WO2023220919A1

WO2023220919A1 - Calibration method, system and apparatus for low-frequency performance test of all-fiber detector

Info

Publication number: WO2023220919A1
Application number: PCT/CN2022/093285
Authority: WO
Inventors: 常天英; 崔洪亮
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2022-05-17
Filing date: 2022-05-17
Publication date: 2023-11-23

Abstract

A calibration method for a low-frequency performance test of an all-fiber detector, comprising: attaching parallel plate capacitor structures (1) at two ends of a detection probe (2) and applying an alternating-current voltage signal, wherein the detection probe (2) is driven to vibrate up and down so that optical fibers on the detection probe (2) are deformed in an alternating-current form; acquiring a phase change amount of the optical fibers by means of a demodulation algorithm, and establishing a first relationship between the phase change amount and the alternating-current voltage signal on the basis of the frequency and amplitude of the alternating-current voltage signal; applying an alternating-current voltage signal having a frequency band below 0.1 Hz, and acquiring the frequency and amplitude of the detection probe (2) via conversion on the basis of the first relationship, so as calibrate a low-frequency performance test of an all-fiber detector. Also provided are a calibration system and apparatus for the low-frequency performance test of the all-fiber detector.

Description

A calibration method, system and device for low-frequency performance testing of all-fiber detectors

Technical field

The invention relates to the field of optical fiber sensing, and specifically to a calibration method, system and device for low-frequency performance testing of an all-fiber detector.

Background technique

Compared with electromechanical seismometers, fiber optic seismometers have the advantages of intrinsically passive probes, resistance to electromagnetic interference, and easy reusability in networking. They are suitable for monitoring natural earthquakes in harsh environments such as the seabed. Fiber optic detectors based on fiber optic interference technology have the potential to monitor long-period vibration signals. Therefore, interference fiber optic seismometers are a hot research topic at home and abroad, and certain results have been achieved. At the same time, corresponding to the index calibration method for electromechanical seismometers, the index calibration methods for fiber optic seismometers also need to be developed accordingly.

The testing of key performance indicators of ultra-wideband electromechanical seismometers is generally completed by a combination of two methods: shaking table testing (absolute calibration) and coil excitation testing (relative calibration). Existing domestic ultra-low-frequency vibration measurement devices can only accurately test the frequency band above 0.1Hz, so the vibration table is only used to test parameters from 0.1Hz to high frequency bands. According to the seismometer testing regulations of the China Earthquake Administration, the coil excitation test method (sine calibration or step calibration) is adopted for the low-frequency end parameter index of the ultra-wideband electromechanical seismometer below 0.1 Hz; the low-frequency end is measured through a high-precision analog signal generator Relative amplitude-frequency characteristics, period, damping and other parameters are used to obtain the amplitude-frequency characteristics of the complete frequency band.

For ultra-wideband fiber optic seismometers, ultra-low-frequency vibration measurement devices can still be used to accurately test its performance indicators in the frequency band above 0.1 Hz. However, its sensing probe is all-fiber passive, and its working principle is completely different from that of electromechanical seismometers. For low frequency bands below 0.1Hz, the relative calibration method of magnetic excitation testing used by electromechanical seismometers is not suitable for Ultra-wideband fiber optic seismometer. Currently, there is no effective low-frequency performance testing and calibration technology for fiber optic seismometers.

Contents of the invention

Based on the problems existing in the existing technology, the present invention provides a calibration method and a control method for low-frequency performance testing of all-fiber detectors. The specific plans are as follows:

A calibration method for low-frequency performance testing of all-fiber detectors, including the following:

Install the preset detection probe on the all-fiber detector to be tested, and add a preset parallel plate capacitor structure at both ends of the detection probe;

Apply an AC voltage signal to the parallel plate capacitor structure to drive the detection probe to vibrate up and down, causing the optical fiber on the detection probe to deform in an AC form;

Obtain the phase change amount of the optical fiber through a preset demodulation algorithm, and combine the frequency and amplitude of the AC voltage signal to establish a first relationship between the phase change amount and the AC voltage signal;

Apply an AC voltage signal in the frequency band below 0.1 Hz to the parallel plate capacitor structure, obtain the phase change amount of the optical fiber under the AC voltage signal in this frequency band, and obtain the frequency and amplitude of the detection probe based on the conversion based on the first relationship, To achieve testing and calibration of the low-frequency performance of the all-fiber detector.

In a specific embodiment, it further includes: after obtaining the first relationship, applying an AC voltage signal above 0.1 Hz to the parallel plate capacitor structure to test and calibrate the high-frequency performance of the all-fiber detector, Obtain the first test result; determine whether the first test result and the preset high-frequency performance test result of the all-fiber detector meet the preset test requirements: if so, based on the first relationship, the all-fiber detector is Carry out test calibration of low-frequency performance; if not, adjust the parameters during the test and re-obtain the first relationship.

In a specific embodiment, the detection probe includes an inertial mass block, a first compliant cylinder, a second compliant cylinder, a first optical fiber and a second optical fiber; the first optical fiber is wound around the first compliant cylinder A first spring body is formed on the body, and the first spring body is equivalent to a spring oscillator structure; the second optical fiber is wound around the second compliant cylinder to form a second spring body, and the second spring body is equivalent to a spring oscillator structure. It is a spring oscillator structure.

