Distributed optical fiber sound sensing system and device and sound detection method

Abstract

The embodiment of the invention discloses a distributed optical fiber sound sensing system and device and a sound detection method, and the system comprises a laser source assembly which is used for generating continuous initial laser; the input end of the coupler is connected with the output end of the laser source assembly, and the coupler is used for dividing the initial laser into a first laser beam and a second laser beam; the input end of the acousto-optic modulator is connected with one output end of the coupler, the output end of the acousto-optic modulator is connected with the first input end of the interferometer or the input end of the erbium-doped amplifier, and the acousto-optic modulator is used for modulating the first laser beam into monopulse laser; and the interferometer is used for modulating the single-pulse laser into double-pulse laser and carrying out sound detection, and is also used for carrying out interference on the second laser beam to generate a reverse laser beam so as to carry out frequency adjustment on the laser source assembly. And the signal-to-noise ratio and the detection precision of the sensing system are improved.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensors, and in particular to a distributed optical fiber sound sensing system, device and sound detection method. Background Art

[0002] The distributed fiber optic sound sensing system senses the environmental vibration of the fiber optic loop through narrow linewidth laser pulses, generates and returns Rayleigh scattered light carrying vibration information, and uses the principle of optical coherence to form interference intensity changes, thereby demodulating the vibration conditions at various locations in the fiber optic loop, with extremely high detection sensitivity. This type of sensor is also called a phase-type optical time domain reflectometer.

[0003] The generation of optical interference signals usually adopts two methods: interference between local light and echo (referred to as local light interferometry) and mutual interference between double pulse echoes (referred to as double pulse interferometry). Among them, the commonly used methods for generating double pulses are electrical modulation method and unbalanced Mach-Zehnder interferometry (UB-MZI). The stability of the double pulses generated by the unbalanced Mach-Zehnder interferometry will affect the final sound detection results. In the prior art, in order to improve stability, the commonly used thermal stabilization and anti-vibration methods can achieve a certain double pulse time domain stabilization effect, but the performance improvement is limited, and such systems are relatively complex and large in size, which is not conducive to productization. In addition, the upper limit of system performance of both the local light interferometry method and the double pulse interferometry method is limited by the linewidth parameters of the narrow linewidth light source, and the influence of the linewidth cannot be alleviated.

[0004] There is currently no effective solution to the above problems in the prior art. Summary of the invention

[0005] To solve the above problems, the present invention provides a distributed fiber optic sound sensing system, device and sound detection method, in which the fiber optic ring used to generate dual pulses is also used as a laser interferometer to generate a feedback control signal of the laser source frequency, thereby solving the problem in the prior art that interference such as environmental vibration and thermal fluctuation cannot be effectively alleviated, and the problem of how to effectively eliminate the influence of light source noise.

[0006] To achieve the above-mentioned object, the present invention provides a distributed optical fiber sound sensing system, comprising: a laser source component, the laser source component is used to generate a continuous initial laser; a coupler, the input end of the coupler is connected to the output end of the laser source component, and is used to divide the initial laser into a first laser beam and a second laser beam; an acousto-optic modulator, the input end of the acousto-optic modulator is connected to an output end of the coupler, and the output end is connected to the first input end of an interferometer or the input end of an erbium-doped fiber amplifier, and is used to modulate the first laser beam into a single-pulse laser; when the output end of the acousto-optic modulator is connected to the first input end of the interferometer, the first output end of the interferometer is connected to the input end of the erbium-doped fiber amplifier; the second input end of the interferometer is connected to the other output end of the coupler through an isolator, and the second output end is connected to the laser source component through a feedback component. The invention relates to a method for transmitting the second laser beam to a receiving component and a coupler for transmitting the second laser beam to a receiving component. The method comprises the following steps: a first port of the circulator is connected to the output end of the erbium-doped fiber amplifier and a second port of the circulator is connected to the sensing fiber, and a third port of the circulator is connected to the receiving component. The output end of the erbium-doped fiber amplifier is connected to the first port of the circulator. The second port of the circulator is connected to the sensing fiber, and the third port of the circulator is connected to the second input end of the interferometer. The second output end of the interferometer is connected to the receiving component. The first input end of the interferometer is connected to the other output end of the coupler through an isolator, and the first output end is connected to the laser source component through a feedback component, so as to receive the second laser beam and transform it into interference light, and adjust the frequency of the laser source component according to the reference value and the intensity value of the interference light.

