Three-component rotational earthquake monitoring device based on dual-polarization fiber optic angular accelerometer

Abstract

The present invention discloses a three-component rotation earthquake monitoring device based on a dual-polarization fiber angular accelerometer, which is characterized by comprising a first light source module, a second light source module, a data processing unit and three modulation and demodulation optical path systems; the output end of the first light source module is connected to a first coupler via a first polarizer, the first coupler divides linearly polarized light into three paths, and respectively inputs the three modulation and demodulation optical path systems; the output end of the second light source module is connected to a second coupler via a second polarizer, the second coupler divides linearly polarized light into three paths, and respectively inputs the three modulation and demodulation optical path systems; each modulation and demodulation optical path system comprises two optical paths and a polarization-maintaining optical fiber ring, each optical path comprises a circulator, a photodetector, a digital signal acquisition and processing unit, an optical modulator, and a polarization splitter / combiner; the polarization-maintaining optical fiber rings in the three systems are placed vertically in pairs; the data processing unit is used to calculate and obtain a three-component earthquake rotation component signal based on the signals corresponding to each system.

Description

Technical Field

[0001] The present invention relates to the field of rotation earthquake detection, in particular to a three-component rotation earthquake monitoring device based on a dual-polarization optical fiber angular accelerometer. Background Art

[0002] The characteristic signal of an earthquake's rotational component, which contains information about the directionality and anisotropy of the vibration, can more fully describe the earthquake source and its wavefield, becoming a key research topic in seismology in recent years. Angular accelerometers can be used to monitor the rotational component of the Earth's medium caused by earthquakes and, in turn, to demodulate the dynamic characteristic signals of the medium's rotation. This is key to breaking through bottlenecks in modern multidimensional seismological research, and therefore, the research on rotational earthquake monitoring devices based on angular accelerometers has important scientific value.

[0003] To date, most angular accelerometer research and development, both domestically and internationally, has focused on high-frequency vibration monitoring. Conventional electromechanical angular accelerometers struggle to scale to low frequencies, making them unsuitable for earthquake monitoring. Liquid ring-based angular accelerometers offer good low-frequency performance, but they suffer from low accuracy and limited environmental adaptability, making them unsuitable for earthquake monitoring. Microelectromechanical system (MEMS) angular accelerometers offer advantages such as small size, low price, and good low-frequency performance, but their lower measurement accuracy limits their application.

[0004] A dual-polarization fiber Sagnac interferometer can achieve highly sensitive angular acceleration detection, thereby creating a dual-polarization fiber angular accelerometer with high sensitivity, wide-band response, and strong environmental adaptability. This, in turn, enables the fabrication of a rotational earthquake detection device that meets these requirements. Compared to traditional earthquake detection devices, this invention not only boasts high sensitivity and wide bandwidth, but also utilizes three dual-polarization fiber angular accelerometers arranged orthogonally, enabling the detection of rotational signals in three-dimensional space. Summary of the Invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide a three-component rotation earthquake monitoring device based on a dual-polarization fiber optic angular accelerometer, which has the advantages of high sensitivity, wide-band response and strong environmental adaptability.

[0006] The technical solution of the present invention is:

[0007] A three-component rotation earthquake monitoring device based on a dual-polarization fiber optic angular accelerometer is characterized by comprising a first light source module 1, a second light source module 4, a data processing unit and three modulation and demodulation optical path systems;

[0008] The output end of the first light source module 1 is connected to the first coupler 3 via the first polarizer 2. The first polarizer 2 is used to convert the laser output by the first light source module 1 into a first polarized light and input it into the first coupler 3. The first coupler 3 is used to split the first polarized light into three paths, which are respectively input into the three modulation and demodulation optical path systems.

[0009] The output end of the second light source module 4 is connected to the second coupler 6 via the second polarizer 5. The second polarizer 5 is used to convert the laser output by the second light source module 4 into a second polarized light and input it into the second coupler 6. The second coupler 6 is used to split the second polarized light into three paths, which are respectively input into the three modulation and demodulation optical path systems.