In a specific embodiment, "applying an AC voltage signal to the parallel plate capacitor structure to drive the up and down vibration of the detection probe, causing the optical fiber on the detection probe to deform in an AC form" includes: applying an AC voltage signal to the parallel plate capacitor structure. The structure applies an AC voltage signal, and the positive and negative electrodes of the parallel plate capacitor structure change in alternating current, causing vibration; the inertial mass block senses the vibration of the parallel plate capacitor structure and generates relative displacement; the first compliant cylinder and the second The compliant cylinder is driven by the inertial mass block to deform, which in turn causes the first optical fiber and the second optical fiber to undergo phase changes due to deformation, and the first optical fiber and the second optical fiber deform in opposite directions.

In a specific embodiment, the first optical fiber and the second optical fiber form two arms of a Michelson interferometer; when vibration comes, the first optical fiber and the second optical fiber are stretched and squeezed respectively, Thus, the two arms of the Michelson interferometer have phase changes in opposite directions; the phase change of the Michelson interferometer is accurately demodulated through the phase generation carrier modulation and demodulation algorithm, and the phase changes of the first optical fiber and the second optical fiber are obtained. quantity.

In a specific embodiment, an AC voltage signal in the 360s-0.1Hz frequency band is applied to the parallel plate capacitor structure to test and calibrate the performance index of the all-fiber detector in the 360s-0.1Hz frequency band; by changing the AC voltage signal to adjust the amplitude of the detection probe.

In a specific embodiment, multiple node frequencies are selected in the 360s-0.1Hz frequency band; AC voltage signals at each node frequency are applied to the parallel plate capacitor structure, and the AC voltage signals at each node frequency have different amplitudes. relation.

In a specific embodiment, when an AC voltage signal is applied to the parallel plate capacitor structure, the electric field E is:

The driving force exerted by the inertial mass block, the first spring body, and the second spring body under AC voltage is:

in,

is the charge density, Q=CV(t) is the surface charge, C is the capacitance, ε is the equivalent dielectric constant, and V(t) is the voltage of the AC voltage signal.

In a specific embodiment, the mechanical equation under the action of driving force F is:

Among them, h is the height variable of the inertial mass block, γ is the equivalent damping coefficient of the first spring body and the second spring body, and k is the equivalent spring coefficient of the first spring body and the second spring body.

A calibration system for low-frequency performance testing of all-fiber detectors, including the following:

The preparation unit is used to install the preset detection probe on the all-fiber detector to be tested, and add a preset parallel plate capacitor structure to both ends of the detection probe;

A driving unit used to apply an AC voltage signal to the parallel plate capacitor structure to drive the detection probe to vibrate up and down, causing the optical fiber on the detection probe to deform in an AC form;

A calculation unit configured to obtain the phase change amount of the optical fiber through a preset demodulation algorithm, and establish a first relationship between the phase change amount and the AC voltage signal in combination with the frequency and amplitude of the AC voltage signal;

A test unit, used to apply an AC voltage signal in a frequency band below 0.1 Hz to the parallel plate capacitor structure, obtain the phase change amount of the optical fiber under the AC voltage signal in this frequency band, and obtain the detection probe based on the first relationship conversion The frequency and amplitude are used to test and calibrate the low-frequency performance of the all-fiber detector.

In a specific embodiment, it also includes:

A verification unit, configured to apply an AC voltage signal above 0.1 Hz to the parallel plate capacitor structure after obtaining the first relationship, so as to test and calibrate the high-frequency performance of the all-fiber detector and obtain the first test result. ; Determine whether the first test result and the preset high-frequency performance test result of the all-fiber detector meet the preset test requirements: if so, based on the first relationship, perform a low-frequency performance test on the all-fiber detector Calibration; if not, adjust the parameters during the test process and re-obtain the first relationship.

A calibration device for low-frequency performance testing of all-fiber detectors, used to implement any of the above calibration methods, the calibration device includes:

An all-fiber detector carries a detection probe on which an optical fiber is wound;

The parallel plate capacitor structure includes a first plate body, a second plate body and a circuit unit. The circuit unit is connected to the first plate body and the second plate body; one end of the detection probe is connected to the first plate body. body, and the other end is connected to the second plate body;

A waveform generator connected to the circuit unit and used to apply an AC voltage signal to the parallel plate capacitor structure;

A coupler, connected to the detection probe, and forming a Michelson interferometer with the detection probe;

Phase demodulation module, used to obtain the phase change of the optical fiber through the demodulation algorithm;

The signal acquisition and processing module is connected to the phase demodulation module and is used to calculate the low-frequency performance of the all-fiber detector based on the phase change of the optical fiber.

In a specific embodiment, the detection probe includes a housing, an inertial mass block, a first compliant cylinder, a second compliant cylinder, a first optical fiber and a second optical fiber; the first optical fiber is wound around the first A first spring body is formed on the compliant cylinder, and the first spring body is equivalent to a spring oscillator structure; the second optical fiber is wound around the second compliant cylinder to form a second spring body, and the second spring The body is equivalent to a spring oscillator structure; the first compliant cylinder, the second compliant cylinder, the inertial mass block, the first optical fiber and the second optical fiber are located in the housing.

