CN111157101A - Weak grating array distributed vibration sensing system and method - Google Patents
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Abstract
The invention discloses a weak grating array distributed vibration sensing system and a method, belongs to the technical field of fiber grating sensing, and solves the problems that demodulation by using a double-arm interferometer in the prior art is easily interfered by an external environment, bottom noise is large, and frequency response bandwidth is narrow. A weak grating array distributed vibration sensing system comprises a narrow linewidth laser used for generating continuous light with a certain central wavelength; the acousto-optic modulator is used for modulating the continuous light into a corresponding double-pulse signal; the circulator is used for transmitting the double-pulse signal to the weak grating array; the weak grating array reflects the double-pulse signal to a circulator; the circulator is also used for transmitting the reflected double-pulse signal to the 3 x 3 coupler; the 3 x 3 coupler is used for enabling the reflected double-pulse signals to form interference and generating interference signals; and the photoelectric detector is used for acquiring the interference signal and converting the interference signal into an electric signal. The system bottom noise is reduced, and the signal-to-noise ratio and the frequency response range are improved.
Description
Technical Field
The invention relates to the technical field of fiber grating sensing, in particular to a weak grating array distributed vibration sensing system and a method.
Background
A signal acquisition and demodulation end of the distributed weak grating vibration sensing demodulation system; according to the vibration sensing mechanism of the fiber grating, a vibration signal is essentially modulated into an interference signal, and the demodulation of the vibration signal is actually phase demodulation; at present, the commonly used phase demodulation methods of the distributed sensing system include an orthogonal (IQ) demodulation algorithm, a phase carrier generation (PGC) detection method, and a 3 × 3 coupler demodulation algorithm;
for signal demodulation of a distributed weak grating vibration sensing demodulation system, the conventional interferometers are a Mach-Zehnder interferometer, a Sagnac interferometer and a Michelson interferometer; the pulse light is reflected by the continuous weak gratings and finally reaches the interferometer, and interferes in the coupler after passing through the two interference arms with unequal lengths, so that the reflected light of the adjacent weak gratings generates an interference phenomenon; the interferometer with sensitive double arms is easily interfered by external environment, such as case temperature, fan, external noise, vibration and the like, so that bottom noise of signal demodulation is very large, and the signal-to-noise ratio of the system is influenced. In addition, most of the existing vibration sensing systems have narrow bandwidth for frequency response and great difficulty for low-frequency response.
Disclosure of Invention
The invention aims to overcome at least one technical defect and provides a weak grating array distributed vibration sensing system and a weak grating array distributed vibration sensing method.
On one hand, the invention provides a distributed vibration sensing system of a weak grating array, which comprises a narrow line width laser, an acousto-optic modulator, a circulator, a weak grating array, a 3 multiplied by 3 coupler and a photoelectric detector;
the narrow linewidth laser is used for generating continuous light with a certain central wavelength and sending the continuous light to the acousto-optic modulator; the acousto-optic modulator is used for modulating the continuous light into a corresponding double-pulse signal and transmitting the double-pulse signal to the circulator; the circulator is used for receiving the double-pulse signal and transmitting the double-pulse signal to the weak grating array, and the weak grating array reflects the double-pulse signal to the circulator; the circulator is also used for transmitting the reflected double-pulse signal to the 3 x 3 coupler; the 3 × 3 coupler is used for enabling the reflected double-pulse signals to form interference and generating interference signals; and the photoelectric detector is used for acquiring the interference signal and converting the interference signal into an electric signal.
Furthermore, the weak grating array distributed vibration sensing system further comprises a data acquisition and FPGA processing unit, wherein the data acquisition and FPGA processing unit is used for generating electric pulses so that the acousto-optic modulator modulates the continuous light into corresponding double-pulse signals; the data acquisition and FPGA processing unit is also used for acquiring and demodulating the electric signals to form demodulated signals.