[0010] Each of the modulation and demodulation optical path systems includes two optical paths and a polarization-maintaining fiber ring, wherein the first optical path includes a first circulator, a first photodetector, a first digital signal acquisition and processing unit, a first optical modulator, and a first polarization beam splitter / combiner; the second optical path includes a second circulator, a second photodetector, a second digital signal acquisition and processing unit, a second optical modulator, and a second polarization beam splitter / combiner;

[0011] The input end of the first optical modulator is connected to the second port of the first circulator, and is used to receive the first route polarized light and split it into two beams, one beam of polarized light is input to the first beam combining input end of the first polarization beam splitter / combiner, and the other beam of polarized light is input to the first beam combining input end of the second polarization beam splitter / combiner. The beam combining output end of the first polarization beam splitter / combiner is connected to one end of the polarization-maintaining fiber ring, and the two beams of polarized light enter the polarization-maintaining fiber ring through the X-Pol channels of the first polarization beam splitter / combiner and the second polarization beam splitter / combiner respectively. The third port of the first circulator is connected to the first digital signal acquisition and processing unit via the first photodetector. The third port of the first circulator is used to receive the interference signal returned by the first optical modulator. The first photodetector is used to convert the received interference signal into an electrical signal and then input it into the first digital signal acquisition and processing unit. The first digital signal acquisition and processing unit is connected to the data processing unit, and is used to input the collected signal into the data processing unit.

[0012] The input end of the second optical modulator is connected to the second port of the second circulator, and is used to receive the second route polarized light and split it into two beams, one beam of polarized light is input to the second beam combining input end of the first polarization beam splitter / combiner, and the other beam of polarized light is input to the second beam combining input end of the second polarization beam splitter / combiner. The beam combining output end of the second polarization beam splitter / combiner is connected to the other end of the polarization-maintaining fiber ring, and the two beams of polarized light enter the polarization-maintaining fiber ring through the Y-Pol channels of the first polarization beam splitter / combiner and the second polarization beam splitter / combiner respectively; the third port of the second circulator is connected to the second digital signal acquisition and processing unit via the second photodetector, and the third port of the second circulator is used to receive the interference signal returned by the second optical modulator, and the second photodetector is used to convert the received interference signal into an electrical signal and then input it into the second digital signal acquisition and processing unit; the second digital signal acquisition and processing unit is connected to the data processing unit, and is used to input the collected signal into the data processing unit;

[0013] The polarization-maintaining optical fiber rings in the modulation and demodulation optical path system are placed vertically in pairs;

[0014] The data processing unit is used to calculate and obtain three-component seismic rotation component signals based on the signals corresponding to the modulation and demodulation optical path systems.

[0015] Furthermore, the data processing unit calculates two angular velocity values Ω1(t) and Ω2(t) based on the two signals corresponding to each of the modulation and demodulation optical path systems; then calculates a single-component angular acceleration value α(t) based on the angular velocity values Ω1(t) and Ω2(t); and then calculates one component signal of the three-component seismic rotation component signal based on the angular acceleration value α(t).

[0016] Furthermore, the angular acceleration value Wherein, Ω1(ω) is the frequency domain signal of Ω1(t), Ω2(ω) is the frequency domain signal of Ω2(t), and τ is the set delay.

[0017] Furthermore, the polarization-maintaining fiber rings in the three modulation and demodulation optical path systems are respectively arranged on three orthogonal side surfaces of a cubic structure 44 .

[0018] Furthermore, the data processing unit includes a first ARM processor 40, a second ARM processor 41, a third ARM processor 42 and a fourth ARM processor 43; the first ARM processor 40 is used to calculate an angular acceleration value based on the two signals corresponding to the first modulation and demodulation optical path system and send it to the fourth ARM processor 43; the second ARM processor 41 is used to calculate an angular acceleration value based on the two signals corresponding to the second modulation and demodulation optical path system and send it to the fourth ARM processor 43; the third ARM processor 42 is used to calculate an angular acceleration value based on the two signals corresponding to the third modulation and demodulation optical path system and send it to the fourth ARM processor 43; the fourth ARM processor 43 calculates a three-component seismic rotation component signal based on the three angular acceleration values.