[0007] Further optionally, the laser source assembly includes: a laser source; the output end of the laser source is connected to the input end of the coupler, and the input end is connected to the output end of the feedback assembly, for generating the initial laser; or, the laser source assembly includes: a laser source and an acousto-optic frequency shifter; the output end of the laser source is connected to the input end of the coupler, and the input end is connected to the output end of the acousto-optic frequency shifter, for generating the initial laser; an acousto-optic frequency shifter, the input end of the acousto-optic frequency shifter is connected to the output end of the feedback assembly, and the output end is connected to the laser source, for shifting the frequency of the laser source.

[0008] Further optionally, the feedback component includes: a photodetector, an input end of the photodetector is connected to the output end of the interferometer, and is used to detect the intensity value of the interference light; a feedback controller, an input end of the feedback controller is connected to the output end of the photodetector, and an output end is connected to a laser source or an acousto-optic modulator, and is used to calculate a frequency correction signal according to the intensity value and a reference value, and control and adjust the frequency of the laser source or the acousto-optic frequency shifter according to the correction signal.

[0009] Further optionally, the laser source is a narrow linewidth laser seed source; and the interferometer is an unbalanced Mach-Zehnder interferometer.

[0010] Further optionally, the receiving component includes: an avalanche photodetector, an AD collector and a data analyzer connected in sequence.

[0011] On the other hand, the present invention provides a sound detection method, which uses the above-mentioned distributed optical fiber sound sensing system to perform sound detection, including: dividing the initial laser into a first laser beam and a second laser beam; pulse-modulating the first laser beam to obtain a single-pulse laser; interfering and amplifying the single-pulse laser and transmitting it to the sensing optical fiber, receiving the echo signal of the sensing optical fiber, and analyzing the echo signal to obtain pending sound information; or amplifying the single-pulse laser and transmitting it to the sensing optical fiber, receiving the echo signal of the sensing optical fiber, and interfering and analyzing the echo signal to obtain pending sound information; interfering with the second laser beam to obtain interference light; adjusting the frequency of the laser source component according to the intensity value of the interference light and a reference value; repeating this step until the difference between the intensity value and the reference value is within a preset difference range, and taking the pending sound information in the corresponding time period at the current moment as reliable sound information; wherein the reference value is pre-set according to the laser source component.

[0012] Further optionally, adjusting the frequency of the laser source assembly according to the intensity value of the interference light and a reference value includes: calculating a frequency correction signal according to the intensity value of the interference light and the reference value; and adjusting the corresponding frequency of the laser source assembly according to the frequency correction signal.

[0013] Further optionally, the parsing of the echo signal includes: performing photoelectric conversion on the echo signal to obtain an electrical signal; and performing signal analysis after AD acquisition on the electrical signal to obtain the pending sound information.

[0014] On the other hand, the present invention further provides a distributed optical fiber sound sensing device, comprising the above-mentioned distributed optical fiber sound sensing system.

[0015] On the other hand, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein the program implements the above-mentioned sound detection method when executed by a processor.

[0016] The above technical solution has the following beneficial effects: by utilizing part of the laser output from the laser source to inject into the optical fiber ring that generates the dual-pulse laser, reverse optical interference is formed. The laser frequency in the reverse interference process and the interference process between the interference arm and the dual-pulse echo of the main laser are completely equivalent. Therefore, by detecting the intensity of the reverse interference light and then controlling the feedback signal of the laser frequency or the laser modulation frequency, the intensity of the reverse interference light can be stabilized, and the system noise caused by various jitters in the conventional dual-pulse distributed optical fiber sensor can be eliminated. The influence of the light source phase noise on the system noise can also be eliminated to a certain extent (equivalently compressing the laser line width of the light source), which improves the signal-to-noise ratio of the sensor as a whole, is conducive to detecting weaker vibration signals, and improves detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 is a schematic structural diagram of a distributed optical fiber sound sensing system provided by an embodiment of the present invention; Figure 2 is a schematic structural diagram of a distributed optical fiber sound sensing system provided by another embodiment of the present invention; Figure 3 is a schematic structural diagram of a distributed optical fiber sound sensing system provided by another embodiment of the present invention; Figure 4 is a schematic structural diagram of a distributed optical fiber sound sensing system provided by another embodiment of the present invention; Figure 5 is a flow chart of a sound detection method provided by an embodiment of the present invention; Figure 6 is a flow chart of a frequency adjustment method provided by an embodiment of the present invention; Figure 7 It is a flow chart of a sound echo signal processing method provided by an embodiment of the present invention.