Further, the weak grating array distributed vibration sensing system further comprises an erbium-doped fiber amplifier, wherein the erbium-doped fiber amplifier is used for amplifying the double-pulse signal; the acousto-optic modulator transmits the double-pulse signal to the circulator, and concretely comprises the steps that the acousto-optic modulator transmits the double-pulse signal to an erbium-doped fiber amplifier, and the double-pulse signal is amplified by the erbium-doped fiber amplifier and then transmitted to the circulator.
Further, the acousto-optic modulator modulates the continuous light into a corresponding double-pulse signal, specifically including that the acousto-optic modulator modulates the continuous light into two rising edges with a time delay of TpsPulse width of TwA pulse repetition frequency of FpThe double-pulse signal of (2) is,
wherein,
Fpv is less than or equal to v/2L, v is the propagation speed of light in the weak grating array, d is the grating distance of the weak grating array, neIs the refractive index of the weak grating array, L is the length of the weak grating array, and c is the speed of light.
Further, the 3 × 3 coupler enables reflected double-pulse signals to form interference, when t is 0, the double-pulse signals are input into the sensing optical fiber, and the ith and i +1 grating reflected signals form interference signals with interference intensity i (t);
wherein E isi,Ri,τiThe amplitude, reflectivity and time of the ith grating are respectively; phi (t) is the phase difference between the i +1 th and i-th gratings, sigma polarization mismatch factor.
Further, the weak grating array distributed vibration sensing system further comprises interference signals with interference intensity I (t) formed by the ith and i +1 grating reflection signals, and currents of the three detectors are obtained
And using a standard arctangent algorithm, the voltage of the electrical signal can be obtained,
wherein D is a DC component, phi0Is the initial phase difference of adjacent weak grating arrays, and delta phi is the phase difference caused by the external environment.
On the other hand, the invention also provides a weak grating array distributed vibration sensing method, which comprises the following steps:
modulating continuous light with a certain central wavelength into a corresponding double-pulse signal, and transmitting the double-pulse signal to a weak grating array; the weak grating array reflects the double-pulse signals to enable the reflected double-pulse signals to form interference and generate interference signals; and acquiring the interference signal and converting the interference signal into an electric signal.
Further, the weak grating array distributed vibration sensing method further comprises the steps of collecting and demodulating the electric signals; and obtaining the phase change between two adjacent gratings by using an arc tangent algorithm on the demodulated signal.
Further, the weak grating array distributed vibration sensing method further comprises amplifying the double-pulse signal before transmitting the double-pulse signal to the weak grating array.
Further, modulating the continuous light into a corresponding double pulse signal specifically includes modulating the continuous light into a time delay of TpsPulse width of TwA pulse repetition frequency of FpThe double-pulse signal of (2) is,
wherein,
Fpv is less than or equal to v/2L, v is the propagation speed of light in the weak grating array, d is the grating distance of the weak grating array, neIs the refractive index of the weak grating array, L is the length of the weak grating array, and c is the speed of light.
Compared with the prior art, the invention has the beneficial effects that: generating continuous light with a certain central wavelength by the narrow linewidth laser and sending the continuous light to the acousto-optic modulator; the acousto-optic modulator modulates the continuous light into a corresponding double-pulse signal and transmits the double-pulse signal to the circulator; the circulator receives the double-pulse signal and transmits the double-pulse signal to the weak grating array, and the weak grating array reflects the double-pulse signal to the circulator; the circulator transmits the reflected double-pulse signal to the 3 x 3 coupler; the 3 x 3 coupler enables the reflected double-pulse signals to form interference to generate interference signals; the photoelectric detector acquires the interference signal and converts the interference signal into an electric signal; the phase difference between adjacent gratings is demodulated without using a conventional double-arm interferometer, so that the system is not interfered by the external environment, the stability of the system is improved, the bottom noise of the system is reduced, and the signal-to-noise ratio and the frequency response range are improved.