[0019] The advantages of the present invention are as follows:

[0020] The present invention uses three orthogonally distributed dual-polarization angular accelerometers to form a three-component rotational earthquake monitoring device to detect rotational earthquake signals in three dimensions. The implementation of the present invention will provide a theoretical basis and technical support for the development of new-sensitivity rotational seismometers, promote their application in the field of earthquake monitoring, and have huge social application value and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Optical path diagram of the three-component fiber optic angular acceleration sensing system based on dual light sources.

[0022] Figure 2 This is the signal processing diagram of the three-component earthquake rotation component.

[0023] Figure 3 This is the structural diagram of the three-component rotational seismic measurement device.

[0024] Reference numerals: 1-first light source module, 2-first polarizer, 3-first coupler, 4-second light source module, 5-second polarizer, 6-second coupler, 7-first circulator, 8-first photodetector, 9-first digital signal acquisition and processing unit (DSP), 10-first optical modulator (MIOC), 11-first polarization beam splitter / combiner (PBS / C), 12-first polarization-maintaining fiber ring; 13-second circulator, 14-second photodetector, 15-second digital signal acquisition and processing unit, 16-second optical modulator, 17-second polarization beam splitter / combiner;

[0025] 18-third circulator, 19-third photodetector, 20-third digital signal acquisition and processing unit, 21-third optical modulator, 22-third polarization beam splitter / combiner, 23-second polarization-maintaining fiber ring, 24-fourth circulator, 25-fourth photodetector, 26-fourth digital signal acquisition and processing unit, 27-fourth optical modulator, 28-fourth polarization beam splitter / combiner;

[0026] 29-fifth circulator, 30-fifth photodetector, 31-fifth digital signal acquisition and processing unit, 32-fifth optical modulator, 33-fifth polarization beam splitter / combiner, 34-third polarization-maintaining fiber ring, 35-sixth circulator, 36-sixth photodetector, 37-sixth digital signal acquisition and processing unit, 38-sixth optical modulator, 39-sixth polarization beam splitter / combiner;

[0027] 40 - first ARM processor, 41 - second ARM processor, 42 - third ARM processor, 43 - fourth ARM processor, 44 - cube structure. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0029] The present invention relates to an angular acceleration measuring device based on an optical fiber Sagnac interferometer. Figure 1As shown, the system is three modulation and demodulation optical paths based on fiber Sagnac interferometers, including a first light source module 1 and a second light source module 4, a first polarizer 2 and a second polarizer 5, a first circulator 7 and a second circulator 13, a first photodetector 8 and a second photodetector 14, a first digital signal acquisition and processing unit 9 and a second digital signal acquisition and processing unit 15, a first optical modulator 10 and a second optical modulator 16, a first polarization splitter / combiner 11 and a second polarization splitter / combiner 17 and a polarization-maintaining fiber ring 12 (the names below are the same as here). The entire optical path system utilizes a polarization-maintaining fiber design, using three identical polarization-maintaining fiber loops to form three identical angular acceleration sensing systems. The specific operating principle is as follows: Light emitted by the light source module 1 is split into three paths, each entering the first optical path of the three angular acceleration sensing systems. Taking the first optical path of the first angular acceleration sensing system as an example, after passing through the first circulator 7, it enters the first optical modulator 10, which splits it into two beams and inputs the first polarization beam splitter / combiner 11 and the second polarization beam splitter / combiner 17. The beams then pass through the X-Pol channels of the first and second polarization beam splitters / combiners 11 and 17, entering the polarization-maintaining fiber loop 12 for sensing. The beams then return to the first and second polarization beam splitters / combiners 11 and 17 for interference interference, and finally pass through the first circulator 7 to enter the first photodetector 8. The first photodetector 8 converts the optical signal into an electrical signal, which is then amplified by an amplifier and processed by the first digital signal acquisition and processing unit 9. The other light emitted by the light source module 2 is also divided into three paths and enters the second path of the three angular acceleration sensor systems, and then enters the y-pol channel of the two PBS / Cs through the circulator and MIOC, and then the second signal can be collected by the same principle.

