Phase-shifted fiber grating ultrasonic detection system and method based on optoelectronic oscillator, terminal and medium

Abstract

This invention provides an ultrasonic detection system, method, terminal, and medium based on a phase-shifted fiber optic grating using an optoelectronic oscillator, relating to the field of microwave photonic fiber optic sensing technology. The system includes a laser, a polarization controller, an optoelectronic self-excited oscillation loop, a phase-shifted fiber optic grating, a down-conversion module, and a high-speed data acquisition module. The laser generates a laser signal, which is output to the loop after passing through the polarization controller. When the grating connected to one end of the optical circulator in the loop experiences a phase shift peak shift due to the ultrasonic signal, the loop splits the beam and outputs two target microwave signals. One signal is sent to a phase modulator to maintain oscillation conditions, while the other signal is processed by the down-conversion module and then acquired and analyzed by the high-speed data acquisition module to obtain and analyze the frequency domain sideband modulation signal. Demodulation is used to recover and quantitatively detect the ultrasonic signal. By converting the optical wavelength shift into the modulation characteristics of the electrical domain microwave signal through the loop, the limitations of traditional measurement ranges are overcome, and environmental temperature interference can be suppressed.

Description

Technical Field

[0001] This invention relates to the field of microwave photonic fiber optic sensing technology, and more particularly to a phase-shifted fiber optic grating ultrasonic testing system, method, terminal, and medium based on an optoelectronic oscillator. Background Technology

[0002] Currently, in the dynamic demodulation of fiber optic sensors, the wavelength shift of fiber optic gratings caused by ultrasonic signals can usually be demodulated with high precision and speed using sideband filtering. However, this method suffers from the problem of difficulty in locking the sensor's operating point (Q-point), and is easily affected by factors such as ambient temperature. On the other hand, while the common three-wavelength phase demodulation scheme can avoid the influence of Q-point shift and achieve fast demodulation, it is also difficult to apply directly due to the narrow spectral linewidth of the phase-shifted fiber optic grating. In other words, there is a contradiction between pursuing high sensitivity and stable large dynamic range measurement in traditional optical demodulation methods. Although the sideband filtering method has high sensitivity, the operating point is prone to lock-up, while the three-wavelength method is stable, but achieving high sensitivity is difficult.

[0003] Therefore, existing technologies have shortcomings and need to be improved and developed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a phase-shifted fiber optic grating ultrasonic detection system, method, terminal and medium based on photoelectric oscillator, which can convert the wavelength shift in the optical domain into the modulation characteristics of the microwave signal in the electrical domain through photoelectric self-excited oscillation loop, thereby realizing the recovery and quantitative detection of ultrasonic signals, thus breaking through the limitations of traditional measurement range and suppressing environmental temperature interference.

[0005] The technical solution adopted by this invention to solve the technical problem is as follows:

[0006] In a first aspect, the present invention also discloses a phase-shifted fiber Bragg grating ultrasonic detection system based on a photoelectric oscillator, wherein the system comprises:

[0007] The phase-shifting fiber grating ultrasonic testing system includes a laser, a polarization controller, a photoelectric self-excited oscillation loop, a phase-shifting fiber grating, a down-conversion module, and a high-speed data acquisition module.

[0008] A laser is used to generate a single-wavelength laser signal and output it to a polarization controller.

[0009] A polarization controller is used to adjust the polarization state of the single-wavelength laser signal to match the optimal operating conditions of the phase modulator in the photoelectric self-excited oscillation loop, and outputs the signal to the photoelectric self-excited oscillation loop.

[0010] A phase-shifted fiber optic grating connected to one end of the optical circulator in the photoelectric self-excited oscillation loop is used to sense ultrasonic signals.

[0011] The optoelectronic self-excited oscillation loop is used to split the beam and output two target microwave signals when the phase shift peak is shifted by an externally applied ultrasonic signal to the phase-shifted fiber grating. One target microwave signal is output to the phase modulator to maintain the oscillation condition of the optoelectronic self-excited oscillation loop, and the other target microwave signal is output to the down-conversion module.

[0012] The downconversion module is used to receive another target microwave signal output from the photoelectric self-excited oscillation loop, and to perform frequency mixing processing on the other target microwave signal and the local oscillator signal to obtain the mixed microwave signal.

[0013] The high-speed data acquisition module is used to acquire and digitize the mixed microwave signal output by the downconversion module in real time to obtain a digital signal. The digital signal is then subjected to fast Fourier transform to determine the variation characteristics of the frequency domain sideband intensity. Based on the variation characteristics of the frequency domain sideband intensity, the digital signal is demodulated to extract the corresponding amplitude and phase information, thereby obtaining the demodulation result and detection result of the ultrasonic signal.

