Multi-channel micro-seismic monitoring system and method based on optical fiber sensing

Abstract

The invention discloses a multichannel micro-seismic monitoring system and method based on optical fiber sensing, and belongs to the technical field of optical fiber sensing noise suppression. Intermittent symmetric square wave modulation signals and synchronous trigger signals are output through the signal generation module, the modulation signals control the light source to output lasers in three periodic phase states, the trigger signals synchronously collect three interference electric signals at the rising edge, and the interference signals are collected in combination with intermittent collection. The problems of inter-channel crosstalk, poor synchronism and high system complexity in multi-channel monitoring are solved, and the crosstalk-free parallel processing effect of multi-channel data time division multiplexing is achieved. Meanwhile, three paths of interference signals which are synchronously collected are regarded as spatial discrete points, noise interference is stripped and pure phase information is reserved through spatial conversion modes such as fitting, translation, rotation and mapping, the technical problem that traditional ellipse fitting fails in fitting under weak micro-vibration signals is solved, and the robustness and monitoring precision of weak signal demodulation are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application relates to the field of optical fiber sensing noise suppression, in particular to a multi-channel microseismic monitoring system and method based on optical fiber sensing. BACKGROUND

[0002] In recent years, optical fiber sensing technology has rapidly developed due to its high sensitivity, wide dynamic range, intrinsic safety and anti-electromagnetic interference, and is widely used in the field of microseismic measurement. It uses light waves as carriers to demodulate external vibrations by sensing the changes of physical parameters such as phase, intensity and wavelength of light in the optical fiber.

[0003] PGC (Phase Generated Carrier) demodulation is one of the most core and classical demodulation schemes in optical fiber interferometer sensors. It actively injects a high-frequency carrier signal into the interferometer, modulates the low-frequency and weak signal to be measured onto the carrier, and then generates a base frequency and a multiple frequency signal synchronized with the carrier signal. After mixing and filtering, a pair of quadrature signals is output, and then the vibration signal is demodulated by DCM or ATAN. This method has high circuit complexity and may also cause carrier phase delay problems. Meanwhile, the phase-frequency characteristics of the filter will affect the orthogonality of the output signal, and further affect the demodulation result.

[0004] The 3x3 coupler demodulation scheme directly outputs signals with fixed phase difference by using the inherent symmetric phase characteristics of the 3x3 coupler, and then constructs quadrature signals by using the ellipse fitting method, and further demodulates the vibration information. This scheme has simple structure and lower cost, and does not need complex active modulation. However, this scheme needs to collect two signals at the same time and perform real-time ellipse fitting operation. When the external vibration signal is too weak, the ellipse may not be closed, which may lead to fitting failure and further demodulation failure. Meanwhile, this scheme is easily affected by low-frequency interference. SUMMARY

[0005] In view of the above problems, the application provides a multi-channel microseismic monitoring system and method based on optical fiber sensing. The application outputs intermittent symmetric square wave modulation signals and synchronous trigger signals through a signal generation module. The modulation signals control the light source to output three periodic phase state lasers. The trigger signals are collected synchronously at the rising edge of the three interference signals. The intermittent collection solves the problems of channel crosstalk, poor synchronization and high system complexity in multi-channel monitoring, and realizes the effect of non-crosstalk parallel processing of multi-channel data time division multiplexing. Meanwhile, the three interference signals collected synchronously are regarded as spatial discrete points. The noise interference is stripped by space conversion methods such as fitting, translation, rotation and mapping, and the pure phase information is retained. The technical problem of fitting failure of the traditional ellipse fitting under weak micro-vibration signal is solved, and the robustness and monitoring accuracy of weak signal demodulation are significantly improved.

[0006] To achieve the above object, the technical scheme adopted by the present application is: a multi-channel microseismic signal demodulation method, comprising the following steps: S1: collecting three-way interference signals with fixed phase difference β to form discrete points P i ( x i , y i , z i ); S2: controlling the phase difference by adjusting the amplitude of the modulation signal β respectively 0 and π, collecting corresponding discrete points P i and fitting a spatial straight line L 1 and L 2; S3: calculating the intersection point P 0( x 0, y0, z0) of the straight lines L 1 and L 2 and the normal vector of the plane where it is located, constructing a spatial straight line P 0 passing through the intersection point L 0 and perpendicular to the planes where the two straight lines are located 0; L S4: calculating the angle between the straight line R 0 and the Z-axis or Y-axis, constructing a rotation matrix with the X-axis as the rotation axis and the angle as the rotation angle x ; S5: based on the intersection point P 0 and the rotation matrix R x mapping the collected discrete points P i to discrete points P j ( x j , y j , z j ), and extracting the quadrature signal; S6: performing differential cross-multiplication operation on the quadrature signal to demodulate the phase change caused by external vibration .