[0019] Figure numerals: 1-laser source assembly; 101-laser source; 102-acoustic-optic frequency shifter; 2-coupler; 3-acoustic-optic modulator; 4-interferometer; 5-feedback assembly; 501-photodetector; 502-feedback controller; 6-erbium-doped fiber amplifier; 7-circulator; 8-sensing fiber; 9-receiving assembly; 901-avalanche photodetector; 902-AD collector; 903-data analyzer; 10-isolator. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The principle of the local light interference method in the prior art is: a small part of the continuous light output by the narrow linewidth laser seed source is first separated by the first coupler as the local light, and the other part of the light is pulse modulated by the acousto-optic modulator, amplified by the erbium-doped fiber amplifier (EDFA), and then injected into the sensing fiber through the circulator; the echo signal scattered by the sensing fiber is output to the second coupler through the circulator, and the echo signal is coherent with the local light through the second coupler and received by the balanced detector; the output electrical signal of the balanced detector is collected by AD for vibration signal analysis. This method is affected by the optical depolarization effect and the overall optical path disturbance, so the effect is unstable, and the double pulse interference method can effectively eliminate these two effects.

[0022] A commonly used double-pulse interference method is the electrical modulation method, and its principle is: using a double electrical pulse sequence to input an acousto-optic modulator to modulate a narrow linewidth laser seed source to obtain a double-pulse laser. The double-pulse laser is amplified by EDFA and then injected into the sensing fiber. The double-pulse laser interferes with the scattered echo in the sensing fiber and can be used for environmental vibration signal analysis. The double-pulse laser in the double-pulse interference method, as the benchmark for the interference of scattered echo light in the sensing fiber, has a great impact on the system performance, that is, the more stable the double pulses generated by the system, the higher the vibration perception sensitivity. Since the modulation signal of the electrical modulation is an electrical pulse signal, it is limited by the circuit time jitter. It is almost impossible to increase it to the order of magnitude equivalent to the light wave period at this stage. Therefore, the signal-to-noise ratio of the distributed optical fiber sound sensing system based on this type of double-pulse interference is relatively low.

[0023] The principle of the unbalanced Mach-Zehnder interferometer (UB-MZI) dual-pulse phase-type distributed optical fiber sound sensing system is as follows: the laser output by the narrow-linewidth laser seed source is electrically modulated by a single pulse input by the acousto-optic modulator to produce a single laser pulse, and then a dual-pulse laser is obtained through the UB-MZI. The subsequent working principle is the same as the electrical modulation method. In order to stabilize the dual-pulse laser, a common method is to use a thermally stable and anti-vibration system to protect the UB-MZI, which can protect the dual pulses from environmental interference to a certain extent, maintain stability, and improve the signal-to-noise ratio of the sensing fiber echo interference signal. However, this method has limited performance improvement, and such systems are relatively complex and large in size, which is not conducive to productization. In addition, the system performance upper limit of the above three sound sensing systems is limited by the linewidth parameters of the narrow-linewidth laser source, and cannot alleviate the impact of the linewidth.