[0014] Optionally, the photoelectric self-excited oscillation loop is composed of a phase modulator, an optical circulator, an optical amplifier, a photodetector, a microwave power amplifier, and a microwave power beam splitter.

[0015] A phase modulator is used to phase modulate the single-wavelength laser signal after it has passed through a polarization controller, and to output the modulated laser signal to an optical circulator.

[0016] An optical circulator is used to output the modulated laser signal input from the phase modulator to the phase-shifted fiber grating, and to receive the laser signal after passing through the phase-shifted fiber grating.

[0017] An optical amplifier is used to amplify the laser signal output from an optical circulator after passing through a phase-shifted fiber grating.

[0018] A photodetector is used to convert the amplified laser signal output by an optical amplifier into an electrical signal, thereby obtaining a corresponding microwave signal.

[0019] A microwave power amplifier is used to amplify the microwave signal output from a photodetector and transmit it to a microwave power beam splitter.

[0020] A microwave power beam splitter is used to split the amplified microwave signal output from a microwave power amplifier, and output one target microwave signal to a phase modulator and the other target microwave signal to a downconversion module.

[0021] Optionally, the phase-shifted fiber grating is also used to filter out a preset modulation frequency from the modulated laser signal input to the optical circulator.

[0022] Optionally, the laser is a wavelength-tunable narrow linewidth laser.

[0023] Optionally, the phase-shifted fiber grating is a π-phase-shifted fiber grating.

[0024] Optionally, the photodetector is specifically used to control the amplified laser signal output by the optical amplifier to beat with the single-wavelength laser signal to obtain a microwave signal.

[0025] Optionally, when the phase-shifting fiber grating is subjected to an externally applied ultrasonic signal, the ultrasonic signal generates dynamic stress on the phase-shifting fiber grating, causing a shift in the phase-shifting peak of the phase-shifting fiber grating. The relationship between the center wavelength of the phase-shifting peak of the phase-shifting fiber grating and the dynamic stress is as follows:

[0026] ;

[0027] in, For the effective elastic coefficient, For dynamic stress, The center wavelength of the phase-shifted fiber grating when it is stress-free.

[0028] Secondly, this invention discloses an ultrasonic detection method based on a phase-shifted fiber optic grating using a photoelectric oscillator, the method comprising:

[0029] When the phase-shifting fiber grating in the phase-shifting fiber grating ultrasonic testing system based on photoelectric oscillator as described above is subjected to an externally applied ultrasonic signal, causing a phase shift peak shift, the down-conversion module of the ultrasonic testing system receives another target microwave signal output from the photoelectric self-excited oscillation loop, and mixes the other target microwave signal with the local oscillator signal to obtain a mixed microwave signal.

[0030] The high-speed data acquisition module performs real-time acquisition and digital processing on the mixed microwave signal output by the downconversion module to obtain a digital signal.

[0031] The digitized signal is acquired, and a fast Fourier transform is performed on the digitized signal to determine the variation characteristics of the frequency domain sideband intensity.

[0032] Based on the variation characteristics of the frequency domain sideband intensity, the digital signal is demodulated, and the corresponding amplitude and phase information are extracted to obtain the demodulation result and detection result of the ultrasonic signal.

[0033] Thirdly, the present invention discloses a terminal, comprising: a memory, a processor, and an ultrasonic testing program for a phase-shifted fiber grating based on an optoelectronic oscillator stored in the memory and executable on the processor. When the ultrasonic testing program for a phase-shifted fiber grating based on an optoelectronic oscillator is executed by the processor, it implements the steps of the ultrasonic testing method for a phase-shifted fiber grating based on an optoelectronic oscillator as described above.

[0034] Fourthly, the present invention discloses a computer-readable storage medium storing a computer program that can be executed to implement the steps of the phase-shifted fiber Bragg grating ultrasonic detection method based on an optoelectronic oscillator as described above.