[0007] Preferably, the interference signal is represented as: ; wherein, a 1, a 2, a 3 represent the DC bias of the signal, b 1, b 2, b 3 represent the AC amplitude, is the phase change caused by the vibration, β is a fixed phase difference.

[0008] Preferably, the spatial straight line L 1 has a parametric equation as follows: ; Preferably, the spatial straight line L 2 has a parametric equation as follows: ; wherein, i 1, i 2, i 3 are the coordinates corresponding to the directional vectors of the straight line L 1. x 1, y 1, z 1 are the coordinates corresponding to an arbitrary point on the straight line L 1. j 1, j 2, j 3 are the coordinates corresponding to the directional vectors of the straight line L 2. x 2, y 2, z 2 are the coordinates corresponding to an arbitrary point on the straight line L 2. t is a real number parameter.

[0009] Preferably, the spatial straight line L 0 has:

[0010] Meanwhile k 1, k 2, k 3 satisfy the following relationship: ; wherein, x 0, y0, z0 are the coordinates corresponding to the intersection point P 0. k 1, k 2, k 3 are the directional vectors of the straight line L 0. i 1, i 2, i 3 are the coordinates corresponding to the directional vectors of the straight line L 1. j 1, j 2, j 3 are the coordinates corresponding to the directional vectors of the straight line L 2.

[0011] The straight line L The angle between the straight line 0 and the Z axis. ; The direction vector of the straight line k 1, k 2, k 3. L 0.

[0012] The rotation matrix R x is expressed as: ; The angle between the straight line 0 and the Z axis. L

[0013] The discrete point P i is mapped into a discrete point P j (x, y, z). x j The mapping relationship of the discrete point j (x, y, z) j is: ; The angle between the straight line 0 and the Z axis. L x 0, y0, z0 are the coordinates corresponding to the intersection point P 0. y j , z j are orthogonal signals.

[0014] A multi-channel microseismic monitoring method based on optical fiber sensing, comprising the following steps: 1) outputting an intermittent symmetric square wave modulation signal and an intermittent square wave trigger signal strictly synchronized therewith through a signal generation module, the modulation signal controlling a light source module to output three periodic phase state lasers; 2) distributing the modulated laser to N sensing channels through a 1×N optical splitter; 3) each sensing channel converts the phase change caused by external vibration into three interference signals with a fixed phase difference β through an interferometer, and after the three interference signals are converted into three interference electric signals by a photoelectric conversion module, the trigger signal controls a data acquisition module to synchronously collect the three interference electric signals at the rising edge of each pulse and output them to a signal processing module; ​​Step 4: The signal processing module uses the above multi-channel microseismic signal demodulation method to process the three-way interference electrical signals collected by N sensor channels and demodulate the phase change caused by external vibration. .

[0015] Preferably, the sensing channel includes a circulator, an interferometer and a photoelectric conversion module; the interferometer adopts a Michelson interferometer including a coupler, a mass block, an elastic body and a Faraday rotator mirror; the time interval for each pulse of the trigger signal to collect three interference electrical signals is t 1. The interval duration is t 2.

[0016] A multi-channel microseismic monitoring system based on optical fiber sensing includes a signal generating module for outputting an intermittent symmetrical square wave modulation signal and an intermittent square wave trigger signal strictly synchronized therewith, wherein each pulse rising edge of the trigger signal is synchronized with the level switching moment of the modulation signal; a light source module for receiving the modulation signal and outputting a phase-modulated laser; a beam splitter for splitting the laser beam output by the light source into N paths; N sensing channels for converting external vibration signals into three-path interference electrical signals; a data acquisition module for receiving the trigger signal output by the signal processing module and synchronously acquiring the three-path interference electrical signals; and a multi-channel three-path interference electrical signal acquired by the multi-channel microseismic monitoring method described above, and demodulating the phase change signal processing module.

[0017] Due to the adoption of the above technical solution, the present invention has the following beneficial effects.

[0018] (1) The present invention outputs an intermittent symmetrical square wave modulation signal and a synchronous trigger signal through a signal generation module. The modulation signal controls the light source to output lasers in three periodic phase states. The trigger signal synchronously collects three interference electrical signals on the rising edge, thereby solving the problems of crosstalk between channels, poor synchronization, and high system complexity in multi-channel monitoring, and realizing multi-channel high-precision synchronous monitoring. The system structure is simple and easy to expand and maintain.