[0030] After collecting two optical signals, the phase shift φ caused by the angular motion of the fiber ring can be calculated. s (t), and then the angular velocity value Ω(t) can be restored:

[0031]

[0032] Where λ is the wavelength of the light wave, L is the length of the fiber loop, D is the area of the fiber loop, and c is the speed of light in a vacuum. Each angular acceleration sensing system can demodulate two angular velocities, Ω1(t) and Ω2(t). By performing a time-domain differential on the delay τ, the angular acceleration value can be calculated. The value of the delay τ can be determined based on the specific situation. Angular acceleration can be expressed as:

[0033]

[0034] Where α(t) is the angular acceleration and t is the time. Based on this principle, the demodulation of three-way angular acceleration is finally achieved.

[0035] Based on the three-way angular acceleration sensing system, the three-component earthquake rotation component signal monitoring is realized. The system consists of three independent signal sensing systems. Each system outputs a signal from a photoelectric detector, which is then processed by two DSPs and demodulated in the ARM processor to obtain two angular velocities. Then, after a delay, the first angular acceleration is obtained. Finally, the three-way angular acceleration signal is obtained, and then the three-way angular acceleration signal is processed by ARM43 to finally realize the monitoring of earthquake rotation signals in three-dimensional space. The data processing unit of the embodiment of the present invention is as follows: Figure 2 As shown, it includes a first ARM processor 40, a second ARM processor 41, a third ARM processor 42 and a fourth ARM processor 43; the first ARM processor 40 is used to calculate an angular acceleration value based on the two signals corresponding to the first modulation and demodulation optical path system and send it to the fourth ARM processor 43; the second ARM processor 41 is used to calculate an angular acceleration value based on the two signals corresponding to the second modulation and demodulation optical path system and send it to the fourth ARM processor 43; the third ARM processor 42 is used to calculate an angular acceleration value based on the two signals corresponding to the third modulation and demodulation optical path system and send it to the fourth ARM processor 43; the fourth ARM processor 43 calculates a three-component seismic rotation component signal based on the three angular acceleration values.

[0036] In the present invention, the sensing of angular acceleration is realized based on polarization-maintaining fiber rings. Each fiber ring can detect the rotation component of the plane in which the ring is located. Therefore, three polarization-maintaining fiber rings are placed vertically in pairs, such as Figure 3 As shown, the detection of angular acceleration in three-dimensional space can be realized. Then, the outer structure 44 is made and fixedly packaged to complete the final device.

[0037] While specific embodiments of the present invention have been disclosed for illustrative purposes, intended to facilitate understanding and implementation of the present invention, those skilled in the art will appreciate that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the disclosure of the preferred embodiments, and the scope of protection claimed in the present invention shall be determined by the scope of the claims.