[0035] This invention provides a phase-shifted fiber grating ultrasonic testing system, method, terminal, and medium based on an optoelectronic oscillator. The phase-shifted fiber grating ultrasonic testing system includes a laser, a polarization controller, an optoelectronic self-excited oscillation loop, a phase-shifted fiber grating, a down-conversion module, and a high-speed data acquisition module. The laser generates a single-wavelength laser signal and outputs it to the polarization controller. The polarization controller adjusts the polarization state of the single-wavelength laser signal to match the optimal operating conditions of the phase modulator in the optoelectronic self-excited oscillation loop and outputs it to the optoelectronic self-excited oscillation loop. A phase-shifting fiber grating connected to one end of an optical circulator is used to sense ultrasonic signals. A photoelectric self-excited oscillation loop is used to split the phase-shifting fiber grating into two target microwave signals when the phase-shifting peak shifts due to an externally applied ultrasonic signal. One target microwave signal is output to a phase modulator to maintain the oscillation conditions of the photoelectric self-excited oscillation loop, and the other target microwave signal is output to a down-conversion module. The down-conversion module receives the other target microwave signal output from the photoelectric self-excited oscillation loop and mixes it with a local oscillator signal to obtain a mixed microwave signal. A high-speed data acquisition module is used to acquire and digitize the mixed microwave signal output from the down-conversion module in real time to obtain a digital signal. This digital signal is then subjected to a Fast Fourier Transform (FFT) to determine the frequency domain sideband intensity variation characteristics. Based on these characteristics, the digital signal is demodulated to extract the corresponding amplitude and phase information, resulting in the demodulation and detection results of the ultrasonic signal.

[0036] Therefore, this invention converts the wavelength shift in the optical domain into the modulation characteristics of the microwave signal in the electrical domain through a photoelectric self-excited oscillation loop. That is, when an ultrasonic signal acts on a phase-shifted fiber grating, it causes a shift in its phase shift peak, thereby changing the frequency of the filtered sidebands and modulating the output spectrum of the photoelectric self-excited oscillation loop. Then, through a down-conversion module and a high-speed data acquisition module, it achieves high-precision and high-stability ultrasonic signal recovery, demodulation, and quantitative detection, breaking through the limitations of traditional measurement ranges and possessing advantages such as resistance to environmental temperature interference, significantly improving the stability and resolution of ultrasonic signal detection. Attached Figure Description

[0037] Figure 1 This is a functional principle block diagram of a phase-shifted fiber optic grating ultrasonic testing system based on an optoelectronic oscillator disclosed in this invention;

[0038] Figure 2 This is a schematic diagram of a specific demodulated spectral response disclosed in this invention;

[0039] Figure 3 This is a schematic diagram of a specific ultrasonic intensity time-domain signal obtained based on IQ demodulation disclosed in this invention;

[0040] Figure 4 This is a schematic diagram illustrating the variation of the amplitude of the restored ultrasound signal with the driving voltage, as disclosed in this invention.

[0041] Figure 5 This is a flowchart of an ultrasonic testing method for phase-shifted fiber optic gratings based on photoelectric oscillators disclosed in this invention;

[0042] Figure 6 This is a functional principle block diagram of a preferred embodiment of the terminal in this invention;

[0043] Explanation of reference numerals in the attached figures:

[0044] 1-Laser, 2-Polarization controller, 3-Phase modulator, 4-Optical circulator, 5-Phase-shifting fiber optic grating, 6-Optical amplifier, 7-Photodetector, 8-Microwave power amplifier, 9-Microwave power beam splitter, 10-Down-conversion module, 11-High-speed data acquisition module, C-Photoelectric self-excited oscillation loop. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0046] Currently, fiber optic sensors possess significant application potential in the field of ultrasonic sensing due to their unique advantages such as high sensitivity, resistance to electromagnetic interference, and small size. Among them, the π phase-shift fiber grating sensor, as a wavelength modulation type fiber optic sensor, obtains ultrasonic information by modulating the wavelength of the phase-shift fiber grating with external ultrasonic pressure. This type of sensor combines advantages not found in traditional sensors, such as resistance to electromagnetic interference, good electrical insulation, small size, light weight, and wide frequency response.

[0047] However, in fiber optic sensing dynamic demodulation, the wavelength shift of fiber optic gratings caused by ultrasonic signals can usually be demodulated quickly and with high precision using sideband filtering. However, this method suffers from the difficulty in locking the sensor's operating point (Q-point), making it susceptible to interference from factors such as ambient temperature. On the other hand, while the common three-wavelength phase demodulation scheme can avoid the influence of Q-point shift and achieve rapid demodulation, it is also difficult to apply directly due to the narrow spectral linewidth of the π-phase-shifted fiber optic grating. In other words, traditional optical demodulation methods present a contradiction between pursuing high sensitivity and stable large dynamic range measurement. While sideband filtering offers high sensitivity, the operating point is prone to lock-up, and while the three-wavelength method is stable, achieving high sensitivity is difficult.

[0048] Optical oscillators (OEOs) combine microwave and photonic technologies to generate high-frequency microwave signals with ultra-low phase noise. They have advantages such as resistance to electromagnetic interference, high frequency stability, low phase noise, and low power consumption, and can be applied in microwave signal processing, communication, and optical sensing.