Drawings
Fig. 1 is a schematic structural diagram of a weak grating array distributed vibration sensing system according to embodiment 1 of the present invention;
fig. 2 is a schematic diagram of the working principle of the weak grating array distributed vibration sensing system according to embodiment 1 of the present invention;
FIG. 3(a) is a diagram of a Michelson-based structure under applied perturbation according to example 1 of the present invention
A demodulated signal spectrogram of the sensing system;
FIG. 3(b) is a diagram of a Michelson-based structure under applied perturbation according to example 1 of the present invention
A demodulated signal waveform of the sensing system;
FIGS. 4(a) and (b) are frequency domain and time domain signal diagrams of the demodulated electrical signal according to embodiment 1 of the present invention;
FIG. 5 is a graph of the frequency response for demodulating 40kHz and 0.1Hz as described in example 1 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further 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.
Example 1
The embodiment of the invention provides a weak grating array distributed vibration sensing system, which has a schematic structural diagram, as shown in fig. 1, and comprises a narrow linewidth laser, an acousto-optic modulator, a circulator, a weak grating array, a 3 x 3 coupler and a photoelectric detector;
the narrow linewidth laser is used for generating continuous light with a certain central wavelength and sending the continuous light to the acousto-optic modulator; the acousto-optic modulator is used for modulating the continuous light into a corresponding double-pulse signal and transmitting the double-pulse signal to the circulator; the circulator is used for receiving the double-pulse signal and transmitting the double-pulse signal to the weak grating array, and the weak grating array reflects the double-pulse signal to the circulator; the circulator is also used for transmitting the reflected double-pulse signal to the 3 x 3 coupler; the 3 × 3 coupler is used for enabling the reflected double-pulse signals to form interference and generating interference signals; and the photoelectric detector is used for acquiring the interference signal and converting the interference signal into an electric signal.
It should be noted that the optical fiber used in the embodiment of the present invention is a weak grating array with identical low reflectivity, the grating is a chirped grating, the 3dB bandwidth exceeds 3nm, the reflectivity is-50 dB, and the grating array interval is 3m or 5 m;
preferably, the weak grating array distributed vibration sensing system further comprises a data acquisition and FPGA processing unit, wherein the data acquisition and FPGA processing unit is used for generating electric pulses so that the acousto-optic modulator modulates the continuous light into corresponding double-pulse signals; the data acquisition and FPGA processing unit is also used for acquiring and demodulating the electric signals to form demodulated signals.
Preferably, the weak grating array distributed vibration sensing system further comprises an erbium-doped fiber amplifier, wherein the erbium-doped fiber amplifier is used for amplifying the double-pulse signal; the acousto-optic modulator transmits the double-pulse signal to the circulator, and concretely comprises the steps that the acousto-optic modulator transmits the double-pulse signal to an erbium-doped fiber amplifier, and the double-pulse signal is amplified by the erbium-doped fiber amplifier and then transmitted to the circulator.
In a specific embodiment, the weak grating array distributed vibration sensing system is schematically illustrated in the working principle, as shown in fig. 2; the narrow linewidth DFB laser generates continuous light with a certain central wavelength (such as 1550.15nm), a data acquisition and FPGA processing unit (which can use a data acquisition card to carry out data acquisition) write-in control is carried out by an upper computer, the data acquisition and FPGA processing unit generates corresponding electric pulses according to a compiled program, the corresponding electric pulses are used for modulating an AOM acoustic optical modulator, the AOM acoustic optical modulator modulates a continuous laser light source (continuous light) into corresponding double pulse light (signals), the double pulse light (signals) enters from a port 1 of a circulator after being amplified by an EDFA (erbium-doped fiber amplifier), then enters into a weak grating fiber array connected with a port 2 in series, the double pulse light is reflected back by the continuous weak grating, and then enters into a 3 x 3 coupler after exiting from a port 3 of the circulator, due to pulse delay, the optical path of the reflected light of the m-th weak grating is the same as the optical path of the reflected light of the m + 1-th weak grating reflected light of the front pulse, so that the reflected light of the adjacent weak gratings generates an interference phenomenon, namely the reflected light of the adjacent weak gratings can form interference in the 3 × 3 coupler; a series of reflected light pulses produces a series of interference pulse signals; if vibration is generated between two adjacent gratings, the transmission optical path difference of light between the two gratings is changed, so that the phase is changed, and the interference intensity is changed; the interference signal (interference pulse signal) is converted into an electric signal by 3 PD photoelectric detectors; the electric signals are collected and demodulated through a data collection and FPGA processing unit, and finally the signals are transmitted to an upper computer through PCIe for display and storage processing; the upper computer PC is mainly used for man-machine interaction; and meanwhile, the upper computer is also responsible for controlling basic setting of FPGA acquisition.