Claims

1. A three-component rotational earthquake monitoring device based on a dual-polarization fiber optic angular accelerometer, characterized in that: It comprises a first light source module (1), a second light source module (4), a data processing unit and three modulation and demodulation optical path systems; The output end of the first light source module (1) is connected to the first coupler (3) via the first polarizer (2); the first polarizer (2) is used to convert the laser output by the first light source module (1) into a first-path polarized light and input it into the first coupler (3); the first coupler (3) is used to split the first-path polarized light into three paths, which are respectively input into the three modulation and demodulation optical path systems; The output end of the second light source module (4) is connected to the second coupler (6) via a second polarizer (5); the second polarizer (5) is used to convert the laser light output by the second light source module (4) into a second-path polarized light and input it into the second coupler (6); the second coupler (6) is used to split the second-path polarized light into three paths, which are respectively input into the three modulation and demodulation optical path systems; Each of the modulation and demodulation optical path systems includes two optical paths and a polarization-maintaining optical fiber ring, wherein the first optical path includes a first circulator, A first photodetector, a first digital signal acquisition and processing unit, a first optical modulator, and a first polarization beam splitter / combiner; a second optical path includes a second circulator, a second photodetector, a second digital signal acquisition and processing unit, a second optical modulator, and a second polarization beam splitter / combiner; The input end of the first optical modulator is connected to the second port of the first circulator, and is used to receive the first route polarized light and split it into two beams, one beam of polarized light is input to the first beam combining input end of the first polarization beam splitter / combiner, and the other beam of polarized light is input to the first beam combining input end of the second polarization beam splitter / combiner. The beam combining output end of the first polarization beam splitter / combiner is connected to one end of the polarization-maintaining fiber ring, and the two beams of polarized light enter the polarization-maintaining fiber ring through the X-Pol channels of the first polarization beam splitter / combiner and the second polarization beam splitter / combiner respectively. The third port of the first circulator is connected to the first digital signal acquisition and processing unit via the first photodetector. The third port of the first circulator is used to receive the interference signal returned by the first optical modulator. The first photodetector is used to convert the received interference signal into an electrical signal and then input it into the first digital signal acquisition and processing unit. The first digital signal acquisition and processing unit is connected to the data processing unit, and is used to input the collected signal into the data processing unit. The input end of the second optical modulator is connected to the second port of the second circulator, and is used to receive the second route polarized light and split it into two beams, one beam of polarized light is input to the second beam combining input end of the first polarization beam splitter / combiner, and the other beam of polarized light is input to the second beam combining input end of the second polarization beam splitter / combiner. The beam combining output end of the second polarization beam splitter / combiner is connected to the other end of the polarization-maintaining fiber ring, and the two beams of polarized light enter the polarization-maintaining fiber ring through the Y-Pol channels of the first polarization beam splitter / combiner and the second polarization beam splitter / combiner respectively; the third port of the second circulator is connected to the second digital signal acquisition and processing unit via the second photodetector, and the third port of the second circulator is used to receive the interference signal returned by the second optical modulator, and the second photodetector is used to convert the received interference signal into an electrical signal and then input it into the second digital signal acquisition and processing unit; the second digital signal acquisition and processing unit is connected to the data processing unit, and is used to input the collected signal into the data processing unit; The polarization-maintaining optical fiber rings in the three modulation and demodulation optical path systems are placed vertically in pairs; The data processing unit is used to calculate and obtain three-component seismic rotation component signals based on the signals corresponding to the modulation and demodulation optical path systems.

2. The three-component rotation earthquake monitoring device according to claim 1, characterized in that: The data processing unit calculates two angular velocity values Ω1(t) and Ω2(t) based on the two signals corresponding to each of the modulation and demodulation optical path systems; then calculates a single-component angular acceleration value α(t) based on the angular velocity values Ω1(t) and Ω2(t); then calculates one component signal of the three-component seismic rotation component signal based on the angular acceleration value α(t).

3. The three-component rotation earthquake monitoring device according to claim 2, characterized in that: The angular acceleration value Wherein, Ω1(ω) is the frequency domain signal of Ω1(t), Ω2(ω) is the frequency domain signal of Ω2(t), and τ is the set delay.

4. The three-component rotation earthquake monitoring device according to claim 1, 2 or 3, characterized in that: The polarization-maintaining optical fiber rings in the three modulation and demodulation optical path systems are respectively arranged on three orthogonal side surfaces of a cubic structure (44).

5. The three-component rotation earthquake monitoring device according to claim 1, 2 or 3, characterized in that: The data processing unit comprises a first ARM processor (40), a second ARM processor (41), a third ARM processor (42) and a fourth ARM processor (43); the first ARM processor (40) is used to calculate an angular acceleration value based on two signals corresponding to the first modulation and demodulation optical path system and send the value to the fourth ARM processor (43); the second ARM processor (41) is used to calculate an angular acceleration value based on two signals corresponding to the second modulation and demodulation optical path system and send the value to the fourth ARM processor (43); the third ARM processor (42) is used to calculate an angular acceleration value based on two signals corresponding to the third modulation and demodulation optical path system and send the value to the fourth ARM processor (43); the fourth ARM processor (43) calculates a three-component seismic rotation component signal based on the three angular acceleration values.

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