sound field distribution signal S(l, t), where l represents the one-dimensional axial space of the sensing fiber, and t is time;
  • the distributed optical fiber acoustic sensor 1 selects an interval of length L as the enhanced aperture 2-1 in the sensing optical fiber link.
  • the enhanced aperture 2-1 is specified according to the prior knowledge of the application scenario.
  • the number of sensing units included in the enhanced aperture is N, which is specifically determined by the spatial sampling frequency f s of the distributed optical fiber acoustic sensor, taking ⁇ n as the interval
  • the sound field signals collected by two sensing units are used as the sampling signal group,
  • l 1 represents the starting position of the enhanced aperture on the optical fiber link 2_2.
  • the sampled signal group is input to the beamformer 4, and processed by the linearly constrained minimum variance beamformer (LCMV), and the covariance matrix of the sampled signal group is first calculated according to the following equation,
  • K represents the number of repetitions of the optical frequency domain reflectometer transmitting the probe light pulse to the sensing fiber.
  • the restriction vector F 1 ⁇ M [0 0 ... 1 ... 0], where the m-th element of the restriction vector is 1, and the rest are 0.
  • the restriction vector determines that only the m-th signal source is directional enhancement, and the other signal sources are directional suppression.
  • the enhanced signal is calculated according to the following equations,
  • the principle diagram of the distributed optical fiber acoustic sensing system adopting the direct detection phase-sensitive optical time domain reflectometer structure is similar to that shown in Figure 2, and will not be repeated here.
  • the signal source is a broadband signal, and its signal processing method mainly includes the following 3 steps:
  • the phase-sensitive optical time domain reflectometer 1 emits detection light pulses to the sensing fiber 2, quantitatively detects the sound field sensed along the sensing fiber 2, and obtains the sound field distribution signal S(l,t) , Where l represents the one-dimensional axial space of the sensing fiber, and t is time;
  • the distributed optical fiber acoustic sensor 1 selects a section of L as the enhanced aperture 2-1 in the sensing optical fiber link, and uses the signal source spatial positioning method based on distributed optical fiber sensing in this section. Obtain the signal source spatial position information of the received signal within the enhanced aperture.
  • the number of sensing units included in the enhanced aperture is N, which is specifically determined by the spatial sampling frequency f s of the distributed optical fiber acoustic sensor, taking ⁇ n as the interval
  • the sound field signals collected by two sensing units are used as the sampling signal group,
  • l 1 represents the starting position of the enhanced aperture on the optical fiber link 2.
  • the sampled signal group is transformed into the frequency domain X(f), and split into P subband signals X(f p ).
  • J represents the frequency accuracy of the fast Fourier transform performed by the direct detection optical time domain reflectometer on the time domain sampled signal group.
  • F 1 ⁇ M [0 0 ... 1 ... 0] where the m-th element of the restriction vector is 1, and the rest are 0.
  • the restriction vector determines that only the m-th signal source is directional enhancement, and the other signal sources are directional suppression.
  • the frequency-domain enhanced signal is calculated according to the following equation,

Abstract

L'invention concerne un procédé de traitement de signaux basé sur un capteur acoustique distribué à fibre optique ; dans ledit procédé, des informations de position spatiale d'une source de signaux s'obtiennent au moyen d'un prétraitement d'un signal de champ acoustique obtenu par une unité de détection ; puis un traitement de signaux est effectué sur les informations décrites, ce qui supprime efficacement le bruit aléatoire du système introduit par le système de détection acoustique distribué à fibre optique lui-même, augmente la sensibilité de système, tout en donnant également la capacité d'améliorer ou de supprimer des signaux entrants spécifiques et spécifiques de position spatiale, et qui permet une détection directionnelle et ponctuelle de signaux de perturbation. La présente invention présente des avantages tels qu'une simplicité de mise en œuvre, une rapidité de vitesse de traitement, une forte capacité de résistance aux interférences et une amélioration évidente du rapport signal sur bruit ; elle améliore en outre la capacité des systèmes de détection existants à surveiller des signaux cibles d'interférence dans un environnement complexe d'exploitation ; elle convient pour une utilisation dans la sécurité ferroviaire, dans la surveillance de canalisations de pétrole et de gaz, dans la sécurité de périmètres et dans des applications analogues ; et revêt une grande importance.
PCT/CN2020/072557 2019-03-14 2020-01-16 Procédé de traitement de signaux basé sur un capteur acoustique distribué à fibre optique WO2020181920A1 (fr)

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CN114754857B (zh) * 2022-06-14 2022-08-23 之江实验室 一种两段式光纤传感水声信号补偿方法和装置

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