[0019] (2) The present invention constructs spatial discrete points by collecting three interference signals with a fixed phase difference β, and adjusts the amplitude of the modulation signal to make the phase difference β 0 and π respectively, fitting a spatial straight line L 1 and L 2, and calculate their intersection P 0 and the normal vector of the plane, constructing a vertical space line L 0, and by calculating the straight line L The angle between 0 and the Z axis or Y axis, constructing the rotation matrix R x , based on the intersection P 0 and the rotation matrixR x The collected discrete points are mapped by translation and rotation, and the quadrature signals are directly extracted. Thus, the noise interference is converted into geometric parameters, the noise is stripped through spatial transformation, the pure phase information is reserved, the weak signal demodulation robustness is improved, the signal distortion and non-orthogonality caused by light source fluctuation and environmental interference are solved, the orthogonalization processing of the signal is realized, a high-quality quadrature signal pair is provided for subsequent DCM demodulation, and finally the differential cross multiplication (DCM) algorithm is used for demodulating the quadrature signal.

[0020] (3) The present application realizes high-precision synchronous monitoring of multi-channel microseismic signals through intermittent modulation signals (three levels) and strictly synchronous trigger signals, time sequence control precision reaches nanosecond level; combined with the multi-channel architecture that 1*N optical splitters distribute laser to N independent sensing channels, each channel picks up external vibration signals through a Michelson interferometer, and through precise matching of multi-channel laser distribution and collection time sequence, high-precision synchronous monitoring of multi-channel microseismic signals is realized.

[0021] (4) The present application regards three interference signals as spatial discrete points, replaces traditional ellipse fitting with translation and rotation projection, solves the problem of fitting failure under weak signals; through strict synchronization of modulation signals and trigger signals, combined with intermittent collection (time length t 2), the effect of non-crosstalk parallel processing of time division multiplexing of multi-channel data is realized. Through the spatial geometric demodulation model and the synchronous time-sharing multi-channel architecture, the present application solves the industry problems of weak signal demodulation failure, noise interference and high system complexity, and provides a high-reliability solution for geological disaster warning. BRIEF DESCRIPTION OF DRAWINGS

[0022] The manufacture and use of the preferred embodiments of the present application are discussed in detail below. It should be understood, however, that the present application provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the present application and do not limit the scope of the present application. Other embodiments can be apparent to those of ordinary skill in the art from the drawings and description without departing from the scope of the present application.

[0023] Figure 1 It is a distribution diagram of the discrete points in the spatial rectangular coordinate system of the present application.

[0024] Figure 2 It is a distribution diagram of the mapped discrete points in the spatial rectangular coordinate system of the present application.

[0025] Figure 3 It is a structural diagram of the present application.

[0026] Figure 4 It is a timing diagram of the modulation signal and the trigger signal of the present application. DETAILED DESCRIPTION

[0027] The making and using of the preferred embodiments of the present application are discussed in detail below. It should be appreciated, however, that the present application provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the application and do not limit the scope of the application.

[0028] The present application regards three-way interference signals as spatial discrete points, replaces traditional ellipse fitting with translation and rotation projection to solve the fitting failure problem under weak signal; through strict synchronization of modulation signal and trigger signal, combined with intermittent acquisition (time length t 2), realizes multi-channel data time division multiplexing without crosstalk parallel processing effect.

[0029] A multi-channel microseismic signal demodulation method, comprising the following steps: S1: collecting three-way interference signals with fixed phase difference β to form discrete points P i ( x i , y i , z i ), the interference signal is represented as: ; Wherein, a 1、 a 2、 a 3 represent the direct current bias of the signal, b 1、 b 2、 b 3 represent the alternating current amplitude, is the phase change caused by vibration, β is the fixed phase difference.

[0030] S2: Adjust the amplitude of the modulation signal to control the phase difference β to be 0 and π respectively, collect the corresponding discrete points P i and fit the spatial straight lines L 1 and L 2; the parametric equation of the spatial straight line L 1 is: .

[0031] The parametric equation of the spatial straight line L 2 is: ; Wherein, i 1、 i 2、 i 3 are the coordinate corresponding to the direction vector of the straight line L 1.x 1、 y 1、 z 1 is the coordinate corresponding to any point on the straight line L 1; j 1、 j 2、 j 3 is the coordinate corresponding to any point on the straight line L 2; x 2、 y 2、 z 2 is the coordinate corresponding to any point on the straight line L 2; t is a real number parameter.