In specific implementation, the central wavelength, the output optical power and the 3dB line width of continuous light of the narrow-line-width laser are 1550.15nm, 30mw and 3kHz respectively; the double pulses comprise two light pulses, namely a front pulse and a rear pulse; the pulse width of a single pulse of the double-pulse signal is TwThe pulse delay of the rear pulse relative to the front pulse is Tps，
Preferably, the acousto-optic modulator modulates the continuous light into a corresponding double-pulse signal, specifically including that the acousto-optic modulator modulates the continuous light into two rising edges with a time delay TpsPulse width of TwA pulse repetition frequency of FpThe double-pulse signal of (2) is,
wherein,
Fpv is less than or equal to v/2L, v is the propagation speed of light in the weak grating array, d is the grating distance of the weak grating array, neIs the refractive index of the weak grating array, L is the length of the weak grating array, and c is the speed of light.
In the specific implementation, the light intensity of the rear pulse after being reflected by the ith grating and before reaching the 3X 3 coupler is assumed to be,
wherein E is0,Rm,ω,ne,k,Lm,τmThe light intensity amplitude of incident light, the reflectivity of the mth grating, the light frequency, the refractive index and the wave number of optical fibers, the optical fiber distance of the ith grating and the transmission time of reflected light to the coupler are respectively;
the front pulse is transmitted, passes through the (i + 1) th grating and is reflected to reach the 3 multiplied by 3 coupler, the front light intensity is,
Ei(t) and Ei+1(t) arrive at the coupler at exactly the same time, thereby causing interference in the PD, so that the interference signal has an interference intensity of
In the above formula, the first two terms are both direct current terms, the cosine function in the third term changes with time, the phase is phi (t), and the phase is phi (t) when no external disturbance exists0(t) the externally induced phase change of the optical fiber is phi1(t), so that phi (t) is phi1(t)+φ0(t), and therefore the above formula can be written as,
I(t)∝D+I0cos[φ(t)]
thus, since the 3 x 3 coupler outputs 120 out of phase, after passing through the coupler and three PDs, the intensity is,
three paths of signals in the coupler are collected through a photoelectric detector, and arc tangent algorithm demodulation is carried out through a data collection and FPGA processing unit, so that the relation between signal voltage V and phase change can be obtained:
wherein D is a DC component, phi0The initial phase difference of adjacent weak grating arrays is obtained, delta phi is the phase difference caused by the external environment, and the phase change of the adjacent weak grating arrays can be linearly obtained through the voltage value, so that distributed phase change demodulation is realized; from the above formula, it can be known that the signal voltage V has a linear relationship with the phase change, the phase change between adjacent gratings can be obtained by measuring the voltage value, and the fully distributed vibration monitoring is realized by arranging the gratings in a row.