[0049] Applying OEO technology to wavelength demodulation of π phase-shift fiber optic grating sensors can convert wavelength-domain signals into frequency-domain signals, enabling faster and more accurate detection by utilizing the relatively low frequency of microwave signals. Therefore, OEO technology can be applied to π phase-shift grating demodulation.

[0050] To address this, this application provides a phase-shifted fiber optic grating ultrasonic testing system based on an optoelectronic oscillator. This system converts the wavelength shift in the optical domain into modulation characteristics of a microwave signal in the electrical domain through a self-excited optoelectronic oscillation loop, thereby enabling the recovery and quantitative detection of ultrasonic signals. This method overcomes the limitations of traditional measurement ranges and offers advantages such as resistance to environmental temperature interference. It also solves the Q-point stability problem of the sideband filtering method and the compatibility issue of the three-wavelength method with the grating spectrum, achieving highly stable, high-resolution, and high-speed ultrasonic testing.

[0051] This application discloses a phase-shifted fiber Bragg grating ultrasonic testing system based on a photoelectric oscillator, the structure of which is as follows: Figure 1 As shown, the phase-shifting fiber grating ultrasonic testing system includes a laser 1, a polarization controller 2, a photoelectric self-excited oscillation loop C, a phase-shifting fiber grating 5, a down-conversion module 10, and a high-speed data acquisition module 11.

[0052] Laser 1 is used to generate a single-wavelength laser signal and output it to polarization controller 2.

[0053] The polarization controller 2 is used to adjust the polarization state of the single-wavelength laser signal to match the optimal operating conditions of the phase modulator 3 in the photoelectric self-excited oscillation loop C, and outputs it to the photoelectric self-excited oscillation loop C.

[0054] A phase-shifted fiber optic grating 5, connected to one end of the optical circulator 4 in the photoelectric self-excited oscillation loop C, is used to sense ultrasonic signals.

[0055] The photoelectric self-excited oscillation loop C is used to split the beam and output two target microwave signals when the phase shift peak is shifted due to the action of an externally applied ultrasonic signal on the phase shift fiber grating 5. One target microwave signal is output to the phase modulator to maintain the oscillation condition of the photoelectric self-excited oscillation loop, and the other target microwave signal is output to the down-conversion module 10.

[0056] The downconversion module 10 is used to receive another target microwave signal output from the photoelectric self-excited oscillation loop C, and to perform frequency mixing processing on the other target microwave signal and the local oscillator signal to obtain the mixed microwave signal.

[0057] The high-speed data acquisition module 11 is used to acquire and digitize the mixed microwave signal output by the downconversion module 10 in real time to obtain a digital signal, so as to perform fast Fourier transform processing on the digital signal, determine the variation characteristics of the frequency domain sideband intensity, and demodulate the digital signal based on the variation characteristics of the frequency domain sideband intensity to extract the corresponding amplitude information and phase information, thereby obtaining the demodulation result and detection result of the ultrasonic signal.

[0058] Specifically, the downconversion module 10 receives another target microwave signal output from the photoelectric self-excited oscillation loop C. Then, it uses a mixer to mix this other target microwave signal with a local oscillator signal, shifting the signal spectrum and reducing the high-frequency microwave signal to a suitable intermediate frequency signal for sampling—the mixed microwave signal. Furthermore, based on the variation characteristics of the frequency domain sideband intensity, the IQ demodulation algorithm is used to demodulate the digital signal, extracting its amplitude and phase information, ultimately achieving precise demodulation and quantitative detection of the ultrasonic signal.

[0059] Furthermore, the photoelectric self-excited oscillation loop C consists of a phase modulator 3, an optical circulator 4, an optical amplifier 6, a photodetector 7, a microwave power amplifier 8, and a microwave power beam splitter 9.

[0060] Phase modulator 3 is used to perform phase modulation on the single-wavelength laser signal after passing through polarization controller 2, and output the modulated laser signal to optical circulator 4;

[0061] The optical circulator 4 is used to output the modulated laser signal input from the phase modulator 3 to the phase-shifted fiber grating 5, and to receive the laser signal after passing through the phase-shifted fiber grating 5.

[0062] Optical amplifier 6 is used to amplify the laser signal output from optical circulator 4 after passing through phase-shifted fiber grating 5;

[0063] The photodetector 7 is used to convert the amplified laser signal output from the optical amplifier 6 into an electrical signal to obtain the corresponding microwave signal.

[0064] Microwave power amplifier 8 is used to amplify the microwave signal output by photodetector 7 and transmit it to microwave power beam splitter 9.

[0065] The microwave power beam splitter 9 is used to split the amplified microwave signal output from the microwave power amplifier 8, and output one target microwave signal to the phase modulator 3, and the other target microwave signal to the downconversion module 10.