[0032] S3: calculate the intersection point L 0 of the straight lines L 1 and P 2, and the normal vector of the plane where the intersection point x 0 (x0, y0, z0) is located, construct a spatial straight line P 0 passing through the intersection point L 0 and perpendicular to the plane where the two straight lines are located; the spatial straight line L 0 is:

[0033] Meanwhile k 1, k 2, k 3 satisfy the following relationship: ; wherein x 0, y0, z0 are the coordinates corresponding to the intersection point P 0; k 1, k 2, k 3 are the direction vectors of the straight line L 0; i 1, i 2, i 3 are the coordinates corresponding to the direction vector of the straight line L 1; j 1, j 2, j 3 are the coordinates corresponding to the direction vector of the straight line L 2.

[0034] S4: calculate the angle between the straight line L 0 and the Z-axis or the Y-axis, and construct a rotation matrix with the X-axis as the rotation axis and the angle as the rotation angle R x ; this embodiment adopts the angle between the straight line L 0 and the Z-axis. The angle between the straight line L 0 and the Z-axis The sine and cosine of are: ; in, k 1. k 2. k 3 is a straight line L A direction vector of 0.

[0035] The rotation matrix R x Expressed as: ; in, For a straight line L The angle between 0 and the Z axis.

[0036] S5: Based on the intersection P 0 and the rotation matrix R x The collected discrete points P i Mapping into discrete points P j ( x j ,y j , z j ), and extract the orthogonal signal; the discrete points P i Mapping into discrete points P j ( x j ,y j , z j ) is: ; in, For a straight line L The angle between 0 and the Z axis; x 0, y0, z0 are the intersection points P The coordinate corresponding to 0; y j 、 z j For quadrature signals.

[0037] S6: Perform differential cross-multiplication operations on the orthogonal signals to demodulate the phase change caused by external vibration .

[0038] A multi-channel microseismic monitoring method based on optical fiber sensing includes step 1: outputting an intermittent symmetrical square wave modulation signal and an intermittent square wave trigger signal strictly synchronized with the modulation signal through a signal generating module, wherein the modulation signal controls a light source module to output lasers in three periodic phase states.

[0039] Step 2: The modulated laser is distributed to N sensing channels through a 1xN optical splitter.

[0040] Step 3: Each sensing channel converts the phase change caused by external vibration into three interference signals with a fixed phase difference through an interferometer β , and after being converted into three interference electric signals by a photoelectric conversion module, the data acquisition module is controlled by the trigger signal to synchronously acquire the three interference electric signals at the rising edge of each pulse and output to the signal processing module.

[0041] Step 4: The signal processing module processes the three interference electric signals acquired by the N sensing channels using the above multi-channel microseismic signal demodulation method, and demodulates the phase change caused by external vibration .

[0042] The sensing channel includes a circulator, an interferometer, and a photoelectric conversion module; the interferometer adopts a Michelson interferometer including a coupler, a mass block, an elastic body, and a Faraday rotating mirror; the time interval of the trigger signal for acquiring three interference electric signals per pulse is t 1, and the intermittent duration is t 2.

[0043] A multi-channel microseismic monitoring system based on optical fiber sensing includes a signal generation module for outputting an intermittent symmetric square wave modulation signal and an intermittent square wave trigger signal strictly synchronized therewith, the rising edge of each pulse of the trigger signal is synchronized with the level switching time of the modulation signal; a light source module for receiving the modulation signal and outputting phase-modulated laser; an optical splitter for splitting the laser output by the light source into N paths; N sensing channels for converting external vibration signals into three interference electric signals; a data acquisition module for receiving the trigger signal output by the signal processing module and synchronously acquiring three interference electric signals; and a signal processing module that processes the acquired multi-channel three interference electric signals using the above multi-channel microseismic monitoring method and demodulates the phase change .

[0044] The following will be further described in conjunction with the accompanying Figures 1-4 . The present application comprises a Michelson interferometer on an optical path through a 1x2 coupler and a Faraday rotating mirror, the sensing arm of the interferometer is wound on an elastic body, the reference arm is directly connected to the Faraday rotating mirror, so that the two arms have a certain arm length difference. When the interferometer senses external vibration, the optical path difference of the two arms will change, after being reflected by the Faraday rotating mirror and returning to the coupler, interference occurs and the vibration signal is modulated into the phase of the interference light.