In a specific embodiment, the inertial mass block has a push-pull structure to improve sensing sensitivity; and/or a Faraday mirror is provided at the tail end of the first optical fiber and the second optical fiber to weaken the Polarization fading effects caused by polarization states in fiber waveguides.

Beneficial effects: The present invention provides a calibration method, system and device for low-frequency performance testing of all-fiber detectors. Based on parallel plate capacitive excitation, the invention effectively realizes low-frequency performance testing and calibration of optical fiber seismometers, with high detection accuracy and low detection cost. It is easy to operate and fills the technical gap in the current low-frequency performance testing and calibration of all-fiber passive probes for optical fiber interference seismometers. A parallel metal plate is attached to the geophone probe and an alternating voltage signal of 360s-0.1Hz is given, causing the inertial mass block to vibrate up and down, thereby simulating external vibration signals, thereby achieving testing and calibration of the low-frequency performance of the fiber optic seismometer.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present invention more clearly, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a flow chart of the calibration method of the present invention;

Figure 2 is a structural diagram of the mandrel type push-pull conformal cylinder optical fiber detector of the present invention;

Figure 3 is a schematic diagram of the parallel plate capacitor structure of the present invention;

Figure 4 is a frequency response characteristic curve diagram of the silicone compliant cylinder under AC action of the present invention;

Figure 5 is a partial enlarged view of the present invention based on Figure 4;

Figure 6 is a schematic diagram of the calibration system module of the present invention;

Figure 7 is an example diagram of the calibration device of the present invention.

Reference symbols: A1-preparation unit; A2-driving unit; A3-calculation unit; A4-test unit; A5-verification unit; 1-parallel plate capacitor structure; 2-detection probe; 11-first plate body; 12- Second board; 13-circuit unit; 21-first compliant cylinder; 22-second compliant cylinder; 23-inertial mass block; 24-first optical fiber; 25-second optical fiber; 26-casing; 27 - Faraday mirror; 31-laser light source; 32-isolator; 33-coupler; 34-photodetector; 35-modulator; 36-phase demodulation module; 37-signal acquisition and processing module.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Currently, there is a mature relative calibration method for electromechanical seismometers, namely the coil excitation test method. However, the sensing probe of the fiber optic seismometer is all-fiber passive, which is also one of its advantages compared with the electromechanical seismometer. However, the coil excitation test method cannot be applied to the fiber optic seismometer, and there is no effective method for the fiber optic seismometer. Low-frequency performance test calibration solution.

Example 1

This embodiment proposes a calibration method for low-frequency performance testing of all-fiber geophones. Based on the parallel plate capacitive excitation method, it achieves accurate testing and calibration of the low-frequency performance of fiber optic seismometers, filling the gap between all-fiber passive probes of current fiber optic interference seismometers. There is a technical gap in low-frequency performance testing and calibration. The flow chart of the calibration method is shown in Figure 1 of the manual. The specific plans are as follows:

A calibration method for low-frequency performance testing of all-fiber detectors, including the following steps:

101. Install the preset detection probe on the all-fiber detector to be tested, and add a preset parallel plate capacitor structure at both ends of the detection probe;

102. Apply an AC voltage signal to the parallel plate capacitor structure to drive the detection probe to vibrate up and down, causing the optical fiber on the detection probe to deform in an AC form;

103. Obtain the phase change amount of the optical fiber through the preset demodulation algorithm, and combine the frequency and amplitude of the AC voltage signal to establish the first relationship between the phase change amount and the AC voltage signal;

104. Apply an AC voltage signal in the frequency band below 0.1Hz to the parallel plate capacitor structure, obtain the phase change of the optical fiber under the AC voltage signal in this frequency band, and obtain the frequency and amplitude of the detection probe based on the first relationship conversion to achieve full detection. Test and calibration of low-frequency performance of fiber optic detectors.

For the interference type fiber optic ultra-wideband seismometer, this embodiment designs a core-type push-pull compliant cylinder all-fiber detection probe structure, and sets the detection probe on the interference type fiber optic ultra-wideband seismometer to be tested. Able to realize all-fiber passive detection function. The structure of the mandrel-type push-pull conformable cylinder optical fiber detector is shown in Figure 2 of the manual. For the mandrel-type push-pull conformal cylinder all-fiber detection probe structure, this embodiment proposes a calibration method based on parallel plate capacitance excitation testing. The parallel plate capacitance excitation test structure is designed and parallel metal is connected to the all-fiber detector. The plate forms a capacitive structure, and a low-frequency alternating voltage (0.1Hz-360s) is applied to realize artificial control of the vibration signal on the probe for low-frequency performance testing and calibration of the all-fiber detection probe. The parallel plate capacitor structure is shown in Figure 3 of the specification.

Specifically, the mandrel-type push-pull compliant cylinder optical fiber detection probe (referred to as the detection probe) includes an inertial mass block, a first compliant cylinder, a second compliant cylinder, a first optical fiber and a second optical fiber. Wherein, the first optical fiber is wound around the first compliant cylinder to form a first spring body, and the first spring body is equivalent to a spring oscillator structure; the second optical fiber is wound around the second compliant cylinder to form a second spring body, and the second spring body is equivalent to a spring oscillator structure. The spring body is equivalent to a spring oscillator structure.