In one specific implementation, the pulse period of the double-pulse signal is 90ns, the pulse width of the double-pulse signal is 40ns, the interval between two pulses is 10ns, the emission interval of the two double-pulse light is 100us, and the photodetector is an Avalanche Photodiode (APD);
preferably, the 3 × 3 coupler causes the reflected double-pulse signals to interfere with each other to generate an interference signal, specifically, the 3 × 3 coupler causes the reflected double-pulse signals to interfere with each other, when t is 0, the double-pulse signals are input to a sensing fiber (weak grating array), and the i-th and i + 1-th grating reflection signals form an interference signal with interference intensity i (t);
wherein E is0,Rm,ω,ne,k0,Lm,τmThe light intensity amplitude of the incident light, the reflectivity of the mth grating, the light frequency, the refractive index of the optical fiber, the wave number, the optical fiber distance of the mth grating and the transmission time of the reflected light to the coupler are respectively.
Preferably, the weak grating array distributed vibration sensing system further includes an interference signal with interference intensity i (t) formed by the ith and i +1 grating reflection signals, and the interference signal acquires currents of the three detectors
And using a standard arctangent algorithm, the voltage of the electrical signal can be obtained,
wherein D is a DC component, phi0Is the initial phase difference of adjacent weak grating arrays, and delta phi is the phase difference caused by the external environment. From the above formula, it can be known that the signal voltage V has a linear relationship with the phase change, the phase change between adjacent gratings can be obtained by measuring the voltage value, and the fully distributed vibration monitoring is realized by arranging the gratings in a row.
In the technical scheme of the embodiment of the invention, a double-arm interference structure does not exist in the optical path, so that the optical path in the system is not interfered by the external environment; based on the Michelson structure
For example, the sensing system is based on Michelson structure
300Hz disturbance and 20Hz sensing signals are applied to the light paths of the sensing system and the system;
FIG. 3(a) is based on a Michelson structure under applied perturbation
A demodulated signal spectrogram of the sensing system; the frequency signal of the phase signal is demodulated by single pulse modulation in a 3 multiplied by 3 coupler mode based on a Michelson double-arm structure under the condition of applying disturbance, and a spectrogram is displayed to have two peaks at 20Hz and 300 Hz; FIG. 3(b) is based on a Michelson structure under applied perturbation
The waveform diagram of the demodulated signal of the sensing system, namely the corresponding time domain signal of fig. 3 (a); FIG. 3(b) showsThe waveform diagram of the modulating signal has a plurality of burrs, and obviously the sensing signal is influenced by the external environment and has obvious noise, so that the signal-to-noise ratio of the system is influenced; FIGS. 4(a) and (b) are frequency domain and time domain signal diagrams of the electrical signal obtained by the technical solution of the present invention after demodulation, respectively; fig. 4(a) and fig. 4(b) show that there is no disturbing signal in the demodulated signal, and the burr in the demodulated signal is not obvious, so the system of the present invention can avoid the interference of vibration to the optical path, improve the stability and reliability of the system, and the signal-to-noise ratio of the system is also obviously improved; FIG. 5 is a frequency response diagram of the system of the present invention demodulating 40kHz and 0.1Hz (the left graph corresponds to 40kHz frequency response, the right graph corresponds to 0.1Hz frequency response), the sensor of the system of the present invention can realize 0.1 Hz-40 kHz frequency response by applying a vibration signal through PZT, and the signal-to-noise ratio of the system can reach 42 dB. It can be seen that the system has a wide frequency response range, which is only limited by the length of the optical fiber and the sampling rate of the acquisition card.
Example 2
The invention also provides a weak grating array distributed vibration sensing method, which comprises the following steps:
modulating continuous light with a certain central wavelength into a corresponding double-pulse signal, and transmitting the double-pulse signal to a weak grating array; the weak grating array reflects the double-pulse signals to enable the reflected double-pulse signals to form interference and generate interference signals; and acquiring the interference signal and converting the interference signal into an electric signal.
Preferably, the weak grating array distributed vibration sensing method further includes collecting and demodulating the electrical signal to form a demodulated signal; and obtaining the phase change between two adjacent gratings by using an arc tangent algorithm on the demodulated signal.