[0045] In addition, the application utilizes a signal generation module to generate a phase modulation signal and a synchronous trigger acquisition signal of a specific waveform, and combines time division separation technology to acquire a set of three discrete signals with a fixed phase difference, and the voltage values of the three signals are taken as the coordinate values of a single point in space, so that they are distributed in a spatial rectangular coordinate system, and finally a pair of orthogonal signals are constructed after translation, rotation and projection, and the conventional DCM demodulation algorithm is used to realize high-precision demodulation of vibration information.

[0046] The three signals with a fixed phase difference β are represented as: ; Wherein, a 1, a 2, a 3 represent the direct current bias of the signal, b 1, b 2, b 3 represent the alternating current amplitude, is the phase change caused by vibration, β is the fixed phase difference. The value of the fixed phase difference β is adjusted by the amplitude of the modulation signal loaded to the light source.

[0047] The distribution of a series of discrete points P i ( x i , y i , z i ) in a spatial rectangular coordinate system acquired by the data acquisition module is shown in Figure 1 . Wherein, when the phase difference β =0 and β= π, the distribution of the discrete points P i ( x i , y i , z i ) in the spatial rectangular coordinate system is two intersecting straight lines, and when 0 β < π, the distribution of the discrete points P i ( x i , y i , z i ) in the spatial rectangular coordinate system presents different shapes and sizes of elliptical rings.

[0048] A multi-channel microseismic signal demodulation method, comprising the following steps: step 1: adjust the amplitude of the modulation signal to zero to control the phase difference β= 0, at this time, a series of discrete points are collected, and the direction vector of the straight line is obtained by using a spatial straight line fitting algorithm and any point on the straight line P 1( x 1, y 1, z 1) is represented by the parametric equation of the straight line as follows: ; wherein, i 1、 i 2、 i 3 are the coordinates corresponding to the direction vector of the straight line L 1; x 1、 y 1、 z 1 are the coordinates corresponding to any point on the straight line L 1; t is a real number parameter.

[0049] Step 2: Adjust the amplitude of the modulation signal to control the phase difference β = π, at this time, a series of discrete points are collected, and the direction vector of the straight line is obtained by using a spatial straight line fitting algorithm and any point on the straight line P 2( x 2, y 2, z 2) is represented by the parametric equation of the straight line as follows: ; wherein, j 1、 j 2、 j 3 are the coordinates corresponding to the direction vector of the straight line L 2; x 2、 y 2、 z 2 are the coordinates corresponding to any point on the straight line L 2; t is a real number parameter.

[0050] Step 3: The intersection point L 0( L 0, y0, z0) of the straight lines P 1 and x 2 can be calculated by simultaneously solving the equations of the two straight lines in Step 1 and Step 2, in addition, the normal vector of the plane on which the straight lines L 1 and L 2 lie can be calculated by the cross product, and the calculation formula is as follows:

[0051] wherein, i 1、i 2. i 3 is a straight line L The direction vector of 1 corresponds to the coordinate; j 1. j 2. j 3 is a straight line L 2 The direction vector corresponds to the coordinate.

[0052] therefore, Figure 1 The straight line constructed in L 1 and L 2 The planes are perpendicular and pass through the intersection P 0( x 0, y0, z0) L 0 is represented by: ; in, x 0, y0, z0 are the intersection points P The coordinate corresponding to 0; k 1. k 2. k 3 is a straight line L A direction vector of 0.

[0053] The straight line L Direction vector of 0 It can be expressed as: ; in, i 1. i 2. i 3 is a straight line L The direction vector of 1 corresponds to the coordinate; j 1. j 2. j 3 is a straight line L 2 The direction vector corresponds to the coordinate.

[0054] Step 4: In the rectangular coordinate system Z The direction vector of the coordinate axis can be expressed as (0, 0, 1), and the constructed straight line can be calculated according to the angle formula L 0 and Z Coordinate axis angle The sine and cosine of : ; in, k 1. k 2. k 3 is a straight line L A direction vector of 0.

[0055] Step 5: Construct a rotation matrix with the X axis as the rotation axis and the angle as the rotation angle Rx : ; wherein, is a straight line L 0 with the Z axis. After deriving the rotation matrix R x and the intersection point P 0( x 0, y0, z0), the amplitude of the modulation signal is set so that 0 < θ < π, at which time the distribution of the collected discrete points β P i ( x i , y i , z i ) in the rectangular coordinate system presents different shapes and sizes of elliptical ring.

[0056] Step 6: After translation and rotation, the collected discrete points P i ( x i , y i , z i ) can be obtained. One-to-one mapping discrete points P j ( x j , y j , z j ) are obtained after mapping the discrete points P i ( x i , y i , z i ) in the rectangular coordinate system. The distribution of the discrete points P j ( x j , y j , z j ) obtained after mapping is shown in Figure 2 , and the mapping relationship is: ; wherein, is a straight line L 0 with the Z axis; x 0, y0, z0 are the coordinates corresponding to the intersection point P 0; y j , z j are orthogonal signals.