[0066] The phase-shifting fiber grating 5 is also used to filter out the preset modulation frequency in the modulated laser signal input to the optical circulator 4.

[0067] The specific connection of the phase-shift fiber grating ultrasonic testing system is described above. Figure 1 As shown, specifically, the output terminal of laser 1 is connected to the input terminal of polarization controller 2, and the output terminal of polarization controller 2 is connected to the optical input terminal of phase modulator 3 in photoelectric self-excited oscillation loop C. Furthermore, the two output terminals of photoelectric self-excited oscillation loop C are respectively connected to the RF input terminal of phase modulator 3 and the input terminal of down-conversion module 10. The output terminal of down-conversion module 10 is connected to the input terminal of high-speed data acquisition module 11. Furthermore, the output of polarization controller 2 is connected to the optical input of phase modulator 3, port a of optical circulator 4 is connected to the output of phase modulator 3, one end of π phase-shifted fiber grating 5 is connected to port b of optical circulator 4, the input of optical amplifier 6 is connected to port c of optical circulator, the output of optical amplifier 6 is connected to the input of photodetector 7, the output of photodetector 7 is connected to the input of microwave power amplifier 8, the output of microwave power amplifier 8 is connected to the input of microwave power beam splitter 9, the first output of microwave power beam splitter 9 is connected to the radio frequency input of phase modulator 3, and the second output of microwave power beam splitter 9 is connected to the input of down-conversion module 10.

[0068] Furthermore, laser 1 can be a wavelength-tunable narrow linewidth laser, and phase-shifting fiber grating 5 can be a π phase-shifting fiber grating.

[0069] Understandably, the wavelength-tunable narrow-linewidth laser 1 outputs single-wavelength laser light. The input terminal of the polarization controller 2 is connected to the output terminal of the wavelength-tunable narrow-linewidth laser 1 to adjust the polarization state of the output light, matching the optimal operating conditions of the phase modulator 3. The optical input terminal of the phase modulator 3 is connected to the output terminal of the polarization controller 2 to perform phase modulation on the input optical signal. The a-terminal of the three-port optical circulator 4 is connected to the output terminal of the phase modulator 3 to receive the phase-modulated optical signal. One end of the π-phase-shifted fiber grating 5 is connected to the b-terminal of the optical circulator to filter out specific modulation frequencies in the modulated optical signal, achieve loop oscillation, and is used to sense ultrasonic signals. The input terminal of the optical amplifier 6 is connected to the c-terminal of the optical circulator to amplify the signal after the π-phase-shifted fiber grating. The optical signal after the fiber grating 5 is made more prone to oscillation; the input end of the photodetector 7 is connected to the output end of the optical amplifier 6 to realize photoelectric signal conversion; the input end of the microwave power amplifier 8 is connected to the output end of the photodetector 7 to amplify the microwave signal generated by the beat frequency in the photodetector 7; the input end of the microwave power beam splitter 9 is connected to the output end of the microwave power amplifier 8, and the first output end of the microwave power beam splitter 9 is connected to the radio frequency input end of the phase modulator 3 to realize the feedback oscillation loop; the input end of the downconversion module 10 is connected to the second output end of the microwave power beam splitter 9 to perform downconversion processing on the microwave signal; the input end of the downconversion module 10 is connected to the input end of the high-speed data acquisition module 11 to recover, demodulate and quantitatively detect the ultrasonic signal.

[0070] In this embodiment, the aforementioned components form a self-excited oscillation through the photoelectric self-excited oscillation loop C. When the high-frequency ultrasound causes a rapid wavelength shift in the phase-shifting fiber optic grating, the system adaptively adjusts the microwave frequency to maintain the oscillation conditions, thereby modulating the ultrasonic signal onto the output signal of the photoelectric oscillator (OEO). By recovering the phase and intensity changes of the ultrasonic signal through the high-speed data acquisition module 11, quantitative detection of the ultrasonic signal can be achieved. This architecture effectively avoids the problem of traditional sideband filtering methods being susceptible to environmental interference, and can achieve high-precision and high-stability ultrasonic signal demodulation.

[0071] Furthermore, the photodetector 7 is specifically used to control the amplified laser signal output by the optical amplifier 6 to beat with the single-wavelength laser signal to obtain a microwave signal.