[0024] To solve the above problems, the present invention provides a distributed optical fiber sound sensing system. Figure 1 , Figure 2 As shown, the distributed optical fiber sound sensing system includes: a laser source component 1, the laser source component 1 is used to generate a continuous initial laser; a coupler 2, the input end of the coupler 2 is connected to the output end of the laser source component 1, and is used to divide the initial laser into a first laser beam and a second laser beam; an acousto-optic modulator 3, the input end of the acousto-optic modulator 3 is connected to an output end of the coupler 2, and the output end is connected to the first input end of the interferometer 4 or the input end of the erbium-doped amplifier, and is used to modulate the first laser beam into a single-pulse laser; when the output end of the acousto-optic modulator 3 is connected to the first input end of the interferometer 4, the first output end of the interferometer 4 is connected to the input end of the erbium-doped fiber amplifier 6; the second input end of the interferometer 4 is connected to the other output end of the coupler 2 through the isolator 10, and the second output end is connected to the laser source component 1 through the feedback component 5, and is used to convert the second laser beam into a single-pulse laser. The output end of the erbium-doped fiber amplifier 6 is connected to the first port of the circulator 7; the second port of the circulator 7 is connected to the sensing fiber 8, and the third port is connected to the receiving component 9; when the output end of the acousto-optic modulator 3 is connected to the input end of the erbium-doped amplifier, the output end of the erbium-doped fiber amplifier 6 is connected to the first port of the circulator 7; the second port of the circulator 7 is connected to the sensing fiber 8, and the third port is connected to the second input end of the interferometer 4; the second output end of the interferometer 4 is connected to the receiving component 9; the first input end of the interferometer 4 is connected to the other output end of the coupler 2 through the isolator 10, and the first output end is connected to the laser source component 1 through the feedback component 5, which is used to receive the second laser beam and convert it into interference light, and adjust the frequency of the laser source component 1 according to the reference value and the intensity value of the interference light.

[0025] like Figure 1 As shown, the laser source assembly 1 is connected to a coupler 2, and the coupler 2 divides the initial laser generated by the laser source assembly 1 into two parts, namely, a first laser beam and a second laser beam, wherein the first laser beam enters the acousto-optic modulator 3, and is electrically modulated by the input single pulse to obtain a single-pulse laser, and the single-pulse laser is input into the first input end (port A shown in the figure) of the interferometer 4 to obtain a double-pulse laser, and the double-pulse laser is output from the first output end (port C shown in the figure) of the interferometer 4, and then amplified by the erbium-doped fiber amplifier 6 and injected into the sensing fiber 8 through the circulator 7, and the echo signal returned by the sensing fiber 8 is input into the receiving assembly 9 through the circulator 7, and the receiving assembly 9 obtains the sound detection result after a series of processing.

[0026] The second laser beam is injected into the second input end (port D in the figure) of the interferometer 4 through the isolator 10. The second laser beam is processed by the interferometer 4 to obtain interference light, which is output from the second output end (port B in the figure). The feedback component 5 receives the interference light and detects its intensity value I, combined with the preset reference value I 0 , calculate the frequency correction signal U (I, I 0 ), adjust the frequency of the laser source component 1 according to the frequency correction signal. Then enter the next round of light intensity detection and frequency correction until the output intensity value I approaches the reference value I 0 .

[0027] Figure 2 For Figure 1 The structure of a distributed fiber optic acoustic sensing system with equivalent structure, such as Figure 2 As shown, it is Figure 1 The difference in structure is that the interferometer 4 is arranged between the circulator 7 and the receiving component 9. Specifically, the laser source component 1 is connected to the coupler 2, and the coupler 2 divides the initial laser generated by the laser source component 1 into two parts, namely the first laser beam and the second laser beam, wherein the first laser beam enters the acousto-optic modulator 3, and a single-pulse laser is obtained after electrical modulation by the input single pulse, and the single-pulse laser is input into the erbium-doped fiber amplifier 6, and after amplification, it is input into the sensing fiber 8 through the circulator 7, and the echo signal returned by the sensing fiber 8 enters the second input end (D port in the figure) of the interferometer 4 for interference and then outputs from the second output end (B port in the figure), and the receiving component 9 performs a series of processing on it to obtain the sound detection result.

[0028] The second laser beam is injected into the first input end (port A in the figure) of the interferometer 4 through the isolator 10. The second laser beam is processed by the interferometer 4 to obtain interference light, which is output from the first output end (port C in the figure). The feedback component 5 receives the interference light and detects its intensity value I, combined with the preset reference value I 0 , calculate the frequency correction signal U (I, I 0 ), adjust the frequency of the laser source component 1 according to the frequency correction signal. Then enter the next round of light intensity detection and frequency correction until the output intensity value I approaches the reference value I 0 .