Preferably, the compliant cylinder is made of silica gel and the optical fiber is wound around it, which not only reduces the equivalent elastic coefficient, but also has good low-frequency response characteristics. An inertial mass block is added in the middle of the compliant cylinder. Preferably, the inertial mass block is a metal block, such as an inertial brass mass block. Further preferably, the inertial mass block is designed as a push-pull structure, which can improve the sensing sensitivity. Preferably, a Faraday mirror is designed at the end of the sensing fiber to weaken the polarization fading effect caused by the polarization state in the fiber waveguide. The silicone compliant cylinder and the wound optical fiber form a spring oscillator structure; the inertial brass mass block can sense the vibration of the housing and produce relative displacement.

The changes in the internal structure of the detection probe specifically include: applying an AC voltage signal to the parallel plate capacitor structure, the positive and negative charges of the parallel plate capacitor structure change in AC, and together with the inertial mass block, produce an AC changing Coulomb force, causing the up and down vibration of the inertial mass block; The first compliant cylinder and the second compliant cylinder are driven by the inertial mass block to deform, which in turn causes the first optical fiber and the second optical fiber to undergo phase changes due to the deformation, and the first optical fiber and the second optical fiber deform in opposite directions. For passive probes, the alternating capacitance mode is used to excite the inertial mass block on the probe to vibrate up and down, causing the compliant cylinder to "squeeze" and "stretch", causing the phase of the "compression" and "stretch" deformation of the wound optical fiber. Variety. The up and down vibration of the detection probe is also to better meet the testing requirements. Preferably, the alternating electrical signal is set to 360s-0.1Hz, which can test and calibrate the performance index of the optical fiber seismometer in the 360s-0.1Hz frequency band.

The arbitrary waveform generator only needs to give the parallel plate capacitor structure a low-frequency alternating voltage signal to complete the low-frequency performance test and calibration of the mandrel-type push-pull conformal cylinder detector. No complex auxiliary equipment and instruments are needed. It is simple and easy. Testing costs are low.

Design parallel plate capacitance excitation test and calibration technology to effectively realize low-frequency performance testing and calibration of fiber optic seismometers. Specifically: the signal output by the arbitrary waveform generator is used as an AC drive signal for the parallel plate capacitor; the positive and negative electrodes of the parallel plate charge change AC to drive the inertial mass block to vibrate up and down, driving the silica gel wrapped around the optical fiber equivalent to a spring body to follow the change. The cylinder is "squeezed" or "stretched", causing the optical fiber length to deform in an AC form, and its change frequency is equivalent to the AC drive signal output by the waveform generator.

Figure 3 of the description provides a parallel plate capacitor structure, including a first plate body, a second plate body and a circuit unit. The circuit unit is connected to the first plate body and the second plate body; one end of the detection probe is connected to the The other end of the first plate body is connected to the second plate body. This parallel-plate capacitor structure is fully compatible with the mandrel-type push-pull compliant cylinder structure. It only needs to add metal parallel plates at both ends. It is simple and easy to operate, efficient and accurate.

The calibration method of this embodiment requires first confirming the relationship between the AC voltage signal and the optical fiber phase change, and this relationship is named the first relationship. Therefore, after obtaining the first relationship, it is necessary to confirm whether the relationship is accurate. The calibration method also includes: after obtaining the first relationship, applying an AC voltage signal above 0.1Hz to the parallel plate capacitor structure to test and calibrate the high-frequency performance of the all-fiber detector to obtain the first test result; judging the first test result Whether the preset high-frequency performance test results of the all-fiber detector meet the preset test requirements: If yes, based on the first relationship, perform a low-frequency performance test calibration on the all-fiber detector; if not, adjust the test process Parameters to re-obtain the first relationship.

In order to verify the feasibility of measuring the first relationship, AC voltage signals at high frequency points above 0.1Hz can be selected to perform performance tests on all-fiber detectors, and at the same time, the vibration table absolute calibration test method can be used to perform indicator tests at the same frequency. Method results are compared to evaluate the effectiveness and accuracy of the specimen plan. The preset test requirement is whether the first test result and the high-frequency performance test result are the same within the preset accuracy requirement. Only when the first test result is the same as the high-frequency performance test result can the first relationship be determined to be correct. When the first relationship is incorrect, it is necessary to adjust the relevant parameters during the test process and re-obtain the first relationship until the correct first relationship is obtained.

Among them, the first optical fiber and the second optical fiber constitute the two arms of the Michelson interferometer (i.e., the sensing arm and the reference arm); when vibration comes, the first optical fiber and the second optical fiber are stretched and squeezed, thereby causing the Michelson interference The two arms of the instrument have phase changes in opposite directions. The phase change of the Michelson interferometer is accurately demodulated through the phase generation carrier modulation and demodulation algorithm, and the phase changes of the first optical fiber and the second optical fiber are obtained.

Preferably, the first optical fiber and the second optical fiber are connected to a coupler. The coupler and the detection probe form a Michelson interferometer. The silica gel conformable cylinder wound by the sensing fiber at the upper and lower positions of the inertial mass block of the detection probe senses external vibration signals. And the deformation of the wound optical fiber is caused by the deformation of the conforming cylinder. The upper and lower sections of the wound optical fiber form the two arms of the Michelson interferometer. When the vibration signal comes, due to the up and down vibration of the inertial mass block, the upper and lower sections of the optical fiber are stretched and squeezed respectively. The voltage is applied, so that the two arms of the interferometer have phase changes in opposite directions; the phase change can be obtained through the phase generation carrier modulation and demodulation algorithm, and then the external vibration signal can be measured.