[0072] For example, a wavelength-tunable narrow-linewidth laser 1 generates a single-wavelength optical carrier ω0. After the polarization state is adjusted by a polarization controller 2, the signal is input to a phase modulator 3 for modulation. The modulated laser signal generates multiple pairs of upper and lower sideband signals with equal intensity and opposite phase, i.e., ω0±ω. mThe upper and lower sideband signals enter the π phase-shift fiber grating 5 through the optical circulator 4. In the initial state, by adjusting the wavelength of the wavelength-tunable narrow-linewidth laser 1, a specific upper sideband ω0+ω is achieved. m Precisely align the phase shift peak of the grating's reflection spectrum, the upper sideband ω0+ω m It is filtered out, and its corresponding lower sideband ω0 ω m Then it passes completely through the grating, that is, when a certain upper sideband signal ω0+ω m When at the phase shift peak of the reflection spectrum of the π phase-shifted fiber grating 5, the upper sideband signal ω0+ω m The phase shift peak will be filtered out by a narrowband filter, and the corresponding lower sideband signal ω0 ω m The optical signal is amplified by optical amplifier 6 after passing through optical circulator 4. The amplified optical signal beats with the original optical carrier ω0 in photodetector 7, generating a frequency ω. m The microwave signal is amplified by microwave power amplifier 8 and then split into two paths by microwave power beam splitter 9: one path is fed back to phase modulator 3 to form photoelectric self-excited oscillation loop C, and the other path is output to down-conversion module 10 for signal down-conversion processing. The signal is then input to high-speed data acquisition module 11 for signal analysis and demodulation. When the ultrasonic signal acts on the π-phase-shift fiber grating 5, it causes a shift in its phase shift peak, thereby changing the frequency of the filtered sidebands and modulating the output spectrum of the OEO. Through this mechanism, the wavelength change in the optical domain is converted into a change in the microwave frequency in the electrical domain, achieving high-precision measurement of ultrasound.

[0073] Therefore, when the phase-shifting fiber grating 5 is subjected to an externally applied ultrasonic signal, the ultrasonic signal generates dynamic stress on the phase-shifting fiber grating 5, causing the phase-shifting peak of the phase-shifting fiber grating 5 to shift. The relationship between the center wavelength of the phase-shifting peak of the phase-shifting fiber grating 5 and the dynamic stress is as follows:

[0074] ;

[0075] in, For the effective elastic coefficient, For dynamic stress, The center wavelength of the phase-shifted fiber grating when it is stress-free.

[0076] It should be noted that in this phase-shift fiber grating ultrasonic testing system, the output frequency of the photoelectric oscillator... f M The frequency of the optical carrier f c Phase shift peak frequency of phase-shifted fiber grating f B They jointly decided that their relationship is as follows:

[0077] ;

[0078] in, λ c λ is the wavelength of the optical carrier wave, and c is the speed of light in a vacuum.

[0079] It should also be noted that in actual ultrasonic sensing processes, the key conversion mechanism does not directly change f M It is caused by ultrasound. λ B The dynamic shift of (t) directly translates into periodic power loss in the photoelectric self-excited oscillation loop C, thereby modulating the intensity of the output microwave signal. This is because the phase shift peak and the upper sideband become detuned during ultrasonic action, resulting in poorer filtering of the upper sideband and decreased transmittance of the lower sideband. These two effects together introduce a time-varying intensity loss α(t) in the optical path, synchronized with the ultrasonic wave. This loss directly reduces the net gain of the photoelectric self-excited oscillation loop C, thereby modulating the amplitude of the output microwave signal. By detecting the intensity modulation information of this microwave signal, the original ultrasonic signal can be demodulated.

[0080] For example, the spectral response obtained after applying an ultrasonic signal to a π-phase-shift fiber Bragg grating using a 1MHz immersion ultrasonic probe and demodulating it using an opto-oscillator (OEO) is shown in [reference needed]. Figure 2 As shown, from Figure 2 As can be observed, a clear ultrasonic modulation sideband appears at a frequency of 1 MHz next to the main oscillation peak of the photoelectric oscillator, and its frequency is completely consistent with the applied ultrasonic signal. By performing IQ demodulation analysis on this sideband signal, quantitative detection of the ultrasonic signal can be achieved.

[0081] It should be noted that when the π-phase-shifted fiber grating is affected by environmental factors such as temperature, the main oscillation frequency of the OEO will drift, but the ultrasonic modulation sideband will move synchronously. Therefore, by continuously tracking the sideband signal, the ultrasonic information can be stably demodulated without relying on the absolute position of the main oscillation frequency. This characteristic significantly reduces the impact of environmental interference, indicating that the demodulation scheme has good anti-interference capability and practical value.

[0082] In practical applications, it is necessary to obtain the time-domain information of the ultrasonic signal. (See [reference needed]) Figure 3 As shown, the IQ demodulation algorithm can be used to invert the ultrasonic signal, reconstruct the ultrasonic waveform in the time domain, and obtain the ultrasonic intensity time domain signal.