Preferably, the weak grating array distributed vibration sensing method further includes amplifying the double pulse signal before transmitting the double pulse signal to the weak grating array.
Preferably, modulating the continuous light into the corresponding double-pulse signal specifically includes modulating the continuous light into a time delay of TpsPulse ofPulse width of TwA pulse repetition frequency of FpThe double-pulse signal of (2) is,
wherein,
Fpv is less than or equal to v/2L, v is the propagation speed of light in the weak grating array, d is the grating distance of the weak grating array, neIs the refractive index of the weak grating array, L is the length of the weak grating array, and c is the speed of light.
Preferably, the interfering the reflected double-pulse signals to generate interference signals includes interfering the reflected double-pulse signals, where the interference intensity is i (t) is interference signals,
wherein E isi,Ri,τiRespectively the amplitude, reflectivity and time of the ith grating; phi (t) is the phase difference between the i +1 th and i-th gratings, sigma polarization mismatch factor.
It should be noted that the description of example 1 and example 2 is not repeated, and they can be referred to each other.
The invention discloses a weak grating array distributed vibration sensing system and a method, wherein continuous light with a certain central wavelength is generated by a narrow linewidth laser and is sent to an acousto-optic modulator; the acousto-optic modulator modulates the continuous light into a corresponding double-pulse signal and transmits the double-pulse signal to the circulator; the circulator receives the double-pulse signal and transmits the double-pulse signal to the weak grating array, and the weak grating array reflects the double-pulse signal to the circulator; the circulator transmits the reflected double-pulse signal to the 3 x 3 coupler; the 3 x 3 coupler enables the reflected double-pulse signals to form interference to generate interference signals; the photoelectric detector acquires the interference signal and converts the interference signal into an electric signal; the phase difference between adjacent gratings is demodulated without using a conventional double-arm interferometer, so that the system is not interfered by the external environment, the stability of the system is improved, the bottom noise of the system is reduced, and the signal-to-noise ratio and the frequency response range are improved;
it should be noted that, in order to reduce the complexity of the phase demodulation algorithm and improve the demodulation precision of the signal and the signal-to-noise ratio of the demodulated signal, the inverse tangent demodulation algorithm is adopted in the invention during demodulation, compared with other demodulation algorithms, the integral operation is replaced by the operation of positive and negative tangent, and the noise self-excitation influence generated by the integral operation is avoided; the technical scheme of the invention does not need double-arm interference, uses direct detection, ensures that demodulation is not interfered by external environment, reduces the bottom noise of the system, improves the signal-to-noise ratio of the system, has an ultra-wide frequency response range, is only limited by the length of an optical fiber, has the lowest response frequency of 0.1Hz, has a simple system structure, reduces the complexity of the system because all components are conventional devices, greatly reduces the system cost, and is more suitable for engineering application.
The above-described embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A distributed vibration sensing system of a weak grating array is characterized by comprising a narrow line width laser, an acousto-optic modulator, a circulator, a weak grating array, a 3 x 3 coupler and a photoelectric detector;
the narrow linewidth laser is used for generating continuous light with a certain central wavelength and sending the continuous light to the acousto-optic modulator; the acousto-optic modulator is used for modulating the continuous light into a corresponding double-pulse signal and transmitting the double-pulse signal to the circulator; the circulator is used for receiving the double-pulse signal and transmitting the double-pulse signal to the weak grating array, and the weak grating array reflects the double-pulse signal to the circulator; the circulator is also used for transmitting the reflected double-pulse signal to the 3 x 3 coupler; the 3 × 3 coupler is used for enabling the reflected double-pulse signals to form interference and generating interference signals; and the photoelectric detector is used for acquiring the interference signal and converting the interference signal into an electric signal.
2. The distributed vibration sensing system of claim 1, further comprising a data acquisition and FPGA processing unit for generating electrical pulses to cause the acousto-optic modulator to modulate said continuous light into a corresponding double pulse signal; the data acquisition and FPGA processing unit is also used for acquiring and demodulating the electric signals to form demodulated signals.