Michelson interferometer is the most common type of optical interferometer. Its principle is that an incident light is divided into two beams through a spectroscope and then each is reflected back by the corresponding plane mirror. Because the two beams of light have the same frequency, The vibration directions are the same and the phase difference is constant (that is, the interference conditions are met), so interference can occur. The different optical path lengths of the two light beams in interference can be achieved by adjusting the length of the interference arm and changing the refractive index of the medium, thereby forming different interference patterns.

Preferably, an AC voltage signal in the 360s-0.1Hz frequency band is applied to the parallel plate capacitor structure to test and calibrate the performance index of the all-fiber detector in the 360s-0.1Hz frequency band; the detection probe is adjusted by changing the amplitude of the AC voltage signal. amplitude. Multiple node frequencies are selected in the 360s-0.1Hz frequency band, and AC voltage signals at each node frequency are applied to the parallel plate capacitor structure, and the AC voltage signals at each node frequency have a size relationship in amplitude. For example, set the applied AC voltage frequency to several key node frequencies between 360s and 0.1Hz, such as 360s, 300s, 200s, 100s, 50s, 20s, and 10s, and modulate the amplitude from small to large.

As shown in Figure 1, apply AC voltage

It acts on the parallel plate capacitor structure and acts on the inertial mass block (mass m, area A). The height variable of the inertial mass block is h, the equivalent damping coefficient of the silicone conformable cylinder wrapped with optical fiber is γ, the equivalent spring coefficient is k, and the equivalent dielectric constant is ε; when an AC voltage signal is applied to the parallel plate capacitor structure, the electric field E is:

in,

is the charge density, Q=CV(t) is the surface charge, C is the capacitance, ε is the equivalent dielectric constant, and V(t) is the voltage of the AC voltage signal. The mechanical equation under the action of driving force F is:

Among them, h is the height variable of the inertial mass block, γ is the equivalent damping coefficient of the first spring body and the second spring body, and k is the equivalent spring coefficient of the first spring body and the second spring body. The function h(t) or h(ω) of the height change of the inertial mass block with time is obtained through formulas (1) and (2), which directly corresponds to the change of the length of the wound optical fiber (ie, phase change) with time. Among them, (frequency f=2π/ω can be set below 0.1Hz to 360s).

The phase change amount of the optical fiber is obtained through the phase generation carrier modulation and demodulation algorithm suitable for the Michelson interference structure of the optical fiber. V(t) gives a vibration signal to the detection probe, causing the phase change of the wound optical fiber; if V(t) is a signal with a frequency of 360s-0.1Hz, the vibration frequency of the sensing probe is 360s-0.1Hz; and V(t) The amplitude is directly related to the magnitude of the sensing probe amplitude. Read the frequency and amplitude of V(t), and determine the conversion relationship to obtain the frequency and amplitude of the vibration of the sensing probe, and then detect the low-frequency response characteristics of the all-fiber passive probe.

Preferably, the measurement of low-frequency response characteristics that can be achieved by the calibration method of this embodiment includes: testing and calibrating key indicators such as operating frequency, responsivity, and dynamic range of the all-fiber detector. Simulation analysis proves that the solution of the present invention can effectively measure the performance of all-fiber geophones and is an effective means for testing the low-frequency performance of fiber optic geophones. Figure 4 of the description shows the frequency response characteristic curve of the silica gel compliant cylinder with various parameter settings under AC action. Figure 5 of the description is a partial enlarged view of Figure 4 (0.001Hz-100Hz).

This embodiment provides a calibration method for low-frequency performance testing of all-fiber detectors. Based on parallel plate capacitive excitation, it effectively realizes low-frequency performance testing and calibration of fiber-optic seismometers. It has high detection accuracy, low detection cost, and simple operation, filling the gap between At present, there is a technical gap in the low-frequency performance testing and calibration of all-fiber passive probes for optical fiber interference seismometers. A parallel metal plate is attached to the geophone probe and an alternating voltage signal of 360s-0.1Hz is given, causing the inertial mass block to vibrate up and down, thereby simulating external vibration signals, thereby achieving testing and calibration of the low-frequency performance of the fiber optic seismometer.

Example 2

This embodiment provides a calibration system for low-frequency performance testing of all-fiber detectors, which systematizes the calibration method of Embodiment 1. The module schematic diagram of the calibration system is shown in Figure 6 of the description. The specific scheme is as follows:

The preparation unit A1 is used to install the preset detection probe on the all-fiber detector to be tested, and add a preset parallel plate capacitor structure at both ends of the detection probe;

The driving unit A2 is used to apply an AC voltage signal to the parallel plate capacitor structure to drive the detection probe to vibrate up and down, causing the optical fiber on the detection probe to deform in an AC form;

The calculation unit A3 is used to obtain the phase change amount of the optical fiber through a preset demodulation algorithm, and combine the frequency and amplitude of the AC voltage signal to establish a first relationship between the phase change amount and the AC voltage signal;

Test unit A4 is used to apply an AC voltage signal in the frequency band below 0.1Hz to the parallel plate capacitor structure, obtain the phase change of the optical fiber under the AC voltage signal in this frequency band, and obtain the frequency and amplitude of the detection probe based on the first relationship conversion, To achieve testing and calibration of the low-frequency performance of all-fiber detectors.