[0029] It should be noted that the first input terminal corresponds to the first output terminal, the second input terminal corresponds to the second output terminal, and the laser transmission directions in the two paths (D→B and A→C) are opposite. The amount of the first laser beam and the second laser beam can be the same or different. Preferably, a small part of the initial laser can be separated to generate interference light. Ports A, B, C, and D are only marked for convenience of explanation and do not represent the port definition in actual application.

[0030] As an optional implementation, the reference value I 0The combined state of the fiber ring and the laser frequency, i.e. the reference state of the stable interference of the laser double pulses, is in principle 0 The selection of can be any value of the measured interference value, but considering the control efficiency and effect, I 0 The value of should be chosen so that |dI / df| is maximized (f is the frequency of the light source).

[0031] Calculate the frequency correction signal U(I, I 0 ), by comparing the reference value of the interference intensity and the real-time intensity value, an error signal is generated. This error signal can be used to set the light source frequency and play a negative feedback role, that is, the measured interference intensity value can gradually approach the reference value. In addition, since the setting of the light source frequency needs to be based on the frequency correction signal U (I, I 0 ), this function requires the laser source assembly 1 to have a fast frequency adjustment function.

[0032] Because the interferometer 4 is always affected by environmental interference, and the frequency of the laser source component 1 is always in a jitter state (phase noise), the intensity value I of the interference light is also fluctuating. The above stabilization process can greatly reduce the change of interference intensity caused by environmental interference and light source frequency jitter, and stabilize it at I 0 The intensity of the output interference light reflects the combined effect of the interferometer and the light source frequency. Therefore, by detecting the intensity value of the interference light to generate a light source frequency adjustment signal and control the light source frequency, the stability of the double-pulse laser interference can be maintained, thereby ensuring the signal-to-noise ratio of the sensor.

[0033] As an optional implementation, Figure 1 , Figure 2 As shown, the laser source assembly 1 includes: a laser source 101; the output end of the laser source 101 is connected to the input end of the coupler 2, and the input end is connected to the output end of the feedback assembly 5, for generating an initial laser; or Figure 3 , Figure 4 As shown, the laser source assembly 1 includes: a laser source 101 and an acousto-optic frequency shifter 102; the output end of the laser source 101 is connected to the input end of the coupler 2, and the input end is connected to the output end of the acousto-optic frequency shifter 102, for generating an initial laser; the acousto-optic frequency shifter 102, the input end of the acousto-optic frequency shifter 102 is connected to the output end of the feedback assembly 5, and the output end is connected to the laser source 101, for shifting the frequency of the laser source 101.

[0034] There are two ways to set the laser source assembly 1. One is that the laser source assembly 1 only includes the laser source 101. In this case, Figure 1 , Figure 2 As shown, the feedback component 5 directly controls the laser source 101, that is, through the frequency correction signal U (I, I 0 ) directly adjusts the frequency of the laser source 101.

[0035] Another way is that the laser source assembly 1 includes a laser source 101 and an acousto-optic frequency shifter 102. In this case, Figure 3 , Figure 4 As shown, the feedback component 5 controls the acousto-optic frequency shifter 102, that is, through the frequency correction signal U (I, I 0 ) The modulation frequency of the acousto-optic frequency shifter 102 is adjusted, and the adjusted acousto-optic frequency shifter 102 then shifts the frequency of the laser source 101, which can improve the fineness of the adjustment.

[0036] As an optional implementation, Figure 1-4 As shown, the feedback component 5 includes: a photodetector 501, the input end of the photodetector 501 is connected to the output end of the interferometer 4, and is used to detect the intensity value of the interference light; a feedback controller 502, the input end of the feedback controller 502 is connected to the output end of the photodetector 501, and the output end is connected to the laser source 101 or the acousto-optic modulator 3, and is used to calculate a frequency correction signal according to the intensity value and the reference value, and control and adjust the frequency of the laser source 101 or the acousto-optic frequency shifter 102 according to the correction signal.

[0037] like Figure 1-4 As shown, the feedback component 5 includes a photodetector 501 and a feedback controller 502. The photodetector 501 performs photoelectric conversion on the interference light to obtain an electrical signal. The feedback component 5 receives the electrical signal and compares it with a reference value to obtain an error signal. The frequency correction signal U (I, I 0 ), and then through the frequency correction signal U (I, I 0 ) adjusts the frequency of the corresponding device (the modulation frequency of the acousto-optic frequency shifter 102 or the frequency of the laser source 101).