[0057] ​Step 7: The phase change caused by external vibration of the interferometer can be directly solved by using a conventional differential cross multiplication operation (DCM demodulation algorithm) : ; wherein, C 0 is a fixed coefficient.

[0058] The complete optical structure of the hardware system is shown in Fig. 3, and a multi-channel microseismic monitoring system based on optical fiber sensing includes a signal generation module for outputting a modulating signal of an intermittent symmetrical square wave and an intermittent square wave trigger signal strictly synchronized therewith, each pulse rising edge of the trigger signal is synchronized with the level switching moment of the modulating signal; an optical source module for receiving the modulating signal and outputting phase-modulated laser; an optical splitter for splitting the laser output by the optical source into N paths; N sensing channels for converting external vibration signals into three-path interference electric signals; a data acquisition module for receiving the trigger signal output by the signal processing module and synchronously acquiring the three-path interference electric signals; and a signal processing module for processing the acquired multi-channel three-path interference electric signals and demodulating the phase change .

[0059] The sensing channel includes a circulator, a coupler, an optical-electric conversion module, a mass block, an elastic body and a Faraday rotating mirror, and the coupler, the mass block, the elastic body and the Faraday rotating mirror constitute a Michelson interferometer; when the external vibration causes the Michelson interferometer of the sensing channel of the plurality of channels to change in phase, the sensitive optical fiber wound on the mass block and the elastic body can pick up the vibration signal.

[0060] The working process and principle of the whole hardware system are as follows: the signal generation module outputs a modulating signal of an intermittent symmetrical square wave and an intermittent square wave trigger signal strictly synchronized therewith, the modulating signal controls the optical source module to output laser of three periodic phase states, the laser is distributed to N sensing channels after passing through a 1×N optical splitter, the split laser is split into sensing light and reference light in turn after passing through the circulator and the coupler of each sensing channel, and is output to the Faraday rotating mirror through the sensing arm and the reference arm of the interferometer, respectively, and is returned to the coupler along the original route after being reflected by the Faraday rotating mirror, and the interference signal is formed in the coupler.

[0061] As Figure 4 shown in the timing diagram of the modulating signal and the trigger signal, the modulating signal of the intermittent symmetrical square wave can intermittently generate three kinds of level signals, and the voltage value can be adjusted within a certain range, the modulating signal can make the three-path interference signals output by the Michelson interferometer of each sensing channel produce three kinds of modulation phases of 0, β , β and βVoltage value of value modulated signal level V 0 decision, Figure 4 The trigger signal in the generation of the square wave signal is synchronized with the modulation signal intermittently, and the intermittent duration is t 2, the data acquisition module acquires the interference signal data at the rising edge of the trigger signal, and the time interval of continuously acquiring three points is t 1, and requires t 1<1us. Due to the strict matching of the modulation signal and the synchronous trigger signal, the above interference signal can output three-phase changes which are symmetrically changed and have a fixed phase difference β Interference signal.

[0062] The interference signal is converted into three interference electric signals by the photoelectric conversion module, and the trigger signal controls the data acquisition module to synchronously acquire the three interference electric signals at the rising edge of each pulse and output to the signal processing module; the signal processing module processes the three interference electric signals collected by N sensing channels by using the above multi-channel microseismic signal demodulation method, and demodulates the phase change caused by external vibration .

[0063] The specific execution process of the present application is as follows: S1: system power on, waiting for the light source module to start and output power stable laser signal, the waiting time is 10 seconds.

[0064] S2: set the signal generation module to output the modulation signal and the trigger signal, set the level change time interval t 1=0.25us, the intermittent time interval t 2=20us.

[0065] S3: set the voltage value V 0 of the signal generation module output modulation signal, that is, the β =0 at this time. Under the condition that the interferometer is subjected to external excitation, the trigger data acquisition module acquires 1000 groups of discrete points P i ( x i , y i , z i ) In the space rectangular coordinate system, the space straight line fitting algorithm is executed, and the direction vector of the straight line And any point on the straight line P 1( x 1, y 1, z 1) is calculated.

[0066] S4: gradually adjust the voltage value V 0 of the signal generation module output modulation signal, so that the phase β= π, under the condition that the interferometer is subjected to external excitation, triggering the data acquisition module to collect 1000 groups of discrete points P i ( x i , y i , z i ). In the spatial rectangular coordinate system, the spatial straight line fitting algorithm is executed, and the direction vector of the straight line and any point on the straight line P 2( x 2, y 2, z 2) are calculated.