Verification unit A5 is used to, after obtaining the first relationship, apply an AC voltage signal above 0.1Hz to the parallel plate capacitor structure to test and calibrate the high-frequency performance of the all-fiber detector, and obtain the first test result; determine the first test Whether the results and the preset high-frequency performance test results of the all-fiber detector meet the preset test requirements: If yes, then based on the first relationship, perform a low-frequency performance test calibration on the all-fiber detector; if not, adjust the test process Parameters in , re-obtain the first relationship.

As shown in Figure 1, apply AC voltage

On the inertial mass block (mass is m, area is A). The height variable of the mass block is h, the equivalent damping coefficient of the silica gel conformable cylinder wrapped with optical fiber is γ, the equivalent spring coefficient is k, and the equivalent dielectric constant is ε; when an AC voltage signal is applied to the parallel plate capacitor structure, the electric field E for:

in,

The phase change of the wound sensing fiber is obtained by the phase generation carrier modulation and demodulation algorithm suitable for the Michelson interference structure of the fiber. V(t) gives a vibration signal to the detection probe, causing the phase change of the wound optical fiber; if V(t) is a signal with a frequency of 360s-0.1Hz, the vibration frequency of the sensing probe is 360s-0.1Hz; and V(t) The amplitude is directly related to the magnitude of the sensing probe amplitude. Read the frequency and amplitude of V(t), and determine the conversion relationship to obtain the frequency and amplitude of the vibration of the sensing probe, and then detect the low-frequency response characteristics of the all-fiber passive probe.

Preferably, the measurement of low-frequency response characteristics that can be achieved by the calibration method of this embodiment includes testing and calibrating key indicators such as operating frequency, responsivity, and dynamic range of the all-fiber detector.

This embodiment provides a calibration system for low-frequency performance testing of an all-fiber detector, which systematizes the calibration method for low-frequency performance testing of an all-fiber detector in Embodiment 1, making it more practical.

Example 3

This embodiment provides a calibration device for low-frequency performance testing of an all-fiber detector, which can implement the calibration method of Embodiment 1. The specific plans are as follows:

A calibration device for low-frequency performance testing of all-fiber detectors, including:

The all-fiber detector carries a detection probe 2, and the detection probe 2 is wound with an optical fiber;

The parallel plate capacitor structure 1 includes a first plate 11, a second plate 12 and a circuit unit 13. The circuit unit 13 is connected to the first plate 11 and the second plate 12; one end of the detection probe 2 is connected to the first plate 11 , the other end is connected to the second plate body 12;

A waveform generator connected to the circuit unit for applying an AC voltage signal to the parallel plate capacitor structure;

Coupler 33 is connected to the detection probe 2, and forms a Michelson interferometer with the detection probe 2;

Phase demodulation module 36, used to obtain the phase change of the optical fiber through a demodulation algorithm;

The signal acquisition and processing module 17 is connected to the phase demodulation module 36 and is used to calculate the low-frequency performance of the all-fiber detector based on the phase change of the optical fiber.

The detection probe, as shown in Figure 2 of the specification, includes a housing 26, an inertial mass block 23, a first compliant cylinder 21, a second compliant cylinder 22, a first optical fiber 24 and a second optical fiber 25; the first optical fiber 24 The second optical fiber 25 is wound around the first compliant cylinder 21 to form a first spring body. The first spring body is equivalent to a spring oscillator structure. The second optical fiber 25 is wound around the second compliant cylinder 22 to form a second spring body. The second spring body Equivalent to a spring oscillator structure; the first compliant cylinder 21, the second compliant cylinder 22, the inertial mass block 23, the first optical fiber 24 and the second optical fiber 25 are located in the housing 26. The upper and lower parts of the housing 26 are respectively provided with aluminum bases to achieve electrical connection with the parallel plate capacitor 1 structure.

Preferably, the compliant cylinder is made of silica gel and the optical fiber is wound around it, which not only reduces the equivalent elastic coefficient, but also has good low-frequency response characteristics. An inertial mass block is added in the middle of the compliant cylinder. Preferably, the inertial mass block 23 is a metal block, such as an inertial brass mass block. Further preferably, the inertial mass block 23 is designed as a push-pull structure, which can improve the sensing sensitivity. Preferably, a Faraday mirror 27 is designed at the end of the sensing fiber to weaken the polarization fading effect caused by the polarization state in the fiber waveguide. The silicone compliant cylinder and the wound optical fiber form a spring oscillator structure; the inertial brass mass block senses the vibration of the housing and produces relative displacement.