[0038] As an optional embodiment, the feedback component 5 can be implemented by a combination of software and hardware. For example, a predetermined program is set on a single-chip microcomputer to extract the intensity of the electrical signal, calculate the difference between the intensity value and the reference value, determine the frequency correction signal based on the difference, and adjust the frequency of the acousto-optic frequency shifter 102 or the laser source 101.

[0039] As an optional implementation, regarding the relationship between the frequency correction signal and the error signal U(I, I 0 ), the relationship between the two can be obtained in advance through simulation experiments, for example, a relationship curve or a relationship function can be obtained.

[0040] As an optional implementation, the laser source 101 is a narrow linewidth laser seed source; and the interferometer 4 is an unbalanced Mach-Zehnder interferometer 4 .

[0041] A narrow linewidth laser seed source is a laser whose output laser has an extremely narrow spectral linewidth. Its main characteristics are extremely high coherence and stability.

[0042] The unbalanced Mach-Zehnder interferometer 4 is an instrument that generates dual beams by using the amplitude division method to achieve interference, and can generate dual-path echoes based on a single-path echo to achieve interference.

[0043] As an optional implementation, the receiving component 9 includes: an avalanche photodetector 901 , an AD collector 902 , and a data analyzer 903 connected in sequence.

[0044] like Figure 1-4 As shown, the echo signal directly output from the circulator 7 or output from the interferometer 4 enters the avalanche photodetector 901 for photoelectric conversion to output an electrical signal. The electrical signal is converted into a digital signal and sampled by the AD collector 902, and then input into the data analyzer for data analysis to obtain the sound detection result.

[0045] The present invention also provides a sound detection method, which uses the above-mentioned distributed optical fiber sound sensing system to perform sound detection. Figure 5 is a flow chart of a sound detection method provided by an embodiment of the present invention, such as Figure 5 As shown, including: S1, dividing the initial laser into a first laser beam and a second laser beam; The laser source component emits an initial laser, which is divided into a first laser beam and a second laser beam after passing through a coupler.

[0046] S2, pulse modulating the first laser beam to obtain a single pulse laser; The first laser beam is electrically modulated by a single pulse through an acousto-optic modulator to obtain a single pulse laser.

[0047] S3, after interfering and amplifying the single pulse laser, transmitting it to the sensing optical fiber, receiving the echo signal of the sensing optical fiber, and analyzing the echo signal to obtain the pending sound information; or after amplifying the single pulse laser, transmitting it to the sensing optical fiber, receiving the echo signal of the sensing optical fiber, interfering and analyzing the echo signal to obtain the pending sound information; like Figure 1 As shown, if the interferometer is arranged between the acousto-optic modulator and the interferometer, a single-pulse laser is first input through the first input end (A port) of the interferometer, and then a double-pulse laser is output through the first output end (C port). The double-pulse laser is amplified by the erbium-doped fiber amplifier and then input into the sensing fiber through the circulator. The echo signal output by the sensing fiber enters the receiving component through the circulator for analysis to obtain the pending sound information.

[0048] like Figure 2As shown, if the interferometer is arranged between the circulator and the receiving component, the single pulse laser is directly amplified by the erbium-doped fiber amplifier and then input into the sensing fiber through the circulator. The echo signal output by the sensing fiber enters the second input port (D port) of the interferometer through the circulator, and after interference, it is output to the receiving component through the second output port (B port) for analysis to obtain the pending sound information.

[0049] S4. Interfere the second laser beam to obtain interference light; adjust the frequency of the laser source assembly according to the intensity value of the interference light and a reference value; repeat this step until the difference between the intensity value and the reference value is within a preset difference range, and take the pending sound information in the corresponding time period at the current moment as reliable sound information; wherein the reference value is pre-set according to the laser source assembly.

[0050] After the second laser beam is interfered by the interferometer, interference light is obtained. After the interference light enters the feedback component, it is calculated with the reference value to obtain the adjustment frequency of the laser source component and adjust the laser source component accordingly. Repeat the interference light intensity detection and frequency correction until the intensity value is close to the reference value (the difference between the intensity value and the reference value is within the preset difference range), and the pending sound information in the time period corresponding to the current moment can be used as reliable sound information. The determination of the time period can be achieved through a preset time range. For example, the current moment is the middle value, and the pending sound information in the time range before and after it is all reliable sound information; or, the pending sound information in the time range before the current moment is all reliable sound information; or, the pending sound information in the time range after the current moment is all reliable sound information. This time range can be set in advance.