[0083] Furthermore, by varying the driving voltage applied to the ultrasonic generator (PZT probe), ultrasonic signals with different sound pressure levels were generated. The corresponding signal recovery intensity changes are shown in [reference needed]. Figure 4As shown, with the increase of driving voltage, the intensity of the detected ultrasonic signal gradually increases, and it exhibits good linear response characteristics.

[0084] In one embodiment, such as Figure 5 As shown, based on the above-described ultrasonic testing system for phase-shifted fiber gratings based on photoelectric oscillators, this invention also provides a corresponding ultrasonic testing method for phase-shifted fiber gratings based on photoelectric oscillators, comprising:

[0085] Step S11: When the phase-shifting fiber grating in the phase-shifting fiber grating ultrasonic testing system based on the photoelectric oscillator, as described above, is subjected to an externally applied ultrasonic signal, causing a phase shift peak shift, the down-conversion module in the ultrasonic testing system receives another target microwave signal output from the photoelectric self-excited oscillation loop, and mixes the other target microwave signal with the local oscillator signal to obtain a mixed microwave signal.

[0086] Step S12: The microwave signal after mixing output by the downconversion module is acquired and digitized in real time through the high-speed data acquisition module to obtain a digital signal.

[0087] Step S13: Acquire the digitized signal and perform Fast Fourier Transform on the digitized signal to determine the variation characteristics of the frequency domain sideband intensity.

[0088] Step S14: Demodulate the digital signal based on the variation characteristics of the frequency domain sideband intensity, extract the corresponding amplitude information and phase information, and obtain the demodulation result and detection result of the ultrasonic signal.

[0089] As can be seen, in this embodiment, the photoelectric self-excited oscillation loop in the ultrasonic testing system converts the wavelength shift in the optical domain into the modulation characteristics of the microwave signal in the electrical domain, thus converting the wavelength shift in the optical domain into the modulation amount of the microwave signal in the electrical domain. That is, when the ultrasonic signal acts on the phase-shifting fiber grating, it causes a shift in its phase shift peak, thereby changing the frequency of the filtered sidebands, and thus modulating the output spectrum of the photoelectric self-excited oscillation loop. This, in turn, enables high-precision and high-stability demodulation and quantitative detection of the ultrasonic signal through a down-conversion module and a high-speed data acquisition module. The technical solution of this application not only breaks through the limitations of traditional measurement ranges but also has advantages such as resistance to environmental temperature interference. It effectively solves the Q-point stability problem in the sideband filtering method and the compatibility problem of the three-wavelength method with the grating spectrum, thereby achieving high-stability, high-resolution, and high-speed ultrasonic testing.

[0090] Figure 6 A schematic diagram of the structure of a terminal provided in an embodiment of this application. The terminal may include:

[0091] The memory 501, the processor 502, and the computer program stored on the memory 501 and capable of running on the processor 502.

[0092] When the processor 502 executes the program, it implements the ultrasonic testing method based on a photoelectric oscillator provided in the above embodiments.

[0093] Furthermore, the terminal also includes:

[0094] Communication interface 503 is used for communication between memory 501 and processor 502.

[0095] The memory 501 is used to store computer programs that can run on the processor 502.

[0096] Memory 501 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0097] If the memory 501, processor 502, and communication interface 503 are implemented independently, they can be interconnected via a bus to communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. Buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, only one line is used in the diagram, but this does not imply that there is only one bus or one type of bus.

[0098] Optionally, in a specific implementation, if the memory 501, processor 502, and communication interface 503 are integrated on a single chip, then the memory 501, processor 502, and communication interface 503 can communicate with each other through an internal interface.

[0099] Processor 502 may be a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application.

[0100] This embodiment also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described phase-shift fiber Bragg grating ultrasonic detection method based on an optoelectronic oscillator.

[0101] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0102] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0103] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus or device (such as a computer-based system, a processor-included system or other system that can read and execute instructions from and from an instruction execution system, apparatus or device).