[0067] S5: the equations of the straight line L 1 and the straight line L 2 are solved simultaneously, and the intersection coordinates P 0( x 0, y0, z0) of the two straight lines are calculated and saved in the signal processing module.

[0068] S6: using the direction vectors of the straight line L 1 and the straight line L 2, the direction vector of the constructed straight line L 0 is calculated as , and the spatial straight line L 0 is:

[0069] Meanwhile k 1, k 2, k 3 satisfy the following relationship: ; Wherein, x 0, y0, z0 are the coordinates corresponding to the intersection P 0; k 1, k 2, k 3 are the direction vectors of the straight line L 0; i 1, i 2, i 3 are the direction vector coordinates of the straight line L 1; j 1, j 2, j 3 are the direction vector coordinates of the straight line L 2.

[0070] S7: the angle between the straight line L 0 and the Z-axis or the Y-axis is calculated, and a rotation matrix Rx ; This embodiment uses a straight line L 0 and the Z axis. L The angle between 0 and the Z axis The sine and cosine of are: ; in, k 1. k 2. k 3 is a straight line L A direction vector of 0.

[0071] The rotation matrix R x Expressed as: ; in, For a straight line L The angle between 0 and Z axis is stored in the signal processing module.

[0072] S8: Adjust the voltage value of the modulation signal output by the signal generation module V 0, so that the interference signal 0 < β <π, the signal acquisition modules of all channels collect discrete points in real time according to the trigger signal P i ( x i ,y i , z i ), combined with the above saved intersection coordinates P 0( x 0, y0, z0) and the rotation matrix R x Based on the intersection P 0 and the rotation matrix R x The collected discrete points P i Mapping into discrete points P j ( x j ,y j , z j ), and extract the orthogonal signal; the discrete points P i Mapping into discrete points P j ( x j ,y j , z j ) is: ; in, For a straight lineL 0 and the included angle of the Z axis; x 0, y0, z0 are intersection points P 0 corresponding coordinates; y j 、 z j is a quadrature signal.

[0073] S9: taking out the mapped discrete points P j ( x j , y j , z j ) Y and Z axis coordinate values, and using differential cross multiplication operation (DCM demodulation algorithm) to demodulate the phase change caused by external vibration from the above-mentioned quadrature signal y j 、 z j (discrete points P j Y and Z axis coordinate values), the expression of the differential cross multiplication operation (DCM demodulation algorithm) is: ; Wherein, C 0 is a fixed coefficient.

[0074] The present application regards three-way interference signals as spatial discrete points, replaces the traditional ellipse fitting by translation and rotation projection, solves the fitting failure problem under weak signal; through strict synchronization of the modulation signal and the trigger signal, combined with intermittent acquisition (time length t 2), realize the non-crosstalk parallel processing effect of time division multiplexing of multi-channel data. Through the spatial geometric demodulation model and the synchronous time-sharing multi-channel architecture, the present application solves the industry problems of weak signal demodulation failure, noise interference and high system complexity, and provides a high reliability solution for geological disaster warning.

[0075] Although the specification has been described in detail, it should be understood that various changes, substitutions and modifications can be made without departing from the spirit and scope of the present application as defined by the appended claims. In addition, the specific embodiments described are not intended to limit the scope of the present application, and those skilled in the art can easily understand based on the present application that the existing or later developed processes, machines, manufactures, compositions of matter, means, methods or steps can perform substantially the same function or obtain substantially the same result. Therefore, the appended claims are intended to include such processes, machines, manufactures, compositions of matter, means, methods or steps within their scope.

Claims

1. A multi-channel microseismic signal demodulation method, characterized by: The following steps are involved: S1: Three acquisition channels with fixed phase difference β The interference signal is composed of discrete points P i ( x i ,y i , z i ); S2: Control the phase difference by adjusting the amplitude of the modulation signal β 0 and π respectively, collecting the corresponding discrete points P i And fit a spatial straight line L 1 and L 2; S3: Calculate straight line L 1 and L The intersection of 2 P 0( x 0, y0, z0) and the normal vector of the plane where it is located, construct the intersection point P 0 and a straight line in space perpendicular to the plane where the two straight lines lie L 0; S4: Calculate straight line L The angle between 0 and the Z axis or Y axis is used to construct a rotation matrix with the X axis as the rotation axis and the angle as the rotation angle. R x ; S5: Based on the intersection P 0 and the rotation matrix R x The collected discrete points P i Mapping into discrete points P j ( x j ,y j , z j ), and extract the orthogonal signal; S6: Perform differential cross-multiplication operations on the orthogonal signals to demodulate the phase change caused by external vibration .