3. The distributed vibration sensing system of claim 1, further comprising an erbium doped fiber amplifier for amplifying the double pulse signal; the acousto-optic modulator transmits the double-pulse signal to the circulator, and concretely comprises the steps that the acousto-optic modulator transmits the double-pulse signal to an erbium-doped fiber amplifier, and the double-pulse signal is amplified by the erbium-doped fiber amplifier and then transmitted to the circulator.
4. The distributed vibration sensing system according to claim 1, wherein the acousto-optic modulator modulates the continuous light into a corresponding double pulse signal, specifically comprising the acousto-optic modulator modulating the continuous light into two leading and trailing rising edges with a time delay of TpsPulse width of TwA pulse repetition frequency of FpThe double-pulse signal of (2) is,
wherein,
Fpv is less than or equal to v/2L, v is the propagation speed of light in the weak grating array, d is the grating distance of the weak grating array, neIs the refractive index of the weak grating array, L is the length of the weak grating array, and c is the speed of light.
5. The distributed vibration sensing system of claim 4, wherein the 3 × 3 coupler causes the reflected double-pulse signals to form interference to generate interference signals, and specifically includes that the 3 × 3 coupler causes the reflected double-pulse signals to form interference, when t is 0, the double-pulse signals are input into the sensing fiber, and the i-th and i + 1-th grating reflection signals form interference signals with interference intensity i (t);
wherein E isi,Ri,τiRespectively the amplitude, reflectivity and time of the ith grating; phi (t) is the phase difference between the i +1 th and i-th gratings, sigma polarization mismatch factor.
6. The distributed vibration sensing system of claim 5, further comprising a means for obtaining the currents of three detectors according to the interference signal with interference intensity I (t) formed by the i and i +1 grating reflection signals
And using a standard arctangent algorithm, the voltage of the electrical signal can be obtained,
wherein D is a DC component, phi0Is the initial phase difference of adjacent weak grating arrays, and delta phi is the phase difference caused by the external environment.
7. A distributed vibration sensing method of a weak grating array is characterized by comprising the following steps:
modulating continuous light with a certain central wavelength into a corresponding double-pulse signal, and transmitting the double-pulse signal to a weak grating array; the weak grating array reflects the double-pulse signals to enable the reflected double-pulse signals to form interference and generate interference signals; and acquiring the interference signal and converting the interference signal into an electric signal.
8. The distributed vibration sensing method of a weak grating array according to claim 7, further comprising collecting and demodulating the electrical signal to form a demodulated signal; and obtaining the phase change between two adjacent gratings by using an arc tangent algorithm on the demodulated signal.
9. The weak grating array distributed vibration sensing method of claim 7, further comprising amplifying the dipulse signal prior to transmitting the dipulse signal to the weak grating array.
10. The distributed vibration sensing method of a weak grating array according to claim 7, wherein modulating the continuous light into a corresponding double pulse signal specifically comprises modulating the continuous light into a time delay of TpsPulse width of TwA pulse repetition frequency of FpThe double-pulse signal of (2) is,
wherein,
Fpv is less than or equal to v/2L, v is the propagation speed of light in the weak grating array, d is the grating distance of the weak grating array, neIs the refractive index of the weak grating array, L is the length of the weak grating array, and c is the speed of light.