[0051] The processing process of the first laser beam and the processing process of the second laser beam are parallel and continuous.

[0052] Reference value I 0 The combined state of the fiber ring and the laser frequency, i.e. the reference state of the stable interference of the laser double pulses, is in principle 0 The selection of can be any value of the measured interference value, but considering the control efficiency and effect, I 0 The value of should be selected to maximize |dI / df| (f is the frequency of the laser source).

[0053] As an optional implementation, Figure 6 is a flow chart of a frequency adjustment method provided by an embodiment of the present invention. Figure 6 As shown, the frequency of the laser source component is adjusted according to the intensity value of the interference light and the reference value, including: S401, calculating a frequency correction signal according to the intensity value of the interference light and a reference value; S402, adjusting the frequency corresponding to the laser source component according to the frequency correction signal.

[0054] Get the intensity value I of the collected interference light, and calculate the current intensity value I and the preset reference value I 0 The frequency correction signal U (I, I 0 ), the calculation relationship between the two can be obtained through a simulation test in advance, or it can be calculated through a function (such as PID control).

[0055] According to the correction signal U(I, I 0 )Adjust the frequency of the laser source component. For example, the correction value obtained by the PID control algorithm is Δf. If it is greater than 0, the frequency |Δf| is increased, and if it is less than 0, the frequency |Δf| is decreased.

[0056] As an optional implementation, Figure 7 : is a flow chart of a sound echo signal processing method provided by an embodiment of the present invention, which analyzes the echo signal and includes: S301, performing photoelectric conversion on the echo signal to obtain an electrical signal; S302, performing signal analysis after AD acquisition on the electrical signal to obtain pending sound information.

[0057] The echo signal directly output from the circulator or output from the interferometer enters the avalanche photodetector for photoelectric conversion to output an electrical signal. The electrical signal is converted into a digital signal and sampled by the AD collector, and then input into the data analyzer for data analysis to obtain the pending sound information.

[0058] An embodiment of the present invention further provides a distributed optical fiber sound sensing device, including the above-mentioned distributed optical fiber sound sensing system.

[0059] An embodiment of the present invention further provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the above-mentioned sound detection method is implemented.

[0060] The above storage media include but are not limited to: CDs, floppy disks, hard disks, erasable memory, etc.

[0061] The above technical solution has the following beneficial effects: by utilizing part of the laser output from the laser source to inject into the optical fiber ring that generates the dual-pulse laser, reverse optical interference is formed. The laser frequency in the reverse interference process and the interference process between the interference arm and the dual-pulse echo of the main laser are completely equivalent. Therefore, by detecting the intensity of the reverse interference light and then controlling the feedback signal of the laser frequency or the laser modulation frequency, the intensity of the reverse interference light can be stabilized, and the system noise caused by various jitters in the conventional dual-pulse distributed optical fiber sensor can be eliminated. The influence of the light source phase noise on the system noise can also be eliminated to a certain extent (equivalently compressing the laser line width of the light source), which improves the signal-to-noise ratio of the sensor as a whole, is conducive to detecting weaker vibration signals, and improves detection accuracy.