Figure 7 of the description shows an example of a calibration device, including a laser light source 31, isolator 32, coupler 33, photodetector 34, modulator 35, phase demodulation module 36, signal acquisition and processing module 37, detection Probe 2 and parallel plate capacitor structure 1. The laser light source 31 uses a narrow linewidth laser light source, which is a distributed feedback (DFB) laser with a wavelength near 1550nm, and outputs continuous light with a pulse width of 10kHz to subsequent components; the subsequent components include an isolator 32, a coupler 33, and a photodetector 34. Modulator 35, phase demodulation module 36, signal acquisition and processing module 37, etc. The coupler 33 is connected to the first optical fiber 24 and the second optical fiber 25 respectively, and the first optical fiber 24 and the second optical fiber 25 serve as the sensing arm and the reference arm respectively. The photodetector 34 is connected to the coupler 33 and the phase demodulation module 36 respectively. The phase demodulation module 36 performs phase demodulation according to the output result of the modulator 35 and the result of the coupler 33 to obtain the phase change amount of the optical fiber and output it to Signal acquisition and processing module 37. The signal acquisition and processing module 37 calculates the low-frequency performance of the all-fiber detector based on the phase change of the optical fiber.

The most important one is the Michelson interferometer composed of the coupler 33 and the detection probe 2. The silica gel compliant cylinder wrapped with the sensing fiber in the detection probe 2 senses external vibration signals and causes the deformation of the wrapped optical fiber through the deformation of the compliant cylinder. , the upper and lower sections of wound optical fiber form the two arms of the Michelson interferometer; when the vibration signal comes, due to the up and down vibration of the inertial mass block, the upper and lower sections of wound optical fiber are stretched and squeezed respectively, so that the two arms of the interferometer have opposite directions. The phase change; through the phase generation carrier modulation and demodulation algorithm, the phase change can be obtained, and then the external vibration signal can be measured.

The present invention provides a calibration method, system and device for low-frequency performance testing of all-fiber detectors. Based on parallel plate capacitive excitation, the low-frequency performance testing and calibration of optical fiber seismometers are effectively realized, with high detection accuracy, low detection cost, and simple operation. , filling the current technical gap in low-frequency performance testing and calibration of all-fiber passive probes for optical fiber interference seismometers. A parallel metal plate is attached to the geophone probe and an alternating voltage signal of 360s-0.1Hz is given, causing the inertial mass block to vibrate up and down, thereby simulating external vibration signals, thereby achieving testing and calibration of the low-frequency performance of the fiber optic seismometer.

Those of ordinary skill in the art should understand that the above-mentioned modules of the present invention can be implemented using a general computing system. They can be concentrated on a single computing system, or distributed on a network composed of multiple computing systems. Alternatively, They can be implemented with program codes executable by the computer system, so that they can be stored in a storage system and executed by the computing system, or they can be made into individual integrated circuit modules, or they can be made into multiple modules or steps. implemented as a single integrated circuit module. As such, the invention is not limited to any specific combination of hardware and software.

Note that the above are only the preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments herein, and that various obvious changes, readjustments and substitutions can be made to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, it can also include more other equivalent embodiments, and the present invention The scope is determined by the scope of the appended claims.

What is disclosed above are only a few specific implementation scenarios of the present invention. However, the present invention is not limited thereto. Any changes that can be thought of by those skilled in the art should fall within the protection scope of the present invention.

Claims

A calibration method for low-frequency performance testing of all-fiber detectors, which is characterized by including the following:

Install the preset detection probe on the all-fiber detector to be tested, and add a preset parallel plate capacitor structure at both ends of the detection probe;

Apply an AC voltage signal to the parallel plate capacitor structure to drive the detection probe to vibrate up and down, causing the optical fiber on the detection probe to deform in an AC form;

Obtain the phase change amount of the optical fiber through a preset demodulation algorithm, and combine the frequency and amplitude of the AC voltage signal to establish a first relationship between the phase change amount and the AC voltage signal;

Apply an AC voltage signal in the frequency band below 0.1 Hz to the parallel plate capacitor structure, obtain the phase change amount of the optical fiber under the AC voltage signal in this frequency band, and obtain the frequency and amplitude of the detection probe based on the conversion based on the first relationship, To achieve testing and calibration of low-frequency performance of the all-fiber detector.
The calibration method according to claim 1, further comprising:

After obtaining the first relationship, apply an AC voltage signal above 0.1 Hz to the parallel plate capacitor structure to perform high-frequency performance test calibration of the all-fiber detector to obtain the first test result;

Determine whether the first test result and the preset high-frequency performance test result of the all-fiber detector meet the preset test requirements:

If so, then based on the first relationship, perform low-frequency performance test calibration on the all-fiber detector;

If not, adjust the parameters during the test process and reacquire the first relationship.
The calibration method according to claim 1, characterized in that the detection probe includes an inertial mass block, a first compliant cylinder, a second compliant cylinder, a first optical fiber and a second optical fiber;

The first optical fiber is wound around the first compliant cylinder to form a first spring body, and the first spring body is equivalent to a spring vibrator structure;

The second optical fiber is wound around the second compliant cylinder to form a second spring body, and the second spring body is equivalent to a spring vibrator structure.
The calibration method according to claim 3, characterized in that "applying an AC voltage signal to the parallel plate capacitor structure to drive the up and down vibration of the detection probe, causing the optical fiber on the detection probe to deform in an AC form" includes :

Applying an AC voltage signal to the parallel plate capacitor structure causes the positive and negative charges of the parallel plate capacitor structure to change alternately, causing vibration;

The inertial mass block senses the vibration of the parallel plate capacitor structure and generates relative displacement;