[0104] It should be understood that the various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, the N steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. If implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0105] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A photonic-oscillator-based phase-shifted fiber grating ultrasonic detection system, characterized in that, The phase-shifted fiber grating ultrasonic detection system comprises a laser, a polarization controller, an optoelectronic self-oscillation loop, a phase-shifted fiber grating, a down-conversion module and a high-speed data acquisition module; The laser is used for generating a single-wavelength laser signal and outputting the single-wavelength laser signal to the polarization controller; The polarization controller is used for adjusting a polarization state of the single-wavelength laser signal to match optimal working conditions of a phase modulator in the optoelectronic self-oscillation loop and outputting the single-wavelength laser signal to the optoelectronic self-oscillation loop; The phase-shifted fiber grating connected with one end of an optical circulator in the optoelectronic self-oscillation loop is used for sensing an ultrasonic signal; The optoelectronic self-oscillation loop is used for splitting and outputting two target microwave signals when the phase-shifted fiber grating is subjected to a peak shift of a phase shift caused by an externally applied ultrasonic signal; one target microwave signal is output to the phase modulator to maintain the oscillation condition of the optoelectronic self-oscillation loop, and the other target microwave signal is output to the down-conversion module; The down-conversion module is used for receiving the other target microwave signal output by the optoelectronic self-oscillation loop, mixing the other target microwave signal with a local signal to obtain a mixed microwave signal, and outputting the mixed microwave signal; The high-speed data acquisition module is used for collecting and digitizing the mixed microwave signal output by the down-conversion module in real time to obtain a digital signal, performing fast Fourier transform on the digital signal to determine a change feature of a frequency domain sideband intensity, demodulating the digital signal based on the change feature of the frequency domain sideband intensity, extracting corresponding amplitude information and phase information, and obtaining a demodulation result and a detection result of the ultrasonic signal.

2. The optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection system of claim 1, wherein, The optoelectronic self-oscillation loop comprises a phase modulator, an optical circulator, an optical amplifier, an optical detector, a microwave power amplifier and a microwave power splitter; The phase modulator is used for phase-modulating the single-wavelength laser signal after the polarization controller and outputting the modulated laser signal to the optical circulator; The optical circulator is used for outputting the modulated laser signal input by the phase modulator to the phase-shifted fiber grating and receiving the laser signal after the phase-shifted fiber grating; The optical amplifier is used for amplifying the laser signal after the phase-shifted fiber grating output by the optical circulator; The optical detector is used for converting the amplified laser signal output by the optical amplifier into an electrical signal to obtain a corresponding microwave signal; The microwave power amplifier is used for amplifying the microwave signal output by the optical detector and transmitting the amplified microwave signal to the microwave power splitter; The microwave power splitter is used for splitting the amplified microwave signal output by the microwave power amplifier, outputting one target microwave signal to the phase modulator, and outputting the other target microwave signal to the down-conversion module.

3. The optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection system of claim 2, wherein, The phase-shifted fiber grating is also used for filtering a preset modulation frequency in the modulated laser signal input by the optical circulator.

4. The optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection system of claim 1, wherein, The laser is a wavelength-tunable narrow-line-width laser.

5. The optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection system of claim 1, wherein, The phase-shifted fiber grating is a π phase-shifted fiber grating.

6. The optoelectronic oscillator based phase-shifted fiber grating ultrasonic detection system of claim 2, wherein, The optical detector is specifically used for controlling the amplified laser signal output by the optical amplifier to beat with the single-wavelength laser signal to obtain a microwave signal.

7. The optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection system of claim 1, wherein, When the phase-shifted fiber grating is subjected to an externally applied ultrasonic signal, the ultrasonic signal produces a dynamic stress on the phase-shifted fiber grating, the phase shift peak of the phase-shifted fiber grating is shifted, and the relationship between the center wavelength of the phase-shifted fiber grating phase shift peak and the dynamic stress is: ； wherein, is the effective photoelastic coefficient, is the dynamic stress, is the center wavelength of the phase-shifted fiber grating when unstressed.

8. A phase-shifted fiber grating ultrasonic detection method based on an optoelectronic oscillator, characterized in that, The method comprises: When the phase-shifted fiber grating in the optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection system according to any one of claims 1 to 7 is subjected to an externally applied ultrasonic signal to cause the phase shift peak to shift, the down-conversion module in the ultrasonic detection system receives another target microwave signal output by the optoelectronic self-oscillation loop, and mixes the other target microwave signal with the local signal to obtain a mixed microwave signal; The mixed microwave signal output by the down-conversion module is collected and digitized in real time by the high-speed data acquisition module to obtain a digital signal; The digital signal is obtained, and the digital signal is subjected to fast Fourier transform processing to determine the change characteristics of the frequency domain sideband intensity; Based on the change characteristics of the frequency domain sideband intensity, the digital signal is demodulated to extract the corresponding amplitude information and phase information, and the demodulation result and detection result of the ultrasonic signal are obtained.

9. A terminal, characterized by comprising: Comprise: A memory, a processor, and an optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection program stored on the memory and executable on the processor, the optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection program being executed by the processor to implement the steps of the optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection method according to claim 8.

10. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program which can be executed to implement the steps of the optoelectronic oscillator-based phase-shifted fiber grating ultrasonic detection method according to claim 8.

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