[0062] The specific implementation methods of the above invention further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above content is only the specific implementation methods of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A distributed optical fiber sound sensing system, characterized in that: include: A laser source assembly, the laser source assembly being used to generate continuous initial laser light; A coupler, the input end of the coupler is connected to the output end of the laser source assembly, and is used to split the initial laser into a first laser beam and a second laser beam; an acousto-optic modulator, wherein the input end of the acousto-optic modulator is connected to an output end of the coupler, and the output end is connected to the first input end of the interferometer or the input end of the erbium-doped amplifier, and is used to modulate the first laser beam into a single-pulse laser; When the output end of the acousto-optic modulator is connected to the first input end of the interferometer, the first output end of the interferometer is connected to the input end of the erbium-doped fiber amplifier; the second input end of the interferometer is connected to the other output end of the coupler through an isolator, and the second output end is connected to the laser source assembly through a feedback assembly, for converting the second laser beam into interference light, and adjusting the frequency of the laser source assembly according to a reference value and an intensity value of the interference light; the output end of the erbium-doped fiber amplifier is connected to the first port of the circulator; the second port of the circulator is connected to the sensing optical fiber, and the third port is connected to the receiving assembly; When the output end of the acousto-optic modulator is connected to the input end of the erbium-doped amplifier, the output end of the erbium-doped fiber amplifier is connected to the first port of the circulator; the second port of the circulator is connected to the sensing fiber, and the third port is connected to the second input end of the interferometer; the second output end of the interferometer is connected to the receiving component; the first input end of the interferometer is connected to the other output end of the coupler through the isolator, and the first output end is connected to the laser source component through the feedback component, so as to receive the second laser beam and convert it into interference light, and adjust the frequency of the laser source component according to the reference value and the intensity value of the interference light.

2. The distributed optical fiber sound sensing system according to claim 1, characterized in that: The laser source assembly includes: a laser source; The output end of the laser source is connected to the input end of the coupler, and the input end is connected to the output end of the feedback component, for generating the initial laser; Or, the laser source assembly includes: a laser source and an acousto-optic frequency shifter; The output end of the laser source is connected to the input end of the coupler, and the input end is connected to the output end of the acousto-optic frequency shifter, for generating the initial laser; An acousto-optic frequency shifter, wherein the input end of the acousto-optic frequency shifter is connected to the output end of the feedback component, and the output end is connected to the laser source, and is used to shift the frequency of the laser source.

3. The distributed optical fiber sound sensing system according to claim 2, characterized in that: The feedback component includes: A photoelectric detector, the input end of which is connected to the output end of the interferometer, and is used to detect the intensity value of the interference light; A feedback controller, wherein the input end of the feedback controller is connected to the output end of the photodetector, and the output end is connected to the laser source or the acousto-optic modulator, and is used to calculate a frequency correction signal according to the intensity value and the reference value, and control and adjust the frequency of the laser source or the acousto-optic frequency shifter according to the correction signal.

4. The distributed optical fiber sound sensing system according to claim 2, characterized in that: The laser source is a narrow line width laser seed source; The interferometer is an unbalanced Mach-Zehnder interferometer.

5. The distributed optical fiber sound sensing system according to claim 1, characterized in that: The receiving component includes: Avalanche photodetector, AD collector and data analyzer.

6. A sound detection method, characterized in that: The distributed optical fiber sound sensing system according to any one of claims 1 to 5 is used for sound detection, comprising: Splitting the initial laser into a first laser beam and a second laser beam; Pulse-modulating the first laser beam to obtain a single-pulse laser; The single pulse laser is interfered and amplified and then transmitted to the sensing optical fiber, an echo signal of the sensing optical fiber is received, and the echo signal is analyzed to obtain the pending sound information; or the single pulse laser is amplified and then transmitted to the sensing optical fiber, an echo signal of the sensing optical fiber is received, and the echo signal is interfered and analyzed to obtain the pending sound information; Interfere the second laser beam to obtain interference light; adjust the frequency of the laser source assembly according to the intensity value of the interference light and a reference value; repeat this step until the difference between the intensity value and the reference value is within a preset difference range, and take the pending sound information in the corresponding time period at the current moment as reliable sound information; wherein the reference value is pre-set according to the laser source assembly.

7. The sound detection method according to claim 6, characterized in that: The step of adjusting the frequency of the laser source assembly according to the intensity value of the interference light and the reference value comprises: Calculate a frequency correction signal according to the intensity value of the interference light and a reference value; The frequency corresponding to the laser source component is adjusted according to the frequency correction signal.

8. The sound detection method according to claim 6, characterized in that: The analyzing the echo signal comprises: Performing photoelectric conversion on the echo signal to obtain an electrical signal; After AD acquisition of the electrical signal, signal analysis is performed to obtain the pending sound information.

9. A distributed optical fiber sound sensing device, characterized in that: It comprises a distributed optical fiber sound sensing system as described in any one of claims 1 to 5.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the sound detection method as described in any one of claims 6 to 8 is implemented.

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