The first compliant cylinder and the second compliant cylinder are driven by the inertial mass block to deform, which in turn causes the first optical fiber and the second optical fiber to undergo phase changes due to deformation, and the first optical fiber and the second optical fiber are deformed. The direction of deformation of the second optical fiber is opposite.
The calibration method according to claim 3, characterized in that the first optical fiber and the second optical fiber constitute two arms of a Michelson interferometer;

When vibration occurs, the first optical fiber and the second optical fiber are stretched and squeezed respectively, so that the two arms of the Michelson interferometer have phase changes in opposite directions;

The phase change of the Michelson interferometer is accurately demodulated through the phase generation carrier modulation and demodulation algorithm to obtain the phase change amount of the first optical fiber and the second optical fiber.
The calibration method according to claim 1, characterized in that an AC voltage signal in the frequency band of 360s-0.1Hz is applied to the parallel plate capacitor structure to test the performance index of the all-fiber detector in the frequency band of 360s-0.1Hz. calibration;

The amplitude of the detection probe is adjusted by changing the amplitude of the AC voltage signal.
The calibration method according to claim 6, characterized in that multiple node frequencies are selected in the 360s-0.1Hz frequency band;

AC voltage signals at each node frequency are applied to the parallel plate capacitor structure, and there is a magnitude relationship between the AC voltage signals at each node frequency.
The calibration method according to claim 3, characterized in that when an AC voltage signal is applied to the parallel plate capacitor structure, the electric field E is:

The driving force exerted by the inertial mass block, the first spring body, and the second spring body under AC voltage is:

in,
is the charge density, Q=CV(t) is the surface charge, C is the capacitance, ε is the equivalent dielectric constant, and V(t) is the voltage of the AC voltage signal.
The calibration method according to claim 8, characterized in that the mechanical equation under the action of the driving force F is:

Among them, h is the height variable of the inertial mass block, γ is the equivalent damping coefficient of the first spring body and the second spring body, and k is the equivalent spring coefficient of the first spring body and the second spring body.
A calibration system for low-frequency performance testing of all-fiber detectors, which is characterized by the following:

The preparation unit is used to install the preset detection probe on the all-fiber detector to be tested, and add a preset parallel plate capacitor structure to both ends of the detection probe;

A driving unit used to apply an AC voltage signal to the parallel plate capacitor structure to drive the detection probe to vibrate up and down, causing the optical fiber on the detection probe to deform in an AC form;

A calculation unit configured to obtain the phase change amount of the optical fiber through a preset demodulation algorithm, and establish a first relationship between the phase change amount and the AC voltage signal in combination with the frequency and amplitude of the AC voltage signal;

A test unit, used to apply an AC voltage signal in a frequency band below 0.1 Hz to the parallel plate capacitor structure, obtain the phase change amount of the optical fiber under the AC voltage signal in this frequency band, and obtain the detection probe based on the first relationship conversion The frequency and amplitude are used to test and calibrate the low-frequency performance of the all-fiber detector.
The calibration system according to claim 10, further comprising:

A verification unit, configured to apply an AC voltage signal above 0.1 Hz to the parallel plate capacitor structure after obtaining the first relationship, so as to test and calibrate the high-frequency performance of the all-fiber detector and obtain the first test result. ;

Determine whether the first test result and the preset high-frequency performance test result of the all-fiber detector meet the preset test requirements:

If so, then based on the first relationship, perform low-frequency performance test calibration on the all-fiber detector;

If not, adjust the parameters during the test process and reacquire the first relationship.
A calibration device for low-frequency performance testing of all-fiber detectors, characterized in that it is used to implement the calibration method according to any one of claims 1 to 9, and the calibration device includes:

An all-fiber detector carries a detection probe on which an optical fiber is wound;

The parallel plate capacitor structure includes a first plate body, a second plate body and a circuit unit. The circuit unit is connected to the first plate body and the second plate body; one end of the detection probe is connected to the first plate body. body, and the other end is connected to the second plate body;

A waveform generator connected to the circuit unit and used to apply an AC voltage signal to the parallel plate capacitor structure;

A coupler, connected to the detection probe, and forming a Michelson interferometer with the detection probe;

Phase demodulation module, used to obtain the phase change of the optical fiber through the demodulation algorithm;

The signal acquisition and processing module is connected to the phase demodulation module and is used to calculate the low-frequency performance of the all-fiber detector based on the phase change of the optical fiber.
The calibration device according to claim 12, wherein the detection probe includes a housing, an inertial mass block, a first compliant cylinder, a second compliant cylinder, a first optical fiber and a second optical fiber;

The first optical fiber is wound around the first compliant cylinder to form a first spring body, and the first spring body is equivalent to a spring vibrator structure;

The second optical fiber is wound around the second compliant cylinder to form a second spring body, and the second spring body is equivalent to a spring vibrator structure;

The first compliant cylinder, the second compliant cylinder, the inertial mass block, the first optical fiber and the second optical fiber are located in the housing.
The calibration device according to claim 12, characterized in that the inertial mass block has a push-pull structure to improve sensing sensitivity;

And/or, a Faraday mirror is provided at the tail end of the first optical fiber and the second optical fiber to weaken the polarization fading effect caused by the polarization state in the optical fiber waveguide.