2. The multi-channel microseismic signal demodulation method according to claim 1, characterized in that: The interference signal in S1 is expressed as: in, a 1. a 2. a 3 represents the DC bias of the signal, b 1. b 2. b 3 represents the AC amplitude, is the phase change caused by vibration, β is a fixed phase difference.

3. The multi-channel microseismic signal demodulation method according to claim 1, characterized in that: The spatial straight line in S2 L The parametric equation of 1 is: ； The spatial straight line L The parametric equation for 2 is: in, i 1. i 2. i 3 is a straight line L The direction vector of 1 corresponds to the coordinate; x 1. y 1. z 1 is a straight line L The coordinates of any point on 1; j 1. j 2. j 3 is a straight line L 2's direction vector corresponds to the coordinate; x 2. y 2. z 2 is a straight line L The coordinates of any point on 2; t is a real number parameter.

4. The multi-channel microseismic signal demodulation method according to claim 1, characterized in that: The spatial straight line of S3 L 0 is: at the same time k 1. k 2. k 3 satisfies the following relationship: in, x 0, y0, z0 are the intersection points P The coordinate corresponding to 0; k 1. k 2. k 3 is a straight line L 0 direction vector; i 1. i 2. i 3 is a straight line L The direction vector of 1 corresponds to the coordinate; j 1. j 2. j 3 is a straight line L 2 The direction vector corresponds to the coordinate.

5. The multi-channel microseismic signal demodulation method according to claim 4, characterized in that: The straight line L The angle between 0 and the Z axis The sine and cosine of are: in, k 1. k 2. k 3 is a straight line L A direction vector of 0.

6. The multi-channel microseismic signal demodulation method according to claim 1, characterized in that: The rotation matrix R x Expressed as: in, For a straight line L The angle between 0 and the Z axis.

7. The multi-channel microseismic signal demodulation method according to claim 1, characterized in that: The discrete points P i Mapping into discrete points P j ( x j ,y j , z j ) is: in, For a straight line L The angle between 0 and the Z axis; x 0, y0, z0 are the intersection points P The coordinate corresponding to 0; y j 、 z j For quadrature signals.

8. A multi-channel microseismic monitoring method based on optical fiber sensing, characterized by: Step 1: The signal generating module outputs an intermittent symmetrical square wave modulation signal and an intermittent square wave trigger signal that is strictly synchronized with the modulation signal. The modulation signal controls the light source module to output lasers in three periodic phase states. Step 2: Distribute the modulated laser light to N sensing channels through a 1×N optical splitter; Step 3: Each sensing channel converts the phase change caused by external vibration into three phase differences through an interferometer β The interference signal is converted into three-way interference electrical signals by the photoelectric conversion module, and the trigger signal is used to control the data acquisition module to synchronously collect the three-way interference electrical signals at the rising edge of each pulse and output them to the signal processing module; Step 4: The signal processing module processes the three-way interference electrical signal collected by the N sensing channels using the multi-channel microseismic signal demodulation method according to any one of claims 1 to 7, and demodulates the phase change caused by the external vibration. .

9. The multi-channel microseismic monitoring method based on optical fiber sensing according to claim 8, characterized in that: The sensing channel includes a circulator, an interferometer and a photoelectric conversion module; the interferometer adopts a Michelson interferometer including a coupler, a mass block, an elastic body and a Faraday rotator mirror; the time interval for each pulse of the trigger signal to collect three interference electrical signals is t 1. The interval duration is t 2.

10. A multi-channel microseismic monitoring system based on optical fiber sensing, characterized by: The system comprises a signal generating module for outputting an intermittent symmetrical square wave modulation signal and an intermittent square wave trigger signal that is strictly synchronized therewith, wherein each rising edge of the trigger signal pulse is synchronized with the level switching moment of the modulation signal; a light source module for receiving the modulation signal and outputting a phase-modulated laser beam; a beam splitter for splitting the laser beam outputted by the light source into N beams; and N sensing channels for converting an external vibration signal into a three-way interference electrical signal. A data acquisition module for receiving a trigger signal output by a signal processing module and synchronously acquiring three-way interference electrical signals; and a multi-channel microseismic monitoring method according to claim 8 for processing the acquired multi-channel three-way interference electrical signals and demodulating the phase change signal processing module.

Images