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Cited By (12)
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| CN112032575A (en) * | 2020-08-10 | 2020-12-04 | 武汉理工大学 | Pipeline safety monitoring method and system based on weak grating and storage medium |
| CN112880711A (en) * | 2021-01-18 | 2021-06-01 | 合肥工业大学 | Distributed optical fiber sensing method and system based on double-pulse modulation |
| CN113219205A (en) * | 2021-03-24 | 2021-08-06 | 西北大学 | Fiber bragg grating distributed acceleration monitoring device and method |
| CN113310564A (en) * | 2021-05-08 | 2021-08-27 | 武汉理工大学 | System and method for measuring vibration parameter and temperature parameter of oil well casing |
| CN113483795A (en) * | 2021-06-18 | 2021-10-08 | 安徽龙联智能光电有限公司 | Weak grating array distributed vibration sensing demodulation method and system |
| CN113503956A (en) * | 2021-07-09 | 2021-10-15 | 中国人民解放军国防科技大学 | Device and method for simultaneously picking up self-vibration of underwater platform and external sound signals |
| CN113691309A (en) * | 2021-08-18 | 2021-11-23 | 中国电力科学研究院有限公司 | Method, system, equipment and medium for measuring half wavelength of standing wave of OPGW (optical fiber composite overhead ground wire) optical cable |
| CN114323251A (en) * | 2022-03-10 | 2022-04-12 | 武汉理工大学 | Signal equalization device and method for distributed optical fiber phase-sensitive optical time domain reflectometer |
| CN114608697A (en) * | 2022-03-22 | 2022-06-10 | 中国人民解放军国防科技大学 | Low-noise broadband distributed acoustic wave detection device and method based on FBG |
| CN114659612A (en) * | 2022-03-16 | 2022-06-24 | 武汉理工大学 | Rail transit train positioning system and method based on fiber bragg grating array |
| CN115388918A (en) * | 2022-08-10 | 2022-11-25 | 武汉理工大学 | Distributed temperature and vibration measurement system and method |
| CN117411546A (en) * | 2023-12-11 | 2024-01-16 | 南昌大学 | LED communication capability evaluation method and system |
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| CN112032575B (en) * | 2020-08-10 | 2022-04-19 | 武汉理工大学 | Pipeline safety monitoring method and system based on weak grating and storage medium |
| CN112032575A (en) * | 2020-08-10 | 2020-12-04 | 武汉理工大学 | Pipeline safety monitoring method and system based on weak grating and storage medium |
| CN112880711A (en) * | 2021-01-18 | 2021-06-01 | 合肥工业大学 | Distributed optical fiber sensing method and system based on double-pulse modulation |
| CN113219205A (en) * | 2021-03-24 | 2021-08-06 | 西北大学 | Fiber bragg grating distributed acceleration monitoring device and method |
| CN113310564A (en) * | 2021-05-08 | 2021-08-27 | 武汉理工大学 | System and method for measuring vibration parameter and temperature parameter of oil well casing |
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| CN113483795B (en) * | 2021-06-18 | 2024-05-14 | 安徽龙联智能光电有限公司 | Weak grating array distributed vibration sensing demodulation method and system |
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| CN114323251A (en) * | 2022-03-10 | 2022-04-12 | 武汉理工大学 | Signal equalization device and method for distributed optical fiber phase-sensitive optical time domain reflectometer |
| CN114323251B (en) * | 2022-03-10 | 2022-06-17 | 武汉理工大学 | Signal equalization device and method for distributed optical fiber phase-sensitive optical time domain reflectometer |
| CN114659612A (en) * | 2022-03-16 | 2022-06-24 | 武汉理工大学 | Rail transit train positioning system and method based on fiber bragg grating array |
| CN114659612B (en) * | 2022-03-16 | 2024-05-03 | 武汉理工大学 | Rail transit train positioning system and method based on fiber bragg grating array |
| CN114608697A (en) * | 2022-03-22 | 2022-06-10 | 中国人民解放军国防科技大学 | Low-noise broadband distributed acoustic wave detection device and method based on FBG |
| CN115388918A (en) * | 2022-08-10 | 2022-11-25 | 武汉理工大学 | Distributed temperature and vibration measurement system and method |
| CN117411546A (en) * | 2023-12-11 | 2024-01-16 | 南昌大学 | LED communication capability evaluation method and system |
| CN117411546B (en) * | 2023-12-11 | 2024-02-09 | 南昌大学 | LED communication capability evaluation method and system |
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